Slurry distributor for chemical mechanical polishing apparatus and method of using the same
A polishing apparatus (100) is provided for polishing a substrate (102) that has slurry distributor (125) which improves planarization uniformity. Generally, apparatus (100) includes: (i) platen (106) with polishing surface (110); (ii) head (116) adapted to hold substrate (102) against polishing surface; (iii) mechanism to rotate platen (106) during polishing; (iv) dispenser (124) having nozzles (126, 128) to dispense slurry on the surface (110); and (v) distributor (125) between the nozzles (126, 128) and head (116). In one embodiment, apparatus (100) further includes a wiper (180) between head (116) and distributor (125) to remove used slurry and polishing byproducts from surface (110), thereby reducing agglomerations or deposits that can damage substrate (102) and improving yield. Optionally, apparatus (100) further includes dispenser (186) for dispensing a fluid before and/or after wiper (180) to substantially eliminate buildup of deposits. Method for polishing and substrate polished according to method.
This application is a divisional of and claims the benefit of priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 10/234,780 filed 3 Sep. 2002 and entitled Slurry Distributor For Chemical Mechanical Polishing Apparatus And Method Of Using The Same, which application claimed priority from U.S. Provisional Patent Application Ser. No. 60/323,117, filed Sep. 10, 2001, each of which applications are incorporated herein by reference.
FIELD OF THE INVENTIONThis invention pertains generally to systems, devices, and methods for polishing and planarizing substrates, and more particularly to an apparatus and method for distributing slurry on a polishing surface of a chemical mechanical polishing (CMP) apparatus.
BACKGROUND OF THE INVENTIONAs feature size decreases, density increases, and the size of semiconductor wafers or substrates increase, Chemical Mechanical Planarization (CMP) process requirements become more stringent. Substrate to substrate process uniformity as well as intra-substrate planarization uniformity are important issues from the standpoint of producing semiconductor products at a low cost. As the size of dies increases a flaw in one small area increasing results in rejection of a relatively large circuit so that even small flaws have relatively large economic consequences in the semiconductor industry.
Many factors are known in the art to contribute to uniformity problems. These include distribution of a slurry between a surface of the substrate and polishing surface during the polishing operation when there is relative motion between a polishing head on which the substrate is held and the polishing surface during the polishing operation. Slurry is a, usually, chemically active liquid having an abrasive material suspended therein that is used to enhance the rate at which material is removed from the substrate surface.
One problem with slurry distribution in a conventional CMP apparatus a non-uniform distribution of slurry on a polishing surface.
As illustrated in
One prior art approach attempting to provide a more uniform distribution of slurry is described in U.S. Pat. No. 5,709,573, to Guthrie et al. (GUTHRIE). GUTHRIE discloses a radially positioned flexible member in contact with the polishing surface to sweep the slurry across the polishing surface. While an improvement over conventional slurry dispensers, this approach is not wholly satisfactory for a number of reasons.
One problem with the approach taught in GUTHRIE is that the constant contact between the flexible member and the polishing surface during polishing operations causes rapid wear of the flexible member. This in turn leads to the need to frequently replace the flexible member. In addition to the cost of replacement parts, this results in excessive down time or loss of availability or the apparatus for processing due to the time needed to replace the flexible member and the time need to re-characterize the polishing process or apparatus. Moreover, prior to replacement, as the flexible member wears the amount and distribution of slurry across the polishing surface can vary introducing a new source of non-uniformity. This is particularly a problem with polishing surfaces comprising a pattern of features, such as indentations in a porous polishing surface or concentric grooves, for aiding in slurry distribution. These features cause the flexible member to wear unevenly across the surface in contact with the polishing surface, resulting in a non-uniform distribution of slurry across the polishing surface.
Another problem with conventional CMP apparatuses and methods, related to the problem with non-uniform distribution described above, is the inefficient use and wastage of slurry. Because the slurry is dispensed onto the polishing surface ahead of the polishing head, an excess of slurry must typically be dispensed to ensure that when it flows across the polishing surface it will cover the entire area between the substrate and the surface. Because of strict requirements concerning the purity of the slurry and in particular the size of the abrasive particles suspended therein, slurry tends to be expensive. Moreover, because materials used in fabricating semiconductors are often hazardous to people and to the environment, used slurry, which can contain significant amounts of material removed from the substrates, must be disposed of as hazardous waste. Thus, a significant factor in the cost of operating conventional CMP apparatuses is the cost of supplying and disposing of the slurry.
Yet another problem with conventional CMP apparatuses and methods is the buildup of solid polishing byproducts on the polishing surface that can damage or destroy a substrate being polished. These byproducts include material removed from the surface of the substrate and agglomerations of abrasives from old or dried out slurry. This particularly a problem for CMP apparatuses including polishing surfaces with numerous small, shallow grooves for the distribution of slurry, or porous polishing pads or coverings.
Accordingly, there is a need for an apparatus and method that provides a controlled or uniform distribution of slurry across the polishing surface to provide improved planarization uniformity. There is a further need for an apparatus and method capable of restricting slurry dispensed on the polishing surface to the portion of the polishing surface over which the polishing head passes during the polishing operation, thereby reducing waste of slurry. There is a yet further need for an apparatus and method capable of removing used slurry and polishing byproducts from the polishing surface thereby eliminating buildup of solid polishing byproducts that can damage the substrate.
SUMMARYThe present invention relates to an apparatus and method for distributing slurry on a polishing surface of a CMP apparatus that achieves a high-planarization uniformity across a surface of a substrate.
According to one aspect of the present invention, a polishing apparatus is provided for removing material from a surface of a substrate. Generally, the polishing apparatus includes: (i) a platen having a polishing surface thereon; (ii) a polishing head adapted to hold the substrate against the polishing surface during a polishing operation; (iii) a drive mechanism to rotate the platen providing a relative motion between the polishing head and the polishing surface during the polishing operation; (iv) a dispenser having a number of nozzles adapted to dispense chemical on the polishing surface; and (v) a spreader or distributor positioned between the nozzles of the dispenser and the polishing head. The distributor mixes and uniformly distributes chemical between the surface of the substrate and the polishing surface during the polishing operation when there is relative motion between the polishing head and the polishing surface. The chemical can be a slurry having, for example, a solid abrasive material suspended in a fluid, or, where the polishing surface includes a fixed abrasive thereon, the chemical can be water.
In one embodiment, the distributor is made from a rigid, ceramic, glass or polymeric material, such as one or more of the following polymers: polyesters; polyethylene terephthalate; polyimide; polyphenylene sulfide; polyetherketone; polytetrafluoroethylene; and polybenzimidazole, and is adapted to provide a substantially planar lower surface separated from and in a facing relationship with a portion of the polishing surface. The lower surface of the distributor is separated from the polishing surface by a predetermined amount based on a desired removal or polishing rate and in further consideration of the viscosity of the chemical or slurry used. Preferably, the distributor includes a chamfered edge to facilitate movement or flow of the chemical under the lower surface thereof. More preferably, the distributor is oriented to form a predetermined angle relative to a plane of the polishing surface, the predetermined angle selected to further facilitate movement or flow of the chemical under the lower surface thereof. It has been found suitable predetermined angles for most polishing or planarizing operations used in processing semiconductor substrates are from about 10 to about 80 degrees. More preferably, the predetermined angles are from about 20 to about 40 degrees, and most preferably about 30 degrees.
In another embodiment, the distributor further includes one or more guide or spacers on the lower surface thereof, the spacers adapted to contact the polishing surface during a polishing operation and to guide or position the distributor relative to the polishing surface. Preferably, the spacers include an adjustment mechanism to adjust a gap between the lower surface of the distributor and the polishing surface, thereby enabling a rate of removal of material from the substrate to be varied.
Optionally, polishing apparatus further includes an actuator for positioning the distributor against or adjacent to the polishing surface. Generally, the actuator can include spring actuators, gravity actuators, hydraulic actuators, pneumatic actuators, or electromagnetic actuators, such as solenoids.
The nozzles can be located distal from or proximal to the distributor. In one embodiment, the nozzles are abutting or affixed to a support supporting the distributor in position over the polishing surface. Optionally, one or more of the nozzles are adapted to dispense the chemical at a different rate than the remainder of the nozzles. For example, nozzles near either an inner or outer end of the dispenser can dispense chemical at a lower rate than those more centrally located to more tightly focus or constrain the chemical on that portion of the polishing surface over which the polishing head will pass. Alternatively, the nozzle near the inner end of the dispenser can dispense chemical at a higher rate than the other nozzles to compensate for a lower speed of the portion of the polishing surface near a center of the rotating platen, thereby providing a more uniform removal rate throughout the rotation of the substrate on the polishing head. Typically, each of the nozzles is adapted to dispense from about 20 milliliters (ml) to about 200 ml of chemical per second.
Alternatively, the distributor is oriented to form a predetermined angle relative to a radius of the polishing surface. The predetermined angle can be adjusted or selected to direct more or less of the chemical to an inner or outer portion of the polishing surface, thereby altering the removal rate over a portion of the polishing surface or more tightly focusing on the polishing head. Preferably, the predetermined angle selected to uniformly distribute the chemical in the path of the polishing head. It has been found suitable predetermined angles for most polishing or planarizing operations used in processing semiconductor substrates are from about 1 to about 30 degrees. More preferably, the predetermined angles are from about 2 to about 20 degrees, and most preferably less than about 10 degrees.
In yet another aspect, the invention is directed to a polishing apparatus including, in addition to a distributor adapted to mix and uniformly distribute a chemical or slurry on a polishing surface, a wiper adapted to remove used chemical and polishing byproducts from the polishing surface after the surface has passed under a polishing head. Generally, the wiper is positioned between the polishing head and the distributor, and is oriented to form an angle relative to a radius of the polishing surface, to direct the used chemical and polishing byproducts off an outer edge of the polishing surface or platen. Preferably, the wiper forms an angle of from about 5 to about 30 degrees relative to a radius of the polishing surface.
In one embodiment, the wiper further includes a vacuum port to vacuum used chemical and polishing byproducts from the polishing surface. This is particularly advantageous for use with a polishing surface having features such as grooves or a porous polymer polishing pad.
In another embodiment, the polishing apparatus can further include a cleaning fluid dispenser for dispensing a cleaning fluid, such as water, onto the polishing before and/or after the wiper to clean the polishing surface during a cleaning operation. In one version of this embodiment, the cleaning fluid dispenser is adapted to dispense cleaning fluid on the polishing surface ahead or upstream of the wiper during the polishing operation to reduce or substantially eliminate buildup of solid polishing byproducts that can damage the substrate.
In yet another aspect, the invention is directed to a method of polishing a substrate having a surface using a polishing apparatus having a polishing surface and a polishing head adapted to hold the substrate during a polishing operation. Generally, the method involves: (i) positioning the substrate on the polishing head; (ii) holding the polishing head so as to press the surface of the substrate against the polishing surface; (iii) dispensing a chemical onto the polishing surface using a dispenser having a number of nozzles through which the chemical is dispensed; and (iv) mixing and uniformly distributing the chemical on the polishing surface using a distributor positioned between the nozzles and the polishing head.
Optionally, the method can further include the step of removing used chemical and polishing byproducts from the polishing surface after the chemical has passed under the polishing head using a wiper positioned between the polishing head and the distributor. Preferably, the wiper has a lower surface with a linear edge in contact with a portion of the polishing surface substantially entirely along the length of the linear edge. More preferably, the wiper or the linear edge thereof forms a predetermined angle relative to a radius of the polishing surface, the predetermined angle selected to direct the used chemical and polishing byproducts off an outer edge of the polishing surface or platen.
Advantages of the apparatus and method of the present invention include any or all of the following:
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- (i) improved planarization uniformity due to uniform distribution of slurry across the polishing surface;
- (ii) improved planarization uniformity of substrates initially having non-planar layers deposited thereon, due to tailored or focused distribution of slurry across the polishing surface;
- (iii) reduced wasting of slurry, due to tailored or focused distribution of slurry across the polishing surface; and
- (iv) improved yields due to reduction or eliminating of buildup or deposits of solid polishing byproducts that can damage the substrate.
These and various other features and advantages of the present invention will be apparent upon reading of the following detailed description in conjunction with the accompanying drawings, where:
The inventive structure and method are now described in the context of specific exemplary embodiments illustrated in the figures. Those skilled in the art will appreciate that various changes and modifications can be made while remaining within the scope of the claimed invention. For example, for purposes of clarity the invention is described in context of a Chemical Mechanical Polishing (CMP) system having a single polishing head. However, those skilled in the art will appreciate that the apparatus and method of the invention can also be utilized with CMP systems having multiple polishing heads.
Referring to
For purposes of clarity, many of the details of the CMP apparatus 100 that are widely known and are not relevant to the present invention have been omitted. CMP apparatuses 100 are described in more detail in, for example, in commonly assigned, co-pending U.S. patent application Ser. No. 09/570,370, filed 12 May 2000 and entitled System and Method for Pneumatic Diaphragm CMP Head Having Separate Retaining Ring and Multi-Region Wafer Pressure Control; Ser. No. 09/570,369, filed 12 May 2000 and entitled System and Method for CMP Having Multi-Pressure Zone Loading For Improved Edge and Annular Zone Material Removal Control; and Ser. No. 09/854,189, filed 11 May 2001 and entitled System and Method for CMP Having Multi-Pressure Annular Zone Subcarrier Material Removal Control, each of which is incorporated herein by reference in its entirety.
The CMP apparatus 100 includes a base 104 rotatably supporting a large rotatable platen 106 with a polishing pad 108 mounted thereto, the polishing pad having a polishing surface 110 on which the substrate 102 is polished. The polishing pad 108 is typically a polyeurethane material, such as that available from RODEL of Newark Del. Additionally, a number of recesses (not shown in
In accordance with the present invention, the CMP apparatus further includes a chemical or slurry dispenser 124 and a distributor 125 which will now be described with reference to FIGS. 3 to 14.
Alternatively, the nozzles 126, 128, of the slurry dispenser 124 shown in
An embodiment of the distributor 125 according to the present invention will now be described with reference to
Alternatively, the distributor 125 can include an arc or a curved member, or two or more members intersecting at angles to direct the slurry to provide a desired non-uniform distribution of slurry 129 across the polishing surface 110. For example, for planarizing copper layers as noted above.
Generally, the distributor 125 is adapted to provide a shape having a substantially planar lower surface (not shown in this figure) separated from and in a facing relationship with a portion of the polishing surface 110. Preferably, to reduce or eliminate potential contamination of the substrate 102 during the polishing operation, the distributor 125 is made from a glass, ceramic, or rigid high purity polymer material. More preferably, the distributor 125 is made from a material commonly used in retaining rings (not shown) disposed about the substrate 102 held on the polishing head 116 in a conventional CMP apparatus. Most preferably, the distributor is made from a polymer thick film (PTF) including one or more of the following polymers: polyesters; polyethylene terephthalate; polyimide; polyphenylene sulfide; polyetherketone; polytetrafluoroethylene; and polybenzimidazole.
The lower surface of the distributor 125 is separated from the polishing surface 110 by a predetermined amount or gap based on a thickness of a layer or film of slurry required to provide a desired removal or polishing rate. In addition to the desired polishing rate, the predetermined gap by which the distributor 125 is separated from the polishing surface 110 further depends on a viscosity of the chemical or slurry 129 used.
Another embodiment of the slurry delivery apparatus 123 will now be described with reference to
Generally, the actuator 146 is selected from a group consisting of: gravity actuators; hydraulic actuators; pneumatic actuators; and electromagnetic actuators or solenoids. In the embodiment shown the actuator 146 includes a piston 148 slidably fitted into a chamber 150 into which a hydraulic or pnematic fluid is introduced, or from which it is withdrawn, to re-position the chamfered edge 140 of the distributor 125. It should be noted that the piston 148 and the chamber 150 can include one or more cylindrical pistons and chambers spaced apart along the length of the distributor 125, or a rectangular piston and chamber that extend substantially the entire length of the distributor. In a preferred embodiment, the actuator 146 includes a single hydraulic or pneumatic piston and cylinder, or a single solenoid joining or coupling the distributor 125 to the support 138 (not shown in this figure).
In another embodiment, the distributor 125 further includes one or more guides or spacers 152 on the lower surface 142 thereof, the spacers adapted to contact the polishing surface 110 during a polishing operation and to guide or position the distributor relative to the polishing surface.
A preferred embodiment of a distributor according to the present invention will now be described with reference to FIGS. 9 to 12.
Optionally, where the used slurry 129 is not removed from the polishing surface 110 after it has passed under the polishing head 116, the chamfered leading edge 154 further serves to recover this used slurry.
The ability of the distributor 125 of
In yet another embodiment shown in
In another aspect, the invention is directed to a CMP apparatus 100 including, in addition to the distributor 125, a wiper 180 adapted to remove used chemical or slurry 129 and polishing byproducts from the polishing surface 110 after it has passed under a polishing head 116.
In one embodiment, shown in
In another embodiment, shown in
As with the distributor 125, the wiper 180 can be joined to a support (not shown) via an actuator 188 that is capable of raising and lowering the wiper into position in contact with the polishing surface 110. The actuator 188 can include a spring actuators, gravity actuators, hydraulic actuators, pneumatic actuators, or electromagnetic actuators, such as solenoids.
A method of operating a CMP apparatus 100 according to the present invention will now be described with reference to
Optionally, the method can further include the step of removing used chemical or slurry and polishing byproducts from the polishing surface 110 after the chemical has passed under the polishing head 116 using a wiper 180 positioned between the polishing head 116 and the distributor 125 (step 208). Preferably, the method further includes the step of dispensing a cleaning fluid on the polishing surface 110 upstream from the wiper 180 to substantially eliminate buildup of polishing byproducts (step 210).
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best use the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
Claims
1. A polishing apparatus for removing material from a surface of a substrate, the polishing apparatus comprising:
- a platen having a polishing surface thereon;
- a polishing head adapted to hold the substrate against the polishing surface during a polishing operation;
- a drive mechanism for providing a relative motion between the polishing head and the polishing surface during the polishing operation;
- a dispenser having at least one nozzle adapted to dispense polishing liquid on the polishing surface;
- a distributor positioned between the nozzle of the dispenser and the polishing head; and
- at least one spacer on a lower surface of the distributor, the at least one spacer positioned between the distributor and the polishing surface, and adapted to contact the polishing surface during the polishing operation and to position the distributor relative to the polishing surface;
- the distributor mixing and uniformly distributing polishing liquid between the distributor and the polishing surface during the polishing operation when there is relative motion between the polishing head and the polishing surface during the polishing operation.
2. A polishing apparatus according to claim 1, wherein the at least one spacer comprises an adjustment mechanism to adjust a gap between the lower surface of the distributor and the polishing surface, so that a rate of removal of material from the substrate can be varied.
3. A polishing apparatus according to claim 2, wherein the adjustment mechanism comprises a threaded rod or screw, or shims.
4. A polishing apparatus according to claim 1, wherein the at least one spacer comprises a material in contact with the polishing surface during the polishing operation selected from a group consisting of:
- a polymeric material;
- a ceramic material; and
- a glass material.
5. A polishing apparatus according to claim 1, wherein the distributor has a chambered edge.
6. A polishing apparatus according to claim 1, wherein the distributor comprises an integral dispenser for dispensing the polishing liquid.
7. A polishing apparatus according to claim 1, further comprising a wiper positioned above the polishing surface, for removing used polishing liquid and polishing byproducts from the polishing surface.
8. A polishing liquid distributor comprising:
- a distributor having a length greater than or substantially equal to a diameter of a polishing head holding a substrate to be polished; and
- at least one spacer on a lower surface of the distributor, the at least one spacer positioned between the distributor and the polishing surface, and adapted to contact the polishing surface during a polishing operation and to position the distributor relative to the polishing surface, the distributor mixing and uniformly distributing polishing liquid between the distributor and the polishing surface during the polishing operation when there is relative motion between the polishing head and the polishing surface during the polishing operation.
9. A polishing liquid distributor according to claim 8, wherein said distributor has a substantially planar lower surface separated from and in a facing relationship with the polishing surface.
10. A polishing liquid distributor according to claim 9, wherein the at least one spacer comprises an adjustment mechanism to adjust a gap between the lower surface of the distributor and the polishing surface, so that a rate of removal of material from the substrate can be varied.
11. A polishing liquid distributor according to claim 10, wherein the adjustment mechanism comprises a threaded rod or screw, or shims.
12. A polishing liquid distributor according to claim 8, wherein the at least one spacer comprises a material in contact with the polishing surface during the polishing operation, the material selected from a group consisting of:
- a polymeric material;
- a ceramic material; and
- a glass material.
13. A polishing liquid distributor according to claim 8, wherein the distributor bar has a chambered edge.
14. A polishing liquid distributor according to claim 8, wherein the distributor comprises an integral dispenser for dispensing the polishing liquid.
15. A polishing liquid distributor according to claim 8, wherein the distributor comprises a distributor bar.
16. A polishing liquid distributor according to claim 8, wherein the liquid distributor is for use in a chemical mechanical polishing apparatus.
17. A polishing apparatus according to claim 1, wherein the distributor comprises a distributor bar.
18. A polishing apparatus according to claim 1, wherein the polishing apparatus is a chemical mechanical polishing apparatus.
19. A polishing apparatus for removing material from a surface of a substrate, the polishing apparatus comprising:
- a platen having a polishing surface thereon;
- a polishing head adapted to hold the substrate against the polishing surface during a polishing operation;
- a drive mechanism for providing a relative motion between the polishing head and the polishing surface during the polishing operation;
- a dispenser having at least one nozzle adapted to dispense polishing liquid on the polishing surface;
- a distributor having at least one chambered edge and positioned between the nozzle of the dispenser and the polishing head, and having a substantially planar lower surface separated from and in a facing relationship with the polishing surface;
- at least one spacer on a lower surface of the distributor, the at least one spacer positioned between the distributor and the polishing surface, and adapted to contact the polishing surface during the polishing operation and to position the distributor relative to the polishing surface, the distributor mixing and uniformly distributing polishing liquid between the distributor and the polishing surface during the polishing operation when there is relative motion between the polishing head and the polishing surface during the polishing operation; and
- a wiper positioned above the polishing surface, for removing used polishing liquid and polishing byproducts from the polishing surface;
- the at least one spacer comprises an adjustment mechanism to adjust a gap between the lower surface of the distributor and the polishing surface so that a rate of removal of material from the substrate can be varied, and comprises a material in contact with the polishing surface during the polishing operation selected from the group consisting of a polymeric material, a ceramic material; and a glass material; and
- the adjustment mechanism comprising a threaded rod or screw, or shims.
20. A method of removing material from a surface of a substrate, the method comprising:
- providing a platen having a polishing surface thereon;
- holding the substrate against the polishing surface in a polishing head during a polishing operation;
- generating a relative motion between the polishing head and the polishing surface during the polishing operation;
- dispensing polishing liquid on the polishing surface from a dispenser having at least one nozzle;
- positioning a distributor between the nozzle of the dispenser and the polishing head; and
- positioning at least one spacer on a lower surface of the distributor, the at least one spacer being positioned between the distributor and the polishing surface, and adapted to contact the polishing surface during the polishing operation and to position the distributor relative to the polishing surface,
- mixing and uniformly distributing polishing liquid with the distributor between the distributor and the polishing surface during the polishing operation when there is relative motion between the polishing head and the polishing surface during the polishing operation.
21. A method according to claim 20, wherein the removing material from a surface of a substrate comprises polishing a surface of a substrate.
22. A method according to claim 20, wherein the removing material from a surface of a substrate comprises planarizing a surface of a semiconductor wafer.
23. A substrate polished according to the method of claim 21.
24. A semiconductor wafer planarized according to the method of claim 22.
Type: Application
Filed: Jan 25, 2005
Publication Date: Jun 16, 2005
Inventors: Jiro Kajiwara (Saitama-ken), Gerard Moloney (Milpitas, CA), Jun Liu (Cupertino, CA), Junsheng Yang (Cupertino, CA), Ernesto Saldana (San Jose, CA), Cormac Walsh (Sunnyvale, CA), Alejandro Reyes (San Jose, CA)
Application Number: 11/043,531