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  Method of manufacturing abrasive compositionUSPTO Application #: 20060240748Title: Method of manufacturing abrasive composition Abstract: A process for producing a polishing composition excelling in dispersion stability wherein the amount of agglomerated particles is reduced. In step 1-1 thereof, ultrapure water is adjusted so as to have a pH value of 1.0 to 2.7. Under shearing force given by a high shear disperser, fumed silica powder of 50 to 200 m2/g specific surface area is charged therein until an initial silica concentration of 46 to 54 wt %, and the high shear disperser is operated so as to apply shearing force for 1 to 5 hours. In step 1-2, a small amount of ultrapure water is added to the silica dispersion so as to realize a silica concentration of 45 to 53 wt % and shearing force is applied for 10 to 40 minutes. In step 1-3, ultrapure water is added to the silica dispersion so as to realize a silica concentration of 33 to 44 wt % and shearing force is applied for 0.5 to 4 hours. In step 2-1, the silica dispersion is added to an aqueous basic substance solution prepared so that a pH value after mixing is in a range of 8 to 12 and so that silica concentration is in a range of 10 to 30 wt %. (end of abstract) Agent: Harness, Dickey & Pierce, P.L.C - Reston, VA, US Inventors: Yoshiharu Ohta, Yasuyuki Itai, Keiji Fukuda USPTO Applicaton #: 20060240748 - Class: 451041000 (USPTO) Related Patent Categories: Abrading, Abrading Process, Glass Or Stone Abrading The Patent Description & Claims data below is from USPTO Patent Application 20060240748. Brief Patent Description - Full Patent Description - Patent Application Claims
TECHNICAL FIELD [0001] The present invention relates to a method of manufacturing an abrasive composition for use in a polishing step of semiconductor manufacturing processes. BACKGROUND ART [0002] In a field of manufacturing semiconductors, the planarization technique for semiconductor and metal layers is becoming an important constituent technology as semiconductor devices scale down and become more and more multilayered. When an integrated circuit is formed in a wafer, stacking layers without planarizing irregularities owing to electrode wiring, etc. will enlarge elevation changes and therefore worsen the planarity extremely. Also, enlarged elevation changes make it difficult to focus on both the reentrants and protrusions in lithography, thus making it impossible to realize scaling down. Therefore, there is a need to perform a planarization process for removing irregularities on a wafer surface at an appropriate stage of sacking. Such planarization process may be an etch-back method by which portions of irregularities are removed by etching, a film-growing method by which a planar film is formed by plasma CVD (Chemical Vapor Deposition), etc., a fluidizing method by which planarization is practiced by a thermal treatment, and a selective growing method by which reentrants are embedded by selective CVD etc. [0003] The above methods have problems in that: whether or not they can be adopted depends on the kind of films, such as an insulating film or a metal film; and the area which can be planarized by them is remarkably small. As a technique for planarization process that enables these problems to be overcome, there is planarization by CMP. [0004] In planarization process by CMP, a polish pad pressed against a silicon wafer is relatively moved to polish a surface thereof while a slurry with fine particles (whet grains) suspended therein is supplied onto a surface of the polish pad, whereby a widespread range of the wafer surface can be planarized with high precision. [0005] A CMP apparatus for planarization by CMP is mainly constructed of: a rotary platen section; a carrier section; a slurry-supply section; and a dressing section. The rotary platen section has a top face on which a polish pad is stuck by an adhesive tape or the like, and a bottom face connected with a rotation-drive mechanism through a rotating shaft. The carrier section holds a silicon wafer on its bottom face, an object to be polished, by a backing material and a retainer ring, and brings a processed face of the silicon wafer into press-contact with the polish pad. the carrier section is connected with the rotation-drive mechanism through the rotating shaft on the side of the top face thereof. [0006] The slurry-supply section supplies the surface of the polish pad with a slurry with particles of silica, ceria, alumina, etc. suspended in a medium. The dressing section includes a plate with industrial diamond particles electrodeposited thereon, and razes a portion on which polishing waste, etc. are deposited thereby to restore the surface of the polish pad degraded in polish property. [0007] The CMP apparatus forces the rotation-drive mechanism to rotate the rotary platen section and carrier section in parallel with supplying a slurry to a substantially central portion of the polish pad and causing relative movement of the silicon wafer and polish pad, and thereby polishes the processed face of a silicon wafer. [0008] In recent years, with scaling down of the design rule for IC (Integrated Circuit) chips, a microscratch ascribable to a slurry that appears on a polished surface of a silicon wafer has presented a problem. What can be considered to be a factor of such microscratch is an agglomerate of whet grains suspended in a medium or a bulky particle existing as a dispersion-failed material. [0009] As a raw material of silica slurry, fumed silica or colloidal silica is used. Fumed silica allows a silica slurry with less impurities to be produced because of its higher purity in comparison to colloidal silica. However, it is hard to highly disperse it in a medium because of its high agglomerate property. [0010] As a conventional method of manufacturing a silica slurry that aims at enhancing the dispersion stability of fumed silica, there are methods described in Japanese Examined Patent Publications JP-B2 2,935,125 and 2,949,633, and Japanese Unexamined Patent Publication JP-A 2001-26771. With any of the methods, the realization of stable dispersibility is attempted by specifying a shearing condition, the concentration of silica, etc. [0011] While a silica slurry was made using fumed silica as a raw material by the manufacturing method described in the above-describe patent documents in fact, the ability of silica to disperse was insufficient and lots of agglomerates were present in the slurry. DISCLOSURE OF INVENTION [0012] It is an object of the invention to provide a method of manufacturing an abrasive composition that is superior in dispersion stability in which fewer agglomerated particles are produced. [0013] The invention is a method of manufacturing an abrasive composition comprising: [0014] a first step of preparing an acid fumed silica dispersion; and [0015] a second step of adding the fumed silica dispersion to an aqueous basic substance solution which is prepared so that the abrasive composition to be obtained after the end of mixing with the fumed silica dispersion has predetermined pH and silica concentration, and mixing the fumed silica dispersion and the aqueous solution. [0016] In addition, the invention is characterized in that the aqueous basic substance solution is prepared so that the abrasive composition has a pH of 8 to 12 and a silica concentration of 10 to 30 wt %. [0017] Also, the invention is characterized in that the fumed silica has a relative surface area of 50 to 200 m.sup.2/g. [0018] Further, the invention is characterized in that the aqueous basic substance solution contains at least any of ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide or magnesium hydroxide. [0019] According to the invention, first of all, an acid fumed silica dispersion is prepared in the first step. Incidentally, it is desirable that the relative surface area of the fumed silica to be used is 50 to 200 m.sup.2/g. [0020] Then, in the second step, an aqueous basic substance solution is prepared. The aqueous basic substance solution is controlled in concentration and volume by mixing with the fumed silica dispersion prepared in the first step so that the intended abrasive composition has a pH of 8 to 12 and a silica concentration of 10 to 30 wt %. The aqueous basic substance solution contains at least any of ammonium hydroxide, sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide or magnesium hydroxide. [0021] While an aqueous basic substance solution is added to a fumed silica dispersion according to the conventional manufacturing method, a fumed silica dispersion is added to an aqueous basic substance solution that has been prepared according to the invention. Continue reading... Full patent description for Method of manufacturing abrasive composition Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of manufacturing abrasive composition patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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