JP2015071660A - Polishing composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polishing composition which is also suitable for polishing using a polishing pad having a foam polyurethane-made polishing surface.SOLUTION: A polishing composition comprises abrasive grains and water. Taking the average secondary particle size of abrasive grains in the composition as Dand the average secondary particle size of abrasive grains in a mixed solution comprising a test solution A of an electric conductivity of 10 μS/cm prepared by using a water extraction solution of the polishing surface after dressing of a polishing pad having a foam polyurethane-made polishing surface and the polishing composition in a volume ratio of 1:1 as D, the average secondary particle size change rate P, calculated by the equation P[%]=|D-D|/D×100, is 10% or smaller.

Description

  The present invention relates to a polishing composition used for polishing an object to be polished.

  A process for manufacturing a substrate that requires a highly accurate surface, such as a magnetic disk substrate or a semiconductor substrate (for example, a silicon wafer), generally includes a step of polishing an object to be polished using a polishing pad. Such a polishing step is usually performed by supplying a polishing composition (polishing slurry) containing abrasive grains and water to the object to be polished. A typical polishing pad has a surface (polishing surface) made of foamed resin. As a typical foamed resin, foamed polyurethane formed by a wet film forming method can be given. Patent Documents 1 to 3 are listed as technical documents related to the polishing pad.

JP 2003-94323 A JP 2005-59184 A JP 2011-73111 A

  In Patent Documents 1 to 3, it is pointed out that, in polishing using a polishing pad having a polishing surface made of a foamed resin, an eluate from the polishing pad can adversely affect the polishing process by mixing in the polishing slurry. . For this problem, Patent Documents 1 and 3 propose countermeasures based on the composition of the polishing pad or the manufacturing method of the polishing pad. However, the countermeasures described in Patent Documents 1 and 3 have the inconvenience that the types of polishing pads that can be selected are restricted for the polishing pad user. In Patent Document 2, it is proposed that the polishing of the product is started after the dummy polishing is performed in advance after sufficiently discharging the eluate. However, since this measure requires an extra step of performing the dummy polishing, The production efficiency is reduced.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a polishing composition that can be preferably applied to polishing using a polishing pad having a polishing surface made of polyurethane foam.

According to this specification, a polishing composition containing abrasive grains and water is provided. In the polishing composition, the average secondary particle diameter of the abrasive grains in the polishing composition is D _m0 , and the volume ratio of the test solution A having an electric conductivity of 10 μS / cm and the polishing composition is 1: The average secondary particle diameter of the abrasive grains in the mixed liquid 1 is D _mA , and the following formula:
P _A [%] = | D _mA −D _m0 | / D _m0 × 100;
Average secondary particle diameter change ratio P _A calculated by 10% or less. Here, the test solution A is prepared using a water extract of the polishing surface after dressing a polishing pad having a polishing surface made of polyurethane foam. According to such a polishing composition, even if an eluate from the polishing pad is mixed, the influence of the polishing composition on the quality of the surface after polishing can be effectively suppressed. The polishing composition can have a pH of, for example, 4 or less.

Further, the matter disclosed by this specification includes a polishing composition containing abrasive grains and water, wherein the average secondary particle diameter of the abrasive grains in the polishing composition is D _m0 , the average secondary particle diameter of the abrasive grains in the mixed solution obtained by mixing test solution B and the above polishing composition at a predetermined ratio comprising a nonionic surfactant as D _mB, the following formula:
P _B [%] = | D _mB −D _m0 | / D _m0 × 100;
The polishing composition in which the average secondary particle diameter change rate P _B calculated by the above is suppressed to a predetermined level or less is included. According to such a polishing composition, even if an eluate from the polishing pad is mixed, the influence of the polishing composition on the quality of the surface after polishing can be effectively suppressed.

The polishing composition disclosed herein preferably has an ionic strength of 0.150 mol / L or less at a concentration at which the abrasive grain content is 6% by weight. Suppressing the ionic strength below 0.150 mol / L, the average secondary particle diameter change rate (hereinafter, simply referred to as "particle diameter change ratio".) In terms of one or both of P _A and P _B smaller Can be advantageous.

The polishing composition disclosed herein preferably contains an anionic surfactant. Be contained anionic surfactant in the polishing composition may be advantageous in order to further reduce the one or both of the particle diameter change ratio P _A and P _B.

  The polishing composition disclosed herein preferably contains colloidal silica as the abrasive grains. In the polishing composition containing colloidal silica abrasive grains, it is particularly meaningful to apply the technique disclosed herein.

The polishing composition disclosed herein preferably has an average secondary particle size D _m0 of 10 nm to 70 nm. In the polishing composition having an average secondary particle diameter D _m0 in the range of 10 nm to 70 nm, it is particularly meaningful to apply the technique disclosed herein.

  A preferable polishing object by any of the polishing compositions disclosed herein includes a disk substrate on which nickel phosphorus plating has been applied. Such a disk substrate (Ni-P substrate) is usually finished to a highly accurate surface by performing at least primary polishing and final polishing (finish polishing). The polishing composition disclosed herein is suitable for use in, for example, further polishing a Ni-P substrate that has finished primary polishing.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

<Abrasive grains>
The material and properties of the abrasive grains disclosed herein are not particularly limited, and can be appropriately selected according to the purpose of use and usage of the polishing composition.
Preferable examples of the abrasive grains include silica abrasive grains such as colloidal silica abrasive grains, fumed silica abrasive grains, and precipitated silica abrasive grains. The abrasive grains may be abrasive grains made of a material other than silica (hereinafter also referred to as non-silica abrasive grains). Specific examples of non-silica abrasive grains include metal oxide abrasive grains such as alumina abrasive grains, titania abrasive grains, zirconia abrasive grains, and ceria abrasive grains, and resin abrasive grains such as polyacrylic acid. These can be used individually by 1 type or in mixture of 2 or more types. Of these, silica abrasive grains are preferable, and colloidal silica abrasive grains and fumed silica abrasive grains are particularly preferable.

The average primary particle diameter of the abrasive grains is typically 5 nm or more, preferably 10 nm or more. By increasing the average primary particle size, a higher polishing rate can be realized.
The upper limit of the average primary particle diameter of the abrasive grains is not particularly limited. From the viewpoint of obtaining a more smooth surface, the average primary particle size is typically 300 nm or less, preferably 100 nm or less, more preferably 60 nm or less, and even more preferably 50 nm or less. For example, in a polishing composition intended for polishing a Ni-P substrate that has been subjected to primary polishing, abrasive grains having the above average primary particle diameter can be preferably employed.

The average primary particle diameter of the abrasive grains can be calculated, for example, from the specific surface area S (m ² / g) measured by the BET method according to the equation of average primary particle diameter (nm) = 2727 / S. The measurement of the specific surface area of the abrasive grains can be performed using, for example, a surface area measuring device manufactured by Micromeritex Co., Ltd., trade name “Flow Sorb II 2300”.

The average secondary particle diameter D _m0 of the abrasive grains in the polishing composition disclosed herein is typically 10 nm or more, usually more than 20 nm, preferably more than 30 nm, more preferably more than 40 nm, still more preferably Is greater than 50 nm. By increasing the average secondary particle diameter D _m0 , a higher polishing rate can be realized.
The upper limit of the average secondary particle diameter D _m0 of the abrasive grains is not particularly limited. From the viewpoint of avoiding that one or both of the particle diameter change ratio P _A and P _B becomes too large, the average secondary particle diameter D _m0 is preferably 1μm or less, more preferably 500nm or less. From the viewpoint of obtaining a more smooth surface, the average secondary particle diameter D _m0 is preferably 350 nm or less, preferably 200 nm or less, more preferably 150 nm or less, still more preferably 110 nm or less, and particularly preferably 70 nm or less. Furthermore, from the viewpoint of obtaining a high-quality surface, the average secondary particle diameter D _m0 may be 55 nm or less, or 40 nm or less.

Here, the average secondary particle diameter D _m0 of the abrasive grains means a volume-based mean particle diameter in a particle size distribution measured by an ultrasonic method using the polishing composition as a measurement sample. The average secondary particle size D _m0 can be measured using, for example, an ultrasonic particle size distribution / zeta potential measuring device (trade name “DT-1200”) manufactured by Nippon Luft. As the measurement sample, a polishing composition having a concentration of 6% by weight of abrasive grains may be used. When the abrasive content of the target polishing composition is different from 6% by weight, a polishing composition in which the abrasive content is adjusted to 6% by increasing or decreasing the amount of water is used as a measurement sample. The average secondary particle diameter D _m0 may be measured by using. That is, it is preferable that the polishing composition disclosed herein exhibits the above average secondary particle diameter D _m0 at an abrasive content of 6% by weight.

The content of abrasive grains in the polishing composition is not particularly limited. That is, the abrasive concentration of the polishing composition is not limited to 6% by weight, and may be a concentration different from 6% by weight.
The abrasive concentration of the polishing composition can be, for example, 30% by weight or less, usually 20% by weight or less, more preferably 15% by weight or less, and still more preferably 10% by weight or less.
The abrasive concentration of the polishing composition is preferably 1% by weight or more, more preferably 3% by weight or more. If the abrasive concentration is too low, the physical polishing action becomes small and the polishing rate decreases, which may be undesirable in practice.
The abrasive concentration can be preferably applied to the abrasive concentration of the polishing liquid supplied to the object to be polished.

<Water>
The polishing composition disclosed herein contains water in addition to the abrasive grains. As water, ion exchange water (deionized water), distilled water, pure water, or the like can be used.

<Acid or salt>
The polishing composition disclosed herein preferably contains an acid or salt as a polishing accelerator in addition to the abrasive grains and water. Here, including an acid or a salt refers to including at least one of an acid and a salt, an embodiment including an acid and no salt, an embodiment including a salt and no acid, and an embodiment including both an acid and a salt It is the meaning which includes any of these.

Examples of the acid include, but are not limited to, inorganic acids and organic acids (for example, organic carboxylic acids having 1 to 10 carbon atoms, organic phosphonic acids, organic sulfonic acids, etc.). An acid can be used individually by 1 type or in combination of 2 or more types.
Specific examples of the inorganic acid include nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, hypophosphorous acid, phosphonic acid, boric acid, hydrofluoric 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, 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, methylene succinic acid, gallic acid, ascorbic acid, nitroacetic acid, oxaloacetic acid, glycine, alanine, glutamic acid , Aspartic acid, nicotinic acid, picoline , 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-methylphosphono Examples include succinic acid, aminopoly (methylenephosphonic acid), methanesulfonic acid, ethanesulfonic acid, aminoethanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid, and 2-naphthalenesulfonic acid.

When an acid is contained in the polishing composition, the content is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. If the acid content is too small, the polishing rate decreases, which may be undesirable in practice.
Moreover, when an acid is contained in polishing composition, it is preferable that the content is 10 weight% or less, More preferably, it is 5 weight% or less. When there is too much content of an acid, the surface precision of a grinding | polishing target object will worsen, and it may be unpractically preferable.

  Examples of the salts include metal salts such as lithium salts, sodium salts and potassium salts of the inorganic acids or organic acids described above, such as alkali metal salts; ammonium salts such as quaternary salts such as tetramethylammonium salts and tetraethylammonium salts. And ammonium salts; alkanolamine salts such as monoethanolamine salts, diethanolamine salts, and triethanolamine salts; Specific examples of the salt include tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, trisodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate and the like, and alkali metal phosphates and alkaline metal warehouses. Hydrogen phosphate salt; alkali metal salt of organic acid exemplified above; other alkali metal salt of glutamic acid diacetic acid, alkali metal salt of diethylenetriaminepentaacetic acid, alkali metal salt of hydroxyethylethylenediaminetriacetic acid, triethylenetetramine hexaacetic acid Alkali metal salts; and the like. The alkali metal in these alkali metal salts can be, for example, lithium, sodium, potassium, and the like. For example, tetrasodium L-glutamate diacetate can be preferably used. A salt can be used individually by 1 type or in combination of 2 or more types.

When the polishing composition contains a salt, the content is preferably 0.1% by weight or more, more preferably 0.5% by weight or more. If the acid content is too small, the polishing rate decreases, which may be undesirable in practice.
When the polishing composition contains an acid, the content is preferably 10% by weight or less, more preferably 7% by weight or less, and further preferably 5% by weight or less. When there is too much content of an acid, the surface precision of a grinding | polishing target object will worsen, and it may be unpractically preferable.

  Such an acid or salt can typically act effectively as a polishing accelerator when used in combination with an oxidizing agent described later. Preferred acids from the viewpoint of polishing efficiency include methanesulfonic acid, sulfuric acid, nitric acid, phosphoric acid, phytic acid, 1-hydroxyethylidene-1,1-diphosphonic acid and the like. Of these, methanesulfonic acid, citric acid, and phosphoric acid are preferable acids. Preferred salts from the viewpoint of polishing efficiency include phosphates and hydrogen phosphates, alkali metal salts of glutamic acid diacetic acid, alkali metal salts of diethylenetriaminepentaacetic acid, alkali metal salts of hydroxyethylethylenediaminetriacetic acid, and triethylenetetraminehexaacetic acid. Examples include alkali metal salts.

<Oxidizing agent>
The polishing composition disclosed herein preferably contains an oxidizing agent as a polishing accelerator in addition to the abrasive grains and water.

  Examples of the oxidizing agent include peroxide, nitric acid or a salt thereof, peroxo acid or a salt thereof, permanganic acid or a salt thereof, chromic acid or a salt thereof, oxygen acid or a salt thereof, metal salt, sulfuric acid, and the like. However, it is not limited to these. An oxidizing agent can be used individually by 1 type or in combination of 2 or more types. Specific examples of the oxidizing agent include hydrogen peroxide, sodium peroxide, barium peroxide, nitric acid, iron nitrate, aluminum nitrate, ammonium nitrate, peroxodisulfuric acid, ammonium peroxodisulfate, peroxodisulfate metal salt, peroxophosphoric acid, peroxosulfuric acid. , Sodium peroxoborate, performic acid, peracetic acid, perbenzoic acid, perphthalic acid, hypobromite, hypoiodous acid, chloric acid, bromic acid, iodic acid, periodic acid, perchloric acid, hypochlorous acid Examples thereof include acid, sodium hypochlorite, calcium hypochlorite, potassium permanganate, metal chromate, metal dichromate, iron chloride, iron sulfate, iron citrate, and iron iron sulfate. Preferable oxidizing agents include hydrogen peroxide, iron nitrate, peroxodisulfuric acid and nitric acid. It preferably contains at least hydrogen peroxide, and more preferably consists of hydrogen peroxide.

When the polishing composition contains an oxidizing agent, the content thereof is preferably 0.1% by weight or more, more preferably 0.3% by weight or more, and further preferably 0.5% by weight or more. It is 0.6% by weight or more. If the content of the oxidizing agent is too small, the rate of oxidizing the object to be polished becomes slow and the polishing rate is lowered, which may be undesirable in practice.
Moreover, when an oxidizing agent is included in polishing composition, it is preferable that the content is 3 weight% or less, More preferably, it is 1.5 weight% or less. When there is too much content of an oxidizing agent, the surface precision of a grinding | polishing target object will worsen, and it may be unpreferable practically.

<Basic compound>
The polishing composition disclosed herein can contain a basic compound. Here, the basic compound refers to a compound having a function of increasing the pH of the composition when added to the polishing composition. Examples thereof include alkali metal hydroxides, carbonates and hydrogencarbonates, quaternary ammonium or salts thereof, ammonia, amines, phosphates and hydrogenphosphates, and organic acid salts. A basic compound can be used individually by 1 type or in combination of 2 or more types.

Specific examples of the alkali metal hydroxide include potassium hydroxide and sodium hydroxide.
Specific examples of the carbonate or bicarbonate include ammonium bicarbonate, ammonium carbonate, potassium bicarbonate, potassium carbonate, sodium bicarbonate, sodium carbonate and the like.
Specific examples of the quaternary ammonium or a salt thereof include quaternary ammonium hydroxide such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide.
Specific examples of amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, monoethanolamine, N- (β-aminoethyl) ethanolamine, hexamethylenediamine, diethylenetriamine, triethylenetetramine, 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 are mentioned.

<Particle diameter change rate _P A>
In a preferred embodiment of the polishing composition disclosed herein, average secondary particles of abrasive grains in a mixed solution of test liquid A having an electric conductivity of 10 μS / cm and the polishing composition in a volume ratio of 1: 1. From the diameter D _mA and the average secondary particle diameter D _{m0 of} the abrasive grains described above, the following formula:
P _A [%] = | D _mA −D _m0 | / D _m0 × 100;
Average secondary particle diameter change ratio P _A calculated by 10% or less. Here, the test liquid A is prepared using the water extract of the polishing surface after dressing a polishing pad having a polishing surface made of polyurethane foam.

The test solution A can be obtained, for example, by the following procedure. That is, a polishing pad having a foamed polyurethane produced by a wet film forming method using a nonionic surfactant on a polishing surface is prepared. The polishing pad is fixed to a surface plate of a polishing machine, and a general dressing process is performed. For example, diamond dressing is performed by scraping the surface layer of the polishing pad using a pad conditioner (also referred to as a pad dresser) in which diamond powder is fixed to the surface of a base material made of metal such as aluminum by electrodeposition or sintering. Diamond dressing typically involves scraping the surface layer of the polishing pad to a depth of 2 μm or more, or until the foamed portion (bubbles) of the polishing pad appears on the surface with an average opening diameter of 2 μm or more, usually 5 μm or more. It is done like scraping. At this time, for example, water may be supplied at a rate of about 1 to 1.5 L / min.
Next, the surface of the polishing pad is cleaned while supplying cleaning water at an appropriate rate, and the drainage is collected. The electrical conductivity of the obtained waste water is measured, and when the electrical conductivity is lower than 10 μS / cm, the water supply rate is reduced to obtain waste water (test solution A) having an electrical conductivity of 10 μS / cm. To be able to. When the electrical conductivity of the obtained waste water is higher than 10 μS / cm, the test liquid A is obtained by adjusting the electrical conductivity to 10 μS / cm by adding an appropriate amount of water to the waste water for dilution. Alternatively, the water supply rate may be increased to obtain drainage (test solution A) having an electric conductivity of 10 μS / cm.
The electric conductivity can be measured by a conventional method. For the measurement, for example, a conductivity meter (model “DS-12”, working electrode “3552-10D”) manufactured by HORIBA, Ltd. can be used.
As the water for washing, ion exchange water, distilled water, pure water or the like can be used.

Average secondary particle diameter change ratio P _A is the test solution A and the polishing composition and the volume ratio of 1: through cohesion resistance test to be mixed with 1, the volume ratio of 1: abrasive grains in a mixture of 1 It can be calculated from the average secondary particle diameter D _mA and the average secondary particle diameter D _m0 of the abrasive grains in the polishing composition before mixing.

The operation of mixing the polishing composition and the test liquid A at a volume ratio of 1: 1 is preferably performed under the condition that these liquid temperatures are in the range of about 20 ° C to 28 ° C. The mixing operation can be preferably carried out by adding the test liquid A while stirring the polishing composition in the container and subsequently stirring the mixed liquid. It is preferable that the time from the start of adding the test solution A to the polishing composition to the completion of the addition be within 30 seconds. The measurement of the average secondary particle diameter D _mA of the abrasive grains in the mixed liquid is preferably performed within about 10 minutes by continuing the stirring after the addition of the test liquid A is completed. For example, it is good to use stirring as a measurement sample for 5 minutes after the addition of the test liquid A is completed and stirring is continued.

Here, the average secondary particle diameter D _mA of the abrasive grains in the mixed liquid means a volume-based mean particle diameter in a particle size distribution measured by an ultrasonic method using the mixed liquid as a measurement sample. . The average secondary particle diameter D _mA can be measured using, for example, an ultrasonic particle size distribution / zeta potential measuring device (trade name “DT-1200”) manufactured by Nippon Luft. For the measurement of the average secondary particle diameter D _mA , it is desirable to use the same apparatus as the measurement of the average secondary particle diameter D _m0 .

The average abrasive grain of the secondary particle diameter D _m0 in the polishing composition and an average secondary particle diameter D _mA abrasive by substituting the above equation in the mixed solution, the particle diameter change ratio P _A Can be calculated.

Average secondary particle diameter change ratio P _A lower polishing composition, component (pad outflow component) polishing composition flowing out from the polishing pad during polishing using the polishing pad having a polishing surface made of expanded polyurethane Even if mixed in, the dispersion state of the abrasive grains in the polishing composition is unlikely to fluctuate. According to such a polishing composition, an event in which abrasive grains agglomerate and coarse particles (LPC) are generated due to mixing of a pad outflow component can be effectively suppressed.

In the production of foamed polyurethane (typically, foamed polyurethane produced by a wet film-forming method), a surfactant can be used for the purpose of a foaming agent, a foaming aid, a foam stabilizer, a film-forming aid, and the like. . Accordingly, the pad outflow component may include a surfactant used in the process of manufacturing the foamed polyurethane.
Examples of the surfactant that can be contained in the pad spill component include oxyalkylene polymers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; polyoxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, Polyoxyalkylene adducts such as polyoxyethylene fatty acid esters, polyoxyethylene glyceryl ether fatty acid esters, polyoxyethylene sorbitan fatty acid esters, glycerin ethylene oxide polyoxide compounds; copolymers of multiple types of oxyalkylene (diblock type, triblock) Type, random type, alternating type); and the like. Another example of the surfactant that can be contained in the pad outflow component is a silicone-based surfactant. Representative examples of silicone surfactants include polyether-modified silicones such as polyoxyalkylene / dimethylsiloxane copolymers and polyoxyalkylene alkyl ether / dimethylsiloxane copolymers. The foamed polyurethane constituting the polished surface can contain one kind of such a surfactant alone or in combination of two or more kinds. The usage-amount of surfactant may be comparable with the normal usage-amount in manufacture of the foaming polyurethane for polishing pads (typically soft foaming polyurethane).

  The fact that the dispersed state of the abrasive grains is not easily affected by the component flowing out of the pad means that the composition of the polishing surface of the polishing pad to be used (for example, a foaming agent, foaming aid, Type and amount used of foaming agent), conditions for adjusting the polishing surface (for example, whether or not a treatment for reducing spillage has been performed in advance, such as dummy polishing or cleaning with jet water), use state of the polishing pad ( This is also preferable from the standpoint of suppressing fluctuations in polishing quality due to polishing time from the start of polishing, abrasion state of the polished surface, and the like.

Polishing composition disclosed herein, it preferably has the particle diameter change ratio P _A is less than 10%, more preferably 7% or less, is 5% or less (e.g., less than 4%) Further preferred. As particle diameter change ratio P _A is smaller polishing composition, less likely to be affected by contamination of the pad outflow components. Therefore, it can be said that there is little variation in the dispersion state of the abrasive grains during polishing. The lower limit of the particle diameter change ratio P _A is theoretically 0%.

The agglomeration resistance test can be preferably performed using, for example, a polishing composition having a concentration of 6% by weight of abrasive grains. When the abrasive content of the target polishing composition is different from 6% by weight, the polishing composition and the test liquid A were adjusted to 6% by weight by increasing or decreasing the amount of water. Is preferably mixed at a volume ratio of 1: 1 to conduct a cohesion resistance test. That is, the polishing compositions disclosed herein, it is preferable to satisfy the above-mentioned particle diameter change ratio P _A in abrasive content 6 wt%.

<Ionic strength>
Although not particularly limited, the polishing composition according to a preferred embodiment may have an ionic strength of 0.150 mol / L or less at a concentration at which the abrasive grain content is 6% by weight. The polishing composition ionic strength is less than 0.150 mol / L is preferred because tends to show a preferred particle diameter change rate P _A described above. From this viewpoint, a polishing composition having an ionic strength of less than 0.135 is more preferable. The lower limit of the ionic strength is not particularly limited as long as the polishing composition can be adjusted to a desired pH. From the viewpoint of improving the polishing rate, usually, the ionic strength is preferably 0.01 mol / L or more, more preferably 0.02 mol / L or more, and further preferably 0.03 mol / L or more. preferable.

  In this specification, the ionic strength is a value calculated by the following formula (1) for all ions in the polishing composition at a concentration at which the abrasive grain content of the polishing composition is 6% by weight. Say. When the abrasive content of the target polishing composition is different from 6% by weight, the ion for the polishing composition when the concentration is adjusted to 6% by weight by increasing or decreasing the amount of water. Calculate the intensity.

Here, I in Formula (1) represents ionic strength [mol / L]. m _i represents a molar concentration [mol / L] of each ion. z _i represents the charge (valence) of each ion. The molar concentration of each ion is calculated from the ion amount (ratio) of each substance dissociated (ionized) in the pH range of the polishing composition relating to the calculation of ionic strength. For example, when the substance A contained at a concentration of 1 mol / L in the polishing composition prepared to an abrasive content of 6% by weight ionizes only 50% in the pH range, the molar concentration reflected in the ionic strength is 0.5 mol / L.

Each of the substances dissociated in the pH range of the polishing composition related to the calculation of the ionic strength (that is, the polishing composition whose concentration is adjusted as necessary so that the abrasive content is 6% by weight). The ion amount (ratio) can be determined from the dissociation constants (ionization constant, acid dissociation constant) of each substance.
For example, the acid dissociation constant of a substance AH that dissociates into A ⁻ and H ⁺ in the polishing composition is pKa, and the substance AH is contained in the polishing composition at 1.0 mol / L. When the pH of the composition is 3, the concentration _{A of} A ⁻ can be obtained by the formula (10 ^−pKa × 1.0 [mol / L]) / 1.0 × 10 ⁻³ .
When a salt is added to the polishing composition, the ionic strength is calculated from the molar concentration of the counter ion of the salt. For example, for the substance AB that dissociates into A ⁻ and B ⁺ in the polishing composition, the ionic strength is calculated separately for AH or BOH in the polishing composition.
In the polishing composition containing a substance that dissociates in one or more stages in the polishing composition, the ionic strength is determined for ions dissociated in each stage.
In addition, calculation of ionic strength shall be performed when the temperature of polishing composition is 25 degreeC.

  The ionic strength of the polishing composition can be adjusted by, for example, the type and amount (concentration) of the ionic compound contained in the composition. As the ionic compound, the above-described polishing accelerator or a compound that functions as a basic compound can be used. The ionic strength may be adjusted using ionic compounds other than these.

<Anionic surfactant>
The polishing composition disclosed herein can contain an anionic surfactant. Be contained anionic surfactant in the polishing composition may be advantageous in order to further reduce the particle diameter change ratio P _A. That is, by containing an anionic surfactant, the influence of the mixing of the pad outflow component on the dispersed state of the abrasive grains can be suppressed.

As the anionic surfactant, for example, a sulfonic acid anionic surfactant can be preferably used. The concept of the sulfonic acid anionic surfactant here includes a sulfonic acid compound and a salt thereof. Examples of the sulfonate compound include polyalkylaryl sulfonic acid compounds such as naphthalene sulfonic acid formaldehyde condensate, methyl naphthalene sulfonic acid formaldehyde condensate, anthracene sulfonic acid formaldehyde condensate, benzene sulfonic acid formaldehyde condensate; melamine sulfonic acid Melamine formalin sulfonic acid compounds such as formaldehyde condensates; lignin sulfonic acid compounds such as lignin sulfonic acid and modified lignin sulfonic acid; Aromatic amino sulfonic acid compounds such as aminoarylsulfonic acid-phenol-formaldehyde condensates; , Polyisoprene sulfonic acid, polyvinyl sulfonic acid, polyallyl sulfonic acid, polyisoamylene sulfonic acid, polystyrene sulfonic acid and the like. As a salt of such a sulfonic acid compound, an alkali metal salt such as a sodium salt or a potassium salt is preferable. Preferable examples of the sulfonic acid compound salt include naphthalenesulfonic acid formaldehyde condensate sodium salt and benzenesulfonic acid formaldehyde condensate sodium salt.
Among the sulfonic acid anionic surfactants, naphthalene sulfonic acid formaldehyde condensates such as naphthalene sulfonic acid formaldehyde condensate and methyl naphthalene sulfonic acid formaldehyde condensate and salts thereof are preferable.

Other examples of the anionic surfactant include polyacrylic acid anionic surfactants such as polyacrylic acid and salts thereof (for example, alkali metal salts such as sodium salt).
Other examples of anionic surfactants include sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, sodium polyoxyethylene alkyl ether sulfate, ammonium polyoxyethylene alkyl phenyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, etc. Is mentioned.

The polishing composition of the embodiment comprising an anionic surfactant, an anionic surfactant in the case where the particle diameter change ratio P _A, from the viewpoint of suppressing P _B, was converted to a concentration content of the abrasive grains is 6 wt% It is appropriate that the content of the active agent is, for example, 0.001% by weight or more. The content is preferably 0.005% by weight or more, more preferably 0.01% by weight or more, and further preferably 0.02% by weight or more from the viewpoint of the smoothness of the surface after polishing. Further, from the viewpoint of polishing rate and the like, the content is suitably 10% by weight or less, preferably 5% by weight or less, for example 1% by weight or less.

<Other ingredients>
The polishing composition disclosed herein is a polishing composition (typically a magnetic material such as a Ni-P substrate) such as a chelating agent or a preservative as long as the effects of the present invention are not significantly hindered. A known additive that can be used in a polishing composition used for polishing a disk substrate may be further contained as necessary.

  Examples of chelating agents include aminocarboxylic acid chelating agents and organic phosphonic acid chelating agents. Examples of aminocarboxylic acid chelating agents include ethylenediaminetetraacetic acid, ethylenediaminetetraacetic acid sodium, nitrilotriacetic acid, nitrilotriacetic acid sodium, nitrilotriacetic acid ammonium, hydroxyethylethylenediaminetriacetic acid, hydroxyethylethylenediamine sodium triacetate, diethylenetriaminepentaacetic acid Diethylenetriamine sodium pentaacetate, triethylenetetramine hexaacetic acid and sodium triethylenetetramine hexaacetate. 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-methylphospho Nosuccinic acid is included. Of these, organic phosphonic acid-based chelating agents are more preferable, and ethylenediaminetetrakis (methylenephosphonic acid) and diethylenetriaminepenta (methylenephosphonic acid) are particularly preferable. A particularly preferred chelating agent is ethylenediaminetetrakis (methylenephosphonic acid).

<Particle diameter change rate P _B >
The matter disclosed in this specification is a polishing composition containing abrasive grains and water, wherein the average secondary particle diameter of the abrasive grains in the polishing composition is D _m0, and is nonionic. the average secondary particle diameter of the abrasive grains in the mixed solution obtained by mixing test solution B and the above polishing composition at a predetermined ratio comprising a surfactant as D _mB, the following formula:
P _B [%] = | D _mB −D _m0 | / D _m0 × 100;
The polishing composition in which the average secondary particle diameter change rate P _B calculated by the above is suppressed to a predetermined level or less is included. According to the polishing composition in which the particle diameter change rate P _B is suppressed to a predetermined level or less, even if the eluate from the polishing pad is mixed, it effectively affects the quality of the surface after polishing. Can be suppressed.

The particle size change rate P _B can be obtained in the same manner as the particle size change rate PA described above except that the test solution B is used instead of the test solution _A. Here, as the test solution B, an aqueous solution of a nonionic surfactant can be used. Moreover, when the water extract of the polishing surface described above contains a nonionic surfactant, the water extract may be used as it is, or after appropriately diluted or concentrated, as the test solution B.
The mixing ratio of the polishing composition and the test liquid B is not particularly limited, but it is usually appropriate that the volume ratio is about 100: 1 to 1: 2, for example, the volume ratio is about 1: 1. Can do.

In a preferred embodiment of the technology disclosed herein, an aqueous solution of a nonionic surfactant is used as the test solution B. As such a test solution B, for example, a commercially available nonionic surfactant can be preferably used as it is, or appropriately prepared by diluting with water or concentrating. As the nonionic surfactant, for example, a glycerin ethylene oxide polyoxide compound can be used.
The present inventor indicated that the polishing composition having a low particle diameter change rate P _B is a component in which the component flowing out from the polishing pad during polishing using a polishing pad having a polishing surface made of polyurethane foam (pad outflow component) is for polishing. It has been found that the dispersion state of the abrasive grains in the polishing composition is less likely to fluctuate even if mixed in the composition. This suggests that the nonionic surfactant contained in the pad outflow component is one factor in the variation of the dispersed state of the abrasive grains due to the pad outflow component. For this reason, by using the test liquid B instead of the test liquid A, it is possible to easily grasp the stability of the dispersed state of the abrasive grains with respect to the pad outflow component.

The polishing composition disclosed herein preferably has a particle diameter change rate P _B of less than 10%, more preferably 5% or less, and less than 5% (for example, 4% or less). Further preferred. It can be said that the smaller the particle diameter change rate P _B is, the less the influence of the pad outflow component is. Therefore, it can be said that there is little variation in the dispersion state of the abrasive grains during polishing. The lower limit of the particle diameter change rate P _B is theoretically 0%.

<Application>
As described above, the polishing composition disclosed herein utilizes various characteristics of the polishing pad having a polishing surface made of polyurethane foam, taking advantage of the fact that there is little variation in the state of abrasive grain dispersion during polishing. It can be preferably applied to the use of polishing. The polishing pad having a foamed polyurethane polishing surface is not particularly limited as long as it has at least the foamed polyurethane on the polishing surface. For example, the polishing pad is entirely made of foamed polyurethane, and the foamed polyurethane layer is a nonwoven fabric. It can be a polishing pad supported by a pad base material such as.
Further, the polishing composition disclosed herein can be applied to a polishing process in which a polishing pad having a polishing surface made of polyurethane foam is not used because the dispersion state of abrasive grains hardly changes during polishing. . For example, it can be used in a polishing process using a polishing pad having a foamed resin other than polyurethane foam on the polishing surface.

  The polishing object (object to be polished) of the polishing composition disclosed herein is not particularly limited. The polishing composition is preferably used for polishing various objects requiring a highly accurate surface such as a magnetic disk substrate, a semiconductor substrate such as a silicon wafer, and an optical material such as a lens and a reflection mirror. obtain. For example, it can be preferably applied to polishing of a magnetic disk substrate (Ni-P substrate) having a nickel phosphorus plating layer on the surface of a base disk. The base disk can be made of, for example, aluminum alloy, glass, glassy carbon, or the like. A disk substrate provided with a metal layer or metal compound layer other than the nickel phosphorus plating layer on the surface of such a base disk may be used. Among these, it is suitable as a polishing composition for polishing a Ni-P substrate having a nickel phosphorus plating layer on a base disk made of aluminum alloy. In such applications, it is particularly meaningful to apply the technology disclosed herein.

  In addition, the polishing composition disclosed herein is, for example, Schmitt Measurement System Inc. Surface roughness (arithmetic mean roughness (Ra)) measured by a laser scanning surface roughness meter “TMS-3000WRC” manufactured by the company is primarily polished to a surface roughness of 10 mm or less. It is suitable for applications such as adjusting to (arithmetic average roughness (Ra)) and applications for further polishing (secondary polishing or final polishing) of a magnetic disk substrate that has undergone primary polishing. In particular, it is particularly meaningful to apply the technique disclosed herein in applications where the magnetic disk substrate is subjected to secondary polishing or finish polishing.

  The polishing composition disclosed herein is typically supplied to an object to be polished (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 a polishing composition. Or you may use polishing composition as polishing liquid as it is. That is, the concept of the polishing composition in the technique disclosed herein includes both a polishing liquid (working slurry) supplied to the object to be polished and a concentrated liquid that is diluted and used as the polishing liquid. .

  The polishing composition disclosed herein may be in a concentrated form (concentrated liquid form) before being supplied to the object to be polished. Such a polishing composition in the form of a concentrated solution is advantageous from the viewpoints of convenience, cost reduction, etc. during production, distribution, storage and the like. The concentration factor can be set to about 1.5 to 50 times, for example. From the viewpoint of the storage stability of the concentrate, a concentration factor of about 2 to 20 times (typically 2 to 10 times) is usually appropriate.

  Thus, the polishing composition in the form of a concentrated liquid can be suitably used in such a manner that a polishing liquid is prepared by diluting at a desired timing and the polishing liquid is supplied to an object to be polished. The dilution can be typically performed by adding and mixing the above-mentioned aqueous solvent to the concentrated solution. Further, when the aqueous solvent is a mixed solvent, only a part of the components of the aqueous solvent may be added, and a mixed solvent containing these components at a different ratio from the aqueous solvent is added. May be diluted.

  The pH of the polishing composition is not particularly limited. For example, from the viewpoint of polishing rate, surface smoothness, etc., pH 4 or less is preferable, and pH 3 or less is more preferable. If necessary, a pH adjusting agent such as an organic acid or an inorganic acid can be contained so that the above pH is realized in the polishing liquid. The pH can be preferably applied to, for example, a polishing liquid used for polishing Ni—P.

  The polishing composition disclosed herein may be a one-part type or a multi-part type including a two-part type. For example, the liquid A containing a part of the constituent components (typically components other than the aqueous solvent) of the polishing composition and the liquid B containing the remaining components are mixed to prepare the polishing object. You may be comprised so that it may be used for grinding | polishing.

<Polishing>
The polishing composition disclosed herein can be suitably used for polishing an object to be polished, for example, in an embodiment including the following operations. Hereinafter, a preferred embodiment of a method for polishing an object to be polished using the polishing composition disclosed herein will be described.
That is, a polishing liquid (typically a slurry-like polishing liquid, sometimes referred to as a polishing slurry) containing any of the polishing compositions disclosed herein is prepared. Preparing the polishing liquid may include preparing a polishing liquid by adding an operation such as concentration adjustment (for example, dilution) to the polishing composition. Or you may use polishing composition as polishing liquid as it is.

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

  The polishing step as described above may be a part of a manufacturing process of a substrate (for example, a magnetic disk substrate such as a Ni-P substrate). Therefore, according to this specification, the manufacturing method of the board | substrate including the said grinding | polishing process is provided.

  Several examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the examples. In the following description, “parts” and “%” are based on weight unless otherwise specified.

<Example 1>
Abrasive grains, citric acid, tetrasodium L-glutamate diacetate (GLDA-4Na), 31% hydrogen peroxide solution, anionic surfactant and ion-exchanged water were mixed to obtain an abrasive concentration of 6%, hydrogen peroxide ( A polishing composition having an H ₂ O ₂ ) concentration of 0.6%, an anionic surfactant concentration of 0.04%, and a pH of 2.7 was prepared. As the abrasive grains, colloidal silica having an average primary particle diameter of 23 nm was used. As an anionic surfactant, naphthalenesulfonic acid formaldehyde condensate sodium salt was used. The amounts of citric acid and GLDA-4Na used were set so that the ionic strength of the polishing composition was 0.052 mol / L.

<Example 2>
Abrasive grains, phosphoric acid, GLDA-4Na, dipotassium hydrogen phosphate, 31% hydrogen peroxide water and ion-exchanged water are mixed to obtain an abrasive grain concentration of 6% and a hydrogen peroxide (H ₂ O ₂ ) concentration of 0.6. %, PH 2.2 polishing composition was prepared. As the abrasive grains, the same ones as in Example 1 were used. The amounts of phosphoric acid, GLDA-4Na, and dipotassium hydrogen phosphate used were set so that the ionic strength of the polishing composition was 0.134 mol / L.

<Example 3>
Abrasive grains, citric acid, GLDA-4Na, 31% hydrogen peroxide solution, anionic surfactant and ion-exchanged water are mixed to obtain an abrasive concentration of 6% and hydrogen peroxide (H ₂ O ₂ ) concentration of 0.6. %, Anionic surfactant concentration 0.04%, pH 2.6 polishing composition was prepared. As the abrasive and anionic surfactant, benzenesulfonic acid formaldehyde condensate sodium salt was used. The amounts of citric acid and GLDA-4Na used were set so that the ionic strength of the polishing composition was 0.135 mol / L.

<Comparative Example 1>
Abrasive grains, phosphoric acid, dipotassium hydrogen phosphate, 31% hydrogen peroxide solution and ion-exchanged water were mixed to obtain an abrasive concentration of 6%, hydrogen peroxide (H ₂ O ₂ ) concentration of 0.6%, pH 2. A polishing composition of 0 was prepared. As the abrasive grains, the same ones as in Example 1 were used. The amounts of phosphoric acid and dipotassium hydrogen phosphate used were set so that the ionic strength of the polishing composition was 0.16 mol / L.

<Comparative Example 2>
Abrasive grains, phosphoric acid, GLDA-4Na, dipotassium hydrogen phosphate, 31% hydrogen peroxide water and ion-exchanged water are mixed to obtain an abrasive grain concentration of 6% and a hydrogen peroxide (H ₂ O ₂ ) concentration of 0.6. %, PH 2.1 polishing composition was prepared. As the abrasive grains, the same ones as in Example 1 were used. The amounts of phosphoric acid, GLDA-4Na, and dipotassium hydrogen phosphate used were set so that the ionic strength of the polishing composition was 0.267 mol / L.

<Comparative Example 3>
Except for not using an anionic surfactant, it was the same as in Example 1, and the abrasive grain concentration was 6%, the hydrogen peroxide (H ₂ O ₂ ) concentration was 0.6%, the pH was 2.7, and the ionic strength was 0.052 mol / L. A polishing composition was prepared.

<Aggregation resistance test>
[Measurement of average secondary particle diameter _Dm0 ]
Using polishing compositions according to Examples 1 to 3 and Comparative Examples 1 to 3 as measurement samples, an average was obtained using an ultrasonic particle size distribution / zeta potential measurement device (trade name “DT-1200”) manufactured by Nippon Luft. The secondary particle diameter D _m0 was measured.
[Preparation of test solution A]
A polishing pad having a foamed polyurethane produced on a polishing surface by a wet film-forming method using a nonionic surfactant was prepared. The polishing pad was fixed to a surface plate of a double-side polishing machine (“9B-5P” manufactured by Speed Fam Co., Ltd.), and diamond dressing of the polishing surface was performed while supplying ion exchange water at a rate of 1 to 1.5 L / min. Thereafter, the polishing surface was cleaned with a brush while supplying ion-exchanged water at a rate of 1 to 1.5 L / min, and the drainage was collected. The electrical conductivity of the obtained waste water was measured by a conductivity meter (model “DS-12”, used electrode “3552-10D”) manufactured by HORIBA, Ltd., and found to be 10 μS / cm. Therefore, this waste water was used as the test solution A as it was.
[Measurement of average secondary particle diameter D _mA ]
Test liquid A was added to the polishing composition according to each example at a volume ratio of 1: 1 and mixed. Stirring is continued from the completion of the addition of the test solution A, and the mixed solution after 5 minutes is used as a measurement sample, using an ultrasonic particle size distribution / zeta potential measurement device (trade name “DT-1200”) manufactured by Nippon Luft. The average secondary particle diameter D _mA was measured.
[Calculation of the average secondary particle diameter change ratio P _A]
The average secondary particle diameter D _m0 and the average secondary particle diameter D _mA obtained above are expressed by the following formula:
P _A [%] = | D _mA −D _m0 | / D _m0 × 100;
It is substituted into and calculate the average secondary particle diameter change ratio P _A. The obtained results are shown in Table 1.

<Polishing test>
The polishing composition according to each example was used as it was as a polishing liquid to polish the substrate to be polished. As a substrate to be polished, an aluminum substrate for a hard disk having a diameter of 3.5 inches (about 95 mm) and a thickness of 1.27 mm provided with an electroless nickel phosphorus plating layer on its surface, Schmitt Measurement System Inc. What was pre-polished so that the value of the surface roughness (arithmetic average roughness (Ra)) measured by a laser scanning surface roughness meter “TMS-3000WRC” manufactured by the company was 6 mm was used. The substrate to be polished was set in a double-side polishing machine in which the polishing pad used in the preparation of the test solution A was fixed to a surface plate, and was polished under the following conditions.

[Polishing conditions]
Polishing load: 120 g / cm ²
Number of substrates loaded: 2 / carrier x 4 carriers (8 total)
Lower platen rotation speed: 60rpm
Polishing liquid supply rate: 83 mL / min Polishing time: 5 minutes Rinse: ion-exchanged water (1 to 1.5 L / min)

[Scratch number evaluation]
For the polished substrate, the number of scratches was counted under the following conditions.
Measuring device: Surface inspection device “Candela OSA6100” manufactured by KLA-Tencor
Measurement range: Radius position 20-45mm
Detector channel: P-Sc (Radial & Circumferential laser)

The results are shown in Table 1 at the following two levels.
○: Number of scratches per substrate is less than 20 ×: Number of scratches per substrate is 20 or more

As shown in Table 1, in Examples 1 to 3 particle diameter change ratio P _A 10% or less, as compared with Comparative Examples 1 to 3 where the particle diameter change ratio P _A exceeds 10%, scratches Was clearly suppressed. Further, it becomes easy to suppress the particle diameter change ratio _{P A} to 10% or less by suppressing the ionic strength below 0.150 mol / L, further particle diameter variation ratio by suppressing the ionic strength to less than 0.135 mol / L it was confirmed that tends to reduce the P _a. Further, from Examples 1 and Comparative Example 3, it becomes easy to suppress the particle diameter change ratio P _A 10% or less was confirmed by incorporating an anionic surfactant.

  Specific examples of the present invention have been described in detail above, but 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 (6)

A polishing composition containing abrasive grains and water,
The average secondary particle diameter of the abrasive grains in the polishing composition is D _m0 ,
Volume ratio of test solution A having an electrical conductivity of 10 μS / cm prepared by using a water extract of the polishing surface after dressing a polishing pad having a polishing surface made of polyurethane polyurethane and the polishing composition is 1: 1. Assuming that the average secondary particle diameter of the abrasive grains in the mixed liquid is D _mA , the following formula:
P _A [%] = | D _mA −D _m0 | / D _m0 × 100;
Average secondary particle diameter change ratio P _A calculated by 10% or less, the polishing composition.   The polishing composition according to claim 1, wherein the polishing composition has an ionic strength of 0.150 mol / L or less at a concentration at which the content of the abrasive grains is 6% by weight.   Polishing composition of Claim 1 or 2 whose pH is 4 or less.   The polishing composition according to any one of claims 1 to 3, wherein the polishing composition contains an anionic surfactant. Wherein comprises a colloidal silica as abrasive grains, the average secondary particle diameter D _m0 is 10Nm～70nm, polishing composition according to any one of claims 1 to 4.   The polishing composition according to any one of claims 1 to 5, which is used for polishing a disk substrate on which nickel phosphorus plating has been applied.