A polishing composition including a colloidal silica containing colloidal silica particles, a pH adjusting agent, and a chelating agent provides a substrate that has a surface having a high flatness, low defects and a low surface roughness with low cost and high productivity, and a substrate having high surface quality suitable as a substrate for mask blanks such as a glass substrate containing SiO.sub.2 as a main component, particularly, as a substrate for mask blanks used in EUVL.

An abrasive article having a plurality of apertures arranged in a non-uniform distribution pattern, wherein the pattern is spiral or phyllotactic, and in particular those patterns described by the Vogel equation. Also, provided is a back-up pad having a spiral or phyllotactic patterns of air flow paths, such as in the form of open channels. The back-up pad can be specifically adapted to correspond with an abrasive article having a non-uniform distribution pattern. Alternatively, the back-up pad can be used in conjunction with conventional perforated coated abrasives. The abrasive articles having a non-uniform distribution pattern of apertures and the back-up pads can be used together as an abrasive system.

Various embodiments disclosed relate to an abrasive article (10). The abrasive article (10 includes a backing (12) defining a major surface. The abrasive article (10) includes an abrasive layer including a plurality of tetrahedral abrasive particles (16) attached to the backing (12). The tetrahedral abrasive particles (16) include four faces joined by six edges terminating at four vertices (40, 42, 44, 46). Each one of the four faces contacts three of the four faces, and a major portion of the tetrahedral abrasive particles (16) have at least one of the vertices (40, 42, 44, 46) oriented in substantially a same direction.

An object of the present invention is to provide a nanobubble-containing inorganic oxide fine particle dispersion having excellent concentration stability in a process used as an abrasive. The object is achieved by the nanobubble-containing inorganic oxide fine particle dispersion including: inorganic oxide fine particles having an average particle size of 1 to 500 nm and containing fine particles containing Ce; and nanobubbles having an average cell size of 50 to 500 nm and being at least one non-oxidizing gas selected from a group consisting of N.sub.2 and H.sub.2.

Articles and methods regarding the making and use of low-shedding nonwoven abrasive articles, such as abrasive wheels and hand pads, that have a low shed rate and achieve a high grind ratio. The abrasive articles comprise a blend of a plurality of primary abrasive particles and a plurality of reinforcing abrasive particles that is disposed on a nonwoven web substrate. The primary abrasive particles have an average particle size equal to or larger than the average fiber diameter of the substrate fibers, and the reinforcing abrasive particles have an average particle size smaller than the average fiber diameter.

The present invention relates to an abrasive and a planarization method using the same, and more particularly, includes fumed silica. A BET specific surface area of the fumed silica is 200 m.sup.2/g to 450 m.sup.2/g, a shape of aggregates dispersed in the abrasive has an elongated shape or a round shape, and a ratio of the round shape of the aggregates is 50% to 90%.

An object of the present invention is to provide a silica particle, a silica sol containing the silica particle, and a polishing composition containing the silica sol, which prevent secondary aggregation, have excellent dispersion stability, and are suitable for polishing. The present invention relates to a silica particle in which an average value of a circularity coefficient measured by a field-emission scanning electron microscope is 0.90 or more, and a standard deviation of the circularity coefficient is 0.05 or less.

A polishing liquid for polishing a surface to be polished containing cobalt, the polishing liquid containing abrasive grains, at least one sugar component selected from the group consisting of a sugar alcohol, a sugar alcohol derivative, and a polysaccharide, an acid component, and water, in which a pH of the polishing liquid is more than 8.0.

A polishing composition having silica-based abrasive grains and a polishing method. A polishing composition having silica particles, wherein on the basis of a colloidal silica dispersion of the silica particles, the dispersion has an Rsp of 0.15 to 0.7 as measured using pulse NMR, and the colloidal silica particles have a shape coefficient SF1 of 1.20 to 1.80, wherein Rsp is calculated based on equation (1):

Rsp=(Rav−Rb)/(Rb)  (1) (wherein Rsp is an index that indicates water affinity; Rav is an inverse of a relaxation time of the colloidal silica dispersion; and Rb is an inverse of a relaxation time of a blank aqueous solution obtained by removing the silica particles from the colloidal silica dispersion), and the shape coefficient SF1 is calculated based on equation (2):

SF1=(area of a circle whose diameter is a maximum diameter of the particle)/(projected area)  (2).

A polishing composition that can not only achieve high polishing speed, but also can improve the surface smoothness (surface quality) of a polished substrate and reduce defects is provided. That is, provided is a polishing composition comprising silica particles and a water soluble polymer, wherein the contained silica particles satisfy the following requirements (a) to (c): (a) the primary particle diameter based on the specific surface area is 5 to 300 nm; (b) the coefficient of variation in the particle diameter is 10% or less; and (c) the Sears number Y is 10.0 to 12.0.