JP2003211351A - Method of reducing micro projections - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of reducing micro projections of a polishing object substrate capable of economically and highly speedily reducing the surface defect such as a small surface roughness, a projection, and a polishing flaw on a workpiece after polishing, and especially the micro projection detected by a surface shape analysis using an atomic force microscope for finishing polishing of a memory hard disk and polishing for a semiconductor device, to provide a substrate for a magnetic disk obtained by the same method, and to provide manufacturing method for a substrate using the same method. <P>SOLUTION: This method reduces the micro projection of the polishing object substrate detected by the surface analysis using the atomic force microscope (AFM), and has a process of polishing the substrate using polishing liquid composition, which includes water, polishing material, and acid compound, shows acid pH, and has a concentration of the polishing material less than 10 wt.%. The substrate for the magnetic disk is provided by the same method. The method is to manufacture the substrate for the magnetic disk reducing the micro projection detected by the surface analysis using the atomic force microscope (AFM) using the same method. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing microscopic protrusions in surface analysis using an atomic force microscope (AFM), a magnetic disk substrate obtained by using the method, and a method for manufacturing a substrate using the method. Regarding the method.

[0002]

2. Description of the Related Art In recent years, memory hard disk drives are required to have a high capacity and a small diameter, and in order to increase the recording density, it is required to reduce the flying height of a magnetic head or reduce the unit recording area. Along with this, the surface quality required after polishing in the manufacturing process of magnetic disk substrates has become stricter year by year, and in response to low head flying, surface roughness, minute waviness, roll-off, reduction of protrusions and The size and depth of scratches and pits that are permissible corresponding to the decrease in the unit recording area are becoming smaller and smaller.

Also in the semiconductor field, high integration,
The wiring is becoming finer with the increase in speed. In the semiconductor device manufacturing process as well, when the photoresist is exposed, the depth of focus becomes shallower as the wiring becomes finer. Therefore, further smoothing of the pattern formation surface is desired.

Particularly, in order to realize a high recording density of a memory hard disk drive, the spacing between the head and the disk has become narrower year by year, and as a result, an atomic force microscope (AFM), which has not been a problem until now, was used. Minute protrusions detected by surface shape analysis (height: 1 to 30 nm,
(Width: 1 to 100 nm) has become a problem.

[0005]

DISCLOSURE OF THE INVENTION An object of the present invention is to finish polishing a memory hard disk and to polish a semiconductor element, and after polishing, the surface to be polished has a small surface roughness and has a surface such as a protrusion or a polishing scratch. A method for reducing defects, especially minute protrusions detected by surface shape analysis using an atomic force microscope, can be reduced economically and at high speed. It is an object to provide a disk substrate and a substrate manufacturing method using the above method.

[0006]

The summary of the present invention is as follows.
[1] A step of polishing a substrate to be polished using a polishing composition containing water, an abrasive, and an acid compound, having an acidic pH and an abrasive concentration of less than 10% by weight. A method for reducing minute protrusions on a substrate to be polished detected by surface analysis using an atomic force microscope (AFM), [2] a magnetic disk substrate obtained by using the method described in [1] above, and [3] The present invention relates to a method for manufacturing a magnetic disk substrate in which minute protrusions detected by surface analysis using an atomic force microscope (AFM) are reduced by using the method described in [1] above.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, minute protrusions (hereinafter, also simply referred to as minute protrusions) detected by surface shape analysis using an atomic force microscope have a height of 1 to 30 nm and a width of 1 to 1 nm.
It means a protrusion having a size of 00 nm. Here, examples of the surface shape analysis method using an atomic force microscope include the methods described in Examples below.

As described above, the method for reducing fine projections of the present invention comprises water, an abrasive, and an acid compound, and has a pH of acid and an abrasive concentration of less than 10% by weight. Is used to polish the substrate to be polished.

As the abrasive used in the present invention, an abrasive generally used for polishing can be used.
Examples of the abrasive include metal; metal or metalloid carbide, nitride, oxide, boride; diamond and the like.
Metal or metalloid elements are 2A of the periodic table (long period type),
It is derived from 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A or 8A group. Specific examples of the abrasive include aluminum oxide, silicon carbide, diamond, magnesium oxide, zinc oxide, titanium oxide, cerium oxide, zirconium oxide, silica, and the like, and the use of one or more of these improves the polishing rate. It is preferable from the viewpoint. Among them, aluminum oxide, silica, cerium oxide, zirconium oxide, titanium oxide and the like are suitable for polishing substrates for precision parts such as semiconductor wafers, semiconductor elements and substrates for magnetic recording media. For aluminum oxide, α, θ, γ
Various crystal systems are known, and they can be appropriately selected and used according to the application. Among them, silica, particularly colloidal silica, is suitable for final finishing polishing of substrates for high recording density memory magnetic disks and polishing for semiconductor device substrates which require higher smoothness.

The average particle size of the primary particles of the abrasive is preferably 0.001 to 3 μm, more preferably 0.01 to 3 μm, still more preferably 0.02 to 0, from the viewpoint of improving the polishing rate.
8 μm, particularly preferably 0.05 to 0.5 μm. Furthermore, when the primary particles are aggregated to form secondary particles, the average particle diameter of the secondary particles is the same from the viewpoint of improving the polishing rate and reducing the surface roughness of the object to be polished. , Preferably 0.05 to 3 μm, more preferably 0.1 to
The thickness is 1.5 μm, particularly preferably 0.2 to 1.2 μm. The average particle diameter of the primary particles of the abrasive can be determined by observing with a scanning electron microscope (preferably 3000 to 30000 times) and performing image analysis to measure the biaxial average particle diameter. The average particle diameter of the secondary particles can be measured as a volume average particle diameter by using a laser light diffraction method.

Further, in the present invention, it is more preferable to use silica particles as the abrasive from the viewpoint of reducing fine projections and surface roughness (Ra) to improve the surface quality. Examples of the silica particles include colloidal silica particles, fumed silica particles, surface-modified silica particles, and the like. Among them, colloidal silica particles are preferable. In addition,
The colloidal silica particles can be obtained, for example, by a production method in which they are produced from an aqueous solution of silicic acid.

The average particle size of the primary particles of the silica particles is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.
From the viewpoint of reducing the surface roughness (Ra), it is preferably 0.6 μm or less, more preferably 0.5 μm.
Or less, more preferably 0.3 μm or less, particularly preferably
It is 0.2 μm or less. The average particle size is preferably 0.001
To 0.6 μm, more preferably 0.001 to 0.5 μm, even more preferably 0.01 to 0.3 μm, particularly preferably 0.02 to 0.2
μm. The particle diameter can be determined by observing with a scanning electron microscope (preferably 3000 times to 100,000 times), image analysis, and measuring the biaxial average diameter.

Further, from the viewpoint of preventing the generation of fine protrusions, the silica particles are integrated from the small particle size side to the particle size (D50) at which the integrated particle size distribution (number basis) from the small particle size side is 50%. Particle size distribution (number basis) is 90% (D
90) ratio (D90 / D50) is 1.0 to 1.5, and D
It is preferable that the particle size distribution of 50 is 10 to 200 nm. The particle size distribution indicates the particle size distribution of the entire silica particles, and, for example, when two or more kinds of silica particles are used in combination, they are measured for the silica particles mixed with each other.

In the above particle size distribution, D90 / D50 is
1.0 to 1.5 is preferable, 1.0 to 1.45 is more preferable, 1.0 to 1.4 is still more preferable, 1.0 to 1.35 is particularly preferable.
Is.

In the particle size distribution, D50 is 10 to
200 nm is preferable, more preferably 20 to 180 nm, further preferably 30 to 150 nm, particularly preferably 50 to 10 nm.
It is 0 nm. The D50 is preferably 10 nm or more from the viewpoint of obtaining a high polishing rate, and from the viewpoint of preventing generation of surface defects such as fine protrusions and obtaining good surface smoothness, 20
It is preferably 0 nm or less.

The particle size of the silica particles used in the present invention can be determined by the following method using a scanning electron microscope (hereinafter referred to as SEM). That is, the polishing liquid composition containing silica particles is diluted with ethanol so that the silica particle concentration becomes 0.5% by weight. The diluted solution is uniformly applied to a sample stage for SEM heated to about 50 ° C. Then, the excess solution is sucked with a filter paper and air-dried uniformly so that the solution does not aggregate.

Pt-Pd was vapor-deposited on naturally dried silica particles, and about 500 particles were observed in the visual field using a field emission scanning electron microscope (FE-SEM: S-4000 type) manufactured by Hitachi, Ltd. The magnification is adjusted to 3000 times to 100,000 times so that the silica particles of (1) are observed, and two points are observed on one sample stage to take a photograph. Photo taken (10.16)
(cm x 12.7 cm) is enlarged to A4 size by a copier, etc., and the particle size of all the photographed silica particles is measured with a caliper or the like and tabulated. This operation is repeated several times so that the number of measured silica particles is 2000 or more. Increasing the number of measurement points by SEM is more preferable from the viewpoint of obtaining an accurate particle size distribution. The measured particle sizes are totaled, and the frequencies (%) are added in order from the smallest particle size, and the particle size at which the value is 50% is D50, and the particle size at which 90% is D90 is D90, and the number-based particle in the present invention is used. The diameter distribution can be obtained. The particle size distribution mentioned here is obtained as the particle size distribution of primary particles. However, aluminum oxide,
When there are secondary particles in which primary particles such as cerium oxide and fumed silica are fused, the particle size distribution can be obtained based on the particle size of the secondary particles.

The method of adjusting the particle size distribution of the silica particles is not particularly limited. For example, when the silica particles are colloidal silica, particles that become new nuclei in the growth process of the particles in the manufacturing stage are added. Therefore, it can be achieved by a method of giving the final product a particle size distribution, a method of mixing two or more silica particles having different particle size distributions, or the like.

The content of these abrasives is less than 10% by weight in the polishing composition. By adjusting to such a concentration range, it is possible to significantly reduce the fine protrusions on the substrate to be polished which are detected by the surface analysis using AFM. In addition, the content of the abrasive is preferably 9% by weight or less, more preferably 8% by weight or less, and further preferably 7% by weight or less, from the viewpoint of reducing fine protrusions and economical efficiency. Further, the content is preferably 0.5% by weight or more, more preferably 1% by weight or more, further preferably 2% by weight or more, particularly preferably 3% by weight or more, from the viewpoint of improving the polishing rate.

That is, the content is preferably 0.5% by weight or more and less than 10% by weight, more preferably 1 to 9% by weight, further preferably 2 to 8% by weight, particularly preferably 3% by weight.
~ 7% by weight.

In the present invention, the acid compound is a compound showing an acidity of pK1 of 7 or less. From the viewpoint of reducing fine protrusions, compounds having a pK1 of 3 or less are preferable. From the viewpoint of improving the polishing rate, a compound having a pK1 of 7 or less and having the ability to chelate the metal contained on the surface of the object to be polished is preferable. Specifically, aminopolycarboxylic acids such as ethylenediaminetetraacetic acid and salts thereof, citric acid, malic acid, tartaric acid, oxalic acid, malonic acid, succinic acid, maleic acid, itaconic acid, organic carboxylic acids such as sulfosalicylic acid and I have that salt. From the viewpoint of reducing micro scratches, a compound having a pK1 of 3 or less is preferable, a pK1 of 2.5 or less is more preferable, and a pK1 of 2.
A compound having a pK1 of 0 or less, particularly preferably a pK1 of 1.5 or less, and a compound having a pK1 of 1 or less (that is, a compound exhibiting strong acidity that cannot be represented by pK1) are most preferable. Specifically, nitric acid, sulfuric acid, sulfurous acid, persulfuric acid, hydrochloric acid, perchloric acid,
Phosphoric acid, phosphonic acid, phosphinic acid, pyrophosphoric acid, oxalic acid, amidosulfate, aspartic acid, 2-aminoethylphosphonic acid, glutamic acid, picolinic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (hereinafter, HEDP
(Also referred to as) and the like. Among these, nitric acid, HEDP, sulfuric acid, perchloric acid and hydrochloric acid are preferable, and nitric acid, HEDP and sulfuric acid are particularly preferable, from the viewpoint of reducing fine projections. You may use these acids individually or in mixture of 2 or more types. Here, pK1 is usually the logarithmic value of the reciprocal of the acid dissociation constant (25 ° C.) of an organic compound or an inorganic compound, which is usually pKa.
And the logarithm of the reciprocal of the primary acid dissociation constant
It is K1. The pK1 of each compound is described in, for example, Revised 4th Edition Chemical Handbook (Basic Edition) II, pp316-325 (Edited by The Chemical Society of Japan) and the like.

The content of the acid compound in the polishing composition is preferably 0.0001 to 20% by weight, more preferably 0.0003 to 10% by weight, from the viewpoint of exhibiting a sufficient polishing rate and improving the surface quality. And more preferably 0.001 to 5% by weight, particularly preferably 0.0025 to 3% by weight.

The polishing composition preferably contains an oxidizing agent from the viewpoint of improving the polishing rate. Examples of the oxidizing agent include peroxide, permanganic acid or a salt thereof, chromic acid or a salt thereof, nitric acid or a salt thereof, peroxo acid or a salt thereof, oxygen acid or a salt thereof, metal salts, sulfuric acid and the like.

More specifically, peroxides include hydrogen peroxide, sodium peroxide, barium peroxide, etc .; permanganates, potassium permanganate etc .; chromates, metal chromates. Salts, metal dichromates, etc .; nitrates as iron (III) nitrate, ammonium nitrates, etc .; peroxo acids or salts thereof as peroxodisulfate, ammonium peroxodisulfate, metal salts of peroxodisulfate, peroxophosphoric acid, peroxosulfate. , Sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, etc .; as oxyacids or salts thereof, hypochlorous acid, hypobromic acid, hypoiodic acid, chloric acid, bromic acid, Iodic acid, perchloric acid, sodium hypochlorite, calcium hypochlorite, etc .; as metal salts, iron (III) chloride, iron (III) sulfate,
Examples include iron (III) citrate and iron (III) ammonium sulfate. Preferred oxidizing agents include hydrogen peroxide, iron (III) nitrate, peracetic acid, ammonium peroxodisulfate (III) sulfate, iron (III) sulfate, and the like.
In particular, hydrogen peroxide is preferable from the viewpoint that metal ions do not adhere to the surface and it is used widely and is inexpensive. You may use these oxidizing agents individually or in mixture of 2 or more types.

From the viewpoint of improving the polishing rate, the content of the oxidizing agent in the polishing 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, particularly preferably It is 0.01% by weight or more, preferably 20% by weight or less, and more preferably 15% by weight from the viewpoint of reducing surface roughness, reducing surface defects such as fine protrusions to improve surface quality and economical efficiency.
Or less, more preferably 10% by weight or less, particularly preferably
It is 5% by weight or less. The content is preferably 0.002 to
20% by weight, more preferably 0.005 to 15% by weight, further preferably 0.007 to 10% by weight, particularly preferably 0.01 to 5%
% By weight.

Water in the polishing composition is used as a medium, and the content thereof is preferably 50% by weight or more, more preferably 66 from the viewpoint of efficiently polishing the object to be polished. % By weight or more, more preferably 77% by weight or more, particularly preferably 85% by weight or more,
Also, preferably 99.4979% by weight or less, more preferably
It is 98.9947% by weight or less, more preferably 96.992% by weight or less, and particularly preferably 94.9875% by weight or less. The content is preferably 55 to 99.4979% by weight, more preferably 67 to 98.99947% by weight, further preferably 75 to 96.992% by weight, and particularly preferably 84 to 94.9875% by weight.

The concentration of each component in the polishing composition may be either the concentration at the time of producing the composition or the concentration at the time of use. Usually, a polishing composition is produced as a concentrated solution, and it is often used by diluting it.

If desired, the polishing composition may contain other components. Examples of the other components include thickeners, dispersants, rust preventives, basic substances, surfactants and the like.

The polishing composition comprises an abrasive, an acid compound, water,
If necessary, it can be prepared by mixing an oxidizing agent, other components and the like by a known method.

Although the pH of the polishing composition is acidic, it is preferable that the specific pH value be appropriately determined according to the type of the workpiece and the required performance. Although it cannot be unequivocally limited depending on the material to be polished, generally, in the case of a metal material, the pH is preferably less than 7.0, more preferably 6.0 or less, further preferably 5.0 or less, and particularly preferably 4.0 or less from the viewpoint of improving the polishing rate. is there. Further, from the viewpoint of the effect on the human body and the corrosiveness of machinery, the pH is preferably 1.0 or higher, more preferably 1.2 or higher, still more preferably 1.4 or higher, and particularly preferably 1.6 or higher. Particularly in the case of precision component substrates mainly intended for metals such as nickel-phosphorus (Ni-P) plated aluminum alloy substrates, the pH is preferably 4.5 or less, and more preferably 4.0 or less from the viewpoint of improving the polishing rate. , More preferably 3.5 or less, particularly preferably 3.0 or less. Therefore, it suffices to set the pH according to the purpose of importance, but particularly in the case of precision component substrates intended for metals such as Ni-P plated aluminum alloy substrates, the above viewpoint is taken into consideration and the pH is 1.0.
It is preferably 4.5 to 4.5, more preferably 1.2 to 4.0, still more preferably 1.4 to 3.5, and particularly preferably 1.6 to 3.0. The pH is inorganic acids such as nitric acid and sulfuric acid, organic acids such as oxalic acid, ammonium salts, aqueous ammonia, potassium hydroxide,
It can be adjusted by appropriately adding a basic substance such as sodium hydroxide or amine in a desired amount.

The method of reducing the fine protrusions of the present invention is, for example,
It has a step of polishing a substrate to be polished by preparing a polishing liquid by using the polishing liquid composition as described above or by mixing the respective components so as to have a composition of the polishing liquid composition, A substrate for precision parts can be suitably manufactured. Specific examples thereof include a non-woven fabric such as an organic polymer-based polishing cloth, preferably a polishing board having a polyurethane-based polishing cloth attached thereto, and the substrate is sandwiched between the polishing solution composition and the polishing liquid composition at a flow rate of 1 m.
0.076 to 3.8 L / min per ² , preferably 0.1
It is supplied to the polishing surface at 5 to 1.5 L / min, and the load is 2.9.
The relative velocity between the upper platen or the lower platen and the substrate to be polished is 0.1 to 2 m / sec at the center of the platen, while a constant pressure of ˜19.6 kPa, preferably 4.9 to 9.8 kPa is applied. Is a method of polishing by moving a polishing board or a substrate so that the speed becomes 0.3 to 1 m / sec.

As described above, by using the method for reducing fine projections of the present invention, not only the fine projections are efficiently removed, but also the polishing rate is improved and the occurrence of surface defects such as fine scratches and pits is suppressed. The effect that the surface smoothness such as surface roughness (Ra) can be improved is exhibited.

The substrate to be polished targeted by the method for reducing fine projections of the present invention includes, for example, metals or semimetals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium and alloys thereof, and glass, Glassy substances such as glassy carbon and amorphous carbon, alumina, silicon dioxide, silicon nitride, tantalum nitride,
A substrate made of a ceramic material such as titanium carbide or a resin such as a polyimide resin may be used. Among these,
Metals such as aluminum, nickel, tungsten, and copper and alloys containing these metals as main components are objects to be polished, or objects such as semiconductor substrates such as semiconductor elements in which they contain metals. Preferably, for example,
A Ni-P plated aluminum alloy substrate or a glass substrate such as crystallized glass or tempered glass is more preferable.
Particularly preferred is a P-plated aluminum alloy substrate.

The shape of the substrate to be polished is not particularly limited. For example, a shape having a flat surface portion such as a disk shape, a plate shape, a slab shape, a prism shape, or a shape having a curved surface portion such as a lens is an object of the present invention. Becomes Among them, it is particularly excellent in polishing a disk-shaped substrate to be polished.

The method for reducing fine protrusions of the present invention is preferably used for polishing precision component substrates. For example, it is suitable for polishing substrates for magnetic recording media such as magnetic disks, optical disks, magneto-optical disks, photomask substrates, optical lenses, optical mirrors, optical prisms, precision component substrates such as semiconductor substrates. The polishing of the semiconductor substrate is performed in a polishing step of a silicon wafer (bare wafer), a step of forming a buried element isolation film, a step of flattening an interlayer insulating film, a step of forming a buried metal wiring, a step of forming a buried capacitor, and the like. The method for reducing fine protrusions of the present invention is particularly suitable for polishing a magnetic disk substrate. Furthermore, the surface roughness (R
a) Suitable for obtaining a magnetic disk substrate of 0.3 nm or less.

In the present specification, the surface roughness (Ra) is obtained as a so-called center line roughness, and the center line average roughness obtained from a roughness curve having a wavelength component of 80 μm or less is represented by Ra. This Ra can be measured as follows.

Centerline average roughness: Ra is measured under the following conditions using a Tally Step (“Taridata 2000”) manufactured by Rank Taylor Hobson Co., Ltd. (hereinafter, terms in brackets indicate trade names). Stylus tip size: 2.5 μm × 2.5 μm High-pass filter: 80 μm Measurement length: 0.64 mm

The method for manufacturing a magnetic disk substrate of the present invention has a polishing step using the method for reducing fine protrusions of the present invention, and the polishing step is performed after the second step among a plurality of polishing steps. Is preferable, and it is particularly preferable to carry out the final polishing step. For example, a Ni-P-plated aluminum alloy substrate having a surface roughness (Ra) of 0.5 nm to 1.5 nm obtained by the one-step or two-step polishing step is subjected to the polishing step using the method for reducing fine protrusions of the present invention. By polishing with, a magnetic disk substrate having a surface roughness (Ra) of 0.3 nm or less, preferably a magnetic disk substrate having a surface roughness (Ra) of 0.25 nm or less can be manufactured. In particular, the method of reducing fine protrusions of the present invention uses a magnetic disk substrate having a surface roughness (Ra) of 0.3 nm or less by polishing in two steps, and preferably a magnetic disk having a surface roughness (Ra) of 0.25 nm or less. It is suitable for use in the second step in manufacturing a substrate.

The manufactured magnetic disk substrate has very few fine protrusions and is excellent in surface smoothness. As the surface smoothness, a surface roughness (Ra) of 0.3 nm or less, preferably 0.25 nm or less is desirable.

As described above, by using the method for reducing fine projections of the present invention, the fine projections can be efficiently removed, the polishing rate can be further improved, and the number of surface defects such as scratches and pits can be reduced. It is possible to manufacture a high-quality magnetic disk substrate having excellent surface properties with improved smoothness such as surface roughness (Ra) and waviness (Wa) with high production efficiency.

Although the method for reducing fine projections of the present invention is particularly effective in the boring process, it can be similarly applied to other polishing processes such as lapping process.

[0042]

Example (Substance to be polished) As a substrate to be polished, a substrate plated with Ni-P was rough-polished in advance with a polishing liquid containing an alumina polishing material to have a substrate surface roughness of 1 nm and a thickness of 0.
Polishing evaluation was performed using an aluminum alloy substrate having a diameter of 95 mm and a diameter of 8 mm.

Examples 1 to 7 and Comparative Examples 1 to 3 Colloidal silica having an average particle size of primary particles as shown in Table 1, 35% hydrogen peroxide (manufactured by Asahi Denka Co., Ltd.), 1-hydroxyethylidene-1,1. -Diphosphonic acid (HEDP, manufactured by Solusia Japan KK, pK1 is 1 or less) or ethylenediaminetetraacetic acid iron salt (EDTA-Fe) was prepared in a predetermined amount and the rest was water so that the total amount was 100% by weight. The order of mixing is HEDP or EDTA-Fe.
Hydrogen peroxide was mixed with an aqueous solution diluted with water, and finally the colloidal silica slurry was quickly added while stirring so as not to gel, and the pH was adjusted to a predetermined value to prepare a polishing composition. The obtained polishing liquid composition was used to polish an object to be polished under the following polishing conditions, and the polishing rate, the surface roughness (Ra) and the number of fine projections were measured and evaluated based on the following methods. The results obtained are shown in Table 1.

(Polishing conditions) Polishing tester: "Double-sided 9B polishing machine" manufactured by Speedfam Polishing pad: Kanebo "Belatrix N0058" Plate rotation speed: 35r / min Slurry supply rate: 40 ml / min Polishing time: 4 minutes Polishing load: 7.8 kPa Number of substrates loaded: 10

(Polishing speed) The specific gravity (8.4 g / cm ³ ) is applied to the weight difference (g) of the substrate before and after the polishing test, and the result is divided by the surface area (65.97 cm ² ) of the disk and the polishing time to give a unit time per unit time. The amount of double-sided polishing is calculated.

(Surface Roughness (Ra)) ScanRate was performed using an atomic force microscope (“Nanoscope III” manufactured by Digital Instrument Co., Ltd.) at a total of 6 points at 120 ° intervals on both sides of the substrate to be polished. Was measured at 1.0 Hz in the range of 2 μm × 2 μm, and the average value was taken. Ra indicates the center line average roughness.

(Number of minute projections) 1 on the front and back of the substrate to be polished
Using an atomic force microscope (“Nanoscope III” manufactured by Digital Instruments Co., Ltd.), a total of 6 points with 3 points at every 20 °, ScanRate at 1.0 Hz, and microprojections included in a range of 2 μm × 2 μm (high The average value per substrate (length: 1 to 30 nm, width: 1 to 100 nm) was obtained.

[0048]

[Table 1]

From the results shown in Table 1, it can be seen that in Examples 1 to 7, substrates having no fine protrusions and low surface roughness can be obtained at high speed, as compared with Comparative Examples 1 to 3.

[0050]

The method of reducing fine projections according to the present invention enables high-speed polishing and highly accurate surface quality, particularly atomic force microscopy (AF).
It is possible to manufacture a substrate capable of preventing the generation of minute protrusions in the surface shape analysis using M).

Claims (6)

[Claims] 1. Containing water, an abrasive, and an acid compound,
An object to be detected by surface analysis using an atomic force microscope (AFM), which has a step of polishing a substrate to be polished with a polishing liquid composition having an acidic pH and an abrasive concentration of less than 10% by weight. A method for reducing minute protrusions on a polishing substrate. 2. The method according to claim 1, wherein the polishing composition further comprises an oxidizing agent. 3. The method according to claim 1, wherein the abrasive is silica. 4. The method of claim 2 wherein the oxidant is hydrogen peroxide. 5. A magnetic disk substrate obtained by using the method according to claim 1. 6. A method for manufacturing a magnetic disk substrate in which minute protrusions detected by surface analysis using an atomic force microscope (AFM) are reduced by using the method according to any one of claims 1 to 4.