JPH07157367A - Production of high purity beta-silicon carbide sintered compact for device for producing semiconductor - Google Patents

Abstract

PURPOSE:To ensure high purity, suppress the production of particles and improve durability and high temp. strength by sintering a powdery mixture of specified beta-SiC powder with a sintering aid at high temp. and pressure. CONSTITUTION:A mixed soln. contg. a liq. silicon compd., a liq. org. compd. having a functional group, forming carbon under heating and contg. <=1ppm impure elements and a polymn. or crosslinking catalyst contg. <=1ppm impure elements is dried, hardened, carbonized by heating at 700-1,100 deg.C in a nonoxidizing atmosphere and burnt at 1,600-2,000 deg.C in a nonoxidizing atmosphere to obtain beta-SiC powder having a ratio of 2.3-2.5 as the molar ratio of C to Si and 0.5-20mum average particle diameter. This SiC powder is mixed with 1-30wt.% superfine SiC powder having 10-100nm average particle diameter as a sintering aid and the resultant mixture is sintered at a high temp. of 1,900-2,000 deg.C under pressure to produce the objective beta-SiC sintered compact having <=0.5OMEGA.cm specific resistance.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention is highly pure and durable,
High-purity β for semiconductor manufacturing equipment with few particles
High-purity β-type silicon carbide for semiconductor manufacturing equipment that can be used for heaters used in the semiconductor industry, heat-resistant parts that require high strength, peripheral parts for highly corrosive gases, electrodes for etchers, etc. Regarding a sintered body.

[0002]

2. Description of the Related Art Conventionally, silicon carbide has been used as a heat resistant material, but it is known as a refractory material because it is a covalent substance. Known sintering methods of silicon carbide include a reactive sintering method (RSSC method), an atmospheric pressure sintering method, and a hot pressing method.

The reactive sintering method is as follows: Raw material mixture (silicon carbide powder + carbon powder) 1. Molding 3. 3. Reaction sintering and 4.
If necessary, each step of post-processing is included. The feature of this method is that the carbon particles of the compact are silicified in the sintering step, and there are advantages that the dimensional change of the compact is small and a sintering aid is not required. Since the body is easy to obtain, it is used in various jigs such as wafer boats used in the semiconductor industry. However, the sintered body made by the RSSC method contains metallic silicon and is not suitable for a heater or a jig used in a field requiring high strength.

Further, the atmospheric pressure sintering method is not suitable for use in the semiconductor industry field because it is necessary to use boron or the like as a sintering aid.

Further, hot press method (including HIP method)
Is known to have physical properties of a highly heat-dissipating sintered body produced by using silicon carbide ultrafine powder as a sintering aid (FC re
port 11, No2 P40-44 [199
3]). However, the highest purity U listed here
It is known that even the SC grade contains several ppm of iron and alkali metal impurities, which are most harmful to semiconductors, and cannot be used in the semiconductor industry without surface coating such as CVD coating.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a β-type silicon carbide sintered body which has high strength at high temperature and can be used in the semiconductor industry without surface coating.

[0007]

The method for producing a high-purity β-type silicon carbide sintered body according to the present invention comprises a liquid silicon compound and a liquid organic compound which has a functional group and produces carbon by heating. Average particle size obtained by curing and drying the mixed solution with the catalyst, heating and carbonizing the obtained solid matter in a non-oxidizing atmosphere, and then calcining the obtained intermediate substance in a non-oxidizing atmosphere. Β-type silicon carbide powder (A) having a diameter of 0.5 to 20 μm, and an average particle diameter of 10 to 100 as a sintering aid.
β consisting of mixing silicon carbide ultrafine powder (B) having a thickness of nm and sintering the resulting mixed powder under high temperature pressure
In the method for producing a type silicon carbide sintered body, the raw material and the catalyst are substantially free of impurity elements, and the intermediate substance has a carbon / silicon molar ratio of 2.3 to 2.5, The ratio of the B component contained in the mixed powder is 1 to 30% by weight, and the specific resistance of the β-type silicon carbide sintered body is 0.5.
Ω · cm or less and the content of each impurity element is 1 ppm
It is characterized by the following.

That is, the present inventors have found that 70% is required to obtain the above-mentioned high-purity and high-strength silicon carbide sintered body.
It was considered necessary for the β-type silicon carbide powder raw material (A) having the above content to have high purity. That is,
In order to use it for jigs in the semiconductor-related field, we have thoroughly modified it from the manufacturing stage of component A to prevent impurities from entering.
Further, by making the same improvements in the sintering step, a manufacturing method for obtaining a high-purity β-type silicon carbide sintered body in which each impurity element is 1 ppm or less was established, and the present invention was completed.

[0009]

In the high-purity β-type silicon carbide sintered body, it is desired to have high strength and high corrosion resistance, but the silicon carbide sintered body obtained by the reaction sintering method contains metallic silicon. However, the high-purity β-type silicon carbide sintered body obtained by the production method of the present invention uses a sintering aid as a silicon carbide By making it into a fine powder, it is possible to obtain a sintered body that is substantially free of impurity elements and to improve the durability against corrosive gas, arc discharge, etc. It has an excellent effect that it can be used as a heating element or the like.

[0010]

The present invention will be described in detail below.

In the present invention, examples of the liquid silicon compound include alkyl silicates such as methyl silicate and ethyl silicate, aqueous solutions of silicic acid polymers, ester solutions of organic compounds having a hydroxyl group and silicic acid, and the like.
Ethyl silicate monomers and oligomers are preferred.

In the present invention, as the liquid organic compound having a functional group and generating carbon by heating, an organic compound having a particularly high residual carbon rate and capable of being polymerized or crosslinked by a catalyst or heating, such as phenol resin or nitrile. Resin, furan resin, polyimide resin, styrene resin, xylene resin,
Polyphenylene oxide, polyphenylene sulfide,
Examples thereof include resin (polymer) monomers and prepolymers such as polyaniline, and a resol-type or novolac-type phenol resin is preferable.

In the present invention, when a phenol resin is used as a raw material, the polymerization or cross-linking catalyst capable of being uniformly solubilized in the raw material is preferably an acid such as toluenesulfonic acid, hydrochloric acid, sulfuric acid or oxalic acid. More preferred is toluene sulfonic acid. When using monomers or oligomers of nitrile resin, ammonium persulfate,
Radical polymerization initiators such as hydrogen peroxide, various hydroperoxides, alkyl peroxides, peroxide esters, and azo compounds are preferable. Also, when other organic compounds are used, generally used polymerization or crosslinking catalysts are preferable.

Further, the mixing ratio of these liquid silicon compound and high-purity organic compound as a carbon source is such that a precursor substance obtained by adding a catalyst to both and curing and drying is carbonized in a non-oxidizing atmosphere. The molar ratio of carbon to silicon is 2.3 to 2.
It is decided to be 5. Further, the amount of carbon remaining in the component A is preferably 3% or less, and if it is 3% or more, it becomes an obstacle to sintering.

In the present invention, the precursor substance obtained by polymerizing or cross-linking the raw material is heated and carbonized in a non-oxidizing atmosphere, and the carbonization temperature is 700 to 1100 ° C., preferably 800. ~ 1000 ° C is adopted. The intermediate product obtained by carbonizing the precursor substance is fired at a higher temperature in a non-oxidizing atmosphere, and the firing temperature is 1600 to 2000 ° C, preferably 1600 to 1900 ° C. Is adopted.

The matters related to impurities, which are important elements in the present invention, are described below.

The term "substantially free of an impurity element" as used in the present invention is defined as the content of each impurity element being 1 ppm or less, preferably 0.5 ppm or less, and more preferably 0.1 ppm. . However, the firing temperature (1600
This does not apply to elements or compounds of elements that evaporate at temperatures of up to 2000 ° C.

Further, for the catalyst, additives, solvent (including water), etc. used in the present invention, it is necessary to use a high-purity product substantially free of impurities. In addition, raw materials and products are preferably handled in a clean booth of class 1000 or lower.

The term “impurity element” as used herein means an element of Ia (excluding hydrogen) to Group IIIa, an element of Group Ib to Group VIIb, an element of Group VIII, an element of Group IVa having an atomic number of 32 or more, and An element of atomic number 33 or higher in the Va group.

The sintering of the powder will be described in detail below.

A component of 10 to 100 n produced by a vapor phase method
A dry or wet ball mill is suitable for the method of mixing 1 to 30% by weight of the silicon carbide ultrafine powder (B) of m. Here, it is necessary to use a container and a ball of resin (for example, nylon, urethane, etc.) that does not contain impurity elements and the like.
Further, since ultrafine silicon carbide is easily oxidized, it is preferable to replace the container with an inert gas. As in the former case of the wet method, it is preferable to carry out the drying, under an inert gas, or under vacuum.

The addition amount of the B component in the mixed powder of the A component and the B component is set to 1 to 30% by weight. 1% by weight is not enough to sinter the A component. This is because if the content is more than 100%, the bulk density of the B component is small, which makes it extremely difficult to mold and sinter.

As a method for heating and sintering the obtained mixture, a hot pressing method and a hot isostatic pressing method (HIP method) are used.
And the like.

The sintering temperature is preferably 1900 to 2000 ° C. In particular, when obtaining a sintered body having a specific resistance of 0.1 Ω · cm, it is preferable to sinter at a high temperature of 2000 ° C. This is because the surface oxide of the ultrafine silicon carbide powder (B) is reduced by the carbon generated by sublimation of β-type silicon carbide. Further, the sintering is preferably performed in a non-oxidizing atmosphere or an inert gas.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples as long as the gist of the present invention is not exceeded.

(Example A1) S as a liquid silicon compound
High-purity ethyl silicate 690 with iO ₂ content of 40%
g and 300 g of a high-purity liquid resol-type phenolic resin having a water content of 20%, 120 g of a 25% aqueous solution of high-purity p-toluenesulfonic acid as a catalyst was added and cured and dried to give a homogeneous resinous solid. Obtained. This was carbonized at 900 ° C. for 1 hour in a nitrogen atmosphere. The carbon / silicon molar ratio of the obtained carbide was 2.4 based on elemental analysis. This carbide was heated to 1900 ° C. in an argon atmosphere, heated, and held for 4 hours to carry out silicon carbide reaction and crystal grain growth. The color of the obtained powder was light green. Also, X
The crystal form of silicon carbide by line diffraction was β type (cubic crystal). Table 1 shows the results of the impurity analysis (ICP-mass spectrometry and flames atomic absorption method) of the component A.

[0027]

[Table 1]

Next, 5% by weight of silicon carbide ultrafine powder (average particle size = 0.05 μm: made by Sumitomo Cement) was added to the component A, dispersed in ethanol, and a nylon container and a nylon ball with an iron core were used. Ball milling for 24 hours. This was dried under reduced pressure and made into a disk shape having a diameter of 50 mm by a normal uniaxial press. Further, this molded body was heated in a vacuum to 1650 ° C. in a hot press machine, and then under an argon atmosphere, a pressure was 450 Kg / cm ² , and a sintering temperature was 19
Sintered at 50 ° C. for 2 hours. Table 2 shows the results of three-point bending strength and specific resistance obtained by surface-polishing the obtained disk having a thickness of about 1.5 mm with diamond, followed by thorough washing and impurity analysis.

[0029]

[Table 2]

Example 2 Example 1 was repeated except that 15% by weight of commercially available ultrafine silicon carbide powder was added to the component A obtained in Example 1 and the mixture was sintered at a sintering temperature of 1950 ° C. for 2 hours. Similarly, a sintered disk was prepared and the same test was conducted. The results of the impurity analysis, the three-point bending strength and the specific resistance are shown in Table 2.

Example 3 Example 1 was repeated except that 28% by weight of commercially available ultrafine silicon carbide powder was added to the component A obtained in Example 1 and the mixture was sintered at a sintering temperature of 1950 ° C. for 2 hours. Similarly, a sintered disk was prepared and the same test was conducted. The results of the impurity analysis, the three-point bending strength and the specific resistance are shown in Table 2.

(Comparative Example 1) The same as Example 2 except that a commercially available high-purity silicon carbide powder (manufactured by Stark Co., Ltd .: the result of impurity analysis is shown in Table 1) was used in place of the component A of Example 1. Then, a sintered disk was prepared and the same test was conducted.
The results of the impurity analysis, the three-point bending strength and the specific resistance are shown in Table 2.

(Comparative Example 2) Component A 1 obtained in Example 1
High-purity novolac phenolic resin 15 against 00g
g, and dry mixed with a ball mill similar to Example 1 to 1
I went for 2 hours. A portion of this was placed in a uniaxial press that can be heated and heat cured under pressure at 60 ° C. for 10 minutes. The obtained molded body had a size of 50 mmΦ and a thickness of 2 mm. This molded body was placed in a furnace, heated at 900 ° C. at a temperature rising rate of 25 ° C./hour in an argon atmosphere, held for 45 minutes, and then cooled in the furnace. This carbonized compact was brought into contact with high-purity silicon melted at 1500 ° C. in an argon atmosphere, and held for 1 hour for reaction sintering. The silicon adhering to the surface of this sintered body was removed, the surface was further washed with high-purity hydrochloric acid and high-purity nitric acid, and the results of impurity analysis and the three-point bending strength and specific resistance are shown in Table 2.

[0034]

The high-purity β-type silicon carbide sintered body obtained by the production method of the present invention has a high purity which is hardly obtained by the conventional sintering method and can be used as a resistance heating element.
It can be applied as a heat-resistant jig or heating element in the semiconductor industry.

Claims (1)

[Claims] 1. A solid solution obtained by curing and drying a mixed solution of a liquid organic compound having a functional group, which has a functional group to generate carbon by heating, and a polymerization or crosslinking catalyst, and obtains the obtained solid under a non-oxidizing atmosphere. Beta-type silicon carbide powder (A) having an average particle size of 0.5 to 20 μm obtained by further heating and carbonizing the obtained intermediate substance and then firing the obtained intermediate substance in a non-oxidizing atmosphere.
And a silicon carbide ultrafine powder (B) having an average particle size of 10 to 100 nm as a sintering aid, and then sintering the resulting mixed powder under high temperature pressure. In the method for producing a sintered body, the raw material and the catalyst are substantially free of impurity elements, and the carbon / silicon molar ratio of the intermediate substance is 2.3 to.
2.5, the proportion of the B component contained in the mixed powder is 1 to 30% by weight, the resistivity of the β-type silicon carbide sintered body is 0.5 Ω · cm or less, and each impurity A method for producing a high-purity β-type silicon carbide sintered body for a semiconductor manufacturing apparatus, characterized in that an element content is 1 ppm or less.