JP2002309238A - Two-component type abrasive slurry and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an abrasive slurry that does not cause scratches at the flattening and polishing during forming composite thin-film magnetic head elements. SOLUTION: An abrasive slurry is prepared by mixing, immediately before polishing of a magnetic head substrate, slurry (A) obtained by dispersing (a) aluminum oxide abrasive particles, (b) boehmite, and (c) a dispersion adjuvant selected from the group consisting of aluminum nitrates and nickel nitrates in an aqueous medium, and a liquid (B) consisting of (d) an aqueous solution of a water-soluble chelating agent. An aluminum nitrate or nickel nitrate is reacted with the chelating agent in an aqueous solution gradually with the passage of time to form crystals that become nuclei of large particles for causing scratches. However, if the slurry is used for polishing a substrate immediately after the two are mixed, no large particles are generated and no scratches occur on the processed substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film magnetic head used for a hard disk drive (HDD), and more particularly to a two-pack type abrasive slurry suitable for polishing a substrate for a composite thin film magnetic head and its preparation. About the method.

[0002]

2. Description of the Related Art With the increase in the storage capacity of HDDs, the transition from a magnetic induction type thin film magnetic head to a magnetic induction writing / magnetic resistance reading combined type thin film magnetic head (so-called MR head) has recently been progressing. In such a background, attention has been paid to the roughness of the underlayer surface before forming the MR element as an item that affects the characteristics of a magnetoresistive element (MR element) composed of a thin film stack, and JP-A-9-54914 discloses an MR underlayer. We propose to polish the alumina surface which is a minute amount. Also,
Japanese Patent Application Laid-Open No. Hei 8-96237 discloses that a polishing process is performed to eliminate the undulation of the upper shield surface caused by the difference in the thickness of the underlayer, and Al ₂ O ₃ and a powder are formed at the final stage of the polishing.
It is proposed to polish Maloy's NiFe.

In these prior arts, a polishing technique is mentioned as a method for creating a surface. Polishing of a composite type thin film magnetic head, for example, aluminum oxide (Al ₂ O) as an insulating film is used.
₃ ) It is necessary to simultaneously polish NiFe and the like constituting the magnetic circuit, and the surface roughness of both of them must be Rmax 100
Angstroms or less and Ra 10 Angstroms or less, and the difference in surface height between them is 1000 or less.
There is no specific disclosure about an abrasive slurry used for polishing in response to a requirement for surface flatness such as suppressing the thickness to angstrom or less.

Japanese Patent Application Laid-Open No. 2000-63804 discloses an abrasive slurry for a magnetic head substrate satisfying the above requirements, in which an aqueous medium contains 5 to 20% by weight of boehmite abrasive grains and 0.1 to 10% by weight of aluminum nitrate. An abrasive slurry containing 0.1% to 3% by weight of a water-soluble chelating material and 0.1% to 3% by weight of an aqueous medium, wherein the boehmite abrasive grains have (a1) an average particle diameter of 100 to 500 μm. Boehmite and (a2)
Boehmite having an average particle size of 10 to 30 μm
An abrasive slurry used at a mixing ratio of 25:75 has been proposed.

The abrasive slurry provides a polished substrate having a flat and uniform surface without causing scratches on the substrate.

[0006]

However, recently, with the increase in the diameter and the integration of the substrate, the polishing rate is such that the polishing end point can be visually confirmed and the polishing rate is high.
Abrasive slurries capable of achieving a polishing rate of 1 to 1.0 μm / min are required from the market, and aluminum oxide (alumina) is used to increase the polishing rate and to achieve uniform surface flatness.
Examination of the combination use of boehmite and boehmite revealed that the polishing rate was improved, and that the abrasive slurry was stable even after storage for three months.

However, the boehmite used in combination has a particle size of 10
When the boehmite having a diameter as large as 0 to 500 nm (nanometer) is excellent in the storage property of the abrasive slurry, when the boehmite to be used in combination is as fine as 10 to 100 nm in particle size, the slurry becomes -When more than one month has passed since the preparation, formation of a large number of giant particles was observed, and it was found that scratches were easily generated on the polishing substrate when the abrasive slurry having the giant particles formed thereon was used.

Although the mechanism of the generation of the giant particles is unknown, the pH during storage of the abrasive slurry, for example, the pH was 3.4 at the initial stage of preparation of the abrasive slurry, but when the giant particles are generated. From the fact that the pH reaches about 2 and the acidity increases, and from the shape of the giant particles, it is presumed that alumina is recrystallized.

In order to prevent the occurrence of such scratches, a polishing operator of the substrate uses up the abrasive slurry delivered from the slurry supplier in the order of delivery date and uses up the abrasive slurry within three months after preparation. However, since the worker has a habit of using the abrasive slurry near the entrance of the warehouse instead of in order of the delivery date, the abrasive slurry that has passed three months after preparation has been attached to the container. May be used without confirming the preparation date described in (1), which causes scratches.

[0010] After three months, the abrasive slurry in which the giant particles have been formed can be reused by filtering to remove the giant particles, but the polishing operator of the substrate does not like such a filtering operation. INDUSTRIAL APPLICABILITY The present invention does not require the control of the elapsed time after the preparation of the abrasive slurry, and can be used by mixing at the site of use in an abrasive slurry using both boehmite and alumina having a fine particle size of 10 to 100 nm. It is intended to provide a two-part slurry.

[0011]

SUMMARY OF THE INVENTION The first aspect of the present invention provides a two-part type abrasive slurry for a magnetic head substrate, comprising the following liquids A) and B). A) Solution A slurry in which (a) aluminum oxide abrasive grains, (b) boehmite, and (c) a dispersing aid selected from aluminum nitrate or nickel nitrate are dispersed in an aqueous medium. B) Solution (d) aqueous solution Aqueous solution of a chelating agent.

[0012] The invention of claim 2 is that, before use for polishing a magnetic head substrate, it is selected from (a) aluminum oxide abrasive grains, (b) boehmite, and (c) aluminum nitrate or nickel nitrate. A method for preparing an abrasive slurry, comprising mixing a slurry A) in which a dispersing aid is dispersed in an aqueous medium and a solution B) consisting of (d) an aqueous solution of a water-soluble chelating agent. Is what you do.

By dissolving the water-soluble chelating agent (d) having low solubility in water in water, mixing of the two solutions A and B becomes easy. Further, by storing aluminum nitrate or nickel nitrate, which acts as a catalyst for the production of macroparticles, separately from the water-soluble chelating agent for improving the polishing rate before the preparation of the polishing agent, the macroparticles at the time of storing the solution A can be obtained. Can be prevented.

Compounds (a) and (b) containing aluminum or nickel metal forming a chelate metal double salt
Solution A in which (c) and (c) are dispersed in an aqueous medium is a slurry.
Before the preparation, the mixture is stored without being mixed with the chelating agent, so that there is no formation of a double metal salt of a chelate which is a nucleus for forming giant particles.

According to a third aspect of the present invention, the composition of the prepared abrasive slurry is as follows: (a) the average particle diameter is 0.05 to 1 μm;
aluminum oxide abrasive grains of 1 to 10% by weight, (b) boehmite having an average particle size of 10 to 100 nm 0.1 to 3% by weight, (c) aluminum nitrate or nickel nitrate 0.1 to 3% by weight, (D) Water-soluble chelating agent 0.1
-3% by weight, and (e) 78-95% by weight of aqueous medium
And a water-dispersible abrasive slurry containing

(C) aluminum nitrate and (d)
The presence of a water-soluble chelating agent enhances the polishing rate. (B)
Boehmite having an average particle size of 10 to 30 nm suppresses generation of scratches. Further, (a) the aluminum oxide abrasive having an average particle diameter of 0.05 to 1 μm is used, so that the flatness of the polished substrate surface is also improved.

The invention of claim 4 is characterized in that the water-soluble chelating agent (d) is a sodium salt of ethylenediaminetetraacetic acid or a sodium salt of ethylenetriaminepentapentaacetic acid.

It is a water-soluble chelating agent which is excellent in collecting free metal ions.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The magnetic head substrate to be polished: the two-part slurry of the present invention and the slurry obtained by the preparation method of the present invention are composed of NiP, Ni provided on the surface of the AlTiC substrate.
It is used for flattening and polishing during the formation of the element of the symbol type magnetic head provided with the FeP, NiCoFe permalloy and the Al ₂ O ₃ insulating film.

The two-part polishing slurry of the present invention is a two-part polishing slurry for a magnetic head substrate comprising the following liquids A) and B). A) Solution A slurry in which (a) aluminum oxide abrasive grains, (b) boehmite, and (c) a dispersing aid selected from aluminum nitrate or nickel nitrate are dispersed in an aqueous medium. B) Solution (d) aqueous solution Aqueous solution of a chelating agent.

The aluminum oxide (alumina) abrasive grains of the component (a) are particles having an average particle diameter of 0.05 to 1.0 μm, preferably 0.3 to 0.5 μm. Alumina is α
-Any of alumina, β-alumina and γ-alumina may be used. Further, a mixture thereof may be used. The content of the (a) component alumina abrasive grains in the abrasive slurry is 1 to 10% by weight, preferably 2 to 3% by weight.
If it is less than 1% by weight, a practical polishing rate cannot be obtained. 10
If the content exceeds% by weight, no further improvement in the effect can be expected, and it is economically disadvantageous to use many of them.

The boehmite as the component (b) is produced by subjecting gypsite to a hydrothermal treatment under pressure at about 250 ° C. or by hydrolyzing an aluminum organic compound {Al (OR) ₃ } which is activated by the Ziegler method. , Al / OOH or A
represented by the chemical formula of _{l 2 O 3 · H 2 O} .

The average particle size of boehmite is 10 to 100 nm.
Having the property of forming a colloidal sol with water.

The dispersing aid (c) improves the dispersibility of aluminum oxide (a) and boehmite (b), and aluminum nitrate and nickel nitrate are used alone or in combination. These dispersing aids also have the effect of accelerating the polishing rate. The dispersing aid (c) is used at a ratio of 0.1 to 3% by weight in the prepared abrasive slurry.

The water-soluble chelating agent (d) is added to the slurry for the purpose of improving the polishing rate and improving the uniformity of the obtained wafer. As such a water-soluble chelating agent, ethylenediaminetetraacetic acid (ED
TA), disodium salt of ethylenediaminetetraacetic acid (EDTA-2), sodium ethylenetriaminepentaacetic acid
Salt aminosulfonic acid-N, N-2 acetic acid alkali metal salt,
Examples thereof include alkali metal salts of 2,2-dimethylpropanebisoxamide, diethylenetriaminepentaacetic acid, and sodium salts thereof. Among them, ethylenediaminetetraacetic acid 2Na salt (EDTA-2) or ethylenetriaminepentaacetic acid Na salt is preferable.

The water-soluble chelating agent of the component (d) is used in an amount of 0.1 to 3% by weight in the abrasive slurry. (D)
Before preparing the abrasive slurry by mixing the A solution and the B solution, the water-soluble chelating agent of the components is dissolved in an aqueous medium to form the B solution, and stored in a container, and the A solution is stored. Stored and delivered with containers The amount ratio of the water-soluble chelating agent (d) to the aqueous medium in which it is dissolved is such that the content of the water-soluble chelating agent in the slurry after preparation of the abrasive slurry is 0.1%.
The amount is such that the chelating agent dissolves in the aqueous medium.

Aqueous medium: As the aqueous medium, water alone or water as a main component (70 to 99% by weight in the aqueous medium), and a water-soluble organic solvent such as alcohol or glycol as a subcomponent (1) -30% by weight) can be used. The water is preferably water that is obtained by filtration through a 0.1 μm cartridge filter and contains as little macroparticles as possible. Alcohols include methyl alcohol, ethyl alcohol, and isopropyl alcohol, and glycols include ethylene glycol, tetramethylene glycol,
Examples include diethylene glycol, propylene glycol, and polyethylene glycol having a molecular weight of 150 to 400.

The content of the aqueous dispersion medium in the abrasive slurry is 78 to 95% by weight, preferably 90 to 95% by weight. If the content is less than 78% by weight, the viscosity of the abrasive slurry becomes high, and the supply of the abrasive slurry onto the substrate is poor.

Other components: In addition to the components a), b), c) and d) and the aqueous medium, the polishing slurry has a polishing oil having a function of a dispersant for abrasives, if necessary. Rust agents, defoamers, pH adjusters, fungicides and the like are compounded. Examples of such polishing oils include various surfactants, ethylene glycol, propylene glycol, and polyethylene glycol.
And polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, pronic nonionic surfactants (addition products of ethylene oxide and propylene oxide) and the like.

Examples of the surfactant include an anionic surfactant, a cationic surfactant, a nonionic surfactant, an amphoteric surfactant, a combination of an anionic surfactant and a nonionic surfactant, and an anionic surfactant. Use of a surfactant and an amphoteric surfactant Combination of a cationic surfactant and a nonionic surfactant, and use of a combination of a cationic surfactant and an amphoteric surfactant. Abrasive oil is an abrasive slurry
Among them, it is used in a proportion of 0.5 to 5% by weight, preferably 1 to 2% by weight.

Examples of the pH adjuster include potassium hydroxide, sodium hydroxide, morpholine, aqueous ammonia and the like. As rust preventives, alkanolamine / alkano-
And nitrogen-containing organic compounds such as monoamine boric acid condensate, monoethanolamine, diethanolamine, triethanolamine, alkanolamine borate and benzisothiazolines. Defoaming agents include liquid paraffin, dimethyl silicone oil, monostearic acid, di-
Glyceride mixtures, sorbitan monopalmitiate, and the like. These may be used, if necessary, in an abrasive slurry.
Among them, an amount of 1.0% by weight or less is used.

Preparation of Abrasive Slurry: Abrasive slurry is prepared immediately before use for substrate polishing (1 minute to 24 hours before).
The liquid A and the liquid B are mixed and stirred. When transporting or storing both containers, a large container is placed in a cardboard box and a small container is placed in the empty space when transporting or storing both containers. In consideration of packing the cardboard box, a capacity ratio (A: B) of 8: 2 to 9: 1 is preferable.

In consideration of the amount of abrasive slurry used per day for one magnetic head substrate polishing apparatus and the scale of the abrasive slurry supply apparatus, the sum of the volumes of both containers is 1
~ 20 liters is preferred.

The present invention will be described in more detail with reference to the following examples. Example 1 2 parts by weight of α-alumina having an average particle diameter of 0.06 μm, 0.5 parts by weight of boehmite having an average particle diameter of 40 nm (nanometer), and 0.5 parts by weight of aluminum nitrate in an amount of 0.1 μm −
A stirring tank containing 45.5 parts by weight of a solution dissolved in 45 parts by weight of water passed through a cartridge filter and 2 parts by weight of polyethylene glycol having a molecular weight of 300, and 45 parts by weight of water passed through a 0.1 μm cartridge filter , And the mixture was stirred and mixed, and stored in a constant temperature room at 23 ° C. for 1 day to prepare a solution A. Then, about 9.44 liters of Liquid A (9,450 g in weight) was put into a high-density polyethylene hollow container for an internal volume of 10 liters using a pump, and stoppered.

0.5 parts by weight of a chelating agent ethylenediamine / tetraacetic acid disodium salt / dihydrate was added to 0.1 μm
The solution was dissolved in 5.0 parts by weight of water passed through a m-cartridge filter, and stored in a constant temperature room at 23 ° C. for 1 day to prepare solution B. Then, using a pump, 0.55 liter of Solution B was placed in a high-density polyethylene hollow container for an internal volume of 1 liter, and stoppered.

The container containing the solution A and the container containing the solution B were packed together in a cardboard box and transferred to a magnetic head substrate processing manufacturer.

One hour before the magnetic head substrate is polished by the magnetic head substrate processing manufacturer, the entire amount of the liquid B is added to the container containing the liquid A and stirred to prepare an abrasive slurry. Slurry supply equipment (supply pipe, motor, etc.) was attached to the container opening, and was attached to a polishing apparatus.

The abrasive slurry thus obtained is dropped onto a polishing pad attached to a polishing platen (platen) of a polishing apparatus, and the substrate of the composite magnetic head is pressed while dropping on the polishing pad. Polishing was performed under the following conditions at the rotation speed of the substrate. Platen rotation speed 40r. p. m. Substrate rotation speed 40r. p. m. Board pressure 200 g / cm ² Polishing time 5 minutes

Polished magnetic head substrate insulating film Al ₂ O
_When the surface roughness of NiFe ₃ and NiFe was evaluated at 1 μm by AFM, Rmax was approximately 50 angstroms and Ra was approximately 6 angstroms. The difference between the heights of the insulating film Al ₂ O ₃ and the NiFe of the substrate was 200 angstroms. When the surface of the alloy was measured by a surface defect analyzer using laser light, and the number of scratches having a width of 1 to 3 μm and a length of 20 μm or less was measured, micro scratches were not detected.

The polishing rate was 0.4 μm / min.

Reference Example 1 0.5 parts by weight of aluminum nitrate was dissolved in 45 parts by weight of water passed through a 0.1 μm cartridge filter.
In addition, 0.5 parts by weight of the chelating agent EDTA-2Na salt was added to water that passed through a 0.1 μm cartridge filter.
The resultant was dissolved in 5 parts by weight, and 2 parts by weight of polyethylene glycol having a molecular weight of 300 was added thereto. Then, the two aqueous solutions were mixed and stored in a constant temperature room at 23 ° C. for 1 to 5 days, and the amount of the precipitate (transparent crystal) was measured.

The amount of crystals relative to the aqueous solution was as follows. After 1 day 0.008 wt% After 2 days 0.036 wt% After 3 days 0.125 wt% After 4 days 0.138 wt% After 5 days 0.140 wt%

It is presumed that the precipitated crystals act as nuclei for generating giant particles.

Comparative Example 1 2 parts by weight of α-alumina having an average particle diameter of 0.06 μm, 0.5 parts by weight of boehmite having an average particle diameter of 40 nm (nanometer), and 0.5 parts by weight of aluminum nitrate .1 μm
45.5 parts by weight of a solution dissolved in 45 parts by weight of water passed through a cartridge filter, 2 parts by weight of polyethylene glycol having a molecular weight of 300, and a chelating agent ethylenediamine / tetraacetic acid disodium salt dihydrate 0. 5 parts by weight of water passed through a 0.1 μm cartridge filter
The mixture was dissolved in 9.5 parts by weight, mixed with stirring, and stored in a constant temperature room at 23 ° C. for 5 days to prepare an abrasive slurry.

Next, the abrasive slurry was filtered to obtain a particle size of 2
The particles having a size of μm or more were removed and stored in a constant temperature room at 23 ° C. for 2 months.

The composite magnetic head substrate was polished under the same conditions as in Example 1 using an abrasive slurry stored in a constant temperature room at 23 ° C. for two months. Of the 100 polished substrates obtained,
Scratches having a length of 20 μm or more were found in two sheets.

[0046]

The abrasive slurry of the two-part mixture type is mixed and prepared immediately before polishing of the magnetic head substrate, so that giant particles are not generated during substrate polishing. A magnetic head substrate having no flatness and excellent flatness uniformity is selected. The abrasive slurry prepared by the preparation method of the present invention can be used for flattening polishing in the process of forming a thin-film magnetic head, particularly a composite thin-film magnetic head, and also satisfies the surface roughness of a composite material, The difference in height between the materials can be kept small.

Claims (4)

[Claims] 1. A two-part abrasive slurry for a magnetic head substrate comprising the following liquids A) and B): A) liquid: (a) aluminum oxide abrasive grains, (b) boehmite, and (c) A slurry B) in which a dispersing aid selected from aluminum nitrate or nickel nitrate is dispersed in an aqueous medium. (D) An aqueous solution of a water-soluble chelating agent. 2. Before use for polishing a magnetic head substrate,
(Slurry A in which (a) aluminum oxide abrasive grains, (b) boehmite, and (c) a dispersing aid selected from aluminum nitrate or nickel nitrate are dispersed in an aqueous medium)
A method for preparing an abrasive slurry, comprising mixing a solution and a solution (B) comprising an aqueous solution of a water-soluble chelating agent. 3. The composition of the prepared abrasive slurry is as follows: (a) 1 to 10% by weight of aluminum oxide abrasive having an average particle diameter of 0.05 to 1 μm, and (b) an average particle diameter of 10 to 100.
0.1 to 3% by weight of boehmite, 0.1 to 3% by weight of (c) a dispersing aid selected from aluminum nitrate or nickel nitrate, and (d) a water-soluble chelating agent.
1-3% by weight, and (e) 78-95% by weight of aqueous medium
3. The method for preparing an abrasive slurry according to claim 2, wherein the slurry is a water-dispersible abrasive slurry containing: 4. The method for preparing an abrasive slurry according to claim 2, wherein (d) the water-soluble chelating agent is ethylenediaminetetraacetic acid 2Na salt or ethylenetriaminepentaacetic acid Na salt.