JP4451347B2 - Polishing liquid composition - Google Patents

Description

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

  Recent memory hard disk drives are required to have a high capacity and a small diameter, and in order to increase the recording density, the flying height of the magnetic head is reduced to reduce the unit recording area. As a result, the surface quality required after polishing in the manufacturing process of magnetic disk substrates has become stricter year by year, and the surface roughness, micro waviness, roll-off and protrusions have been reduced in response to the low flying height of the head. Corresponding to the decrease in unit recording area, the allowable number of scratches per substrate surface is small, and its size and depth are getting smaller.

  Also in the semiconductor field, high integration and high speed are advancing. In particular, miniaturization of wiring is required for high integration. As a result, in the manufacturing process of a semiconductor substrate, the depth of focus at the time of exposure of a photoresist becomes shallow, and surface quality with fewer defects is desired.

In response to such demands, a polishing liquid composition with improved surface smoothness of the memory hard disk substrate is described in Patent Document 1, but in order to obtain the surface quality necessary for increasing the density of the memory hard disk substrate. It is insufficient.
Japanese Patent Laid-Open No. 2002-30274

  Therefore, the inventors of the present invention diligently examined the requirements for achieving the surface quality necessary for high density or high integration of precision component substrates such as memory hard disk substrates and semiconductor substrates. The present invention has been completed by finding that high density is hindered in the memory hard disk substrate and high integration is hindered in the semiconductor substrate.

  That is, an object of the present invention is to provide a polishing composition that can remarkably reduce nanoscratches of an object to be polished after polishing, and a substrate manufacturing method that remarkably reduces nanoscratches.

That is, the gist of the present invention is as follows.
[1] A polishing composition comprising two or more kinds of abrasives, wherein the zeta potential at the pH at the time of polishing is (a) an abrasive a exceeding 0 mV and (b) an abrasive b less than 0 mV A polishing composition comprising:
[2] A method for producing a substrate comprising a step of polishing using a polishing composition comprising two or more kinds of abrasives, wherein the zeta potential of the abrasives during polishing is at least one exceeding 0 mV, And at least one other type of substrate manufacturing method comprising a step of polishing at less than 0 mV, and
[3] The present invention relates to a polishing composition comprising a mixture of an abrasive material a having a zeta potential at a polishing pH of (a) greater than 0 mV and (b) an abrasive material b of less than 0 mV.

  By using the polishing composition of the present invention, for example, in a polishing step of a precision component substrate for high density or high integration, fine nano scratches can be remarkably reduced, so that high quality with excellent surface properties can be obtained. There is an effect that precision component substrates such as a memory hard disk substrate and a semiconductor substrate can be manufactured.

  The present invention is a polishing composition comprising two or more kinds of abrasives, wherein the zeta potential at the pH during polishing is (a) an abrasive a exceeding 0 mV and (b) an abrasive having less than 0 mV The present invention relates to a polishing composition comprising b. By having such a configuration, it is possible to significantly reduce nano scratches. This nano-scratch is a physical property that is important for high density or high integration especially in a memory hard disk substrate or a semiconductor substrate. Therefore, by using the polishing composition of the present invention, a high-quality memory hard disk substrate or semiconductor substrate having excellent surface properties can be produced.

  The nano scratch in the present invention is a fine scratch on the substrate surface having a depth of 10 nm or more and less than 100 nm, a width of 5 nm or more and less than 500 nm, and a length of 100 μm or more. Nano scratches are presumed to be caused by, for example, coarse particles derived from the polishing composition or the environment, or aggregates of abrasive particles generated during polishing. Nanoscratches can be detected with an atomic force microscope (AFM), and can be quantitatively evaluated as the number of nanoscratches by measurement with “MicroMax” which is a visual inspection apparatus described in Examples described later.

The abrasive used in the present invention is roughly classified into two types according to the zeta potential at the pH at the time of polishing. The abrasive having a zeta potential of more than 0 mV is designated as abrasive a, and the abrasive having a zeta potential of less than 0 mV is designated as abrasive b. .
Although the mechanism for reducing nanoscratches in the present invention is not clear, the abrasive material a and the abrasive material b having different zeta potentials at the pH during polishing, that is, different surface charges, attract each other by electrostatic attraction, and the nanoscratch This is presumed to suppress the dropping of the aggregate of abrasive particles or abrasive particles generated during polishing, which is considered to be one of the causes of scratches, to the substrate surface.
From the viewpoint of increasing electrostatic attraction and reducing nanoscratches, it is preferable that the absolute values of the zeta potentials of the abrasives a and b at the pH during polishing are large. The zeta potential of the abrasive material a at the pH during polishing is more than 0 mV, preferably 0.5 mV or more, more preferably 0.7 mV or more, and further preferably 0.8 mV or more. Moreover, from a viewpoint of making the cohesion force with the abrasive b moderate, it is preferably 50 mV or less, more preferably 20 mV or less, and further preferably 10 mV or less. The zeta potential of the abrasive b at the pH during polishing is less than 0 mV, preferably -1 mV or less, more preferably -3 mV or less, still more preferably -5 mV or less, and even more preferably -10 mV or less. Moreover, from a viewpoint of making the cohesion force with the abrasive material a moderate, Preferably it is -50 mV or more, More preferably, it is -40 mV or more, More preferably, it is -30 mV or more.
Similarly, when mixing two or more kinds of abrasives a and b for the purpose of adjusting the particle size distribution from the viewpoint of improving the polishing rate and reducing nanoscratch, the abrasive having a zeta potential of more than 0 mV at the pH during polishing is also polished. A material a1, an abrasive material a2,..., And an abrasive material whose zeta potential is less than 0 mV are an abrasive material b1, an abrasive material b2,.

  As the abrasive material a and the abrasive material b, the pH dependence of the isoelectric point and the zeta potential of the abrasive material may be examined, and those that meet the purpose may be selected. The abrasive material a can be obtained, for example, by subjecting the abrasive material to surface treatment such as adsorbing positively charged Al ions, and the abrasive material b can be obtained by, for example, a carboxyl group or sulfone having a negative charge on the abrasive material. It can be obtained by applying a surface treatment such as adsorption of a compound having an acid group.

The zeta potential in the present invention refers to the zeta potential when measured using a zeta potential measuring device Zeta Probe (Colloidal Dynamics). The measurement principle is electrokinetic Sonic Amplitude (ESA), which is a type of ultrasonic method, and there is no need to dilute the abrasive concentration as in conventional electrophoresis, and it is the same as the polishing composition. The zeta potential can be measured by concentration.
In this specification, the zeta potential of the abrasive in the polishing composition is the same as the zeta potential of the water slurry of the abrasive adjusted to the same pH as the polishing composition at the time of polishing. Refers to electric potential. The zeta potential of the polishing liquid composition refers to the zeta potential obtained by measuring the target polishing liquid composition as it is using the zeta potential measuring device. When measuring the zeta potential with the zeta potential measurement device, in order to increase the reliability of the measurement value, the measurement is repeated at least three times under the same sample and the same measurement condition, and the average value thereof is set as the zeta potential.

The average particle size of the primary particles of the abrasives a and b is preferably 1 nm or more and less than 40 nm. From the viewpoint of improving the polishing rate, the average particle size is more preferably 3 nm or more, further preferably 5 nm or more, and the nanoscratch is reduced. From this viewpoint, it is more preferably 35 nm or less, further preferably 30 nm or less, further preferably 25 nm or less, and further preferably 20 nm or less. Therefore, the average particle size of the primary particles is preferably 1 to 35 nm, more preferably 3 to 30 nm, still more preferably 5 to 25 nm, and still more preferably 5 to 20 nm from the viewpoint of economically reducing nanoscratches. Further, when the primary particles are aggregated to form secondary particles, the average particle size of the secondary particles is preferably 5 to 5 from the viewpoint of improving the polishing rate and reducing the nano scratches. It is 150 nm, More preferably, it is 5-100 nm, More preferably, it is 5-80 nm, More preferably, it is 5-50 nm, More preferably, it is 5-30 nm.
Moreover, as particle size distribution of the abrasives a and b, D90 / D50 is preferably 1 to 5, more preferably 2 to 5, and even more preferably 3 from the viewpoint of reducing nanoscratches and improving the polishing rate. ~ 5. D90 and D50 are images observed with a transmission electron microscope or a scanning electron microscope as described later, and the cumulative particle size distribution (number basis) from the small particle size side of the primary particles is 90% respectively. The particle size is 50%.

Further, the average particle size of the primary particle size of the polishing material as the entire polishing liquid composition is preferably 1 nm or more and less than 40 nm, and from the viewpoint of improving the polishing rate, more preferably 3 nm or more, more preferably 5 nm or more, From the viewpoint of reducing nanoscratches, the thickness is more preferably 35 nm or less, further preferably 30 nm or less, further preferably 25 nm or less, and further preferably 20 nm or less. Therefore, the average particle size of the primary particles is preferably 1 to 35 nm, more preferably 3 to 30 nm, still more preferably 5 to 25 nm, and still more preferably 5 to 20 nm from the viewpoint of economically reducing nanoscratches. When primary particles are aggregated to form secondary particles, the average particle size of the secondary particles is preferably 5 to 5 from the viewpoint of improving the polishing rate and reducing nanoscratches. It is 150 nm, More preferably, it is 5-100 nm, More preferably, it is 5-80 nm, More preferably, it is 5-50 nm, More preferably, it is 5-30 nm.
In addition, as a particle size distribution of the abrasive, D90 / D50 is preferably 1 to 5, more preferably 2 to 5, and further preferably 3 to 5, from the viewpoint of reducing nanoscratches and improving the polishing rate.

Among them, from the viewpoint of improving the polishing rate by increasing the filling rate of the abrasive and reducing nano scratches, among the two or more kinds of abrasives to be mixed, the abrasive having the largest average primary particle size and the average particle size are The ratio of the average particle size of the smallest abrasive (large particle size / small particle size) is preferably 1.3 to 10, more preferably 1.3 to 6, and further preferably 1.5 to 5. is there.
From the viewpoint of reducing nanoscratches and improving the polishing rate, the total amount of the abrasives having the maximum and minimum average particle diameters is preferably 10% by weight or more, more preferably 20% by weight, based on the total abrasives. More preferably, it is 25% by weight or more, more preferably 30% by weight or more, and further preferably 35% by weight or more.
Further, the zeta potential at the pH during polishing of the abrasive having the largest particle size and the abrasive having the smallest particle size may be the same, but from the viewpoint of reducing nanoscratches, it is preferable that the symbols are different.

  The average particle size of the primary particles of the abrasive is measured with a scanner using an image observed with a transmission electron microscope (TEM) (10000 to 50000 times) or a scanning electron microscope (SEM) (preferably 3000 to 100000 times). Import as image data, and use analysis software "WinROOF" (distributor: Mitani) to determine the biaxial average (average of major axis and minor axis) particle size of each particle for more than 1000 particle data It is determined by measuring the particle diameter (D50) at which the integrated particle diameter distribution (number basis) from the small particle diameter side of the primary particles is 50%, with the diameter as the diameter. The average particle size of the secondary particles can be measured as a volume average particle size using a laser beam diffraction method.

  As the abrasive in the present invention, an abrasive generally used for polishing can be used, and examples thereof include metal, metal or metalloid carbide, nitride, oxide, boride, diamond, and the like. It is done. The metal or metalloid element is derived from Group 2A, 2B, 3A, 3B, 4A, 4B, 5A, 6A, 7A or Group 8 of the periodic table (long period type). Specific examples of the abrasive include silicon oxide (hereinafter referred to as silica), aluminum oxide (hereinafter referred to as alumina), silicon carbide, diamond, manganese oxide, magnesium oxide, zinc oxide, titanium oxide, cerium oxide, zirconium oxide, and the like. In addition, the surface of these abrasives may be modified or surface-modified with a functional group, or may be compounded with a surfactant or an abrasive, and the use of one or more of these may reduce surface roughness. To preferred. Furthermore, from the viewpoint of reducing nanoscratches, colloidal particles and fumed silica particles are preferable, and colloidal particles such as colloidal silica, colloidal ceria, and colloidal alumina are particularly preferable. Colloidal silica obtained by is preferable.

A preferable combination of two or more abrasives is preferably at least one colloidal particle such as colloidal silica, colloidal ceria, or colloidal alumina from the viewpoint of reducing nanoscratches. More preferably, the two types are selected from colloidal particles such as colloidal silica, colloidal ceria, colloidal alumina, and more preferably two or more types are all colloidal particles such as colloidal silica, colloidal ceria, colloidal alumina, in particular. Preferably, the two or more types are all colloidal silica.
In colloidal silica, from the viewpoint of reducing nanoscratches, the average particle size of the primary particles is preferably 1 nm or more and less than 40 nm, more preferably 1 to 35 nm, and still more preferably 1 to 30 nm.

  The content of the abrasive in the polishing composition is preferably 0.5% by weight or more, more preferably 1% by weight or more, further preferably 3% by weight or more, and further preferably 5% from the viewpoint of improving the polishing rate. From the viewpoint of improving the surface quality, it is preferably 20% by weight or less, more preferably 15% by weight or less, still more preferably 13% by weight or less, and further preferably 10% by weight or less. That is, from the viewpoint of economically improving the surface quality, the content is preferably 0.5 to 20% by weight, more preferably 1 to 15% by weight, still more preferably 3 to 13% by weight, and still more preferably 5 to 5%. 10% by weight.

  From the viewpoint of reducing nanoscratches, the content of the abrasive to be mixed is determined by the zeta potential of the polishing composition at the pH during polishing after mixing the abrasive (as the entire abrasive contained in the polishing composition). The amount of zeta potential is preferably −10 mV to +5 mV, more preferably −8 mV to +3 mV, still more preferably −6 mV to +2 mV, and still more preferably −5 mV to +1.5 mV.

  In the present invention, the pH during polishing refers to the pH of the polishing composition immediately after being discharged from the polishing machine. The pH during polishing is determined according to the abrasive used, the degree of surface modification, and the like from the viewpoint of improving the polishing rate and reducing nanoscratches. When the abrasive is colloidal silica, the pH during polishing is preferably 7 or less, more preferably 5 or less, further preferably 4 or less, more preferably 3 or less, further preferably 2.5 or less, and further preferably 2 or less. From the viewpoint of preventing corrosion of the polishing machine, it is preferably 0.5 or more, more preferably 0.8 or more, still more preferably 1.0 or more, still more preferably 1.2 or more, and further preferably 1.4 or more. is there.

  A zeta potential adjusting agent can be blended in the polishing composition of the present invention as necessary. In this specification, the zeta potential adjusting agent refers to an additive for controlling the zeta potential of the surface of the abrasive in the polishing composition. Specifically, an agent that controls the surface potential of the abrasive particles by directly or indirectly adsorbing on the surface of the abrasive particles or changing the property such as acidity or basicity of the medium. Say. Examples of such zeta potential adjusting agents include acids, bases, salts, and surfactants.

  As the acid, an inorganic acid or an organic acid is used. Examples of the inorganic acid include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, amidosulfuric acid and the like. Examples of organic acids include carboxylic acids, organic phosphoric acids, amino acids, and the like. For example, carboxylic acids include monovalent carboxylic acids such as acetic acid, glycolic acid, and ascorbic acid, and divalent carboxylic acids such as oxalic acid and tartaric acid. And trivalent carboxylic acids such as citric acid, and examples of the organic phosphoric acid include 2-aminoethylphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), aminotri (methylenephosphonic acid), ethylenediaminetetra (Methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) and the like. Examples of amino acids include glycine and alanine. Among these, inorganic acids, carboxylic acids, and organic phosphoric acids are preferable from the viewpoint of reducing nanoscratches. For example, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, glycolic acid, oxalic acid, citric acid, HEDP, aminotri (methylene) Phosphonic acid), ethylenediaminetetra (methylenephosphonic acid), diethylenetriaminepenta (methylenephosphonic acid) are suitable.

  Examples of the base include ammonia water, hydroxylamine, alkylhydroxylamine, primary to tertiary alkylamine, alkylenediamine, alkylammonium hydroxide and the like. From the viewpoint of reducing nanoscratches, ammonia water and alkanolamine are preferable. .

  Examples of the salt include a salt of the acid. Examples of the cation forming the salt include metal ions derived from groups 1A, 2A, 3B, and 8 of the long-period periodic table, ammonium ions, and hydroxides. Ammonium ions or alkanol ammonium ions are preferred. Among these, examples of the acid salt include ammonium nitrate, ammonium sulfate, aluminum nitrate, aluminum sulfate, and aluminum chloride. Examples of basic salts include sodium citrate, sodium oxalate, sodium tartrate and the like. Examples of the neutral salt include sodium chloride, sodium sulfate, sodium nitrate and the like.

  Surfactants include low-molecular-weight active agents and high-molecular-weight active agents, which are adsorbed or chemically bonded to the surface of the abrasive and have one or more hydrophilic groups in the molecule, regardless of whether they are the same or different. It is. Among them, nonionic active agents having nonionic groups typified by ether groups (oxyethylene groups, etc.) and hydroxyl groups, anionic properties typified by carboxylic acid groups, sulfonic acid groups, sulfate ester groups and phosphate ester groups And an anionic activator having a cationic group, a cationic activator having a cationic group represented by quaternary ammonium, and an anionic group and a cationic group.

Further, as a preferable combination of the abrasive and the zeta potential adjusting agent, when the abrasive is silica, the zeta potential adjusting agent is nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, glycolic acid, oxalic acid, citric acid. HEDP, aminotri (methylenephosphonic acid), ethylenediaminetetra (methylenephosphonic acid), and diethylenetriaminepenta (methylenephosphonic acid) are preferable, and nitric acid, sulfuric acid, phosphoric acid, citric acid, and HEDP are more preferable. For example, nitric acid, sulfuric acid, phosphoric acid, citric acid, and HEDP are preferable as the zeta potential adjusting agent used when adjusting the zeta potential of silica particles at the pH during polishing to be positive or negative.
When the abrasives a and b are both silica, the sign of the zeta potential can be made different by adding the above zeta potential adjusting agent so that the sign of the zeta potential varies depending on the pH at the time of polishing.

  When the abrasive is alumina, the zeta potential adjuster is preferably sulfuric acid, ammonium sulfate, phosphoric acid, polyphosphoric acid, oxalic acid, citric acid, HEDP, sulfuric acid, ammonium sulfate, phosphoric acid, polyphosphoric acid, citric acid, HEDP is more preferred. For example, sulfuric acid, ammonium sulfate, phosphoric acid, polyphosphoric acid, citric acid, and HEDP are preferable as the zeta potential adjusting agent used when adjusting the zeta potential of alumina particles at the pH during polishing to be positive or negative.

  The content of the zeta potential adjusting agent in the polishing composition of the present invention is preferably 0.01 to 20% by weight and more preferably 0.05 to 10% by weight from the viewpoint of reducing nanoscratches.

  As the medium in the polishing composition of the present invention, water and / or a water-soluble organic solvent can be used. Examples of water include ion-exchanged water, distilled water, and ultrapure water. Examples of water-soluble organic solvents include primary to tertiary alcohols and glycols. The content of the medium corresponds to the balance obtained by setting the total weight of the polishing composition to 100% by weight and subtracting the contents of the abrasive, the zeta potential adjusting agent, and other optional components described later. The content of this medium is preferably 60 to 99% by weight, more preferably 70 to 98% by weight in the polishing composition.

Examples of the other optional components include oxidizing agents such as hydrogen peroxide, radical scavengers, inclusion compounds, rust preventives, antifoaming agents, and antibacterial agents.
The content of these other optional components is preferably 0 to 10% by weight, more preferably 0 to 5% by weight, from the viewpoint of reducing nanoscratches in the polishing composition.

The polishing composition of the present invention can be prepared, for example, as follows. That is, the zeta potential of the abrasive at the target pH (pH at the time of polishing) is measured, and the zeta potential is greater than 0 mV (abrasive a) and the zeta potential is less than 0 mV (abrasive b). Classify. Next, one or more types are selected from the classified abrasives a and b, respectively, and mixed with a medium to prepare an abrasive composition. If necessary, the above zeta potential adjusting agent and / or optional components are further blended and put into a polishing machine. The zeta potential adjusting agent and / or the optional component may be mixed during the preparation of the polishing liquid composition, or may be mixed with the polishing liquid composition immediately before being introduced into the polishing machine.
The abrasive material a and the abrasive material b may be mixed in the state of a concentrated slurry when preparing the polishing liquid composition, or may be mixed after each diluted with water or the like. Further, it may be mixed immediately before being put into the polishing machine in a diluted state.

  The zeta potential (before polishing) of the polishing composition that can be prepared as described above is preferably −10 mV to +5 mV from the viewpoint of reducing nanoscratches. More preferably, it is −8 mV to +3 mV, further −6 mV to +2 mV, further preferably −5 mV to +1.5 mV, and further −3 mV to +1 mV.

  In addition, before adding the zeta potential adjusting agent, even if it is a polishing liquid composition in which an abrasive having the same sign is mixed, it is a kind selected from the group consisting of an acid, a base, a salt and a surfactant during polishing. The above zeta potential adjusting agent is added and adjusted so that the zeta potential of at least one abrasive is more than 0 mV and the zeta potential of at least one other abrasive is less than 0 mV at the pH during polishing. By polishing, a substrate with reduced nanoscratches can be produced. In order to adjust the pH during polishing, the zeta potential adjuster may be supplied to the polishing machine from a separate supply port with the polishing composition, or once mixed with the polishing composition immediately before the polishing machine You may supply to.

  Nano scratches of the substrate can be reduced using the polishing composition of the present invention obtained as described above. Specifically, the substrate is sandwiched by a polishing machine to which a non-woven organic polymer polishing cloth or the like is attached, and the zeta potential at the pH at the time of polishing is (a) an abrasive material a exceeding 0 mV and (b) less than 0 mV And a polishing liquid composition containing the above-mentioned abrasive b is supplied to the surface of the substrate and polished by moving the polishing disk or the substrate while applying a constant pressure.

  The surface properties of the substrate (substrate to be polished) before being subjected to the polishing step using the polishing liquid composition of the present invention are not particularly limited. For example, a substrate having a surface property with a surface roughness (Ra) of 1 nm is suitable. Surface roughness is a measure of surface smoothness, and the evaluation method is not limited, but it is evaluated as roughness measurable at a short wavelength of 10 μm or less in an AFM (atomic force microscope), and the center line average roughness It can be expressed as Ra.

  The material of the object to be polished (substrate) preferably used in the present invention is, for example, a metal or semimetal such as silicon, aluminum, nickel, tungsten, copper, tantalum, titanium, or an alloy thereof, glass, glassy carbon. And glassy substances such as amorphous carbon, ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, and titanium carbide, and resins such as polyimide resin. Among these, it is suitable for an object to be polished containing a metal such as aluminum, nickel, tungsten, or copper and an alloy mainly composed of these metals. For example, a Ni—P plated aluminum alloy substrate or a glass substrate such as crystallized glass or tempered glass is more suitable, and a Ni—P plated aluminum alloy substrate is more suitable.

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

  The polishing composition of the present invention is suitably used for polishing precision component substrates. For example, it is suitable for polishing a magnetic disk medium such as a memory hard disk substrate, a magnetic recording medium substrate such as an optical disk and a magneto-optical disk, a precision component substrate such as a photomask substrate, an optical lens, an optical mirror, an optical prism, and a semiconductor substrate. Among them, the polishing composition of the present invention can remarkably reduce nano scratches that are important for high density and high integration, and is therefore suitable for polishing magnetic disks such as memory hard disk substrates and semiconductor substrates. It is particularly suitable for polishing a magnetic disk substrate.

  The polishing of the memory hard disk substrate or the semiconductor substrate is performed in a substrate manufacturing process, a silicon wafer (bare wafer) polishing process, a buried metal wiring forming process, an interlayer insulating film planarizing process, a buried capacitor forming process, or the like. The polishing composition of the present invention is particularly effective in the polishing process, but can be similarly applied to other polishing processes such as a lapping process.

  The invention also relates to a method for manufacturing a substrate. The method for producing a substrate of the present invention is a method for producing a substrate having a step of polishing using a polishing liquid composition containing two or more kinds of abrasives, and the zeta potential of the abrasive during polishing is At least one of them has a step of polishing at over 0 mV, and at least one of the other at less than 0 mV. By having such a configuration, the effect that the nano-scratch of the polished object after polishing can be remarkably reduced is exhibited.

  The abrasive used in the method for producing a substrate of the present invention may be the same as that used in the polishing composition of the present invention.

  Moreover, the manufacturing method of the board | substrate of this invention is 1 or more types chosen from the group which consists of an acid, a base, a salt, and surfactant into the polishing liquid composition containing 2 or more types of abrasives as the one aspect | mode. Of the substrate having the step of adjusting and polishing so that the zeta potential of at least one abrasive is more than 0 mV and the zeta potential of at least one other abrasive is less than 0 mV. Includes manufacturing methods. The zeta potential adjusting agent used in such an embodiment and the acid, base, salt and / or surfactant that can be used as the zeta potential adjusting agent are the same as those used in the above-described polishing composition of the present invention. Anything is acceptable.

  In order to adjust the pH during polishing, the zeta potential adjuster may be supplied to the polishing machine from a separate supply port with the polishing composition, or once mixed with the polishing composition immediately before the polishing machine You may supply to.

  The object to be polished used in the method for producing a substrate of the present invention may be the same as the object to be polished of the polishing composition of the present invention.

  The polishing step is preferably performed after the second step among the plurality of polishing steps, and particularly preferably performed in the final polishing step. At that time, in order to avoid mixing of the polishing material or polishing liquid composition in the previous process, different polishing machines may be used, and in the case of using different polishing machines, the substrate is removed at each stage. It is preferable to wash. The polishing machine is not particularly limited.

The manufactured substrate has very few nano scratches. Accordingly, when the substrate is, for example, a memory hard disk substrate, it can also cope with a recording density of 120 G / inch ² and further 160 G / inch ² , and when it is a semiconductor substrate, the wiring width 65 nm and even 45 nm can be supported.

  As a substrate to be polished, a Ni-P plated substrate was coarsely polished in advance with a polishing liquid containing an alumina abrasive to obtain an Ra of 1 nm, an aluminum alloy substrate having an outer periphery of 95 mmφ and an inner periphery of 25 mmφ. Polishing evaluation was performed.

  After adding a predetermined amount of sulfuric acid (special grade, manufactured by Wako Pure Chemical Industries, Ltd.), 60 wt% HEDP (manufactured by Solusia Japan), or citric acid (special grade, manufactured by Wako Pure Chemical Industries, Ltd.) listed in Table 2 as a zeta potential regulator. Then, colloidal silica shown in Table 1 was added as an abrasive to the aqueous solution to obtain a polishing composition.

1. Polishing conditions / polishing tester: Speedfam, double-sided 9B polishing machine / polishing cloth: Fujibow, polishing pad (thickness 0.9 mm, hole diameter 30 μm, Shore A hardness 60 °)
・ Surface plate speed: 32.5r / min
Polishing liquid composition supply amount: 100 mL / min
Polishing time: 4 minutes Polishing load: 7.8 kPa
・ Number of loaded substrates: 10

2. Measurement conditions for zeta potential Measuring instrument: Zeta Probe (Colloidal Dynamics)
Measurement temperature: 25 ℃
Measurement sample:
1) In the case of abrasive: A slurry prepared by adjusting the abrasive slurry containing each abrasive and water to the same pH as that during polishing using a zeta potential adjuster as necessary was used.
2) In the case of polishing liquid composition: The polishing liquid composition which is a measuring object was used as it was.
Number of measurements: The measurement was repeated three times under the same sample and the same measurement conditions, and the average of the three times was defined as the zeta potential.

3. Nano scratch measurement conditions / measurement equipment: “MicroMax VMX-2100CSP” manufactured by VISION PSYTEC
-Light source: 100% for both 2Sλ (250W) and 3Pλ (250W)
-Tilt angle: -6 °
・ Magnification: Maximum (Field range: 1/120 of the total area)
・ Observation area: total area (substrate with outer circumference 95mmφ and inner circumference 25mm)
・ Iris: notch
・ Evaluation: Randomly select 4 out of the substrates put into the polishing tester, and divide the total number of nano scratches (on each side) of each of the 4 substrates by 8 to get The number of nano scratches was calculated.

  From the results shown in Table 2, the substrates obtained using the polishing liquid compositions of Examples 1 to 6 are those in which the generation of nanoscratches is suppressed as compared with those of Comparative Examples 1 to 6. Recognize.

  The polishing liquid composition of the present invention is a precision component substrate, for example, a substrate for a recording medium such as a magnetic disk, an optical disk, or a magneto-optical disk, a precision component substrate such as a photomask substrate, an optical lens, an optical mirror, an optical prism, or a semiconductor substrate. It is suitably used for polishing.

Claims (6)

A polishing liquid composition comprising two or more types of colloidal silica having an average primary particle size of 1 nm or more and less than 40 nm, wherein the zeta potential at the pH during polishing is (a) colloidal silica with a pH greater than 0 mV ( a Ru Ken Migakueki composition name contains the b) less than 0mV colloidal silica, zeta potential (before polishing of the polishing composition in pH during polishing) is the -10 to + 5 mV, memory hard disk substrate Polishing liquid composition .   2. The polishing composition according to claim 1, wherein the ratio (large particle size / small particle size) of the largest and smallest of the average particle sizes of the primary particles of two or more kinds of colloidal silica is 1.3 to 10. 5. object. A polishing liquid composition obtained by mixing two or more colloidal silicas having an average primary particle size of 1 nm or more and less than 40 nm, wherein the colloidal silica has a zeta potential at a pH during polishing (a) greater than 0 mV And (b) a polishing liquid composition for a memory hard disk substrate , wherein the polishing liquid composition has a zeta potential (before polishing) of −10 to +5 mV at the pH during polishing . The polishing composition according to any one of claims 1 to 3, wherein the zeta potential of colloidal silica exceeding 0 mV is 10 mV or less, and the zeta potential of colloidal silica of less than 0 mV is -30 mV or more . The polishing composition according to any one of claims 1 to 4, wherein the pH during polishing is 1.0 to 4 . A method for producing a memory hard disk substrate, comprising a step of polishing the memory hard disk substrate using the polishing composition according to claim 1 .