METHOD FOR FABRICATING ELECTRONIC COMPONENT AND ELECTRO-PLATING APPARATUS
A method for fabricating an electronic component according to an Embodiment, includes a seed film forming process and an electro-plating process. In the seed film forming process, a seed film is formed above a substrate. In the electro-plating process, electro-plating is performed by soaking the seed film in a plating solution in a plating bath to which the plating solution being bubbled by a nitrogen gas is supplied, using the seed film as a cathode.
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-128060 filed on Jun. 3, 2010 in Japan, the entire contents of which are incorporated herein by reference.
FIELDEmbodiments described herein relate generally to a method for fabricating an electronic component and an electro-plating apparatus.
BACKGROUNDIn recent years, with higher integration and higher performance of semiconductor integrated circuits (LSI), new microprocessing technologies have been developed. Particularly recently, replacement of aluminum (Al) alloys as a conventional wire material by low-resistant copper (Cu) or Cu alloys (that is, copper-containing materials and hereinafter, collectively referred to as Cu) is under way to achieve faster LSIs. However, it is difficult to microprocess Cu by the dry etching method such as RIE (reactive ion etching) used frequently to form an Al-alloy wire. Therefore, the so-called damascene method by which an embedded wire is formed by depositing a Cu film on a grooved dielectric film and removing the Cu film excluding the Cu film embedded in the groove by the chemical mechanical polishing (CMP) method is mainly adopted. The Cu film is generally formed by first forming a thin Cu seed film by the sputter process or the like and then forming a laminated film of a thickness on the order of several hundred nm by the electro-plating method. Further, when a multilayer Cu wire is formed, particularly the wire formation method called a dual damascene structure can also be used. According to the method, a dielectric film is formed on a lower-layer wire to form a predetermined via hole and a trench (wire groove) for an upper-layer wire and then, Cu to be the wire material is embedded in the via hole and the trench simultaneously and further, unnecessary Cu in the upper layer is removed by the CMP method for planarization to form an embedded wire.
A Cu seed film formed by the sputter process has particularly a thin side wall and is easily dissolved by a plating solution. If an attempt is made to perform electro-plating on a portion where the Cu seed film has dissolved, no Cu film is formed because no current flows. Thus, even if a Cu film grown from therearound is completely embedded in such a portion, there is a problem that the portion has poor adhesion between the side wall and the Cu film, causing defects.
A method for fabricating an electronic component according to an Embodiment, includes a seed film forming process and an electro-plating process. In the seed film forming process, a seed film is formed above a substrate. In the electro-plating process, electro-plating is performed by soaking the seed film in a plating solution in a plating bath to which the plating solution being bubbled by a nitrogen gas is supplied, using the seed film as a cathode.
An electro-plating apparatus according to an Embodiment, includes a holder, a plating bath, a supply tank, a nitrogen gas supply unit, and a current supply device. The holder is configured to hold a substrate to be plated. An anode member is arranged in the plating bath. The supply tank is configured to supply a plating solution being bubbled by a nitrogen gas to the plating bath. The nitrogen gas supply unit is configured to supply the nitrogen gas into the supply tank. The current supply device is configured to pass a current between the substrate to be plated and the anode member.
In the first embodiment, a case where a Cu damascene wire is formed in an insulating layer of a low-k film will be described below using the drawings.
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In the first embodiment, N2 bubbling is performed before plating is started in the next process, that is, the electro-plating process (S114), to prevent the seed film 250 from disappearing after being dissolved by a plating solution, and electro-plating is performed by using the plating solution with which N2 bubbling has been performed at least until the plating is started (the passage of electric current for electro-plating is started).
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Then, a damascene wire is formed by removing, using CMP, the Cu film 260 and the barrier metal film 240 that are deposited on the opening 150 and excessive from the above state.
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The reason why the rate of dissolution of Cu can be reduced by performing N2 bubbling is considered to be because Cu dissolution in the plating solution occurs according to the following reaction formula:
Cu+O2+2H+→Cu2++H2O
Cu reacts with dissolved oxygen and acid in the plating solution to elute into the plating solution. Dissolved oxygen in the plating solution is expelled by performing N2 bubbling so that the amount of reaction of the above reaction formula decreases. Accordingly, elution of Cu into the plating solution can be considered to have decreased.
When electro-plating is performed, the seed film 250 may further be put into the plating bath 650 filled with the plating solution 670 in a state in which a voltage is applied to the seed film 250 from the current supply device 612 while performing N2 bubbling. Particularly in the first embodiment, a voltage lower than a voltage when electro-plating is started after the substrate is soaked in the plating solution 670 is suitably applied to the seed film 250 when the substrate is put into the plating bath 650 filled with the plating solution 670. With this configuration, dissolution of the Cu seed film can further be suppressed.
To completely prevent dissolution of the Cu seed film without performing N2 bubbling, it is necessary to set the voltage at which Cu plating occurs. However, when the substrate is put into the plating bath 650, it takes a predetermined time before the whole surface of the substrate 200 comes into contact with the plating solution 670 and the plating time is different between a portion that comes into contact with the solution first and a portion that comes into contact last, resulting in degradation in embedding uniformity of the Cu film 260 grown as plating on the surface of the substrate 200. Moreover, if the voltage applied to the substrate 200 is decreased without performing N2 bubbling, incomplete plating or defects occur on the side wall where the Cu seed film is thin. Therefore, in the first embodiment, a voltage lower than a voltage when electro-plating is started after the substrate is put into the plating bath 650 filled with the plating solution 670 is applied to the seed film 250 when the substrate is soaked in the plating solution 670 while performing N2 bubbling. Accordingly, dissolution of the Cu layer can be suppressed while maintaining embedding uniformity.
Second EmbodimentIn the second embodiment, a case where, in addition to content in the first embodiment, the substrate is further cooled will be described below using the drawings.
The seed film 250 is cooled as the cooling process (S112). The rear surface of the substrate 200 is cooled by using a gas as a cooling method to cool the seed film 250 via the rear surface of the substrate 200.
It is preferable that the substrate be cooled to a temperature cooler than the temperature of the plating solution 670 by 10° C. or more. If, for example, the temperature of the plating solution 670 is 25° C., the substrate temperature may be controlled to a range between a temperature at which condensation of the substrate 200 is not caused (for example, 5° C.) and 15° C. If the rate of dissolution of the seed film 250 in the plating solution 670 at 25° C. is 100%, the rate of dissolution of the seed film 250 in the plating solution 670 can be suppressed to 56% by cooling the substrate temperature to 15° C. If the substrate temperature is cooled to 5° C., the rate of dissolution of the seed film 250 in the plating solution 670 can be suppressed to about 30%. That is, by cooling the substrate temperature to 15° C. or below, the rate of dissolution can be reduced to almost the half. The cooling position is preferably as close to the plating solution 670 as possible. By making the cooling position as close to the plating solution 670 as possible, the time necessary for the substrate 200 to come into contact with the plating solution 670 after the cooling can be reduced to maintain the cooling effect.
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When electro-plating is performed, the cooled seed film 250 may further be put into the plating bath 650 filled with the plating solution 670 (soaked into the plating solution 670 from outside the plating solution 670) in a state in which a voltage is applied to the seed film 250 from the current supply device 612 while performing N2 bubbling. As described above, a voltage lower than a voltage when electro-plating is started after the substrate is put into the plating bath 650 filled with the plating solution 670 is suitably applied to the seed film 250 when the substrate is soaked in the plating solution 670 (soaked into the plating solution 670 from outside the plating solution 670).
Thus, as described above, by cooling the substrate in addition to N2 bubbling for the plating solution 670, when the surface of the substrate 200 is put into the plating bath 650, dissolution of the seed film 250 can further be suppressed.
Third EmbodimentIn the second embodiment, before the substrate 200 is put into the plating bath 650, for example, the substrate 200 is cooled in the standby position shown in
According to the above embodiments, as described above, occurrences of incompletely plated films after electro-plating and defects can be reduced while suppressing dissolution of a seed film.
In the foregoing, the embodiments have been described with reference to concrete examples. However, the embodiments are not limited to such concrete examples. In the above embodiments, the low-k film 220 is used as a dielectric film, but the dielectric film is not limited to the low-k film 220 and other insulating materials may also be used. For example, a silicon oxide (SiO2) film may be used. The rear surface of the substrate 200 may indirectly be cooled, instead of cooling directly. The embodiments describe a damascene wire, but a dual damascene wire can also achieve similar effects. Particularly, the embodiments are suitable for Cu embedding in a via hole in dual damascene wire formation. In the above examples, the N2 gas supplied from the N2 tank 620 is branched to the holder 652 side and the supply tank 610 of the plating solution, but the embodiments are not limited to such examples. For example, the N2 gas after being supplied to the holder 652 side and discharged from the holder 652 may be supplied to the supply tank 610 for N2 bubbling.
Concerning the thickness of inter-level dielectrics and the size, shape, number and the like of openings, what is needed for semiconductor integrated circuits and various semiconductor elements can be selected and used as appropriate.
In addition, methods for fabricating an electronic component represented by all methods for fabricating a semiconductor device including the elements of the embodiments and obtainable by arbitrarily changing the design by a person skilled in the art are included in the scope of the embodiments.
While techniques normally used in the semiconductor industry such as a photolithography process and cleaning before and after treatment are not described for convenience of description, it is needless to say that such techniques are included in the scope of the embodiments.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and devices described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods and devices described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Claims
1. A method for fabricating an electronic component, comprising:
- forming a seed film above a substrate; and
- performing electro-plating by soaking the seed film in a plating solution in a plating bath to which the plating solution being bubbled by a nitrogen gas is supplied, using the seed film as a cathode.
2. The method according to claim 1, further comprising:
- cooling the seed film by supplying a nitrogen gas to a rear surface of the substrate from a same supply source as the nitrogen gas used for a bubbling.
3. The method according to claim 2, wherein the nitrogen gas after being supplied to the rear surface of the substrate is used for the bubbling of the plating solution.
4. The method according to claim 1, wherein when the electro-plating is performed, the seed film is soaked in the plating solution from outside the plating solution in a state in which a voltage is applied to the seed film.
5. The method according to claim 1, wherein a voltage lower than a voltage when the electro-plating is started after the seed film is soaked in the plating solution is applied to the seed film when the seed film is soaked in the plating solution from outside the plating solution.
6. The method according to claim 1, wherein the seed film is formed by using copper (Cu).
7. The method according to claim 1, wherein the plating solution supplied to the plating bath continues to be bubbled by the nitrogen gas since before the electro-plating is started at least until when the electro-plating is started.
8. The method according to claim 1, wherein the plating solution supplied to the plating bath continues to be bubbled by the nitrogen gas since before the electro-plating is started until the electro-plating is completed.
9. The method according to claim 1, further comprising:
- bubbling the plating solution inside a supply tank by the nitrogen gas; and
- supplying the plating solution that continues to be bubbled inside the supply tank to the plating bath.
10. The method according to claim 9, wherein the plating solution that continues to be bubbled inside the supply tank circulates through the supply tank and the plating bath since before the electro-plating is started until the electro-plating is completed.
11. The method according to claim 9, wherein a portion of the plating solution overflowing from the plating bath is bubbled inside the supply tank by the nitrogen gas and then supplied to the plating bath again.
12. An electro-plating apparatus, comprising:
- a holder configured to hold a substrate to be plated;
- a plating bath in which an anode member is arranged;
- a supply tank configured to supply a plating solution being bubbled by a nitrogen gas to the plating bath;
- a nitrogen gas supply unit configured to supply the nitrogen gas into the supply tank; and
- a current supply device configured to pass a current between the substrate to be plated and the anode member.
13. The apparatus according to claim 12, wherein the holder has a channel, through which a nitrogen gas supplied from the nitrogen gas supply unit passes while the substrate to be plated is held, formed in a rear surface side of the substrate held.
14. The apparatus according to claim 13, wherein the rear surface of the substrate to be plated is cooled by the nitrogen gas being passed through the channel.
15. The apparatus according to claim 12, wherein a seed film is formed on the substrate to be plated, and the seed film is soaked into the plating solution from outside the plating solution by the holder in a state in which a voltage is applied to the seed film by the current supply device.
16. The apparatus according to claim 15, wherein the current supply device applies a voltage, lower than the voltage when electro-plating is started after the seed film is soaked in the plating solution, to the seed film when the seed film is soaked into the plating solution from outside the plating solution.
17. The apparatus according to claim 15, wherein the nitrogen gas supply unit is controlled to continue to supply the nitrogen gas into the supply tank since before the seed film is soaked in the plating solution at least until when electro-plating is started.
18. The apparatus according to claim 15, wherein the nitrogen gas supply unit is controlled to continue to supply the nitrogen gas into the supply tank since before the seed film is soaked in the plating solution until the electro-plating is completed.
19. The apparatus according to claim 12, further comprising:
- a mechanism configured to cause the plating solution continuing to be bubbled by the nitrogen gas inside the supply tank to circulate between the supply tank and the plating bath since before electro-plating is started until the electro-plating is completed.
20. The apparatus according to claim 19, wherein a portion of the plating solution overflowing from the plating bath is bubbled inside the supply tank by the nitrogen gas and then supplied to the plating bath again.
Type: Application
Filed: Mar 17, 2011
Publication Date: Dec 8, 2011
Inventors: Toshiyuki MORITA (Mie), Satoshi Wakatsuki (Kanagawa)
Application Number: 13/050,454
International Classification: C23C 28/02 (20060101); C25B 9/00 (20060101); C25B 15/08 (20060101); C25B 15/00 (20060101);