JP7186568B2 - Polishing composition, method for polishing substrate, and method for producing substrate - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polishing composition, a substrate polishing method, and a substrate manufacturing method.

BACKGROUND ART Conventionally, the surfaces of materials such as metals, semi-metals, non-metals and their oxides have been subjected to polishing using a polishing composition containing abrasive grains and water. For example, Japanese Patent Laid-Open No. 2002-100003 is cited as a technical document relating to a polishing liquid composition used for polishing a magnetic disk substrate.

JP 2018-81733 A

In the manufacturing process of polished products that require a highly precise surface, generally before the final polishing process (finish polishing process) performed to finish the final product with surface precision, polishing efficiency (typically polishing rate) Polishing (preliminary polishing) is performed with a greater emphasis on It is not preferable for the abrasive grains contained in the polishing composition used in the preliminary polishing step to remain on the object to be polished after the preliminary polishing step, because it can cause deterioration of the surface quality after the final polishing step.

Accordingly, the present invention provides a polishing composition that is used in a preliminary polishing step, and that achieves a polishing rate suitable for preliminary polishing while suppressing the residual of abrasive grains on the object to be polished. intended to Another related object is to provide a method for polishing a substrate and a method for manufacturing a substrate using the polishing composition.

According to this specification, a polishing composition for use in a preliminary polishing step is provided. This polishing composition contains abrasive grains containing silica particles and water. The abrasive grains have an average aspect ratio of 1.1 or more and a cumulative frequency 99% particle size (D ₉₉ ) of less than 295 nm as determined by a light transmission centrifugal sedimentation method. According to the polishing composition containing abrasive grains satisfying the above properties (average aspect ratio and D ₉₉ ), it is possible to achieve a polishing rate suitable for preliminary polishing while suppressing residual abrasive grains on the surface of the object to be polished. can.

In a preferred embodiment of the technology disclosed herein (including polishing compositions, substrate polishing methods, and substrate manufacturing methods; the same shall apply hereinafter), a cumulative frequency of 50% of the abrasive grains by a light transmission centrifugal sedimentation method The particle diameter ( _D50 ) is 80 nm or more. Abrasive grains having a _D50 that satisfies the above range tend to achieve a polishing rate suitable for the preliminary polishing step.

In a preferred aspect of the technology disclosed herein, the polishing composition further contains an acid and an oxidizing agent. By using a polishing composition containing a combination of abrasive grains, an acid, and an oxidizing agent that satisfy the above properties, it becomes easier to achieve a practical polishing rate suitable for preliminary polishing.

A magnetic disk substrate is exemplified as a preferable application target of the technology disclosed herein. A particularly preferable object to be polished is a magnetic disk substrate plated with nickel phosphorous (hereinafter also referred to as “Ni—P substrate”). By applying the polishing composition to the preliminary polishing step of the magnetic disk substrate, it is possible to more effectively reduce residual particles while satisfying a practical polishing rate.

The present invention also provides a method of polishing a substrate. The polishing method comprises a step (1) of supplying any one of the polishing compositions disclosed herein to a substrate to be polished to polish the substrate, and after the step (1), the substrate to be polished and a step (2) of washing. According to this polishing method, it is possible to effectively remove abrasive grains and reduce residual particles in step (2) while satisfying a practical polishing rate in step (1). In a preferred embodiment, the method for polishing a substrate further includes a step (3) of supplying a final polishing composition to the substrate to be polished to polish the substrate after the step (2). According to this aspect, the reduced residual particles from step (1) at the start of step (3) result in a substrate of higher surface quality (e.g., fewer surface defects) in step (3). can get.

Also according to the present invention, a method of manufacturing a substrate is provided. The manufacturing method comprises a step (1) of polishing a substrate to be polished using any of the polishing compositions disclosed herein, and a step (2) of washing the substrate to be polished after step (1). ) and According to this manufacturing method, a substrate having a high surface quality can be manufactured with good productivity.

1 shows particle size distributions of samples 1 and 2 obtained by a light transmission centrifugal sedimentation method. It is the particle size distribution of samples 1 and 2 obtained by a laser scattering method. It is the particle size distribution of samples 1 and 2 obtained by the dynamic light scattering method. 4 is an SEM image of the substrate surface after cleaning in Example 4. FIG. 10 is an SEM image of the substrate surface after cleaning in Example 9. FIG.

Preferred embodiments of the present invention are described below. Matters other than those specifically mentioned in this specification, which are necessary for carrying out the present invention, can be grasped as design matters by those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field.

<Polishing composition>
The polishing composition disclosed herein is used in the preliminary polishing step. In this specification, the term “preliminary polishing step” refers to a polishing step arranged upstream of the final polishing step among polishing steps performed using a polishing composition containing abrasive grains. The term “finish polishing step” refers to a polishing step arranged last (that is, most downstream) among polishing steps performed using a polishing composition containing abrasive grains. Therefore, the polishing composition disclosed herein can be grasped as a type of polishing composition used in polishing steps other than the polishing step arranged on the most downstream side.

(Characteristic)
The polishing composition disclosed herein contains abrasive grains, and is characterized by satisfying an average aspect ratio of 1.1 or more and a cumulative frequency of 99% particle diameter (D ₉₉ ) of less than 295 nm.
Upon detailed observation of the surface of the object to be polished after cleaning after the preliminary polishing step, the inventors found that residual particles were stuck in the concave portions of the roughness of the surface of the object to be polished. However, if an attempt is made to prevent particles from remaining by simply reducing the roughness of the surface after the preliminary polishing process, the polishing rate in the preliminary polishing process tends to decrease. According to the polishing composition disclosed herein, by focusing on and limiting the cumulative frequency 99% particle diameter (D ₉₉ ) of the abrasive grains, the generation of nano-scratches where particles are particularly likely to get stuck is focused. and effectively reduce residual particles. Further, since the average aspect ratio of the abrasive grains is 1.1 or more, a polishing rate suitable for the preliminary polishing process can be realized even if _D99 is limited to less than 295 nm. A person skilled in the art can obtain a polishing composition containing abrasive grains satisfying a predetermined average aspect ratio and _D99 by selecting materials to be used and adjusting the particle size distribution. The above particle size distribution is adjusted, for example, by performing a treatment to remove coarse particles, or by blending two or more types of abrasive grains having different average aspect ratios and/or _D99 at an appropriate ratio. can be done.

The term “cumulative frequency 99% particle size (D ₉₉ )” as used herein refers to a weight-based particle size distribution obtained by particle size measurement based on a light transmission centrifugal sedimentation method. It refers to the particle diameter corresponding to the 99% point. The light transmission type centrifugal sedimentation method uses the sedimentation speed difference caused by the difference in particle size, and measures the particle size while classifying each particle in the abrasive grains. method (for example, laser scattering method, dynamic light scattering method, etc.). Therefore, _D99 , which is based on the particle size distribution obtained by the light transmission centrifugal sedimentation method, can be a highly reliable index for evaluating abrasive grains capable of reducing residual particles.
The particle size distribution obtained by the light transmission centrifugal sedimentation method is obtained by a method conforming to JIS Z 8823-2:2016. A specific procedure for such particle size distribution measurement is as follows. First, a disk-shaped cell is filled with a transparent test liquid containing no particles (eg, an aqueous solution of 8 to 24% by weight of sucrose), and the cell is irradiated with a light beam that passes through the test liquid. Then, while rotating the cell at a predetermined number of revolutions (for example, 24000 rpm), the dispersion liquid of the abrasive grains is injected into the cell from the injection port coaxial with the rotation axis. This causes the particles in the dispersion to settle outward in the centrifugal direction, and the light beam is attenuated by the settling particles. Then, the particle size distribution of the abrasive grains is obtained based on the change in the attenuation of the light beam with the lapse of time. The particle size distribution of the abrasive grains can be determined using software for converting the change in attenuation of the light beam into a particle size distribution.

The _D99 of the abrasive grains obtained by the transmissive centrifugal sedimentation method may be about 290 nm or less, 285 nm or less, 280 nm or less, or 275 nm or less. The smaller the _D99 of the abrasive grain, the more effectively the residual particles tend to be reduced. In addition, the D ₉₉ of the abrasive grain may be about 150 nm or more, 170 nm or more, 190 nm or more, 200 nm or more, or 220 nm or more, It may be 240 nm or more. The polishing rate tends to improve as the _D99 of the abrasive grains increases.

In addition, although not particularly limited, the cumulative frequency 50% particle diameter (D ₅₀ ) of the abrasive grains is preferably 50 nm or more, more preferably 60 nm or more, further preferably 70 nm or more, and 80 nm or more. is particularly preferred. This makes it easier to achieve a polishing rate suitable for the preliminary polishing step. In addition, from the viewpoint of surface quality, the _D50 of the abrasive grain may be 150 nm or less, 140 nm or less, 130 nm or less, 120 nm or less, or 110 nm or less. may be For example, from the viewpoint of achieving both a polishing rate and surface quality, the technology disclosed herein uses an abrasive grain having a D ₅₀ of 50 nm or more and 150 nm or less (more preferably 70 nm or more and 130 nm or less, further preferably 80 nm or more and 110 nm or less). It can be preferably implemented in a mode using. In addition, the above-mentioned "cumulative frequency 50% particle size (D ₅₀ )" means that in the weight-based particle size distribution obtained by particle size measurement based on the light transmission centrifugal sedimentation method, the accumulation from the small particle size side is 50%. It refers to the particle diameter corresponding to the point where

Moreover, the "average aspect ratio" in this specification is measured, for example, by the following method. Specifically, using a scanning electron microscope (SEM), the abrasive grains to be measured (may be one type of abrasive grains, or a mixture of two or more types of abrasive grains ) are observed in an SEM image containing 50 or more particles in one field of view. Observation magnification is 10,000 to 50,000 times. For the abrasive grains in the observed image, draw the smallest rectangle that circumscribes each grain image. Then, regarding the rectangle drawn for each particle image, the value obtained by dividing the length of the long side (value of the major axis) by the length of the short side (value of the minor axis) is the ratio of the major axis to the minor axis (aspect ratio ). The average aspect ratio can be obtained by arithmetically averaging the aspect ratios of the predetermined number of particles. The average aspect ratio can be determined using general image analysis software.
The predetermined number, that is, the number of particles for calculating the aspect ratio of each particle, is usually 1000 or more, preferably 1500 or more, from the viewpoint of improving measurement accuracy and reproducibility. preferable. The upper limit of the predetermined number is not particularly limited. From the viewpoint of measurement efficiency, the predetermined number may be, for example, 5000 or less, or 2500 or less.

The average aspect ratio may be approximately 1.11 or more, 1.12 or more, 1.13 or more, 1.14 or more, or 1.15. or more. A practical polishing rate tends to be obtained more easily as the average aspect ratio increases. Further, the average aspect ratio of the abrasive grains may be approximately 3.0 or less, 2.5 or less, 2.0 or less, or 1.5 or less. , 1.2 or less. In addition, the shape of each particle constituting the abrasive grains is not particularly limited as long as the average aspect ratio of the entire abrasive grains satisfies the above-mentioned predetermined range, and depending on the purpose of use, mode of use, etc. of the polishing composition can be selected as appropriate. That is, the abrasive grains disclosed herein may contain spherical particles. Examples of specific shapes of particles (non-spherical particles) having an aspect ratio of 1.1 or more include peanut shape (that is, peanut shell shape), cocoon shape, shape with projections (for example, confetti shape), A rugby ball shape and the like can be mentioned.

(abrasive)
The abrasive grains of the polishing composition disclosed herein contain silica particles. Silica particles can be various silica particles containing silica as a main component. Here, silica particles containing silica as a main component refer to particles in which 90% by weight or more (usually 95% by weight or more, typically 98% by weight or more) of the particles are silica. Examples of silica particles that can be used include, but are not limited to, colloidal silica, precipitated silica, sodium silicate silica, alkoxide silica, fumed silica, dry silica, detonation silica, and the like. Examples of silica particles that can be used further include silica particles (i.e., colloidal silica, precipitated silica, sodium silicate silica, alkoxide silica, fumed silica, dry silica, explosive silica, etc.) obtained as raw materials. and silica particles. Examples of such silica particles include the silica particles of the raw material (hereinafter also referred to as "raw material silica"), heat treatment such as heating, drying, and firing, pressure treatment such as autoclave treatment, crushing and pulverization ( mechanical treatment such as crushing), surface modification (for example, introduction of functional groups, chemical modification such as metal modification), etc. Contains silica particles obtained by applying one or more treatments selected from obtain. The abrasive grains disclosed herein may contain one type of silica particles as described above alone or in combination of two or more types.

Silica particles include, for example, silica particles obtained by subjecting raw material silica to heat treatment (hereinafter also referred to as "heat-treated silica"), specifically heated silica particles, dried silica particles, and calcined silica particles. silica particles and the like. Here, the heated silica particles are typically obtained through a process of holding in an environment of 60° C. or more and less than 110° C. for a certain time or more (for example, 15 minutes or more, typically 30 minutes or more). It refers to silica particles obtained by In addition, the dried silica particles are typically dried in an environment of 110° C. or more and less than 500° C. (preferably 300° C. or more and less than 500° C.) for a certain period of time or more (for example, 15 minutes or more, typically 30 minutes). Above) Refers to silica particles obtained through a holding treatment. Then, the calcined silica particles (hereinafter also referred to as "calcined silica") are typically kept in an environment of 500 ° C. or higher for a certain period of time (for example, 15 minutes or longer, typically 30 minutes or longer). It refers to silica particles obtained through a treatment (hereinafter also referred to as “firing”). Silica particles obtained through a process of heat-treating any of the above raw material silica (colloidal silica, precipitated silica, sodium silicate silica, alkoxide silica, fumed silica, dry silica, explosive silica, etc.) This is a typical example included in the concept of heat-treated silica. When the silica abrasive grains contain heat-treated silica, the silica abrasive grains may contain one type of heat-treated silica, or two or more types having different manufacturing conditions and/or physical properties. In addition, the silica abrasive grains may be composed of one or more types of heat-treated silica, and include a combination of heat-treated silica and other silica particles (i.e., silica particles that have not been heat-treated). There may be.

Colloidal silica is another preferred example of silica particles that can be used as a component of silica abrasive grains in the technique disclosed herein. Among them, it is preferable to use colloidal silica synthesized through particle growth in an aqueous phase, such as sodium silicate method silica and alkoxide method silica. Silica abrasive grains containing this kind of colloidal silica can suitably achieve a high polishing rate and good surface accuracy. When the silica abrasive grains disclosed herein contain colloidal silica, the colloidal silica contained in the silica abrasive grains may be one type, or two or more types having different manufacturing conditions and/or physical properties. . In addition, the silica abrasive grains may be composed of one or more colloidal silica, and may be composed of a combination of colloidal silica and other silica particles (i.e., silica particles other than colloidal silica). There may be.

In the polishing composition disclosed herein, the content of silica particles in the solid content contained in the polishing composition is not particularly limited. The content of the silica particles is preferably 40% by weight or more, more preferably 50% by weight or more, and still more preferably 60% by weight or more of the total solid content, from the viewpoint of easily exhibiting the effects of the present invention. (for example, 80% by weight or more). Alternatively, from the viewpoint of making it easier to balance various performances (for example, polishing rate, surface quality of the surface to be polished, etc.), the content of the silica particles is 90% by weight or less (for example, 80% by weight or less) of the total solid content. may be In the present specification, the solid content contained in the polishing composition refers to the residual content (non-volatile content) after water is evaporated from the polishing composition at a temperature (for example, 60 ° C.) at which bound water is not removed. Say.

In addition, the abrasive grains of the polishing composition disclosed herein can contain particles other than the silica particles. Any of inorganic particles, organic particles, and organic-inorganic composite particles can be used as particles other than silica particles. Specific examples of inorganic particles include oxide particles such as alumina particles, cerium oxide particles, chromium oxide particles, titanium dioxide particles, zirconium oxide particles, magnesium oxide particles, manganese dioxide particles, zinc oxide particles, and red iron oxide particles; silicon nitride particles , nitride particles such as boron nitride particles; carbide particles such as silicon carbide particles and boron carbide particles; diamond particles; carbonates such as calcium carbonate and barium carbonate; Examples of the alumina particles include α-alumina, intermediate alumina other than α-alumina, and composites thereof. Intermediate alumina is a general term for alumina particles other than α-alumina, and specific examples thereof include γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina and composites thereof. Specific examples of organic particles include polymethyl methacrylate (PMMA) particles and poly(meth)acrylic acid particles (here, (meth)acrylic acid is a generic term for acrylic acid and methacrylic acid.) , polyacrylonitrile particles, and the like. These particles other than silica particles can be used singly or in combination of two or more.

The polishing composition disclosed herein can preferably be implemented in a manner substantially free of alumina abrasive grains (eg, α-alumina abrasive grains). According to such a polishing composition, quality deterioration due to the use of alumina abrasive grains (for example, the occurrence of roughness (scratches) and dents, an increase in residual particles due to the occurrence of the roughness, defects due to sticking of abrasive grains, etc.) prevented. In the present specification, substantially not containing a predetermined abrasive grain (for example, alumina abrasive grain) means that the proportion of the abrasive grain in the total solid content contained in the polishing composition is 1% by weight or less (more preferably 0.5% by weight or less, typically 0.1% by weight or less). A polishing composition having a proportion of alumina abrasive grains of 0% by weight, ie a polishing composition containing no alumina abrasive grains, is particularly preferred. In addition, the polishing composition disclosed herein can be preferably implemented in a manner substantially free of α-alumina abrasive grains.

The polishing composition disclosed herein can also preferably be practiced in a mode in which it does not substantially contain particles other than silica particles (non-silica particles). Here, "substantially free of non-silica particles" means that the proportion of non-silica particles in the total amount of solids contained in the polishing composition is 1% by weight or less (more preferably 0.5% by weight or less, typically 0.1% by weight or less). In such an aspect, the application effects of the technology disclosed herein can be favorably exhibited.

(water)
The polishing composition disclosed herein typically contains, in addition to the abrasive grains described above, water for dispersing the abrasive grains. As water, ion-exchanged water (deionized water), pure water, ultrapure water, distilled water, or the like can be preferably used.

The polishing composition disclosed herein (typically a slurry composition) can be preferably implemented in a form having a solid content of, for example, 5 g/L to 300 g/L. A form in which the solid content is 10 g/L to 200 g/L is more preferable.

(acid)
The polishing composition disclosed herein may preferably be implemented in a mode containing an acid as a polishing accelerator. Examples of acids that can be preferably used include inorganic acids and organic acids (eg, organic carboxylic acids having about 1 to 10 carbon atoms, organic phosphonic acids, organic sulfonic acids, amino acids, etc.). Not limited. An acid can be used individually by 1 type or in combination of 2 or more types.

Specific examples of inorganic acids include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, hypophosphorous acid, phosphonic acid, boric acid, sulfamic acid and the like.

Specific examples of organic acids include citric acid, maleic acid, malic acid, glycolic acid, succinic acid, itaconic acid, malonic acid, iminodiacetic acid, gluconic acid, lactic acid, mandelic acid, tartaric acid, crotonic acid, nicotinic acid, and acetic acid. , adipic acid, formic acid, oxalic acid, propionic acid, valeric acid, caproic acid, caprylic acid, capric acid, cyclohexanecarboxylic acid, phenylacetic acid, benzoic acid, crotonic acid, methacrylic acid, glutaric acid, fumaric acid, phthalic acid, isophthalic acid Acid, terephthalic acid, glycolic acid, tartronic acid, glyceric acid, hydroxybutyric acid, hydroxyacetic acid, hydroxybenzoic acid, salicylic acid, isocitric acid, methylenesuccinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetic acid, glycine, alanine, glutamic acid , aspartic acid, valine, leucine, isoleucine, serine, threonine, cysteine, methionine, phenylalanine, tryptophan, tyrosine, proline, cystine, glutamine, asparagine, lysine, arginine, picolinic acid, methyl acid phosphate, ethyl acid phosphate, ethyl glycol acid phosphate, isopropyl acid phosphate, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetra(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1- diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethanehydroxy-1,1,2-triphosphonic acid, ethane-1,2-dicarboxy-1, 2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid, α-methylphosphonosuccinic acid, aminopoly(methylenephosphonic acid), methane Sulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, 2-naphthalenesulfonic acid and the like.

Preferred acids from the viewpoint of polishing efficiency include nitric acid, sulfuric acid, phosphoric acid, sulfamic acid, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, methanesulfonic acid and the like. Among them, nitric acid, sulfuric acid, phosphoric acid, sulfamic acid and methanesulfonic acid are preferred.

When the polishing composition contains an acid, its content is not particularly limited, but is usually 0.01 mol/L or more, preferably 0.05 mol/L or more, and more preferably 0.1 mol/L or more. preferable. If the acid content is too low, the polishing rate tends to be insufficient, which may not be practical. Also, the upper limit of the acid content is usually appropriately 1 mol/L or less, preferably 0.7 mol/L or less, and more preferably 0.6 mol/L or less (for example, 0.5 mol/L or less). If the acid content is too high, the surface accuracy of the object to be polished tends to decrease, which may be undesirable in practice.

Acids may be used in the form of their salts. Examples of salts include metal salts (e.g., alkali metal salts such as lithium salts, sodium salts, and potassium salts) and ammonium salts (e.g., tetramethylammonium salts, tetraethylammonium salts, etc.) of the inorganic acids and organic acids described above. quaternary ammonium salts), alkanolamine salts (eg, monoethanolamine salts, diethanolamine salts, triethanolamine salts), and the like.
Specific examples of salts include alkali metal phosphates such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, and sodium dihydrogen phosphate, and alkali metal Hydrogen phosphate; alkali metal salts of organic acids exemplified above; other alkali metal salts of glutamic acid diacetic acid, alkali metal salts of diethylenetriamine pentaacetic acid, alkali metal salts of hydroxyethylethylenediamine triacetic acid, triethylenetetramine hexaacetic acid alkali metal salt; and the like. Alkali metals in these alkali metal salts can be, for example, lithium, sodium, potassium and the like.

Salts of inorganic acids (for example, alkali metal salts and ammonium salts) can be preferably employed as salts that can be contained in the polishing composition disclosed herein. For example, potassium chloride, sodium chloride, ammonium chloride, potassium nitrate, sodium nitrate, ammonium nitrate, potassium phosphate and the like can be preferably used.

(Oxidant)
The polishing composition disclosed herein may optionally contain an oxidizing agent. Examples of oxidizing agents include peroxides, nitric acid or its salts, periodic acid or its salts, peroxoacids or its salts, permanganic acid or its salts, chromic acid or its salts, oxyacids or its salts, metal salts. , sulfuric acid and the like, but are not limited to these. The oxidizing agents can be used singly or in combination of two or more. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitric acid, iron nitrate, aluminum nitrate, ammonium nitrate, peroxomonosulfuric acid, ammonium peroxomonosulfate, metal peroxomonosulfate, peroxodisulfuric acid, peroxodi Ammonium sulfate, metal peroxodisulfate, peroxolinic acid, peroxosulfuric acid, sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromous acid, hypoiodic acid, chloric acid, bromic acid, Iodic acid, periodic acid, perchloric acid, hypochlorous acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, chromate metal salt, dichromate metal salt, iron chloride, iron sulfate, Examples include iron citrate and iron ammonium sulfate. Preferred oxidants are hydrogen peroxide, iron nitrate, periodic acid, peroxomonosulfuric acid, peroxodisulfuric acid and nitric acid. The oxidizing agent preferably contains at least hydrogen peroxide, and more preferably consists of hydrogen peroxide.

When the polishing composition contains an oxidizing agent, its content is not particularly limited, but it is usually preferably 0.05 mol/L or more, more preferably 0.1 mol/L or more, and still more preferably 0.1 mol/L or more. It is 15 mol/L or more. If the content of the oxidizing agent is too low, the speed at which the object to be polished is oxidized becomes slow and the polishing rate decreases, which may not be practically preferable. Also, the upper limit of the content of the oxidizing agent is preferably 1 mol/L or less, more preferably 0.9 mol/L or less, and still more preferably 0.8 mol/L or less. If the content of the oxidizing agent is too high, the surface accuracy of the object to be polished tends to decrease, which may not be practically preferable.

(basic compound)
The polishing composition may contain a basic compound, if necessary. Here, the basic compound refers to a compound that has the function of increasing the pH of the polishing composition when added to the composition. Examples of basic compounds include alkali metal hydroxides, carbonates and hydrogen carbonates, quaternary ammonium or salts thereof, ammonia, amines, phosphates and hydrogen phosphates, organic acid salts and the like. A basic compound can be used individually by 1 type or in combination of 2 or more types.

Specific examples of alkali metal hydroxides include potassium hydroxide and sodium hydroxide.
Specific examples of carbonates and hydrogencarbonates include ammonium hydrogencarbonate, ammonium carbonate, potassium hydrogencarbonate, potassium carbonate, sodium hydrogencarbonate and sodium carbonate.
Specific examples of quaternary ammonium or salts thereof include quaternary ammonium hydroxides such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrabutylammonium hydroxide; alkali metals of such quaternary ammonium hydroxides; salts (eg, sodium salts, potassium salts); and the like.
Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N-(β-aminoethyl)ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, and anhydrous piperazine. , piperazine hexahydrate, 1-(2-aminoethyl)piperazine, N-methylpiperazine, guanidine, azoles such as imidazole and triazole, and the like.
Specific examples of phosphates and hydrogen phosphates include alkalis such as tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate and sodium dihydrogen phosphate. metal salts.
Specific examples of organic acid salts include potassium citrate, potassium oxalate, potassium tartrate, potassium sodium tartrate, and ammonium tartrate.

(other ingredients)
The polishing composition disclosed herein contains surfactants, water-soluble polymers, dispersants, chelating agents, preservatives, antifungal agents, etc., as long as the effects of the present invention are not significantly hindered. Known additives that can be used in products (for example, polishing compositions for magnetic disk substrates such as Ni—P substrates) may be further contained as necessary.

The surfactant is not particularly limited, and any of anionic surfactants, nonionic surfactants, cationic surfactants and amphoteric surfactants can be used. Use of a surfactant (typically a water-soluble organic compound with a molecular weight of less than 1×10 ⁴ ) can improve the dispersion stability of the polishing composition. Surfactant can be used individually by 1 type or in combination of 2 or more types.
Specific examples of anionic surfactants include polyoxyethylene alkyl ether acetic acid, polyoxyethylene alkyl sulfate, alkyl sulfate, polyoxyethylene alkyl sulfate, alkyl sulfate, alkylbenzenesulfonic acid, alkyl phosphate, and polyoxyethylene. Alkyl phosphate, polyoxyethylene sulfosuccinic acid, alkyl sulfosuccinic acid, alkyl naphthalene sulfonic acid, alkyl diphenyl ether disulfonic acid, polyacrylic acid, sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkylphenyl ether sulfate, sodium polyoxyethylene alkylphenyl ether sulfate, and salts thereof;
Other specific examples of anionic surfactants include polyalkylarylsulfonic acid compounds such as naphthalenesulfonic acid-formaldehyde condensates, methylnaphthalenesulfonic acid-formaldehyde condensates, anthracene-sulfonic acid-formaldehyde condensates, and benzenesulfonic acid-formaldehyde condensates. melamine formalin resin sulfonic acid compounds such as melamine sulfonic acid formaldehyde condensates; lignin sulfonic acid compounds such as lignin sulfonic acid and modified lignin sulfonic acid; aromatic amino sulfonic acids such as aminoaryl sulfonic acid-phenol-formaldehyde condensates polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallylsulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonic acid; and salts thereof. The salt is preferably an alkali metal salt such as sodium salt or potassium salt.
Specific examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, glycerin fatty acid esters, polyoxyethylene fatty acid esters, polyoxyethylene alkylamines, alkylalkanolamides, and the like. .
Specific examples of cationic surfactants include alkyltrimethylammonium salts, alkyldimethylammonium salts, alkylbenzyldimethylammonium salts, alkylamine salts and the like.
Specific examples of amphoteric surfactants include alkylbetaines and alkylamine oxides.

In the polishing composition containing a surfactant, it is suitable that the content of the surfactant is, for example, 0.005 g/L or more. The above content is preferably 0.01 g/L or more, more preferably 0.1 g/L or more, from the viewpoint of surface smoothness after polishing. From the viewpoint of polishing rate and the like, the content is suitably 100 g/L or less, preferably 50 g/L or less, for example 10 g/L or less.

The polishing composition disclosed herein may contain a water-soluble polymer. By containing a water-soluble polymer, surface accuracy after polishing can be improved. Examples of water-soluble polymers include polyalkylarylsulfonic acid compounds such as naphthalenesulfonic acid formaldehyde condensates, methylnaphthalenesulfonic acid formaldehyde condensates, and anthracene sulfonic acid formaldehyde; melamine formalin resin sulfones such as melamine sulfonic acid formaldehyde condensates; Acid-based compounds; ligninsulfonic acid-based compounds such as ligninsulfonic acid and modified ligninsulfonic acid; aromatic aminosulfonic acid-based compounds such as aminoarylsulfonic acid-phenol-formaldehyde condensates; , polyallylsulfonic acid, polyisoamylenesulfonic acid, polystyrenesulfonate, polyacrylate, polyvinyl acetate, polymaleic acid, polyitaconic acid, polyvinyl alcohol, polyglycerin, polyvinylpyrrolidone, isoprenesulfonic acid and acrylic acid Polymer, polyvinylpyrrolidone polyacrylic acid copolymer, polyvinylpyrrolidone vinyl acetate copolymer, diallylamine hydrochloride sulfur dioxide copolymer, carboxymethylcellulose, salt of carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, pullulan, chitosan, chitosan salts etc. A water-soluble polymer can be used individually by 1 type or in combination of 2 or more types.

In the polishing composition of the embodiment containing a water-soluble polymer, the content of the water-soluble polymer in the polishing liquid (in the embodiment containing a plurality of water-soluble polymers, their total content) is, for example, 0.01 g /L or more is appropriate. The above content is preferably 0.05 g/L or more, more preferably 0.08 g/L or more, still more preferably 0.08 g/L or more, and still more preferably 0.05 g/L or more, from the viewpoint of surface smoothness of an object to be polished (for example, a magnetic disk substrate) after polishing. 1 g/L or more. From the viewpoint of polishing rate and the like, the content is suitably 10 g/L or less, preferably 5 g/L or less, for example 1 g/L or less. In addition, the technique disclosed here can be preferably practiced even in a mode in which the polishing composition does not substantially contain a water-soluble polymer.

Examples of dispersants include polycarboxylic acid-based dispersants such as polycarboxylic acid sodium salts and polycarboxylic acid ammonium salts; naphthalenesulfonic acid-based dispersants such as naphthalenesulfonic acid sodium salts and naphthalenesulfonic acid ammonium salts; polyphosphate dispersant; polyalkylenepolyamine dispersant; quaternary ammonium dispersant; alkylpolyamine dispersant; alkylene oxide dispersant; polyhydric alcohol ester dispersant;

Examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid-based chelating agents include ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetate, nitrilotriacetic acid, sodium nitrilotriacetate, ammonium nitrilotriacetate, hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetate, diethylenetriaminepentaacetic acid. , sodium diethylenetriaminepentaacetate, triethylenetetraminehexaacetic acid and sodium triethylenetetraminehexaacetate. Examples of organic phosphonic acid chelating agents include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri(methylenephosphonic acid), ethylenediaminetetrakis(methylenephosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, ethane-1-hydroxy-1,1-diphosphonic acid, ethane-1-hydroxy-1,1,2-triphosphonic acid , ethane-1,2-dicarboxy-1,2-diphosphonic acid, methanehydroxyphosphonic acid, 2-phosphonobutane-1,2-dicarboxylic acid, 1-phosphonobutane-2,3,4-tricarboxylic acid and α-methylphosphonic acid. Contains nosuccinic acid. Of these, organic phosphonic acid-based chelating agents are more preferred, and ethylenediaminetetrakis(methylenephosphonic acid) and diethylenetriaminepenta(methylenephosphonic acid) are particularly preferred. A particularly preferred chelating agent is ethylenediaminetetrakis(methylenephosphonic acid).

Examples of antiseptics and antifungal agents include isothiazoline preservatives such as 2-methyl-4-isothiazolin-3-one and 5-chloro-2-methyl-4-isothiazolin-3-one, and paraoxybenzoic acid esters. , phenoxyethanol and the like.

(polishing liquid)
The polishing composition disclosed herein is typically supplied to an object to be polished (for example, a magnetic disk substrate) in the form of a polishing liquid containing the polishing composition, and used for polishing the object to be polished. . The polishing liquid may be prepared, for example, by diluting the polishing composition (typically with water). Alternatively, the polishing composition may be used as a polishing liquid as it is. That is, the concept of the polishing composition in the technology disclosed herein includes a polishing liquid (working slurry) that is supplied to a polishing object and used for polishing the polishing object, and a diluted polishing liquid that is used as a polishing liquid. Both concentrates are included. A polishing composition in the form of such a concentrate is advantageous from the viewpoints of convenience in production, distribution, storage, etc., cost reduction, and the like. The concentration ratio can be, for example, about 1.5 times to 50 times. From the viewpoint of the storage stability of the concentrate, a concentration ratio of about 2 to 20 times (typically 2 to 10 times) is appropriate.

The content of abrasive grains in the polishing liquid (the total content thereof when multiple types of abrasive grains are included) is not particularly limited, but is typically 1% by weight or more, and 2.5% by weight or more. It is preferably 5% by weight or more, more preferably 5% by weight or more. A higher polishing rate tends to be realized by increasing the content of abrasive grains. From the viewpoint of the surface smoothness of the substrate after polishing and the stability of polishing, the content is usually 20% by weight or less, preferably 15% by weight or less, more preferably 10% by weight or less, and even more preferably 10% by weight or less. is 8% by weight or less.

(pH)
The pH of the polishing composition disclosed herein is not particularly limited. The pH of the polishing composition can be, for example, pH 12.0 or less (typically pH 0.5 to 12.0), and pH 10.0 or less (typically pH 0.5 to 10.0). may be In a preferred embodiment, the pH of the polishing composition can be pH 7.0 or less (eg, pH 0.5 to 7.0), and pH 5.0 or less (typically pH 1.0 to 5.0). More preferably, the pH is 4.0 or less (eg, pH 1.0 to 4.0). The pH of the polishing composition is, for example, pH 3.0 or less (typically pH 1.0 to 3.0, preferably pH 1.0 to 2.0, more preferably pH 1.0 to 1.8). can be done. If necessary, a pH adjuster such as an organic acid, an inorganic acid, or a basic compound may be contained in the polishing liquid so that the above pH is achieved. The above pH can be preferably applied to the polishing composition for the pre-polishing step of magnetic disk substrates such as Ni—P substrates, for example.

(Multi-component polishing composition)
In addition, the polishing composition disclosed herein may be of a one-component type, or may be of a multi-component type including a two-component type. For example, liquid A containing some components (typically, components other than water) of the constituent components of the polishing composition and liquid B containing the remaining components are mixed to polish the object to be polished. may be configured to be used for A multi-component polishing composition according to a preferred embodiment comprises liquid A containing abrasive grains (typically, an abrasive dispersion liquid that may contain a dispersant) and components other than abrasive grains (e.g., acid, aqueous It is composed of a liquid B containing a flexible polymer and other additives). Usually, these are stored separately before use and can be mixed during use (during polishing of the substrate to be polished). During mixing, an oxidizing agent such as hydrogen peroxide may be further mixed. For example, when the oxidizing agent (eg, hydrogen peroxide) is supplied in the form of an aqueous solution (eg, hydrogen peroxide solution), the aqueous solution can be Liquid C constituting the multi-component polishing composition.

<Application>
The application target of the technology disclosed herein is not particularly limited. The technology disclosed herein includes polishing of various objects to be polished that can be polished with a polishing composition containing abrasive grains, and production of polished objects including polishing of objects to be polished using the above-described polishing composition. can be applied to Materials to be polished include metals such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, stainless steel, semimetals, alloys thereof, and thin films used for semiconductor wiring using these materials; quartz Glass-like materials such as glass, aluminosilicate glass, and vitreous carbon; Ceramic materials such as alumina, silica, sapphire, silicon nitride, tantalum nitride, and titanium carbide; Compound semiconductor substrate materials such as silicon carbide, gallium nitride, and gallium arsenide; Resin materials such as polycarbonate-based resins, acrylic-based resins, allyl-based resins, urethane-based resins, epithio-based resins, and polyimide resins; and the like, but are not limited to these. Moreover, the object to be polished may be made of a plurality of materials among these materials.

The polishing composition disclosed herein is used for polishing various objects requiring a highly precise surface, such as magnetic disk substrates, semiconductor substrates such as silicon wafers, and optical materials such as lenses and reflecting mirrors. can be preferably used for Such an object to be polished may be a disc substrate having a metal layer or a metal compound layer other than the nickel phosphorous plating layer on the surface of the substrate disc. The substrate disc may be made of, for example, aluminum alloy, glass, vitreous carbon, or the like. The polishing composition disclosed herein is preferably applied to polishing Ni—P substrates among such disk substrates, and is a Ni—P substrate having a nickel phosphorous plating layer on an aluminum alloy base disk. can be preferably applied by polishing.

The polishing composition disclosed herein is used in the pre-polishing step in the process of manufacturing polished objects (for example, magnetic disk substrates) that require a highly precise surface after the final polishing step. As a result, residual abrasive grains after the preliminary polishing process are suppressed, so that a substrate with a higher surface quality can be obtained after the final polishing process. In addition, when a plurality of preliminary polishing steps are performed as the preceding steps of the final polishing step, the same or different polishing compositions can be used in these preliminary polishing steps. At this time, the polishing composition disclosed herein can be used in any pre-polishing step. In the case of having a plurality of pre-polishing steps, the polishing composition disclosed herein is preferably used in a pre-polishing step which is arranged immediately before the final polishing step with a washing step interposed therebetween.

The polishing composition disclosed herein has a surface roughness (arithmetic mean roughness (Ra)) of 20 Å as measured by a laser scanning surface roughness meter “TMS-3000WRC” manufactured by Schmitt Measurement Systems Inc. It is suitable for polishing (typically, primary polishing) a magnetic disk substrate with a thickness of about 300 Å to adjust the surface roughness (arithmetic mean roughness (Ra)) of the magnetic disk substrate to 10 Å or less. For such uses, it is particularly significant to apply the technology disclosed herein.

<Polishing process>
The polishing composition disclosed herein can be suitably used for polishing an object to be polished (for example, a magnetic disk substrate), for example, in a mode including the following operations. A preferred embodiment of a method for polishing an object to be polished (typically a substrate to be polished) using the polishing composition disclosed herein will be described below.
That is, a polishing liquid (working slurry) containing any one of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include performing operations such as concentration adjustment (for example, dilution) and pH adjustment on the polishing composition to prepare the polishing liquid. Alternatively, the polishing composition may be used as a polishing liquid as it is.

Then, the polishing liquid is supplied to the object to be polished, and the object is polished by a conventional method. For example, an object to be polished is set in a general polishing apparatus, and polishing liquid is supplied to the surface of the object to be polished (surface to be polished) through the polishing pad of the polishing apparatus. Typically, while the polishing liquid is continuously supplied, the polishing pad is pressed against the surface of the object to be polished, and the two are relatively moved (for example, rotationally moved). Polishing of the object to be polished is completed through such a polishing process.

A polishing step as described above can be part of the manufacturing process of a substrate (eg, a magnetic disk substrate, typically a Ni—P substrate). Therefore, according to this specification, a substrate manufacturing method and a polishing method including the above-described polishing step are provided.

The polishing composition disclosed herein can be preferably used in a pre-polishing step of an object to be polished. According to this specification, a method for producing a polished object (substrate) comprising a step of performing preliminary polishing using any of the polishing compositions described above, and a step of cleaning the object to be polished after the preliminary polishing step. and a polishing method are provided. The above method comprises a step (1) of supplying the polishing composition disclosed herein to an object to be polished to polish the object, and a step (2) of washing the substrate to be polished after step (1). including. The method may include a final polishing step after step (2) above. Therefore, the matters disclosed by this specification include the step (1) of polishing the object to be polished with a polishing composition containing abrasive grains having an average aspect ratio and _D99 within a predetermined range; A step (2) of removing the polishing composition used in step (2), and a step of polishing the object with a polishing composition (finish polishing composition) different from the polishing composition used in step (1). (3) and (3) are included in this order. The method for producing a polished product can be preferably applied to the production of magnetic disk substrates (eg, Ni—P substrates) and other polished products. In addition, the polishing composition used in the final polishing step is not particularly limited.

Several examples relating to the present invention are described below, but the present invention is not intended to be limited to those shown in such examples.

<Method for measuring particle size distribution>
A plurality of types of silica particles with different particle size distributions were prepared, and two types of abrasive grains were produced by combining these (Samples 1 and 2). Then, each abrasive grain is dispersed in ion-exchanged water to prepare a slurry for measurement. Particle size distribution was measured.
In the light transmission centrifugal sedimentation method, a disc centrifugal particle size distribution analyzer "DC24000 UHR" manufactured by CPS Instruments, USA was used to determine the weight-based particle size distribution according to JIS Z 8823-2. The particle size distribution was measured under the following conditions.
Test solution introduced into the cell: sucrose aqueous solution with a minimum concentration of 8% by weight and a maximum concentration of 24% by weight Injection volume of the test solution introduced into the cell: 12 mL
Silica concentration of slurry for measurement: 2% by weight
Injection amount of slurry for measurement: 0.1 mL
Disc rotation speed: 24000 rpm
Measurement range: 0.025 μm to 1.0 μm
In the laser scattering method, the model "LA-950" manufactured by HORIBA was used to determine the volume-based particle size distribution. Further, in the dynamic light scattering method, the volume-based particle size distribution was determined using a model "Zetasizer nano ZSP" manufactured by Malvern. The particle size distribution obtained by the light transmission centrifugal sedimentation method is shown in FIG. 1, the particle size distribution obtained by the laser scattering method is shown in FIG. 2, and the particle size distribution obtained by the dynamic light scattering method is shown in FIG.

As shown in FIGS. 1 to 3, the particle size distribution obtained by the light transmission centrifugal sedimentation method differs from the particle size distribution obtained by the laser scattering method and the dynamic light scattering method, and the mixed silica particles are mixed. A peak based on each mode diameter was confirmed. It is considered that this is because the particle diameter is measured while classifying each particle contained in the abrasive grain. For this reason, the light transmission centrifugal sedimentation method has better resolution than other methods, and the cumulative frequency 99% particle diameter (D ₉₉ ) obtained by this method is a coarse grain that can form roughness. It can be seen that it can be a highly reliable indicator when examining the presence of particles.

<Examples 1 to 10>
[Preparation of polishing composition]
A plurality of types of silica particles with different particle size distributions and aspect ratios were prepared. Abrasive grains containing these silica particles alone or in combination, phosphoric acid, 31% hydrogen peroxide solution, and deionized water were mixed to give an abrasive grain concentration of 7% by weight and a phosphoric acid concentration of 0.5% by weight. A polishing composition having a concentration of 14 mol/L and a hydrogen peroxide concentration of 0.36 mol/L was prepared (Examples 1 to 10). The pH of this polishing composition was 1.5. For the polishing composition according to each example, Table 1 shows the average aspect ratio of the abrasive grains used, the cumulative frequency 99% particle size (D ₉₉ ), and the cumulative frequency 50% particle size (D ₅₀ ) by the light transmission centrifugal sedimentation method. are shown together.

[Disc polishing]
Using the polishing composition according to each example as it is as a polishing liquid, an object to be polished was polished under the following conditions. A hard disk aluminum substrate having an electroless nickel phosphorous plating layer on its surface was used as the object to be polished. The object to be polished (substrate to be polished) has a diameter of 3.5 inches (doughnut-shaped with an outer diameter of about 95 mm and an inner diameter of about 25 mm), a thickness of 1.75 mm, and a surface roughness Ra (Schmitt Measurement System The arithmetic mean roughness of the nickel phosphorus plating layer measured by a laser scanning surface roughness meter "TMS-3000WRC" manufactured by Inc. was 130 Å.

(polishing conditions)
Polishing device: Double-sided polishing machine manufactured by System Seiko, model "9.5B-5P"
Polishing pad: suede pad (average initial surface line roughness: 10 μm or more, pore size: 50 μm)
Input number of substrates to be polished: 15 (3 substrates/carrier x 5 carriers)
Polishing liquid supply rate: 135 mL/min Polishing load: 120 g/cm ²
Upper surface plate rotation speed: 27 rpm
Lower surface plate rotation speed: 36 rpm
Sun gear (sun gear) speed: 8 rpm
Amount of polishing: Total thickness of both sides of each substrate is about 2.2 μm

[Polishing rate]
The polishing rate on one side of the substrate to be polished was calculated under the above polishing conditions using the polishing composition according to each example. The polishing rate was obtained based on the following formula. Table 1 shows the results. The polishing rate (%) in Table 1 is a relative value with the polishing rate of Example 8 as 100%.
Polishing rate [μm/min]=weight loss of substrate due to polishing [g]/(area of substrate [cm ² ]×density of nickel-phosphorus plating [g/cm ³ ]×polishing time [min])×10 ⁴

[Number of residual particles]
The substrate was polished under the same conditions as for the measurement of the polishing rate, and then washed with a washing machine manufactured by Cresen Co., Ltd., and then the number of particles remaining on the surface of the substrate was measured. Specific procedures are described below.
First, the substrate was washed in running water without using a brush and detergent, water droplets adhering to the substrate were shaken off with a spin dryer, dried, and then normal cleaning using a brush and detergent was performed within 10 minutes. did Specific washing conditions are as follows.
(No brush condition)
Cleaning agent application time: 0 seconds 1st cleaning time (running water only): 15 seconds 2nd cleaning time (running water only): 20 seconds Ultrasonic cleaning time (running water only): 20 seconds Spin dry drying time: 20 seconds (normal conditions) )
Cleaning agent application time: 5 seconds 1st cleaning time (with brush cleaning): 15 seconds 2nd cleaning time (with brush cleaning): 20 seconds Ultrasonic cleaning time (running water only): 20 seconds Spin dry drying time: 20 seconds Next Then, using a scanning electron microscope "SU8000" manufactured by Hitachi High-Technologies Corporation, the surface of the substrate (both sides) after washing was observed at a magnification of 50,000 times with 10 fields per side. Then, using image analysis type particle size distribution measurement software "Mac-View" manufactured by Mountec, the number of residual particles in each field of view was measured, and the average value of the number of residual particles per field of view was calculated. Table 1 shows the results. The number of residual particles (%) in Table 1 is a relative value with the number of residual particles in Example 8 as 100%. 4 shows an SEM image of the substrate surface after cleaning in Example 4, and an SEM image of the substrate surface after cleaning in Example 9 is shown in FIG.

As shown in Table 1, in Examples 1 to 7, compared with Examples 8 and 9, the number of residual particles was reduced. For example, as shown in FIGS. 4 and 5, in Example 9, roughness was formed on the substrate surface and many particles remained, whereas in Example 4, formation of roughness was suppressed and residual particles were reduced. rice field. Further, as shown in Table 1, in Examples 1 to 7, significantly higher polishing rates than in Example 10 were obtained. From these results, by using a polishing composition containing abrasive grains having an average aspect ratio of 1.11 or more and a D ₉₉ of less than 295 nm, while realizing a practical polishing rate, residual particles can be effectively reduced.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

Claims (5)

A polishing composition used in a pre-polishing step of a magnetic disk substrate plated with nickel phosphorous ,
Abrasive grains containing silica particles and water,
The abrasive grains have an average aspect ratio of 1.1 or more and a cumulative frequency 99% particle diameter (D ₉₉ ) of less than 295 nm by a light transmission centrifugal sedimentation method ,
The polishing composition, wherein the abrasive grains have a cumulative 50% frequency particle diameter (D ₅₀ ) of 80 nm or more as determined by a light transmission centrifugal sedimentation method . The polishing composition according to claim 1 , further comprising an acid and an oxidizing agent. A step (1) of supplying the polishing composition according to claim 1 or 2 to a substrate to be polished and polishing the substrate to be polished;
A method of polishing a substrate, comprising a step (2) of cleaning the substrate to be polished after the step (1). 4. The method of polishing a substrate according to claim 3 , further comprising a step (3) of supplying a final polishing composition to the substrate to be polished and polishing the substrate to be polished after the step (2). A step (1) of polishing a substrate to be polished using the polishing composition according to claim 1 or 2 ;
A method for manufacturing a substrate, comprising a step (2) of cleaning the substrate to be polished after the step (1).

Images