WO2018003878A1 - 磁気ディスク基板の製造方法 - Google Patents
磁気ディスク基板の製造方法 Download PDFInfo
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- WO2018003878A1 WO2018003878A1 PCT/JP2017/023804 JP2017023804W WO2018003878A1 WO 2018003878 A1 WO2018003878 A1 WO 2018003878A1 JP 2017023804 W JP2017023804 W JP 2017023804W WO 2018003878 A1 WO2018003878 A1 WO 2018003878A1
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
- G11B5/8404—Processes or apparatus specially adapted for manufacturing record carriers manufacturing base layers
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- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/84—Processes or apparatus specially adapted for manufacturing record carriers
Definitions
- the present disclosure relates to a method for manufacturing a magnetic disk substrate and a method for polishing the substrate.
- the hard disk substrate manufacturing method includes a multi-stage polishing method having two or more polishing steps. Often adopted.
- a polishing composition for finishing containing colloidal silica particles is used in order to satisfy the requirements of reducing surface roughness and scratches such as scratches.
- a polishing liquid composition containing alumina particles and silica particles is used from the viewpoint of improving productivity.
- Patent Documents 1 and 2 disclose a method of manufacturing a magnetic disk substrate that can reduce particle sticking to the substrate by using a polishing liquid composition containing silica particles as abrasive grains in the rough polishing step. Proposed.
- the present disclosure provides a method of manufacturing a magnetic disk substrate that can reduce scratches on the substrate surface after polishing while ensuring a high polishing rate.
- the present disclosure includes a polishing step of polishing a substrate to be polished using a polishing composition containing abrasive grains and water, wherein the abrasive grains are particles having a cutting depth of 5 nm or more and 25 nm or less.
- the depth relates to a method for manufacturing a magnetic disk substrate, which is the depth of a recess that is generated when abrasive grains cut the substrate surface.
- the present disclosure includes a polishing step of polishing a substrate to be polished using a polishing liquid composition containing abrasive grains and water.
- a cutting depth is 5 nm or more and 25 nm or less, and the cutting depth is
- the present invention relates to a method of manufacturing a magnetic disk substrate, which is the depth of a recess that is generated when abrasive grains cut the substrate surface.
- the present disclosure includes polishing a substrate to be polished using a polishing liquid composition containing abrasive grains and water.
- the cutting depth is 5 nm or more and 25 nm or less, and the cutting depth is determined by polishing. It relates to a method for polishing a substrate, wherein the grain is the depth of a recess formed when the substrate surface is cut, and the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate.
- FIG. 1 is an example of a transmission electron microscope (hereinafter also referred to as “TEM”) observation photograph of gold flat sugar type silica particles.
- FIG. 2 is an example of a TEM observation photograph of deformed silica particles.
- FIG. 3 is an example of a TEM observation photograph of precipitated silica particles.
- FIG. 4 is a view for explaining an embodiment of the polishing system.
- FIG. 5 is a diagram for explaining a cutting depth measurement method.
- TEM transmission electron microscope
- the cutting depth in the polishing step is set to a predetermined range, or particles having a cutting depth in the predetermined range are used as abrasive grains, so that a high polishing rate is secured and the substrate surface after polishing is polished. Based on the knowledge that scratches can be reduced. Generally, in the manufacture of a magnetic disk substrate, if the generation of scratches can be suppressed, the substrate yield can be improved. Therefore, according to the present disclosure, it is possible to improve the substrate yield while maintaining the productivity in manufacturing the magnetic disk substrate.
- the present disclosure includes a polishing step of polishing a substrate to be polished using a polishing liquid composition containing abrasive grains and water.
- a cutting depth is 5 nm or more and 25 nm or less, and the cutting depth is
- the present invention relates to a method of manufacturing a magnetic disk substrate (hereinafter also referred to as “manufacturing method according to the present disclosure”), which is the depth of a recess generated when abrasive grains cut the substrate surface.
- the present disclosure includes a polishing step of polishing a substrate to be polished using a polishing liquid composition containing abrasive grains and water, and the abrasive grains are particles having a cutting depth of 5 nm to 25 nm,
- the cutting depth relates to a method for manufacturing a magnetic disk substrate, which is a depth of a recess that is generated when abrasive grains cut the substrate surface. According to the manufacturing method according to the present disclosure, it is possible to achieve an effect that a magnetic disk substrate with reduced scratches can be manufactured with high substrate yield and high productivity while ensuring a high polishing rate.
- a magnetic disk is manufactured through a magnetic layer forming step in which a substrate to be polished that has undergone a grinding step is polished through a rough polishing step and a final polishing step.
- the polishing step of the manufacturing method according to the present disclosure is preferably applied to the rough polishing step from the viewpoint of further improving the final substrate quality.
- scratches on the surface of the substrate can be detected by, for example, an optical microscope, and can be quantitatively evaluated as the number of scratches. Specifically, the number of scratches can be evaluated by the method described in the examples.
- the “cutting depth” refers to the depth of the recess that is generated when abrasive grains cut the substrate surface.
- the “recess” may include a cutting mark, a depression, or a groove.
- the “cutting depth” is, for example, the depth of the concave portion when polishing is performed under such a condition that the abrasive grains are arranged in one layer on the substrate surface, and preferably the abrasive grains are arranged in one layer on the substrate surface. It can be set as the depth of a recessed part when grind
- the “concentration at which the abrasive grains are arranged in a single layer on the substrate surface” is, for example, as shown in FIG. 5, so that a plurality of particles (abrasive grains) are in contact with each other and do not overlap in the substrate thickness direction. It can be calculated as the concentration of particles (abrasive grains) when it is assumed to be disposed on the top.
- the cutting depth can be calculated, for example, by measuring the depth of a concave portion generated when polishing with a polishing machine, a polishing pad, and a polishing load used for polishing, preferably rough polishing.
- the value of the cutting depth is preferably such a concentration that the abrasive grains are arranged in a single layer on the substrate surface when polishing is performed under such conditions that the abrasive grains are arranged in a single layer on the substrate surface. It can be obtained as an average value of the maximum value of the depth of the recess in terms of one abrasive grain on the substrate surface after polishing for a predetermined time (for example, 30 seconds) using the polishing composition, specifically, It can be calculated by the measurement method described in the examples.
- the cutting depth can be measured, for example, by the following steps (i) to (iv).
- a substrate to be polished a substrate that is polished so that the depth of the concave portion on the surface of the substrate is a predetermined depth (for example, 1.0 nm or less) is prepared.
- a polishing liquid for cutting depth measurement having a concentration at which the abrasive grains are arranged in a layer on the substrate surface, for example, an abrasive grain concentration calculated by the following equation, is prepared.
- Abrasive grain concentration (mass%) surface area of polishing pad (cm 2 ) ⁇ [mass per particle (g / piece) / cross sectional area per particle (cm 2 / piece)] / [polishing liquid flow rate ( g / min) ⁇ polishing time (min)] ⁇ 100
- the surface to be polished of the substrate to be polished is polished for a predetermined time (for example, 30 seconds) using a polishing liquid for cutting depth.
- polishing conditions include the conditions described in the examples.
- (Iv) The average value of the maximum depths of the recesses in terms of one abrasive grain on the substrate surface after polishing is calculated as the cutting depth.
- the average value of the maximum depth of the recesses in terms of one abrasive particle can be measured by the method described in the examples described later.
- the cutting depth is 5 nm or more, preferably 6 nm or more, more preferably 7 nm or more, from the viewpoint of improving the polishing rate, and more preferably 25 nm or less from the viewpoint of scratch reduction. And, 15 nm or less is preferable and 9 nm or less is more preferable. In an embodiment, the cutting depth is 5 nm or more and 25 nm or less, preferably 6 nm or more and 15 nm or less, and more preferably 7 nm or more and 15 nm or less from the viewpoint of improving the polishing rate and reducing scratches.
- the cutting depth is 5 nm or more and 25 nm or less, preferably 5 nm or more and 9 nm or less, or 10 nm or more and 25 nm or less, and preferably 6 nm or more and 9 nm or less or 10 nm in other embodiments from the viewpoint of improving the polishing rate and reducing scratches. It is more preferably 20 nm or less, and further preferably 7 nm or more and 9 nm or less, or 10 nm or more and 17 nm or less.
- polishing liquid composition I used in the polishing step of the production method according to the present disclosure contains abrasive grains and water.
- the abrasive grain in polishing liquid composition I the abrasive grain whose cutting depth becomes the range mentioned above is mentioned, for example.
- the use form of the abrasive grains include powder and slurry (dispersion liquid). From the viewpoint of ease of production of the polishing composition I, the slurry is preferable. Accordingly, the present disclosure relates to an abrasive for polishing a magnetic disk substrate, wherein the abrasive is a particle having a cutting depth of 5 nm to 25 nm. Furthermore, the present disclosure relates to a slurry (dispersion) containing abrasive grains for polishing a magnetic disk substrate, wherein the abrasive grains are particles having a cutting depth of 5 nm to 25 nm.
- Examples of the abrasive grains include alumina particles and silica particles, and silica particles are preferable from the viewpoint of improving the polishing rate and reducing scratches.
- Examples of the silica particles include colloidal silica, precipitated silica, fumed silica, pulverized silica, and silica obtained by surface modification thereof, and colloidal silica is preferable from the viewpoint of improving the polishing rate and reducing scratches.
- the colloidal silica is, for example, a method based on particle growth using an aqueous alkali silicate solution (hereinafter also referred to as “water glass method”) and a method based on condensation of an alkoxysilane hydrolyzate (hereinafter referred to as “sol-gel method”). From the viewpoint of ease of production and economy, and preferably obtained by the water glass method. Silica particles obtained by the water glass method and the sol-gel method can be produced by a conventionally known method.
- the precipitated silica is silica particles obtained by a precipitation method, and the production method will be described later.
- the silica particles contained as the abrasive grains may be calcined silica or crushed calcined silica (hereinafter collectively referred to as “calcined silica”).
- the fired silica include those obtained by firing the above-described silica (excluding colloidal silica). Crushing refers to loosening and breaking up a mass of fine particles.
- the content of the baked silica in the abrasive grains is preferably less than 50% by mass, more preferably 30% by mass or less, and still more preferably 15% by mass or less, from the viewpoint of improving the polishing rate and reducing scratches.
- Non-spherical silica particle A The abrasive grains preferably contain non-spherical silica particles A (hereinafter also referred to as “particles A”) as silica particles.
- particles A include particles whose cutting depth is within the above-described range.
- the average sphericity of the particles A is preferably 0.60 or more, more preferably 0.63 or more, and preferably 0.85 or less, preferably 0.80 or less, from the viewpoint of improving the polishing rate and reducing scratches. .75 or less is more preferable.
- the average sphericity of the particles A is an average value of the sphericity of at least 500 particles A contained in the polishing liquid composition I.
- the sphericity of each particle A is preferably 0.60 or more, more preferably 0.63 or more, and preferably 0.85 or less, more preferably 0.80 or less, from the viewpoint of improving the polishing rate and reducing scratches. 0.75 or less is more preferable.
- the average minor axis of the particles A is preferably 100 nm or more, more preferably 110 nm or more, still more preferably 150 nm or more, still more preferably 180 nm or more, and even more preferably 500 nm or less from the viewpoint of scratch reduction. Preferably, it is 450 nm or less, more preferably 420 nm or less, still more preferably 400 nm or less, still more preferably 350 nm or less, still more preferably 300 nm or less, and even more preferably 250 nm or less.
- the average minor axis of the particle A is an average value of the minor axis of at least 500 particles A contained in the polishing liquid composition I.
- the minor axis of the particle A is the length of the short side of the rectangle when a minimum rectangle circumscribing the projected image of the particle A is drawn using, for example, TEM observation and image analysis software.
- the BET specific surface area of the particles A from the viewpoint of improving the polishing rate and reducing scratches, preferably 50 m 2 / g or less, more preferably 40 m 2 / g, still more preferably 30 m 2 / g or less, and, 5 m 2 / g
- the above is preferable, 10 m 2 / g or more is more preferable, 20 m 2 / g or more is more preferable, and 25 m 2 / g or more is more preferable.
- the BET specific surface area can be calculated by a nitrogen adsorption method (hereinafter also referred to as “BET method”). Specifically, it can be calculated by the measurement method described in the examples.
- the average primary particle diameter D1A of the particles A is preferably 60 nm or more, more preferably 70 nm or more, more preferably 75 nm or more, still more preferably 80 nm or more, and preferably 250 nm or less from the viewpoint of improving the polishing rate and reducing scratches. 220 nm or less is more preferable, 200 nm or less is further preferable, and 180 nm or less is still more preferable.
- the average secondary particle diameter D2A of the particles A is preferably 150 nm or more, more preferably 160 nm or more, further preferably 170 nm or more, further preferably 180 nm or more, and 580 nm or less from the viewpoint of improving the polishing rate and reducing scratches.
- 500 nm or less is more preferable, 400 nm or less is further preferable, 350 nm or less is further preferable, 300 nm or less is further preferable, 250 nm or less is further preferable, and 200 nm or less is further preferable.
- the average secondary particle diameter D2 A particle A refers to the average particle diameter on a volume basis, based on the scattering intensity distribution measured by a dynamic light scattering method.
- the “scattering intensity distribution” means a particle size distribution in terms of volume of sub-micron particles or less determined by dynamic light scattering (DLS) or quasielastic light scattering (QLS). I mean.
- the average secondary particle diameter D2 A of particles A in the present disclosure is specifically can be obtained by the method described in Examples.
- the shape of the particle A is a shape in which a plurality of precursor particles are aggregated or fused with a silica particle having a particle size smaller than the secondary particle size of the particle A as a precursor particle from the viewpoint of improving the polishing rate and reducing scratches. It is.
- the kind of particles A is preferably at least one kind of silica particles selected from confetti type silica particles Aa, irregular shape silica particles Ab, irregular and confetti type silica particles Ac, and precipitated silica Ad.
- the irregular-shaped silica particles Ab and the precipitated silica particles Ad are more preferable.
- the particle A may be one type of non-spherical silica particle or a combination of two or more types of non-spherical silica particles.
- confetti-type silica particles Aa refer to silica particles having unique ridge-like projections on the surface of spherical particles (see FIG. 1).
- the particle Aa preferably has a shape in which the largest precursor particle a1 and one or more precursor particles a2 having a particle size of 1/5 or less of the precursor particle a1 are aggregated or fused.
- the particles Aa are preferably in a state in which a plurality of precursor particles a2 having a small particle size are partially embedded in one precursor particle a1 having a large particle size.
- the particles Aa can be obtained, for example, by the method described in JP-A-2008-137822.
- the particle diameter of the precursor particles can be obtained as the equivalent circle diameter measured in one precursor particle in an observation image by TEM or the like, that is, the major axis of a circle having the same area as the projected area of the precursor particles.
- the particle diameters of the precursor particles in the irregular-shaped silica particles Ab and the irregular-shaped and confetti-shaped silica particles Ac can also be determined in the same manner.
- irregular-shaped silica particles Ab have a shape in which two or more precursor particles, preferably two or more and ten or less precursor particles are aggregated or fused. This refers to silica particles (see FIG. 2).
- the particle Ab preferably has a shape in which two or more precursor particles having a particle size of 1.5 times or less are aggregated or fused on the basis of the particle size of the smallest precursor particle.
- the particles Ab can be obtained, for example, by the method described in JP-A-2015-86102.
- irregular and confetti-type silica particles Ac (hereinafter also referred to as “particles Ac”) have the particle Ab as the precursor particle c1, the largest precursor particle c1, and the particle size of the precursor particle c1. It is a shape in which one or more precursor particles c2 which are 1/5 or less are aggregated or fused.
- Examples of the method for producing the particles Aa, the particles Ab, and the particles Ac include a water glass method, a sol-gel method, and a pulverization method, and the water glass method is preferable from the viewpoint of improving the polishing rate and reducing scratches.
- sedimentation method silica particles Ad refer to silica particles produced by the precipitation method.
- the shape of the particles Ad is preferably a shape in which a plurality of primary particles are aggregated from the viewpoint of improving the polishing rate and reducing scratches, and a shape in which a plurality of primary particles having a relatively large particle size is aggregated as shown in FIG. More preferred.
- Examples of the method for producing the particle Ad include known methods such as the method described in Tosoh Research and Technical Report Vol. 45 (2001) pages 65 to 69.
- Specific examples of the method for producing the particles Ad include a precipitation method in which silica particles are precipitated by a neutralization reaction between a silicate such as sodium silicate and a mineral acid such as sulfuric acid. It is preferable that the neutralization reaction is performed at a relatively high temperature and under alkaline conditions, whereby the primary particle growth of silica proceeds rapidly, and the primary particles aggregate in a floc form and settle, preferably further pulverized. By doing so, the particle Ad is obtained.
- the particle A preferably includes at least one selected from the particles Aa, Ab, Ac and Ad, and more preferably includes at least one selected from the particle Ab and the particle Ad from the viewpoint of improving the polishing rate and reducing scratches.
- the total amount of the particles Aa, Ab, Ac and Ad in the particles A is preferably 50% by mass or more, more preferably 70% by mass or more, and still more preferably 80% by mass or more, from the viewpoint of improving the polishing rate and reducing scratches. 90 mass% or more is still more preferable, and substantially 100 mass% is still more preferable.
- the content of the particles A in the polishing liquid composition I is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and more preferably 1% by mass or more from the viewpoint of improving the polishing rate and reducing scratches. 2 mass% or more is still more preferable, and from a viewpoint of economical efficiency, 30 mass% or less is preferable, 25 mass% or less is more preferable, and 20 mass% or less is still more preferable.
- the polishing liquid composition I contains the particles A as abrasive grains, it can preferably further contain spherical silica particles B (hereinafter also referred to as “particles B”) as abrasive grains.
- particles B include particles whose cutting depth is within the above-described range.
- the average sphericity of the particles B is preferably 0.85 or more, more preferably 0.87 or more, from the viewpoint of improving the polishing rate and scratch reduction, and from the same viewpoint, 1.00 or less is preferable, and 0.95 The following is more preferable.
- the sphericity of each particle B is preferably 0.85 or more, more preferably 0.87 or more, and preferably 1.00 or less, more preferably 0.95 or less.
- the average sphericity and sphericity of the particle B can be calculated by the same method as the particle A.
- the average minor axis of the particles B is preferably 20 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, and more preferably 200 nm or less, and more preferably 150 nm or less, from the viewpoint of scratch reduction, from the viewpoint of improving the polishing rate. 110 nm or less is more preferable.
- the average minor axis of the particle B can be calculated by the same method as that for the particle A.
- the average minor axis of the particles A is preferably larger than the average minor axis of the particles B from the viewpoint of improving the polishing rate and reducing scratches.
- the ratio of the average minor axis of particle A to the average minor axis of particle B in polishing liquid composition I (average minor axis of particle A) / (average minor axis of particle B) is from the viewpoint of improving the polishing rate and reducing scratches.
- the average primary particle diameter D1 B of the particles B is preferably 20 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, from the viewpoint of polishing rate improvement and scratch reduction, and from the same viewpoint, 150 nm or less is preferable. 120 nm or less is more preferable, and 100 nm or less is still more preferable.
- the average primary particle diameter D1 B of the particle B can be calculated by the same method as the particle A.
- the average secondary particle diameter D2B of the particles B is preferably 20 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, and preferably 200 nm or less from the viewpoint of improving the polishing rate and reducing scratches. 150 nm or less is more preferable, and 120 nm or less is still more preferable.
- the average secondary particle diameter D1 B of the particle B can be calculated by the same measurement method as that for the particle A.
- the particles B include colloidal silica, fumed silica, and surface-modified silica.
- the particle B for example, commercially available colloidal silica may be applicable. From the viewpoint of improving the polishing rate and reducing scratches, the particle B is preferably colloidal silica.
- the particle B may be one type of spherical silica particle or a combination of two or more types of spherical silica particles.
- Examples of the method for producing the particles B include a water glass method, a sol-gel method, and a pulverization method, and the water glass method is preferable from the viewpoint of improving the polishing rate and reducing scratches.
- the usage form of the particles B is preferably a slurry.
- the content of the particles B in the polishing liquid composition I is preferably 0.5% by mass or more, more preferably 1.0% by mass or more, and more preferably 1.5% by mass or more from the viewpoint of improving the polishing rate and reducing scratches. Further, from the viewpoint of economy, it is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less.
- the ratio A / B (mass ratio) of the content of the particles A to the content of the particles B in the polishing liquid composition I is the polishing rate. From the viewpoint of improvement and scratch reduction, 10/90 or more is preferable, 15/85 or more is more preferable, 25/75 or more is more preferable, and from the same viewpoint, 99/1 or less is preferable, and 90/10 or less is preferable. More preferred is 75/25 or less.
- the particle A is a combination of two or more types of spherical silica particles
- the content of the particle A refers to the total content thereof. The same applies to the content of the particles B.
- the other abrasive grains in the polishing composition I contain abrasive grains other than the particles A and B
- the other abrasive grains include, for example, particles whose cutting depth is in the above-described range. Is mentioned.
- the total content of the particles A and the particles B with respect to the entire abrasive grains in the polishing liquid composition I is preferably 98.0% by mass or more, and 98.5% by mass or more from the viewpoint of improving the polishing rate and reducing scratches. Is more preferable, 99.0 mass% or more is further preferable, 99.5 mass% or more is further more preferable, 99.8 mass% or more is further more preferable, and substantially 100 mass% is still more preferable.
- Polishing liquid composition I may contain a pH adjuster from a viewpoint of improving polishing rate, reducing scratches, and adjusting pH.
- the pH adjuster is preferably at least one selected from acids and salts from the same viewpoint.
- Examples of the acid include nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid, amidosulfuric acid, phosphoric acid, polyphosphoric acid, phosphonic acid, and other inorganic acids; organic phosphoric acid, organic phosphonic acid, and other organic acids; etc. Is mentioned.
- at least one selected from phosphoric acid, sulfuric acid, and 1-hydroxyethylidene-1,1-diphosphonic acid is preferable, and at least one selected from sulfuric acid and phosphoric acid is more preferable.
- phosphoric acid is more preferable.
- the salt examples include a salt of the above acid and at least one selected from metals, ammonia, and alkylamines.
- Specific examples of the metal include metals belonging to Groups 1 to 11 of the periodic table.
- a salt of the above acid with a metal belonging to Group 1 or ammonia is preferable from the viewpoint of improving the polishing rate and reducing scratches.
- the content of the pH adjusting agent in the polishing liquid composition I is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, and more preferably 0.05% by mass or more from the viewpoint of improving the polishing rate and reducing scratches. Is more preferably 0.1% by mass or more, and from the same viewpoint, 5.0% by mass or less is preferable, 4.0% by mass or less is more preferable, and 3.0% by mass or less is more preferable. 2.5% by mass or less is even more preferable.
- the polishing composition I may contain an oxidizing agent from the viewpoint of improving the polishing rate and reducing scratches.
- the oxidizing agent include peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, peroxo acid or a salt thereof, oxygen acid or a salt thereof, and the like from the same viewpoint.
- at least one selected from hydrogen peroxide, iron nitrate (III), peracetic acid, ammonium peroxodisulfate, iron sulfate (III) and ammonium iron sulfate (III) is preferable. From the viewpoint of preventing metal ions from adhering to the surface and the availability, hydrogen peroxide is more preferable.
- These oxidizing agents may be used alone or in admixture of two or more.
- the content of the oxidizing agent in the polishing liquid composition I is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and more preferably 0.1% by mass or more from the viewpoint of improving the polishing rate and reducing scratches. Further, from the same viewpoint, it is preferably 4.0% by mass or less, more preferably 2.0% by mass or less, and further preferably 1.5% by mass or less.
- Polishing liquid composition I contains water as a medium.
- Examples of water include distilled water, ion exchange water, pure water, and ultrapure water.
- the content of water in the polishing liquid composition I is preferably 61% by mass or more, more preferably 70% by mass or more, still more preferably 80% by mass or more, from the viewpoint of easy handling of the polishing liquid composition. From the same viewpoint, 99% by mass or less is preferable, 98% by mass or less is more preferable, and 97% by mass or less is still more preferable.
- Polishing liquid composition I may contain another component as needed.
- other components include thickeners, dispersants, rust inhibitors, basic substances, polishing rate improvers, surfactants, and polymer compounds.
- the other components are preferably blended in the polishing liquid composition I as long as the effects of the present disclosure are not impaired.
- the content of the other components in the polishing liquid composition I is 0% by mass or more. Preferably, more than 0% by mass is more preferable, 0.01% by mass or more is further preferable, 10% by mass or less is preferable, and 5% by mass or less is more preferable.
- the content of alumina abrasive grains is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, and 0.02 It is more preferable that the amount is not more than mass%, and it is further preferable that the alumina abrasive grains are not substantially contained.
- substantially free of alumina abrasive grains means that no alumina particles are contained, no alumina particles functioning as abrasive grains, or an amount of alumina particles that affect the polishing result. May not be included.
- the content of alumina particles in the polishing liquid composition I is preferably 5% by mass or less, more preferably 2% by mass or less, still more preferably 1% by mass or less, based on the total amount of abrasive grains in the polishing liquid composition I. Even more preferably, it is substantially 0% by weight.
- the pH of the polishing composition I is preferably 0.5 or more, more preferably 0.7 or more, still more preferably 0.9 or more, and even more preferably 1.0 or more, from the viewpoint of improving the polishing rate and reducing scratches.
- 1.2 or more is even more preferable, 1.4 or more is still more preferable, and from the same viewpoint, 6.0 or less is preferable, 4.0 or less is more preferable, 3.0 or less is more preferable, 2.5 or less is even more preferable, and 2.0 or less is even more preferable.
- the pH is preferably adjusted using the aforementioned acid or a known pH adjuster.
- the above pH is the pH of the polishing liquid composition at 25 ° C. and can be measured using a pH meter, and is preferably a value 30 seconds after the electrode of the pH meter is immersed in the polishing liquid composition.
- the polishing liquid composition I can be prepared, for example, by blending the particles A and water and, if desired, at least one selected from the particles B, a pH adjuster, an oxidizing agent and other components by a known method. .
- the polishing liquid composition I can be formed by blending at least the particles A and water.
- “mixing” includes mixing the particles A and water, and if necessary, the particles B, a pH adjuster, an oxidizing agent and other components simultaneously or in any order.
- blending can be performed using mixers, such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill, for example.
- the compounding amount of each component in the preparation of the polishing liquid composition I can be the same as the content of each component in the polishing liquid composition I described above.
- the “content of each component in the polishing liquid composition” refers to the content of each component at the time when the polishing liquid composition is used for polishing. Therefore, when the polishing liquid composition I is prepared as a concentrate, the content of each component can be increased by the concentrated amount.
- the substrate to be polished in the present disclosure is a substrate used for manufacturing a magnetic disk substrate, for example, a Ni—P plated aluminum alloy substrate.
- the “Ni—P plated aluminum alloy substrate” refers to a surface of an aluminum alloy base material that has been subjected to electroless Ni—P plating after being ground.
- a magnetic disk can be manufactured by performing a step of forming a magnetic layer on the substrate surface by sputtering or the like.
- Examples of the shape of the substrate to be polished include a shape having a flat portion such as a disk shape, a plate shape, a slab shape, and a prism shape, and a shape having a curved surface portion such as a lens. is there.
- a disk-shaped substrate to be polished its outer diameter is, for example, 10 to 120 mm, and its thickness is, for example, 0.5 to 2 mm.
- the substrate to be polished is sandwiched between a surface plate to which a polishing pad is attached, the polishing composition I is supplied to the polishing surface, and the polishing pad or the polishing target is applied while applying pressure.
- the substrate to be polished is polished by moving the substrate.
- the polishing step in the present disclosure can include adjusting the polishing conditions so that the cutting depth is within the above-described range. For example, in the polishing load of 3 kPa to 30 kPa, the cutting depth is within the above-described range. Selecting the abrasive grains to be.
- the polishing load in the polishing step is preferably 30 kPa or less, more preferably 25 kPa or less, still more preferably 20 kPa or less, still more preferably 18 kPa or less, even more preferably 16 kPa or less, and even more preferably 14 kPa or less, from the viewpoint of polishing rate and scratch reduction. Is more preferably 3 kPa or more, more preferably 5 kPa or more, still more preferably 7 kPa or more, still more preferably 8 kPa or more, and even more preferably 9 kPa or more.
- polishing load refers to the pressure of the surface plate applied to the surface to be polished of the substrate to be polished during polishing. The polishing load can be adjusted by applying air pressure or weight to the surface plate or the substrate.
- the polishing amount per 1 cm 2 of the substrate to be polished is preferably 0.20 mg or more, more preferably 0.30 mg or more, further preferably 0.40 mg or more, from the viewpoint of improving the polishing rate and reducing scratches. From the same viewpoint, it is preferably 2.50 mg or less, more preferably 2.00 mg or less, and even more preferably 1.60 mg or less.
- the supply rate of the polishing liquid composition I per 1 cm 2 of the substrate to be polished is preferably 0.25 mL / min or less, more preferably 0.20 mL / min or less, and 0.15 mL from the viewpoint of economy.
- / Min or less is more preferable, 0.10 mL / min or less is still more preferable, and from the viewpoint of improving the polishing rate, 0.01 mL / min or more is preferable, 0.03 mL / min or more is more preferable, 0.05 mL / min More than minutes are more preferable.
- the polishing step as a method of supplying the polishing composition I to the polishing machine, for example, a method of continuously supplying using a pump or the like can be mentioned.
- a method of continuously supplying using a pump or the like can be mentioned.
- the polishing liquid composition I to the polishing machine in addition to the method of supplying it with one liquid containing all components, considering the storage stability of the polishing liquid composition, etc. Divided into two or more liquids. In the latter case, for example, the plurality of compounding component liquids are mixed in the supply pipe or on the substrate to be polished to obtain the polishing liquid composition I in the present disclosure.
- the present disclosure includes polishing a substrate to be polished using a polishing liquid composition containing abrasive grains and water.
- the cutting depth is 5 nm or more and 25 nm or less, and the cutting depth is determined by polishing.
- the depth of the concave portion generated when the grain cuts the surface of the substrate, and the substrate to be polished is a substrate used for manufacturing a magnetic disk substrate (hereinafter, “polishing method according to the present disclosure”). Also called).
- polishing method according to the present disclosure it is possible to produce a magnetic disk substrate with reduced scratches with high substrate yield and high productivity while ensuring a high polishing rate.
- the specific polishing method and conditions can be the same as those of the manufacturing method according to the present disclosure described above.
- the polishing method according to the present disclosure is preferably applied to the rough polishing step from the viewpoint of further improving the final substrate quality.
- the manufacturing method and the polishing method according to the present disclosure include a first polishing machine 1 that performs a rough polishing process, a cleaning unit 2 that performs a cleaning process, and a second polishing machine that performs a final polishing process, as shown in FIG. 3 can be performed by a magnetic disk substrate polishing system.
- the present disclosure includes a polishing machine 1 that polishes (roughly polishes) a substrate to be polished using the polishing liquid composition I according to the present disclosure, a cleaning unit 2 that cleans the substrate polished by the polishing machine 1, and a polishing liquid composition.
- the present invention relates to a polishing system for a magnetic disk substrate including a polishing machine 3 for polishing (finish polishing) a substrate after cleaning using an object II.
- the polishing composition II used in the finish polishing preferably contains silica particles as abrasive grains from the viewpoint of reducing protrusion defects after the finish polishing.
- the silica particles are preferably colloidal silica from the viewpoint of reducing long-wave waviness after finish polishing. It is preferable that the polishing composition II used for finish polishing does not substantially contain alumina abrasive grains from the viewpoint of reducing protrusion defects after finish polishing.
- “long wavelength undulation” refers to undulation observed with a wavelength of 500 to 5000 ⁇ m.
- Polishing liquid composition I was prepared as follows, and the substrate to be polished was polished under the following conditions.
- the preparation method of the polishing liquid composition I, the additive used, the measurement method of each parameter, the polishing conditions (polishing method) and the evaluation method are as follows.
- polishing liquid composition I Using the abrasive grains (non-spherical silica particles A, spherical silica particles B, alumina abrasive grains), acid (phosphoric acid), oxidizing agent (hydrogen peroxide), and water described in Table 1, Polishing liquid compositions I of Examples 1 to 6 and Comparative Examples 1 to 14 shown in Table 3 were prepared.
- the content of each component in each polishing liquid composition I was abrasive grains: 5 mass%, phosphoric acid: 1.5 mass%, and hydrogen peroxide: 0.8 mass%.
- the pH of each polishing composition I was 1.6.
- the types of non-spherical silica particles A used for the abrasive grains were irregular-shaped silica particles and precipitated silica particles.
- the irregular-shaped silica particles A1, 2, and 8 to 10 are those produced by the water glass method (colloidal silica)
- the irregular-shaped silica particles A7 are those produced by the sol-gel method (colloidal).
- Silica and the precipitated silica particles of A3 to 6 are produced by the precipitation method.
- the spherical silica particles B used for the abrasive grains are those produced by the water glass method (colloidal silica).
- the pH was measured using a pH meter (manufactured by Toa DKK Corporation), and the value after 30 seconds after the electrode was immersed in the polishing composition was adopted (hereinafter the same).
- Polishing test Polishing of the substrate to be polished was performed according to the following steps (1) and (2). The conditions for each step are shown below.
- the substrate to be polished was an aluminum alloy substrate plated with Ni—P. This substrate to be polished had a thickness of 1.27 mm and a diameter of 95 mm.
- Polishing machine Double-side polishing machine (9B-type double-side polishing machine, manufactured by Speed Fam Co., Ltd.) Number of substrates to be polished: 10 polishing liquids: polishing liquid compositions I of Examples 1 to 9 and Comparative Examples 1 to 17 Polishing pad: Suede type (foamed layer: polyurethane elastomer), thickness: 1.0 mm, average pore diameter: 30 ⁇ m, compression ratio of surface layer: 2.5% (“CR200” manufactured by Filwel) Plate rotation speed: 35 rpm Polishing load: set values described in Tables 3 to 4 Polishing liquid supply amount: 100 mL / min (corresponding to 0.076 mL / min per 1 cm 2 of substrate surface to be polished) Polishing time: 6 minutes
- Step (2) Cleaning
- the substrate obtained in the step (1) was washed under the following conditions. First, the substrate obtained in the step (1) is immersed for 5 minutes in a bath containing an alkaline detergent composition having a pH of 12 consisting of a 0.1% by mass aqueous KOH solution. Next, the substrate after immersion is rinsed with ion exchange water for 20 seconds. Then, the rinsed substrate is transferred to a scrub cleaning unit on which a cleaning brush is set and cleaned.
- the cutting depth was measured by the following measuring method. First, using a substrate similar to the substrate to be polished used in the above-described polishing test, rough polishing and finish polishing are performed by a publicly known method, and a substrate in which the depth of the concave portion on the substrate surface is 1.0 nm or less is previously determined. Produced. The depth of the recesses on the surface of the produced substrate was measured using a light interference type surface shape measuring instrument “OptiFLAT III” (manufactured by KLA Tencor) under the cutting depth measurement conditions described later.
- Examples 1 to 9 and Comparative Examples 1 to 17 shown in Tables 3 to 4 were performed except that the abrasive concentration was the amount described in Table 2 and the polishing time was 30 seconds. Polishing was performed under the same conditions as in (1). Specific polishing conditions are shown below.
- the abrasive grain concentration was such that the abrasive grains were arranged in a single layer on the substrate surface, and was calculated by the following method.
- the average value of the maximum depth of the recesses in terms of one abrasive grain on the substrate surface after polishing was calculated as the cutting depth.
- Polishing machine Double-side polishing machine (9B-type double-side polishing machine, manufactured by Speed Fam Co.) Polishing pad: “CR200” manufactured by Filwel Number of substrates: 4 Polishing load: Set values described in Tables 3 to 4 (3.6 to 19.3 kPa) Plate rotation speed: 35 rpm Polishing liquid flow rate: 100 mL / min (corresponding to 0.190 mL / min per 1 cm 2 of substrate surface) Polishing time: 30 seconds
- the cutting depth refers to the depth of the recess when polished under conditions such that abrasive grains (particles) are arranged in a single layer on the substrate surface.
- the said conditions can be set by adjusting the density
- concentration of the abrasive grains in polishing liquid composition were arranged on the polishing pad so that a plurality of abrasive grains (particles) are in contact with each other and do not overlap in the substrate thickness direction, as shown in FIG.
- the concentration of the abrasive grains in the polishing liquid composition was calculated based on the following formula. The calculated values are shown in Table 2.
- Optical interference type surface shape measuring instrument “OptiFLAT III” (manufactured by KLA Tencor) Radius Inside / Out: 14.87mm / 47.83mm Center X / Y: 55.44mm / 53.38mm Low Cutoff: 2.5mm Inner Mask: 18.50mm Outer Mask: 45.5mm Long Period: 2.5mm Wa Correction: 0.9 Rn Correction: 1.0 No Zernike Terms: 8
- polishing rate Evaluation 20 mg / min or more: “A: The polishing rate is good and the substrate yield can be expected to improve” 10 mg / min or more and less than 20 mg / min: “B: Improvement is required for actual production” Less than 10 mg / min: “C: substrate yield is greatly reduced”
- scratches can be reduced while ensuring a high polishing rate, so that the substrate yield can be improved while improving the productivity of manufacturing the magnetic disk substrate.
- the present disclosure can be suitably used for manufacturing a magnetic disk substrate.
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- Manufacturing Of Magnetic Record Carriers (AREA)
- Finish Polishing, Edge Sharpening, And Grinding By Specific Grinding Devices (AREA)
Abstract
Description
切削深さは、例えば、以下の工程(i)~工程(iv)により測定することができる。
(i)被研磨基板として、基板表面の凹部の深さが所定の深さ(例えば、1.0nm以下)になるよう研磨された基板を準備する。
(ii)砥粒が基板表面上に一層に配置されるような濃度、例えば、下記式により算出される砥粒濃度の切削深さ測定用研磨液を準備する。
[砥粒濃度の算出方法]
粒子1個換算の質量(g/個)=1個換算の体積(cm3/個)×粒子の比重(g/cm3)
粒子1個換算の断面積=π×[平均二次粒子径(cm)/2]2
砥粒濃度(質量%)=研磨パッドの表面積(cm2)×[粒子1個換算の質量(g/個)/粒子1個換算の断面積(cm2/個)]/[研磨液流量(g/min)×研磨時間(min)]×100
(iii)切削深さ用研磨液を用いて被研磨基板の研磨対象面を所定時間(例えば、30秒間)研磨する。研磨条件としては、例えば、実施例に記載の条件が挙げられる。
(iv)研磨後の基板表面における、砥粒粒子1個換算の凹部の深さの最大値の平均値を切削深さとして算出する。砥粒粒子1個換算の凹部の深さの最大値の平均値は、後述する実施例に記載の方法により測定できる。
本開示に係る製造方法の研磨工程に使用する研磨液組成物(以下、「研磨液組成物I」ともいう)は、砥粒及び水を含有する。
研磨液組成物I中の砥粒は、例えば、切削深さが上述した範囲となる砥粒が挙げられる。砥粒の使用形態としては、例えば、粉末状やスラリー状(分散液)が挙げられ、研磨液組成物Iの製造容易性の観点から、スラリー状が好ましい。したがって、本開示は、磁気ディスク基板研磨用の砥粒であって、前記砥粒は、切削深さが5nm以上25nm以下となる粒子である、砥粒に関する。さらに、本開示は、磁気ディスク基板研磨用砥粒を含むスラリー(分散液)であって、前記砥粒は、切削深さが5nm以上25nm以下となる粒子である、スラリー(分散液)に関する。
前記砥粒は、シリカ粒子として、好ましくは非球状シリカ粒子A(以下、「粒子A」ともいう)を含有する。粒子Aとしては、例えば、切削深さが上述した範囲内となる粒子が挙げられる。
球形度=4π×S/L2
平均一次粒子径(nm)=2727/S
研磨液組成物Iは、砥粒として前記粒子Aを含有する場合、好ましくは砥粒として球状シリカ粒子B(以下、「粒子B」ともいう)をさらに含有することができる。粒子Bは、例えば、切削深さが上述した範囲内となる粒子が挙げられる。
研磨液組成物Iは、研磨速度向上、スクラッチ低減、及び、pHを調整する観点から、pH調整剤を含有してもよい。pH調整剤としては、同様の観点から、酸及び塩から選ばれる少なくとも1種が好ましい。
研磨液組成物Iは、研磨速度向上及びスクラッチ低減の観点から、酸化剤を含有してもよい。酸化剤としては、例えば、同様の観点から、過酸化物、過マンガン酸又はその塩、クロム酸又はその塩、ペルオキソ酸又はその塩、酸素酸又はその塩等が挙げられる。これらの中でも、過酸化水素、硝酸鉄(III)、過酢酸、ペルオキソ二硫酸アンモニウム、硫酸鉄(III)及び硫酸アンモニウム鉄(III)から選ばれる少なくとも1種が好ましく、研磨速度向上の観点、被研磨基板の表面に金属イオンが付着しない観点、及び入手容易性の観点から、過酸化水素がより好ましい。これらの酸化剤は、単独で又は2種以上を混合して使用してもよい。
研磨液組成物Iは、媒体として水を含有する。水としては、蒸留水、イオン交換水、純水及び超純水等が挙げられる。研磨液組成物I中の水の含有量は、研磨液組成物の取扱いが容易になる観点から、61質量%以上が好ましく、70質量%以上がより好ましく、80質量%以上が更に好ましく、85質量%以上が更により好ましく、そして、同様の観点から、99質量%以下が好ましく、98質量%以下がより好ましく、97質量%以下が更に好ましい。
研磨液組成物Iは、必要に応じてその他の成分を含有してもよい。他の成分としては、増粘剤、分散剤、防錆剤、塩基性物質、研磨速度向上剤、界面活性剤、高分子化合物等が挙げられる。前記その他の成分は、本開示の効果を損なわない範囲で研磨液組成物I中に配合されることが好ましく、研磨液組成物I中の前記その他の成分の含有量は、0質量%以上が好ましく、0質量%超がより好ましく、0.01質量%以上が更に好ましく、そして、10質量%以下が好ましく、5質量%以下がより好ましい。
研磨液組成物Iは、アルミナ粒子の基板への突き刺さりを低減させたい場合、アルミナ砥粒の含有量が、0.1質量%以下が好ましく、0.05質量%以下がより好ましく、0.02質量%以下が更に好ましく、アルミナ砥粒を実質的に含まないことが更に好ましい。本開示において「アルミナ砥粒を実質的に含まない」とは、アルミナ粒子を含まないこと、砥粒として機能する量のアルミナ粒子を含まないこと、又は、研磨結果に影響を与える量のアルミナ粒子を含まないこと、を含みうる。研磨液組成物I中のアルミナ粒子の含有量は、研磨液組成物I中の砥粒全量に対し、5質量%以下が好ましく、2質量%以下がより好ましく、1質量%以下が更に好ましく、実質的に0質量%であることが更により好ましい。
研磨液組成物IのpHは、研磨速度の向上及びスクラッチ低減の観点から、0.5以上が好ましく、0.7以上がより好ましく、0.9以上が更に好ましく、1.0以上が更により好ましく、1.2以上が更により好ましく、1.4以上が更により好ましく、そして、同様の観点から、6.0以下が好ましく、4.0以下がより好ましく、3.0以下が更に好ましく、2.5以下が更により好ましく、2.0以下が更により好ましい。pHの調整は、前述の酸や公知のpH調整剤を用いて、調整することが好ましい。上記のpHは、25℃における研磨液組成物のpHであり、pHメータを用いて測定でき、好ましくは、pHメータの電極を研磨液組成物へ浸漬して30秒後の数値である。
研磨液組成物Iは、例えば、粒子A及び水と、更に所望により、粒子B、pH調整剤、酸化剤及びその他の成分から選ばれる少なくとも1種とを公知の方法で配合することにより調製できる。例えば、研磨液組成物Iは、少なくとも粒子A及び水を配合してなるものとすることができる。本開示において「配合する」とは、粒子A及び水、並びに必要に応じて粒子B、pH調整剤、酸化剤及びその他の成分を同時に又は任意の順に混合することを含む。前記配合は、例えば、ホモミキサー、ホモジナイザー、超音波分散機及び湿式ボールミル等の混合器を用いて行うことができる。研磨液組成物Iの調製の際の各成分の配合量は、上述した研磨液組成物I中の各成分の含有量と同じとすることができる。
本開示における被研磨基板は、磁気ディスク基板の製造に用いられる基板であり、例えば、Ni-Pメッキされたアルミニウム合金基板が挙げられる。本開示において「Ni-Pメッキされたアルミニウム合金基板」とは、アルミニウム合金基材の表面を研削後、無電解Ni-Pメッキ処理したものをいう。被研磨基板の表面を本開示における研磨工程で研磨した後、スパッタ等でその基板表面に磁性層を形成する工程を行うことにより、磁気ディスクを製造できうる。被研磨基板の形状は、例えば、ディスク状、プレート状、スラブ状、プリズム状等の平面部を有する形状や、レンズ等の曲面部を有する形状が挙げられ、好ましくはディスク状の被研磨基板である。ディスク状の被研磨基板の場合、その外径は例えば10~120mmであり、その厚みは例えば0.5~2mmである。
本開示に係る製造方法の研磨工程では、例えば、研磨パッドを貼り付けた定盤で被研磨基板を挟み込み、前記研磨液組成物Iを研磨面に供給し、圧力を加えながら研磨パッドや被研磨基板を動かすことにより、被研磨基板を研磨する。本開示における研磨工程は、切削深さが上述した範囲内となるように研磨条件を調整することを含むことができ、例えば、3kPa以上30kPa以下の研磨荷重において、切削深さが上述した範囲となる砥粒を選択することを含むことができる。
本開示は、砥粒及び水を含有する研磨液組成物を用いて被研磨基板を研磨することを含み、前記研磨において、切削深さが5nm以上25nm以下であり、前記切削深さは、砥粒が基板表面を切削するときに生じる凹部の深さであり、前記被研磨基板は、磁気ディスク基板の製造に用いられる基板である、基板の研磨方法(以下、「本開示に係る研磨方法」ともいう)に関する。本開示に係る研磨方法を使用することにより、高研磨速度を確保しつつ、スクラッチが低減された磁気ディスク基板を高い基板収率で、生産性よく製造できるという効果が奏されうる。具体的な研磨の方法及び条件は、上述した本開示に係る製造方法と同じようにすることができる。本開示に係る研磨方法は、最終の基板品質をより向上させる観点から、粗研磨工程に適用されることが好ましい。
表1に記載の砥粒(非球状シリカ粒子A、球状シリカ粒子B、アルミナ砥粒)、酸(リン酸)、酸化剤(過酸化水素)、及び水を用い、表3に記載の実施例1~6及び比較例1~14の研磨液組成物Iを調製した。各研磨液組成物I中の各成分の含有量は、砥粒:5質量%、リン酸:1.5質量%、過酸化水素:0.8質量%とした。各研磨液組成物IのpHは1.6であった。砥粒に用いた非球状シリカ粒子Aのタイプは、異形型シリカ粒子及び沈降法シリカ粒子であった。表1において、A1、2、8~10の異形型シリカ粒子は、水ガラス法で製造されたもの(コロイダルシリカ)であり、A7の異形型シリカ粒子は、ゾルゲル法で製造されたもの(コロイダルシリカ)であり、A3~6の沈降法シリカ粒子は、沈降法により製造されたものである。砥粒に用いた球状シリカ粒子Bは、水ガラス法により製造されたもの(コロイダルシリカ)である。pHは、pHメータ(東亜ディーケーケー社製)を用いて測定し、電極を研磨液組成物へ浸漬して30秒後の数値を採用した(以下、同様)。
BET比表面積Sは、下記の[前処理]をした後、測定サンプル約0.1gを測定セルに小数点以下4桁(0.1mgの桁)まで精量し、比表面積の測定直前に110℃の雰囲気下で30分間乾燥した後、比表面積測定装置(島津製作所製 マイクロメリティック自動比表面積測定装置「フローソーブIII2305」)を用いてBET法により測定した。
[前処理]
スラリー状の砥粒をシャーレにとり150℃の熱風乾燥機内で1時間乾燥させた。乾燥後の試料をメノウ乳鉢で細かく粉砕して測定サンプルを得た。
砥粒の平均一次粒子径は、上記BET比表面積S(m2/g)を用いて下記式から算出した。
平均一次粒子径(nm)=2727/S
シリカ粒子をイオン交換水で希釈し、シリカ粒子を1質量%含有する分散液を作製した。そして、該分散液を下記測定装置内に投入し、シリカ粒子の体積粒度分布を得た。得られた体積粒度分布の累積体積頻度が50%となる粒径(Z-average値)を二次粒子径とした。
測定機器 :マルバーン ゼータサイザー ナノ「Nano S」
測定条件 :サンプル量 1.5mL
:レーザー He-Ne、3.0mW、633nm
:散乱光検出角 173°
ポイズ530(花王社製、ポリカルボン酸型高分子界面活性剤)を0.5質量%含有する水溶液を分散媒として、下記測定装置内に投入し、続いて透過率が75~95%になるようにサンプル(アルミナ粒子)を投入し、その後、5分間超音波を付与した後、粒径を測定した。
測定機器 :堀場製作所製 レーザー回折/散乱式粒度分布測定装置 LA920
循環強度 :4
超音波強度:4
砥粒粒子をTEM(日本電子社製「JEM-2000FX」、80kV、1~5万倍)で観察した写真をパーソナルコンピュータにスキャナで画像データとして取込み、解析ソフト(三谷商事「WinROOF(Ver.3.6)」)を用いて500個の粒子の投影画像データを解析した。そして、個々の粒子の短径を求め、短径の平均値(平均短径)を得た。
被研磨基板の研磨を下記工程(1)及び(2)に従い行った。各工程の条件を以下に示す。
(1)研磨工程:研磨液組成物Iを用いて被研磨基板の研磨対象面を研磨する工程。
(2)洗浄工程:工程(1)で得られた基板を洗浄する工程。
被研磨基板は、Ni-Pメッキされたアルミニウム合金基板を用いた。この被研磨基板は、厚み1.27mm、直径95mmであった。
研磨機:両面研磨機(9B型両面研磨機、スピードファム社製)
被研磨基板枚数:10枚
研磨液:実施例1~9及び比較例1~17の研磨液組成物I
研磨パッド:スエードタイプ(発泡層:ポリウレタンエラストマー)、厚み:1.0mm、平均気孔径:30μm、表面層の圧縮率:2.5%(Filwel社製「CR200」)
定盤回転数:35rpm
研磨荷重:表3~4に記載の設定値
研磨液供給量:100mL/分(被研磨基板面1cm2あたり、0.076mL/分に相当)
研磨時間:6分
工程(1)で得られた基板を、下記条件で洗浄した。
まず、0.1質量%のKOH水溶液からなるpH12のアルカリ性洗浄剤組成物の入った槽内に、工程(1)で得られた基板を5分間浸漬する。次に、浸漬後の基板を、イオン交換水で20秒間すすぎを行う。そして、すすぎ後の基板を洗浄ブラシがセットされたスクラブ洗浄ユニットに移送し洗浄する。
切削深さは、下記の測定方法により測定した。
まず、上述の研磨試験に用いた被研磨基板と同様の基板を用いて、公知の方法にて粗研磨及び仕上げ研磨を行い、基板表面の凹部の深さが1.0nm以下となる基板を予め作製した。作製した基板表面の凹部の深さは、光干渉型表面形状測定機「OptiFLAT III」(KLA Tencor社製)を用い、後述する切削深さ測定条件で測定した。
次に、作製した基板に対し、砥粒濃度を表2に記載した量とし、研磨時間を30秒とした以外は、表3~4に示す実施例1~9及び比較例1~17の工程(1)と同じ条件で研磨を行った。具体的な研磨条件を以下に示す。前記砥粒濃度は、砥粒が基板表面上に一層に配置されるような濃度であって、以下の方法で算出した。
次に、研磨後の基板表面における砥粒粒子1個換算の凹部の深さの最大値の平均値を切削深さとして算出した。すなわち、研磨後の基板を前述の工程(2)と同様に洗浄後、光干渉型表面形状測定機「OptiFLAT III」(KLA Tencor社製)を用いて、任意の断面プロファイルを取ったときの凹部の深さの最大値を後述する切削深さ測定条件で測定した。そして、基板1面当たり5点ずつ測定し、基板4枚で合計20点の測定値の平均値を切削深さとして算出し、表3~4に示した。
研磨機:両面研磨機(9B型両面研磨機、スピードファム社製)
研磨パッド:Filwel社製「CR200」
基板枚数:4枚
研磨荷重:表3~4に記載の設定値(3.6~19.3kPa)
定盤回転数:35rpm
研磨液の流量:100mL/分(基板面1cm2あたり、0.190mL/分に相当)
研磨時間:30秒
切削深さは、砥粒(粒子)が基板表面上に一層に配置されるような条件で研磨したときの凹部の深さをいう。前記条件は、研磨液組成物中の砥粒の濃度と、研磨液組成物の量とを調整することで、設定できる。ここでは、研磨液組成物中の砥粒が、図5に示すように、複数の砥粒(粒子)が、互いに接しかつ基板厚み方向に重ならないように研磨パッド上に配置されると仮定し、前記研磨液組成物中の砥粒の濃度を、下記式に基づいて算出した。算出した値を表2に示した。
<砥粒濃度の計算式>
・研磨パッドの表面積(両面):5526cm2
・シリカの比重:2.2g/cm3
・アルミナの比重:4.0g/cm3
・砥粒の粒子径:平均二次粒子径(cm)
・研磨液組成物の流量:100mL/分
・研磨時間:30秒間
・研磨液組成物の質量:50g (※研磨液の比重を1とした)
・粒子1個換算の質量(g/個)
=1個換算の体積(cm3/個)×粒子の比重(g/cm3)
=(4/3)×π×(平均二次粒子径/2)3×粒子の比重 (g/cm3)
・粒子1個換算の断面積(cm2/個)=π×(平均二次粒子径/2)2
・砥粒濃度(質量%)
=5526(cm2)×粒子1個換算の質量(g/個)/粒子1個換算の断面積(cm2/個)/50×100
測定機器:光干渉型表面形状測定機「OptiFLAT III」(KLA Tencor社製)
Radius Inside/Out:14.87mm/47.83mm
Center X/Y:55.44mm/53.38mm
Low Cutoff:2.5mm
Inner Mask:18.50mm
Outer Mask:45.5mm
Long Period:2.5mm
Wa Correction:0.9
Rn Correction:1.0
No Zernike Terms:8
[工程(1)の研磨速度の測定方法及び評価]
研磨前後の各基板1枚当たりの重さを計り(Sartorius社製、「BP-210S」)を用いて測定し、各基板の質量変化から質量減少量を求めた。全10枚の平均の質量減少量を研磨時間で割った値を研磨速度として下記式により算出し、さらに実施例1を100.0とした研磨速度の相対値を算出した。その結果を表3~4に示す。
質量減少量(g)={研磨前の質量(g)-研磨後の質量(g)}
研磨速度(mg/min)=質量減少量(mg)/研磨時間(min)
<評価基準>
研磨速度:評価
20mg/min以上:「A:研磨速度が良好で、基板収率向上が期待できる」
10mg/min以上20mg/min未満:「B:実生産には改良が必要」
10mg/min未満:「C:基板収率が大幅に低下する」
測定機器:光学製顕微鏡 本体BX60M、デジタルカメラDP70(オリンパス社製)
評価:対物レンズ200倍、中間レンズ2.5倍を使用し、暗視野観察(視野550×420μm)により、スクラッチ数を測定した。上記観察は、工程(2)後の10枚の基板から任意に2枚を選択し、基板の両面について中心から30mmの位置を90°ごとの各4点、計16点観察した。観察した画像をパーソナルコンピュータ(PC)に取り込み、画像解析ソフトWinRoof(三谷商事)にてスクラッチ数を(実施例1を100とした相対値)を算出した。その結果を表3~4に示す。
<評価基準>
スクラッチ数(相対値):評価
0超150以下 :「A:極めて発生が抑制され、更なる基板収率向上が期待できる」
150超175以下:「B:発生が抑制され、基板収率向上が期待できる」
175超200以下:「C:実生産可能」
200超 :「D:基板収率が大幅に低下する」
工程(2)後の各基板の表面を走査型電子顕微鏡(日立製作所製:S-4800)にて1万倍で観察し、アルミナ残留物の有無を確認した。
各評価の結果を表3~4に示した。
Claims (13)
- 砥粒及び水を含有する研磨液組成物を用いて被研磨基板を研磨する研磨工程を含み、
前記砥粒は、切削深さが5nm以上25nm以下となる粒子であり、
前記切削深さは、砥粒が基板表面を切削するときに生じる凹部の深さである、磁気ディスク基板の製造方法。 - 前記切削深さは、前記砥粒が基板表面上に一層に配置されるような条件で研磨したときの凹部の深さである、請求項1に記載の磁気ディスク基板の製造方法。
- 前記砥粒は、非球状シリカ粒子Aを含む、請求項1又は2に記載の磁気ディスク基板の製造方法。
- 前記非球状シリカ粒子Aの平均短径が、100nm以上である、請求項3に記載の磁気ディスク基板の製造方法。
- 前記非球状シリカ粒子Aの平均二次粒子径が、170nm以上である、請求項3又は4に記載の磁気ディスク基板の製造方法。
- 前記砥粒中の焼成シリカの含有量が、50質量%未満である、請求項1から5のいずれかに記載の磁気ディスク基板の製造方法。
- 前記研磨液組成物中のアルミナ砥粒の含有量が、0.1質量%以下である、請求項1から6のいずれかに記載の磁気ディスク基板の製造方法。
- 前記研磨工程が、粗研磨工程である、請求項1から7のいずれかに記載の磁気ディスク基板の製造方法。
- 前記被研磨基板が、Ni-Pメッキされたアルミニウム合金基板である、請求項1から8のいずれかに記載された磁気ディスク基板の製造方法。
- 砥粒及び水を含有する研磨液組成物を用いて被研磨基板を研磨する研磨工程を含み、
前記研磨工程において、切削深さが5nm以上25nm以下であり、
前記切削深さは、砥粒が基板表面を切削するときに生じる凹部の深さである、磁気ディスク基板の製造方法。 - 前記砥粒は、切削深さが5nm以上25nm以下となるシリカ粒子である、請求項10に記載の磁気ディスク基板の製造方法。
- 前記研磨工程は、切削深さが5nm以上25nm以下となるように研磨条件を調整することを含む、請求項1から10のいずれかに記載の磁気ディスク基板の製造方法。
- 砥粒及び水を含有する研磨液組成物を用いて被研磨基板を研磨することを含み、
前記研磨において、切削深さが5nm以上25nm以下であり、
前記切削深さは、砥粒が基板表面を切削するときに生じる凹部の深さであり、
前記被研磨基板は、磁気ディスク基板の製造に用いられる基板である、基板の研磨方法。
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