JPS62285976A - Abrasive composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an abrasive composition. More specifically, the present invention relates to an abrasive composition useful for precision polishing of semiconductor substrates, thin-film magnetic head substrates, optical components such as optical fibers and laser mirrors, magnetic disk substrates, and the like.

[Conventional technology]

Hitherto, a wide variety of abrasives have been known. For example, in Japanese Patent Publication No. 53-75≦, there is a dispersion of abrasive powder such as alumina and silica sol in water and/or a water-soluble organic solvent. An abrasive consisting of: However, although this abrasive is suitable for polishing glass plates and the like, it is not suitable for precision polishing of semiconductors and the like which require a high degree of polishing precision.

On the other hand, in recent years, colloidal dispersions of silicic anhydride have been in increasing demand for use in polishing semiconductor materials such as silicon wafers, and as abrasives for semiconductor materials where slight surface roughness can cause significant deterioration in performance. polishing performance,
There is a demand for products with excellent handling properties, and this trend is increasing more and more.

In general, methods for producing silica particles are broadly divided into wet methods and dry methods.The shape of the particles obtained by the wet method is generally irregular and angular, whereas that of the dry method. is a roughly spherical particle with a rounded shape. Both types of abrasive grains are used in abrasive materials for semiconductor materials, but in the case of polishing using mechanochemical reactions, dry silicic anhydride particles, which have a rounded, roughly spherical shape, are more effective in polishing. It is known that the surface quality is improved and is preferable (see, for example, Japanese Patent Publication No. 7-20310). Anhydrous silicic acid produced by a dry method is particularly preferred as abrasive grains for abrasives because it does not contain alkali metals such as Na and can be of high purity. However, since the silicic anhydride produced by the dry method has a large aggregation and thickening effect, it has the disadvantage that it becomes gelatinous at a silicic acid anhydride concentration of 70 wt4 or more and cannot be used as an abrasive.

On the other hand, at a low concentration of 10 wt% or less, silica sediments. For the purpose of preventing such sedimentation, for example, Japanese Patent Application Laid-Open No. 1983-1985 Hiro-/2? ? No. 90 describes the inclusion of water-soluble carboxypolymethylene rubber or xantham rubber, and the publication also describes the inclusion of water-soluble cellulose derivatives. However, with this method of suppressing silica sedimentation by adding an anti-settling agent such as a water-soluble organic polymer, the effect could only be achieved by using a large amount of the anti-settling agent, or the effect could not be achieved. Even if it were, the slurry would become viscous, and the slurry would be contaminated with a large amount of organic matter, which is not desirable as an abrasive.

[Problem that the invention seeks to solve]

The present invention solves such problems and provides an aqueous dispersion containing silicic anhydride and alumina, which has a low viscosity even at high concentrations and does not cause particles to settle even without adding an anti-settling agent such as a water-soluble organic polymer. The present invention provides an abrasive consisting of:

[Means for solving problems]

The gist of the present invention is to use aqueous silicic acid anhydride, which is obtained by surface treating alumina and silicic anhydride produced by a dry method, and has a surface silanol group density in the range of 0.3 to 3 on the /θθP side. An abrasive composition characterized in that it is contained in a solvent.

The present invention will be explained in more detail below.

The silica used in the present invention is limited to silicic anhydride produced by a dry process. As mentioned above, methods for producing silica particles are broadly divided into wet methods and dry methods. Silica particles produced by the wet method are made of hydrated silicic acid and have the same surface area as those produced by the dry method. The particle size is larger than that of anhydrous silicic acid particles, and the moisture absorption rate is also high, so it is not suitable as the silica used in the present invention.A dry method for producing silicic acid is to heat a silicon halide such as silicon tetrachloride in a high-temperature burner flame. method by gas-phase reaction of silicon tetrachloride, ammonia, and steam, method by thermal decomposition of organosilicon compounds such as tetramethoxysilane, combustion of silicon fine powder, combustion of silicon sulfide, and natural anhydrous silicic acid. Various methods can be used, such as arc heating a mixture of coke and coke to reoxidize, but the silicic anhydride used in the present invention is not particularly limited by its manufacturing method. Particularly preferred, however, is silicic acid anhydride, called ahumed silica, obtained by high-temperature hydrolysis of silicon halides.

The silicic anhydride used in the present invention has a specific surface area of 10 to 00 rr? /f, preferably /00~j00d/
f, particle size Q, θ/μ ~ /μ, preferably 0, O/
~ θI/μ.

Normally, the surface silanol group density of hyposilicic anhydride obtained by a dry process is greater than 10 × 3 silanol groups, but in the present invention, by surface-treating the silicic anhydride obtained by a dry process, , its surface silanol group density is 10 o'h”
Hit 0. J It is necessary to keep it at least 3 and no more than 3. Preferably, the surface silanol group density is 100P.
The number is 0.5 or more and 2.5 or less, more preferably 0
．． More than j = fewer than j pieces.

Methods for reducing the surface silanol group density by surface treatment of silicic anhydride include reacting the silanol groups with various coupling agents, esterifying the silanol groups with alcohol, and dehydrating and condensing the silanol groups by heating. Examples include methods. Among these, when attempting to reduce the number of silanol groups by introducing an organic group by reacting a coupling agent, alcohol, etc. with the silanol group, the hydrophobicity is too strong and it cannot be wetted by aqueous solvents. Since it may be difficult to disperse uniformly during summer, consideration should be given to reducing the amount of coupling agent, alcohol, etc. to a certain extent while keeping the surface silanol group density within the range of the present invention. is necessary. As a guideline for such treatment, it can be determined based on the organic carbon content in the silicic anhydride into which organic groups have been introduced, as measured by an organic element analyzer.

Coupling agents used to reduce the surface silanol group density of silicic anhydride include silane coupling agents such as methyltrimethoxysilane and hexamethyldisilazane, acetalkoxy7aluminum diisopropylate, etc. Aluminum-based coupling agents, organic titanium-based camping agents such as inpropyl triisostearoyl titanate, organic phosphorus-based coupling agents such as dibutyl cometallyloyloxyethyl phos7ate, and the like. When an organic group is introduced into silicic anhydride by reacting a coupling agent with a silanol group to bring the surface silanol group density within the range of the present invention, the total organic group in silicic anhydride after the treatment is If the carbon content is 3 wt% or more, the hydrophobicity is strong and it is difficult to uniformly disperse it in an aqueous solvent, so the total organic carbon content should be 0.7~! ,0vrt%
It is preferable to set it as the range of. The treatment method using a coupling agent is not particularly limited, and includes ordinary liquid phase treatment,
Gas phase treatment can be applied.

In the case of reducing the surface silanol group density of silicic anhydride with alcohol, examples of the alcohol include methanol, ethanol, n-propanol, 180-propanol,
Number of carbon atoms in n-butanol, -butanol, etc./~/? straight-chain or branched saturated-hydric alcohols. When the surface silanol group density is within the range of the present invention by introducing an organic group into silicic anhydride through an esterification reaction between an alcohol and a silanol group, the above-mentioned total organic carbon content fk in the silica is set to θ, / It is preferable to set it as the range of -t,o wt%. d, those exceeding 0 wt% are strongly hydrophobic and difficult to disperse in aqueous solvents.

The preferred treatment method is gas phase treatment, and the temperature is preferably higher than the boiling point of the alcohol used in the treatment and lower than 350°C.

When reducing the surface ylanol group density If of silicic anhydride by dehydrating and condensing silanol groups by heating, simply 30
It may be heated to θ°C or higher, preferably 500°C or higher.

In short, regardless of the treatment method, it is sufficient that the final surface silanol group density of the silicic anhydride falls within the range of the present invention.

However, when the surface silanol group density exceeds 0.3/100X2, the higher the total organic carbon content in the silicic anhydride, the lower the hydrophilicity, and when dispersed in an aqueous solvent,
Since the viscosity tends to decrease, the higher the total organic carbon content within the above range, the lower the viscosity, which is preferable.

When silicic anhydride having a surface silanol group density outside the range of the present invention is dispersed in an aqueous solvent, high viscosity of the dispersion or sedimentation of the silicic anhydride is observed, which is not preferable. In particular, when using a coupling agent to reduce the surface silanol group density, if the density becomes less than (7,J pieces/10oX!), viscosity and thixotropy will develop, which is undesirable.The reason for this is not clear, but Because it is extremely hydrophobic, it is presumed that a hydrophobic bonding force is acting, which is different from the original hydrogen bonding force.

In order to measure the 7-ranol groups on the surface of the silicic anhydride thus obtained, various methods can be used to quantify them using their reactivity, but in the present invention, silicic anhydride determined by the BET method using N2 adsorption The specific surface area of and silicic anhydride are expressed by the following reaction formula (1
) can be determined based on the following calculation formula from the quantitative value of hydrogen generated by reacting with LiA][4 by gas chromatography.

Geoyasan445:5i-0)4+ Li1H4u8l-0-Li
+ (-81-0 entered...+≠H↑(1) N: Avogadro's constant g, 0.2J and LiAl1'
Amount of hydrogen generated in reaction 14 □ (mo1/l) On the other hand, alumina, which is another component of the abrasive dispersion of the present invention, is a brown alumina obtained by melting and reducing alumina ore (gawoxide) in an electric furnace. Alumina abrasive grains, white alumina abrasive grains obtained by melting high purity alumina in an electric furnace, etc. are used. The crystal form of alumina can be α, β, γ, etc., but α-alumina is particularly preferred. There are no particular limitations on the particle size distribution, particle shape, surface hydroxyl group density, etc. of the alumina abrasive grains, and any commercially available alumina abrasive grains can be used, depending on the material to be polished. However, it is desirable to avoid mixing coarse particles into the abrasive composition because it causes scratches on the surface of the material to be polished.The average particle size is usually 0.07 to 3μ, preferably 0. .0hiro~/
It is best to use alumina abrasive grains of μ size.

The aqueous solvent in which the silicic anhydride and alumina are dispersed means an aqueous solution containing only water or an organic solvent soluble in water. Examples of water-soluble organic solvents include alcohols such as methanol, ethanol, isopropanol, and glycerin, ketones such as acetone, esters such as methyl acetate, organic carboxylic acids such as formic acid and acetic acid, These include organic amines such as dimethylamine, aldehydes such as formalin and acetaldehyde, dioxane, and tetrahydrofuran. When the aqueous solvent is a mixture of water and an organic solvent, the ratio of organic solvent to water differs depending on the type of organic solvent, but the amount that forms a uniform layer with water is sufficient, and there are no particular limitations on water-absorbing solvents. Water and/or alcohol are preferred, and water alone is particularly preferred.

The method for preparing the abrasive composition containing silicic anhydride and alumina in an aqueous solvent of the present invention is not particularly limited, but may include mixing an alumina sol into an aqueous dispersion of silicic anhydride, or Preferably, it is prepared by dispersing and mixing alumina particles in an aqueous dispersion.

An aqueous dispersion of silicic anhydride is made by adding the above-mentioned silicic anhydride to the above-mentioned aqueous solvent! It is obtained by dispersing it so that it contains ~jo wt%.

The silicic anhydride is uniformly dispersed and mixed in the aqueous solvent using a conventional stirrer, homomixer, high shear blender, turbine mixer, or the like. 2. If the silicic anhydride is poorly dispersed in the aqueous solvent, it may tend to settle or have an abnormally high viscosity. Therefore, a high shear type dispersion machine is used to make the suspension uniform. It is desirable to use

In addition, when using alumina sol, the dispersion medium for alumina particles is the same as the above aqueous solvent, but especially water and/or
Alternatively, alcohol is preferable, and the proportion of alumina contained in the alumina sol is about /θ to HiroQ% by weight.

Mixing of the aqueous dispersion of silicic anhydride and alumina sol or alumina particles is carried out by using an ordinary stirrer, homomixer, etc., in the same manner as dispersing silicic anhydride in an aqueous solvent.
Mix.

The ratio of alumina to silicic anhydride in the thus obtained abrasive composition containing silicic anhydride and alumina in an aqueous solvent depends on the type of material to be processed during polishing, polishing pressure, fixed plate, rotation speed, etc. The amount of bu-rOX varies depending on the polishing conditions, but the type of material to be processed,
Depending on the processing conditions, it can be further diluted with water before use.

The abrasive composition of the present invention may optionally contain abrasive grains such as zirconium oxide and cerium oxide, organic amines such as diethylamine as a pH adjuster, bases such as caustic soda, ammonium hydroxide, and ammonia, or nitric acid, It is also possible to add organic or inorganic acids such as acetic acid.

[Effect]

The abrasive composition of the present invention is used for polishing metals such as silicon wafers. As the polishing method, a method using a commercially available polishing or polishing machine is usually applied.

The amount of abrasive used, polishing pressure, polishing speed, polishing time, etc. are appropriately selected depending on the type of material to be processed, the required surface finish, etc.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited in any way by the following Examples.

Incidentally, the surface silanol group density was measured by the following method.

The anhydrous silicic acid is dried under reduced pressure at a temperature of 2θ° C. and a pressure of less than jwnHsF for 3 hours to remove adhering moisture. Next, the silicic anhydride/0P is added to the dehydrated dioxane 30 resistant, and a slurry liquid is prepared by thoroughly dispersing the slurry using ultrasonic waves or the like.

A cojd glass Erlenmeyer flask was used as the reaction tank.
There are 0. ．． 3 f LvLiAIH, and 10 ml of dehydrated dioxane are added and stirred, and the silicic anhydride dispersion slurry is taken into a syringe in 2/ml portions, and then injected into the reaction tank and reacted. The silanol groups on the silicic anhydride surface and LiA
The amount of hydrogen generated during the reaction of lH4 is determined by gas chromatography to determine the amount of hydrogen iX'moli generated.

The reaction in this case is expressed as the reaction formula (1) above, and according to this reaction, silanol! 7 hydrogen molecules per /6
occurs. Separately, by the B, T, method by N2 adsorption,
Specific surface area ACrr of silicic anhydride? /? ], the surface silanol group density can be determined using the following equation.

N: Avogadro's constant O, 0.23 x 1023 Reference example / Nippon Aerosil Co., Ltd.'s Aerosil Well 200 as dry silicic acid (average/next particle size, /, < mμ, specific surface area -00
dl? , silanol group density θ/100p, total organic carbon content 0.03 wt%), and using methyltrimethoxysilane, a silane coupling agent,
The powder obtained by gas phase treatment at 100°C for 70 minutes has a total organic carbon content of 0. jWtlg, the surface silanol group density was 2.5//00 A.

Table 7 shows the viscosities of slurry liquids of various concentrations obtained by dispersing this treated silicic anhydride in deionized water. These materials were effective even after 7 months as sedimentation of particles was observed.

Reference example/Same dry silicic anhydride as Reference example/(Aerosil@aOO)
The powder obtained by treating with n-butyl alcohol at 230°C for 70 minutes in a normal pressure system has a total organic carbon content of 0. Fw
t, the surface silanol group density is 7. It was 3 pieces/100A.

Table 1 shows the viscosities of slurry liquids of various concentrations obtained by dispersing this treated silicic anhydride in deionized water. No sedimentation of particles was observed in these slurry liquids even after 77 months.

Reference Example 3 Same dry silicic anhydride as Reference Example (Aerosil #, 2oθ
) was heat-treated at 20θ°C for 2 hours, and the powder had a total organic carbon content of 0.02 wt% and a surface silanol group density of 2@//θ0A.

Table 1 shows the viscosities of slurry liquids of various concentrations obtained by dispersing the treated silicic anhydride in deionized water and adjusting the pH to /θ,j with aqueous ammonia.

No sedimentation of particles was observed in these slurry liquids even after 7 months.

Reference example μ Same dry silicic anhydride as Reference example/(Aerosil #200)
, hexamethyldisilazane (CH3)3s1-NH8
The powder obtained by gas-phase treatment with 1(CH3)s vapor at 1.200°C for 30 minutes has a total organic carbon content of 0.5%/wt% and a surface silanol group density of 0.000%. r pieces/100).

The table below shows the viscosity of slurry liquids of various concentrations obtained by dispersing this treated silicic anhydride in a 50 volume aqueous solution of isopropanol.
It was shown to.

No sedimentation of particles was observed in these slurry liquids even after several months.

Comparative Reference Example/ Same dry silicic anhydride (Aerosil #soo') as Reference Example/
) @ As a result of directly dispersing it in deionized water, S10! Concentration / Owt% What is the viscosity (℃) of the slurry liquid? r, /
It had a very high viscosity of 00 Q,p. or,
In the J0wtL% slurry liquid, gelation was significantly uncontrollable.

Viscosity of low concentration slurry liquid with B102 concentration jet% (Jr
℃) had a low viscosity at /Jc,p, but after 3 days most of the particles had settled.

Comparison reference example - Same dry silicic anhydride as Reference example (Aerosil#koOθ)
Hexamethyldisilazane (CH,)s 5iNE-8
The powder obtained by vapor phase treatment with t(cH3)s vapor at 350°C for 30 minutes has a total organic carbon content of 3.0 wt% and a surface silanol group density of 0. ．． It was 2 J pieces/ / 00 A.

This treatment uses silicic anhydride for isopropanol! As a result of dispersing the ice-water solution in θ volume, t! c, p, and similarly 20 wt%V
The slurry liquid showed 7,000 c,p.

The B102 concentration 10wt% female slurry solution had a relatively low temperature of 1 degree, but some of the particles settled and crumbled after 3 days.

The surface silanol group density obtained in Example/Reference Example/ is Jj pieces/
Alumina sol As-! is added to an aqueous dispersion (dispersion medium: water)/l containing /00 A of silicic anhydride at /Owt%. 20
(Manufactured by Yasan Kagaku Kogyo Co., Ltd., At!03.20vrt%)
/ and 2 tons of water was used as an abrasive to polish a silicon wafer.

As for the polishing method, a polishing table made of soft metal and a semi-hard type polishing cloth are used, the silicon wafer is fixed to a wafer attachment block with wax, and the above abrasive is dripped at a constant speed at a ratio of "Ornl/rriy+". While polishing table! ORPM,
Polishing was performed for 70 minutes by rotating the wafer-attached block at 200 RI'M while applying a pressure of 10 oy/-. The surface roughness of the polished wafer is Rmax = 0.
/μ showed a high degree of surface finish.

Comparative Example / In contrast to /l, a mixture of alumina sol AB-j-20 (manufactured by Nichichi Kagaku Kogyo ■, Al2O3CoOwt%) yt and water 2t was used as an abrasive, and many clutches were generated as in Example 5. Ta.

Example λ The surface silanol group density obtained in Reference Example/ is 2.5/
α-Alumina (AES-T: manufactured by Sumitomo Chemical Co., Ltd., center particle size 0.3μ) was dispersed and mixed in an aqueous dispersion (dispersion medium: water) containing 100A of silicic anhydride. , an abrasive was prepared.

Gallium-arsenic compound semiconductor substrates are polished using a double-sided polisher and a semi-node type polishing cloth.
The wafer was fixed to the wafer attachment block with wax, and the abrasive was dropped at a constant speed at a rate of /θWLl/mis while the polishing table f I/ORPM and the wafer attachment block were placed at 200? /θRP while applying 7cm pressure
Polishing was performed for 10 minutes by rotating with M.

The average surface roughness of the semiconductor substrate before polishing treatment is o, o l
Asμt, but the average surface roughness after polishing was 0.
It was 0θ/μm.

Comparative Example 2 α-Alumina (Am!: S-T: Sumitomo Chemical Co., Ltd.,
Center particle size θ, 3μ) 10ot and nitric acid 15mm as a dispersion aid. were dispersed and mixed in water/l to prepare an abrasive.

When the abrasive was used to polish a gallium-arsenic compound semiconductor substrate in the same manner as in Example 1, the average surface roughness was 0.0 hμ〆 to 0, θ≠Oμ〆. .

〔Effect of the invention〕

The abrasive of the present invention is made by dispersing silicic anhydride and alumina, which are obtained by surface treating silicic anhydride produced by a dry method and having a surface cranol group density in a specific range, in an aqueous solvent. When used as a precision abrasive for semiconductor substrates such as wafers and various metals, it has the excellent effect of providing a high degree of polishing precision.

Furthermore, since the abrasive of the present invention uses the specific silicic anhydride as mentioned above, it has good storage stability. Even after several months, the silicic acid anhydride particles do not settle, or even if some do. Not only does it have the favorable handling properties of being easily dispersed into a uniform slurry with slight shaking, but it also prevents silica from settling sufficiently without the addition of water-bathable polymers, etc., which were conventionally added to prevent the settling of silica. It is effective and therefore preferable as an abrasive, and also has the advantage of avoiding contamination with organic matter.

Sender: Mitsubishi Chemical Industries, Ltd. Representative Patent Attorney Hase - (7 others)

Claims (2)

[Claims] (1) Alumina and surface silanol group density is 100 Å^
An abrasive composition characterized in that an aqueous solvent contains silicic anhydride produced by a dry method in a range of 0.3 or more and 3 or less per 2. (2) Silicic anhydride is produced by a dry method and is partially hydrophobized to have a surface silanol group density of 100 Å^2
The abrasive composition according to claim 1, wherein the abrasive composition has a range of from 0.3 to 3 pieces per abrasive composition.