JP2000109818A - Composition of abrasive solution - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce surface roughness and to improve an abrasive rate without generating a surface defect on a polished material by containing an alkylsulfonic acid or its salt having specific number of carbons, an abrasive and water. SOLUTION: An alkylsulfonic acid contained in a composition of an abrasion solution has a carbon number of a 1-4C and specifically methanesulfonic acid is preferable. The salt of this alkylsulfonic is preferably an Al salt, Ni salt or Fe slat. Total content of the alkylsulfonic acid and its salt in the composition is preferably 0.01-20 wt.%. The abrasive is knoop hardness of 1500-3000 and α-alumina or γ-alumina particles having purity not less than 98% are preferably used. A content of the abrasive in the composition is preferably 0.01-40 wt.%. A content of water in the composition is preferably 60-99.8 wt.%. This composition is suitably used for polishing a base for precision parts.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polishing composition, a method for polishing a substrate to be polished, and a method for manufacturing a substrate for precision parts.

[0002]

2. Description of the Related Art As the density of hard disks has increased, the flying height of a magnetic head has become smaller. As a result, in the process of polishing a hard disk substrate, it is required to improve the polishing rate and reduce the surface roughness, and a polishing composition and a polishing method containing an ammonium salt of a carboxylic acid such as acetic acid have been studied (Japanese Patent Application Laid-Open (JP-A) No. Heisei 9 (1999)). 2-158683 gazette).

In the field of semiconductors, high integration,
As the speed is increased, the design room of the semiconductor device is miniaturized, the depth of focus in the device manufacturing process is reduced, and the flatness of the pattern formation surface is further required.

However, in the prior art, the surface roughness of the hard disk substrate and the surface on which the semiconductor pattern is formed is not sufficiently reduced, flattened, and polished, and depending on the object to be polished, surface defects such as scratches and pits are generated. In some cases, it was not satisfactory as a polishing composition.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a polishing rate can be improved without causing a surface defect on an object to be polished,
An object of the present invention is to provide a polishing composition capable of reducing surface roughness, a method for polishing a substrate to be polished, and a method for manufacturing a substrate for precision parts.

[0006]

That is, the gist of the present invention is as follows.
A polishing composition comprising a C 1-4 alkyl sulfonic acid or a salt thereof, an abrasive, and water, a method for polishing a substrate to be polished using the polishing composition, and a substrate for a precision component. It relates to a manufacturing method.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific examples of alkylsulfonic acids having 1 to 4 carbon atoms include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, and butanesulfonic acid. Of these, methanesulfonic acid is preferred from the viewpoint of improving the polishing rate.

Examples of the salts of these alkylsulfonic acids include salts of alkylsulfonic acids with metals, ammonium, alkylammonium having 1 to 20 carbon atoms, and alkanolamines having 2 to 12 carbon atoms. The metal, ammonium, alkylammonium, and alkanolamine are not particularly limited as long as they can form a salt with alkylsulfonic acid.

Specific examples of the metal include 1A, 1B, 2A, 2B, 3A, 3B, 7A and 8 in the periodic table (long period type).
Metals belonging to the group.

Specific examples of the alkyl ammonium include:
Examples include dimethyl ammonium, trimethyl ammonium, tetramethyl ammonium, tetraethyl ammonium, tetrabutyl ammonium and the like. Specific examples of the alkanolamine include monoethanolamine, diethanolamine, and triethanolamine.

[0011] Among the alkyl sulfonates, aluminum salts, nickel salts, iron salts, cobalt salts, magnesium salts, cerium salts, and ammonium salts are preferred, and aluminum salts, nickel salts, and iron salts are more preferred.

The alkylsulfonic acid and the alkylsulfonic acid salt may be used alone or in combination.

The content of the alkylsulfonic acid or a salt thereof in the polishing composition of the present invention is preferably 0.01 to 20% by weight, more preferably 0.05 to 15% by weight, and particularly preferably 0.1 to 10% by weight. From the viewpoint of improving the polishing rate
0.01% by weight or more is preferable, and from the viewpoint of economy, 20% by weight
% Or less is preferable.

As the abrasive, abrasive grains generally used for polishing can be used. Examples of the abrasive grains include metals; metal or metalloid carbides, nitrides, oxides, borides, and diamonds. Metals or metalloid elements are 3A, 4A, 5A, 3B, 4B, 5A of the periodic table (long period type).
It is derived from group B, 6B, 7B or 8 groups. Specific examples of the abrasive grains include alumina particles, silicon carbide particles, diamond particles, magnesium oxide particles, cerium oxide particles, zirconium oxide particles, colloidal silica particles or fumed silica particles, which are used to improve the polishing rate. Is preferred. In particular, alumina particles,
Cerium oxide particles, zirconium oxide particles, colloidal silica particles, and fumed silica particles are suitable for polishing precision parts such as semiconductor wafers, semiconductor elements, and substrates for magnetic recording media. Alumina particles and colloidal silica particles are particularly suitable for polishing a substrate for a magnetic recording medium. Among the alumina particles, the intermediate alumina particles are preferable because the surface roughness of the object to be polished can be extremely reduced. The term “intermediate alumina particles” is a general term for alumina particles other than α-alumina particles, and specifically includes γ-alumina particles, δ-alumina particles, θ-alumina particles, η-alumina particles, and amorphous alumina particles. And the like. Further, as the alumina particles, alumina-based particles in which secondary particles are redispersed into primary particles when mechanically stirring or polishing the polishing composition can be suitably used.

The average particle size of the primary particles of the abrasive is preferably 0.002 to 3 μm, more preferably 0.01 to 1 μm, further preferably 0.02 to 0.8 μm, and particularly preferably 0.05 to 0.5 μm. From the viewpoint of improving the polishing rate is preferably 0.002μm or more, from the viewpoint of reducing the surface roughness of the object to be polished 3μm
The following is preferred.

Further, when the primary particles are aggregated to form secondary particles, the average particle size of the secondary particles is preferably 0.05 to 2 μm, more preferably 0.1 to 1.5 μm, and particularly preferably 0.3 to 1.5 μm. 1.21.2 μm. The thickness is preferably 0.05 μm or more from the viewpoint of improving the polishing rate, and is preferably 2 μm or less from the viewpoint of reducing the surface roughness of the polished object.

The average particle size of the primary particles of the abrasive can be determined by observing with a scanning electron microscope (preferably 3000 to 100,000 times), analyzing the image, and measuring the biaxial average diameter. Further, the average particle size of the secondary particles can be measured as a volume average particle size using a laser light diffraction method.

The Knoop hardness (JIS Z-2251) of the abrasive is preferably from 700 to 9000, and more preferably from 1,000 to 5, from the viewpoint of obtaining a sufficient polishing rate and not causing surface defects on the object to be polished.
000 is more preferred, and 1500 to 3000 is even more preferred.

The specific gravity of the abrasive is preferably 2 to 6 from the viewpoints of dispersibility, supply to the polishing apparatus, and recovery and reuse.
~ 4 is more preferable.

In the polishing composition of the present invention, from the viewpoint of enhancing the synergistic effect of improving the polishing rate and preventing the generation of scratches and pits by adding an alkyl sulfonic acid and a salt thereof and an abrasive, particularly, The preferably used abrasive material has a Knoop hardness of 1500 to 3000, a purity of 98% by weight or more,
It is preferably at least 99% by weight, particularly preferably at least 99.9% by weight, of α-alumina particles or γ-alumina particles. This abrasive can be produced by a crystal growth method using a high-purity aluminum salt (such as the Bernoulli method). The purity of the abrasive can be measured by dissolving 1 to 3 g of the abrasive in an aqueous acid or alkali solution, and quantifying aluminum ions using a plasma emission spectrometry.

The abrasive is used in a slurry state using water as a medium. The content of the abrasive in the polishing composition,
It is preferable to appropriately determine the viscosity depending on the viscosity of the polishing composition, the required quality of the polishing object, and the like. The content of the abrasive in the polishing composition is preferably 0.01 to 40% by weight, more preferably 0.1 to 25% by weight, and particularly preferably 1 to 15% by weight. The content is preferably 0.01% by weight or more from the viewpoint of efficient polishing, and is preferably 40% by weight or less from the viewpoint of economy and reduction in surface roughness.

Further, from the viewpoint of improving the polishing rate and sufficiently exhibiting the effect of reducing the surface roughness, the content ratio of the abrasive in the polishing composition to the alkylsulfonic acid and its salt [abrasive (% By weight) / content of alkyl sulfonic acid and its salt (% by weight)]
It is desirable that the compounding ratio be 0.001 to 200, more preferably 0.01 to 100, further preferably 0.1 to 50, and particularly preferably 1 to 25.

The water in the polishing composition of the present invention is used as a medium. The content of water in the polishing composition is preferably 60 to 99.8% by weight, from the viewpoint of efficiently polishing the object to be polished.
%, More preferably 70 to 99.4% by weight, particularly preferably 90 to 90% by weight.
99.0% by weight.

The polishing composition of the present invention may contain other components as required. As the other component, a metal salt or an ammonium salt of a monomer type acid compound,
Examples include peroxides, thickeners, dispersants, rust inhibitors, chelating agents, basic substances, and surfactants. Specific examples of metal salts, ammonium salts and peroxides of monomeric acid compounds are described in JP-A-62-25187, page 2, upper right column, lines 3 to 11,
No. 63-251163, page 3, upper left column, 4 lines to upper right column, 2 lines, JP-A 3-11
No. 5383, page 2, lower right column, line 16 to item 3, upper left column, line 11, JP-A-4-27
No. 5387, page 2, right column, line 27 to page 3, left column, line 12 are mentioned. The content of these other components in the polishing composition is preferably 0.1 to 5.0% by weight.

The pH of the polishing composition of the present invention is preferably from 2 to 12, from the viewpoints of the cleaning properties of the substrate and the corrosion prevention of the processing machine. In a precision component substrate mainly for a metal such as an Ni-P plated aluminum substrate, the pH is particularly preferably 2 to 8 from the viewpoint of improving the polishing rate and improving the surface quality. In addition, when used for polishing semiconductor wafers, semiconductor elements, and other oxides, semimetals, and the like, particularly for polishing silicon wafers, from the viewpoint of improving the polishing rate and improving the surface quality, the pH is more preferably 7 to 12, 8 to 12 are more preferable, and 9 to 11 are particularly preferable. The pH can be adjusted using an inorganic acid such as nitric acid or sulfuric acid, a metal salt or an ammonium salt of the inorganic acid, a peroxide, a basic substance such as sodium hydroxide, potassium hydroxide, or an amine.

Further, the method for polishing a substrate to be polished according to the present invention comprises:
A step of polishing a substrate to be polished using the polishing composition of the present invention.

The method of manufacturing a substrate for precision parts of the present invention includes a step of polishing a substrate to be polished using the polishing composition of the present invention.

The material of the substrate to be polished is, for example, silicon,
Metals or semi-metals such as aluminum, tungsten, copper, etc.
Alloys containing these metals as main components, glassy substances such as glass, glassy carbon and amorphous carbon, ceramic materials such as alumina, titanium carbide and silicon dioxide;
Examples of the resin include a resin such as a polyimide resin. Among these, when polishing an object to be polished made of a ductile material such as aluminum, nickel, tungsten, copper, and an alloy containing these metals as a main component, particularly a substrate to be polished made of Ni-P plated aluminum. In addition, the use of the polishing composition of the present invention is preferable because the generation of surface defects is suppressed and high-speed polishing can be performed while the surface roughness is lower than in the past.

There is no particular limitation on the shape of the object to be polished. For example, a shape having a flat portion such as a disk shape, a plate shape, a slab shape or a prism shape, or a shape having a curved surface portion such as a lens is used in the present invention. It is an object to be polished using the liquid composition. Among them, it is particularly excellent in polishing a disk-shaped object to be polished.

The polishing composition of the present invention is particularly suitably used for polishing substrates for precision parts. For example, it is suitable for polishing substrates of magnetic recording media such as hard disks, optical disks, and magneto-optical disks, semiconductor substrates such as semiconductor wafers and semiconductor elements, optical lenses, optical mirrors, half mirrors, and optical prisms. Among them, it is suitable for polishing a substrate of a magnetic recording medium or a semiconductor substrate, particularly a hard disk substrate. The polishing of a semiconductor element includes, for example, polishing performed in a step of planarizing an interlayer insulating film, a step of forming a buried metal wiring, a step of forming a buried element isolation film, and a step of forming a buried capacitor. By performing polishing as described above, a precision component substrate can be manufactured.

Although the polishing composition of the present invention is particularly effective in the polishing step, it can be similarly applied to other polishing steps such as a lapping step.

[0032]

[Example] Knoop hardness 2000, primary average particle size as abrasive
Α-alumina with 0.29 μm, secondary average particle size 0.56 μm (purity 9
9.9%) 10% by weight, an alkylsulfonic acid or an alkylsulfonic acid salt shown in Table 1, and the remaining water were mixed and stirred to obtain a polishing composition.

Using the polishing composition obtained, the center line average roughness Ra measured by the following method was 0.1 μm, and the thickness was 0.9 μm.
2.5 inch diameter Ni-P plated aluminum substrate surface is polished with a double-sided processing machine under the following double-sided processing machine setting conditions, and the Ni-P plated aluminum substrate used as a hard disk substrate A polished product was obtained.

The setting conditions of the double-side processing machine are shown below. Double-side processing machine used: 6B type double-side processing machine manufactured by Kyoritsu Seiki Co., Ltd. Processing pressure: 9.8 kPa Polishing pad: Polytex DG (manufactured by Rodel Nitta) Plate rotation speed: 40 r / min Polishing composition supply flow rate: 30 mL / min Polishing time ： 7min

The thickness of the aluminum substrate after polishing was measured, and the rate of thickness reduction was determined from the change in the thickness of the aluminum substrate before and after polishing. The relative speed (relative value) was determined based on Comparative Example 1. I asked. Further, the center line roughness Ra and the surface defect of the surface of each substrate after polishing were measured according to the following methods. The relative roughness (relative value) was determined based on Comparative Example 1. The results are shown in Table 1.

[Center line average roughness Ra] Measured under the following conditions using a tally step manufactured by Rank Taylor Hobson. Needle size: 25μm × 25μm, high-pass filter: 80μ
m, Measurement length: 0.64mm

[Surface Defects (Scratch)] Using an optical microscope observation (differential interference microscope), the surface of each substrate was measured at six points at 60 ° intervals at a magnification of × 50. The scratch depth was measured with Zygo (manufactured by Zygo). The evaluation criteria are as follows. S: 0 scratches exceeding a depth of 50 nm / 1 visual field A: Scratches exceeding a depth of 50 nm are less than 0.5 on average / 1 visual field B: Scratch exceeding 50 nm depth is an average of 0.5 or more and less than 1 visual field / 1 visual field C : One or more scratches with a depth of more than 50 nm on average / one visual field

[0038]

【table 1】

From the results shown in Table 1, when the polishing liquids obtained in Examples 1 to 7 were used, the polishing liquid was more polished than when the polishing liquids obtained in Comparative Examples 1 and 2 were used. It can be seen that a substrate to be polished having a high polishing speed, small surface roughness, few scratches and a good polished surface can be obtained.

[0040]

According to the present invention, the polishing rate is improved,
Provided are a polishing composition, a method for polishing a substrate to be polished, and a method for manufacturing a substrate for precision parts, which can reduce the surface roughness without causing surface defects on the object to be polished.

Claims (3)

[Claims] 1. A polishing composition comprising an alkylsulfonic acid having 1 to 4 carbon atoms or a salt thereof, an abrasive, and water. 2. A method for polishing a substrate to be polished, comprising polishing the substrate to be polished using the polishing composition according to claim 1. 3. A method for manufacturing a precision component substrate, comprising the step of polishing a substrate to be polished using the polishing composition according to claim 1.