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Alumina particles, production process thereof, composition comprising the particles and alumina slurry for polishingRelated Patent Categories: Colloid Systems And Wetting Agents; Subcombinations Thereof; Processes Of, Continuous Liquid Or Supercritical Phase: Colloid Systems; Compositions An Agent For Making Or Stabilizing Colloid Systems; Processes Of Making Or Stabilizing Colloid Systems; Processes Of Preparing The Compositions (e.g., Micelle; Thickening Agent; Protective Colloid Agent; Composition Containing An Emulsifying Agent With No Dispersant Disclosed; Organic Liquid Emulsified In Anhydrous Hf), Aqueous Continuous Liquid Phase And Discontinuous Phase Primarily Solid (e.g., Water Based Suspensions, Dispersions, Or Certain Sols*, Of Natural Or Synthetic Ester-wax, Beeswax, Carnauba Wax; Or Latex Dispersion), The Solid Is Primarily Inorganic Material (e.g., Mercurous Halide), The Material Primarily Contains Compound Containing Both Metal And Oxygen (e.g., Silver Nitrate), The Metal Present In The Greatest Amount Is AluminumAlumina particles, production process thereof, composition comprising the particles and alumina slurry for polishing description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060194885, Alumina particles, production process thereof, composition comprising the particles and alumina slurry for polishing. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS REFERENCE TO RELATED APPLICATIONS [0001] This application is a divisional of U.S. patent application Ser. No. 10/179,268, filed Jun. 26, 2002, which is a continuation-in-part (CIP) application under 35 U.S.C. .sctn.120 of U.S. patent application Ser. No. 09/891,456 filed on Jun. 27, 2001 and PCT/JP00/09231 filed on Dec. 26, 2000 and designating U.S., claiming benefit pursuant to 35 U.S.C. .sctn.119(e)(1) of the filing date of the Provisional Application 60/214,795 filed on Jun. 28, 2000 pursuant to 35 U.S.C. .sctn.111(b). TECHNICAL FIELD [0002] The present invention relates to alumina particles obtained using a gas phase method, a process for producing the alumina particles, and a composition comprising the particles. The alumina particles are obtainable from aluminum chloride by the gas phase method, and are suitable for use as a slurry for polishing. BACKGROUND ART [0003] Aluminum oxide (alumina) has various crystalline forms such as .gamma.-, .delta.-, .theta.-, and .alpha.-forms. The .alpha.-alumina is widely used as a raw material for fine ceramics in most general use. The .gamma.-, .delta.-, and .theta.-aluminas other than the .alpha.-alumina are low-temperature phases of the .alpha.-alumina. They are referred to as transition alumina and used for catalyst carriers, various kinds of fillers, and modifiers for modifying rheological properties. [0004] To produce the transition alumina, there is a process of calcining aluminum hydroxide, aluminum alkoxide, or alum, followed by grinding. Calcination of aluminum hydroxide, aluminum alkoxide, and alum can remove water, alcohol, and ammonium sulfate respectively therefrom, thereby providing alumina. In the above process, the particle properties of the raw material and the calcining conditions strongly influence the primary particle diameter and the secondary particle diameter of alumina obtained as the resulting product. Therefore, in order to control the primary and secondary particle diameters, it is important to pay attention to the properties of the raw particles, specifically, to appropriately select the raw materials. The step of grinding the calcined powder often becomes indispensable for regulating the particle size. [0005] Further, as examples of the process for obtaining the transition alumina by synthesizing a raw material in a liquid phase and calcining the raw material, the following processes are known: a process for obtaining .gamma.-alumina by preparing basic aluminum ammonium carbonate in a liquid phase and calcining the basic aluminum ammonium carbonate (Japanese Laid-Open Patent Application No. 11-228132); a process of gelling a basic aluminum chloride aqueous solution by pH adjustment and sintering the resulting gelled product (Japanese Laid-Open Patent Application No. 11-228131); and a process of sintering and grinding hydrated alumina with a boehmite structure (Japanese Laid-Open Patent Application No. 11-268911). [0006] In addition to the above, there is a process for obtaining the transition alumina by a gas phase method, for example, a process for obtaining an ultrafine oxide by melting and vaporizing a metal in a vacuum vessel, and introducing the vaporized metal into an oxidizing atmosphere; a process of evaporating and oxidizing a metal aluminum powder in an oxygen-containing flame (Japanese Patent Publication No. 5-53722); and a process of ejecting a metal halide represented by anhydrous aluminum chloride into a burner flame to oxidize the same (Japanese Laid-Open Patent Application No. 8-197414). The transition alumina particles produced by such gas phase methods have a lower aggregation degree as compared with those of transition alumina produced through a liquid phase, or have a nearly spherical shape and are in almost a monodispersed state. [0007] Recently, there has been a tendency for more and more increase in the degree of integration of circuits provided on a semiconductor substrate. The technique of chemical mechanical polishing (CMP) is attracting special attention as a method for increasing the degree of integration. In this technique, circuit formation on a substrate and smoothing of the substrate by polishing are alternately carried out to make a multi-layered circuit, thereby increasing the degree of integration. A slurry used for the CMP comprises an aqueous solvent of which the liquid properties are adjusted with an oxidizing metallic salt, a surfactant or the like, and inorganic particles uniformly suspended in the solvent. The aqueous solvent chemically reacts with the surface subjected to polishing, and the compounds present on the surface subjected to polishing are scraped away by the mechanical abrasiveness of the inorganic particles. Therefore, the inorganic particles are required to efficiently work to scrape away the compounds with a measure of hardness and to include neither coarse particles nor particles with extremely high hardness, as both types of particles would cause scratches on the surface subjected to polishing. [0008] The transition alumina prepared through the sintering step includes a large number of coarse particles. It is difficult to decrease the number of coarse particles in order to cope with the CMP even if grinding is insistently conducted. Further, variance in sintering in the particles is unavoidable, and it is therefore highly probable that particles with high hardness are mixed in. Meanwhile, when the particles produced by the gas phase method are spherical or nearly spherical, the frictional force of the particles against the surface subjected to polishing becomes low and, consequently, the abrasiveness is decreased. In order to improve the abrasiveness, it is better for the primary particles or secondary particles to be large. However, scattering in the particle size distribution is unavoidable in light of the properties of the particles, so that no particles with a completely uniform particle size exist. On this account, with the increase in size of the primary particles or the secondary particles, the probability that coarse particles are contained is drastically increased, with the result that the occurrence of scratches becomes frequent. The above-mentioned Japanese Laid-Open Patent Application No. 8-197414 discloses fumed alumina produced by a gas phase method. However, the previously mentioned points are not taken into consideration, and the production process is not disclosed. SUMMARY OF THE INVENTION [0009] The object of the present invention is to provide alumina particles with excellent abrasiveness, containing small amounts of coarse particles to such a degree that the alumina particles are suitable as abrasive grains for CMP, a process for producing the alumina particles, and a composition and an alumina slurry for polishing, each comprising the alumina particles. [0010] The present inventors have intensively studied and succeeded in obtaining alumina particles capable of solving the above-mentioned problems by controlling the manufacturing conditions such as mixing of gases and the reaction temperature in the production process of alumina where aluminum chloride serving as a raw material is vaporized and thereafter allowed to react with an oxidizing gas. [0011] Namely, the present invention basically provides the following: [0012] (1) Alumina particles obtained from aluminum chloride by a gas phase method, the alumina having an amorphous form or being an alumina having a crystalline form of transition alumina, with primary particles thereof having an average particle diameter of approximately 5 to 100 nm, and secondary particles, resulting from the aggregation of the primary particles, having an average particle diameter of approximately 50 to 800 nm. [0013] (2) Alumina particles obtained from aluminum chloride by a gas phase method, the particles having an amorphous form or a .gamma.-, .delta.-, or .theta.- crystalline form or a mixed form thereof, with primary particles thereof having an average particle diameter of approximately 5 to 100 nm, and secondary particles, resulting from the aggregation of the primary particles, having an average particle diameter of approximately 50 to 800 nm. [0014] (3) The alumina particles as described in (1) or (2) above, wherein particles having a particle diameter larger than 45 .mu.m are contained in an amount of about 0.05% by mass or less. [0015] (4) A process for producing alumina particles, comprising vaporizing aluminum chloride and high-temperature oxidizing the vaporized aluminum chloride with an oxidizing gas to produce alumina particles as described in any one of (1) to (3) above. [0016] (5) The process for producing alumina particles as described in (4) above, wherein the aluminum chloride vaporized gas and the oxidizing gas are preheated to 500.degree. C. or more before the high-temperature oxidation. [0017] (6) The process for producing alumina particles as described in any one of (1) to (4) above, wherein the aluminum chloride-containing gas (material gas) and the oxidizing gas are introduced into a reactor each at an ejecting flow velocity of about 10 m/sec or more, the ratio of the flow velocity of oxidizing gas to the flow velocity of material gas is approximately from 0.2 to less than 10, and the amount of oxidizing gas is about 1 or more times the amount of oxidizing gas necessary for stoichiometrically oxidizing aluminum chloride. [0018] (7) The process for producing alumina particles as described in any one of (4) to (6) above, wherein the vaporized aluminum chloride gas contains approximately from 5 to 90% by volume of aluminum chloride. [0019] (8) The process for producing alumina particles as described in any one of (4) to (7) above, wherein the ratio of oxygen to water vapor in the oxidizing gas is from 0 to about 90% by volume of oxygen to from about 10 to 100% by volume of water vapor and the sum total of oxygen and water vapor is from about 10 to 100% by volume. [0020] (9) The process for producing alumina particles as described in any one of (4) to (8) above, wherein the high-temperature oxidation is performed with a reactor residence time of about 1 sec or less. Continue reading about Alumina particles, production process thereof, composition comprising the particles and alumina slurry for polishing... 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