Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
2002-02-28
2004-04-27
Eley, Timothy V. (Department: 3724)
Abrading
Abrading process
Utilizing fluent abradant
C451S041000, C451S059000, C451S063000, C451S550000, C051S308000, C051S309000
Reexamination Certificate
active
06726534
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention provides chemical mechanical polishing systems and methods for their use in polishing.
BACKGROUND OF THE INVENTION
In the course of manufacturing integrated circuits, it is generally necessary to polish or planarize the surfaces of semiconductor wafers. Such mechanical treatment may be done to remove high topography, surface defects, scratches, roughness, or embedded particles. A chemical slurry can be used to carry out this process. Polishing with a slurry is called chemical-mechanical planarization (CMP).
In a typical CMP process, a wafer is pressed against a polishing pad in the presence of a slurry under controlled chemical, pressure, velocity, and temperature conditions. The slurry generally contains small, abrasive particles that abrade the surface of the wafer in a mixture with chemicals that etch and/or oxidize the newly formed surface of the wafer. The polishing pad is generally a planar pad made from a continuous phase matrix material such as polyurethane. Thus, when the pad and/or the wafer move with respect to each other, material is removed from the surface of the wafer mechanically by the abrasive particles and chemically by the etchants and/or oxidants in the slurry.
CMP slurries are typically prepared and stored for extended periods before use in polishing a substrate. Under these conditions the chemical components typically reach a chemical equilibrium with the abrasive. However, polishing substrate surfaces with equilibrium CMP mixtures is not always the optimal method, especially when the chemical components are reactive with both the wafer surface and the abrasive particles and reaction with the substrate surface provides advantageous polishing characteristics. This is because the reaction of the chemical component with the abrasive particle surface prior to polishing lowers the concentration of that component available for reaction with the substrate surface during polishing. Consequently, the polishing performance of certain equilibrium CMP slurries is not optimal for the polishing of solid surfaces, including integrated circuit wafer surfaces, memory or rigid disk surfaces, glass surfaces, magnetic media, etc. Furthermore, because CMP slurries must be stable for the extended periods over which they are typically stored before use, the chemical additives available for use in slurries is limited by their reactivity with slurry components, particularly the abrasive. This consideration also limits the concentration of certain additives that can be incorporated into slurries.
Thus, methods are needed to improve CMP slurry performance that can increase the potential advantages achievable by the reaction of chemical components with substrate surfaces and which minimize the disadvantages arising from the reactivity of those components within CMP slurries. The present invention provides such a method. These and other advantages of the present invention, as well as additional inventive features, will be apparent from the description of the invention provided herein.
BRIEF SUMMARY OF THE INVENTION
The invention provides a polishing system that comprises a liquid carrier, an alkali metal ion, hydroxide ions, and a polishing pad and/or an abrasive. When an abrasive is used, it can be dispersed in the liquid carrier of the polishing system or bound to the polishing pad. The alkali metal ion can be any univalent group I metal ion and is present in the polishing system at a concentration of about 0.05 molar (M) or more. Hydroxide ions are present in a sufficient amount to provide the system with a pH of about 9 or more. The liquid carrier of the polishing system can be any suitable polar solvent, such as water. The invention further provides a polishing method that involves polishing a portion of a substrate with the polishing system beginning about 6 hours or less after the polishing system is prepared.
DETAILED DESCRIPTION OF THE INVENTION
The invention provides a polishing system and method for polishing a substrate. The polishing system comprises, consists essentially of, or consists of (a) a liquid carrier, (b) an alkali metal ion at a concentration of about 0.05 M or more, (c) hydroxide ions sufficient to provide the polishing system with a pH of about 9 or more, and (d) a polishing pad and/or an abrasive. The polishing method involves contacting a surface of a substrate with such a polishing system, particularly a polishing system comprising (a) a liquid carrier, (b) an alkali metal ion at a concentration of about 0.05 M or more, (c) hydroxide ions sufficient to provide the polishing system with a pH of about 9 or more, and (d) a polishing pad and/or an abrasive, and polishing at least a portion of the substrate before the polishing system components reach a chemical equilibrium after the system is prepared.
Typically, the polishing system is used about 6 hours or less after the polishing system is prepared, which generally will be before the polishing system reaches chemical equilibrium. Preferably, the polishing system is used about 4 hours or less (e.g., about 2 hours or less, about 1 hour or less, about 30 minutes or less, about 10 minutes or less, about 5 minutes or less, or even about 1 minute or less) after the polishing system is prepared. Indeed, the polishing system can be used seconds (e.g., about 30 seconds or less, or about 10 seconds or less) after the polishing system is prepared, such as when the polishing system components are mixed very near or at the point-of-use of the polishing system (e.g., on the polishing pad and/or substrate being polished).
The term“component” as used herein includes individual ingredients (e.g., acids, bases, oxidizers, water, etc.) as well as any combination of ingredients (e.g., aqueous compositions, abrasive slurries, mixtures and solutions of oxidizers, acids, bases, complexing agents, etc.) that are stored separately and combined to form a polishing system.
The invention can be used to polish any suitable substrate. Suitable substrates are typically wafers used in the semiconductor industry that are in need of polishing or planarizing. They comprise, for example, a metal, metal oxide, metal composite, metal alloy, or mixtures thereof. The substrate can comprise metals such as copper, aluminum, titanium, tungsten, gold, and combinations (e.g., alloys or mixtures) thereof. The substrate also can comprise metal oxides such as alumina, silica, titania, ceria, zirconia, germania, magnesia, and co-formed products thereof, and mixtures thereof. In addition, the substrate can comprise metal composites and/or alloys such as metal nitrides (e.g., silicon nitride, tantalum nitride, titanium nitride, and tungsten nitride), metal carbides (e.g., silicon carbide and tungsten carbide), nickel-phosphorus, alumino-borosilicate, borosilicate glass, phosphosilicate glass (PSG), borophosphosilicate glass (BPSG), silicon-germanium alloys, and silicon-germanium-carbon alloys. The substrate also can comprise semiconductor base materials such as single-crystal silicon, polycrystalline silicon, amorphous silicon, silicon-on-insulator, and gallium arsenide. The substrate also can comprise a low dielectric resin, such as a nanoporous siloxane resin formed from an alkylhydridosiloxane, a doped silicon oxide, such as boron, carbon, or halogen-doped silicon oxide, or such other low dielectric resins as are known, such as BLACK DIAMOND, manufactured by Applied Materials, CORAL, manufactured by Novellus Systems, Inc., and SILK, manufactured by Dow. Substrate materials can be porous or nonporous, as desired. The invention is not limited to semiconductor polishing. It can also be applied to glass substrates, including technical glass, optical glass, and ceramics, of various types known in the art.
The invention can be used to polish any part of a substrate (e.g., a semiconductor device) at any stage in the production of the substrate. For example, a particularly effective use of certain polishing systems of the invention is in polishing a semiconductor device in conjunction with shallow trench
Bogush Gregory H.
Chamberlain Jeffrey P.
Feeney Paul M.
Mueller Brian L.
Schroeder David J.
Cabot Microelectronics Corporation
Eley Timothy V.
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