JP4637003B2 - Manufacturing method of hard disk substrate - Google Patents

Description

  The present invention relates to a polishing liquid composition and a method for producing a substrate.

  In recent years, memory hard disk drives have been required to be smaller and have higher capacities, and efforts have been made to reduce the flying height of the magnetic head to reduce the unit recording area in order to increase the recording density. On the other hand, the surface quality required for a polished substrate in the manufacturing process of a magnetic disk substrate is becoming stricter year by year, and surface roughness, micro waviness, and protrusions are reduced in response to the low flying height of the magnetic head. There is a need to reduce. Further, in order to increase the recording area per hard disk, it is required to be flat up to the outer peripheral edge of the substrate, and it is important to suppress roll-off (end surface droop) in polishing the substrate. .

Patent Document 1 discloses a polishing liquid using an oxyalkylene alkyl sulfate, but it cannot be said that roll-off reduction is sufficient.
International Publication No. 98/21289 Pamphlet

  Accordingly, the present invention provides a polishing composition that is effective in reducing roll-off at the outer peripheral edge of a substrate, and in particular, reducing roll-off necessary for increasing the capacity of a hard disk, and a method for manufacturing a substrate with reduced roll-off. The issue is to provide.

That is, the gist of the present invention is as follows.
[1] A polishing composition containing silica, an acid, a surfactant, and water, wherein (a) the solubility of the acid in water at 25 ° C. is 1 g / 100 g or more of a saturated aqueous solution, and (b) the surfactant is A sulfonic acid represented by the following general formula (1) or a salt thereof, and (c) a polishing liquid composition having a polishing liquid composition having a pH of 0 to 3,
RO- (AO) _n -SO ₃ H (1)
[In the formula, R represents a hydrocarbon group having 3 to 20 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and n represents 1 to 6 in terms of the average added mole number of AO. ]
[2] The polishing composition according to [1], further containing an oxidizing agent, and
[3] A substrate having a step of supplying the polishing composition according to [1] or [2] at a supply rate of 0.05 mL / min or more per 1 cm ^{2 of the} substrate to be polished and polishing at a polishing pressure of 5 to 50 kPa. It relates to a manufacturing method.

  By using the polishing composition of the present invention in a polishing process in a manufacturing process of a substrate for a hard disk, for example, it is possible to remarkably reduce the end face of the outer peripheral edge of the substrate, i.e., roll-off. There is an effect that the substrate can be manufactured.

  The polishing liquid composition of the present invention uses silica as an abrasive and combines a surfactant comprising a sulfonic acid having a specific structure or a salt thereof with an acid having a specific solubility in water, and has a specific pH. There is one feature in having.

  Examples of the silica used in the present invention include colloidal silica, fumed silica, and surface-modified silica. Among these, colloidal silica is preferable from the viewpoint of obtaining a higher level of flatness on the surface of the substrate to be polished. The colloidal silica may be a commercially available one or one obtained by a known production method or the like produced from a silicic acid aqueous solution. The usage form of silica is preferably a slurry from the viewpoint of operability.

  The average particle size of the primary particles of silica is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm from the viewpoint of improving the polishing rate regardless of whether silica is used alone or in combination of two or more. From the viewpoint of reducing the surface roughness (centerline average roughness: Ra, Peak to Valley value: Rmax), it is preferably 40 nm or less, more preferably 35 nm or less, still more preferably 30 nm or less, and even more. Preferably it is 25 nm or less, and more preferably 20 nm or less. Therefore, the average particle diameter of the primary particles is preferably 1 to 40 nm, more preferably 1 to 35 nm, still more preferably 3 to 30 nm, still more preferably 5 to 25 nm, and further preferably 5 to 20 nm. When primary particles are aggregated to form secondary particles, the average particle size of the secondary particles is preferably 5 from the viewpoint of improving the polishing rate and reducing the surface roughness of the substrate. It is ˜150 nm, more preferably 5 to 100 nm, still more preferably 5 to 80 nm, still more preferably 5 to 50 nm, and even more preferably 5 to 30 nm.

  Further, the average particle size of the primary particles of the silica is determined by using an image observed with a transmission electron microscope to obtain a particle size (D50) at which the cumulative volume frequency from the small particle size side of the primary particles becomes 50%. The value is the average particle size of the primary particles. The average particle diameter of the secondary particles can be measured as a volume average particle diameter using a laser light scattering method.

  As a particle size distribution of silica, D90 / D50 is preferably 1 to 3, more preferably 1.3 to 3 from the viewpoint of achieving reduction of nanoscratches, reduction of surface roughness, and high polishing rate. Note that D90 is a particle size at which the cumulative volume frequency from the small particle size side of the primary particles becomes 90% using an image observed with a transmission electron microscope.

  From the viewpoint of improving the polishing rate, the content of silica in the polishing composition is preferably 0.5% by weight or more, more preferably 1% by weight or more, still more preferably 3% by weight or more, and even more preferably 5%. From the viewpoint of improving the surface properties, it is preferably 20% by weight or less, more preferably 15% by weight or less, still more preferably 13% by weight or less, and even more preferably 10% by weight or less. That is, the content is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, still more preferably 3 to 13% by weight, and even more preferably 5 to 10% by weight.

The acid used in the present invention has a solubility in water at 25 ° C. of 1 g or more per 100 g of a saturated aqueous solution.
The acid solubility in the present invention represents the mass (g) of acid contained in 100 g of a saturated aqueous solution of acid at 25 ° C. The acid solubility is described, for example, in the revised 4th edition, Chemical Handbook (Basic) II, pp156-178 (Edited by Chemical Society of Japan).

  The acid is preferably an acid having a solubility of 2 g or more, more preferably 3 g or more, further preferably 4 g or more, even more preferably 5 g or more, and even more, from the viewpoint of improving the polishing rate and reducing roll-off. An acid of 6 g or more is desirable. Examples of the acid include inorganic acids such as sulfuric acid, sulfurous acid, persulfuric acid, nitric acid, hydrochloric acid, pyrophosphoric acid, phosphonic acid, phosphoric acid, and amidosulfuric acid, 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1- Diphosphonic acid (HEDP), aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,1-triphosphonic acid, methane Hydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, organic phosphonic acids such as α-methylphosphonosuccinic acid, aminocarboxylic acids such as glutamic acid and picolinic acid And carboxylic acids such as oxalic acid, nitroacetic acid, maleic acid and oxaloacetic acid. Among these, from the viewpoint of reducing scratches and roll-off, inorganic acids and organic phosphonic acids having high water solubility are preferable. Among inorganic acids, sulfuric acid, nitric acid, hydrochloric acid, and perchloric acid are more preferable. Among organic phosphonic acids, HEDP, aminotri (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphonic acid) are more preferable. These acids may be used alone or in combination of two or more.

  These acids used in the present invention may be in the form of partially neutralized salts. Preferred examples of such salts include sodium citrate, sodium sulfate, sodium nitrate and the like.

  The content of the acid in the polishing composition is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and further preferably 0.4% by weight or more from the viewpoint of reducing roll-off and improving the polishing rate. Further, from the viewpoint of influence on the human body and corrosion of the polishing apparatus, the acid content is preferably 2% by weight or less, more preferably 1.5% by weight or less, and further preferably 1% by weight or less. Therefore, from the viewpoint of reduction in roll-off and working environment, 0.1 to 2% by weight is preferable, 0.2 to 1.5% by weight is more preferable, and 0.4 to 1% by weight is further preferable.

  In the present invention, among acids, an acid whose standard electrode potential (25 ° C.) of the aqueous solution shows a value of 1 V or more is treated as an oxidizing agent. The standard electrode potential of the aqueous solution system is described in, for example, Revised 4th edition, Chemical Handbook (Basic) II, pp464-468 (Edited by Chemical Society of Japan). Here, the standard electrode potential of acid refers to the acid anion.

As the acid used in the present invention, it is preferable to use one having a pKa of 4 or less from the viewpoint of reducing roll-off. Among these, from the viewpoint of improving the polishing rate and reducing roll-off, an acid having a pKa of 3 or less is preferable, more preferably 2 or less, still more preferably 1.5 or less, and even more preferably 1 or less.
The acid corresponding to the sulfonic acid as the surfactant used in the present invention is not included in the “acid” used in the polishing composition of the present invention.

The surfactant used in the polishing composition of the present invention is a sulfonic acid represented by the following general formula (1) or a salt thereof.
RO- (AO) _n -SO ₃ H (1)
[In the formula, R represents a hydrocarbon group having 3 to 20 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and n represents 1 to 6 in terms of an average added mole number of AO. ]

  R may be a saturated hydrocarbon or an unsaturated hydrocarbon, and may have a linear structure or a branched structure. Further, it may be an aliphatic hydrocarbon or an aromatic hydrocarbon. Furthermore, in R, a part of the hydrocarbon hydrogen atoms may be substituted with other atoms or substituents within the scope of the effects of the present invention. From the viewpoint of reducing roll-off, R is preferably an alkyl group having 6 to 20 carbon atoms (including the substituted hydrocarbon, the same shall apply hereinafter). Further, from the viewpoint of operability such as foaming resistance, R 6 More preferred are ˜18 alkyl groups.

  AO is an oxyalkylene group having 2 to 4 carbon atoms. Examples of these oxyalkylene groups include an oxyethylene group, an oxypropylene group, an oxytrimethylene group, and an oxybutylene group. These may be one kind alone or a mixture thereof.

  The added mole number n of the oxyalkylene group in the sulfonic acid is 1-6. From the viewpoint of suppressing adsorption of the sulfonic acid to the silica surface and enhancing the dispersion stability of the silica, the number n of oxyalkylene groups added is preferably 1 to 4, and more preferably 1 to 3.

  Examples of the counter ion of the sulfonate used in the polishing liquid composition of the present invention include primary to quaternary ammonium ions in addition to inorganic cations such as alkali metal ions, alkaline earth metal ions, and animmonium ions. An organic cation is mentioned. From the viewpoint of solubility of sulfonate in water, alkali metal ions are preferred.

  Examples of the surfactant preferably used in the present invention include sodium polyoxyethylene (2 mol addition) sodium lauryl sulfate and polyoxyethylene (4 mol addition) sodium lauryl sulfate.

The effect of the present invention can be achieved by adjusting the pH of the polishing composition to 0 to 3 using the surfactant as described above together with an acid having high solubility in water. For example, roll-off can be significantly reduced by using sodium polyoxyethylene lauryl sulfate together with sulfuric acid having a solubility in water (25 ° C.) of 80.3 g / saturated aqueous solution 100 g.
The surfactant in the polishing composition may be used alone or in combination of two or more.

  The content of the surfactant in the polishing composition is preferably 0.005 to 2% by weight, more preferably 0.01 to 2% by weight, still more preferably 0.025 to 2% by weight, and still more preferably, from the viewpoint of reducing roll-off. 0.05-2% by weight is desirable. Furthermore, considering operability such as foaming resistance, 0.05 to 0.5% by weight is even more preferable.

  Examples of the water used in the polishing composition of the present invention include distilled water, ion exchange water, and ultrapure water. From the viewpoint of the surface cleanliness of the substrate to be polished, ion exchange water and ultrapure water are preferable, and ultrapure water is more preferable. The content of water in the polishing composition is preferably 60 to 99% by weight, more preferably 70 to 98% by weight. Moreover, you may contain organic solvents, such as alcohol, in the range which does not inhibit the effect of this invention.

  The pH of the polishing composition of the present invention is 0-3. The pH can be adjusted with the sulfonic acid of the general formula (1) or a salt thereof, but from the viewpoint of reducing roll-off, the pH is preferably adjusted with an acid having a solubility in water at 25 ° C. of 1 g / saturated aqueous solution 100 g or more. From the viewpoint of reducing roll-off and improving the polishing rate, the pH is preferably 2.8 or less, more preferably 2.5 or less, and even more preferably 2 or less. Further, from the viewpoint of corrosion of the polishing apparatus, the pH is preferably 0.1 or more, more preferably 0.5 or more, and further preferably 0.8 or more. Therefore, 0.1 to 2.8 is preferable, 0.5 to 2.5 is more preferable, and 0.8 to 2 is even more preferable from the viewpoint of roll-off reduction and workability environment.

  The polishing liquid composition of the present invention can further improve the polishing rate without deteriorating roll-off by containing an oxidizing agent. As the oxidizing agent, peroxides, permanganates, chromates, nitrates, peroxo acids or salts thereof, oxygen acids or salts thereof, metal salts, and the like can be used.

  As the peroxide, hydrogen peroxide, sodium peroxide, barium peroxide, etc .; As the permanganate, potassium permanganate, etc .; As the chromate, chromate metal salt, dichromate metal salt, etc .; Examples of nitrates include iron (III) nitrate, ammonium nitrate, and the like. Peracetic acid, perbenzoic acid, perphthalic acid, etc .; oxygen acid or its salts include hypochlorous acid, hypobromite, hypoiodous acid, chloric acid, bromic acid, iodic acid, sodium hypochlorite, Calcium hypochlorite, etc .; Examples of metal salts include iron (III) chloride, iron (III) sulfate, iron (III) citrate, and iron (III) ammonium sulfate. It is. Preferable oxidizing agents include hydrogen peroxide, iron (III) nitrate, peracetic acid, ammonium peroxodisulfate, iron (III) sulfate, and iron (III) ammonium sulfate. These oxidizing agents may be used alone or in combination of two or more. It is preferable to use hydrogen peroxide from the viewpoint that ions derived from the oxidizing agent are difficult to adhere to the surface of the object to be polished.

  The content of the oxidizing agent in the polishing liquid composition is preferably 0.002% by weight or more, more preferably 0.005% by weight or more, further preferably 0.007% by weight or more, and still more preferably 0.01% by weight, from the viewpoint of improving the polishing rate. From the viewpoint of reducing surface roughness and waviness, and reducing surface defects such as pits and scratches to improve surface quality, it is preferably 20% by weight or less, more preferably 15% by weight or less, and still more preferably Is 10% by weight or less, and more preferably 5% by weight or less. Therefore, in order to improve the polishing rate while maintaining the surface quality, the content is preferably 0.002 to 20% by weight, more preferably 0.005 to 15% by weight, still more preferably 0.007 to 10% by weight, and even more preferably. Is 0.01 to 5% by weight.

  The polishing liquid composition of the present invention may contain a radical scavenger, a rust inhibitor, an antifoaming agent, an antibacterial agent, and the like as necessary. The content of these other optional components in the polishing liquid composition is preferably 0 to 10% by weight, more preferably 0 to 5% by weight.

The polishing composition of the present invention can be prepared, for example, as follows. That is, an aqueous surfactant solution is prepared, and an acid having a solubility in water (25 ° C.) of 1 g / 100 g or more of a saturated aqueous solution and a silica slurry are added to prepare a polishing liquid composition. If necessary, optional components are further blended and supplied to the polishing machine. The surfactant and optional components may be added and mixed in advance before being supplied to the polishing machine, or may be added and mixed in the process of supplying to the polishing machine (for example, in the supply pipe or on the polishing substrate). .
Silica may be mixed in the state of a concentrated slurry when preparing the polishing composition, or may be mixed after being diluted with water or the like. Furthermore, it may be added and mixed in the process of supplying to the polishing machine as described above.

When preparing the polishing composition of the present invention, it is preferable from the viewpoint of silica stability that an aqueous acid solution is prepared in advance, and then a silica slurry is added thereto and mixed. Moreover, it is preferable to mix the silica slurry after previously dissolving other optional components in water to form an aqueous solution. Furthermore, when mixing the silica slurry, it is preferable to mix at a speed at which the silica particles do not dry from the viewpoint of preventing aggregation due to drying of the silica particles.
When mixing the silica slurry, from the viewpoint of dispersibility of silica, it is preferable to add and mix the silica slurry while stirring an aqueous solution of components other than silica.

The present invention also relates to a substrate polishing method and a substrate manufacturing method. By polishing the substrate to be polished using the polishing composition of the present invention obtained as described above, it is possible to produce a substrate in which roll-off is suppressed. Specifically, the substrate is sandwiched by a polishing machine with a non-woven organic polymer polishing cloth, etc., and the polishing composition of the present invention is supplied to the substrate at 0.05 mL / min or more per 1 cm ^{2 of the} substrate to be polished. The roll-off can be effectively suppressed by polishing the substrate by moving the polishing platen and the substrate at a polishing pressure of 5 to 50 kPa.

  In the polishing method and the manufacturing method of the present invention, the polishing pressure refers to the pressure of the surface plate applied to the polishing surface of the substrate to be polished during polishing. When the polishing pressure is set to 5 kPa or more, the substrate to be polished is pressed by the surface plate, the substrate to be polished is less likely to vibrate, and it is difficult to apply a load at the outer peripheral edge of the substrate. Presumed. Considering productivity, it is preferably 7 kPa or more, more preferably 10 kPa or more. On the other hand, since scratches are likely to occur when the polishing pressure is increased, the platen pressure is 50 kPa or less, preferably 30 kPa or less, more preferably 20 kPa or less. Therefore, in the polishing method and the production method of the present invention, the polishing pressure is 5 to 50 kPa, preferably 7 to 30 kPa, and more preferably 10 to 20 kPa. The polishing pressure can be adjusted by applying air pressure or weight to the surface plate and / or the substrate.

The supply rate of the polishing composition in the polishing method and the production method of the present invention is 0.05 mL / min or more per 1 cm ^{2 of the} substrate to be polished. At 0.05 mL / min or more, the frictional resistance between the polishing cloth and the substrate to be polished is suppressed, so the substrate to be polished is less likely to vibrate, and the load at the outer peripheral edge of the substrate is difficult to apply, effectively reducing roll-off. Presumed to be possible. The flow rate is preferably 0.07 mL / min or more, more preferably 0.09 mL / min or more, further preferably 0.12 mL / min or more, even more preferably 0.15 mL / min or more from the viewpoint of reducing roll-off due to increased frictional resistance. It is. Further, from the viewpoint of economically reducing roll-off, it is preferably 0.50 mL / min or less, more preferably 0.30 mL / min or less, further preferably 0.25 mL / min or less per 1 cm ^{2 of the} substrate to be polished. Accordingly, the supply rate of the polishing composition is preferably 0.07 to 0.50 mL / min, more preferably 0.09 to 0.50 mL / min, still more preferably 0.12 to 0.30 mL / min, and even more preferably, per 1 cm ^{2 of the} substrate to be polished. 0.15-0.25 mL / min.

  Examples of the method for supplying the polishing composition of the present invention to the substrate to be polished include a method of continuously supplying using a pump or the like. At that time, in addition to the method of supplying the polishing liquid composition as one liquid containing all the components, considering the stability of the polishing liquid composition, etc., it is divided into several kits and supplied in two liquids or more. You can also. In the latter case, for example, the several kits are mixed in the supply pipe or on the polishing substrate to form the polishing liquid composition of the present invention.

  The polishing method is preferably performed in the second and subsequent steps among the plurality of polishing steps, and more preferably in the final polishing step. At that time, in order to avoid mixing of the polishing material and polishing liquid composition in the previous step, different polishing machines may be used, and when different polishing machines are used, the substrate is used for each polishing process. Is preferably washed. The polishing machine is not particularly limited.

  The surface properties of the substrate used in the substrate polishing method and the substrate manufacturing method of the present invention are not particularly limited, but in order to manufacture a substrate for high recording density, for example, the surface roughness (Ra) is about 1 nm. A substrate having surface properties is suitable. The surface roughness is a measure of surface smoothness, and the evaluation method is not limited. For example, the surface roughness is evaluated as roughness measurable at a wavelength of 10 μm or less with an atomic force microscope, and expressed as centerline average roughness Ra. be able to.

  Examples of the material of the substrate to be polished preferably used in the present invention include metals, metalloids such as silicon, aluminum, nickel, tungsten, copper, tantalum, and titanium, or alloys thereof; glass, glassy carbon, amorphous carbon Glass materials such as alumina; ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, and titanium carbide; and resins such as polyimide resins. Among these, an object to be polished containing a metal such as aluminum, nickel, tungsten, or copper and an alloy containing such a metal as a main component is preferable. For example, a Ni—P plated aluminum alloy substrate or a glass substrate such as crystallized glass or tempered glass is more suitable, and a Ni—P plated aluminum alloy substrate is more suitable.

  The shape of the object to be polished is not particularly limited. For example, the shape having a flat portion such as a disk shape, a plate shape, a slab shape, or a prism shape, or the shape having a curved surface portion such as a lens can be used. It becomes the object of polishing using. Among them, it is more suitable for polishing a disk-shaped workpiece.

  The polishing composition of the present invention is suitably used for polishing precision component substrates. For example, it is suitable for polishing a substrate of a disk recording medium such as a magnetic disk, an optical disk, a magneto-optical disk, a photomask substrate, a glass for liquid crystal, an optical lens, an optical mirror, an optical prism, a semiconductor substrate and the like. The polishing composition of the present invention, the substrate polishing method, and the substrate manufacturing method can remarkably reduce roll-off important in increasing the capacity, and are particularly suitable for polishing a hard disk substrate and manufacturing the same. ing.

  As a substrate to be polished, a Ni-P plated aluminum alloy substrate (thickness: 1.27 mm, outer periphery: 95 mmφ, inner periphery: 25 mmφ), which is roughly polished in advance with a polishing liquid containing an alumina abrasive and Ra is set to 1 nm is used. Polishing evaluation was performed.

  After adding a predetermined amount of surfactants listed in Table 1, sulfuric acid (98% by weight, manufactured by Wako Pure Chemical Industries) and / or HEDP aqueous solution (60% by weight, manufactured by Solusia Japan) to water Hydrogen peroxide water (35% by weight, manufactured by Asahi Denka Kogyo Co., Ltd.) is added and mixed. Finally, colloidal silica slurry (average primary particle size: 22 nm, active ingredient 20-40% by weight, medium: water) is stirred. In addition, a polishing composition was obtained.

1. Polishing conditions / polishing tester: Speed Fam Co., double-sided 9B polishing machine / polishing cloth: manufactured by Fujibow Co., Ltd., polishing pad for finishing (thickness 0.9 mm, average hole diameter 30 μm)
・ Surface plate rotation speed: 45 rotations / minute ・ Polishing liquid composition supply rate: 0.1 to 0.2 mL / min ・ Polishing time: 5 minutes ・ Polishing pressure (table plate pressure): 6 to 15 kPa
・ Number of loaded substrates: 10

2. Roll-off measurement conditions and measurement equipment: New View 5032 made by Zygo
・ Lens: 2.5x ・ Zoom: 0.5x ・ Analysis software: Zygo Metro Pro

The outer peripheral edge of the disk 43.0 to 47.0 mm from the center of the disk was used as the measurement area. Points of 43.0 mm, 44.0 mm, and 46.6 mm on a straight line from the center of the disk toward the outer peripheral direction are designated as points A, B, and C, respectively, as shown in FIG. The position in the thickness direction of the disk at point C ′ on the disk surface with respect to the extended line connecting points A and B was measured for the substrate before polishing and after polishing, and roll-off before polishing and roll-off after polishing (nm, respectively). ). The analysis software was used to calculate this position. According to the following formula, the roll-off difference per unit polishing weight (mg) was calculated by dividing the roll-off difference before and after the polishing test by the polishing amount to obtain the roll-off value (nm / mg). For one polishing, four points were measured per side for both sides and two substrates, and the average value for a total of 16 points is shown in Table 1.
Roll-off value (nm / mg) = {roll-off before polishing (nm)-roll-off after polishing (nm)} / polishing weight (mg)

3. pH Measurement Conditions The pH of the polishing composition was measured at 25 ° C. using a pH meter (manufactured by Toa Denpa Kogyo Co., Ltd., glass type hydrogen ion concentration index meter “HM-30G”).

4). Measurement method of polishing rate The weight change of the substrate before and after polishing was measured for 10 substrates (BP-210S manufactured by Sartrius), and the value obtained by dividing the average value by the polishing time was taken as the weight change rate. The polishing rate (μm / min) was calculated from the Ni—P density (8.4 g / cm ³ ) and the substrate single-sided area (65.87 cm ² ) according to the following formula.
Weight change rate = {Substrate weight before polishing (g)-Substrate weight after polishing (g)} / Polishing time (min)
Polishing rate (μm / min) = Weight change rate (g / min) / Substrate single side area (mm ² ) / Ni-P plating density (g / cm ³ ) × 10 ⁶

From the results shown in Table 1, the substrates obtained using the polishing liquid compositions of Examples 1 to 16 (however, Example 14 is a reference example) are compared with those of Comparative Examples 1 to 3, It can be seen that the roll-off is suppressed.

  The polishing composition of the present invention, the method for polishing a substrate, and the method for manufacturing a substrate are suitably used for polishing a substrate for a disk recording medium such as a magnetic disk, an optical disk, and a magneto-optical disk.

FIG. 1 is a cross-sectional view of a substrate showing measurement positions at the time of roll-off measurement.

Explanation of symbols

A: Point at a distance of 43.0 mm from the center of the disk toward the outer periphery direction B: Point at a distance of 44.0 mm from the center of the disk toward the outer periphery direction C: 46.6 mm from the center of the disk toward the outer periphery direction Point C 'at a distance C': A point where a straight line passing through points A, B, and C intersects with a line perpendicular to point C and the disk surface X: roll-off

Claims (6)

A polishing composition comprising silica, acid, surfactant and water, wherein (a) the solubility of acid in water at 25 ° C. is 1 g / saturated aqueous solution 100 g or more, (b) the surfactant is represented by the following general formula (1) sulfonic acid or a salt thereof and (c) pH is the polishing composition is 0-3, feed rate of more than 0.05 mL / min per ² to be polished substrate 1cm of the polishing composition, The manufacturing method of the board | substrate for hard disks which has the process of grind | polishing with the grinding | polishing pressure of 7-20 kPa.
R—O— (AO) _n —SO ₃ H (1)
[Wherein, R represents a hydrocarbon group having 3 to 20 carbon atoms, AO represents an oxyalkylene group having 2 to 4 carbon atoms, and n represents an average added mole number of AO of 1 to 4. ] The production method according to claim 1, wherein R in the general formula (1) is an alkyl group having 6 to 20 carbon atoms. The production method according to claim 1 or 2, wherein the content of the surfactant is 0.005 to 2% by weight. Furthermore, the manufacturing method in any one of Claims 1-3 containing an oxidizing agent. The supply rate of the polishing composition is 1 cm for the substrate to be polished. ² The manufacturing method in any one of Claims 1-4 which is 0.15-0.25 mL / min per. The production method according to claim 1, wherein the acid (a) is at least one selected from the group consisting of inorganic acids and organic phosphonic acids.

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