JP2008307676A - Polishing liquid composition for hard disk substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polishing liquid composition for a hard disk substrate capable of reducing piercing of abrasive grains and surface staining on the substrate after polishing, and a method for manufacturing the hard disk substrate using the composition. <P>SOLUTION: This polishing liquid composition contains aluminum oxide particles, organic nitrogen compounds and water. A volume medium particle diameter of a secondary particle of the aluminum oxide particle is 0.1 to 0.7 μm. Content of particles having particle diameters of 1 μm or more in aluminum oxide particles is 0.2 wt.% or less. The organic nitrogen compounds have two or more amino groups and/or imino groups in molecules. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polishing composition for a hard disk substrate and a method for producing a hard disk substrate using the same.

  With the rapid spread of computers and the start of digital broadcasting, there is a need for higher capacity and smaller diameter hard disk drives. For example, as a method for increasing the recording density of a memory hard disk used in a hard disk drive, it has been proposed to reduce the flying height of the magnetic head and reduce the unit recording area. However, in order to cope with the low flying height of the head, it is necessary to reduce the surface roughness, minute waviness, roll-off and the like of the surface of the hard disk substrate. In order to satisfy such requirements, abrasive slurry (Patent Documents 1 and 2) that can reduce scratches on the substrate after polishing, and polishing liquid composition that can reduce surface defects such as surface contamination of the substrate after polishing (Patent Documents) 3 and 4) are known.

In a manufacturing method of a hard disk substrate, a multi-stage polishing method having two or more polishing steps is often employed from the viewpoint of achieving both surface quality improvement and productivity improvement such as smoother and less scratches. In the final polishing step of the multi-stage polishing method, that is, the final polishing step, in order to satisfy the requirements of reducing the surface roughness and reducing the scratches, the polishing is generally performed with a polishing composition for finishing using colloidal silica particles. On the other hand, in the polishing prior to the final polishing step, from the viewpoint of productivity, abrasive grains having a relatively large particle diameter that can realize a high polishing rate, for example, aluminum oxide particles tend to be used.
JP 2000-15560 A JP 2000-458 A JP 2002-163407 A JP 2006-150534 A

  However, when aluminum oxide particles are used as abrasive grains, there is a problem that defects in the media are caused as a texture scratch, and further, magnetic characteristics are lowered, that is, a signal to noise ratio (SNR) is lowered. Further, even in a perpendicular recording substrate that is not subjected to texture processing, when the abrasive grains are used, there is a problem that it may cause a recording error, a decrease in magnetic characteristics, a decrease in SNR, and the like. Further, in order to achieve the surface quality necessary for increasing the density of the memory hard disk substrate, it is also an important issue to reduce residues such as abrasive grains and polishing residue on the substrate after polishing.

  The present invention relates to a polishing liquid composition containing aluminum oxide particles as abrasive grains, a polishing liquid composition for a hard disk substrate capable of remarkably improving the surface quality of the hard disk substrate, and a method of manufacturing a hard disk substrate using the same. provide.

  The polishing liquid composition for a hard disk substrate of the present invention (hereinafter also referred to as the polishing liquid composition of the present invention) contains aluminum oxide particles, an organic nitrogen compound, and water, and is in the volume of secondary particles of the aluminum oxide particles. The particle size is 0.1 to 0.7 μm, the content of particles having a particle size of 1 μm or more in the aluminum oxide particles is 0.2% by weight or less, and the organic nitrogen compound is A polishing composition for a hard disk substrate, which is an organic nitrogen compound having two or more amino groups and / or imino groups. The method for producing a hard disk substrate of the present invention is a method for producing a hard disk substrate including a step of polishing a substrate to be polished using the polishing composition.

  When the polishing composition of the present invention is used for polishing prior to the final polishing step of a hard disk substrate, for example, a hard disk substrate suitable for high recording density in which piercing of the aluminum oxide particles to the substrate and surface contamination of the substrate are reduced. The effect that can be manufactured is produced.

  In the present invention, the “piercing” of the abrasive grains refers to a state in which the abrasive grains are pushed into the substrate and remain, unlike the abrasive grains attached to the substrate. This “piercing” is a polishing liquid composition containing colloidal particles as abrasive grains, as will be described later, and after polishing the substrate surface slightly to remove the abrasive grains adhering to the substrate, the substrate surface Can be examined by dark field microscopy, atomic force microscopy (AFM) or scanning electron microscopy (SEM).

  If this piercing occurs, defects such as deep scratches on the surface occur in the texture processing performed in the media forming process of the hard disk substrate, or the magnetic characteristics of the completed hard disk deteriorate, that is, the signal to noise ratio (SNR). This is thought to cause a decrease in Therefore, reducing the piercing of the abrasive grains is important for obtaining an excellent hard disk substrate.

  The present invention controls the particle diameter of aluminum oxide particles, which are abrasive grains of a polishing composition, to a specific size, and reduces coarse particles of a specific size present in the abrasive grains to a specific amount or less. This is based on the knowledge that it becomes possible to reduce the sticking of abrasive grains to the substrate after polishing.

  In the present invention, “surface contamination” of the substrate after polishing means that, unlike the “piercing”, abrasive grains and polishing residue used in the polishing step remain on the surface of the substrate after polishing. If these residues are present, for example, it may adversely affect the next polishing process and the final polishing process, and may cause scratches and pits, resulting in a decrease in the surface quality of the hard disk substrate. In the present invention, the surface contamination and its reduction effect can be evaluated by, for example, microscopic observation of a substrate surface obtained after polishing, observation by a scanning electron microscope, etc. It can be evaluated by observing the parts with these instruments. Further, the polishing substrate surface can be evaluated by glow discharge spectroscopic analysis (GDOES) or the like.

  The present invention provides a polishing composition containing an organic nitrogen compound having an amino group and / or imino group in the molecule and an acid together with the predetermined aluminum oxide particles, and polishing the substrate after polishing. This is based on the knowledge that a polishing method capable of reducing the surface sticking as well as reducing the piercing of the grains is possible. Although the mechanism by which the organic nitrogen compound reduces the piercing of abrasive grains is not clear, by using the predetermined aluminum oxide particles and the organic nitrogen compound, the aluminum oxide particles remaining on the substrate surface are reduced, and finish polishing. This is probably because the stab of aluminum oxide particles in the process is suppressed.

  As described above, the polishing liquid composition of the present invention contains aluminum oxide particles, an organic nitrogen compound, and water, and the volume-median particle diameter of secondary particles of the aluminum oxide particles is 0.1 to 0.00. 7 μm, the content of particles having a particle diameter of 1 μm or more in the aluminum oxide particles is 0.2% by weight or less, and the organic nitrogen compound has two or more amino groups and / or imino groups in the molecule. One of the technical features is that it is an organic nitrogen compound. By providing such technical features, the present invention provides a polishing method capable of reducing both the sticking of abrasive grains and surface contamination on a polished substrate, and a hard disk substrate suitable for high recording density with excellent surface quality. Can be provided.

[Aluminum oxide particles]
The polishing liquid composition of the present invention contains aluminum oxide (hereinafter sometimes referred to as alumina) particles as abrasive grains. The aluminum oxide particles used in the present invention are preferably alumina having a purity of 95% or more, more preferably 97, from the viewpoints of piercing reduction, waviness reduction, surface roughness reduction, polishing rate improvement and surface defect prevention. % Or more, more preferably 99% or more of alumina. Further, α-alumina is preferable from the viewpoint of improving the polishing rate, and intermediate alumina and amorphous alumina are preferable from the viewpoint of surface properties and undulation reduction. Intermediate alumina is a generic term for crystalline alumina particles other than α-alumina, and specifically includes γ-alumina, δ-alumina, θ-alumina, η-alumina, κ-alumina, and mixtures thereof. It is done. Among the intermediate aluminas, γ-alumina, δ-alumina, θ-alumina and mixtures thereof are preferable from the viewpoint of improving the polishing rate and reducing waviness, and more preferably γ-alumina and θ-alumina. From the viewpoint of improving the polishing rate and reducing waviness, it is preferable to use a mixture of α-alumina, intermediate alumina and / or amorphous alumina, and a mixture of α-alumina and θ-alumina. More preferred. In addition, the content of α-alumina in the aluminum oxide particles is preferably 20% by weight or more, more preferably 30% by weight or more, further preferably 40% by weight or more, and 50% by weight from the viewpoint of improving the polishing rate and reducing waviness. % Or more is more preferable, and from the viewpoint of roll-off reduction, 10 to 90% by weight is preferable, 20 to 80% by weight is more preferable, and 30 to 70% by weight is further preferable. In the present invention, the content of α-alumina in the aluminum oxide particles is such that the peak area of the 104 plane of WA-1000 (shown by Showa Denko Co., Ltd.) is 100%, Determined by relative comparison of corresponding peak areas.

  The volume median particle diameter of the secondary particles of the aluminum oxide particles is 0.7 μm or less, preferably 0.5 μm or less, more preferably 0.4 μm or less, and more preferably 0.35 μm from the viewpoints of reducing sticking and surface contamination. The following is more preferable, 0.3 μm or less is still more preferable, and 0.25 μm or less is even more preferable. Further, the particle diameter is 0.1 μm or more, preferably 0.15 μm or more, and more preferably 0.2 μm or more from the viewpoint of improving the polishing rate. That is, the particle diameter is 0.1 to 0.7 μm, preferably 0.1 to 0.5 μm, more preferably 0.1 to 0.4 μm, still more preferably 0.15 to 0.35 μm, More preferably, it is 0.15-0.3 micrometer, More preferably, it is 0.2-0.25 micrometer. Among them, the volume-median particle diameter of the secondary particles of α-alumina is preferably 0.1 to 0.7 μm, preferably 0.1 to 0.5 μm, from the viewpoints of reducing piercing, reducing surface contamination, and improving the polishing rate. Is more preferable, 0.1 to 0.4 μm is more preferable, 0.1 to 0.35 μm is still more preferable, 0.15 to 0.3 μm is still more preferable, and 0.15 to 0.25 μm is still more preferable. .

  The average particle diameter of the primary particles of the aluminum oxide particles is preferably 0.005 to 0.5 μm, more preferably 0.01 to 0.4 μm, and more preferably 0.03 to 0.3 μm from the viewpoints of reducing sticking and reducing surface contamination. Is more preferable, and 0.05 to 0.2 μm is even more preferable. Among these, the average particle diameter of the primary particles of α-alumina is preferably 0.05 to 0.5 μm, more preferably 0.05 to 0.4 μm, from the viewpoint of improving the polishing rate, reducing piercing, and reducing surface contamination. 0.05 to 0.3 μm is more preferable, and 0.07 to 0.2 μm is even more preferable.

The average particle diameter (volume basis) of primary particles of aluminum oxide particles and the volume median particle diameter of secondary particles of less than 0.1 μm are observed with a scanning electron microscope (preferably 3000 to 30000 times) or transmission electrons. It can be obtained by observing with a microscope (preferably 10,000 to 300,000 times), performing image analysis, and measuring the particle diameter. Specifically, using an enlarged photograph or the like, the maximum length of each primary particle or secondary particle is measured for at least 200 particles, and the volume of a sphere having the length as a diameter is calculated. The particle diameter (D ₅₀ ) at which the cumulative volume frequency from 50% becomes the average particle diameter of primary particles or the volume-median particle diameter of secondary particles, respectively. Further, the volume median particle diameter (D ₅₀ ) of secondary particles of 0.1 μm or more is measured using a laser light diffraction method.

The specific surface area of α-alumina measured by the BET method is preferably from 0.1 to 50 m ² / g, more preferably from 1 to 40 m ² / g, from the viewpoint of improving the polishing rate, reducing piercing, and reducing surface contamination. More preferably, it is 2-20 m < ² > / g. Furthermore, the specific surface area of the intermediate alumina or amorphous alumina measured by the BET method is preferably 30 to 300 m ² / g, more preferably 50 to ²⁰⁰ m ² / g.

  The content of the aluminum oxide particles in the polishing composition is preferably 0.05% by weight or more, more preferably 0.1% by weight or more, and still more preferably, from the viewpoints of improving the polishing rate, reducing piercing, and reducing surface contamination. It is 0.5% by weight or more, and more preferably 1% by weight or more. The content is preferably 30% by weight or less, more preferably 20% by weight or less, still more preferably 15% by weight or less, and even more preferably 10% by weight or less, from the viewpoint of improving surface quality and economy. . That is, the content of aluminum oxide particles in the polishing composition is preferably 0.05 to 30% by weight, more preferably 0.1 to 20% by weight, still more preferably 0.5 to 15% by weight, and even more preferably. Is 1 to 10% by weight.

  The content of coarse particles having a particle diameter of 1 μm or more in the aluminum oxide particles is 0.2% by weight or less, preferably 0.15% by weight or less, more preferably 0, from the viewpoint of reducing sticking and reducing surface contamination. .1% by weight or less, more preferably 0.05% by weight or less. In addition, the content of coarse particles having a particle diameter of 3 μm or more in the aluminum oxide particles is preferably 0.05% by weight or less, more preferably 0.04% by weight or less, and still more preferably 0.03 from the same viewpoint. % By weight or less, still more preferably 0.02% by weight or less, still more preferably 0.01% by weight or less. The “coarse particles having a particle diameter of 1 μm or more” or “coarse particles having a particle diameter of 3 μm or more” includes not only primary particles but also secondary particles in which primary particles are aggregated.

  For the measurement of the content of the coarse particles in the polishing liquid composition, a number counting method (Sizing Particle Optical Sensing method) is used. Specifically, the content can be determined by measuring the particle diameter of aluminum oxide particles with “Accusizer 780” manufactured by Particle Sizing Systems, USA.

  The method for controlling the content of coarse particles having a particle diameter of 1 μm or more in the aluminum oxide particles is not particularly limited, and a general dispersion method or particle removal method can be used during or after the production of the polishing composition. Can be used. For example, in order to obtain a specific average particle size, the aluminum oxide particle slurry uniformly crushed by a wet circulating bead mill is further subjected to a sedimentation method using a stationary precipitation method, a centrifugal separator, or a microfiltration using a filtering material The content can be controlled by subjecting to a method for removing coarse particles. About the removal method of a coarse particle, you may process by a single method each, or may combine and process 2 or more types, and there is no restriction | limiting also about the process sequence of a combination. Further, the processing conditions and the number of processing times can be appropriately selected and used.

[Organic nitrogen compounds]
The organic nitrogen compound used in the polishing liquid composition of the present invention is a compound having a total of two or more amino groups and / or imino groups in the molecule. The number of amino groups and imino groups in the molecule is preferably from 2 to 2000, more preferably from 2 to 1000, and even more preferably from 2 to 50, from the viewpoints of reducing sticking and reducing surface contamination. Specific examples include polyalkyleneimines, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, bis (3-aminopropyl) amine, 1,3-propanediamine and the like.

  Typical examples of the polyalkyleneimines include polyethyleneimine, polypropyleneimine, polybutadieneimine, and the like, and examples include linear, branched, and cyclostructured ones. Among these, polyethyleneimine is preferable from the viewpoint of reducing sticking and reducing surface contamination. The number average molecular weight is preferably from 150 to 100,000, more preferably from 200 to 30,000, still more preferably from 200 to 10,000, and even more preferably from 300 to 2,000, from the viewpoints of reducing sticking and reducing surface contamination.

  In addition, the content of the organic nitrogen compound in the polishing composition is preferably 0.001 to 0.5% by weight, and 0.001 to 0.3% by weight from the viewpoint of reducing sticking and reducing surface contamination. More preferred is 0.001 to 0.1% by weight.

[acid]
The polishing composition of the present invention preferably contains an acid from the viewpoints of improving the polishing rate, reducing piercing, and reducing surface contamination. The acid used in the polishing composition of the present invention preferably has a pK1 of 7 or less, more preferably 5 or less, still more preferably 3 or less, from the viewpoint of improving the polishing rate, reducing sticking and reducing surface contamination. More preferably, the acid is 2 or less. Here, pK1 is a logarithmic value of the reciprocal of the first acid dissociation constant (25 ° C.). PK1 of each compound is described, for example, in Chemical Handbook 4th edition (basic edition) II, p316 to 325 (edited by the Chemical Society of Japan).

  Specific examples of the acid used in the present invention are shown below. Examples of inorganic acids include monovalent mineral acids such as nitric acid, hydrochloric acid, perchloric acid, and amidosulfuric acid, and polyvalent mineral acids such as sulfuric acid, sulfurous acid, phosphoric acid, pyrophosphoric acid, polyphosphoric acid, phosphonic acid, and phosphinic acid. . Organic acids include formic acid, acetic acid, glycolic acid, lactic acid, propanoic acid, hydroxypropanoic acid, butyric acid, benzoic acid, glycine and other monocarboxylic acids, oxalic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid Acids, itaconic acid, malic acid, tartaric acid, citric acid, isocitric acid, phthalic acid, polyvalent carboxylic acids such as nitrotriacetic acid, ethylenediaminetetraacetic acid, alkylsulfonic acids such as methanesulfonic acid and paratoluenesulfonic acid, ethylphosphoric acid, butylphosphorus Examples thereof include alkylphosphoric acids such as acids, phosphonohydroxyacetic acid, hydroxytylidenediphosphonic acid, phosphonobutanetricarboxylic acid, and phosphonic acids such as ethylenediaminetetramethylenephosphonic acid. Among these, from the viewpoint of improving the polishing rate and reducing piercing and undulation, polyvalent acids are preferred, more preferred are polyvalent mineral acids, polyvalent organic carboxylic acids and polyvalent organic phosphonic acids, and even more preferred are polyvalent minerals. Acids and polyvalent organic carboxylic acids. Here, the polyvalent acid refers to an acid having two or more hydrogen atoms capable of generating hydrogen ions in the molecule. Further, nitric acid, sulfuric acid, sulfonic acid and carboxylic acid are preferable from the viewpoint of preventing surface contamination of the object to be polished.

  Although the said acid may be used independently, it is preferable to mix and use 2 or more types. In particular, when polishing a metal surface such as a Ni-P plated substrate, the metal ions of the object to be polished are eluted during polishing, the pH of the polishing composition increases, and a high polishing rate cannot be obtained. In order to reduce the pH change, it is preferable to use a combination of an acid having a pK1 of less than 2.5 and an acid having a pK1 of 2.5 or more, and an acid having a pK1 of 1.5 or less and a pK1 of 2.5 or more. More preferably, it is used in combination with an acid. In the case where such two or more acids are contained, considering the improvement in polishing rate, reduction in waviness, and availability, the acids having a pK1 of less than 2.5 include minerals such as nitric acid, sulfuric acid, phosphoric acid, and polyphosphoric acid. It is preferable to use an acid or an organic phosphonic acid. On the other hand, as the acid having a pK1 of 2.5 or more, from the same viewpoint, organic carboxylic acids such as acetic acid, succinic acid, malic acid, tartaric acid, citric acid, and itaconic acid are preferable. Among them, succinic acid, malic acid, and tartaric acid are preferable. Citric acid and itaconic acid are preferable, and citric acid is more preferable. Further, from the viewpoint of improving the polishing rate and reducing waviness, when using an organic carboxylic acid having a pK1 of 2.5 or more, it is more preferable to use a combination of an oxycarboxylic acid and a divalent or higher polyvalent carboxylic acid. . For example, examples of the oxycarboxylic acid include citric acid, malic acid, and tartaric acid, and examples of the polyvalent carboxylic acid include succinic acid, maleic acid, and itaconic acid. Therefore, it is preferable to use one or more of these in combination, and among these, it is preferable to combine citric acid and polyvalent carboxylic acid.

  The content of the acid in the polishing composition is preferably 0.002% by weight or more, more preferably 0.005% by weight or more, and still more preferably 0, from the viewpoints of improving the polishing rate, reducing piercing, and reducing surface contamination. 0.007% by weight or more, still more preferably 0.01% by weight or more. The content is preferably 20% by weight or less, more preferably 15% by weight or less, still more preferably 10% by weight or less, and still more preferably 5% by weight or less, from the viewpoint of surface quality and economy. That is, the acid content in the polishing composition is preferably 0.002 to 20% by weight, more preferably 0.005 to 15% by weight, still more preferably 0.007 to 10% by weight, and still more preferably. 0.01 to 5% by weight. Further, from the viewpoint of improving the polishing rate, the weight ratio of an acid having a pK1 of less than 2.5 and an acid having a pK1 of 2.5 or more [(an acid having a pK1 of less than 2.5) / (pK1 of 2.5 or more). The acid)] is preferably 9/1 to 1/9, more preferably 7/1 to 1/7, and still more preferably 5/1 to 1/5.

  In the polishing composition of the present invention, the weight ratio of the organic nitrogen compound to the acid (organic nitrogen compound / acid) is 1/1 from the viewpoint of improving the polishing rate, reducing piercing, and reducing surface contamination. 10,000 to 1/1 is preferable, 1/1000 to 1/2 is more preferable, and 1/500 to 1/5 is more preferable.

[water]
The water in the polishing composition of the present invention is used as a medium, and ion exchange water, pure water, ultrapure water, or the like can be used. The content of water in the polishing composition is preferably 55 to 99% by weight, more preferably 60 to 97% by weight, and still more preferably 70 to 95% by weight, from the viewpoint of efficiently polishing an object to be polished. .

[Oxidant]
The polishing composition of the present invention preferably contains an oxidizing agent from the viewpoints of improving the polishing rate, reducing piercing, and reducing surface contamination. Examples of the oxidizing agent used in the present invention include peroxides, metal peroxo acids or salts thereof, or oxygen acids or salts thereof. Oxidizing agents are roughly classified into inorganic oxidizing agents and organic oxidizing agents according to their structures. Examples of inorganic oxidants include hydrogen peroxide; alkali metal or alkaline earth metal peroxides such as sodium peroxide, potassium peroxide, calcium peroxide, barium peroxide, and magnesium peroxide; sodium peroxocarbonate, peroxo Peroxocarbonates such as potassium carbonate; peroxosulfuric acid such as ammonium peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate, peroxomonosulfuric acid or the like; peroxo such as sodium peroxophosphate, potassium peroxophosphate, ammonium peroxophosphate Peroxoborate such as sodium peroxoborate and potassium peroxoborate; peroxochromate such as sodium peroxochromate and potassium peroxochromate; sodium permanganate Permanganates such as sodium and potassium permanganate; halogen-containing substances such as sodium perchlorate, potassium perchlorate, sodium hypochlorite, sodium periodate, potassium periodate, sodium iodate, potassium iodate And oxygen acid salts; and inorganic acid metal salts such as iron chloride (III) and iron sulfate (III). Examples of organic oxidizing agents include percarboxylic acids such as peracetic acid, performic acid, and perbenzoic acid; peroxides such as t-butyl peroxide and cumene peroxide; and organic acids such as iron (III) citrate Examples thereof include iron (III) salts. Among these, an inorganic oxidizing agent is preferable from the viewpoints of improvement in polishing rate, availability, and handleability such as solubility in water. Of these, hydrogen peroxide, sodium peroxoborate, sodium iodate and potassium iodate are preferred. These oxidizing agents may be used alone or in combination of two or more.

  The content of the oxidizing agent in the polishing liquid composition is preferably 0.002% by weight or more, more preferably 0.005% by weight or more, from the viewpoints of improving the polishing rate, reducing piercing, and reducing surface contamination. % By weight or more is more preferable, and 0.01% by weight or more is even more preferable. Moreover, from a viewpoint of roll-off reduction and surface quality, 20 weight% or less is preferable, 15 weight% or more is more preferable, 10 weight% or less is more preferable, and 5 weight% or less is further more preferable. That is, the content of the oxidizing agent in the polishing composition is preferably 0.002 to 20% by weight, more preferably 0.005 to 15% by weight, still more preferably 0.007 to 10% by weight, Even more preferred is ˜5 wt%.

[PH of polishing composition]
It is preferable that the pH of the polishing composition of the present invention is appropriately determined according to the type of the object to be polished and the required quality. For example, the pH of the polishing composition is preferably less than 7 from the viewpoints of improving the polishing rate, reducing piercing and reducing surface contamination, and from the viewpoint of corrosion prevention of processing machines and the safety of workers. Is more preferably 0.5-5, even more preferably 1-5, even more preferably 1-4, and even more preferably 1-3. Where necessary, the pH may be selected from inorganic acids such as nitric acid and sulfuric acid, organic acids such as oxycarboxylic acids, polyvalent carboxylic acids, aminopolycarboxylic acids and amino acids, and metal salts and ammonium salts thereof, ammonia, sodium hydroxide, It can adjust by mix | blending basic substances, such as potassium hydroxide and an amine, with a desired quantity suitably.

[Other ingredients]
Further, the polishing liquid composition of the present invention may further contain other components according to the purpose of improving the polishing rate, reducing the piercing and reducing the surface contamination, and other purposes. Examples of other components include metal oxide abrasive grains such as colloidal silica, fumed silica, and colloidal titanium oxide, inorganic salts, thickeners, rust preventives, and basic substances. Examples of inorganic salts include ammonium nitrate, ammonium sulfate, potassium sulfate, nickel sulfate, aluminum nitrate, aluminum sulfate, and ammonium sulfamate. The inorganic salt can be used for the purpose of improving the polishing rate, improving the roll-off, and preventing caking of the polishing composition. The other components may be used alone or in combination of two or more. The content of the other component in the polishing composition is preferably 0.05 to 20% by weight, more preferably 0.05 to 10% by weight, and still more preferably 0.05 to 5% from the viewpoint of economy. % By weight.

  Furthermore, a bactericidal agent, an antibacterial agent, etc. can be mix | blended with the polishing liquid composition of this invention as another component as needed. The content of these bactericides and antibacterial agents in the polishing liquid composition is preferably 0.0001 to 0.1% by weight from the viewpoint of exerting the function, and from the viewpoint of influence on polishing performance and economy. More preferably, it is 0.001-0.05 weight%, More preferably, it is 0.002-0.02 weight%.

[Method for preparing polishing liquid composition]
The method for preparing the polishing composition of the present invention is not limited at all, and can be prepared by mixing at least the aluminum oxide particles and the organic nitrogen compound with water. Dispersion | distribution in particular of the said aluminum oxide particle is not restrict | limited, It can carry out using stirrers etc., such as a homomixer, a homogenizer, an ultrasonic disperser, and a wet ball mill. The concentration of each component in the polishing liquid composition of the present invention is a preferable concentration when polishing, but when the polishing liquid composition is prepared as a concentrated liquid, it is described above before or during use. It is preferable to dilute so as to obtain the concentration. In addition, the polishing composition can be prepared by adding and mixing the target components by any method.

  In addition, the polishing composition of the present invention has an intermediate composition (hereinafter, also referred to as an intermediate polishing composition) having a composition obtained by removing the organic nitrogen compound from the polishing composition of the present invention immediately before use. It may be prepared by mixing with an organic nitrogen compound. For example, when the polishing liquid composition of the present invention is used in a polishing machine, the polishing liquid composition of the present invention is prepared by adding the organic nitrogen compound to the intermediate polishing liquid composition in the supply pipe to the polishing machine. Alternatively, the polishing composition of the present invention may be prepared by adding the organic nitrogen compound simultaneously with supplying the intermediate polishing composition to the polishing machine.

[Polished substrate]
Examples of the substrate to be polished using the polishing composition of the present invention include those usually used for the production of a hard disk substrate or a magnetic recording medium substrate. As a specific example of the substrate to be polished, a substrate obtained by plating a Ni—P alloy on an aluminum alloy is representative, but glass or glassy carbon is used instead of the aluminum alloy, and Ni—P plating is applied thereto. Instead of the substrate or Ni-P plating, a substrate in which various metal compounds are coated by plating or vapor deposition can be used.

[Polishing method]
As a polishing method using the polishing liquid composition of the present invention, for example, a substrate to be polished is sandwiched by a polishing board provided with a polishing pad made of a nonwoven or porous organic polymer, and the polishing liquid composition of the present invention is used. The substrate to be polished can be polished by supplying the polishing surface and moving the polishing disk or the substrate to be polished while applying pressure. In polishing, the polishing composition of the present invention may be used as it is, or diluted if it is a concentrated solution. When diluting the concentrated liquid, the dilution ratio is not particularly limited, and can be appropriately determined according to the concentration of each component (such as the content of abrasive grains) in the concentrated liquid and the polishing conditions. Moreover, as described above, the intermediate polishing composition and the organic nitrogen compound are prepared, and the polishing of the present invention is performed by adding the organic nitrogen compound to the intermediate polishing composition in the supply pipe to the polishing machine. You may supply a liquid composition, or you may supply the polishing liquid composition of this invention by adding the said organic nitrogen compound simultaneously with supplying the said intermediate | middle polishing liquid composition to a grinder.

  The polishing load means the pressure of the surface plate applied to the polishing surface of the substrate to be polished during polishing. The polishing load in the production method of the present invention is preferably 50 kPa or less, more preferably 40 kPa or less, and even more preferably 30 kPa or less, from the viewpoint of reducing the sticking of aluminum oxide particles to the substrate and reducing the surface contamination of the substrate after polishing. . The polishing load is preferably 3 kPa or more, more preferably 5 kPa or more, and even more preferably 7 kPa or more, from the viewpoint of productivity (polishing rate). Therefore, the polishing load is preferably 3 to 50 kPa, more preferably 5 to 40 kPa, and even more preferably 7 to 30 kPa. The polishing load can be adjusted by applying air pressure or weight to the surface plate or the substrate.

The supply rate of the polishing composition is preferably 0.25 mL / min or less, more preferably 0.2 mL / min or less per 1 cm ^{2 of the} substrate to be polished, from the viewpoint of low cost. The supply rate is preferably 0.01 mL / min or more per 1 cm ^{2 of the} substrate to be polished, more preferably 0.025 mL / min or more, and even more preferably 0.05 mL / min or more because the polishing rate can be further improved. is there. Accordingly, the supply rate is preferably 0.01 to 0.25 mL / min per 1 cm ^{2 of the} substrate to be polished, more preferably 0.025 to 0.2 mL / min, and still more preferably 0.05 to 0.15 mL. / Min.

  The polishing method using the polishing liquid composition of the present invention preferably reduces the sticking of the abrasive grains and surface contamination on the substrate after polishing without reducing the polishing rate, and therefore preferably increases the recording density. A suitable hard disk substrate can be provided.

[Method of manufacturing hard disk substrate]
The method for producing a hard disk substrate of the present invention (hereinafter also referred to as the production method of the present invention) is a step of polishing a substrate to be polished by the above-described polishing method using the polishing composition of the present invention (hereinafter referred to as “polishing step”). May be referred to as).

  The hard disk substrate obtained by using the manufacturing method of the present invention is suitable for increasing the recording density because, for example, the surface quality is improved by reducing the piercing and surface contamination of aluminum oxide particles.

  Further, the production method of the present invention is preferably a multi-stage polishing method having two or more stages of polishing processes, and the above-mentioned “polishing process” is performed in a process prior to the final polishing process which is the final process. Is preferred. In the polishing composition used in the final polishing process, from the viewpoint of the surface quality of the hard disk substrate, for example, from the viewpoint of reducing waviness, reducing the surface roughness, and reducing surface defects such as scratches, abrasive particles (abrasive grains) The average particle diameter of the primary particles is preferably 0.1 μm or less, more preferably 0.08 μm or less, further preferably 0.05 μm or less, and even more preferably 0.03 μm or less. preferable. Further, from the viewpoint of improving the polishing rate, the average particle diameter is preferably 0.005 μm or more, and more preferably 0.01 μm or more.

  As abrasive particles in the polishing liquid composition used in the final polishing step, fumed silica abrasive grains, colloidal silica abrasive grains and the like can be mentioned, from the viewpoint of reducing surface roughness and reducing surface defects such as scratches. Colloidal silica abrasive is preferred. The average particle diameter of primary particles of colloidal silica abrasive grains is preferably 0.005 to 0.08 μm, more preferably 0.005 to 0.05 μm, and still more preferably 0.01 to 0.03 μm.

  In the final polishing step, when using abrasive particles having an average primary particle size of 0.005 to 0.1 μm, the viewpoint of reducing the surface roughness, reducing the sticking of the aluminum oxide particles, and productivity (polishing time) From this viewpoint, the polishing amount is preferably 0.05 to 0.5 μm, more preferably 0.1 to 0.4 μm, and further preferably 0.2 to 0.4 μm. There are no particular limitations on the other conditions (type of polishing machine, polishing temperature, polishing rate, supply amount of polishing liquid, etc.) when performing final polishing, and the polishing load is exemplified in the above-mentioned “polishing step”. It may be the same as the polishing load. The polishing amount can be determined as in the examples described later.

  The polishing composition of the present invention is particularly effective in the polishing step in the method of manufacturing a hard disk substrate, but can be similarly applied to other polishing steps such as a lapping step.

1. Coarse particle removal treatment of aluminum oxide particles An aluminum oxide slurry was prepared as follows.
(1) Nitric acid was added to 50 kg of an aluminum oxide slurry containing 10% by weight of aluminum oxide particles having a purity of 99.9% shown in Table 1 below, and the pH was adjusted to 3.
(2) The aluminum oxide slurry obtained in (1) was transferred to a cylindrical container having a diameter of 40 cm and a height of 50 cm.
(3) The aluminum oxide slurry in the container was stirred to be uniform.
(4) The aluminum oxide slurry after stirring was allowed to stand for 3 to 10 hours.
(5) Leave about 5 cm of the lower layer portion of the aluminum oxide slurry after standing, move the upper layer portion to another container having the same shape, and perform the operations (3) and (4) for the upper layer portion.
(6) The above (5) was further repeated 2 to 4 times to obtain an aluminum oxide slurry from which various coarse particles were removed.

2. Preparation of Polishing Liquid Composition Aluminum oxide slurry shown in Table 1 below and organic nitrogen compound shown in Table 2 below were mixed with 0.5 wt% sulfuric acid (98 wt% product), 0.6 wt% citric acid, ammonium sulfate 0 The mixture was mixed with 0.5 wt%, hydrogen peroxide (35 wt% product, manufactured by Asahi Denka Co., Ltd.) 0.6 wt% and ion-exchanged water (remainder) and stirred. The obtained slurry was filtered with a back filter (manufactured by Hayward Japan, model number: PE1-P03H-403) to obtain polishing liquid compositions of Examples 1 to 11 and Comparative Examples 1 to 9 shown in Table 3 below. .

3. Polishing method The surface of a substrate made of a Ni-P plated aluminum alloy having a thickness of 1.27 mm and a diameter of 3.5 inches is polished by a double-sided processing machine under the following setting conditions, and Ni used as a substrate for a magnetic recording medium A polished product of an aluminum alloy substrate plated with -P was obtained. The substrate used for polishing had an amplitude of short wavelength waviness (wavelength: 50 to 500 μm) in the measurement using “New View 5032 manufactured by Zygo Corporation” of 3.8 nm, and long wave waviness (wavelength: 0.5 to 5 mm) was 1.6 nm.
Setting conditions of the double-sided machine Double-sided machine: Speed Fam Co., Ltd., 9B type double-sided machine Polishing load: 9.8 kPa
Polishing pad: 1P polishing pad manufactured by Fujibow Co., Ltd. Average pore diameter 45 μm
Plate rotation speed: 45r / min
Polishing liquid composition supply flow rate: 100 mL / min
Polishing time: 4 min
Number of substrates loaded: 10

4). Evaluation Method (1) Evaluation of Abrasion of Abrasive Grain The substrate surface after polishing was polished so that the polishing amount would be 0.035 μm ± 0.005 μm using the following polishing composition for finishing. By doing so, the piercing of the abrasive grains was evaluated. The composition of the polishing composition for finishing, the polishing conditions, the measuring method of the polishing amount, the piercing observation method and the evaluation criteria are shown below.
Polishing composition for finishing colloidal silica slurry (manufactured by DuPont, average particle diameter of primary particles 0.02 μm) as silica particle concentration is 7% by weight, HEDP (1-hydroxyethylidene-1,1-diphosphonic acid, Sorcia Japan (Made by Asahi Denka Co., Ltd.) was used as an effective component, and hydrogen peroxide (manufactured by Asahi Denka) was used as an effective component in an amount of 0.6% by weight.
Polishing conditions Polishing tester: Speed Fam Co., Ltd., double-sided 9B polishing machine Polishing pad: Fujibow Co., Ltd. urethane finishing polishing pad upper surface plate rotation speed: 32.5r / min
Polishing liquid composition supply amount: 100 mL / min
Polishing time: 0.5 to 1.5 min (adjusted so that the polishing amount becomes 0.035 μm ± 0.005 μm)
Polishing load: 4.1 kPa
Number of substrates loaded: 10
Measuring method of polishing amount Each substrate before and after polishing was weighed (measured by Sartorius, “BP-210S”), and introduced into the following formula to determine the polishing amount.
Weight reduction (g) = {weight before polishing (g) −weight after polishing (g)}
Polishing amount (μm) = weight reduction amount (g) / substrate single-sided area (mm2) / 2 / Ni-P plating density (g / cm ³ ) × 10 ⁶
(The substrate single-sided area is calculated as 6597 mm ² and Ni-P plating density 8.4 g / cm ³ )
Method of piercing observation Using an Olympus optical microscope (main body BX60M, digital camera DP70, objective lens 200 times, intermediate lens 2.5 times), abrasive grains pierced by dark field observation (field of view 550 × 420 μm) as bright spots The number was detected and the number was measured. In the above-described observation, two were arbitrarily selected from the 10 substrates after polishing, and a total of 16 points were observed at 4 points for each 90 ° at a position 30 mm from the center on both surfaces of the substrate. The observed image was taken into a personal computer (PC), and the number of bright spots was determined by image analysis software WinRof (Mitani Corporation). And the average value of the observed number of bright spots was made into the number of piercings of an abrasive grain.
Piercing evaluation criteria 5: The number of sticking is 0 to 200
4: Number of piercings is 201 to 400
3: Number of piercings is 401 to 800
2: The number of piercings is 801 to 1200
1: More than 1201 sticks

(2) Surface contamination The surface of each substrate after polishing was observed at a magnification of 10,000 with a scanning electron microscope (manufactured by Hitachi, Ltd .: S-4000), and the following five-stage evaluation was performed. 1 and 2 are practical defects.
5: No alumina residue or polishing debris observed on the surface 4: Very little observed 3: Some observed 2: Many observed 1: Very many observed

(3) Measurement of coarse particle content Under the following measurement conditions, the content of particles having a particle diameter of 1 μm or more and particles having a particle diameter of 3 μm or more in the aluminum oxide particles was measured.
Measuring instrument: “Accurizer 780APS” manufactured by PSS
Injection Loop Volume: 1mL
Flow Rate: 60mL / min
Data Collection Time: 60sec
Number Channels: 128

(4) to measure the particle diameter of the secondary particles (D _10, D ₅₀ and D ₉₀₎ measured following measurement conditions of the particle diameter of the secondary particles. Note that the D _10, D ₅₀ and D _90, 10% cumulative particle size distribution from small diameter (volume basis), respectively, a particle diameter at 50% and 90%, of which, the D ₅₀ The volume-median particle diameter is used.
Measuring device: Laser diffraction / scattering particle size distribution measuring apparatus LA920 manufactured by Horiba, Ltd.
Circulation strength: 4
Ultrasonic intensity: 4

(5) Content of α-alumina in aluminum oxide particles 20 g of the polishing composition prepared by the above method was dried at 105 ° C. for 5 hours to obtain a powder. And about the obtained powder, the peak area of 104 surface was measured on the conditions of tube voltage 40kW and tube current 120mA with the X-ray-diffraction apparatus (the product made by Rigaku Corporation, model number: RINT2500VPC), and the alumina made from Showa Denko was measured similarly. It calculated | required by calculating like the following formula from the peak area of particle | grains WA-1000.
α-alumina content (% by weight) = (peak area of test sample) ÷ (peak area of WA-1000) × 100

  As shown in Table 2 above, when the polishing liquid compositions of Examples 1 to 11 were used, the piercing of abrasive grains to the substrate was significantly reduced as compared with the polishing liquid compositions of Comparative Examples 1 to 9, and It can be seen that the surface contamination of the substrate to be polished is significantly reduced.

  By using the present invention, for example, a hard disk substrate suitable for high recording density can be provided.

Claims (6)

A polishing liquid composition for a hard disk substrate containing aluminum oxide particles, an organic nitrogen compound, and water,
The volume-median particle diameter of the secondary particles of the aluminum oxide particles is 0.1 to 0.7 μm,
The content of particles having a particle diameter of 1 μm or more in the aluminum oxide particles is 0.2% by weight or less,
The said organic nitrogen compound is a polishing liquid composition for hard disk substrates which is an organic nitrogen compound which has a 2 or more amino group and / or imino group in a molecule | numerator. The polishing composition for a hard disk substrate according to claim 1, wherein the aluminum oxide particles contain α-alumina particles, and the α-alumina particles are 20% by weight or more of the whole aluminum oxide particles. The polishing liquid composition for hard disk substrates according to claim 1 or 2, wherein the organic nitrogen compound has a number average molecular weight of 150 to 100,000. The polishing liquid composition for hard disk substrates as described in any one of Claim 1 to 3 whose content of the said organic nitrogen compound is 0.001-0.5 weight%. The polishing composition for a hard disk substrate according to any one of claims 1 to 4, wherein the pH is less than 7. A method for producing a hard disk substrate, comprising a step of polishing a substrate to be polished using the polishing composition for a hard disk substrate according to any one of claims 1 to 5.