CN100460478C - Polishing liquid composition for magnetic disk - Google Patents

Abstract

The present invention relates to the polishing liquid composition of magnetic disk that contains aluminum oxide, water, peroxide and organic acid, comprise the grinding method of the polished substrate of the process of using above-mentioned polishing liquid composition to grind the substrate to be polished, and comprise using above-mentioned polishing liquid A method of manufacturing a substrate in the step of polishing a substrate to be polished with the composition. The polishing liquid composition can be suitably used for producing high-quality magnetic disk substrates such as hard disks.

Description

Polishing liquid composition for magnetic disk

technical field

The present invention relates to a polishing liquid composition for a magnetic disk, a polishing method using the polishing liquid composition, and a method for manufacturing a substrate.

Background technique

In order to reduce the minimum recording area and increase the capacity of hard disks, it is required to reduce the floating amount of the magnetic head and prevent surface defects (surface contamination). In order to reduce the floating amount of the magnetic head, it is necessary to reduce short-wavelength surface waviness (surface waviness with a wavelength of 50 to 500 μm) and long-wavelength surface waviness (surface waviness with a wavelength of 0.5 mm or more) in the grinding process of the hard disk substrate, and to prevent surface waviness. the remains. The "surface waviness" as used herein refers to surface irregularities longer than the wavelength of the surface roughness, and can be measured with an optical measuring instrument such as "Zygo" manufactured by Canon Sales Co., Ltd. In order to manufacture such substrates with surface waviness and reduced surface contamination, mechanical conditions such as pore size control, hardness control, and polishing load and rotational speed control during polishing were studied. However, although these mechanical conditions are effective, they cannot be said to be sufficient. On the other hand, a method of passing a polishing liquid composition has also been studied. JP-A-2003-14733 discloses a polishing liquid composition containing oxidant, phosphorus-containing inorganic acid and other inorganic acids; Slurry for grinding process. However, the methods using these polishing liquid compositions cannot be said to be sufficient from the viewpoint of achieving both the polishing speed and the reduction of surface waviness required for practical use, and preventing surface contamination.

Contents of the invention

That is, the present invention involves

(1) A polishing liquid composition for magnetic disk containing aluminum oxide, water, peroxide and organic acid;

(2) the polishing method of the polished substrate comprising the step of polishing the polished substrate using the polishing liquid composition described in the above (1); and

(3) A method of manufacturing a substrate including a step of polishing a substrate to be polished using the polishing liquid composition described in (1) above.

Detailed ways

The present invention relates to a polishing liquid composition which has a high polishing speed and can reduce surface waviness. The present invention also relates to a polishing method using the polishing liquid composition, for example, reducing surface waviness of a substrate to be polished, and a method of manufacturing a substrate using the polishing liquid composition.

These and other advantages of the present invention will become apparent from the following description.

By using the polishing liquid composition of the present invention for polishing magnetic disks, a high polishing speed can be achieved, surface waviness of objects to be polished can be reduced, and substrate defects, especially substrate contamination, can be reduced. Also obtained are a polishing method and a substrate manufacturing method for reducing surface waviness of a substrate to be polished using the polishing liquid composition.

A major feature of the polishing liquid composition of the present invention is that an organic acid and a peroxide are used as a polishing accelerator of the polishing liquid composition using aluminum oxide as the polishing material. It is found that by using the polishing liquid composition with such characteristics, a high polishing speed can be achieved, the surface waviness of the substrate to be polished can be effectively reduced, and substrate defects such as scratches and pits can be achieved, especially the remarkable effect of reducing substrate contamination.

The details of the mechanism of polishing when the polishing liquid composition of the present invention is used are unclear. It is presumed that the lower the pH of the polishing liquid composition during polishing, the higher the polishing rate, and the corrosion effect of the hydrogen ions generated by the acid on the material to be polished promotes polishing, but it is not limited thereto. Therefore, the higher the acid strength, the higher the grinding rate. In addition, in order to give full play to the grinding effect of alumina, the peroxide changes the surface of the object to be ground to enhance the above-mentioned corrosion effect. The result is reduced surface waviness at production-level processing speeds. It is speculated that the enhanced effect obtained by the combination of the organic acid and the peroxide is also related to the reduction of substrate defects, especially the reduction of substrate contamination, but it is not limited thereto.

The polishing liquid composition of the present invention contains alumina as a polishing material. From the viewpoint of reducing surface waviness, reducing surface roughness, increasing grinding speed, and preventing surface defects, the alumina used in the present invention is preferably alumina with a purity of 95% or more, more preferably 97% Above, more preferably 99% or more of alumina. In addition, from the viewpoint of grinding speed, α-alumina is preferred; from the viewpoint of surface properties and reduction of surface waviness, γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina are preferred. Aluminum and other intermediate alumina. The intermediate alumina in the present invention is a general term for alumina particles other than α-alumina particles, and specific examples include γ-alumina particles, δ-alumina particles, θ-alumina particles, η-alumina particles, κ-alumina particles, Aluminum particles and their mixtures, etc. Among these intermediate aluminas, γ-alumina, δ-alumina, θ-alumina and mixtures thereof are preferred, and γ-alumina and θ-alumina are more preferred from the viewpoint of increasing the polishing rate and reducing surface waviness.

The average particle diameter of the primary particles of alumina is more preferably 0.005-0.8 μm, more preferably 0.01-0.4 μm, and more preferably the average particle diameter of the secondary particles is from the viewpoint of reducing surface waviness. 0.01 to 2 μm, more preferably 0.05 to 1.0 μm, still more preferably 0.1 to 0.5 μm. The average particle size of the primary particles of the abrasive can be determined by scanning electron microscope observation (preferably 3000-30000 times) or transmission electron microscope observation (preferably 10000-300000 times), image analysis, and particle size measurement. In addition, the average particle diameter of the secondary particles can be measured by the laser diffraction method as the volume average particle diameter.

In particular, when the alumina is intermediate alumina, the specific surface area measured by the BET method is preferably 30 to 300 m ² /g, more preferably 50 to 200 m ² /g.

From the viewpoint of increasing the grinding speed and reducing surface ripples, the content of alumina in the polishing liquid composition is preferably more than 0.05% by weight, more preferably more than 0.1% by weight, more preferably more than 0.5% by weight, and more preferably 1% by weight above. In addition, from the viewpoint of surface quality and economy, the content in the polishing liquid composition is preferably 40% by weight or less, more preferably 30% by weight or less, more preferably 25% by weight or less, and more preferably 20% by weight or less. That is, the content of alumina in the polishing liquid composition is preferably 0.05 to 40% by weight, more preferably 0.1 to 30% by weight, particularly preferably 0.5 to 25% by weight, even more preferably 1 to 20% by weight.

From the standpoint of advantages such as increasing the polishing speed and reducing surface waviness, the polishing liquid composition of the present invention should contain peroxide. The peroxides of the present invention can be broadly classified into inorganic peroxides and organic peroxides according to their structures. Specific examples of these peroxides are shown below. As inorganic peroxides, hydrogen peroxide, alkali metals such as sodium peroxide, potassium peroxide, calcium peroxide, barium peroxide, and magnesium peroxide, or peroxides of alkaline earth metals, sodium percarbonate, etc. can be used. , potassium percarbonate and other percarbonates; Its salts, superphosphoric acid such as sodium superphosphate, potassium superphosphate, ammonium superphosphate or its salts, perborates such as sodium perborate and potassium perborate, perchromates such as potassium perchromate and sodium perchromate Classes, potassium permanganate, sodium permanganate and other permanganates, sodium perchlorate, potassium perchlorate, chloric acid, sodium hypochlorite, sodium periodate, potassium periodate, iodic acid, sodium iodate and other halogens Oxygen acids or their derivatives. As the organic peroxide, percarboxylic acids such as peracetic acid, performic acid, and perbenzoic acid, and peroxides such as t-butyl peroxide and cumene peroxide can be used. Among them, inorganic peroxides are preferred in order to improve the polishing rate, ease of availability, and water solubility. Furthermore, from the viewpoint of environmental problems, inorganic peroxides that do not contain heavy metals are preferable. From the above viewpoints, inorganic peroxides are more preferred, especially hydrogen peroxide, persulfates, halogen-containing oxyacids or salts thereof, and hydrogen peroxide is still more preferred. In addition, these peroxides may be used alone or in combination of two or more.

From the viewpoint of improving the grinding speed and reducing surface ripples, the content of peroxide in the polishing liquid composition is preferably more than 0.002% by weight, more preferably more than 0.005% by weight, more preferably more than 0.007% by weight, and more preferably 0.01% by weight %above. In addition, from the viewpoint of surface quality and economy, the content in the polishing liquid composition is preferably 20% by weight or less, more preferably 15% by weight or less, more preferably 10% by weight or less, and more preferably 5% by weight or less. That is, the content of peroxide in the polishing composition is preferably 0.002 to 20% by weight, more preferably 0.005 to 15% by weight, even more preferably 0.007 to 10% by weight, and still more preferably 0.01 to 5% by weight.

From the point of view of increasing the grinding speed and reducing surface ripples, the polishing liquid composition of the present invention should also contain an organic acid in addition to aluminum oxide and peroxide. From the standpoint of improving the grinding speed and reducing surface waviness, the pK1 of the organic acid used in the present invention is less than 7, more preferably 5 or less, more preferably 4 or less, and more preferably 2 or less. Here, pK1 represents the logarithmic value of the reciprocal of the first acid dissociation constant at 25°C. The pK1 of each compound is described in Chemical Handbook Revised 4th Edition (Basic Edition) II, pp316-325 (Edited by the Chemical Society of Japan) and the like.

As suitable organic acids in the present invention, sulfur-containing organic acids, carboxylic acids, and phosphorus-containing organic acids are preferable from the viewpoint of increasing the polishing rate, reducing surface waviness, and preventing surface contamination. A specific example thereof is shown below. For example, formic acid, acetic acid, glycolic acid, lactic acid, propionic acid, hydroxypropionic acid, butyric acid, benzoic acid, glycine and other monocarboxylic acids, oxalic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid , itaconic acid, malic acid, tartaric acid, citric acid, isocitric acid, phthalic acid, nitrotriacetic acid, ethylenediaminetetraacetic acid and other polycarboxylic acids, methanesulfonic acid, p-toluenesulfonic acid and other sulfur-containing organic acids, Ethyl phosphate, butyl phosphate, lauryl phosphate, hydroxyphosphonoacetic acid, hydroxyethylidene-1,1-diphosphonic acid, phosphonobutanetricarboxylic acid, ethylenediaminetetramethylenephosphonic acid, etc. organic acids etc. Among them, from the viewpoint of increasing the polishing rate and reducing surface waviness, sulfur-containing organic acids and phosphorus-containing organic acids are preferred, organic sulfonic acids and organic phosphonic acids are more preferred, and organic sulfonic acids are particularly preferred. In addition, from the viewpoint of preventing contamination of the abrasive, sulfur-containing organic acids and carboxylic acids are preferable, and organic sulfonic acids and polycarboxylic acids are more preferable.

These compounds may be used alone or in combination.

From the viewpoint of improving the grinding speed and reducing surface ripples, the content of the organic acid in the polishing liquid composition is preferably more than 0.002% by weight, more preferably more than 0.005% by weight, more preferably more than 0.007% by weight, and more preferably 0.01% by weight above. In addition, from the viewpoint of surface quality and economy, the content in the polishing liquid composition is preferably 20% by weight or less, more preferably 15% by weight or less, more preferably 10% by weight or less, and more preferably 5% by weight or less. That is, the content of the acid in the polishing composition is preferably 0.002 to 20% by weight, more preferably 0.005 to 15% by weight, even more preferably 0.007 to 10% by weight, and still more preferably 0.01 to 5% by weight.

Water in the polishing liquid composition of the present invention is used as a medium. From the viewpoint of efficiently grinding the object to be ground, the water content is preferably 55 to 99% by weight, more preferably 60 to 97% by weight, and still more preferably 70 to 95% by weight.

From the viewpoint of further increasing the polishing rate and reducing surface waviness, it is preferable to use an inorganic acid in combination in the polishing liquid composition of the present invention. Examples of the inorganic acid include nitrogen-containing inorganic acids such as nitric acid and nitrous acid, sulfur-containing inorganic acids such as sulfuric acid, sulfurous acid, and sulfamic acid, and phosphorus-containing inorganic acids such as phosphoric acid, pyrophosphoric acid, polyphosphoric acid, and phosphonic acid. Among these, nitric acid, nitrous acid, sulfuric acid, sulfurous acid, and sulfamic acid are preferred, sulfuric acid, sulfurous acid, and sulfamic acid are more preferred, and sulfuric acid is still more preferred, from the viewpoint of increasing the polishing rate. When an inorganic acid is used in combination, its content in the polishing liquid composition is preferably at least 0.002% by weight, more preferably at least 0.005% by weight, still more preferably at least 0.007% by weight, and still more preferably at least 0.01% by weight. In addition, from the viewpoint of surface quality and economy, the content in the polishing liquid composition is preferably 20% by weight or less, more preferably 15% by weight or less, particularly preferably 10% by weight or less, and more preferably 5% by weight or less. That is, the content of the inorganic acid in the polishing liquid composition is preferably 0.002 to 20% by weight, more preferably 0.005 to 15% by weight, particularly preferably 0.007 to 10% by weight, and even more preferably 0.01 to 5% by weight.

In addition, other components such as inorganic salts, thickeners, rust inhibitors, and alkaline substances may be added to the polishing liquid composition of the present invention as needed. In particular, inorganic salts such as ammonium nitrate, ammonium sulfate, potassium sulfate, nickel sulfate, aluminum sulfate, and ammonium sulfamate have an auxiliary effect on increasing the grinding speed. These other components may be used alone or in combination of two or more. In addition, from the viewpoint of economical efficiency, its content in the polishing liquid composition is preferably 0.05 to 20% by weight, more preferably 0.05 to 10% by weight, and still more preferably 0.05 to 5% by weight.

In addition, as other components, a bactericide, an antibacterial agent, and the like may be blended as needed. From the point of view of function and impact on polishing performance and economical point of view, the content of these bactericides and antibacterial agents in the polishing liquid composition is preferably 0.0001 to 0.1% by weight, more preferably 0.001 to 0.05% by weight, and particularly preferably It is 0.002 to 0.02% by weight.

Furthermore, the concentration of each component of the polishing liquid composition of the present invention is the preferred concentration during polishing, but may be the concentration during preparation of the composition. Usually, the composition is prepared in the form of a concentrated solution in many cases, and it is diluted before use or at the time of use.

In addition, the polishing liquid composition can be prepared by adding and mixing required components by any method.

The pH of the polishing liquid composition is preferably appropriately determined according to the type and required quality of the object to be polished. From the point of view of increasing the grinding speed and reducing surface waviness, the lower the pH, the better, but from the point of view of the corrosion resistance of the processing machine and the safety of the operator, the pH is preferably close to 7, so when the two are added together, the pH is preferably 0.1 or more and less than 6, more preferably 0.5 or more and less than 5, more preferably 1 or more and less than 4, still more preferably 1 or more and less than 3. The pH of the polishing liquid composition can be adjusted by appropriately matching inorganic acids such as nitric acid and sulfuric acid, organic acids such as hydroxycarboxylic acids, polycarboxylic acids, aminopolycarboxylic acids, amino acids, and metal salts thereof, ammonium salts, ammonia, hydrogen, etc. Sodium oxide, potassium hydroxide, amine and other alkaline substances to adjust.

The manufacturing method of the substrate of the present invention includes the step of polishing the substrate to be polished with the above-mentioned polishing liquid composition.

The substrate to be polished, the magnetic disk substrate, which is the object of the present invention is used as a substrate of a magnetic recording medium. As a specific example of a magnetic disk substrate, the representative one is an aluminum alloy substrate plated with Ni-P alloy. It can also be mentioned that a substrate plated with Ni-P is replaced by glass and glassy carbon, or by plating and vapor deposition of various metals. compound instead of plating Ni-P to coat the substrate.

In above-mentioned lapping process, clamp substrate with the lapping disk that sticks porous organic macromolecule system lapping cloth etc., the grinding liquid composition of the present invention is supplied to the lapping surface of substrate, make lapping disk and substrate rotate while applying pressure, can Grinding the substrate to be ground. Therefore, the present invention relates to a polishing method of a substrate to be polished including the step of polishing the substrate to be polished with the above-mentioned polishing liquid composition. There are no particular limitations on other conditions for polishing (type of polishing machine, polishing temperature, polishing speed, supply amount of polishing liquid, etc.).

The polishing liquid composition of the present invention is particularly effective in the polishing process, but it can also be applied to other polishing processes, such as polishing processes.

Example

The following further illustrates and discloses the mode of the present invention through examples. These examples are just illustrations of the present invention, and do not represent any limitation thereto.

Examples 1-6, Comparative Examples 1-2

1. Preparation of abrasive composition

Mix and stir a given amount of alumina (the average particle size of the secondary particles is 0.2 μm, and the purity is about 99.9%), peroxide, organic acid and other additives, etc., as shown in Table 1, and the balance is ion-exchanged water to prepare Polishing composition.

2. Grinding method

The surface of a substrate composed of a Ni-P-plated aluminum alloy with a thickness of 1.27mm and a diameter of 3.5 inches (95mm) (short-wavelength surface corrugations of 3.8nm and long-wavelength surface corrugations of 1.6nm measured by "Zygo New View 200") was used The double-sided processing machine polished under the setting conditions of the following double-sided processing machine to obtain a polished object of a Ni-P-plated aluminum alloy substrate used as a substrate for a magnetic recording medium.

The setting conditions of the double-sided processing machine are as follows.

<Setting conditions of double-sided processing machine>

Double-sided processing machine: Made by Speedfam, 9B type double-sided processing machine

Processing pressure: 9.8kPa

Polishing pad: "H9900S" (trade name) manufactured by Fujibo Corporation

Fixed plate speed: 50r/min

Supply flow rate of polishing liquid composition: 100ml/min

Grinding time: 4 minutes

The number of boards to put in: 10

3. Evaluation method

(1) Grinding speed

The weight of each substrate before and after polishing was measured with a balance ("BP-210S" manufactured by Sartorius Co., Ltd.), and the weight change of each substrate was obtained. The average value of 10 pieces was used as the amount of decrease, and the value obtained by dividing it by the polishing time was taken as the weight. Reduce speed. The weight reduction rate was introduced into the following formula to convert it into a polishing rate (μm/min). Using the polishing rate of Comparative Example 1 as a reference value 1, relative values (relative speeds) of the polishing rates of the respective Examples and Comparative Examples were obtained.

Weight reduction rate (g/min) = {weight before grinding (g) - weight after grinding (g)}/grinding time (minutes)

Polishing speed (μm/min) = Weight reduction rate (g/min)/Substrate surface area (mm ² )

/Ni-P plating density (g/cm ³ )×1000000

(2) surface corrugation

Each polished substrate was measured under the following conditions.

Machine: Zygo New-View 200 (manufactured by Canon)

Objective lens: 2.5x Michelson

Zoom ratio: 0.5

Move out: Cylinder

Filter: FFT fixed bandpass

-Short wavelength surface ripple: filter high wavelength 50μm

Filter low wavelength 50μm

-Short wavelength surface ripple: filter high wavelength 0.5mm

Filter low wavelength 5mm

Area: 4.33mm×5.77mm

(3) The surface is dirty

The surface of each polished substrate was observed with a polarizing microscope at a magnification of 300, and the following five-level evaluation was performed. Levels 1 and 2 are not practical.

5: No aluminum oxide residues and grinding debris etc. are observed on the surface

4: Only a very small amount is observed

3: A small amount is observed

2: A large amount was observed

1: observed very much

The results are shown in Table 1.

As can be seen from the results in Table 1, the polishing liquid compositions obtained in Examples 1-6, compared with those obtained in Comparative Examples 1-2, have a high polishing rate, and both short-wavelength surface ripples and long-wavelength surface ripples are reduced, and the substrate Surface soiling is also significantly reduced.

The polishing liquid composition of the present invention can be suitably used for producing high-quality magnetic disk substrates such as hard disks.

With the invention thus described, it will be apparent that there are many forms within the same scope. It is considered that such diversity does not depart from the spirit and scope of the invention, and all changes made by those skilled in the art are included within the technical scope of the appended claims.

Claims (12)

1. disk grinding Liquid composition, it contains aluminum oxide, water, superoxide, organic acid and mineral acid, wherein this mineral acid be selected from nitric acid, nitrous acid, sulfuric acid, sulfurous acid and the thionamic acid more than a kind.

2. the described grinding Liquid composition of claim 1, wherein, organic acid is for being selected from sulfur-bearing organic acid, carboxylic acid and phosphorous organic acid more than a kind.

3. the described grinding Liquid composition of claim 1, wherein, composition pH is more than 0.1 and less than 6.

4. the described grinding Liquid composition of claim 2, wherein, composition pH is more than 0.1 and less than 6.

5. ground the Ginding process of substrate, it comprises the operation of using the described grinding Liquid composition grinding of claim 1 to be ground substrate.

6. ground the Ginding process of substrate, it comprises the operation of using the described grinding Liquid composition grinding of claim 2 to be ground substrate.

7. the described method of claim 5 is wherein ground the aluminium alloy base plate of substrate for plating Ni-P alloy.

8. the described method of claim 6 is wherein ground the aluminium alloy base plate of substrate for plating Ni-P alloy.

9. the manufacture method of substrate, it comprises and uses the described grinding Liquid composition of claim 1 to grind the operation of being ground substrate.

10. the manufacture method of substrate, it comprises and uses the described grinding Liquid composition of claim 2 to grind the operation of being ground substrate.

11. the described manufacture method of claim 9 is wherein ground the aluminium alloy base plate of substrate for plating Ni-P alloy.

12. the described manufacture method of claim 10 is wherein ground the aluminium alloy base plate of substrate for plating Ni-P alloy.