Polishing method and polishing apparatus
A polishing method can prevent scratches in a polished surface of a polishing object, caused by foreign matter adhering to a surface of a polishing member, thus preventing the attendant lowering of the yield even when the polishing object is large-sized. The polishing method includes: specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of the polishing member; and intensively cleaning the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
1. Field of the Invention
The present invention relates to a polishing method and a polishing apparatus for polishing optical components, machine components, ceramics, metals, etc., a program for carrying out the polishing method, and a storage medium storing the program, and more particularly to a polishing method and a polishing apparatus which are suitable for polishing a polishing object, such as a semiconductor wafer, into a flat mirror-like surface, a program for carrying out the polishing method, and a storage medium storing the program.
2. Description of the Related Art
With the recent progress toward higher integration of semiconductor devices, circuit interconnects are becoming finer and the sizes of devices integrated are becoming smaller. The manufacturing of such semiconductor devices necessitate a process of removing by polishing a film formed in a surface of a semiconductor wafer, thereby flattening the surface. There are various methods for performing such a wafer flattening process, among which is polishing by chemical mechanical polishing (CMP) apparatus. A chemical mechanical polishing apparatus includes a polishing member (polishing cloth, polishing pad, etc.) and a holder (top ring, polishing head, chucks, etc.) for holding a polishing object, such as a semiconductor water. During polishing of a polishing object, a surface (to be polished) of the polishing object is pressed against a surface of the polishing member while moving them relative to each other, and a polishing aid (abrasive liquid, chemical, slurry, pure water, etc.) is supplied therebetween, thereby polishing the surface of the polishing object into a flat mirror-like surface. Polishing by a chemical mechanical polishing apparatus is known to perform good polishing by the combination of chemical polishing action and mechanical polishing action.
A foamed resin or a non-woven fabric is generally used as a material for a polishing member for use in a chemical mechanical polishing apparatus. Such a polishing member has fine surface irregularities, which act as chip pockets effective for prevention of clogging and a reduction in polishing resistance. The fine surface irregularities, however, smooth down during continued polishing of a polishing object with the polishing member, causing a decrease in the polishing rate. It is therefore necessary to carry out dressing of the surface of the polishing member, for example, by using a diamond dresser with a large number of diamond particles electrodeposited on its surface, to re-create fine irregularities in the surface of the polishing member.
During the dressing, the diamond particles can fall from the dresser and dressing debris can be produced. The diamond particles, which have fallen from the dresser, and the dressing debris are usually removed from the surface of the polishing member by a cleaning liquid which is supplied upon dressing. If, however, some of them are not removed and remain on the surface of the polishing member, they may form foreign matter and the foreign matter can cause a scratch or scratches in a surface (polished surface) of a polishing object after polishing.
Besides such diamond particles and dressing debris produced during dressing, debris of a film and debris of the polishing member, produced upon polishing of a film, such as an oxide film or a metal film, abrasive grains contained in a polishing aid, etc. can agglomerate into foreign matter and adhere to the surface of the polishing member, and such foreign matter can also cause a scratch or scratches in the polished surface of the polishing object. When the polishing object is a semiconductor wafer, such scratches are highly likely to be fetal defects, causing serious problems. Further, if polishing is continued with the polishing member with foreign matter adhering to the surface, production of scratches will continue not only on one polishing object but on a plurality of polishing objects until the foreign matter is removed from the surface of the polishing member, resulting in a lowering of the yield.
As described above, scratches formed in the surface of a polishing object are likely to be fetal detects. For the purpose of preventing scratches, various methods and apparatuses have been proposed to remove foreign matter adhering to a surface of a polishing member. For example, a method has been proposed in which a cleaning liquid, such as pure water or a liquid chemical, is blown onto a polishing member to clean off foreign matter from the polishing member, and a polishing apparatus incorporating an apparatus for carrying out the method has also been proposed (see Japanese Patent Laid-Open Publication Nos. H10-94964, H10-244458, H10-296625, H11-243072, H11-333695, 2000-218517, 2000-280163, 2000-340531 and 2001-144055). A method has been proposed in which foreign matter is removed from a surface of a polishing member by blowing a cleaning liquid onto the polishing member while rubbing the surface of the polishing member with a brush, a grindstone, a PVA sponge, or the like, and a polishing apparatus provided with an apparatus for carrying out the method has also been proposed (see Japanese Patent Laid-Open Publication Nos. H10-244458, H10-296625, H11-333695, 2000-218517 and 2000-280163). A polishing apparatus has been proposed in which an apparatus for sucking in a slurry is provided so that a slurry, which is a cause of foreign matter, is removed by suction from a surface of a polishing member (see Japanese Patent Laid-Open Publication No. H10-94964). A polishing apparatus has been proposed which is provided with a fluid bath for cleaning a polishing member during polishing (see Japanese Patent Laid-Open Publication No. H10-296625). A method has also been proposed which involves dissolving foreign matter with a solvent, such as peroxosulfuric acid or hydrofluoric acid, and a polishing apparatus provided with an apparatus for carrying out the method has also been proposed (see Japanese Patent Laid-Open Publication Nos. H10-217104 and 2000-280163).
Further, a scratch analysis method and a scratch analysis apparatus have been proposed which, in order to improve polishing conditions which will cause scratches or improve a polishing apparatus itself, analyze scratches formed in a surface (polished surface) of a polishing object after polishing and specify a polishing apparatus and its polishing conditions which have caused scratches, and specify the position of foreign matter adhering to a polishing member (see Japanese Patent Laid-Open Publication No. 2004-259871).
SUMMARY OF THE INVENTIONIt is, however, difficult to completely remove foreign matter adhering to a polishing member so as to fully prevent scratches producing in a surface (polished surface) of a polishing object after polishing. This is partly because, with the trend toward larger-sized polishing objects, an area of a polishing member for contact with a surface (to be polished) of a polishing object becomes larger, whereby blowing of a cleaning liquid onto the polishing member, rubbing of the polishing member with a brush, etc. are likely to be uneven, making effective removal of foreign matter from the polishing member difficult. On the other hand, uniform cleaning of a surface of a polishing member, if possible, may result in a failure in intensively cleaning a foreign matter adhesion portion of the polishing member, leading to insufficient removal of foreign matter from the polishing member.
The scratch analysis method and the scratch analysis apparatus, disclosed in Japanese Patent Laid-Open Publication No. 2004-259871, are not cooperative with a polishing apparatus. The analysis method and apparatus are therefore considered not to be capable of promptly dealing with the occurrence of scratches in a surface of a polishing object in a polishing apparatus operating in a mass production line. Prevention of the lowering of the yield will thus not be possible.
The present invention has been made in view of the above situation in the related art. It is therefore an object of the present invention to provide a polishing method and a polishing apparatus which can prevent scratches in a polished surface of a polishing object, caused by foreign matter adhering to a surface of a polishing member, thus preventing the attendant lowering of the yield even when the polishing object is large-sized, an adhesion region specifying method and an adhesion region specifying apparatus for specifying a foreign matter adhesion region, a program for carrying out the polishing method and a program for carrying out the adhesion region specifying method, and storage media storing the programs.
In order to achieve the above object, the present invention provides a polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of the polishing member; and intensively cleaning the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
By intensively cleaning a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member, for example, after stopping polishing, foreign matter can be effectively removed from the surface of the polishing member.
The present invention also provides another polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising: reading information on an intensive cleaning position or an intensive cleaning area in a surface of the polishing member from a storage medium in a computer; and intensively cleaning the intensive cleaning position or the intensive cleaning area in the surface of the polishing member.
By storing information on an intensive cleaning position or an intensive cleaning area, which is a position or area of high frequency of adhesion of foreign matter or a position or area which is especially important to the polishing yield, adhesion of foreign matter to a surface of a polishing member, which would cause scratches on a polishing object, can be prevented.
The present invention also provides still another polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising: reading information on an intensive cleaning position or an intensive cleaning area in a surface of the polishing member from a storage medium in a computer; specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; and intensively cleaning at least one of the intensive cleaning position or the intensive cleaning area in the surface of the polishing member and the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
When foreign matter is not detected on a surface of a polishing member, e.g., during polishing and thus a foreign matter adhesion position or a foreign matter-adhesion area is not specified in the surface of the polishing member, an intensive cleaning position or an intensive cleaning area will be intensively cleaned. When foreign matter is detected on the surface of the polishing member, the foreign matter adhesion position or the foreign matter adhesion area will be intensively cleaned. Adhesion of foreign matter to the surface of the polishing member can thus be effectively prevented, and removal of foreign matter adhering to the surface can be performed effectively. It is also possible to intensively clean a wider area, including a foreign matter adhesion position or a foreign matter adhesion area.
The present invention also provides still another polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising: specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of the polishing member; storing foreign matter adhesion positions or foreign matter adhesion areas in the surface of the polishing member; calculating an intensive cleaning position or an intensive cleaning area in the surface of the polishing member from the stored foreign matter adhesion positions or foreign matter adhesion areas; and intensively cleaning at one of the calculated intensive cleaning position or foreign matter adhesion area in the surface of the polishing member and the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member.
This makes it possible to calculate, from stored data on foreign matter adhesion positions or foreign matter adhesion areas in a surface of a polishing member, a position or area, which is of high frequency of adhesion of foreign matter, in the surface of the polishing member and to store the calculated position or area as an intensive cleaning position or an intensive cleaning area in a storage medium. The longer the polishing time is, the more is the amount of stored information on foreign matter adhesion positions or foreign matter adhesion areas in the surface of a polishing member, and thus the higher is the accuracy of intensive cleaning position or intensive cleaning area. Accordingly, an operation for removal of foreign matter from a surface of a polishing member can be performed more effectively, and cleaning for prevention of adhesion of foreign matter to the surface of the polishing member can be performed more effectively.
Preferably, adhesion of foreign matter to the surface of the polishing member is detected by a detection section to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
By detecting adhesion of foreign matter to a surface of a polishing member by the detection section, polishing can be stopped immediately after detection of the foreign matter. After stopping polishing, the surface of the polishing member may be cleaned to remove the foreign matter, or the polishing member may be replaced with a new one, thereby preventing scratches in a polished surface of a polishing object. Especially by detecting foreign matter on the surface of the polishing member by a contact method, foreign matter on the surface of the polishing member can be detection with high precision even when a liquid film or the like is present on the surface of the polishing member.
The detection of adhesion of foreign matter to the surface of the polishing member may be performed by image analysis of the surface.
According to this method, there is no fear of contamination of the polishing member by the detection section.
The polished surface of the polishing object after polishing may be evaluated to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
There is a correlation between a scratch formed in a surface (polished surface) of a polishing object after polishing and a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member. Accordingly, by evaluating the surface of the polishing object after polishing and detecting a scratch formed in the surface, a foreign matter adhesion position or a foreign matter adhesion area can be specified from the position of the scratch. Therefore, by intensively cleaning the foreign matter adhesion position or the foreign matter adhesion area, foreign matter can be removed effectively.
The evaluation of the polished surface of the polishing object after polishing can be performed by image analysis of the polished surface.
For example, a check is made as to whether scratches in a surface (polished surface) of a polishing object after polishing, caused by foreign matter, are fetal defects or not, and only scratches that are fetal detects are extracted. The extracted scratches can specify those foreign matter adhesion positions or foreign matter adhesion areas in a surface of a polishing member which will cause fetal scratches. Polishing may be stopped immediately after detection of the fetal scratches and intensive cleaning may be carried out on the specified foreign matter adhesion positions or foreign matter adhesion areas in the surface of the polishing member. This can prevent the lowering of the yield.
The present invention also provides a method for specifying a cleaning region in a surface of a polishing member, comprising: evaluating the surface of the polishing member to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member as a position or area to be intensively cleaned; and storing the specified intensive cleaning position or intensive cleaning area.
The present invention also provides another method for specifying a cleaning region in a surface of a polishing member, comprising polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, and evaluating a polished surface of the polishing object to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member as a position or area to be intensively cleaned.
Preferably, information on the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member is stored.
The evaluation of the polished surface of the polishing object may be performed by image analysis of the polished surface.
By thus storing the information on the specified position or area, the stored information can be utilized for calculation of an intensive cleaning position or an intensive cleaning area.
The present invention also provides a method for specifying a foreign matter adhesion region, comprising specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member by image analysis of a shot image of a polished surface of a polishing object.
For example, when scratches are formed in a polished surface of a polishing object, a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member can be specified by image analysis of a shot image of the polished surface, enabling efficient removal of foreign matter from the surface of the polishing member.
The present invention also provides a polishing apparatus for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising: an adhesion region specifying section for specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of the polishing member; and a cleaning section for intensively cleaning the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member, specified by the adhesion region specifying section.
By intensively cleaning a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member, for example, after stopping polishing, foreign matter can be effectively removed from the surface of the polishing member.
The present invention also provides another polishing apparatus for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising: a cleaning section for cleaning a surface of the polishing member; and a control section for reading information from a storage medium storing information on an intensive cleaning position or an intensive cleaning area in the surface of the cleaning member, and so controlling the cleaning section as to intensively clean the intensive cleaning position or the intensive cleaning area in the surface of the polishing member.
This can prevent foreign matter from adhering to the surface of the polishing member that would cause scratches.
The present invention also provides still another polishing apparatus for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising: a cleaning section for cleaning a surface of the polishing member; an adhesion region specifying section for specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; and a control section for reading information from a storage medium storing information on an intensive cleaning position or an intensive cleaning area in the surface of the cleaning member, and so controlling the cleaning section as to intensively clean at least one of the read intensive cleaning position or intensive cleaning area in the surface of the polishing member and the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member, specified by the adhesion region specifying section.
When foreign matter is not detected on a surface of a polishing member, e.g., during polishing and thus a foreign matter adhesion position or a foreign matter adhesion area is not specified in a surface of a polishing member, an intensive cleaning position or an intensive cleaning area will be intensively cleaned. When foreign matter is detected on the surface of the polishing member, the foreign matter adhesion position or the foreign matter adhesion area will be intensively cleaned. Adhesion of foreign matter to the surface of the polishing member can thus be effectively prevented, and removal of foreign matter adhering to the surface can be performed effectively.
The present invention also provides still another polishing apparatus for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising: a cleaning section for cleaning a surface of the polishing member; an adhesion region specifying section for specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; and a control section for storing foreign mater adhesion positions or foreign matter adhesion areas in the surface of the polishing member, specified by the adhesion region specifying section, calculating an intensive cleaning position or an intensive cleaning area in the surface of the polishing member based on the stored foreign matter adhesion positions or foreign matter adhesion areas, and so controlling the cleaning section as to intensively clean at least one of the calculated intensive cleaning position or intensive cleaning area in the surface of the polishing member and the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member, specified by the adhesion region specifying section.
This makes it possible to calculate, from stored data on foreign matter adhesion positions or foreign matter adhesion areas in a surface of a polishing member, a position or area, which is of high frequency of adhesion of foreign matter, in the surface of the polishing member and to store the position or area as an intensive cleaning position or an intensive cleaning area in a storage medium. The longer the polishing time is, the more is the amount of stored information on foreign matter adhesion positions or foreign matter adhesion areas in the surface of a polishing member, and thus the higher is the accuracy of the intensive cleaning position or intensive cleaning area. Accordingly, an operation for removal of foreign matter from a surface of a polishing member can be performed more effectively, and cleaning for prevention of adhesion of foreign matter to the surface of the polishing member can be performed more effectively. Data on a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, stored in the present polishing apparatus, or data on an intensive cleaning position or an intensive cleaning area in the surface of the polishing member, the latter data being calculated from the former data, can be used in another polishing apparatus. For example, in the case of installing a new polishing apparatus in addition to an existing polishing apparatus, data stored in the existing apparatus can be used in the new polishing apparatus, whereby adhesion of foreign matter to the same type of polishing member can be effectively prevented also in the new apparatus.
In a preferred aspect of the present invention, the adhesion region specifying section includes a detection section for detecting foreign matter adhering to the surface of the polishing member to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
This makes it possible to take action, such as stopping polishing, when the detection section has detected adhesion of foreign matter to a surface of a polishing member. Especially by providing the detection section in a polishing section, adhesion of foreign matter to a surface of a polishing member can be promptly detected. When a contact method is employed for detection of foreign matter on a surface of a polishing member, the detection can be performed with high precision even when there is a liquid film or the like on the surface of the polishing member.
The adhesion region specifying section may include an image analyzer for performing image analysis of the surface of the polishing member to detect foreign matter adhering to the surface.
This can prevent contamination of a polishing member, etc. by the detection section.
In a preferred aspect of the present invention, the adhesion region specifying section includes an evaluation device for evaluating the polished surface of the polishing object after polishing to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
There is a correlation between a scratch formed in a surface (polished surface) of a polishing object after polishing and a foreign matter adhesion position or a foreign matter adhesion area in the surface of a polishing member. Accordingly, by evaluating the surface of the polishing object after polishing and detecting a scratch formed in the surface, a foreign matter adhesion position or a foreign matter adhesion area can be specified from the position of the scratch. Therefore, by intensively cleaning the foreign matter adhesion position or the foreign matter adhesion area, foreign matter can be removed effectively.
The evaluation device is, for example, an image analyzer for analyzing an image of the polished surface of the polishing object after polishing to evaluate the surface.
For example, a check is made as to whether scratches in a surface (polished surface) of a polishing object after polishing, caused by foreign matter, are fetal defects or not, and only scratches that are fetal detects are extracted. The extracted scratches can specify those foreign matter adhesion positions or foreign matter adhesion areas in the surface of a polishing member which will cause fetal scratches. Polishing may be stopped immediately after detection of the fetal scratches and intensive cleaning may be carried out on the specified foreign matter adhesion positions or foreign matter adhesion areas in the surface of the polishing member. This can prevent the lowering of the yield.
In a preferred aspect of the present invention, the control section stores information on the foreign matter adhesion position or the foreign matter adhesion area specified by the adhesion region specifying section.
This makes it possible to utilize the stored information for calculation of an intensive cleaning position or an intensive cleaning area.
The present invention also provides an apparatus for specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, comprising; a reading device for reading standard patterns from a storage medium; a reading device for reading a shot image of a polished surface of a polishing object; an arithmetic unit for performing image analysis using the read standard patterns and the read image to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; and an output device for outputting the foreign matter adhesion position or the foreign matter adhesion area specified by the arithmetic unit.
When scratches are formed in a polished surface of a polishing object, a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member can be specified by image analysis using prepared standard patterns and a shot image of the polished surface of the polishing object. Therefore, an operation for removing foreign matter from the surface of the polishing member can be effectively performed. The reading device for reading standard patterns and the reading device for reading a shot image may, of course, comprise a common device having the both functions.
The present invention also provides another apparatus for specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, comprising: a reading device for reading geometric parameters of a polishing apparatus and polishing conditions for polishing a polishing object; a standard pattern production device for producing standard patterns using the read geometric parameters and the read polishing conditions; a reading device for reading a shot image of a polished surface of the polishing object; an arithmetic unit for performing image analysis using the produced standard patterns and the read image to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; and an output device for outputting the foreign matter adhesion position or the foreign matter adhesion area specified by the arithmetic unit.
According to this apparatus, standard patterns can be produced by using the read geometric parameters of a polishing apparatus and the read polishing conditions for polishing a polishing object. There is, therefore, no need to previously prepare standard patterns. Further, when scratches are formed in a polished surface of a polishing object, a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member can be specified by image analysis with the arithmetic unit using standard patterns, produced in the above-described manner, and a shot image of the polished surface of the polishing object, read by the image reading device. Accordingly, an operation for removal of foreign matter from the surface of the polishing member can be effectively performed. The reading device for reading geometric parameters of a polishing apparatus and the reading device for reading a shot image of a polished surface of a polishing object may, of course, comprise a common device having the both functions.
The present invention also provides a program for causing a computer to control an apparatus, for cleaning off foreign matter adhering to a surface of a polishing member, to perform operations of: an adhesion region specifying step of specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of the polishing member; an intensive cleaning conditions reading step of reading cleaning conditions for use in carrying out intensive cleaning on the surface of the polishing member; and an intensive cleaning step of intensively cleaning the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member under the read intensive cleaning conditions.
This program can cause a computer, for cleaning off foreign matter from a surface of a polishing member, to perform an adhesion region specifying step, an intensive cleaning conditions reading step, and an intensive cleaning step.
The present invention also provides another program for causing a computer to control an apparatus, for preventing adhesion of foreign matter to a surface of a polishing member, to perform operations of: an intensive cleaning region reading step of reading information on an intensive cleaning position or an intensive cleaning area in a surface of the polishing member from a storage medium; an intensive cleaning conditions reading step of reading cleaning conditions for use in carrying out intensive cleaning on a surface of the polishing member; and an intensive cleaning step of cleaning the read intensive cleaning position or intensive cleaning area in the surface of the polishing member under the read intensive cleaning conditions.
This program can cause a computer, for preventing adhesion of foreign matter to a surface of a polishing member, to perform an intensive cleaning region reading step, an intensive cleaning conditions reading step, and an intensive cleaning step.
The present invention also provides still another program for causing a computer to control an apparatus, for preventing adhesion of foreign matter to a surface of a polishing member or for cleaning off foreign matter adhering to the surface of the polishing member, to perform operations of: an intensive cleaning region reading step of reading information on an intensive cleaning position or an intensive cleaning area in the surface of the polishing member from a storage medium; an adhesion region specifying step of specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; an intensive cleaning conditions reading step of reading cleaning conditions for use in carrying out intensive cleaning on the surface of the polishing member; and an intensive cleaning step of cleaning at least one of the read intensive cleaning position or intensive cleaning area in the surface of the polishing member and the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member under the read intensive cleaning conditions.
This program can cause a computer, for preventing adhesion of foreign matter to a surface of a polishing member or for cleaning off foreign matter adhering to the surface of the polishing member, to perform an intensive cleaning region reading step, an adhesion region specifying step, an intensive cleaning conditions reading step, and an intensive cleaning step.
The present invention also provides still another program for causing a computer to control an apparatus, for preventing adhesion of foreign matter to a surface of a polishing member or for cleaning off foreign matter adhering to the surface of the polishing member, to perform operations of: an adhesion region specifying step of specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; an adhesion region storing step of storing foreign matter adhesion positions or foreign matter adhesion areas in the surface of the polishing member; an intensive cleaning region calculation step of calculating an intensive cleaning position or an intensive cleaning area in the surface of the polishing member from the stored foreign matter adhesion positions or foreign matter adhesion areas; an intensive cleaning conditions reading step of reading cleaning conditions for use in carrying out intensive cleaning on the surface of the polishing member; and an intensive cleaning step of cleaning at least one of the calculated intensive cleaning position or intensive cleaning area in the surface of the polishing member and the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member under the read intensive cleaning conditions.
This program can cause a computer, for preventing adhesion of foreign matter to a surface of a polishing member or for cleaning off foreign matter adhering to the surface of the polishing member, to perform an adhesion region specifying step, an adhesion region storing step, an intensive cleaning region calculation step, an intensive cleaning conditions reading step, and an intensive cleaning step.
The foreign matter adhesion position or the foreign matter adhesion area is specified in the adhesion region specifying step by, for example, detecting adhesion of foreign matter to the surface of the polishing member by a detection section.
This makes it possible to cause a computer to perform the adhesion region specifying step for detecting foreign matter on the surface of the polishing member with detecting section.
The adhesion region specifying step may include a step of performing image analysis of the surface of the polishing member to detect adhesion of the foreign matter to the surface.
This makes it possible to cause the computer to perform the adhesion region specifying step including a step of performing image analysis of the surface of the polishing member to detect adhesion of the foreign matter to the surface.
Alternatively, the foreign matter adhesion position or the foreign matter adhesion area may be specified in the adhesion region specifying step by evaluating a polished surface of a polishing object.
This makes it possible to cause the computer to perform the adhesion region specifying step for specifying the foreign matter adhesion position or the foreign matter adhesion area by evaluating a polished surface of a polishing object.
The adhesion region specifying step may include a step of performing image analysis of the polished surface of the polishing object after polishing to evaluate the polished surface.
This makes it possible to cause the computer to perform the adhesion region specifying step including a step of performing image analysis of the polished surface of the polishing object after polishing to evaluate the polished surface.
The present invention also provides still another program for causing a computer to control an apparatus, for storing foreign matter adhesion positions or foreign matter adhesion areas in a surface of a polishing member, to perform operations of: a step of evaluating the surface of the polishing member to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member as a position or an area to be intensively cleaned; and a step of storing the specified intensive cleaning position or intensive cleaning area.
This program can cause a computer to perform a step for storing a foreign matter adhesion position or a foreign matter adhesion area.
The present invention also provides still another program for causing a computer to control an apparatus, for specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, to perform operations of: polishing step of polishing a polishing object by applying pressure between the polishing member and the polishing object while moving the polishing member and the polishing object relative to each other; and an adhesion region specifying step of evaluating a polished surface of the polishing object to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member, which position or area is to be intensively cleaned.
This program can cause a computer to perform a step for specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member.
The program may be for also causing the computer to perform a step of storing data on the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member.
This makes it possible to cause the computer to perform a step of storing data on the specified foreign matter adhesion position or foreign matter adhesion area.
The adhesion region specifying step may include a step of performing image analysis of the polished surface of the polishing object to evaluate the polished surface.
This makes it possible to cause the computer to perform the adhesion region specifying step including a step of performing image analysis of the polished surface of the polishing object to evaluate the polished surface.
The present invention also provides still another program for causing a computer to control an apparatus, for specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, to perform an operation of: an adhesion region specifying step for specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member by image analysis of a shot image of a polished surface of a polishing object.
This makes it possible to cause a computer to perform an adhesion region specifying step for specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member.
The present invention also provides a computer readable storage medium storing the above-described program.
The present invention also provides still another polishing apparatus for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising a computer capable of reading the program from the above-described storage medium and executing the program.
By thus storing the program in a computer readable storage medium and reading the program from the storage medium for causing a computer to control an apparatus, a polishing apparatus, which can prevent the lowering of the yield due to scratches, can be provided.
The present invention also provides still another apparatus for specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, comprising a computer capable of reading the program from the above-described storage medium and executing the program.
By thus storing the program in a computer readable storage medium and reading the program from the storage medium for causing a computer to control an apparatus, an adhesion region specifying apparatus, which specifies a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, which would cause scratches, can be provided.
Preferred embodiments of the present invention will now be described with reference to the drawings.
At the outset, the terms “foreign matter adhesion position” and “foreign matter adhesion area”, in a surface of a polishing member, such as a polishing pad, to which foreign matter is adhering, will be described with reference to
The term “foreign matter adhesion position” refers to the exact position of adherent foreign matter in a surface of a polishing member. Thus, as shown in
The term “foreign matter adhesion area” refers to that area in a surface of a polishing member in which, when the polishing member is in a stationary state, foreign matter may possibly be adhering to the surface of the polishing member. Thus, in the case of the rotary polishing member 200, a foreign matter adhesion area may be represented, for example, by the circle with the radius R1, the center coinciding with the rotation center of the polishing member 200 (i.e., circumferential position θ not specified), or by an annular area with an inside diameter of R2 and an outside diameter of R3 (R2≠R3), as shown in
A description will now be given of an adhesion region specifying section which detects foreign matter on a surface of a polishing member to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member, which position or area is to be subjected to cleaning. An adhesion region specifying section, comprising a detection section for detecting foreign matter by a contact method, detects adhesion of foreign matter to a surface of a polishing member by bringing the detection section, e.g., comprised of a presser sensor or a displacement sensor, into contact with the surface of the polishing member, thereby specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member. The displacement sensor may be, for example, a commercially-available contact-type displacement sensor, or a displacement sensor comprised of a detection piece to be in contact with a polishing member, and a reading mechanism for reading a detected displacement. A commercially-available contact-type or non-contact-type displacement sensor can be used as the reading mechanism.
In order to thoroughly inspect the presence or absence of foreign matter in that area of the surface of the polishing member 200 to which adhesion of foreign matter must be avoided, the pressure sensors 204 are preferably disposed so that their adjacent annular trajectories partly overlap. The pressure sensors 204 should preferably be disposed so that their pressure detection faces fully cover, by rotation of the polishing member 200, at least that area of the surface of the polishing member 200 which may possibly come into contact with a polishing object 210, such as a semiconductor wafer, held, e.g., by a polishing head 208.
Since it suffices if the pressure sensors 204 are so disposed as to meet the above requirements, their arrangement is not limited to the arrangement along one radial direction shown in
As shown in
While the adhesion region specifying section 206 has been described in terms of its application to the rotary polishing member 200 shown in
A description will now be given of a method for detecting foreign matter F adhering to the surface of the polishing member 200 by the pressure sensors 204. Foreign matter F adhering to the surface of the polishing member 200 protrudes from the surface, as shown in
The foreign matter adhesion area in the polishing member 200 can be specified from the position of the particular pressure sensor 204, of the plurality of pressure sensors 204, which has detected the foreign matter F, or from the surface measuring range of the particular pressure sensor 204. Further, the foreign matter adhesion position can be specified by setting a reference coordinate system on the surface of the polishing member 200, and synchronizing the foreign matter detection time with the time history of the rotational or linear movement of the reference coordinate system, e.g., by the computer 212. A foreign matter adhesion position or a foreign matter adhesion area can be specified with high precision by using as the pressure sensor 204 a pressure distribution measuring device (tactile sensor) having a high spatial resolution.
As shown in
A description will now be given of an adhesion region specifying section 226 which employs, as a detection section, a plurality of displacement sensors 224 each including a detection piece 220 in contact with the polishing member 200, and a displacement reading mechanism 222 for reading a displacement of the detection piece 220, as shown in
The displacement sensors (detection section) 224, used in the adhesion region specifying section 226 shown in
A common contact-type or non-contact-type displacement sensor can be used as the displacement reading mechanism 222. The presence of foreign matter F on the polishing member 200 is first caught by a change in the position of the detection piece 220, the change is then detected by the displacement reading mechanism 222, using, e.g., a common non-contact-type displacement sensor, which generates a displacement signal, and the signal is recognized, e.g., by the computer 212.
Like the polishing object 210 being polished, the detection piece 220 is also polished and worn out though only gradually. Accordingly, a displacement of the detection piece 220, which is read by the displacement reading mechanism 222, changes with time even in the absence of foreign matter F. A means is therefore needed which will compensate for a change in the relative position between the displacement reading mechanism 222 and the detection piece 220 due to the wear of the detection piece 220. Such means include signal filtering, such as high-pass filtering or differential filtering, of the displacement signal of the displacement reading mechanism 222, a means for compensating for a change in the relative position by using a pre-measured wearing rate of the detection piece 220.
A material hard to be polished is preferably used for the detection piece 220. Examples of such materials include ceramics, such as zirconia, alumina, etc. and engineering plastics, such as an epoxy (EP) resin, a phenol (PF) resin, a polyphenylene sulfide (PPS) resin, etc.
While the displacement sensor 224, including the detection piece 220 and the displacement reading mechanism 222, has been described, a common contact-type displacement sensor may also be used.
The embodiment shown in
The detection piece 220 of each displacement sensor 224 is movably held, e.g., by the holder 228. Thus, while the holder 228 and the displacement reading mechanism 222 of the displacement sensor 224 are fixed at certain positions, only the detection piece 220 is movable. The polishing member 200 moves relative to such displacement sensors 224. That portion of the detection piece 220 of each displacement 224, which is in contact with the surface of the polishing member 200, will move relative to the surface of the polishing member 200 in an annular trajectory with a certain width. In order to thoroughly inspect the presence or absence of foreign matter in that area of the surface of the polishing member 200 to which adhesion of foreign matter must be avoided, the displacement sensors 224 are preferably disposed so that their adjacent annular trajectories partly overlap. The displacement sensors 224 should preferably be disposed so that the detection pieces 220 fully cover, by rotation of the polishing member 200, at least that area of the surface of the polishing member 200 which may possibly come into contact with the polishing object 210 held, e.g., by the polishing head 208.
Since it suffices if the displacement sensors 224 are so disposed as to meet the above requirements, their arrangement is not limited to the arrangement along one radial direction shown in
As shown in
While the adhesion region specifying section 226 has been described in terms of its application to the rotary polishing member 200 shown in
A description will now be given of a method for detecting foreign matter F adhering to the surface of the polishing member 200 by the displacement sensors 224. Foreign matter F adhering to the surface of the polishing member 200 protrudes from the surface, as shown in
The specification of a foreign matter adhesion position or a foreign matter adhesion area in a polishing member by the above-described adhesion region specifying sections, each including the contact-type foreign matter detection section, can be performed at any time when the polishing member is moving, such as before, during or after polishing of a polishing object, or during dressing of the polishing member. By carrying out the specifying operation during polishing, foreign matter can be detected immediately after its adhesion to the polishing member.
A description will now be given of an adhesion region specifying section which detects foreign matter on a surface of a polishing member by a non-contact-type detection section to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member, which position or area is to be subjected to cleaning. Such an adhesion region specifying section, having a non-contact-type foreign matter detection section, specifies a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member by detecting foreign matter on the surface of the polishing member without bringing into contact with the polishing member, such as by shooting the surface of the polishing member and analyzing a shot image of the surface.
An adhesion region specifying section, for example, including a photographic device, as a detection section, for shooting a surface of a polishing member, and an arithmetic unit for analyzing a shot image, will now be described first of its construction and then of its image analysis.
A photographic device (detection section) 230 may be set at a position, above a polishing member 200, at which shooting of the surface of the polishing member 200 is possible, as shown in
An adhesion region specifying section 234 includes the arithmetic unit 232 for making an image analysis of a shot image. An image shot by the photographic device 230 is transmitted, e.g., in the form of image data, through a wire 233 to the arithmetic unit 232 where the shot image is analyzed. A common computer, capable of executing image analysis by an image analysis software or an auxiliary image analysis circuit, a computer exclusively for image analysis, a digital image analysis circuit, an analog image analysis circuit, etc. can be used as the arithmetic unit 232. The arithmetic unit 232 may also have a control function for the photographic device 230.
In this embodiment, an image refers to an analog image, digital image data, or an analog electrical signal converted from an analog image or digital image data.
Image analysis by the adhesion region specifying section 234 will now be described. The polishing surface of the polishing member 200 is divided into an appropriate number of zones 236, and a shooting area 238 that includes a zone 236, preferably also includes an area surrounding the zone, is shot by the photographic device 230. All the zones 236 are thus shot sequentially. Image transformation of a shot image for image corrections and feature extraction on the transformed image are performed by the arithmetic unit 232. The image transformation may include spatial filtering for denoising, distortion correction, deblurring, sharpening, image enhancement, etc., spectral transformation, Walsh transform, wavelet transform, normalization, etc. The feature extraction may include edge extraction, line extraction, contour extraction, color extraction, density extraction, texture extraction, etc.
Thereafter, image recognition is performed by the arithmetic unit 232 to determine whether foreign matter is adhering to the surface of the polishing member 200 or not. The image recognition may include pattern recognition, such as the nearest neighbor method, Bayes decision rule, dynamic programming matching (DP matching), Hidden Markov Model, etc. In this embodiment, image analysis implies execution of at least one of image transformation, feature extraction and image recognition. Determination can be made by image analysis as to whether foreign matter is adhering to the surface of the polishing member 200 or not.
Though, in this embodiment, the surface of the polishing member 200 is divided into the zones 236 and the corresponding shooting areas 238 are shot sequential, it is also possible to shoot the entire polishing member 200 at once. The number of the zones 236 is not particularly limited. A position or area, in the surface of the polishing member 200, in which the presence of foreign matter F is determined by image recognition, can be specified as the foreign matter adhesion position or the foreign matter adhesion area. As with the above-described contact-type detection sections, it is also possible to set a reference coordinate system on the surface of the polishing member 200, and synchronize the time of detection of foreign matter with the time history of rotational or linear movement of the reference coordinate system by, e.g., a computer for controlling the polishing apparatus, thereby specifying the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member 200.
A CCD camera may be conveniently used as the photographic device 230. The use of a CCD camera enables the use of a digital arithmetic unit 232 for image analysis. It is, of course, possible to use an analog camera as the photographic device 230 and perform image analysis with a digital arithmetic unit 232 through A/D conversion of an image signal. This holds true for other photographic devices.
The arithmetic unit 232 may be either an arithmetic unit for exclusive use in the adhesion region specifying section 234 or a computer also used to control the polishing apparatus.
In a case where polishing is carried out using an opaque polishing aid, detection of foreign matter on the surface of the polishing member 200 by the adhesion region specifying section 234, which employs the above-described non-contact detection method, is preferably carried out when there is little polishing aid on the surface of the polishing member 200, such as during or after dressing of the polishing member 200.
Detection of foreign matter on the surface of the polishing member 200 by the adhesion region specifying section 234, which employs the above-described non-contact detection method, can be carried out irrespective of whether the polishing member 200 is moving or not. When the polishing member 200 is moving, the zones 236 are also moving. Shooting of the zones 236 is therefore carried out with timing synchronous with the movement of the polishing member 200. When the polishing member 200 is not moving, the entire zones 236 of the polishing surface are shot, e.g., by moving the photographic device 230. The entire polishing member 200 may be shot at once, as described above.
While the adhesion region specifying sections having a detection section have been described, an adhesion detection specifying section is not necessary provided with a detection section. For example, it is possible to carry out a simulation by using a computer to obtain information on a position or area of high probability of adhesion of foreign matter, and input the information into an adhesion region specifying section not having a detection section. It is also possible to use an adhesion region specifying section which itself has such a simulation function Furthermore, it is possible to use an adhesion region specifying section which stores information on foreign matter adhesion positions or foreign matter adhesion areas specified by the adhesion region specifying section, and specifies a foreign matter adhesion position or a foreign matter adhesion area based on the stored information. It is not necessary for such adhesion region specifying sections to carry out detection of foreign matter on a polishing member in use.
A description will now be given of an adhesion region specifying section which evaluates by image analysis of a surface (polished surface) of a polishing object after polishing. Such an adhesion region specifying section carries out shooting of a surface of a polishing object after polishing and image analysis of a shot image to detect a scratch or scratches in the surface, thereby indirectly specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member. An adhesion region specifying section which uses a photographic device, as a detection section, for shooting a surface (polished surface) of a polishing object after polishing, and includes an arithmetic unit (evaluation device or image analyzer) for analyzing a shot image, for example, will now be described first of its construction and then of its image analysis.
A photographic device (detection section) 250 may be set at a position at which shooting of a surface (polished surface) 210a of a polishing object 210, such as a semiconductor wafer, held on a holder 246 is possible, as shown in
The adhesion region specifying section 254 includes the arithmetic unit 252 for making an image analysis of a shot image. An image shot by the photographic device 250 is transmitted, e.g., in the form of image data, through a wire 253 to the arithmetic unit 252 where the shot image is analyzed. A common computer, capable of executing image analysis by an image analysis software or an auxiliary image analysis circuit, a computer exclusively for image analysis, a digital image analysis circuit, an analog image analysis circuit, etc. can be used as the arithmetic unit 252. The arithmetic unit 252 may also have a control function for the photographic device 250.
In this embodiment, an image refers to an analog image, digital image data, or an analog electrical signal converted from an analog image or digital image data.
Image analysis by the adhesion region specifying section 254 will now be described. The surface (polished surface) 210a of the polishing object 210 after polishing is divided into an appropriate number of zones 256, and a shooting area 258 that includes a zone 256, preferably also includes an area surrounding the zone 256, is shot by the photographic device 250. All the zones 256 are thus shot sequentially. Image transformation of a shot image for image corrections and feature extraction on the transformed image are performed by the arithmetic unit 252. The image transformation may include spatial filtering for denoising, distortion correction, deblurring, sharpening, image enhancement, etc., spectral transformation, Walsh transform, wavelet transform, normalization, etc. The feature extraction may include edge extraction, line extraction, contour extraction, color extraction, density extraction, texture extraction, etc.
Thereafter, image recognition is performed by the arithmetic unit (evaluation device or image analyzer) 252 to detect (extract) a scratch or scratches 210b formed in the surface 210a of the polishing object 210 after polishing. The presence of a scratch or scratches 210b in the surface 210a of the polishing object 210 after polishing indicates adhesion of foreign matter to a surface of a polishing member. The image recognition may include pattern recognition, such as the nearest neighbor method, Bayes decision rule, dynamic programming matching (DP matching), Hidden Markov Model, etc. In this embodiment, image analysis implies execution of at least one of image transformation, feature extraction and image recognition.
The use of the adhesion region specifying section 254 can indirectly detect adhesion of foreign matter to a surface of a polishing member. By determining a width, length, depth, etc. of a scratch with the arithmetic unit 252, the scratch can be checked to see if it is a fatal defect or not. When the scratch is a fetal defect, an appropriate action, such as immediately stopping polishing and cleaning the surface of the polishing member, can be taken. Polishing can be continued when the scratch is not a fetal defect. The lowering of the yield can therefore be prevented while minimizing the lowering of the throughput of polishing.
The arithmetic unit 252 may be either an arithmetic unit for exclusive use with the adhesion region specifying section 254 or a computer also used to control the polishing apparatus.
In the case where a polishing object is a semiconductor wafer, various wafer defect inspection apparatuses and foreign matter inspection apparatuses, which are commercially available from manufactures of semiconductor device inspection apparatuses, can be used for detection of scratches or for determination as to whether a scratch is a fetal defect or not. Such a commercially-available defect inspection apparatus, when used in combination with the adhesion region specifying section 254 to detect scratches 210b in the surface (polished surface) 210a of the polishing object 210, will contribute to maintaining the throughput at a high level.
A description will now be given of a method for specifying a foreign matter adhesion position or a foreign matter adhesion area in a polishing surface of a polishing member based on evaluation, by image analysis, of the surface (polished surface) 210a of the polishing object 210 after polishing. The foreign matter specifying method comprises shooting the surface (polished surface) 210a of the polishing object 210 after polishing, performing image analysis of a shot image, and specifying, from a scratch or scratches 210b in the surface 210a, a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member.
The detection of a scratch or scratches in the surface (polished surface) 210a of the polishing object 210 is carried out, for example, with the above-described adhesion region specifying section 254. The adhesion region specifying section 254 includes the arithmetic unit 252 for performing image analysis of a scratch or scratches detected by the photographic device (detection section) 250.
A method is known in which a foreign matter adhesion position or a foreign matter adhesion area in a polishing member is specified from a formulated scratch track, using the center of the circle of curvature and the radius of curvature at a point on a scratch and geometric parameters of the polishing apparatus, as described in Japanese Patent Laid-Open Publication No. 2004-259871. The geometric parameters of polishing apparatus are parameters which are determined by positional relationships between elements of the apparatus, such as the distance between the rotation center of a polishing member and the rotation center of a polishing object. An arithmetic unit, provided in an adhesion region specifying section, calculates by image analysis the center of the circle of curvature and the radius of curvature at a point on a scratch, and calculates and specifies a foreign matter adhesion position or a foreign matter adhesion area from the formulated scratch track.
This method can determine a foreign matter adhesion position or a foreign matter adhesion area in a polishing member with high precision. However, in some cases, for example, in the case where a polishing object swings on a polishing member, complicate calculations are required to formulate a scratch track and specify a foreign matter adhesion position or a foreign matter adhesion area from the formulated scratch track.
On the other hand, according to the below-described foreign matter region specifying method using the adhesion region specifying section 254 of this embodiment, a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member can be easily specified with high precision even when using a complicated polishing recipe. The method is therefore very useful.
First, patterns of scratches, as will be formed in a surface (polished surface) of a polishing object after polishing with a polishing member to which foreign matter is adhering, are calculated for a number of foreign matter adhesion positions or foreign matter adhesion areas by an arithmetic unit, and the calculated scratch patterns are stored as standard patterns in a storage device capable storing a program and/or data. Next, a scratch pattern (detection pattern) in the surface (polished surface) of the polishing object after polishing, actually detected by the adhesion region specifying section 254, is compared with the standard patterns by the arithmetic unit 252 and, from the degree of similarity, a foreign matter adhesion position or a foreign matter adhesion area in the polishing member is specified. The comparison by the arithmetic unit 252 includes image recognition.
A standard pattern may be produced experimentally or by a simulation. A standard pattern can be produced experimentally, for example, in the following manner: A polishing object is actually polished with a polishing member to which foreign matter or an equivalent of foreign matter is intentionally adhered. A scratch or scratches produced by polishing are detected by image analysis by the adhesion region specifying section 254. From the detected scratches, a desired pattern for use as a standard pattern is produced as computer-readable image data. In the case of employing image data as a standard pattern, the produced computer-readable data is converted into image data and the image data is used as a standard pattern.
A standard pattern can be produced by a simulation, for example, in the following manner: A track of foreign matter, adhering to a surface of a polishing member, on a surface (to be polished) of a polishing object is calculated using geometric parameters of a polishing apparatus, polishing conditions and a foreign matter adhesion position or a foreign matter adhesion area. From the track thus calculated, a desired pattern is produced as computer-readable data. In the case of employing image data as a standard pattern, the produced computer-readable data is converted into image data and the image data is used as a standard pattern.
A foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member can thus be specified by using image data on a scratch, detected by the photographic device 250, as a detection pattern, and comparing the detection pattern and standard patterns by image recognition using the arithmetic unit 252.
The geometric parameters of a polishing apparatus refer to parameters as determined by positional relationships between elements of the apparatus, such as the distance between the rotation center of a polishing member and the rotation center of a polishing object, and the polishing conditions refer to the rotational speed (moving speed) of a polishing member, the rotational speed of a polishing object, the swinging speed of the polishing object, the swinging range of the polishing object, etc. Polishing conditions are usually inputted as a polishing recipe into a polishing apparatus prior to polishing, and thus are known. Standard patterns, corresponding to foreign matter adhesion positions, can be produced easily from such a known polishing recipe even when the polishing conditions are complicated. It is therefore possible to carry out a simulation using an arithmetic device or a computer, provided in a polishing apparatus, after inputting a polishing recipe into the polishing apparatus, to thereby produce standard patterns.
Thus, even when a complicated polishing recipe is set, a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member can be specified with high precision. The present method specifies a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member by comparison of a detection pattern with standard patterns. Therefore, the precision can be enhanced by increasing the number of standard patterns according to necessity. The image recognition includes pattern recognition, such as the nearest neighbor method, Bayes decision rule, dynamic programming matching (DP matching), Hidden Markov Model, etc.
While the use of image data as a standard pattern has been described, it is also possible to use as a standard pattern various data obtainable from scratches, such as a radial density distribution and a circumferential density distribution of scratches, the presence or absence of a scratch at a specified position in a polished surface. In the case of using such standard patterns, a foreign matter adhesion position or a foreign matter adhesion area can be specified without carrying out image recognition.
For example, in the case of a circular polishing object, a foreign matter adhesion position or a foreign matter adhesion area in a polishing member can be specified by using, as a standard pattern, a radial or circumferential density distribution of scratches in the polished surface, as follows: From scratches detected by the photographic device 250, a radial or circumferential density distribution of the scratches in the polished surface is first calculated as a detection pattern using the arithmetic device 252. The arithmetic unit 252 then compares the detection pattern with the characteristics of distributions in standard patterns which have previously been calculated and stored as data, such as the periodicity of distribution of scratches, the peak position (position at which scratches are concentrated) of scratches, the peak height (concentration or density of scratches), etc., thereby specifying an adhesion position or an adhesion area in the polishing member.
If the detection pattern does not fully coincide with any of the standard patterns in terms of distribution characteristics, the arithmetic unit 252 may then pick out the most similar standard pattern and specify a position or an area in the polishing member, corresponding to the most similar standard pattern, as a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member. Alternatively, the arithmetic unit 252 may pick out some similar standard patterns, and specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member by determining the average or the maximal value in a distribution function of positions or areas, corresponding to the similar standard patterns. Thus, more than one foreign matter adhesion position or foreign matter adhesion area can be specified. This holds true for any other specifying method.
The arithmetic unit 252 may be either an arithmetic unit for exclusive use with the adhesion region specifying section 254 or a computer also used to control the polishing apparatus.
Located at a position accessible by the transport robot 24, there is provided an adhesion region specifying section 120 shown in
The transport robot 24 has upper and lower hands. The lower hand of the transport robot 24 is used only for receiving a semiconductor wafer from the wafer cassette 21. The upper hand of the transport robot 24 is used for transporting a semiconductor wafer in or from the adhesion region specifying section 120 and returning a semiconductor wafer to the wafer cassette 21. Since a clean semiconductor wafer, which has been cleaned, is held by the upper hand, the clean semiconductor wafer is not further contaminated. The lower hand is a vacuum attracting-type hand for holding a semiconductor wafer under vacuum, and the upper hand is a recess support-type hand for supporting a peripheral edge of a semiconductor wafer. The vacuum attracting-type hand can hold and transport a semiconductor wafer even if the semiconductor wafer is not located in a normal position. The recess support-type hand can transport a semiconductor wafer while keeping a lower surface of the semiconductor wafer clean because dust is not collected.
Two cleaning devices 25, 26 are disposed at an opposite side of the wafer cassettes 21 with respect to the rails 23 of the transport robot 24. The cleaning devices 25, 26 are disposed at positions accessible by the hands of the transport robot 24. Between the two cleaning devices 25, 26, a wafer station 70 having four semiconductor wafer supports 27, 28, 29 and 30 is disposed at a position accessible by the transport robot 24. Each of the cleaning devices 25, 26 has a spin-dry mechanism for drying a semiconductor wafer by spinning it at a high speed, and hence two-stage cleaning and three-stage cleaning of a semiconductor wafer can be performed without replacing any cleaning module.
An area B, in which the cleaning devices 25, 26 and the supports 27, 28, 29 and 30 are disposed, and an area A, in which the wafer cassettes 21, the adhesion region specifying section 120 and the transport robot 24 are disposed, are partitioned by a partition 84 so that the cleanliness of the area A and the area B can be separated. The partition 84 has an opening for allowing semiconductor wafers to pass therethrough, and a shutter 31 is provided at the opening of the partition 84. A transport robot 80, having two hands, is disposed at a position where the transport robot 80 can access the cleaning device 25 and the three supports 27, 29 and 30, and a transport robot 81, having two hands, is disposed at a position where the transport robot 81 can access the cleaning device 26 and the three supports 28, 29 and 30.
The support 27 is used to transfer a semiconductor wafer between the transport robot 24 and the transport robot 80, and has a sensor 91 for detecting existence of a semiconductor wafer. The support 28 is used to transfer a semiconductor wafer between the transport robot 24 and the transport robot 81, and has a sensor 92 for detecting existence of a semiconductor wafer. The support 29 is used to transport a semiconductor wafer from the transport robot 81 to the transport robot 80, and has a sensor 93 for detecting existence of a semiconductor wafer and a rinsing nozzle 95 for preventing a semiconductor wafer from being dried or rinsing a semiconductor wafer.
The support 30 is used to transport a semiconductor wafer from the transport robot 80 to the transport robot 81, and has a sensor 94 for detecting existence of a semiconductor wafer and a rinsing nozzle 96 for preventing a semiconductor wafer from being dried or rinsing a semiconductor wafer. The supports 29, 30 are disposed in a common water-scatter-prevention cover which has an opening defined therein for transporting wafers therethrough. At the opening, there is provided a shutter 97. The support 29 is disposed above the support 30. The upper support 29 serves to support a semiconductor wafer which has been cleaned, and the lower support 30 serves to support a semiconductor wafer to be cleaned. With this arrangement, the semiconductor wafer is prevented from being contaminated by rinsing liquid which would otherwise fall thereon. The sensors 91, 92, 93 and 94, the rinsing nozzles 95, 96, and the shutter 97 are schematically shown in
The respective upper hands of the transport robots 80, 81 are used for transporting a semiconductor wafer, that has been cleaned, to the cleaning devices 25, 26 or the supports of the wafer station 70. On the other hand, the respective lower hands of the transport robots 80, 81 are used for transporting a semiconductor wafer, that has not cleaned or a semiconductor wafer to be polished, to a reversing device. Since the lower hands are used to transport a semiconductor wafer to or from the reversing device, the upper hands are not contaminated by drops of rinsing liquid which fall from an upper wall of the reversing device. A cleaning device 82 is disposed at a position adjacent to the cleaning device 25 and accessible by the hands of the transport robot 80, and another cleaning device 83 is disposed at a position adjacent to the cleaning device 26 and accessible by the hands of the transport robot 81. All of the cleaning devices 25, 26, 82 and 83, the supports 27, 28, 29 and 30 of the wafer station 70, and the transport robots 80, 81 are placed in area B. Pressure in area B is adjusted so as to be lower than pressure in area A. Each of the cleaning devices 82, 83 is capable of cleaning both surfaces of a semiconductor wafer.
The chemical mechanical polishing apparatus has a housing 66 for enclosing various components therein. The interior of the housing 66 is partitioned into a plurality of compartments or chambers (including the areas A and B) by partitions 84, 85, 86, 87 and 67. A polishing chamber is separated from an area A by the partition 87, and the polishing chamber is divided into an area C as a first polishing section and an area D as a second polishing section. In each of the two areas C, D, there are provided two polishing tables, and a top ring for holding a semiconductor wafer and pressing the semiconductor wafer against the polishing tables for polishing. That is, polishing tables 54, 56 are provided in the area C, and polishing tables 55, 57 are provided in the area D. Further, a top ring 52 is provided in the area C, and a top ring 53 is provided in the area D.
The polishing tables 54, 55, 56, 57 are each provided at the top with a polishing pad 10 (see
The adhesion region specifying sections 110, 111, according to this embodiment, are each comprised of the adhesion region specifying section 226 having the displacement sensors 224, shown in
The adhesion region specifying sections 110, 111 can therefore detect adhesion of foreign matter to a polishing pad and specify a foreign matter adhesion area in the polishing pad even during polishing. The cleaning sections 112, 113 carry out cleaning of the polishing pad by rubbing the polishing pad with a rotating brush. The cleaning sections 112, 113 have a mechanism for moving the brush to an arbitrary radial position on the polishing pad. Thus, the brush of the cleaning section 112 or 113 can be fixed at an arbitrary position when the polishing table 54 or 55 is rotating, so that the area in the polishing pad, which makes contact with the fixed brush, can be cleaned intensively. Alternatively, the brush of the cleaning section 112 or 113 may be moved such that it swings between the center and the edge of the polishing pad so that the entire surface of the polishing pad can be cleaned.
By such an expression as “intensively clean” is herein meant (1) to clean a position or area for a longer time than the other position or area, (2) when rubbing a polishing member with a brush, a grindstone, a PVA sponge, or the like, to rub a position or area at a higher pressure than the other position or area, (3) when rubbing a polishing member with a rotating brush, grindstone, PVA sponge, or the like, to rub a position or area at a higher rotational speed than the other position or area, (4) when cleaning off foreign matter by blowing a cleaning liquid, such as pure water or a liquid chemical, onto a polishing member, to blow the cleaning liquid onto a position or area at a higher flow rate, a higher speed (higher pressure), a higher concentration and/or a high temperature than the other position or area, (5) when sucking in a slurry on a polishing member, to suck in the slurry on a position or area at a high suction than the other position or area, (6) when dissolving foreign matter on a polishing member with a solvent, such peroxosulfuric acid or hydrofluoric acid, to apply the solvent at a higher concentration or a higher temperature to a position or area than the other position or area, (7) when cleaning a polishing member by ultrasonic cleaning, to apply ultrasonic waves of higher power to a position or area than the other position or area, etc. This holds true for any other specifying method.
Wet-type wafer film thickness-measuring machines may be installed in place of the polishing tables 56, 57. In this case, it is possible to measure with the wafer film thickness-measuring machine a thickness of a surface film of a semiconductor wafer immediately after polishing, making it possible to additionally polish the surface film of the semiconductor wafer or to control the polishing process of the next semiconductor wafer by utilizing the measured film thickness value.
In order to transfer a semiconductor wafer between the polishing chamber and the area B, a rotary wafer station 98, having reversing machines 99, 100, 101, 102 for reversing a semiconductor wafer, is disposed at a position accessible by the transport robots 80, 81 and the top rings 52, 53. The reversing machines 99, 100, 101, 102 revolve by rotation of the rotary wafer station 98.
A semiconductor wafer is transferred between the polishing chamber and the area B in the following manner: Assuming that the reversing machines 99, 100, 101, 102, provided in the rotary wafer station 98, are disposed as shown in
A shutter 45, provided in the partition 87, opens when the transport robot 80 transports a semiconductor wafer to the rotary wafer station 98 so that the semiconductor wafer can be transferred between the area B and the polishing chamber. A shutter 46, provided in the partition 87, opens when the transport robot 81 transports a semiconductor wafer to the rotary wafer station 98 so that the semiconductor wafer can be transferred between the area B and the polishing chamber.
After transferring the semiconductor wafer to the reversing machine 99 and transferring the another semiconductor wafer to the reversing machine 100, the rotary wafer station 98 is rotated on its axis by 180 degrees to thereby move the reversing machine 99 to the area D side and move the reversing machine 100 to the area C side. The semiconductor wafer, which has been moved to the area C side by the rotation of the rotary wafer station 98, is reversed by the reversing machine 100 such that its upward surface to be polished (front surface) turns downward, and then transferred to the top ring 52. The semiconductor wafer, which has been moved to the area D side by the rotation of the rotary wafer station 98, is reversed by the reversing machine 99 such that its upward surface to be polished (front surface) turns to downward, and then transferred to the top ring 53.
The semiconductor wafers, which have been transferred to the top rings 52, 53, are attracted to the top rings 52, 53 by their vacuum attraction mechanisms. The semiconductor wafers, while kept attracted to the top rings 52, 53, are transported to the polishing tables 54, 55, and are polished with the polishing pads mounted on the polishing tables 54, 55.
As shown in
The pressure of the retainer ring 14 against the polishing pad 10 is adjusted by controlling the pressure in the air bag 6 by a pressure adjustment mechanism 108. It is also possible not to provide the airbag 6, and adjust the pressure of the support surface of the retainer ring 14 by controlling the load, applied from the shaft of the top ring 52, by the pressure adjustment mechanism 108. The air bag 5 may be comprised of either a single chamber, as illustrated in the Figure, or a plurality of concentric chambers.
The polishing table 54 comprises a polishing platen 9 and the polishing pad 10. The polishing pad 10 may be either a single-layer pad, as shown in
Returning to
The semiconductor wafers after completion of the polishing are transferred by the top rings 52, 53 to the reversing machines 99, 100, respectively. After reversing the semiconductor wafers with the reversing machines 99, 100 such that the front surfaces after polishing (polished surfaces) turn to upward, the rotary wafer station 98 is rotated by 180 degrees to thereby move the semiconductor wafers to the area B side of the rotary wafer station 98. One of the semiconductor wafers, which have been moved to the area B side, is transported by the transport robot 80 from the reversing machine 99 to either the cleaning machine 82 or the wafer station 70. The other semiconductor wafer is transported by the transport robot 81 from the reversing machine 100 to either the cleaning machine 83 or the wafer station 70. After carrying out appropriate cleaning of the semiconductor wafers, the surface (polished surface) of each semiconductor wafer is evaluated with the adhesion region specifying section 120 to determine the presence or absence of a scratch. Thereafter, the semiconductor wafers are placed into the wafer cassette 21.
After the completion of polishing with the polishing table 54 or 55, the polishing pad attached on top of the polishing table 54 or 55 is dressed with the dresser 58 or 59. During dressing, the abrasive liquid nozzle 60 or 61 supplies a cleaning liquid, such as pure water, to the polishing pad. The dressing effects cleaning, dressing, configuration correction, etc. of the surface of the polishing pad. When adhesion of foreign matter to the polishing pad is not detected by the adhesion region specifying section 110 or 111 and the adhesion region specifying section 120, an intensive cleaning area in the polishing pad is intensively cleaned, e.g., with a brush of the cleaning section 112 or 113 in parallel with the dressing. The intensive cleaning area is predetermined as an area to which foreign matter is likely to adhere, as will be described later. Accordingly, adhesion of foreign matter to the polishing pad can be prevented by intensively cleaning the intensive cleaning area of the polishing pad with the cleaning section 112 or 113. The adhesion region specifying section 110 or 111 performs detection of foreign matter to the polishing pad also during dressing. Therefore, adhesion of foreign matter to the polishing pad can be detected and the adhesion area can be specified also during dressing.
When foreign matter adhering to the polishing pad is detected by the adhesion region specifying section 110 or 111 during polishing or during dressing, an annular area in the surface of the polishing pad can be specified as the foreign matter adhesion area in the polishing pad. It is to be noted in this regard that the adhesion region specifying section 226 having the displacement sensors 224, shown in
There is a case where the adhesion region specifying sections 110, 111 detect, besides foreign matter adhering to the polishing pad, foreign matter moving on the polishing pad by a flow of a slurry or a cleaning liquid. Therefore, in order to more precisely detect adhesion of foreign matter to a polishing pad, the chemical mechanical polishing apparatus, shown in
A pattern or patterns, similar to the shot scratch pattern, are picked out by pattern recognition, and the foreign matter adhesion area (range of a radius or radii of the pad) is specified based on the similarity between the shot scratch pattern and the standard patterns picked out. There is no need to make pattern recognition when the absence of a scratch in the surface of the semiconductor wafer is determined by the adhesion region specifying section 120. In the case where the adhesion region specifying section 120 has detected adhesion of foreign matter to the polishing pad and specified the foreign matter adhesion area, the foreign matter adhesion area in the polishing pad is intensively cleaned with the cleaning section 112 or 113. This can effectively remove the foreign matter from the polishing pad.
When a foreign matter adhesion area in a polishing pad, specified by the adhesion region specifying section 110 or 111, overlaps with a foreign matter adhesion area in the polishing pad, specified by the adhesion region specifying section 120, the probability of adhesion of foreign matter to the polishing pad is high, and the foreign matter is present in the specified foreign matter adhesion area with high probability. In case foreign matter cannot be removed during a polishing process for one semiconductor wafer and the foreign matter is detected in a plurality of wafers in spite of intensive cleaning of the foreign matter adhesion area of the polishing pad, polishing with the polishing table having foreign matter may be stopped and the foreign matter adhesion area may be intensively cleaned with the cleaning section 112 or 113. The removal of the foreign matter from the polishing pad can be detected with the adhesion region specifying section 110 or 111.
The chemical mechanical polishing apparatus can store data on foreign matter adhesion areas, specified by the adhesion region specifying section 110 or 111 and the adhesion region specifying section 120, in a storage device installed in a control computer 130. An area in the polishing pad, to which foreign matter is likely to adhere, can be determined by calculation of an adhesion probability with the control computer 130 based on the stored data on specified foreign matter adhesion areas. By predetermining an area, to which foreign matter is likely to adhere, as an intensive cleaning area, and intensively cleaning the area, when there is no foreign matter in the area, with the cleaning section 112 or 113, adhesion of foreign matter to the polishing pad can be prevented effectively. In the chemical mechanical polishing apparatus, the entire process, including transport, polishing and cleaning of a semiconductor wafer, detection of adhesion of foreign matter to the polishing pad and specification of a foreign matter adhesion position or a foreign matter adhesion area, is controlled by the control computer 130.
A description will now be given of a method for calculating the probability of adhesion of foreign matter to the polishing pad 10 of the polishing table 54 based on stored data on foreign matter adhesion areas specified by the adhesion region specifying section 110. First, the polishing pad 10 of the polishing table 54 is divided to define 5 concentric annular zones 1 to 5, as shown in
If a zone or zones with an adhesion probability of not less than 30% are to be designated as an intensive cleaning area, then the zones 3 and 4 will be designated as an intensive cleaning area. When intensively cleaning the intensive cleaning area of the polishing pad 10 with the cleaning section 112, the polishing pad 10 is cleaned while swinging the brush of the cleaning 112 over the width of the zones 3 and 4. If a zone with the highest adhesion probability is to be designated as an intensive cleaning area, the zone 3 is the intensive cleaning area of the polishing pad 10. In this case, there is no need for the calculation of adhesion probability and the zone with the highest adhesion frequency can be designated as an intensive cleaning area. When intensively cleaning the intensive cleaning area (zone 3) of the polishing pad 10 with the cleaning section 112, the brush of the cleaning section 112 is allowed to swing over the width of the zone 3 during cleaning. In the case where the brush is large enough to clean the zone 3 of the polishing pad 10 without swinging, the brush may be kept at a fixed position during cleaning.
While the method for calculating the probability of adhesion of foreign matter to the polishing pad 10 of the polishing table 54, based on stored data on adhesion are as specified by the adhesion region specifying section 110, has been described, the same method applies to the case of calculating adhesion probability for the polishing pad of the polishing table 55 based on stored data on adhesion are as specified by the adhesion region specifying section 111. Also in the case of calculating adhesion probability based on an adhesion area specified by the adhesion region specifying section 120, the probability can be calculated in the same manner, i.e., by defining divisional annular zones in the surface of the polishing pad, storing adhesion frequencies in the zones in the storage device, and calculating the adhesion probabilities from the stored data.
Next, a description will now be given of a control flow in a process of polishing a semiconductor wafer as a polishing object with a polishing pad as a polishing member, using the chemical mechanical polishing apparatus shown in
The following information, for example, is stored in the storage device of the control computer 130:
A. Polishing Apparatus Control ProgramA-1. Main routine for polishing
A-2. Routine for determination of completion of preparations for polishing
A-3. Dressing routine
A-4. Polishing pad cleaning routine
A-5. Semiconductor wafer cleaning routine
A-6. Routine for monitoring foreign matter adhesion by evaluation of polishing pad
A-7. Routine for determination of foreign matter adhesion by evaluation of polished surface
A-8. Intensive cleaning area calculation routine
A-9. Semiconductor wafer transport routine
-
- etc.
B-1. Semiconductor wafer transport conditions
B-2. Polishing conditions (polishing recipe)
-
- B-2-1. Rotational speed of polishing pad
- B-2-2. Rotational speed of semiconductor wafer (top ring)
- B-2-3. Swinging speed of semiconductor wafer (top ring)
- B-2-4. Swinging range of semiconductor wafer (top ring)
- B-2-5. Polishing time
- B-2-6. Polishing pressure
- B-2-7. Flow rate of slurry supplied
B-3. Dressing conditions
-
- B-3-1. Rotational speed of polishing pad
- B-3-2. Rotational speed of dresser
- B-3-3. Swinging speed of dresser
- B-3-4. Swinging range of dresser
- B-3-5. Dressing time
- B-3-6. Dressing pressure
- B-3-7. Flow rate of cleaning liquid supplied
B-4. Semiconductor wafer cleaning conditions
B-5. Polishing pad cleaning conditions
-
- B-5-1. Normal cleaning conditions
- B-5-1-1. Rotational speed of brush
- B-5-1-2. Swinging speed of brush
- B-5-1-3. Swinging range of brush
- B-5-1-4. Pressure of brush
- B-5-1-5. Cleaning time
- B-5-2. Intensive cleaning conditions
- B-5-2-1. Rotational speed of brush
- B-5-2-2. Pressure of brush
- B-5-2-3. Cleaning time
- B-5-1. Normal cleaning conditions
B-6. Geometric parameters
-
- B-6-1. Diameter of semiconductor wafer
- B-6-2. Coordinates of rotation center of polishing pad
- B-6-3. Coordinates of rotation center of top ring
- B-6-4. Coordinates of pivot center of top ring
- B-6-5. Radius of pivoting of top ring
B-7. Intensive cleaning area
etc.
C. Information on Foreign Matter Adhesion
-
- C-1. Polishing pad zones
- C-2. Standard patterns for image recognition
- C-3. Foreign matter adhesion region
- C-4. Intensive cleaning area etc.
Polishing by the polishing apparatus is started when the control computer 130 retrieves a polishing apparatus control program from the storage device, and polishing proceeds, e.g., in accordance with the main routine for polishing shown in
After reading the various conditions from the storage device, the control computer 130 produces, based on the read various conditions, standard patterns for image recognition, which are to be used in specification of a foreign matter adhesion area, by evaluation of the polished surface of a polishing object with the adhesion region specifying section 120. The standard patterns to be produced may be, for example, data on a radial density distribution or a circumferential density distribution of scratches, or data on the presence or absence of a scratch at a specified position on a polished surface, analyzed from data on a track of foreign matter as shown in
Next, the control computer 130 so controls the polishing apparatus that a semiconductor wafer is taken by the transport robot 24 out of the wafer cassette 21 and transported to the support 28. After the semiconductor wafer is transported to the support 28, the control computer 130 so controls the transport robot 81, etc. as to transport the semiconductor wafer to the reversing device 100 provided in the rotary wafer station 98.
After the semiconductor wafer is transported to the reversing device 100, the control computer 130 executes the routine for determination of the completion of preparations for polishing, shown in
Next, the control computer 130 so controls the polishing apparatus as to rotate the rotary wafer station 98 and reverse the semiconductor wafer with the reversing device 100 and, after transporting the semiconductor wafer to the top ring 52, transport it to the polishing table 54. After the semiconductor wafer is transported to the polishing table 54, the control computer 130 so controls the polishing apparatus as to polish the semiconductor wafer under the polishing conditions read from the storage device. The semiconductor wafer polishing conditions include the rotational speed of the polishing pad, the rotational speed of the semiconductor wafer (top ring), the swinging speed of the semiconductor wafer (top ring), the swinging range of the semiconductor wafer (top ring), the polishing time, the polishing pressure, the flow rate of a slurry supplied, etc.
On completion of the polishing of the semiconductor wafer, the control computer 130 executes the following two lines of processes in parallel: a line in which the semiconductor wafer is cleaned and dried, and then returned to the wafer cassette 21; and a line in which the polishing pad 10 is dressed and cleaned to prepare for the next polishing.
A description will be made first of the process line for dressing and cleaning the polishing pad to prepare for the next polishing. This line of process comprises three operations the operation of dressing the polishing pad; the operation of cleaning the polishing pad; and the operation of monitoring adhesion of foreign matter to the surface of the polishing pad. On completion of the polishing of the semiconductor wafer, the control computer 130 executes the dressing routine shown in
The dressing routine shown in
The polishing pad cleaning routine shown in
In the case where the semiconductor wafer after polishing is not 3nth, the control computer 130 so controls the polishing apparatus as to evenly clean the entire polishing pad 10 with the brush of the cleaning section 112 under the normal cleaning conditions which have been read by the computer from the storage device at the start of the polishing process. The normal cleaning conditions include the rotational speed of the brush, the swinging speed of the brush, the swinging range of the brush, the pressure of the brush, the cleaning time, etc. The rotational speed of the polishing pad during the cleaning is also the rotational speed of the polishing pad during its dressing which is carried out in parallel with the cleaning. In the case where the semiconductor wafer after polishing is 3nth, the control computer 130 reads an intensive cleaning area of the polishing pad 10 from the storage device, and so controls the polishing apparatus as to intensively clean the intensive cleaning area with the brush of the cleaning section 112. The intensive cleaning area is an intensive cleaning area which has been stored in the storage device prior to polishing, and/or an intensive cleaning area which has been stored in the storage device in the below-described intensive cleaning area calculation routine. In this embodiment, the intensive cleaning area is stored as the zone number(s) of one or more of the 5 ring-shaped divisional zones of the polishing pad 10, shown in
The polishing apparatus of this embodiment employs, as the brush of the cleaning section 112, a brush having a diameter which is larger than the width of the intensive cleaning area. Accordingly, by appropriately setting the position of the brush of the cleaning section 112 based on the intensive cleaning area that the control computer 130 has read from the storage device, the intensive cleaning area of the polishing pad 10 can be intensively cleaned without swinging the brush. The position of the brush of the cleaning section 112 is set by the control computer 130 as the coordinates of the center of the brush such that the distance of the brush center from the rotation center of the polishing table 54 takes an intermediate value between the inside radius and the outside radius of the zone designated as the intensive cleaning area. It is also possible to pre-store such positions of the brush in the storage device that each of the 5 zones shown in
A description will now be given of the routine for monitoring foreign matter adhesion by evaluation of the polishing pad, shown in
The control computer 130 monitors signals from the adhesion region specifying section 110 while the termination flag of foreign matter adhesion monitoring by evaluation of polishing pad is OFF. When foreign matter adheres to the surface of the polishing pad 10, a peak P, as shown in
When the control computer 130 has determined adhesion of foreign matter to the polishing pad 10, the control computer 130 turns a foreign matter adhesion flag ON. The foreign matter adhesion flag is ON while foreign matter remains adhering to the polishing pad 10, i.e., while a displacement sensor 224, with which a peak P has been detected, keeps sending a signal with the peak P appearing repeatedly in synchronization with the rotating cycles of the polishing pad.
After turning the foreign matter adhesion flag ON, the control computer 130 specifies a foreign matter adhesion area. In this embodiment, a foreign matter adhesion area corresponds to the detection area of the displacement sensor 224 with which the peak P has been detected (see
In the polishing apparatus of this embodiment, the brush of the cleaning section 112 has a diameter which is larger than the width of the intensive cleaning area. Accordingly, by appropriately setting the position of the brush based on the specified foreign matter adhesion area, the foreign matter adhesion area can be intensively cleaned without swinging the brush. The position of the brush is set by the control computer 130 as the coordinates of the center of the brush such that the distance of the brush center from the rotation center of the polishing table 54 takes an intermediate value between the inside radius and the outside radius of the ring-shaped zone designated as the foreign matter adhesion area. It is also possible to pre-store such positions of the brush in the storage device that each of the 5 zones shown in
After cleaning the specified foreign matter adhesion area with the brush of the cleaning section 112 for the cleaning time set in the intensive cleaning conditions, the control computer 130 again determines the presence or absence of foreign matter. In the case where foreign matter, adhering to the polishing pad 10, still exists, the above processing is repeated. In the case where there is no foreign matter adhering to the polishing pad 10, the foreign matter adhesion flag is turned OFF, and the polishing pad cleaning routine is resumed. If the determination is made past a cleaning termination time as scheduled in the polishing pad cleaning routine, the control computer 130 immediately executes processing for the termination of the polishing pad cleaning routine.
When the termination flag of foreign matter adhesion monitoring by evaluation of polishing pad is turned ON, the control computer 130 moves the adhesion region specifying section 110 to the retreat area, thereby terminating the routine for monitoring foreign matter adhesion by evaluation of the polishing pad.
The termination flag of foreign matter adhesion monitoring by evaluation of polishing pad is not turned ON while the foreign matter adhesion flag is ON, as shown in
In parallel with the cleaning of the specified foreign matter adhesion area, the control computer 130 makes the calculation of intensive cleaning area. In the intensive cleaning area calculation routine, as shown in
When foreign matter, which has not been removed from the polishing pad 10 after intensive cleaning, is detected again, the intensive cleaning area calculation routine is not executed in order to avoid double counting. Whether detection of particular foreign matter is re-detection of the same foreign matter or not is determined by whether or not a peak P in a signal from the relevant displacement sensor 224 appears periodically in synchronization with the rotation of the polishing pad.
Returning to the main routine for polishing shown in
On completion of the cleaning and drying of the semiconductor wafer with the cleaning device 26, the control computer 130 so controls the polishing apparatus as to transport the semiconductor wafer by the transport robot 81 from the cleaning device 26 to the support 28, and then transport the semiconductor wafer by the transport robot 24 to the adhesion region specifying section 120.
After the semiconductor wafer has been transported to the adhesion region specifying section 120, the control computer 130 executes a routine for determination of foreign matter adhesion by evaluation of the polished surface of the semiconductor wafer (polishing object) to carry out determination of adhesion of foreign matter to the surface of the polishing pad (polishing member) and specification of a foreign matter adhesion area. In the routine for determination of foreign matter adhesion by evaluation of the polished surface, the control computer 130 executes the steps shown in
The control computer 130 first executes shooting the polished surface of the semiconductor wafer with the adhesion region specifying section 120 and taking in the image data. Corrections, such as denoising, sharpening, binarization, etc. of the taken image data and line extraction of the corrected image data are then performed. Thereafter, in order to determine whether an extracted line is a scratch or not, the control computer 130 executes pattern recognition. In the pattern recognition, a determination is made as to whether an extracted line is a scratch or not based on the length, the shape, etc. of the extracted line. If the absence of a scratch in the polished surface is determined, then the control computer 130 terminates the routine for determination of foreign matter adhesion by evaluation of the polished surface.
If the presence of a scratch in the polished surface is determined, the control computer 130 analyzes the particular image data from which the line, determined as the scratch, is extracted, and specifies a radial density distribution or a circumferential density distribution of the scratch, the presence or absence of the scratch at a specified position on the polished surface, etc. as a detection pattern. Thereafter, the control computer 130 determines a standard pattern which is most similar to the detection pattern by the nearest neighbor method, and specifies the foreign matter adhesion area (distance of the foreign matter from the center of the polishing pad), corresponding to the standard pattern, as the foreign matter adhesion area in the surface of the polishing pad (polishing member).
Next, the control computer 130 determines to which zone of the 5 zones shown in
If the polishing pad cleaning routine is in execution when the intensive cleaning is about to start, the polishing pad cleaning routine is stopped. If the intensive cleaning in the routine for monitoring foreign matter adhesion by evaluation of the polishing pad is in execution, the intensive cleaning in the present routine is waited until completion of the intensive cleaning in the routine for monitoring foreign matter adhesion by evaluation of the polishing pad.
In this embodiment, the brush of the cleaning section 112 has a diameter which is sufficiently larger than the width of the annular foreign matter adhesion area, corresponding to the standard pattern, of the polishing pad. Accordingly, by appropriately setting the position of the brush based on the specified foreign matter adhesion area, the foreign matter adhesion area can be intensively cleaned without swinging the brush. The position of the brush is set as the coordinates of the center of the brush by the control computer 130 such that the distance of the brush center from the rotation center of the polishing table 54 coincides with the specified foreign matter adhesion area corresponding to the standard pattern.
After carrying out cleaning of the specified foreign matter adhesion area with the cleaning section 112 for the cleaning time set in the read intensive cleaning conditions, the control computer 130 turns the foreign matter adhesion flag OFF to terminate the routine for determination of foreign matter adhesion by evaluation of the polished surface. If the polishing pad cleaning routine has been suspended, the polishing pad cleaning routine is resumed. If, however, a cleaning termination time as scheduled in the polishing pad cleaning routine is past, the control computer 130 immediately executes processing for the termination of the polishing pad cleaning routine.
In parallel with the intensive cleaning of the foreign matter adhesion area with the cleaning section 112, the control computer 130 executes the intensive cleaning area calculation routine in the manner described above. In the calculation of an intensive cleaning area, stored data on zones specified as foreign matter adhesion areas in the above-described manner is utilized to determine an intensive cleaning area. Alternatively, it is possible to store foreign matter adhesion areas as specified by pattern recognition.
Returning to the main routine for polishing shown in
While the present invention has been described in terms of the preferred embodiments mainly with reference to
Though the above-described chemical mechanical polishing apparatus employs as the adhesion region specifying sections 110, 111 the adhesion region specifying section 226 shown in
Though the above-described chemical mechanical polishing apparatus has both the adhesion region specifying sections 110, 111 which directly detect foreign matter on a polishing member (polishing pad) and the adhesion region specifying section 120 which detects foreign matter on a polishing member (polishing pad) indirectly by evaluation of the surface (polished surface) of a polishing object (semiconductor wafer) after polishing, a chemical mechanical polishing apparatus according to the present invention may have only one of the two types of adhesion region specifying sections. Further, a chemical mechanical polishing apparatus according to the present invention may not be provided with an adhesion region specifying section, but provided with a control section which reads information from a storage medium storing information on an intensive cleaning position or an intensive cleaning area in the surface of a polishing member, and so controls the above-described cleaning section as to intensively clean the intensive cleaning position or the intensive cleaning area in the surface of the polishing member. The intensive cleaning of the intensive cleaning position or the intensive cleaning area can prevent adhesion of foreign matter to the surface of the polishing pad.
Though the entire process is controlled by the single control computer 130 in the above-described chemical mechanical polishing apparatus, it is also possible to provide an independent control section for an adhesion region specifying section. In this case, a control section for controlling the entire chemical mechanical polishing apparatus and the control section for controlling the adhesion region specifying section will be able to communicate with each other so that the control sections can cooperate with each other in performing a polishing process. Further in this case, a specified foreign matter adhesion area may be stored in a storage device provided in the adhesion region specifying section.
The following information, for example, is stored in the storage device 144:
A. Adhesion Region Specifying Apparatus Control ProgramA-1. Various conditions reading routine
A-2. Standard pattern production routine
A-3. Image reading routine
A-4. Image analysis routine
A-5. Foreign matter adhesion area display routine
-
- etc.
B-1. Polishing conditions (polishing recipe)
-
- B-1-1. Rotational speed of polishing pad
- B-1-2. Rotational speed of semiconductor wafer (top ring)
- B-1-3. Swinging speed of semiconductor wafer (top ring)
- B-1-4. Swinging range of semiconductor wafer (top ring)
- B-1-5. Polishing time
B-2. Geometric parameters
-
- B-2-1. Diameter of semiconductor wafer
- B-2-2. Coordinates of rotation center of polishing pad
- B-2-3. Coordinates of rotation center of top ring
- B-2-4. Coordinates of pivot center of top ring
- B-2-5. Radius of pivoting of top ring
- etc.
C-1. Standard patterns for image recognition
C-2. Shot image of polished surface
-
- etc.
A method for specifying a foreign matter adhesion area in a surface of a polishing member, such as a polishing pad, from a polished surface of a polishing object, such as a semiconductor wafer, with a scratch, caused by the foreign matter on the polishing member, formed in the polished surface, by using the adhesion region specifying apparatus, will now be described with reference to the flow of a process for specifying a foreign matter adhesion area, shown in
First, upon input of a command to start the process from an input device, such as a keyboard, a mouse, touch panel, etc., the central processing unit (arithmetic unit) 140 receives a command of a control program stored in the main memory 142 and reads various conditions from the storage device 144. As described above, polishing conditions (polishing recipe), geometric parameters, etc. are stored as various conditions in the storage device 144.
In the case where the polishing object is a semiconductor wafer and the polishing apparatus is one as shown in
The various conditions are read in the storage device 144 from the polishing apparatus or an external storage device using the input device (reading device) 146 installed in the adhesion region specifying apparatus, or inputted to the storage device 144 manually from an input device, such as a keyboard, a mouse or a touch panel, prior to the process for specifying a foreign matter adhesion area. Besides the various conditions, a control program for the adhesion region specifying apparatus and information on foreign matter adhesion are also stored in the storage device 144.
After reading the various conditions from the storage device 144, the central processing unit 140, on receipt of a command of the control program in the main memory 142, produces standard patterns for image recognition, which are to be used in specifying a foreign matter adhesion area, based on the read various conditions, and stores the produced standard patterns as information on foreign matter adhesion in the storage device 144. The standard patterns are, for example, data on tracks of foreign matter as shown in
Next, the central processing unit 140, on receipt of a command of the control program in the main memory 142, reads a shot image of a polished surface with a scratch or scratches. The central processing unit 140 may either read the shot image from a photographic device using the input device (reading device) 146 or read the shot image from an external storage medium, such as a floppy disk or a CD-ROM. Alternatively, the central processing unit 140 may read the shot image of a polished surface, pre-stored in the storage device of the adhesion region specifying apparatus.
Next, the central processing unit 144, on receipt of a command of the control program in the main memory 142, performs corrections (image transformation), such as denoising, sharpening, binarization, etc., on the read image data and line extraction (feature extraction) on the corrected image data. Thereafter, the central processing unit 140, on receipt of a command of the control program in the main memory 142, executes pattern recognition (image recognition) to extract a scratch from extracted lines.
Next, the central processing unit 140, on receipt of a command of the control program in the main memory 142, designates an image data, from which the scratch is extracted, as a detection pattern and determines by image recognition a standard pattern which is most similar to the detection pattern, and specifies the foreign matter adhesion area (distance of foreign matter from the center of polishing pad), corresponding to the standard pattern, as a foreign matter adhesion area in the surface of the polishing member.
The image recognition includes pattern recognition, such as the nearest neighbor method, Bayes decision rule, dynamic programming matching (DP matching), Hidden Markov Model, etc. In this embodiment, image analysis implies execution of at least one of image transformation, feature extraction and image recognition. Thereafter, the central processing unit 140, on receipt of a command of the control program in the main memory 142, output the foreign matter adhesion area to the output device 148, such as a printer or a display.
The use of the adhesion region specifying apparatus of this embodiment makes it possible to specify a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, such as a polishing pad, when a scratch or scratches are formed in a polished surface of a polishing object, such as a semiconductor wafer, after carrying out polishing using a polishing apparatus having no foreign matter region specifying section.
Though in this embodiment standard patterns are produced in the process for specifying a foreign matter adhesion area, it is of course possible to pre-store prepared standard patterns in the storage device 144 of the adhesion region specifying apparatus or in an external storage medium, without producing the standard patterns, and read the stored standard patterns from the storage device or medium in the process for specifying a foreign matter adhesion area. It is also possible to store the standard patterns, produced in the process for specifying a foreign matter adhesion area, not in the storage device 144 of the adhesion region specifying apparatus, but in an external storage device, and read the stored data from the external device in the specifying process.
While the process for specifying a foreign matter adhesion area using data on tracks of foreign matter has described, it is possible to use, instead of the track data, data on a radial or circumferential density distribution of scratch, data on the presence or absence of a scratch at a specified position on a polished surface, etc., analyzed from the track data, in specifying a foreign matter adhesion area. In this case, image data, from which a scratch is extracted, is analyzed to determine a radial or circumferential density distribution of the scratch, the presence or absence of the scratch at a specified position on the polished surface, etc., and the determined data is used as a detection pattern. Accordingly, data on a radial or circumferential density distribution of a scratch, the presence or absence of a scratch at a specified position on the polished surface, etc. is used as a standard pattern.
The present invention makes it possible to prevent scratches in a polished surface of a polishing object, which would be caused by foreign matter adhering to a surface of a polishing member, thus preventing the attendant lowering of the yield even when the polishing object is large-sized. In particular, detection of foreign matter adhering to a surface of a polishing member, makes it possible to stop polishing and carry out cleaning of the surface of the polishing member or replacement of the polishing member, thereby preventing scratches on a polishing object and preventing the lowering of the yield due to scratches. By specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member, and intensively cleaning the foreign matter adhesion position or the foreign matter adhesion area after stopping polishing or during polishing, it becomes possible to effectively remove foreign matter from the polishing member and prevent scratches, caused by the foreign matter, on a polishing object, thereby preventing the lowering of the yield. Furthermore, the prevent invention makes it possible to effectively prevent adhesion of foreign matter to a surface of a polishing member, thus preventing scratches on a polishing object and preventing the lowering of the yield due to scratches.
Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.
Claims
1. A polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising:
- specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of the polishing member; and
- intensively cleaning the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
2. A polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising:
- reading information on an intensive cleaning position or an intensive cleaning area in a surface of the polishing member from a storage medium in a computer; and
- intensively cleaning the intensive cleaning position or the intensive cleaning area in the surface of the polishing member.
3. A polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising:
- reading information on an intensive cleaning position or an intensive cleaning area in a surface of the polishing member from a storage medium in a computer;
- specifying a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member; and
- intensively cleaning at least one of the intensive cleaning position or the intensive cleaning area in the surface of the polishing member and the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
4. A polishing method for polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, comprising:
- specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of the polishing member;
- storing foreign matter adhesion positions or foreign matter adhesion areas in the surface of the polishing member;
- calculating an intensive cleaning position or an intensive cleaning area in the surface of the polishing member from the stored foreign matter adhesion positions or foreign matter adhesion areas; and
- intensively cleaning at one of the calculated intensive cleaning position or foreign matter adhesion area in the surface of the polishing member and the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member.
5. The polishing method according to claim 1, wherein adhesion of foreign matter to the surface of the polishing member is detected by a detection section to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
6. The polishing method according to claim 5, wherein the detection of adhesion of foreign matter to the surface of the polishing member is performed by image analysis of the surface.
7. The polishing method according to claim 3, wherein adhesion of foreign matter to the surface of the polishing member is detected by a detection section to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
8. The polishing method according to claim 7, wherein the detection of adhesion of foreign matter to the surface of the polishing member is performed by image analysis of the surface.
9. The polishing method according to claim 4, wherein adhesion of foreign matter to the surface of the polishing member is detected by a detection section to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
10. The polishing method according to claim 9, wherein the detection of adhesion of foreign matter to the surface of the polishing member is performed by image analysis of the surface.
11. The polishing method according to claim 1, wherein the polished surface of the polishing object after polishing is evaluated to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
12. The polishing method according to claim 11, wherein the evaluation of the polished surface of the polishing object after polishing is performed by image analysis of the polished surface.
13. The polishing method according to claim 3, wherein the polished surface of the polishing object after polishing is evaluated to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
14. The polishing method according to claim 13, wherein the evaluation of the polished surface of the polishing object after polishing is performed by image analysis of the polished surface.
15. The polishing method according to claim 4, wherein the polished surface of the polishing object after polishing is evaluated to specify the foreign matter adhesion position or the foreign matter adhesion area in the surface of the polishing member.
16. The polishing method according to claim 15, wherein the evaluation of the polished surface of the polishing object after polishing is performed by image analysis of the polished surface.
17. A method for specifying a cleaning region in a surface of a polishing member, comprising:
- evaluating the surface of the polishing member to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member as a position or area to be intensively cleaned; and
- storing the specified intensive cleaning position or intensive cleaning area.
18. A method for specifying a cleaning region in a surface of a polishing member, comprising polishing a polishing object by applying pressure between a polishing member and the polishing object while moving the polishing member and the polishing object relative to each other, and evaluating a polished surface of the polishing object to specify a foreign matter adhesion position or a foreign matter adhesion area in the surface of the polishing member as a position or area to be intensively cleaned.
19. The method according to claim 18, wherein information on the specified foreign matter adhesion position or foreign matter adhesion area in the surface of the polishing member is stored.
20. The method according to claim 18, wherein the evaluation of the polished surface of the polishing object is performed by image analysis of the polished surface.
21. A method for specifying a foreign matter adhesion region, comprising specifying a foreign matter adhesion position or a foreign matter adhesion area in a surface of a polishing member by image analysis of a shot image of a polished surface of a polishing object.
22-75. (canceled)
Type: Application
Filed: Mar 29, 2007
Publication Date: Oct 4, 2007
Inventors: Akira Fukuda (Kanagawa-ken), Hirokuni Hiyama (Kanagawa-ken), Manabu Tsujimura (Tokyo)
Application Number: 11/730,141
International Classification: B24B 1/00 (20060101);
