JP2001323253A - Composition for polishing magnetic disk substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polishing liquid composition capable of increasing the polishing speed of a magnetic disk substrate. SOLUTION: This composition for polishing the magnetic disk substrate is a polishing liquid comprising water, a polishing material and a polishing accelerator and the polishing accelerator is composed of at least one kind selected from the group consisting of a divalent or more polyvalent carboxylic acid having either one of alkene group (C=C), alkyne group (C≡C), ether group (C-O-C), thioether group (C-S-C), ketone group [(C=O)] or an aromatic ring as a functional group and a salt thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a composition for polishing a magnetic disk substrate.

[0002]

2. Description of the Related Art Hard disks are becoming smaller and have higher capacities year by year, and their density is increasing, the minimum storage area is getting smaller, and the flying height of the magnetic head is getting smaller. Therefore, there is a demand for a substrate having more surface properties and less surface defects such as scratches and pits in a polishing step of a hard disk substrate. Therefore, the average grain size of the abrasive grains used in each process is decreasing year by year, and accordingly, there is still a problem that the polishing rate is inevitably reduced and the productivity is reduced. Polishing compositions and polishing methods using water, alumina and organic acids have been studied (JP-A-2-84485, JP-A-7-216345, etc.), but a more excellent polishing rate has been studied. At present, there is a demand for a polishing composition having the following.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polishing composition capable of improving the polishing rate of a magnetic disk substrate.

[0004]

That is, the gist of the present invention is as follows.
A polishing liquid containing water, an abrasive, and a polishing accelerator, wherein the polishing accelerator contains an alkene group (-C = C-) and an alkyne group (-
C≡C—), ether group (—C—O—C—), thioether group (—C—S—C—), ketone group (— (C ＝ O))
-) Or at least one type of magnetic disk substrate polishing composition selected from the group consisting of divalent or higher carboxylic acids having at least one aromatic ring as a functional group and salts thereof (hereinafter, also referred to simply as polishing composition) ).

[0005]

DETAILED DESCRIPTION OF THE INVENTION As the polishing accelerator used in the present invention, an alkene group (-C = C-) and an alkyne group (-C
{C-), an ether group (-COC-), a thioether group (-CSC-), a ketone group (-(C = O)-)
Or divalent or higher carboxylic acids having any of aromatic rings as a functional group and salts thereof.

From the viewpoint of promoting polishing, the carboxylic acid preferably has 2 to 12 carbon atoms, more preferably 3 to 8 carbon atoms, and still more preferably 4 to 6 carbon atoms. From the viewpoint of availability, the valence of the carboxylic acid is divalent or more, preferably 2 to 3, and more preferably divalent. Examples of the functional group include an alkene group, an alkyne group, an ether group, a thioether group, a ketone group, and an aromatic ring. From the viewpoint of availability, an alkene group, an ether group, and an aromatic ring are preferred. Specific examples of the carboxylic acid include maleic acid, fumaric acid, itaconic acid, citraconic acid, diglycolic acid, thiodiglycolic acid, trimellitic acid, phthalic acid, pyromellitic acid, acetylenedicarboxylic acid, oxalacetic acid, Ketoglutaric acid, 1,3-acetone dicarboxylic acid and the like can be mentioned. Among these, maleic acid, fumaric acid, itaconic acid, diglycolic acid and citraconic acid are particularly preferred.

The salts of these acids are not particularly limited, and specific examples thereof include salts with metals, ammonium, alkylammonium, organic amines and the like. Specific examples of metals include the periodic table (long period type) 1A, 1B, 2
A, 2B, 3A, 3B, 4A, 6A, 7A or a metal belonging to Group 8 can be used. Among these metals, metals belonging to Groups 1A, 3A, 3B, 7A or 8 are preferable from the viewpoint of improving the polishing rate, and metals belonging to Groups 1A, 3A, 3B or 8 are more preferable, and sodium and potassium belonging to Group 1A. Most preferred are cerium belonging to Group 3A, aluminum belonging to Group 3B, and iron belonging to Group VIII.

Specific examples of the alkyl ammonium include
Examples include tetramethylammonium, tetraethylammonium, and tetrabutylammonium.

Specific examples of the organic amine and the like include dimethylamine, trimethylamine and alkanolamine.

Of these salts, ammonium salts, sodium salts, potassium salts and aluminum salts are particularly preferred.

These polishing accelerators can be used alone or in combination of two or more.

The content of the polishing accelerator in the polishing composition is 0.05% by weight from the viewpoint of improving the polishing rate.
The above is preferable, and 5% by weight or less is preferable from an economic viewpoint. The content is preferably 0.05 to 5% by weight, more preferably 0.1 to 3% by weight, further preferably 0.2 to 2% by weight, most preferably 0.25 to 5% by weight.
1% by weight.

As the abrasive used in the present invention, an abrasive generally used for polishing can be used. Examples of the abrasive include metal; metal or metalloid carbide,
Nitrides, oxides, borides; diamonds and the like. Metal or metalloid elements are listed in the Periodic Table (Long Period Type)
A, 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A
Or, it is derived from Group 8. As a specific example of the abrasive, α
-Alumina particles, silicon carbide particles, diamond particles,
Examples include magnesium oxide particles, zinc oxide particles, cerium oxide particles, zirconium oxide particles, colloidal silica particles, fumed silica particles, and the like. Use of one or more of these is preferred from the viewpoint of improving the polishing rate. Among them, α-alumina particles, cerium oxide particles, zirconium oxide particles, colloidal silica particles, fumed silica particles, and the like are more preferable, and α-alumina particles are particularly preferable.

The average particle size of the primary particles of the abrasive is preferably from 0.01 to 3 μm, more preferably from 0.02 to 0.8 μm, particularly preferably from 0.05 to 0.
5 μm. Further, when the primary particles are aggregated to form secondary particles, the average particle size of the secondary particles is similarly increased from the viewpoint of improving the polishing rate and reducing the surface roughness of the object to be polished. , Preferably 0.05 to 3 μm, more preferably 0.1 to 1.5 μm, particularly preferably 0.2 to 1.2 μm.
μm. The average particle size of the primary particles of the abrasive can be obtained as a number average particle size by observing (preferably 3000 to 30,000 times) with a scanning electron microscope, analyzing the image, and measuring the particle size. The average particle size of the secondary particles can be measured as a volume average particle size by using a laser light diffraction method.

The specific gravity of the abrasive is preferably from 2 to 6, more preferably from 2 to 5, from the viewpoints of dispersibility, supply to the polishing apparatus, and recovery and reuse.

The content of the abrasive in the polishing composition is preferably 1 to 40% by weight, more preferably from the viewpoint of economical efficiency, reduction of surface roughness and efficient polishing. It is 2 to 30% by weight, more preferably 3 to 15% by weight.

The water in the polishing composition of the present invention is used as a medium, and its content is preferably 40% from the viewpoint of enabling the object to be polished to be polished efficiently.
The content is preferably from 98 to 95% by weight, more preferably from 60 to 98% by weight, and particularly preferably from 70 to 95% by weight.

The polishing composition of the present invention may contain other components as necessary. Other ingredients include
Organic acids other than the carboxylic acids and salts thereof, for example, oxycarboxylic acids, monocarboxylic acids,
Organic acids and salts thereof such as carboxylic acids and polyaminocarboxylic acids having a valence of more than one, amino acids and the like, inorganic acids and salts thereof, oxidizing agents, thickeners, dispersants, rust inhibitors, basic substances, surfactants, etc. Can be Specific examples of organic acids and salts thereof, inorganic acids and salts thereof, and oxidizing agents are described in JP-A-62-25.
No. 187, page 2, upper right column, lines 3-11, JP-A-1-20
No. 5973, page 3, upper left column, line 11 to upper right column, line 2; JP-A-3-115383, page 2, lower right column, line 16 to page 3, upper left column, line 11; To 9 lines, JP-A-4-275387, page 2, right column, line 27 to page 3, left column, 12 lines, and JP-A-4-363385, page 2, right column, lines 21 to 30. Can be

These components may be used alone, or 2
A mixture of more than one species may be used. Also, its content is
From the viewpoint of improving the polishing rate, expressing each function, and economy, preferably 0.05 to 20% by weight, more preferably 0.05 to 20% by weight in the polishing composition.
It is 10% by weight, more preferably 0.05 to 5% by weight.

The concentration of each component in the polishing composition is a preferable concentration when polishing, but may be a concentration when the composition is manufactured. Usually, the composition is produced as a concentrated liquid, and this is often used after dilution.

It is preferable that the pH of the polishing composition is appropriately determined according to the kind of the object to be polished, required quality, and the like. For example, the pH is preferably from 2 to 12, from the viewpoints of substrate cleaning properties, processing machine corrosion prevention properties, and operator safety.
Further, when the object to be polished is a magnetic disk substrate mainly for a metal such as a Ni-P plated aluminum alloy substrate, from the viewpoint of improving the polishing rate and improving the surface quality, 2 to 2
9 is more preferable and 3 to 8 are particularly preferable. The pH is
If necessary, it can be adjusted by appropriately mixing inorganic acids such as nitric acid and sulfuric acid, organic acids, and basic substances such as ammonia, sodium hydroxide and potassium hydroxide in desired amounts.

As the magnetic disk substrate used in the present invention, an aluminum substrate, a Ni-P plated aluminum substrate, a Ni-Fe substrate, a boron carbide substrate, a carbon substrate, a glass substrate such as tempered glass or crystallized glass are used. And the like. Particularly, an aluminum substrate plated with Ni-P is preferable.

Although the polishing composition of the present invention is suitably used for polishing a magnetic disk substrate, it can also be used for polishing other precision component substrates. Examples of the precision component substrate include a substrate of a magnetic recording medium such as an optical disk and a magneto-optical disk, a photomask substrate, an optical lens, an optical mirror, an optical prism, and a semiconductor substrate. In addition,
Polishing of a semiconductor substrate includes a polishing step of a silicon wafer (bare wafer), a step of forming an embedded element isolation film, a step of planarizing an interlayer insulating film, a step of forming an embedded metal wiring,
There is polishing performed in an embedded capacitor forming step or the like.

The polishing composition of the present invention is particularly effective in the polishing step, but can be similarly applied to other polishing steps, for example, a lapping step.

[0025]

Examples 1 to 11, Comparative Examples 1 to 6 Abrasives (α-alumina having an average primary particle size of 0.23 μm and secondary particles of 0.5 μm (purity 99.9)
%)) 7 parts by weight, a predetermined amount shown in Table 1 of the polishing accelerator used in the examples and the compound used in the comparative example, and the remainder of the ion-exchanged water were mixed and stirred. Comparative Examples 2 to 5 were adjusted to pH 4 with aqueous ammonia, Example 8 was adjusted to pH 5.5 with aqueous ammonia, and Example 10 was adjusted to pH 5.5 with aqueous ammonia.
Comparative Example 1 was adjusted to pH 4 with nitric acid, and Comparative Example 6 was adjusted to pH 5 with ammonia water to obtain 100 parts by weight of the composition.

The obtained composition was polished under the following conditions. Polishing condition Workpiece 3.5 inch electroless Ni-P plated aluminum magnetic disk substrate Polishing machine 9B double-side polishing machine (Speed Fam Co., Ltd.)
Polishing pad Politex DG-High (Rodel Nitta Co., Ltd.) Working pressure 9.8 kPa Surface plate rotation speed 50 rpm Number of processed 10 Polishing liquid supply 100 ml / min Polishing time 4 min

After polishing, the thickness of the aluminum magnetic disk substrate was measured with a film thickness meter (manufactured by Mitutoyo Corporation, laser film thickness meter Mo).
del LGH-110 / LHC-11N) to determine the rate of thickness reduction from the change in the thickness of the aluminum magnetic disk substrate before and after polishing, and a relative value (relative speed) based on Comparative Example 1.
I asked. Table 1 shows the results.

[0028]

[Table 1]

From the results shown in Table 1, all of the compositions for polishing a magnetic disk substrate obtained in Examples 1 to 11 are shown in Comparative Example 1.
It can be seen that the polishing rate was improved as compared with the compositions obtained in Nos. 6 to 6.

[0030]

When polishing is performed using the magnetic disk substrate polishing composition of the present invention, a high polishing rate can be obtained.
This is useful from the viewpoint that productivity can be significantly improved.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3C047 FF08 GG15 3C058 AA07 DA02 DA17 5D112 AA02 AA11 BA06 GA02 GA09 GA26

Claims (2)

[Claims] A polishing liquid containing water, an abrasive, and a polishing accelerator, wherein the polishing accelerator is an alkene group (-C = C-),
Alkyne group (—C≡C—), ether group (—C—O—C
-), A thioether group (-C-S-C-), a ketone group (-(C = O)-) or an aromatic ring as a functional group. A magnetic disk substrate polishing composition comprising at least one selected from the group consisting of: 2. The composition for polishing a magnetic disk substrate according to claim 1, wherein the content of the polishing accelerator is 0.05 to 5% by weight.