JP5013986B2 - Manufacturing method of glass substrate - Google Patents

Description

  The present invention relates to a method for manufacturing a glass substrate.

  Recent memory hard disk drives are required to reduce the flying height of the magnetic head to reduce the unit recording area in order to increase the recording density for the purpose of increasing the capacity and reducing the diameter. Along with this, the surface quality required after polishing in the manufacturing process of the magnetic disk substrate is becoming stricter year by year. That is, it is necessary to reduce the surface roughness, micro waviness, roll-off and protrusions according to the lower flying height of the head, and the number of scratches, size, and depth per one side of the substrate further according to the decrease of the unit recording area. There is a need to reduce. In order to realize the surface quality required for such a magnetic disk substrate, a glass substrate is used as the hard disk substrate instead of the conventionally widely used aluminum substrate. The glass substrate exhibits favorable performance in terms of surface flatness and substrate strength compared to an aluminum substrate. As such a glass substrate, a chemically strengthened glass substrate or a crystallized glass substrate whose substrate strength is increased by crystallization may be used in order to increase the substrate strength. Further, the glass substrate is being used as a mask substrate in EUV lithography technology used at the time of manufacturing an integrated circuit (see, for example, Patent Document 1). A glass substrate for a mask used for EUV lithography is also required to have high surface flatness.

As a method of reducing the surface roughness of the substrate after polishing when polishing the substrate, the surface roughness after polishing by polishing with an acidic polishing composition containing colloidal silica having an average primary particle size of 50 nm or less is used. A polishing method for reducing the thickness to a predetermined value or less is disclosed (Patent Document 1). A polishing method including softening a part of a substrate using a chemical corrosive agent and removing the part using colloidal particles is also disclosed (Patent Document 2).
JP 2006-35413 A JP-A-7-240025

  As described above, in the polishing process in the production of the glass substrate, it is important to improve the substrate quality by reducing the surface roughness of the substrate after polishing. However, it is also important to achieve and maintain an economical polishing rate with excellent productivity.

  The present invention provides a method for producing a glass substrate, which can produce a glass substrate excellent in substrate quality with high productivity. The present invention also provides a method for evaluating a polishing composition for a glass substrate suitable for polishing a glass substrate to be polished.

  The method for producing a glass substrate of the present invention comprises a step of polishing a polishing composition containing an abrasive and water between a polishing pad and a glass substrate to be polished, and the pH of the polishing composition. Is 4 or less, and the polishing composition and the glass substrate to be polished are measured by pressing a probe of an atomic force microscope against the surface of the glass substrate to be polished immersed in the polishing composition. This is a method for manufacturing a glass substrate that satisfies the relationship that the depth of penetration is 4 nm or less.

  The glass substrate polishing liquid composition evaluation method of the present invention measures the depth of penetration of the probe into the substrate surface by pressing the probe against the surface of the glass substrate to be polished immersed in the glass substrate polishing liquid composition. And evaluating the suitability of the glass substrate polishing liquid composition for use in the glass substrate to be polished using the measured value of the penetration depth as an index. .

  According to the method for producing a glass substrate of the present invention, for example, glass whose surface roughness after polishing is reduced in the polishing step and polishing having an economical polishing rate is possible, thereby improving the substrate quality. There is an effect that the substrate can be manufactured with high productivity.

  According to the method for evaluating a polishing composition for a glass substrate of the present invention, for example, a polishing composition that can achieve an economical polishing rate in polishing a glass substrate to be polished and can reduce the surface roughness after polishing. And the polishing composition can be used.

  In general, a glass substrate is chemically durable and is said to hardly corrode even under acidic conditions with a pH of 4 or less. On the other hand, it is known that the surface roughness after polishing deteriorates in polishing of a glass substrate using an acidic polishing liquid composition. When the present inventors polish a glass substrate using an acidic polishing composition, the hardness of the glass substrate surface layer in contact with the acidic polishing composition changes, and as a result, the surface roughness after polishing deteriorates. I got the knowledge to do. When a glass substrate containing sodium (Na) comes into contact with an acidic solution, Na elutes as ions from the glass substrate, causing an ion exchange reaction in which hydronium ions in the solution enter the glass substrate, resulting in an ion exchange reaction. It is presumed that the surface layer of the glass substrate becomes sparse and brittle, and the surface roughness of the polished glass substrate deteriorates.

  The present invention is based on the knowledge that the surface roughness of the substrate after polishing can be reduced by controlling the thickness of the altered layer in which the hardness of the surface layer of the glass substrate to be polished that has been in contact with the acidic polishing composition is reduced. .

  The method for producing a glass substrate of the present invention is a method for producing a glass substrate, comprising a step of polishing a polishing composition containing an abrasive and water between a polishing pad and a glass substrate to be polished. The polishing liquid composition has a pH of 4 or less, and the polishing liquid composition and the glass substrate to be polished are provided with an atomic force microscope probe on the surface of the glass substrate to be polished immersed in the polishing liquid composition. This satisfies the relationship that the probe penetration depth measured by pressing is 4 nm or less. As a result, for example, the surface roughness after polishing is reduced and polishing with an economical polishing rate is possible, and as a result, an effect that a glass substrate with improved substrate quality can be produced with high productivity is exhibited. The

[Probe penetration depth]
In the method for manufacturing a glass substrate of the present invention (hereinafter also referred to as the manufacturing method of the present invention), the penetration depth of the probe is the probe of an atomic force microscope (AFM) on the surface of the glass substrate immersed in the polishing composition. It refers to the probe penetration depth measured by pressing the needle, and more specifically, the probe penetration depth measured by the following standard test. From the viewpoint of reducing the surface roughness of the substrate after polishing, the penetration depth of the probe is preferably 3 nm or less, more preferably 2 nm or less, and from the viewpoint of improving the polishing rate, preferably 0.5 nm or more, more Preferably it is 1 nm or more.

[Standard test]
First, the glass substrate to be measured is cut into a measurable size and set in an AFM apparatus in a state of being immersed in the polishing composition. Although the size depends on the AFM apparatus to be used, for example, 10 mm × 10 mm can be mentioned. Subsequently, in order to simulate actual polishing in which polished new surfaces appear one after another, a new surface is formed by scanning a range of 0.5 μm × 0.5 μm at 1 Hz with a load of 0.73 μN as preprocessing. Then, the penetration depth is obtained by pressing the probe of the AFM device against the new surface under the following conditions.
Measurement (pressing) conditions <br/> Glass substrate moving distance: 100 nm
Approach speed: 1Hz (200nm / s)
Measurement location: Number of measurements near the center of the new surface 0.5 μm × 0.5 μm: N = 3 times at different locations Cantilever: NP-S (Si3N4 chip) manufactured by Veeco
Folding (pushing end) set value: Cantilever warping amount = 40 nm
The uppermost surface of the penetration depth is a position where the probe comes into contact with the surface of the glass substrate to be measured and the cantilever starts to warp. Further, the probe is pushed in, and when the cantilever warpage reaches 40 nm, the pushing is finished, and the position is set as the lowermost surface. The difference in position between the uppermost surface and the lowermost surface is defined as the penetration depth, and the average of three times is defined as the penetration depth of the probe.

Examples of the AFM apparatus used for this standard test include the following apparatuses.
Outline of measuring device (example)
Manufacturer: Veeco (formerly Digital Instruments)
Controller: NanoScope IIIa
Body: Multi-mode AFM
Scanner: JV Scanner The above apparatus is an example, and the AFM apparatus used for the standard test is not limited to this.

[Polishing liquid composition]
The polishing composition in the present invention contains an abrasive and water and has a pH of 4 or less. The pH of the polishing composition is preferably pH 1 to 4, more preferably pH 1 to 3, and still more preferably pH 1 to 2, from the viewpoint of improving the polishing rate. It is preferable that the polishing composition further contains a water-soluble polymer from the viewpoint of reducing the surface roughness of the substrate after polishing. By adding a water-soluble polymer to the polishing composition, the depth of penetration of the probe can be preferably controlled.

[Abrasive]
As the abrasive in the present invention, an abrasive generally used for polishing can be used, and examples thereof include metal, metal or metalloid carbide, nitride, oxide, boride, diamond, and the like. It is done. The metal or metalloid element is derived from Group 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A or Group 8 of the periodic table (long period type). Specific examples of the abrasive include silicon oxide (hereinafter referred to as silica), aluminum oxide (hereinafter referred to as alumina), silicon carbide, diamond, manganese oxide, magnesium oxide, zinc oxide, titanium oxide, cerium oxide, zirconium oxide, and the like. In addition, the surface of these abrasives may be modified or surface-modified with a functional group, or may be compounded with a surfactant or an abrasive, and the use of one or more of these may reduce surface roughness. To preferred. Furthermore, colloidal particles and fumed silica particles are preferable from the viewpoint of reducing the surface roughness of the substrate after polishing and reducing scratches, more preferably colloidal particles, and of these, colloidal silica is particularly preferable. In addition, you may use the above-mentioned thing individually or in mixture of 2 or more types as an abrasive. The abrasive is preferably dispersed in the polishing composition at the time of use.

  Colloidal silica is a water-glass method in which alkali metal silicates such as sodium silicate are used as raw materials, and are subjected to a condensation reaction in an aqueous solution to grow particles, or alkoxysilanes such as tetraethoxysilane as raw materials, and water-soluble organic solvents such as alcohols. It is obtained by an alkoxysilane method in which a condensation reaction is carried out in water containing. Further, fumed silica is obtained by a vapor phase method in which a volatile silicon compound such as silicon tetrachloride is used as a raw material and is hydrolyzed and grown at a high temperature of 1000 ° C. or higher with an oxygen-hydrogen burner.

The average particle size of the primary particles of silica is preferably 1 to 50 nm from the viewpoint of reducing the surface roughness of the substrate after polishing. From the viewpoint of further improving the polishing rate, it is more preferably 3 to 50 nm, further preferably 5 to 40 nm, and still more preferably 5 to 30 nm. In the determination of the average particle size of the primary particles in the present invention, a method by image analysis of an observation image with a transmission electron microscope (TEM) was used. That is, a photograph obtained by observing silica particles with a transmission electron microscope (JEM-2000FX, manufacturer: JEOL) under the conditions of an acceleration voltage of 80 kV and a photographing magnification of 10,000 to 50,000 times is displayed with a scanner connected to a personal computer. Imported as data, and using image analysis software (WinROOF, distributor: Mitani Shoji), the equivalent circle diameter of each silica particle (the diameter of a circle having the same area as the projected area of the silica particles) is regarded as the particle size. After accumulating 1000 or more pieces of silica particle data, it is calculated using spreadsheet software “EXCEL” (manufactured by Microsoft). The particle size (D ₅₀ ) at which the cumulative volume from the small particle size side becomes 50% is the average particle size of the primary particles as referred to in the present invention.

  When silica forms secondary particles, the average particle size of the secondary particles is preferably 10 to 100 nm, more preferably 15 to 90 nm, from the viewpoint of reducing scratches and reducing the surface roughness. More preferably, it is 80 nm. Examples of the method for measuring the secondary particle diameter include a dynamic light scattering method, an ultrasonic attenuation method, and a capillary (CHDF) method.

  The content of silica in the polishing composition is preferably 0.1 to 50% by weight, more preferably 1 to 45% by weight from the viewpoint of reducing the surface roughness of the substrate after silica polishing and improving the polishing rate. Preferably, 5 to 40% by weight is more preferable.

[water]
As the water used in the present invention, ion exchange water, distilled water, ultrapure water or the like is preferably used. The water content in the polishing composition is preferably 40 to 99% by weight, more preferably 50 to 98% by weight from the viewpoint of maintaining the fluidity of the polishing composition and improving the polishing rate. 50 to 97% by weight is more preferred, and 50 to 95% by weight is even more preferred.

[Water-soluble polymer]
The water-soluble polymer that can be included in the polishing composition used in the production method of the present invention comprises a structural unit derived from a monomer having a carboxylic acid group and a structural unit derived from a monomer having a sulfonic acid group. A (co) polymer (hereinafter also referred to as an anionic water-soluble polymer) having at least one structural unit selected from the group is preferred. Examples of the monomer having a carboxylic acid group include itaconic acid, (meth) acrylic acid, maleic acid and the like. Examples of the monomer having a sulfonic acid group include isoprene sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, styrene sulfonic acid, methallyl sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, isoamido Examples include lensulfonic acid. Of these, isoprenesulfonic acid and 2- (meth) acrylamide-2-methylpropanesulfonic acid are preferable from the viewpoint of reducing the surface roughness. The anionic water-soluble polymer may contain two or more types of structural units derived from a monomer having a carboxylic acid group and structural units derived from a monomer having a sulfonic acid group. In addition, the anionic water-soluble polymer can contain structural unit components other than these.

  As a preferable anionic water-soluble polymer, from the viewpoint of reducing the surface roughness of the substrate after polishing, a copolymer obtained by polymerizing (meth) acrylic acid and isoprenesulfonic acid, (meth) acrylic acid and A copolymer obtained by polymerizing 2- (meth) acrylamido-2-methylpropanesulfonic acid, polymerizing (meth) acrylic acid, isoprenesulfonic acid and 2- (meth) acrylamido-2-methylpropanesulfonic acid. And a copolymer obtained in the above manner.

  The content of the structural unit derived from the sulfonic acid group-containing monomer in all the structural units of the anionic water-soluble polymer is reduced in the surface roughness of the substrate after polishing, the polishing rate is improved, and the copolymer itself. From the viewpoint of persistence, 10 to 100 mol% is preferable, more preferably 20 to 100 mol%, and still more preferably 40 to 100 mol%. Here, the acrylic acid monomer containing a sulfonic acid group is counted as a sulfonic acid group-containing monomer.

The weight average molecular weight of the anionic water-soluble polymer is preferably from 500 to 20,000, more preferably from 500 to 10,000, from the viewpoints of reduction of the surface roughness of the substrate after polishing, improvement of the polishing rate, and persistence of the copolymer itself. Preferably, 500 to 5000 is more preferable, 500 to 3000 is even more preferable, and 500 to 1500 is even more preferable. The measurement of this weight average molecular weight can be performed by converting the result measured by gel permeation chromatography (GPC) using a calibration curve prepared using sodium polystyrene sulfonate as a standard sample. The GPC conditions are shown below.
GPC condition column; G4000PWXL (manufactured by Tosoh Corporation) + G2500PWXL (manufactured by Tosoh Corporation)
Eluent: 0.2M phosphate buffer / acetonitrile = 9/1 (volume ratio)
Flow rate: 1.0 mL / min
Temperature: 40 ° C
Detection: 210nm
Sample: concentration 5 mg / mL (injection volume 100 μL)

  An anionic water-soluble polymer is obtained by, for example, converting a base polymer containing a diene structure or an aromatic structure into a known method, for example, edited by The Chemical Society of Japan, New Experimental Chemistry Course 14 (Synthesis and Reaction of Organic Compounds III, 1773, 1978) and the like. The anionic water-soluble polymer may be in the form of a salt. Although the counter ion for forming a salt is not specifically limited, 1 or more types can be used from alkali metal ions, such as sodium and potassium, ammonium ion, alkylammonium ion, etc.

  The content of the water-soluble polymer or anionic water-soluble polymer in the polishing composition is preferably 0.0001 to 10% by weight from the viewpoint of reducing the surface roughness of the substrate after polishing and improving the polishing rate. More preferably, it is 0.001 to 5 weight%, More preferably, it is 0.005 to 1 weight%.

  As described above, the depth of penetration of the probe can be preferably controlled by adding a water-soluble polymer or an anionic water-soluble polymer to the polishing composition. For example, when a polishing composition composed of water and an abrasive and a glass substrate to be polished exceed a probe penetration depth of 4 nm, a water-soluble polymer or an anionic water-soluble polymer is added to the polishing composition. By doing so, the penetration depth of the probe can be set to 4 nm or less. The mechanism by which the penetration depth of the probe is reduced by the water-soluble polymer or the anionic water-soluble polymer is not clear, but is considered as follows. That is, new polishing surfaces are successively generated on the surface of the glass substrate being polished. Since this polished new surface is in a very active state compared to the normal glass substrate surface, anionic groups such as carboxyl groups in the water-soluble polymer are easily adsorbed, and the adsorbed water-soluble polymer is in the glass substrate. By preventing the elution of Na ions, embrittlement of the surface layer of the glass substrate is suppressed, and as a result, the penetration depth of the probe is reduced. In the case of a water-soluble polymer containing a carboxyl group and a sulfonic acid group, the water-soluble property under acidic conditions is further increased, so that the adsorption rate to the newly polished surface is increased and the probe penetration depth is further increased. Presumed to be controlled.

[Method for producing polishing composition]
The polishing composition can be prepared by mixing the above-described components (water, abrasive, and other components such as a water-soluble polymer as required) by a known method. From the viewpoint of economy, the polishing liquid composition is usually produced as a concentrated liquid and is often diluted at the time of use. In addition, it is preferable to perform the above-mentioned standard test with the polishing liquid composition at the time of use. The pH of the polishing composition can be adjusted by, for example, the acid content. Such acids include inorganic acids and organic acids. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, amidosulfuric acid and the like. Examples of organic acids include carboxylic acids, organic phosphoric acids, amino acids, and the like. For example, carboxylic acids include monovalent carboxylic acids such as acetic acid, glycolic acid, and ascorbic acid, divalent carboxylic acids such as oxalic acid and tartaric acid, Examples of the organic phosphoric acid include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotri (methylenephosphonic acid), ethylenediaminetetra ( Methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and the like. Examples of amino acids include glycine and alanine. Among these, inorganic acid, carboxylic acid and organic phosphoric acid are preferable from the viewpoint of surface roughness reduction. For example, hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, glycolic acid, acid, citric acid, HEDP, aminotri ( Methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) are suitable. These acids for adjusting the pH may be used singly or in combination of two or more.

[Optional ingredients]
The polishing liquid composition may further contain an oxidizing agent, a bactericidal agent, an antibacterial agent, a thickener, a dispersant, a rust preventive agent, a basic substance, a surfactant, a pH adjuster, and the like. The content of these components in the polishing composition is preferably 10% by weight or less, more preferably 8% by weight or less, and still more preferably 6% by weight or less from the viewpoint of polishing characteristics.

[Polished glass substrate / manufactured glass substrate]
Examples of the glass substrate produced by the production method of the present invention include a magnetic hard disk substrate for a magnetic disk and a magneto-optical disk, and include a liquid crystal display, a plasma display (hereinafter referred to as PD), an inorganic and organic electroluminescence display, and a field emission. Examples include glass substrates for flat panel displays such as displays, photomask substrates, and other glass substrates for precision parts such as optical disks, optical lenses, optical mirrors, optical prisms, and semiconductor substrates. Therefore, examples of the glass substrate to be polished in the production method of the present invention include glass substrates to be polished of these produced glass substrates. Examples of the material of the glass substrate to be polished include quartz glass, soda lime glass, aluminosilicate glass, borosilicate glass, aluminoborosilicate glass, alkali-free glass, crystallized glass, and glassy carbon. Among these, this invention has a remarkable effect with respect to the glass substrate containing sodium (Na). The material of the glass substrate to be polished may be an aluminosilicate glass for a tempered glass substrate or a glass ceramic substrate (crystallized glass substrate). There is no restriction | limiting in particular in the shape of a glass substrate to be polished, For example, the shape which has flat parts, such as a disk shape, plate shape, slab shape, prism shape, and the shape which has curved surface parts, such as a lens, may be sufficient.

[Glass substrate manufacturing method]
The production method of the present invention is a step of polishing a polishing composition having a pH of 4 or less between a polishing pad and a glass substrate to be polished, wherein the polishing liquid composition and the glass substrate to be polished are searched. There is a polishing step (hereinafter also referred to as “polishing step”) that satisfies the relationship that the needle penetration depth is 4 nm or less. As a polishing method in this “polishing step”, a polishing method using a polishing apparatus may be mentioned. Specifically, the glass substrate to be polished is held by a carrier, sandwiched by a polishing platen to which a polishing pad is attached, a polishing composition is supplied between the polishing pad and the glass substrate to be polished, and a predetermined pressure is applied. There is a polishing method in which the polishing liquid composition is moved while the polishing liquid composition is in contact with the glass substrate to be polished by moving the polishing platen and / or the glass substrate to be polished. In this “polishing step”, by polishing the glass substrate to be polished using a polishing composition that satisfies the relationship that the probe depth is 4 nm or less, for example, the surface roughness after polishing in the polishing step And a glass substrate with improved substrate quality can be manufactured with high productivity.

The glass substrate polishing apparatus used in the production method of the present invention is not particularly limited, and for example, a polishing apparatus including means for holding a glass substrate to be polished (carrier: made of aramid, etc.) and a polishing cloth (polishing pad) is used. be able to. Especially, the double-side polish apparatus used for a polishing process can be used preferably. In the production method of the present invention, the polishing load refers to the pressure applied to the polishing surface of the glass substrate to be polished at the time of polishing. From the viewpoint of improving the polishing rate, it is preferably 3 kPa or more, more preferably 4 kPa or more, and further 5 kPa or more. More preferably, 5.5 kPa or more is even more preferable. Further, from the viewpoint of reducing the surface roughness of the substrate after polishing, it is preferably 20 kPa or less, more preferably 15 kPa or less, even more preferably 10 kPa or less, and even more preferably 9 kPa or less. Therefore, from the viewpoint of reducing the surface roughness of the glass substrate after polishing and improving the polishing rate, it is preferably 3 to 20 kPa, more preferably 4 to 15 kPa, even more preferably 5 to 10 kPa, and even more preferably 5.5. ~ 9kPa. Since the preferable supply rate of the polishing liquid composition in the “polishing step” varies depending on the area of the polishing pad in contact with the glass substrate to be polished and the total area of the loaded substrate, and further on the type of polishing liquid composition, Although not determined, 0.06 to 5 mL / min per unit polished area (1 cm ² ) of the glass substrate to be polished is preferable from the viewpoint of reducing the surface roughness of the glass substrate after polishing and improving the polishing rate. 0.08-4 mL / min is more preferable, and 0.1-3 mL / min is more preferable.

[Glass hard disk substrate manufacturing method]
An embodiment of the production method of the present invention in which the glass substrate to be produced is a glass hard disk substrate will be described. In this case, the glass hard disk substrate is, for example, from a process of obtaining a glass substrate by a mold press of molten glass or a method of cutting out from sheet glass, a rough grinding process, a shape processing process, an end mirror processing process, a fine grinding process, a polishing process, and a cleaning process. It is manufactured through a process. Further, a magnetic disk is obtained by obtaining a magnetic disk manufacturing process. In general, in the case of a tempered glass substrate in the middle of this manufacturing process, next to the cleaning step, chemical strengthening is performed by immersing the substrate in a heated chemical strengthening salt of potassium nitrate and sodium nitrate to replace ions on the surface layer. A process is performed. In the case of a crystallized glass substrate, prior to this manufacturing process, a crystallization process is performed in advance to generate crystal nuclei by heat treatment to form a crystal phase. Also, for example, about # 400 alumina abrasive grains are used in the rough grinding process, cylindrical grinding stones are used in the shape processing process, brushes are used in the end mirror processing process, and about # 1000 alumina abrasive grains are used in the fine grinding process. The polishing step is generally divided into a first polishing step and a second polishing step, but a final (finishing) polishing step is often performed for the purpose of improving the surface quality. Cerium oxide is preferably used in the first polishing step, and silica is preferably used in the final (finish) polishing step. Accordingly, the “polishing step” in the production method of the present invention is preferably used, for example, in the polishing step in the method for producing a glass hard disk substrate, and is preferably used as the second polishing step or later, which significantly reduces the surface roughness. From the viewpoint of obtaining excellent surface smoothness, it is more preferably used in the finish polishing step. Note that the finish polishing step refers to at least one final polishing step when there are a plurality of polishing steps. The glass hard disk substrate is required to have smoothness that does not cause a read / write error of the magnetic head. That is, the substrate surface is required to have excellent flatness (roughness, waviness, etc.) and defects (protrusions such as abrasive grains, recesses such as scratches and pits). The second polishing step or the final (finish) polishing step is particularly important. After the polishing step, scrub cleaning to remove silica abrasive grains and polishing debris remaining on the glass substrate surface, and / or strong alkali ultrasonic cleaning using an aqueous sodium hydroxide solution to dissolve and remove the residue Then, immersion cleaning with pure water, isopropanol or the like, and steam drying with isopropanol or the like are performed. Thereafter, a seed layer, an underlayer, an intermediate layer, a magnetic layer, a protective layer, and a lubricating layer are formed to form a magnetic disk. Accordingly, the present invention is a method of manufacturing a magnetic disk including a “polishing step” as another aspect.

[Polishing pad]
As the polishing pad, organic polymer foam, non-foamed, non-woven polishing pad can be used. For example, in the first polishing step, a suede-like urethane hard pad, the second polishing step and the final polishing are used. In the process, a suede-like urethane soft pad is preferably used.

[Evaluation method of polishing liquid composition]
In another aspect, the present invention is a method for evaluating a polishing composition for a glass substrate (hereinafter also referred to as an evaluation method of the present invention), which is a surface of a glass substrate to be polished immersed in the polishing composition for a glass substrate. The probe is pressed against the substrate surface to measure the depth of penetration of the probe into the substrate surface, and the glass substrate polishing liquid composition is used for the glass substrate to be polished with the measured value of the penetration depth as an index. Includes assessing suitability. Evaluation of the suitability of the polishing composition for use on a glass substrate to be polished means that when the polishing composition is used for polishing a glass substrate to be polished, the polishing rate is reduced and the surface roughness after polishing is reduced. An assessment of whether or not can be achieved. According to the evaluation method of the present invention, for example, it is possible to select a polishing liquid composition that can achieve an economical polishing rate in polishing a glass substrate to be polished and can reduce the surface roughness after polishing. There exists an effect that a liquid composition can be used.

  The method for measuring the penetration depth of the probe in the evaluation method of the present invention includes a method using an atomic force microscope, for example, measurement by the standard test method described above. When the method for measuring the penetration depth of the probe is based on the above standard test, the penetration depth of the probe is 4 nm or less, preferably 3 or less, from the viewpoint of reducing the surface roughness of the substrate after polishing. More preferably, it is 2 nm or less, and from the viewpoint of improving the polishing rate, it is preferably 0.5 nm or more, more preferably 1 nm or more. The thing similar to the thing in the manufacturing method of this invention can be used for the polishing liquid composition and the glass substrate to be polished in the evaluation method of this invention. As another aspect, the present invention may be a glass substrate manufacturing method including selecting a polishing liquid composition for a glass substrate to be polished using the evaluation method of the present invention.

1. Glass substrate to be polished A hard disk having an outer diameter of 65 mmφ having an outer diameter of 65 mmφ and an inner diameter of 20 mmφ in which the first and second polishing steps are performed in advance with a polishing liquid composition containing ceria as an abrasive, and the surface roughness is 0.3 nm. An aluminosilicate glass substrate for use was used as the glass substrate to be polished. In addition, the measuring method of surface roughness is as mentioned later.

2. Preparation of composition to be polished As a polishing agent, colloidal silica slurry shown in Table 1 below is 5.0% by weight in terms of silica particles, and acrylic acid / acrylamido-2-methylpropanesulfonic acid in Table 1 below as an anionic water-soluble polymer (AA / AMPS) (co) polymer is 0.10% by weight in terms of effective component, and HEDP (manufactured by Solusia Japan, solid content concentration 60% by weight) as an acid is 0.13% by weight in terms of effective component, sulfuric acid (Wako Pure Chemical Industries, Ltd., concentrated sulfuric acid, reagent special grade) 0.40% by weight in terms of effective component, and ion-exchanged water as the balance were mixed, and polishing liquids of Examples 1 to 7 and Comparative Examples 1 and 2 below. A composition was prepared. Specifically, a predetermined amount of the anionic aqueous solution polymer diluted 5-fold with ion-exchanged water was added and mixed under stirring of an aqueous solution of HEDP and sulfuric acid, and the colloidal silica slurry was added last to be mixed and prepared. . The pH of the resulting polishing composition was as shown in Table 1 below.

  The AA / AMPS copolymer used in Examples 1 to 3 is a sulfonic acid group-containing monomer (APMS) content of 30 mol%, a weight average molecular weight of 1300, a solid content concentration of 40 wt%, and a sodium neutralized product. there were. The APMS content and weight average molecular weight of the AA / AMPS (co) polymers used in Examples 4 to 7 are as shown in Table 1 below.

  The colloidal silica slurry used in Examples 1 and 3 to 7 and Comparative Examples 1 and 2 was manufactured by DuPont, the average particle diameter of primary particles was 18 nm, the silica particle concentration was 40% by weight, and the balance was water. The colloidal silica slurry used was the same colloidal silica slurry except that the average particle size of the primary particles was 28 nm.

3. Standard Test The glass substrate to be measured, which had been cut to a size of 10 mm × 10 mm, was set in an atomic force microscope (AFM) apparatus while immersed in the polishing composition. Subsequently, in order to simulate actual polishing in which a new surface appears next, a new surface was created by scanning at 1 Hz over a range of 0.5 μm × 0.5 μm with a load of 0.73 μN as a pretreatment. On average, it was about 30 minutes so far after immersion. Then, a probe was pressed against the new surface under the following conditions to determine the penetration depth. The results are shown in Table 1 below.
AFM measuring device Manufacturer: Veeco (formerly Digital Instruments)
Controller: NanoScope IIIa
Body: Multi-mode AFM
Scanner: JV scanner
Measurement (pushing) conditions Glass substrate movement distance: 100 nm
Approach speed: 1Hz (200nm / s)
Measurement location: near the center of the new surface 0.5 um × 0.5 um Number of measurements: N = 3 times at different locations Cantilever: NP-S (Si3N4 chip) manufactured by Veeco
Folding (push end) set value: Cantilever warpage = 40 nm
The position where the probe comes into contact with the surface of the glass substrate to be measured and the cantilever starts to warp is taken as the uppermost surface of the depth of penetration. Further, the probe is pushed in and when the warpage of the cantilever reaches 40 nm, the pushing is finished. The position was the bottom surface. The difference in position between the uppermost surface and the lowermost surface was defined as the depth of penetration, and the average of three times in total was defined as the depth of penetration of the probe.

4). Polishing Test The glass substrate to be polished was polished under the polishing composition of Examples 1 to 7 and Comparative Examples 1 and 2 and the following polishing conditions. The polishing rate and the surface roughness after polishing are shown in Table 1 below.
Polishing conditions Polishing tester: Speedfam Co., 9B-5P-IV type double-sided polishing machine Polishing pad: Urethane finish polishing pad surface plate rotation speed: 10r / min
Lower surface plate rotation speed: 30r / min
Carrier rotation speed: 10r / min
Carrier: Aramid, thickness 0.45mm
Polishing liquid composition supply rate: 100 mL / min (about 0.3 mL / min / cm ² )
Final polishing time: 5 min
Final polishing load: 5.9 kPa
Rinse conditions: Load = 2.0 kPa, time = 5 min, ion exchange water supply amount = about 2 L / min
Dressing condition: Brush dressing was performed for 2 min while supplying ion-exchanged water for each polishing.

5. Evaluation method (1) Surface roughness The surface roughness was calculated | required as follows using atomic force microscope (AFM).
AFM measurement method Measuring instrument: manufactured by Veeco, TM-M5E
Mode: non-contact
Scanrate: 1.0 Hz
Scanarea: 10 × 10 μm
Evaluation method: Two points were measured (two-dimensional correction) in the vicinity of the middle between the inner periphery and the outer periphery on an arbitrary substrate center line, and the average value of the values was obtained to obtain the surface roughness.

(2) Polishing rate Unit of weight difference (g) of substrate before and after polishing divided by substrate density (2.46 g / cm ³ ), substrate surface area (30.04 cm ² ), and polishing time (min) The polishing amount per hour was calculated, and the polishing rate (μm / min) was calculated.

  As shown in Table 1 above, in the polishing using the polishing liquid compositions of Examples 1 to 7, the surface roughness after polishing is reduced as compared with those of Comparative Examples 1 and 2, and the polishing rate is economical. It can be seen that polishing with

  By using the present invention, for example, a glass substrate with improved substrate quality such as a glass hard disk substrate suitable for increasing the recording density can be efficiently produced.

Claims (7)

A method for producing a glass substrate comprising a step of polishing a polishing composition containing an abrasive and water between a polishing pad and a glass substrate to be polished.
The polishing composition has a pH of 4 or less,
The polishing composition and the glass substrate to be polished are measured by pressing the probe of an atomic force microscope (AFM) against the surface of the glass substrate to be polished immersed in the polishing composition. Saga 4nm meet the following as the relationship,
The penetration depth of the probe is a method for manufacturing a glass substrate, which is measured by the following steps (1) to (4) .
(1) A glass substrate to be measured is cut into a measurable size and set in an AFM apparatus in a state immersed in a polishing composition.
(2) In order to simulate actual polishing in which polished new surfaces appear one after another, a new surface is created by scanning a range of 0.5 μm × 0.5 μm at 1 Hz with a load of 0.73 μN as preprocessing.
(3) The probe of the AFM apparatus is pressed against the new surface under the following measurement (pressing) conditions.
[Measurement (pushing) conditions]
Glass substrate moving distance: 100 nm
Approach speed: 1Hz (200nm / s)
Measurement location: Near the center of the new surface 0.5μm × 0.5μm
Number of measurements: N = 3 times at different locations
Cantilever: NP-S (Si3N4 chip) manufactured by Veeco
Folding (pushing end) set value: Cantilever warping amount = 40 nm
(4) The uppermost surface of the penetration depth is set to a position where the probe comes into contact with the surface of the glass substrate to be measured and the cantilever starts to warp. Further, the probe is pushed in and pushed when the cantilever warpage reaches 40 nm. And that position is the bottom surface. The difference in position between the uppermost surface and the lowermost surface is defined as the penetration depth, and the average of three times is defined as the penetration depth of the probe. The method for producing a glass substrate according to claim 1, wherein the polishing liquid composition further contains a water-soluble polymer. The water-soluble polymer has at least one structural unit selected from the group consisting of a structural unit derived from a monomer having a carboxylic acid group and a structural unit derived from a monomer having a sulfonic acid group (co) The manufacturing method of the glass substrate of Claim 2 which is a polymer or its salt. The manufacturing method of the glass substrate as described in any one of Claim 1 to 3 with which the said polishing liquid composition contains colloidal silica as an abrasive | polishing material. The manufacturing method of the glass substrate as described in any one of Claim 1 to 4 whose grinding | polishing load in the said grinding | polishing is 3-20 kPa. The manufacturing method of the glass substrate as described in any one of Claim 1 to 5 whose glass substrate manufactured is a glass hard disk substrate. A method for evaluating a polishing liquid composition for a glass substrate,
Measuring the depth of penetration of the probe into the substrate surface by pressing the probe of an atomic force microscope (AFM) against the surface of the glass substrate to be polished immersed in the polishing liquid composition for glass substrate; and
Look including evaluating the use suitability of the to be polished glass substrate of the penetration depth of the glass substrate polishing composition measurements as an indicator,
The penetration depth of the probe is a method for evaluating a polishing composition for a glass substrate, which is measured by the following steps (1) to (4) .
(1) A glass substrate to be measured is cut into a measurable size and set in an AFM apparatus in a state immersed in a polishing composition.
(2) In order to simulate actual polishing in which polished new surfaces appear one after another, a new surface is created by scanning a range of 0.5 μm × 0.5 μm at 1 Hz with a load of 0.73 μN as preprocessing.
(3) The probe of the AFM apparatus is pressed against the new surface under the following measurement (pressing) conditions.
[Measurement (pushing) conditions]
Glass substrate moving distance: 100 nm
Approach speed: 1Hz (200nm / s)
Measurement location: Near the center of the new surface 0.5μm × 0.5μm
Number of measurements: N = 3 times at different locations
Cantilever: NP-S (Si3N4 chip) manufactured by Veeco
Folding (pushing end) set value: Cantilever warping amount = 40 nm
(4) The uppermost surface of the penetration depth is set to a position where the probe comes into contact with the surface of the glass substrate to be measured and the cantilever starts to warp. Further, the probe is pushed in and pushed when the cantilever warpage reaches 40 nm. And that position is the bottom surface. The difference in position between the uppermost surface and the lowermost surface is defined as the penetration depth, and the average of three times is defined as the penetration depth of the probe.