Aqueous dispersion for chemical mechanical polishing

Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means

Reexamination Certificate

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C051S306000, C051S307000

Reexamination Certificate

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06559056

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to an aqueous dispersion for chemical mechanical polishing. More specifically, it relates to an aqueous dispersion for chemical mechanical polishing that is particularly useful for chemical mechanical polishing of insulating films during the manufacturing steps for semiconductor devices.
Improvements in degrees of semiconductor device integration and increased multilayer wiring have led to drastic increases in storage volumes of memory devices. This has been supported by advances in micronization for the working techniques, increased multilayer wiring and the steps for micronization are increasing correspondingly, thus leading to higher chip costs. Given such circumstances, chemical mechanical polishing techniques for polishing of working film and the like been introduced and attention is being directed toward these techniques. Application of such chemical mechanical polishing techniques has allowed planarization and numerous micronization techniques.
One of these micronization techniques is Shallow Trench Isolation, also known as STI. The important factor for the STI technique is the removal rate ratio between the silicon nitride film used as the stopper film and the silicon oxide film, or the “selectivity”, and an optimum polishing agent is necessary.
SUMMARY OF THE INVENTION
In light of the state of the aforementioned STI technique, it is an object of the present invention to provide an aqueous dispersion for chemical mechanical polishing with a high removal rate for silicon oxide film and a low removal rate for silicon nitride film, i.e. a high selectivity.
The present invention is as follows.
1. An aqueous dispersion for chemical mechanical polishing characterized by comprising an inorganic abrasive and organic particles with anionic group, wherein the removal rate for silicon oxide film is at least 5 times the removal rate for silicon nitride film.
2. An aqueous dispersion for chemical mechanical polishing according to 1. above, wherein the abovementioned anionic group is at least one selected from among carboxyl group, hydroxyl group, sulfuric acid ester group, sulfonic acid group, phosphoric acid group and epoxy group.
3. An aqueous dispersion for chemical mechanical polishing according to 2. above, wherein the abovementioned inorganic abrasive is at least one selected from the group consisting of silica, ceria, alumina, titania and zirconia.
4. An aqueous dispersion for chemical mechanical polishing according to 3. above, wherein the zeta potential of the abovementioned organic particles with the abovementioned anionic group is −10 mV or lower.
5. An aqueous dispersion for chemical mechanical polishing according to 2. above, wherein the abovementioned inorganic abrasive is fumed silica or colloidal silica.
6. An aqueous dispersion for chemical mechanical polishing according to 5. above, wherein the zeta potential of the abovementioned organic particles with the abovementioned anionic group is −10 mV or lower.
7. An aqueous dispersion for chemical mechanical polishing according to 6. above, wherein the zeta potential of the abovementioned organic particles with the abovementioned anionic group is −20 mV or lower.
8. An aqueous dispersion for chemical mechanical polishing according to 7. above, which is used for a shallow trench isolation step in the manufacture of a semiconductor device.
9. An aqueous dispersion for chemical mechanical polishing according to 1. above, which further comprises an anionic surfactant, wherein when the abovementioned inorganic abrasive is silica, the removal rate for silicon oxide film is at least 6 times the removal rate for silicon nitride film.
10. An aqueous dispersion for chemical mechanical polishing according to 9. above, wherein the abovementioned anionic group is at least one selected from among carboxyl group, hydroxyl group, sulfuric acid ester group, sulfonic acid group, phosphoric acid group and epoxy group.
11. An aqueous dispersion for chemical mechanical polishing according to 10. above, wherein the zeta potential of the abovementioned organic particles with the abovementioned anionic group is −10 mV or lower.
12. An aqueous dispersion for chemical mechanical polishing according to 11. above, which is used for a shallow trench isolation step in the manufacture of a semiconductor device.
13. An aqueous dispersion for chemical mechanical polishing according to 1. above, which further comprises an anionic surfactant, wherein when the abovementioned inorganic abrasive is ceria, the removal rate for silicon oxide film is at least 10 times the removal rate for silicon nitride film.
14. An aqueous dispersion for chemical mechanical polishing according to 13. above, wherein the abovementioned anionic group is at least one selected from among carboxyl group, hydroxyl group, sulfuric acid ester group, sulfonic acid group, phosphoric acid group and epoxy group.
15. An aqueous dispersion for chemical mechanical polishing according to 14. above, wherein the zeta potential of the abovementioned organic particles with the abovementioned anionic group is −10 mV or lower.
16. An aqueous dispersion for chemical mechanical polishing according to 15. above, which is used for a shallow trench isolation step in the manufacture of a semiconductor device.
According to the invention, it is possible to obtain an aqueous dispersion for chemical mechanical polishing which is useful for STI steps, to allow polishing of silicon oxide film at an adequate rate while maintaining an adequately high selectivity as the ratio with respect to the removal rate for silicon nitride film, and without producing scratching or dishing.
DETAILED DESCRIPTION OF THE INVENTION
The aqueous dispersion for chemical mechanical polishing of the invention is characterized by comprising an inorganic abrasive and organic particles with anionic group, wherein the removal rate for silicon oxide film is at least 5 times the removal rate for silicon nitride film.
The “inorganic abrasive” may be silica, ceria, alumina, titania, zirconia or the like, and particularly preferred are silica and ceria. The silica used may be (1) fumed silica obtained by reacting silicon chloride in the presence of hydrogen and oxygen, (2) colloidal silica obtained by ion-exchange of a silicic acid salt, or (3) colloidal silica obtained by hydrolysis or condensation of a metal alkoxide. The ceria used may be obtained by firing of cerium carbonate, cerium hydroxide or cerium oxalate, but ceria obtained by firing of cerium carbonate is particularly preferred. The inorganic abrasive used may be of a single type, but combinations of two or more, such as silica and ceria, silica and alumina or ceria and alumina may also be used.
The average particle size of the inorganic abrasive is preferably 0.01-3 &mgr;m, because when the average particle size is less than 0.01 &mgr;m it is not possible to obtain an aqueous dispersion with an adequately high removal rate. On the other hand, if the average particle size is greater than 3 &mgr;m, the inorganic abrasive settles and easily separates, thus making it difficult to achieve a stable aqueous dispersion. The average particle size is more preferably 0.02-1.0 &mgr;m, and even more preferably 0.04-0.7 &mgr;m. An inorganic abrasive with an average particle size within this range gives a stable aqueous dispersion for chemical mechanical polishing with a high removal rate, and minimal settling or separation of the abrasive. The average particle size can be measured with a dynamic light scattering type measuring instrument, a laser diffusion diffraction type measuring instrument or the like, or it may be measured by observation with a transmission electron microscope. It may also be calculated based on the specific surface area of the powdered inorganic abrasive.
The content of the inorganic abrasive in the aqueous dispersion will depend on the type of inorganic abrasive, but for silica it may be 2-20 parts by weight (hereunder referred to as “parts”), preferably 4-15 parts and more prefera

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