JP4781693B2 - Method for reducing nano scratch on magnetic disk substrate - Google Patents

Description

  The present invention relates to a polishing liquid composition, a method for producing a polishing liquid composition, a method for reducing nanoscratches in a substrate using the 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 magnetic 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 the photoresist becomes shallow, and further surface smoothness is desired.

  On the other hand, improvement in substrate production efficiency is required year by year, and it is also desired that the substrate has excellent surface smoothness and can be polished in a short time.

In response to such demands, Patent Document 1 discloses a polishing composition that improves the surface smoothness of a substrate by using colloidal silica produced by an alkoxysilane method as an abrasive. It is not enough for a substrate for density.
JP 2001-269857 A

  That is, an object of the present invention is to provide a polishing liquid composition capable of reducing the surface roughness of the polished object after polishing and remarkably reducing nanoscratches, a method for producing the polishing liquid composition, and a substrate using the polishing liquid composition. Another object of the present invention is to provide a method for reducing nanoscratches, and a method for producing a substrate having a small surface roughness and significantly reduced nanoscratches.

  Accordingly, the present inventors have made extensive studies on the requirements for achieving the surface smoothness necessary for high density or high integration of precision component substrates such as memory hard disk substrates and semiconductor substrates, and have been able to detect them so far. “Nano scratches” (depth scratches of 10 nm or more, less than 100 nm, widths of 5 nm or more and less than 500 nm, and fine scratches on the substrate surface with a length of 100 μm or more) are increased in the density of memory hard disk substrates, and semiconductor substrates Then, for the first time, it was found that high integration was inhibited. Furthermore, the nano-scratch can be reduced by using colloidal silica produced by using a silicate such as sodium silicate and controlling the density of silanol groups present on the surface of the colloidal silica within a specific range. For the first time, the present invention was completed.

That is, the gist of the present invention is as follows.
[1] A polishing composition comprising colloidal silica produced using silicate and having an average primary particle diameter of 1 nm or more and less than 40 nm and water, wherein the silanol group density on the surface of the colloidal silica is colloidal. A polishing composition that is 0.06 to 0.3 mmol per gram of silica;
[2] A method for producing a polishing composition according to [1], comprising the following steps:
Step 1: Adjusting the pH of the silica dispersion containing colloidal silica having an average primary particle size of 1 nm or more and less than 40 nm and water to 10 to 14, and Step 2: Silica dispersion obtained in Step 1 A step of re-adjusting the pH of the liquid to 1 to 6 to obtain a polishing liquid composition;
[3] A method for reducing nano-scratch on a substrate, comprising a step of polishing a substrate to be polished using the polishing composition according to [1]
[4] A method for producing a substrate comprising a step of polishing a substrate to be polished using the polishing composition according to [1],
About.

  By using the polishing composition of the present invention, for example, in a polishing step of a precision component substrate for densification or high integration, the surface smoothness of the substrate after polishing is excellent, and the fineness that could not be detected conventionally is used. Since nano-scratches can be significantly reduced, there is an effect that high-quality memory hard disk substrates having excellent surface properties and precision component substrates such as semiconductor substrates can be efficiently manufactured.

  The polishing liquid composition of the present invention is a polishing liquid composition produced using silicate and containing colloidal silica having an average primary particle diameter of 1 nm or more and less than 40 nm and water, the surface of the colloidal silica The silanol group density is characterized by 0.06-0.3 mmol / g, and by having such characteristics, excellent surface properties can be achieved, and nano scratches that cause defects can be significantly reduced. Is possible. 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.

  Although the reduction mechanism of the nano scratch is not clear, it is presumed that the aggregation of colloidal silica is suppressed and the nano scratch is reduced by adjusting the silanol group density on the surface of the colloidal silica to a specific range.

Colloidal silica contained in the polishing composition of the present invention is colloidal silica produced by a so-called silicate method using a silicate such as sodium silicate or potassium silicate as a raw material, and its mode is not particularly limited. Sol or gel state.
Examples of the silicate method include a method (water glass method) in which silicate is used as a raw material and a condensation reaction is performed to produce silica particles.
In the present invention, by using colloidal silica produced by such a silicate method, compared to the case of using colloidal silica obtained by a conventional alkoxysilane method or fumed silica obtained by a dry method, nanoscratches are reduced. There is an advantage that it can be remarkably reduced.

  The average particle size of the primary particles of the colloidal silica is 1 nm or more and less than 40 nm regardless of whether or not one or more colloidal silicas are mixed. From the viewpoint of improving the polishing rate, it is preferably 3 nm or more, more preferably 5 nm. From the viewpoint of reducing the surface roughness (centerline average roughness: Ra, Peak to Valley value: Rmax), it is preferably 35 nm or less, more preferably 30 nm or less, still more preferably 25 nm or less, and even more preferably 20 nm. It is as follows. Therefore, from the viewpoint of economically reducing the surface roughness, 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. . Furthermore, when primary particles are aggregated to form secondary particles, the average particle size of the secondary particles is preferably from the viewpoint of improving the polishing rate and reducing the surface roughness of the substrate. Is 5 to 150 nm, more preferably 5 to 100 nm, still more preferably 5 to 80 nm, still more preferably 5 to 50 nm, still more preferably 5 to 30 nm.

  In addition, the average particle size of the primary particles of the colloidal silica is an accumulated volume from the small particle size side of the primary particles using an image observed with a transmission electron microscope regardless of whether or not one or more colloidal silicas are mixed. The particle diameter (D50) at which the frequency is 50% is obtained, and this value is taken as the average particle diameter of the primary particles. The average particle diameter of the secondary particles can be measured as a volume average particle diameter using a laser light scattering method.

  Furthermore, as for the particle size distribution of colloidal silica, D90 / D50, from the viewpoint of achieving reduction of nanoscratches, reduction of surface roughness and high polishing rate, regardless of whether or not one or more colloidal silicas are mixed. Preferably it is 1-3, More preferably, it is 1.3-3. Note that D90 is a particle size at which the cumulative volume frequency from the small particle size side of the primary particles becomes 90% using an image observed with a transmission electron microscope.

  The content of colloidal silica in the polishing composition is preferably 0.5% by weight or more, more preferably 1% by weight or more, still more 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 properties, 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 surface properties, 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%. -10% by weight.

In the present invention, the silanol group density on the colloidal silica surface is 0.06 to 0.3 mmol / g, and from the viewpoint of reducing nanoscratches, 0.08 to 0.3 mmol / g is preferable, and 0.1 to 0 0.3 mmol / g is more preferable, and 0.15-0.3 mmol / g is still more preferable.
The silanol group density can be measured by the method described later.

  The silanol group on the surface of the colloidal silica referred to in the present invention means a hydroxyl group that is present on the surface of the colloidal silica in the polishing liquid composition and directly bonded to the silicon atom of the colloidal silica. There is no particular limitation. Moreover, the production | generation conditions of a silanol group etc. are not ask | required.

  In the present invention, the silanol group density is measured by directly titrating a polishing composition with hydrochloric acid using a potentiometric titrator, and the number of silanol groups (unit: mmol) determined from the inflection point of the differentiated curve. Is divided by the weight (unit: g) of colloidal silica contained in the polishing composition used for titration, the silanol group density (unit: mmol / g) per 1 g of colloidal silica can be determined. When the pH of the polishing composition is 6 or more and 14 or less, titration with hydrochloric acid can be performed to determine the number of silanol groups. On the other hand, when the pH of the polishing composition is less than 6, the pH is adjusted to 9 with an aqueous solution of a strong base such as sodium hydroxide and titrated with hydrochloric acid using a potentiometric titrator.

  Although the mechanism of action of the metal element content in the polishing composition is not clear, it is preferably a specific content for reducing nanoscratches, for example, 0.001 to 2% by weight, more preferably It is 0.001 to 1 weight%, More preferably, it is 0.01 to 1 weight%, More preferably, it is 0.01 to 0.5 weight%, More preferably, it is 0.01 to 0.1 weight%.

Examples of the metal element include alkali metals such as Na and K and alkaline earth metals such as Mg and Ca. In many cases, these metal elements are derived from the production of colloidal silica (including the case where the colloidal silica surface is modified with aluminum or the like). In that case, the content of the metal element derived from colloidal silica in the polishing composition is For example, 0.001 to 0.2% by weight is preferable, and from the viewpoint of reducing nanoscratches, more preferably 0.001 to 0.1% by weight, still more preferably 0.005 to 0.1% by weight, and still more preferably. Is 0.005 to 0.05% by weight.
The metal element content derived from colloidal silica does not include metal elements involved in pH adjustment of the silica dispersion in the present invention.
Moreover, in order to adjust metal element content derived from colloidal silica to a specific range as mentioned above, it can adjust with the density | concentration of the silicate at the time of colloidal silica manufacture, for example.

  Among these, when the metal element is Na or K, 0.001 to 0.2% by weight is preferable, and more preferably 0.001 to 0.2% by weight, from the viewpoint of reducing nanoscratches, as in the above case. It is 0.1% by weight, more preferably 0.005 to 0.1% by weight, and still more preferably 0.005 to 0.05% by weight.

  Water is used as the medium in the polishing composition of the present invention. Examples of water include ion exchange water, distilled water, and ultrapure water. In the present invention, in addition to water, a water-soluble organic solvent can also be used as a medium. Examples of the water-soluble organic solvent include primary to tertiary alcohols and glycols. The content of these media is preferably 69 to 99% by weight, more preferably 79 to 98% by weight in the polishing composition.

  Moreover, other components can be mix | blended with the polishing liquid composition of this invention as needed. For example, abrasives such as aluminum oxide and cerium oxide generally used for polishing excluding the colloidal silica; inorganic acid or organic acid; inorganic base or organic base such as ammonia water, sodium hydroxide, potassium hydroxide, etc. Acidic salts, neutral salts or basic salts; surfactants; oxidizing agents such as hydrogen peroxide; radical scavengers; clathrate compounds; rust inhibitors; and antifoaming agents and antibacterial agents. Among these, from the viewpoint of improving the polishing rate and reducing the surface roughness of the substrate, an oxidizing agent such as an inorganic or organic acid, an acidic salt, or hydrogen peroxide is preferable. The content of these other components is preferably 0 to 10% by weight and more preferably 0 to 5% by weight from the viewpoint of improving the polishing rate and reducing the surface roughness of the substrate in the polishing composition. preferable.

  The polishing composition of the present invention can be prepared by appropriately mixing the above components.

  In the present invention, from the viewpoint of increasing the silanol group density to a desired range and reducing nanoscratches, a step of temporarily increasing the pH of the silica dispersion that is the raw material of the polishing composition (step 1), and subsequently the pH It is preferable to manufacture a polishing liquid composition through a lowering step (step 2). More specifically, in Step 1, the pH of the silica dispersion (also referred to as colloidal silica slurry) containing colloidal silica having an average primary particle size of 1 nm or more and less than 40 nm and water is increased by 10 to 14, and the silanol group is increased. From the point of view, it is a step of adjusting to preferably 10 to 13, more preferably 10 to 12. In step 2, the pH of the silica dispersion obtained in step 1 is adjusted to 1 to 6, preferably from 1 to 4, and more preferably 1 to 2, and more preferably 1 to 2 to obtain a polishing composition. It is a process.

As a method for reducing the silanol group, _e.g., NaCl, or by adding a metal salt such as CaCl _2, MgCl _2, AlCl ₃ to silica dispersion, a method of heating the silica dispersion.

  The polishing composition prepared by the method as described above has an advantage that the effect of reducing nanoscratch is particularly excellent.

  As the pH adjuster used in step 1, an inorganic base such as aqueous ammonia, sodium hydroxide, potassium hydroxide, hydroxylamine, or an organic base can be used. Among these, from the viewpoint of reducing nanoscratches, preferably an inorganic base, more preferably aqueous ammonia, sodium hydroxide, potassium hydroxide, and still more preferably sodium hydroxide, potassium hydroxide.

  Moreover, the pH adjuster used for the process 2 can use an inorganic acid and an organic acid. Among these, from the viewpoint of reducing nanoscratches, preferably hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, polyphosphoric acid, glycolic acid, oxalic acid, citric acid, 1-hydroxyethylidene-1,1-diphosphonic acid, aminotri ( Methylenephosphonic acid) and ethylenediaminetetra (methylenesulfonic acid), more preferably hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, citric acid, and 1-hydroxyethylidene-1,1-diphosphonic acid.

  As the pH adjustment method of step 1 of the present invention, it is preferable to add a pH adjuster to the silica dispersion while stirring the silica dispersion in order to suppress gelation of colloidal silica that may occur due to an increase in pH. . The operating conditions such as the stirring speed and the addition speed of the pH adjuster may be adjusted as appropriate so as to suppress the gelation of colloidal silica. The pH-adjusted silica dispersion in Step 1 is preferably used in Step 2 as soon as possible from the viewpoint of effectively forming silanol groups and reducing nanoscratches.

  The addition of the pH adjusting agent in step 2 is preferably continued after stirring for a while after reaching a predetermined pH, for example, after confirming that there is no pH change after 1 hour. If pH fluctuation is confirmed, a pH adjuster is further added and the above operation is repeated.

  The concentration of each component in the polishing liquid composition may be any of the concentration during production of the composition and the concentration during use. Usually, a polishing composition is produced as a concentrated liquid, and it is often used after being diluted at the time of use.

  The pH of the polishing composition of the present invention is, for example, preferably 7 or less, more preferably 5 or less, still more preferably 4 or less, and still more preferably 3 or less, from the viewpoint of improving the polishing rate and reducing nanoscratches. More preferably, it is 2.5 or less, more preferably 2 or less.

  By using the polishing composition having such a configuration, it is possible to obtain a precision component substrate having excellent surface properties with very few nanoscratches.

  The nano-scratch in the present invention is a fine scratch on the substrate surface having a depth of 10 nm or more, less than 100 nm, a width of 5 nm or more, less than 500 nm, and a length of 100 μm or more, and is detected by an atomic force microscope (AFM). It can be quantitatively evaluated as the number of scratches by measurement with “MicroMax” which is a visual inspection apparatus described in the examples described later.

  Further, the evaluation method for the surface roughness, which is a measure of surface smoothness, is not limited, but in the present invention, it is evaluated as a roughness that can be measured at a short wavelength of 10 μm or less in AFM, and the centerline average roughness ( AFM-Ra). Specifically, it can be obtained by the method described in Examples below.

  Examples of the material of the substrate to be polished that are preferably used in the present invention include metals, metalloids such as silicon, aluminum, nickel, tungsten, copper, tantalum, and titanium, or alloys thereof, glass, glassy carbon, and amorphous. Examples thereof include glassy substances such as carbon, ceramic materials such as alumina, silicon dioxide, silicon nitride, tantalum nitride, and titanium carbide, and resins such as polyimide resins. Among these, it is suitable for a substrate to be polished containing a metal such as aluminum, nickel, tungsten, copper, and an alloy containing these metals as a main component. For example, an aluminum alloy substrate plated with Ni—P or a glass substrate such as crystallized glass or tempered glass is more suitable, and an aluminum alloy substrate plated with Ni—P is more suitable.

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

  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. Particularly suitable for polishing magnetic disk substrates.

  The polishing of the memory hard disk substrate and the semiconductor substrate is performed in a polishing process of a silicon wafer (bare wafer), a formation process of an embedded metal wiring, a planarization process of an interlayer insulating film, a formation process of an embedded metal wiring, an embedded capacitor formation process, and the like.

  As described above, by using the polishing composition of the present invention, the nano-scratch of the substrate can be significantly reduced. Accordingly, the present invention relates to a method for reducing nanoscratches on a substrate using the polishing composition, and a method for producing a substrate.

  The method for reducing substrate nanoscratches or the method for producing a substrate of the present invention is a method comprising a step of polishing a substrate to be polished using the polishing composition of the present invention. Specifically, as the polishing step, the substrate is sandwiched between polishing plates with a non-woven organic polymer polishing cloth or the like attached thereto, the polishing composition of the present invention is supplied to the substrate surface, and a constant load is applied. For example, a method of polishing by moving a polishing board or a substrate may be used. The conditions such as the supply speed of the polishing composition, the polishing load, and the rotational speed for moving the polishing disk and the substrate may be within a known range.

  The surface property of the substrate before being subjected to the polishing step using the polishing composition of the present invention is not particularly limited. For example, a substrate having a surface property with a center line average roughness (Ra) of 1 nm or less is suitable.

  The polishing step is preferably performed after the second step among the plurality of polishing steps, and more 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 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 substrate manufactured by using the polishing composition of the present invention or the substrate manufacturing method of the present invention as described above is excellent in surface smoothness, for example, the center line average roughness (AFM-Ra) is 0.00. 3 nm or less, Preferably it is 0.2 nm or less, More preferably, it is 0.15 nm or less, More preferably, the thing of 0.13 nm or less is obtained.

Further, the manufactured substrate has very few nano scratches and is suitable for a magnetic disk substrate or a semiconductor substrate. For example, in the case of a memory hard disk substrate, it is also suitable for a recording density of 120 G / inch ² and further 160 G / inch ² . Further, in the case of a semiconductor substrate, it can be suitably used for a wiring width of 65 nm and further 45 nm.

  As a substrate to be polished, a Ni-P plated substrate was previously roughly polished with a polishing liquid containing an alumina abrasive, and the center line average roughness (AFM-Ra) was 1 nm, and the outer periphery was 95 mmφ with a thickness of 1.27 mm. Then, polishing evaluation was performed using an aluminum alloy substrate having an inner circumference of 25 mmφ.

Examples 1 to 9 and Comparative Examples 1 to 4 (Examples 1 to 9 are reference examples)
As shown in Table 1, as colloidal silica, colloidal silica slurry A (manufactured by DuPont, aqueous dispersion having a silica concentration of 40% by weight, D90 / D50 = 1.3),
B (manufactured by DuPont, an aqueous dispersion having a silica concentration of 40% by weight, D90 / D50 = 1.4),
C (manufactured by DuPont, an aqueous dispersion having a silica concentration of 40% by weight, D90 / D50 = 1.4),
D (manufactured by Catalyst Kasei Kogyo, an aqueous dispersion having a silica concentration of 40% by weight, D90 / D50 = 1.1),
E (manufactured by DuPont, an aqueous dispersion having a silica concentration of 40% by weight, D90 / D50 = 1.2),
F (manufactured by Fuso Chemical Industries, an aqueous dispersion having a silica concentration of 13% by weight, D90 / D50 = 1.1),
G (manufactured by DuPont, an aqueous dispersion having a silica concentration of 50% by weight, D90 / D50 = 2.5),
Polishing with 60% by weight of 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) aqueous solution, 98% by weight of sulfuric acid and / or citric acid, and 35% by weight of hydrogen peroxide aqueous solution as other components A liquid composition was prepared. The balance is ion exchange water.

  On the other hand, as shown in Table 1, as the fumed silica, a polishing liquid composition was prepared using fumed silica slurry A (manufactured by Nippon Aerosil Co., Ltd., D90 / D50 = 1.1) and a 60 wt% HEDP aqueous solution. The balance is ion exchange water.

  The colloidal silica slurries A to E and G are obtained using a silicate method, the colloidal silica slurry F is obtained using an alkoxysilane method, and the fumed silica slurry A is a dry type. It was obtained using the method.

  The order of mixing each component in Examples 1 to 9 and Comparative Examples 1, 3, and 4 is that an aqueous hydrogen peroxide solution is added to an aqueous solution obtained by diluting HEDP and sulfuric acid or citric acid with water, and then the remaining components are added. After mixing, it was added in portions to the stirred colloidal silica slurry to prepare.

  On the other hand, the order of mixing each component of Comparative Example 2 was as follows: an aqueous solution obtained by further diluting 60% by weight of HEDP aqueous solution with the remaining half of the ion-exchanged water was dispersed with the remaining half of the ion-exchanged water. It added little by little to the fumed silica slurry A, and prepared.

Example 10
A 1N aqueous sodium hydroxide solution (manufactured by Sigma-Aldrich Japan, Factor 0.999) was dropped into the stirring colloidal silica slurry B so as not to cause gelation of the colloidal silica, and a silica dispersion having a pH of 10.0 was prepared. Prepared (step 1). While stirring this silica dispersion, a predetermined amount of a 60% by weight HEDP aqueous solution, 98% by weight sulfuric acid and ion-exchanged water as shown in Table 1 was added to obtain a polishing liquid composition having a pH of 1.5. (Step 2).

Example 11
In Example 10, a polishing composition was obtained in the same manner as in Example 10 except that the pH of the silica dispersion was adjusted to 12.0.

Example 12
In Example 10, it replaced with the colloidal silica slurry B, and obtained the polishing composition by the same method as Example 10 except having used the colloidal silica slurry G.

Example 13
In Example 10, it replaced with the colloidal silica slurry B, and used the colloidal silica slurry G, and obtained the polishing liquid composition by the same method as Example 10 except having adjusted the pH of the silica dispersion liquid to 12.0.

  For the polishing liquid compositions obtained in Examples 1 to 13 and Comparative Examples 1 to 4, silanol group density, polishing rate, nano scratch and AFM-Ra were measured and evaluated based on the following methods. The obtained results are shown in Table 2. Table 2 also shows the metal element content derived from colloidal silica, the average particle diameter of primary particles of silica, and the metal element content in the polishing composition.

1. Silanol group density measurement conditions / potential difference measuring device: manufactured by Kyoto Electronics Co., Ltd., automatic potentiometric titrator “AT-310J”
-Titration reagent: 0.01N hydrochloric acid aqueous solution-Titration reagent dropping speed: 0.03 ml / min-Measurement sample: 0.2% by weight silica concentration of the polishing composition of Examples 1 to 13 or Comparative Examples 1 to 4 A sample diluted with ion-exchanged water was used as a measurement sample.

2. Polishing conditions / polishing tester: Speedfam, double-sided 9B polishing machine / polishing cloth: manufactured by Fujibow, polishing pad (thickness 0.9 mm, opening diameter 30 μm)
・ Rotating speed of polishing machine: 32.5 r / min
Polishing liquid composition supply rate: 100 mL / min
Polishing time: 4 minutes Polishing load: 7.8 kPa
・ Number of loaded substrates: 10

3. Measurement conditions of polishing rate Unit by dividing weight difference (g) of substrate before and after polishing test by Ni-P density (8.4 g / cm ³ ), substrate surface area (131.9 cm ² ) and polishing time. The polishing rate was obtained by calculating the amount of double-side polishing of the substrate per hour.

4). 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 25mmφ)
・ Iris: notch
・ Evaluation: Of the 10 substrates put into the polishing tester, 4 were selected at random, and the total number of nano scratches on each side of the 4 substrates was divided by 8. The number of nano scratches per substrate surface (lines / surface) was calculated. Moreover, the evaluation of the nano scratch described in the table was performed by relative evaluation with respect to the number of nano scratches of Comparative Example 1 (240 / surface).

5. AFM-Ra measurement conditions and measurement equipment: “TM-M5E” manufactured by Veeco
・ Mode: non-contact
・ Scanrate: 1.0 Hz
・ Scanarea: 10 × 10 μm
Evaluation: The center between the inner periphery and the outer periphery was measured at 120 points every 120 °, and this was performed on both sides of the substrate to obtain an average value of a total of 6 points.

6). Measurement of metal element content The polishing composition, silica slurry or silica was heated and incinerated, and then an aqueous hydrofluoric acid solution was added and further decomposed by heating. The resulting residue was dissolved in water, and the metal element was quantified by ICP (radio frequency inductively coupled plasma) emission spectroscopy.

7). Average particle diameter of primary particles of silica Using the slurry-like silica particles used to prepare the polishing composition as a sample, JEOL transmission electron microscope “JEM-2000FX” (80 kV, 1 to 50,000 times) The sample was observed according to the instructions attached by the manufacturer of the microscope, and a TEM image was taken. The photograph is taken into a personal computer as image data by a scanner, and an analysis software “WinROOF” (distributor: Mitani Corp.) is used to determine the equivalent circle diameter of each silica particle. After analyzing the silica particle data, it was converted from the particle diameter to a particle volume as a sphere having the diameter using spreadsheet software “EXCEL” (manufactured by Microsoft Corporation).

  Based on the particle size distribution data of the silica particles obtained in this manner, the ratio of particles having a certain particle size (volume basis%) in all particles is expressed as the cumulative frequency from the small particle size side, and the cumulative volume frequency (% ) Was obtained, and the particle size (D50) at which this value was 50% was determined, and this value was taken as the average particle size of the primary particles. Here, the particle diameter of one primary particle was a biaxial average (average of major axis and minor axis).

  From the results shown in Table 2, in the substrates obtained by polishing using the polishing composition of Examples 1 to 13, the generation of nanoscratches was suppressed and the surface roughness was higher than those of Comparative Examples 1 to 4. It can be seen that is reduced.

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

Claims (6)

The colloidal silica whose average particle diameter of the primary particle manufactured using a silicate is 1 nm or more and less than 40 nm contains water, and the silanol group density on the surface of the colloidal silica is 0.06 to 0.3 mmol per 1 g of colloidal silica. And
Step 1: A step of increasing the pH of a silica dispersion containing colloidal silica having an average primary particle size of 1 nm or more and less than 40 nm and water to adjust to pH 10 to 14 and Step 2: obtained in Step 1 Re-adjusting the pH of the silica dispersion to 1 to 6 to obtain a polishing composition;
Nano-scratch of magnetic disk substrate having a step of polishing a Ni-P plated substrate using a polishing composition for a magnetic disk substrate having a pH of 1 to 6 obtained by a production method comprising: Reduction method . The reduction method according to claim 1, wherein the metal element content in the polishing composition is 0.001 to 2% by weight. The reduction method according to claim 1 or 2, wherein the content of the metal element derived from colloidal silica in the polishing composition is 0.001 to 0.2% by weight. The colloidal silica whose average particle diameter of the primary particle manufactured using a silicate is 1 nm or more and less than 40 nm contains water, and the silanol group density on the surface of the colloidal silica is 0.06 to 0.3 mmol per 1 g of colloidal silica. And
Step 1: increasing the pH of a silica dispersion containing colloidal silica having an average primary particle size of 1 nm or more and less than 40 nm and water, and adjusting the pH to 10 to 14, and
Step 2: A step of readjusting the pH of the silica dispersion obtained in Step 1 to 1 to 6 to obtain a polishing composition,
A method for producing a magnetic disk substrate, comprising a step of polishing a Ni-P plated substrate using a polishing composition for a magnetic disk substrate having a pH of 1 to 6, obtained by a production method comprising: . The manufacturing method according to claim 4, wherein the metal element content in the polishing composition is 0.001 to 2% by weight. The production method according to claim 4 or 5, wherein the content of the metal element derived from colloidal silica in the polishing composition is 0.001 to 0.2% by weight.