GB2401109A

GB2401109A - Polishing composition

Info

Publication number: GB2401109A
Application number: GB0407024A
Authority: GB
Inventors: Junichi Hirano; Yasushi Matsunami; Noritaka Yokomichi; Toshiki Owaki
Original assignee: Fujimi Inc
Current assignee: Fujimi Inc
Priority date: 2003-03-31
Filing date: 2004-03-29
Publication date: 2004-11-03
Anticipated expiration: 2024-03-29
Also published as: JP4202172B2; JP2004300348A; GB2401109A8; GB2401109B8; CN100389161C; GB2401109B; MY164438A; GB0407024D0; CN1536046A

Abstract

A polishing composition for use in polishing a substrate for a magnetic disk comprises silicon dioxide; a first compound containing at least one compound selected from the group consisting of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, sodium metaphosphate and acidic sodium hexametaphosphate; a second compound containing at least on salt produced by a neutralisation reaction of each of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid with ammonia hydrogen peroxide; and water. The polishing composition may further contain a polishing accelerator e.g. citric acid, succinic acid. Also shown is a method for polishing a substrate using the above composition.

Description

2401 1 09

POLISHING COMPOSITION

BACKGROUND OF THE INVENTION

The present invention relates to a polishing composition to be used for polishing a substrate for a magnetic disk and the like.

With respect to a magnetic disk for use as a hard disk serving as a memory device for a computer, there have been strong demands for high recording density. Therefore, a substrate for a magnetic disk is required to have superior surface characteristics, for example, to have less corrosion or scratches.

Japanese l,aid-Open Patent Publication No. 2002-327170 discloses a polishing composition improved so as to satisfy such a requirement for a substrate. The polishing composition contains an abrasive, an oxidizing agent, an organic phosphoric acid such as diethylene triamine pentamethylene phosphoric acid, and water. When a substrate is polished using the polishing composition, a protective film is formed on the surface of the substrate by the action of organic phosphoric acid and therefore, generation of corrosion and scratches on the surface during polishing is suppressed.

However, since the protective film formation action of organic phosphoric acid is not so strong, the degree of the suppressed corrosion and scratches is not so high. Therefore, there is yet room for improvement over conventional polishing compositions.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention À. .e no- ..

to provide a polishing composition more suitable for use in polishing a substrate for a magnetic disk.

To achieve the foregoing and other objectives and in accordance with the purpose of the present invention, a polishing composition is provided. The polishing composition includes silicon dioxide; a first compound containing at least one compound selected from the group consisting of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, physic acid, 1- hydroxyethylidene-1,1-diphosphonic acid, sodium metaphosphate, and acidic sodium hexametaphosphate; a second compound containing at least one salt produced by a neutralization reaction of each of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, physic acid, and 1-hydroxyethylidene-1,1-diphosphonic acid with ammonia; hydrogen peroxide; and water.

Other aspects and advantages of the invention will become apparent from the following description, illustrating by way of example the principles of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described.

A polishing composition according to this embodiment, which contains silicon dioxide, a phosphorus-containing compound, ammonium salt, hydrogen peroxide, and water, is used for polishing, for example, a substrate for a magnetic disk.

This substrate may be a substrate formed by providing an electroless plating layer composed of nickel-phosphorus on a : I.: À À- ..

:::: :-:-:- :- : . . : . . blank member composed of an aluminum alloy, a substrate formed by providing a layer composed of nickel-iron on a blank member, or a substrate containing boron carbide or carbon.

The above-described silicon dioxide is an abrasive and plays a role in mechanically polishing an object. As for abrasives other than silicon dioxide, known abrasives are cerium oxides, diamond, aluminum oxides and the like.

However, a polishing composition containing cerium oxide in place of silicon dioxide does not have the ability for polishing a substrate at a high speed. A polishing composition containing diamond or aluminum oxides in place of silicon dioxide frequently generate surface defects such as scratches or pits in the substrate during the polishing. On the contrary, a polishing composition according to this embodiment containing silicon dioxide as an abrasive, which has an ability for polishing a substrate at a high speed and moreover, scarcely generates scratches on the substrate during the polishing.

The polishing composition may contain two or more kinds of silicon dioxides. The silicon dioxide may be colloidal silica, fumed silica, or precipitated silica, and is preferably colloidal silica. The polishing composition containing colloidal silica hardly generates scratches on a substrate during the polishing. Colloidal silica is composed of amorphous silica particles the surface of which is charged, and is dispersed in a colloidal state in water. Colloidal silica is obtained by, for example, a method in which ultra fine colloidal silica from which sodium silicate and potassium silicate are removed through ion exchange, and is subjected to a particle-growing process, a method in which alkoxysilane is subjected to hydrolysis by using an acid or alkali, or a method in which an organic silicon compound is heated and decomposed in a wet system.

:.*:: :...:. *. : * . * * * . * . . Average particle size of the silicon dioxide determined from a specific surface area of the silicon dioxide measured by a BET method is preferably from 0.005 to 0.5 Em inclusive, more preferably from 0.01 to 0.3 Em inclusive. If the average particle size is smaller than 0. 005 am, the polishing composition does not have the ability for polishing the substrate at a high speed. In other words, the polishing rate of the polishing composition for the substrate is reduced. In addition, precise polishing becomes difficult because vibrations are generated in the polishing machine due to large polishing resistance. If the average particle size exceeds 0.5 m, precipitate is generated in the polishing composition, and as a result, the polished substrate surface becomes rough or scratches are generated on the substrate during the polishing in some cases.

The content of the silicon dioxide in the polishing composition is preferably from 0.01 to 40% by weight inclusive, more preferably from 0.1 to 10% by weight inclusive. If the content is less than 0.01% by weight, the polishing rate of the polishing composition for the substrate is reduced and moreover, precise polishing becomes difficult because vibrations are generated in the polishing machine due to large polishing resistance. If the content exceeds 40% by weight, silicon dioxides are agglomerated in the polishing composition, and as a result, storage stability is deteriorated and scratches may be generated in the substrate during the polishing due to the agglomerated silicon dioxide in some cases. In addition, a polishing composition containing a large amount of silicon dioxide is disadvantageous in terms of cost.

The above-described phosphorus-containing compound plays a role in chemically polishing an object and a role in À À À À À.. . Àe... ' À À a À À À À . . À À À À.

increasing acidity in the polishing composition to accelerate oxidization of the object by hydrogen peroxide. The phosphorus-containing compound contains at least one compound selected from the group consisting of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, physic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, sodium metaphosphate, and acidic sodium hexametaphosphate. Unlike citric acid which is a known polishing accelerator, the phosphoruscontaining compound has protective film formation action for forming a protective film having scratch resistance and corrosion resistance on the surface of the substrate during the polishing. Further, the phosphoruscontaining compound is strong in the protective film formation action as compared with diethylene triamine pentamethylene phosphoric acid.

The orthophosphoric acid is represented by the formula H3PO. The diphosphoric acid is represented by formula H4P2O7 and is also referred to as pyrophosphoric acid. The polyphosphoric acid is a linear polymeric phosphoric acid produced by dehydration condensation of orthophosphoric acid and is represented by the formula Hn+2PnO3n+l, wherein n represents an integer of 2 to 4 inclusive. The polyphosphoric acid is a mixture of linear polymeric phosphoric acids which are different from each other in the number of n, more specifically, a mixture of at least two compounds selected from diphosphoric acid, triphosphoric acid (Hsp3olo) and tetraphosphoric acid (H6P4Ol3). A condensation ratio of the polyphosphorlc acid, more specifically, a weight ratio of the orthophosphoric acid produced by hydrolysis of the polyphosphoric acid based on the weight of the polyphosphoric acid may be 105% or 116%, or may be values other than those.

The metaphosphoric acid is a cyclic phosphoric acid produced 3S by dehydration condensation of the orthophosphoric acid and is e r ^ ; À * À À . . . represented by the formula (HPO3)m, wherein m represents an integer of 3 to 8 inclusive. The methyl acid phosphate is also referred to as methyl phosphoric acid. The ethyl acid phosphate is also referred to as ethyl phosphoric acid. The physic acid is also referred to as inositol hexaphosphoric acid. The 1-hydroxyethylidene-1,1-diphosphonic acid is abbreviated to HEDP. The sodium metaphosphate is represented by the formula (NaPO3) me wherein m represents an integer of 3 to 8 inclusive. The acidic sodium hexametaphosphate is represented by the formula NaxHy(PO3)x+y, wherein x and y each represent an integer of 1 to 7 inclusive and the sum of x and y is from 3 to 8 inclusive.

The content of the phosphorus-containing compound in the polishing composition is preferably from 0.01 to 40% by weight inclusive, more preferably from 1 to 20% by weight inclusive.

If the content is less than 0.01% by weight, the polishing rate of the polishing composition for the substrate is reduced. If the content exceeds 40% by weight, corrosion is generated in the substrate during the polishing in some cases, and also it is not economical.

The above-described ararnonium salt contains at least one salt produced by a neutralization reaction of each of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, physic acid, and 1hydroxyethylidene-1,1-diphosphonic acid with ammonia, preferably contains at least one salt selected from the group consisting of triammonium orthophosphate ((NH4)3PO4), diarnmonium hydrogenorthophosphate ((NH4) 2HPO4), and ammonium dihydrogenorthophosphate (NH4El2PO4).

The ammonium salt has protective film formation action for forming a protective film having scratch resistance and : À : ; a

- - - - - - - - - - - - - - - -

corrosion resistance on the surface of the substrate during the polishing. Each metal salt of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, physic acid, and 1-hydroxyethylidene-1,1diphosphonic acid also has protective film formation action similarly to that of the ammonium salt. However, in the polishing composition containing the metal salt, silicon dioxide in the polishing composition is agglomerated due to a metal ion derived from the metal salt, and as a result, scratches is generated on the substrate during the polishing by the agglomerated silicon dioxide.

The content of the ammonium salt in the polishing composition is preferably from 0.01 to 30% by weight inclusive, more preferably from 1 to 10% by weight inclusive.

If the content is less than 0.01% by weight, the protective film formation action of the polishing composition is not so strong in some cases. When the protective film formation action of the polishing composition is not strong enough, corrosion and scratches are generated in the substrate during the polishing. A polishing composition containing ammonium salt in excess of 30% by weight is poor in stability.

The above-described hydrogen peroxide is an oxidizing agent and plays a role in oxidizing an object to accelerate mechanical polishing by an abrasive. Known as oxidizing agents other than hydrogen peroxide are nitric acid, potassium permanganate, persulfate, and the like. However, nitric acid has insufficient oxidizing power, and a polishing composition containing potassium permanganate or persulfate as an oxidizing agent generates scratches in the substrate during the polishing. On the contrary, hydrogen peroxide has a sufficient oxidizing power, is friendly to the environment and relatively inexpensive. Hydrogen peroxide may be added to the À c, see see e. ee e À e e e a e À e e I e polishing composition in the form of an aqueous solution containing hydrogen peroxide in an amount of 30 to 35% by weight.

The content of the hydrogen peroxide in the polishing composition is preferably from 0.1 to 5% by weight inclusive, more preferably from 0.3 to 1% by weight inclusive. If Che content is less than 0.1-- by weight, the polishing rate of the polishing composition for the substrate is reduced and scratches is generated on the substrate during the polishing in some cases. If the content exceeds 5% by weight, corrosion is generated in the substrate during the polishing in some cases and the polishing rate of the polishing composition for the substrate is not stable.

The above-described water plays a role as a medium for dispersing or dissolving components other than water in the polishing composition. It is preferred that the water contains as little impurities as possible. More specifically, purified water, ultrapure water, or distilled water is preferable.

The pH of the polishing composition is preferably from 0.5 to 5.0 inclusive, more preferably from 1.0 to 3.0 inclusive. If the pH is less than 0.5, corrosion is generated in the substrate during the polishing in some cases. If the pH exceeds 5.0, oxidization of the substrate due to hydrogen peroxide is suppressed, and as a result, the polishing rate of the polishing composition for the substrate is reduced.

A polishing composition according to this embodiment is prepared by mixing silicon dioxide, a phosphorus-containing compound, ammonium salt, hydrogen peroxide, and water. During the mixing, the order of in which each component is added may be in any order, or all the components may be added at the À À .. Àe.

À À À À À Àe. .. .e Àe ÀÀÀÀ ÀÀ À A . : _ _ same time.

When the surface of the substrate is polished using a polishing composition according to this embodiment, for example, the surface of the substrate is rubbed with a polishing pad while supplying the polishing composition to the surface of the substrate. The substrate after the polishing is washed and dried.

A polishing composition according to this embodiment is preferably used in the final polishing step in a plurality of polishing steps commonly carried out during the manufacturing processes for a substrate The present embodiment provides the following advantages.

A polishing composition according to this embodiment Contains a phosphorus-containing compound and an ammonium salt both having protective film formation action and therefore, generation of corrosion and scratches in the object during the polishing, in particular, in the substrate for a magnetic disk during the polishing, is effectively suppressed. Accordingly, a polishing composition according to this embodiment is extremely suitable for use in polishing a substrate, in particular, for use in finish-polishing a substrate. A substrate polished by use of a polishing composition according to the embodiment has good surface properties such as less corrosion and scratches and low surface roughness.

Accordingly, a polishing composition according to the embodiment contributes to the realization of high recording density in a magnetic disk.

A polishing composition according to the embodiment contains silicon dioxide for mechanically polishing an object, a phosphorus-containing compound for chemically polishing an À À e e e e e e e e e Àee e e sea eee ee e e e e À e e e À e e e e ee e object, and hydrogen peroxide for accelerating mechanical polishing by the silicon dioxide and therefore, the composition has an ability for polishing an object, in particular, polishing a substrate for a magnetic disk at a high speed. In other words, the polishing composition according to the embodiment is high in polishing rate for a substrate.

When ammonium salt in the polishing composition contains at least one salt selected from the group consisting of triammonium orthophosphate, diammonium hydrogenorthophosphate and ammonium dibydrogenorthophosphate, the effect of the polishing composition in suppressing generation of corrosion and scratches of the substrate during the polishing can be maintained for a long period of time. This is because triammonium orthophosphate, diammonium hydrogenorthophosphate and ammonium dihydrogenorthophosphate have high stability in the polishing composition.

It should be apparent to those skilled in the art that the present invention may be embodied in many other specific forms without departing from the spirit of scope of the invention. Particularly, it should be understood that the invention may be embodied in the following forms.

The polishing composition may further contain a polishing accelerator for accelerating the mechanical polishing of silicon dioxide. The polishing accelerator preferably contains at least one compound selected from the group consisting of citric acid, maleic acid, maleic anhydride, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, crotonic acid, nicotinic acid, acetic acid, adipic acid, glycine, alanine, histidine, formic acid, and oxalic acid. The content of the polishing À . . À . ...

À À À Àe À À- < À À accelerator in the polishing composition is preferably from 0.01 to 40% by weight inclusive, more preferably from 1 to 20% by weight inclusive. If the content is less than 0.01% by weight, the mechanical polishing by silicon dioxide is not accelerated remarkably. If the content exceeds 40% by weight, corrosion may be generated in the substrate during the polishing.

The polishing composition may further contain a surfactant, a thickener, a chelating agent or an antifoaming agent, if necessary. The surfactant may be a polycarboxylic acid-based surfactant or may be a polysulfonic acid-based surfactant. More specifically, the surfactant may be sodium polystyrene sulfonate or may be sodium polyacrylate. The surfactant improves dispersibility of silicon dioxide in the polishing composition. The thickener may be water-soluble celluloses or polyvinyl alcohols.

The polishing composition may be prepared by diluting a stock solution with water immediately before use.

The polishing composition may be prepared by mixing hydrogen peroxide with a mixture of silicon dioxide, a phosphorus-containing compound, an ammonium salt and water immediately before use. In such a case, deterioration in storage stability due to decomposition of hydrogen peroxide in the polishing composition can be prevented.

The polishing composition may be used in polishing an object other than a substrate for a magnetic disk. The object other than a substrate for a magnetic disk may be an object containing tungsten, copper, silicon, glass, or ceramic. More specifically, the object may be a semiconductor water or an optical lens.

À À. tee À À À À À À À À À ÀÀÀÀ ÀÀ À À À À . . . À À À.

À À _ The present invention will now be described in more detail by referring to Examples and Comparative Examples.

In Examples 1 to 22, polishing compositions were prepared by mixing colloidal silica, a phosphorus-containing compound, an ammonium salt, hydrogen peroxide, and water. In Examples 23 to 26, polishing compositions were prepared by mixing colloidal silica, a phosphorus-containing compound, an ammonium salt, hydrogen peroxide, a polishing accelerator, and water. In Comparative Examples 1 to 5, polishing compositions were prepared by mixing at least two compounds selected from a phosphortls-containing compound, an ammonium salt, and hydrogen peroxide with colloidal silica and water. In Comparative Examples 6 to 11, polishing compositions were prepared by mixing at least two compounds selected from a phosphorus- containirg compound, an ammonium salt, and hydrogen peroxide with colloidal silica, a polishing accelerator, and water. In Comparative Examples 12 and 13, polishing compositions containing diethylene triamine pentamethylene phosphoric acid in place of the phosphorus-containing compound were prepared.

Detailed compositions of respective polishing compositions are shown in Tables 1 and 2.

It should be noted that each of the colloidal silicas in Examples 1 to 9, and 12 to 26, and Comparative Examples 1 to 13, has an average particle size of 30 no, the colloidal silica in Example]0 has an average particle size of 50 nm and the colloidal silica in Example 11 has an average particle size of 10 no. Further, the condensation ratio of polyphosphoric acid is 116%.

Using each of the polishing compositions in Examples 1 to 26 and Comparative Examples 1 to]3, the surface of a substrate was polished under the following polishing conditions.

: À : amp::: :: .:' :e.

Polishing conditions: Substrate to be polished: a substrate of +3.5 inches (about 95 mm) provided with a nickel-phosphorus electroless plated layer, which has been preliminarily polished to have a value of surface roughness Ra of about 6 A measured by a scanning probe microscope "Nanoscope III" manufactured by Digital Instrument Co., Ltd. Polishing machine: a double-sided polishing machine, "SFDL-9B", manufactured by SPEEDFAM Co., Ltd. Polishing pad: a suede-type polishing pad, "Belatrix N0058", manufactured by Kanebo, Ltd. Polishing load: 80 g/cm2 Rate of revolution of lower fixed base: 30 rpm Rate of supply of polishing composition: 40 ml/min I Polishing time: 8 minutes Number of polished substrates: 10 With respect to polishing processes carried out under the above-mentioned conditions, the polishing rate was calculated based on the following equation. The column entitled "polishing rate" in Tables 1 and 2 indicates the result of evaluation determined from the calculated polishing rate, based upon the four ranks shown in the column entitled "polishing rate" in Table 3.

Equation Polishing rate (,um/min) = reduced amount of substrate (a) due to polishing / [area (cm2) of substrate surface to be polished x density (g/cm3) of nickel-phosphor plated layer x polishing time (min)] x 104.

The thus polished substrates were observed using an ultrafine defect visualizing macro inspecting apparatus "MicroMax VMX2100" manufactured by VISION PSYTEC Co. Ltd., and À À ÀÀ À : À.e À . ..

the number of scratches in the surface of each substrate was measured. The column entitled "scratches" in Tables 1 and 2 indicates an evaluation result determined from the average value of the number of scratches measured by using ten samples, based on the four ranks shown in the column entitled "scratches" in Table 3.

In order to investigate to what degree the substrates were corroded by each polishing composition in Examples 1 to 26 and Comparative Examples 1 to 13, a substrate provided with a nickel- phosphorus electroless plated layer and having a diameter of 3.5 inches was dipped in a polishing composition at 30 C for 3 hours. The weight reduction amount of the substrate due to the dipping was measured. From the weight reduction amount each measured by use of two samples, corrosiveness was evaluated with the four ranks shown in the column entitled "corrosiveness" in Table 3. The results thereof are shown in the column entitled "corrosiveness" in

Tables 1 and 2.

Table 1 f4t

Ex. 1 30nm) polyphosphoric (NH4)2HPO4 3002 O | O | EX'2 (30nm, polyphosphoric 0 w t L. Owt % (NoH.4)WHt%O4 ho 0' | Ex. 3 co L. silica po yphosphoric NH 2Oz 5.0wt% Z.Owt% (o.4)wHt%O4 l.Owt! _ (of O P,x.9 col silica polyphosphorlc 1 O _ (30r.m) acid NHH2PO. L.Owtt () Ex.5 (30nm) polyphosphoric (NH4)3PO4 H:O _ 5 Owt% LaOwtd% 0.4wt% l.Owtt _ (of Ex.6 colt slllca polyphosphoric (9H<} zHPo. 1.0wt! = - O _ À À À À À À. À - À À À À À À

Table 1: continued ''

En 7colt sil ca polyphosphoric (N HPO N O --- S 0wt% 1.0wt% 1.0wt% 1.0wtt _ O o) Ex.9colt sill ca PO l yphcoi dho r i c ( NH4 2H PO. O. . 3wLt. O O Ex.91 i - 92 - - 0wt% _ acid (NoH.4)WH%O. 3.7wt% _ O EY.1O colt silica P lYPhOcldhOriC (NoH4)2HPO4 1 0wt% O EH.ll col 513Ej polyphosphoric {NH42HPO4 E O2 (10nm) ac d 0.9wt% 1.0wLt O Ex.12 colt si: polypahcsdhoric (NH42HPO4 1 Owtt _ O Ex.13 col silica polyphosphoric (N HPO _ 10.0wt% 1.0wt% 0.4wt% H2O2t - () O t Ex.14 colt silica diphosphoric acid H 0 5.0wt% 1.0wt% (NoH.44wHtP%O4 1 Owtt _ () Ex.15 col silica ortnophosphoric H O _ (30nm) acid (NoH44wHtP%04 1.0wtt _ O t) O Ex.16 colt silica metaphosphoric (NH4) 2HPO4 1. 0wtt _ Ex.17 ol. .silica acidic sodium (NH4) 2HpO4 H O. (30nm) hexametaphosphate 0.4wt% _.0wt% _ Ex.l9 colt silica methyl acid NH HP HzO2 (30nm) 1.0wt% o.49 2t%O4 1. 0wtt O (o) Ex.l9 colt silica phosphate NH HPO H 530Ontm% 1.Owt% ( o.4)wt% 4 l.Owt% _ O Ex.20 col silica ethyl glycol acid U (30nm) phosphate (NH412HPO4 0wt% l 0wt% 0.4wt% 1 0wt% _ Ex.21 (30nm) physic acid (NoH4)2HPO4 1. H0Ott _ O (o) Àx.22 colt silica HED (NH4)2HPO4 H'O2 5.30wtmo 1.0wt% 0. 9wt: 1. 0wtt. O (o) O Ex.23 colt silica orth phosphoric. H O:- _ (30nm) acid (N0H492d%O4 1.0wt% acid O Ex.29 colt silica metaphosphoric H 0 citric 5.0wt% acid (NoH44wHtPcO4 l.0wt% 1.0wtt Ex.25 colt sil Ica orthophosphoric (NH4) 7HPO4 1. 0wl% acd __ Ex.26 colt silica orth sp oric H 0 -715: 7 _ (.30wtm)c 1.0wt - ( NH4) zH PO4 1. 0 w % 1. Owt% ) (o) O 2..2 À'. .- À . À

Table 2

, o 9: : C. x. colt silica phosphoric owtlo.Owt% ( NH4) 2EIPo4 _ _ X X O C.Ex.2 colt silica ortho- _ _ phosphoric 5.30wt) laOwtd% (NoH.44WH%O4 _ _ X X O C.Ex.3 colt sili.ca poly- . _ _ _ phospihdric _ - ( O 5.30wt) l Owt% l.HOw2tl C.Ex.4 colt silica diphosphoric _ 5.0wt% acid _ 1.0wt% O A C.Ex.5 colt silica _ (30nm) _ (NoH442HE2O4 1HOwt% _ X X () C.Ex.6 colt silica _ _ (NH4) 2HPO4 citric acid 5.0wt% 0.4wt 1.Ho2wt% l.Owt% O A C.Ex.7 colt silica _ 5.0wt% _ (NoH442HPO4 1.Ho2w2t% maleic acid O A C.Ex.8 co]. silica _ _ _ (30nm) _ (NoEl442ElPO4 1.Ho2Wt% malonic acid O t) C.Ex.9 disodium _ (3Onm) _ ( NEi4) 2HPO4 H202 SIJccinate 5. Owt% 0. 4wt% 1. Owt% methanc- O sulfonic acid C.Ex.10 co]. silica 1. 0wt% _ 30nm) _ (NH4)2HPO4 sulfuric acid 5.0wt% 0.4wt% 1HOwt% 1. Owt% t) O X (NH HPo H 0 meth ne0.4wt S 1fonic acid O O X = co: ca T.Owt! T.Owt% _ _ (80r) PBTC (NoH4)2HPO4 HOwOt% _ C.Ex.13 colt slllca PE3TC HOz _ 5.0wt l Owt% = I.Owt! _ O X

Table 3

Evaluatl.on Polishing rate Scratches Corrosivencss crlterla Cpm/min; [number] _ [A] not less than 0.10 less than 20 less than 5 C) 0.07 to 0. 10 20 to 50 5 to ncluslve 1nc]uslve inclusive 0.04 to 0.0/ 50 to 100 8 to 10 _ 1nclusve inclusive inclusive X less than 0.04 not less than 100 not less than 10 ..

:::: :-::- :.

: .e ' À . As shown in Tables 1 and 2, in Examples 1 to 26, any of evaluation results of polishing rate, scratches and corrosion are good. In contrast, in Comparative examples 1 to 13, at least any one of evaluation results of polishing rate, scratches and corrosion is not good.

The present examples and embodiments are to be considered as illustrative and not restrictive and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalence of the appended claims.

: ... : . '. À:' À À À À. À * À a À À À À À À. À À .

Claims

CLAIMS: 1. A polishing composition characterized by: silicon dioxide; a

first compound containing at least one compound selected from the group consisting of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl ylycol acid phosphate, physic acid, l-hydroxyethylidene-1,1dlphosphonic acid, sodium metaphosphate, and acidic sodium hexametaphosphate; a second compound containing at least one salt produced by a neutralization reaction of each of orthophosphoric acid, diphosphoric acid, polyphosphoric acid, metaphosphoric acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, physic acid, and lhydroxyethylidene-1,1- diphosphonic acid with ammonia) hydrogen peroxide; and water.
2. The polishing composition according to claim 1, characterized by a polishing accelerator containing at least one compound selected from the group consisting of citric acid, maleic acid, maleic anhydride, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, crotonic acid, nicotinic acid, acetic acid, adipic acid, glycine, alanine, hl.sti.dine, formic acid, and oxalic acid.
3. The polishing composition according to claim 1 or 2, characterized in that the silicon di.oxide is colloidal silica.
4. The polishing composition according to any one of claims 1 to 3, characterized in that an average particle size of the À À e. Àe.

À À e.. Àe À. À.

a À À À silicon dioxide determined from a specific surface area of the silicon dioxide measured by a BET method is from 0.005 to O.S Am inclusive.
5. The polishing composition according to any one of claims 1 to 4, characterized in that the content of the silicon dioxide in the polishing composition is from 0.01 to 40% by weight inclusive.
6. The polishing composition according to any one of claims 1 to 5, characterized in that the content of the first compound in the polishing composition is from 0.01 to 40% by weight inclusive.
7 The polishing composition according to any one of claims 1 to 6, characterized in that the second compound contains at least one compound selected from the group consisting of triammonium orthophosphate, diammonium hydrogenorthophosphate and ammonium dihydrogenorthophosphate
8. The polishing composition according to any one of claims 1 to 7, characterized in that the content of the second compound in the polishing composition is from 0 01 to 30% by weight inclusive.
9. The polishing composition according to any one of claims 1 to 8, characterized in that the content of the hydrogen peroxide in the polishing composition is from 0 1 to 5% by weight inclusive.
lO. The polishing composition according to any one of claims 1 to 9, characterized in that the pH of the polishing composition is from 0.5 to 5.0 inclusive.
11. The polishing composition according to any one of claims À .& ... À À À

amp::: :': À:e:; 1 to 10, characterized in that the polishing composition is used in finish-polishing of a surface of a substrate for a magnetic disk.
12. A method for polishing a substrate for a magnetic disk, the method characterized by: preparing the polishing composition according to any one of claims I to 10; polishing the surface of the substrate by using the polishing composition.
13. A polishing composition substantially as hereinbefore described with reference to the

examples.
14. A method for polishing a substrate for a magnetic disk substantially as hereinbefore described with reference to the examples.

: .'. : . '. À'' 2.;:: :' À:. :'. .