Semiconductor device manufacturing: process – Chemical etching – Combined with the removal of material by nonchemical means
Reexamination Certificate
1997-12-30
2002-07-16
Sherry, Michael J. (Department: 2829)
Semiconductor device manufacturing: process
Chemical etching
Combined with the removal of material by nonchemical means
C051S307000, C216S089000, C438S633000, C438S692000
Reexamination Certificate
active
06420269
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a cerium oxide abrasive, a method for producing the cerium oxide abrasive, a method for polishing substrates, a method for producing semiconductor chips, a semiconductor chip, a method for producing semiconductor devices, and a semiconductor device.
BACKGROUND ART
With the recent noticeable increase In the density and the degree of integration of ultra-LSIs, which requires multi-layered structures of aluminium wiring and fine wiring patterns, it is desired to reduce the minimum line width of wiring patterns to be processed. Therefore, for the interlayer insulating films to be in those LSIs, required is a flattening technique of flattening their surfaces with the films filling up in the distance between the adjacent fine wiring lines with no empty space therebetween.
In general, such interlayer insulating films which needs to be flattened are formed through vapor deposition such as plasma CVD or ECR-CVD, or through coating such as SOG. Of those, SOG comprises applying a coating liquid that is prepared by hydrolyzing an alkoxysilane and an alkylalkoxysilane with water and a catalyst in an organic solvent such as an alcohol, onto a substrate through spin coating, followed by curing it through heat treatment, and the thus-coated film is then flattened. For this, for example, mainly employed Is an organic SOG film which contains the organic component (e.g., alkyl group) remaining therein in order to be thick without being cracked. The organic SOG film is advantageous in that its volume is shrunk little when it is cured, that it is hydrophobic and that its dielectric constant is low. However, the organic SOG film is not satisfactorily applicable to global flattening of uneven surfaces caused by complicated sparse and dense wiring, though being applicable to local flattening of a part of such uneven surfaces.
As the material for forming the interlayer insulating films, silicon-free, organic polymer resins with good insulation performance and adhesiveness are being tried. For example, a coating liquid as prepared by dissolving such a silicon-free, organic polymer resin in an organic solvent such as an alcohol is applied onto a substrate through spin coating, and thereafter heated to form an insulating film on the substrate. This method produces thick insulating films relatively with ease.
Multi-layered wiring structures are much used In ultra-LSIs in order to make them have a higher density and a higher degree of integration. In particular, current logic LSI devices have four-layered or higher poly-layered structures, in which, therefore, the difference in surface level is increasing. On the other hand, the focal depth of resists to be used for patterning of wiring in those devices is being reduced with the reduction in the wiring width of the patterns, and such a high difference in surface level in those fine patterns is problematic. In order to solve this problem, it is desired to globally flatten the fine patterns. As one method for this, it is expected to apply to the fine patterns a chemical mechanical polishing (CMP) technique which has heretofore been used for polishing Si wafers and which produces a synergistic effect of the chemical polishing action and the mechanical polishing action.
Of insulating films, those formed through CVD could be relatively easily polished with an abrasive slurry comprising a dispersion of colloidal silica, which has heretofore been used in polishing Si wafers. However, CVD is problematic in that grooves with a high aspect ratio to be between fine lines of wiring patterns are poorly filled up through CVD, and it is said that CVD is limitedly applicable to grooves having an aspect ratio of at most 3 or so. In order to lower the dielectric constant of insulating films, the introduction of fluorine into the films is tried, for which, however, there are still outstanding problems in that the fluorine once introduced into the films is often expelled therefrom and that the hygroscopicity of the films increases.
On the other hand, organic SOG films formed through SOG are advantageous in that even grooves with a high aspect ratio can be well filled up with the films, and it is said that grooves having an aspect ratio of 10 or larger could be filled up therewith. In addition, those organic SOG films have a low dielectric constant of 3 or so in themselves, and the costs for producing the films are lower than those for producing CVD films. However, when the organic SOG films are polished with a colloidal silica-containing abrasive such as that mentioned above, they are often scratched. If they are polished with the abrasive under a mild condition in order to protect them from being scratched, the polishing speed is greatly lowered. In addition, even if polished under the same condition, the polishing speed for the organic SOG films is significantly lower than that for CVD films. Therefore, if the organic SOG films are desired to be used in the art as they are, their costs shall be too high, resulting in that their use in the art is impracticable. Given that situation, it is desired to develop an abrasive capable of polishing those organic SOG films at a high speed.
On the other hand, organic polymer resin films can form thick films having a thickness of 10 &mgr;m or larger in one-pass coating, and it is considered that the films will be effectively usable in global flattening of fine patterns, Those films have a low dielectric constant of 3 or so in themselves, and their dielectric constant may be reduced more if fluorine is introduced thereinto. Acrylate polymer films can be formed with UV rays without being heated. However, since the hardness of those organic polymer resin films is much lower than that of CVD films and organic SOG films, the organic polymer resin films are scratched if polished with a colloidal silica-containing abrasive such as that mentioned above. In order to protect the films from being scratched, if the polishing condition is made mild to such a degree that the films are not scratched, the films could not almost be polished under such a mild condition. Therefore, it is desired to develop an abrasive capable of polishing the organic polymer resin films without scratching them.
DISCLOSURE OF THE INVENTION
The present invention is to provide a cerium oxide abrasive favorably used for polishing insulating films such as organic SOG films and organic polymer resin films which have a low dielectric constant and can be globally flattened and with which even grooves between fine wiring lines can be filled up; a method for producing the cerium oxide abrasive; a method for polishing substrates using the cerium oxide abrasive; a method for producing semiconductor chips using the polishing method; a semiconductor chip; a method for producing semiconductor devices; and a semiconductor device.
Specifically, the invention provides a cerium oxide abrasive for polishing an insulating film formed on a predetermined substrate, which comprises a slurry of cerium oxide grains dispersed in water. Desirably, this slurry comprises 100 parts by weight of a water solvent and not larger than 10 parts by weight of cerium oxide grains dispersed in the solvent. The invention also provides a method for producing the cerium oxide abrasive, which comprises a step of dispersing cerium oxide grains in water to prepare a slurry.
The cerium oxide grains to be used herein are desirably at least any of the following (1) to (11).
(1) Cerium oxide grains as obtained by oxidizing a water-insoluble, tri-valent cerium compound as dispersed in water, with an oxidizing agent.
(2) Cerium oxide grains as obtained by oxidizing a water-insoluble cerium compound, which is obtained from an aqueous solution of a water-soluble, tri-valent cerium compound, with an oxidizing agent.
For those (1) and (2), the oxidizing agent is preferably hydrogen peroxide.
(3) Cerium oxide grains as obtained by neutralizing or alkalifying an aqueous solution of a tetra-valent cerium compound.
(4) Cerium oxide grains having a specific surface area of not smalle
Honma Yoshio
Kurata Yasushi
Matsuzawa Jun
Tanno Kiyohito
Griffin & Szipl, P.C.
Hitachi Chemical Company Ltd.
Sarkar Asok Kumar
Sherry Michael J.
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