JP3467723B2 - Method for manufacturing silicon carbide sintered body member - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a silicon carbide sintered body member, and more particularly, to a metal from the surface of the sintered body even when the silicon carbide sintered body member is used in a wide temperature range. The present invention relates to a method for producing a silicon carbide sintered body member in which the emission pollution such as impurities and the emission pollution from the surface of a sintering aid component such as boron used for sintering silicon carbide (SiC) are significantly reduced.

[0002]

2. Description of the Related Art A silicon carbide sintered body is excellent in many physical properties such as heat resistance, denseness, high thermal conductivity, corrosion resistance, strength, and wear resistance, and therefore it is a high temperature structural material such as a heat insulating cylinder and a gas turbine blade. In addition to heating elements, resistors, etc., they are widely used in various applications such as food materials, wear resistant materials, abrasive materials such as grindstones, abrasive materials, and others. The method for manufacturing a silicon carbide sintered body is roughly classified into
There are three methods: self-sintering, reaction sintering, and recrystallization. In reaction sintering, the impregnating material usually contains about 5% by weight or more of Si, etc., so that it is possible to manufacture a sintered body with a high SiC content. Is generally manufactured by self-sintering. However,
Silicon carbide (SiC) is a chemically stable compound having a strong covalent bond property. Moreover, since sublimation and thermal decomposition start at a melting point of 2700 ° C. or higher and 2200 ° C. or higher, silicon carbide powder is self-sintered by itself. Therefore, it is difficult to obtain a good sintered body, and it is usually necessary to add a so-called sintering aid such as boron, carbon, or alumina to the sintering. Regarding the silicon carbide sintered body produced by the self-sintering method, when the contained sintering aid is a boron type, some special ones have a low content rate of 0.05% by weight. Contains about 0.1 to several wt% of boron.

This sintering aid is necessary during the sintering process, but is not necessary after the sintering reaction is completed, and when the sintered body is used as a member, especially under high temperature heating. In some cases, a part of the auxiliary agent remaining on the surface or in the vicinity of the surface migrates inside the sintered body and is released outside the sintered body, which may become a pollution source contaminating the surroundings. For this reason, in the field of precision industry where this kind of contamination is extremely disliked, for example, in the field of semiconductor manufacturing, the silicon carbide sintered material produced by self-sintering has many excellent physical properties described above. However, its use is generally shunned except for special cases from the viewpoint of the above-mentioned impurity emission and contamination, and conventionally, it is almost considered to be adopted as a semiconductor heat treatment member such as a wafer boat and a core tube. I didn't.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention burned despite having many excellent physical properties such as heat resistance, denseness, high thermal conductivity, corrosion resistance, strength and abrasion resistance as described above. Various treatments have been applied to the silicon carbide sintered material in order to suppress the release of the contaminant impurities of the silicon carbide sintered body, which has been rarely considered as a semiconductor heat treatment member due to the peripheral contamination caused by the release of impurities such as auxiliary agents. Then, various studies were conducted on the relationship between the treatment method and the amount of released impurities. As a result, as described in detail below, the surface of the silicon carbide sintered body member is oxidized, the generated oxide film is removed by acid cleaning, and then a specific purification heat treatment is performed, whereby the above-mentioned sintering aid, etc. The inventors have found that the emission of the pollutant (1) from the surface of the sintered body can be reduced to an extremely low level, and have completed the present invention.

Therefore, the object of the present invention is not only to suppress the release of pollutants such as metals, but also to completely release the sintering aid contained in the silicon carbide sintered body from the surface and migration contamination. It is an object of the present invention to provide a method for producing a silicon carbide sintered body member which can be suppressed and can be sufficiently used as a semiconductor heat treatment member.

[0006]

According to the present invention, the surface of a sintering aid-containing silicon carbide sintered body member that has been machined after sintering is washed to remove particles that have adhered, and after drying, The surface of the oxide film is oxidized by heat treatment in an oxidizing atmosphere, the generated oxide film layer is removed by acid cleaning, and then heat purification treatment is further performed in an inert gas atmosphere or a hydrogen chloride-containing gas atmosphere. A method of manufacturing a silicon carbide sintered body member is provided. Further, according to one aspect of the present invention, the surface of the silicon carbide sintered body member that has been subjected to the impurity release suppressing treatment is further subjected to a silicon carbide coating treatment, so that an excellent impurity release suppressing effect is obtained particularly in use in a high temperature range. A method for manufacturing a silicon carbide sintered body that exhibits

According to the method of the present invention, a machined silicon carbide sintered body member is oxidized in an oxidizing atmosphere to form an oxide film layer on the surface, and the formed oxide film is a hydrofluoric acid solution or a hydrofluoric acid. Remove by acid washing with a mixed acid solution of acid and nitric acid,
Then, by a relatively simple treatment operation of heat treatment in an atmosphere of an inert gas such as argon, during use, impurities such as sintering aid components may be released from the surface of the sintered body to pollute the surrounding environment. It is a feature that a general-purpose silicon carbide sintered body having a certain property can be converted into a silicon carbide sintered body having almost no migration of impurities from the surface or emission pollution. The silicon carbide sintered body member manufactured by this method of the present invention, when used as a product, exhibits a remarkable effect of suppressing impurity emission in the temperature range of 400 to 800 ° C.

Further, a silicon carbide sintered body obtained by applying the method of another aspect of the present invention in which the surface of the sintered body member treated by the above method is further coated with silicon carbide by the CVD method or the like, When used in a high temperature range of 900 to 1200 ° C., it exhibits a remarkable effect of suppressing the release of impurities.

In the method of the present invention, the step of oxidizing the surface of the sintered silicon carbide member is a treatment for the purpose of removing the surface machining layer, and the surface machining layer contains only a relatively large amount of impurities. In most cases, the so-called crushed layer is chemically relatively destabilized due to strain and the like caused by mechanical treatment such as grinding and polishing, which makes the layer unstable chemically. The crushed layer varies depending on the processing state, but the thickness is usually on the order of several μm. Therefore, this layer is relatively easily oxidized, and the oxidation is completed in 1200 ° C. for about 2 hours in an oxygen atmosphere.

Then, in the method of the present invention, this surface oxide layer of the sintered body is acid-cleaned with a cleaning liquid such as an aqueous solution of hydrofluoric acid to dissolve and remove it. Fe and A present in this surface-treated layer
Metallic element impurities such as 1, Ni, Cr, etc. and B, C, alumina, and other sintering aid components are not stable because the processed layer (crushed layer) itself is unstable and is highly reactive. When the bound body is used as it is, these impurities tend to be easily desorbed, transferred to the outside, and released. Therefore, in the present invention, the impurities that are likely to migrate are first removed together with the processed surface layer (crushed layer) by the above treatment. In the sintered body produced by the self-sintering method, most of the sintering aid component elements exist in the state of being solid-solved in the SiC crystal grains, or in the state of being trapped in the grain boundary phase. To do.
The surface layer of the sintered body, which appears after removing the oxide layer, has crystals arranged more orderly than the processed surface layer, has a dense microstructure structure, and contains many impurity elements such as auxiliary component elements. Is dissolved in the crystal grains. Silicon carbide (Si
C) The impurity in the crystal phase has a small diffusion coefficient, so that the amount transferred to the outside is very limited.

Next, in the method of the present invention, this sintered member is subjected to a heat purification treatment. This treatment involves relatively moving the grain boundary of the surface crystal phase after removal of the processed layer and microcracks. Is performed for the purpose of removing impurities that are easy to remove, for example, 1200 in an argon (Ar) gas atmosphere.
Treatment at about 2 hours for 2 hours achieves the removal of these easily moved impurities. Further, the same effect can be obtained by the treatment with the gas containing HCl. Generally, in a sintered body such as a silicon carbide sintered body, for example, a sintering aid component such as boron or aluminum element tends to gather at the grain boundaries of the polycrystalline phase during sintering. In the method of the present invention, it is important to remove impurities that are concentrated in the crystal grain boundaries on the surface of the sintered body and are relatively mobile.

The silicon carbide sintered body obtained by the method of the present invention has a remarkable impurity emission amount as compared with a general-purpose sintered body, as will be apparent by referring to the description of Examples below. Will be reduced. Furthermore, in the silicon carbide sintered body member obtained by applying the method of another aspect of the present invention, in which the surface of this treated sintered body is coated with silicon carbide by the CVD method or the like, the surface of a general-purpose silicon carbide sintered body is obtained. When used at 1200 ° C., the amount of released impurities can be reduced to 1 / 1,000 or less in the case of boron and 1/50 or less in the case of Fe as compared with the sintered body coated with silicon carbide.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The silicon carbide sintered body to which the method of the present invention is applied is not particularly limited and is for a member which is self-sintered by an ordinary method and processed into a predetermined shape by cutting, polishing or the like. A sintered body can be used. The silicon carbide sintered body is generally obtained by adding SiC powder particles having an average particle size of about 0.3 μm to several μm to a sintering aid such as boron, boron compound, carbon or carbide, aluminum compound and the like. Add a binder or the like to form a mixture, add water or the like, knead, and mold into a predetermined material shape, and after degreasing 2000 to 22
It is obtained by sintering at a temperature of about 00 ° C.

The sintered material thus obtained is cut into a predetermined shape and subjected to processing such as surface polishing as required to obtain a sintered member. In the case where the sintered body is a semiconductor heat treatment member or the like, it is further washed with an acid such as an aqueous solution of HF + HNO ₃ mixed acid, the surface is cleaned and dried to obtain a member. In order to obtain a good semiconductor heat treatment member in which emission pollution is effectively reduced by applying the method of the present invention to the above sintered body member, a silicon carbide sintered body to which boron is added as a sintering aid is used as a material. It is preferable to use, and it is particularly preferable that the sintered body has a boron content of less than 1%.

In the method of the present invention, first, the surface-treated and acid-cleaned sintered body is heated to a temperature of 600 to 130 in an oxidizing atmosphere such as air, oxygen gas or other oxidizing gas.
Oxidation is performed by heating at a temperature of 0 ° C., preferably 1000 to 1200 ° C. If the oxidation temperature is less than 600 ° C, the oxidation rate is too slow to be practical, and if it exceeds 1300 ° C, there is no problem in oxidizing the sintered body itself, but the heat resistance of the constituent material of the oxidation heating furnace, etc. There is a problem with it, and it is still not practical.

By this treatment, the oxidation reaction represented by the following reaction formula proceeds in the surface layer of the sintered body. 2SiC + 3O ₂ = 2SiO ₂ + 2CO This surface layer oxidation progresses at an oxidation rate of about 0.2 to 0.3 μm / Hr at 1200 ° C. on the surface of a normal sintered body, but 1 to several μm / Hr at the fracture layer. proceed. The surface oxidation is performed to such an extent that an oxide film layer (SiO ₂ layer) having a depth of the surface crushed layer of about several μm or a thickness somewhat deeper than that is formed. For example, the surface oxide film layer is formed in about 2 hours under the processing condition of 1200 ° C. in the atmospheric oxygen gas atmosphere.

Then, the oxide film layer formed on the surface of the sintered body is dissolved and removed by acid cleaning. Examples of the cleaning solution used for the acid cleaning include a hydrofluoric acid aqueous solution,
A silicic acid component-soluble aqueous solution such as a mixed acid aqueous solution of hydrofluoric acid and nitric acid is used, and the acid concentration is, for example, 5 to 40% by weight, preferably 8 to 15% by weight in the case of a hydrofluoric acid aqueous solution.
An aqueous acid solution having a concentration of about wt% is used. The acid cleaning temperature is
Although either normal temperature or heating may be used, for example, when a 10% aqueous solution of hydrofluoric acid is used, the purpose can be sufficiently achieved by washing at normal temperature for about 10 minutes.

The sintered body from which the surface oxide film layer has been removed in this manner is thoroughly washed with pure water and dried, and then heat-purified. In the method of the present invention, this heat purification treatment is
In an inert gas atmosphere such as helium, neon, argon or krypton, the temperature is 1200 ° C. or higher, preferably 120.
Heat treatment at a temperature of 0 to 1800 ° C., or
Processing is performed at the same temperature as above in an atmosphere containing HCl gas. This processing time is, for example, in an atmospheric pressure Ar gas atmosphere,
In the case of 1200 ° C. treatment, it takes about 2 hours. In the case of processing in an inert gas atmosphere, it is preferable to use Ar gas from the viewpoints of gas handling, processing effect and cost. As the HCl-containing gas, HCl-containing gas that uses oxygen gas as a carrier, and H that uses the above-mentioned inert gas such as Ar gas as a carrier
HC using Cl-containing gas, oxygen and inert gas as carriers
1-containing gas etc. can be mentioned.

The treatment in the above-mentioned inert gas atmosphere has an advantage that the surface of the SiC is not altered during purification, and in the gas atmosphere containing the inert gas carrier HCl, there is an advantage that impurities can be easily converted to chloride to be removed. , Sintered body (Si
C) Surface is slightly roughened (gas slightly decomposes SiC)
There is fear. HCl with oxygen and inert gas as carriers
The contained gas has a greater risk of roughening the surface of the sintered body (SiC), but has an effect of completely removing surface contamination faster.

When the sintered silicon carbide member is used in a high temperature range of 800 ° C. or higher, the surface of the sintered silicon carbide member obtained by the above treatment is preferably further subjected to SiC coating. The surface-SiC-coated sintered body of the present invention thus obtained has a temperature of 800 to 1200 ° C.
In the high temperature range of 1, the amount of impurities released is remarkably reduced as compared with the conventional silicon carbide sintered body not subjected to the treatment of the present invention which is directly coated on the SiC surface. This is probably because in the conventional sintered body, a large amount of impurities are released from the surface of the sintered body during the coating process, and the released impurities are transferred to the coat layer to contaminate the coat layer. Impurities are further released to the outside. On the other hand, it is presumed that when the sintered body member treated by the present invention is coated, a clean coat layer can be obtained because there is no contamination during coating.

As a method for forming the SiC surface coat layer on the sintered body which has been subjected to the treatment of the present invention, a known surface coat forming method which is generally used for this type of sintered body may be used.
For example, a chemical vapor deposition method (CVD method), a physical vapor deposition method (P
A VD method), a thermal spraying method, or the like can be used, and among these methods, the surface coating by the CVD method is preferable from the viewpoints of forming film performance, adhesion, and the like. That is, for example, the surface of the sintered member is CVD coated at 1150 ° C. using trichlorosilane and hydrogen gas. As described above, the silicon carbide sintered body obtained by applying the method of the present invention has a very small impurity emission amount in a wide temperature range from a low temperature region to a high temperature region. jig,
Besides the lap plate, the susceptor and the like, it can be suitably used as a semiconductor heat treatment member such as a wafer boat and a core tube.

[0022]

[Example] "Example 1" A material silicon carbide sintered body produced by a self-sintering method (boron content: 0.086% by weight, free carbon amount: 1.2% by weight, density: 3.16 g / cm3) ³ ) is cut to form a prismatic SiC sintered body sample piece (3 × 3 × 40
mm) were prepared, and these were acid-washed with an aqueous solution of HF + HNO ₃ for about 30 minutes and dried at 110 ° C. for 1 hour. These sample pieces were placed in a furnace made of quartz glass and heated in an oxygen gas atmosphere at 1200 ° C. for 2 hours to form an oxide film layer on the sample surface. After cooling, the surface oxide layer was
The oxide film layer was removed by acid cleaning with a 0 wt% concentration hydrofluoric acid (HF) aqueous solution for 10 minutes. After drying this sample piece, this time it was heated in an oven at 1200 ° C. for 2 hours in an Ar gas atmosphere, and the sample was purified to obtain a silicon carbide sintered body sample piece of the present invention. Then, the treated sample piece was placed on the surface of a half-divided silicon wafer with its cut surface in contact, placed in a heating furnace, and heated to a predetermined temperature shown in Table 1 below in a dry oxygen atmosphere. After holding at that temperature for 1 hour, it is allowed to cool, and the increase amount of impurities (measured impurities: B, Fe) of each wafer is measured in comparison with the other half control wafer, and this is the amount of released impurities. (Unit: atoms / cm ² ). The results are shown in Table 1 and FIGS.

"Comparative Example 1" A plurality of sample pieces similar to the cut and sintered SiC prismatic sample prepared in Example 1 were washed and dried in the same manner as in Example 1, and these were subjected to an oxide film forming step and an oxide film removing step. The same procedure as in Example 1 was carried out except that the above was removed, and the amount of released impurities was measured. The results are shown in Table 1 and FIGS.

[Example 2] A sample piece treated in the same manner as in Example 1 was subjected to a CVD method (treatment condition: trichlorosilane + hydrogen gas: treatment temperature 1150 ° C, treatment time 3Hr) on the surface to form a SiC coat layer (layer thickness). 100 μm) was formed. These SiC surface-coated sample pieces were brought into contact with the wafer in the same manner as in Example 1, and the amount of released impurities in the higher temperature region than in Example 1 was measured. The results are shown in Table 2 and FIGS.

"Comparative Example 2" A sample piece similar to that used in Comparative Example 1 was used, and the surface thereof was subjected to CVD in the same manner as in Example 2.
A SiC coat layer (layer thickness: about 100 μm) was formed by treatment, and the amount of released impurities was measured. The results are shown in Table 2 and FIGS. 3 and 4.

From the results shown in Tables 1 and 2 and FIGS. 1 to 4, the silicon carbide sintered body is oxidized in an oxygen atmosphere, the generated surface oxide layer is removed by HF cleaning, and then heat treatment is performed in an Ar atmosphere. Thus, it can be seen that the emission of impurities can be significantly reduced in a wide temperature range. This is because, in this type of sintered body, the processed surface layer contains more impurities than the inside, and the impurities are released by heating, and the amount of released impurities is high. In the sintered body according to the present invention, in which the impurities are removed, the impurities mainly exist as a solid solution in the inside of the sintered body, and the impurity in the SiC crystal phase has a small diffusion coefficient. It is considered to be a thing. Further, it is considered that the heat treatment in Ar gas removed the relatively easily migrated impurities existing in the grain boundaries and the microcracks, and the released impurity value was reduced to a lower level.

High temperature region (900 to 1) of the silicon carbide sintered body
200 ° C.) to reduce the amount of impurities released,
Conventionally, the method of coating the surface of the sintered body with SiC has been performed. However, in the case of a conventional coated product, a large amount of impurities are released from the sintered body during the coating treatment, and this is transferred to the coating layer to form a coating layer. Contamination results in a high released impurity value at the time of use, whereas the silicon carbide sintered body treated according to the present invention has no contamination at the time of coating, so that a clean coating film can be obtained at the time of use. In, it is considered that high cleanliness can be obtained.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

As described above, the silicon carbide sintered body member produced by the method of the present invention has excellent heat resistance, compactness, high thermal conductivity, corrosion resistance, and strength inherently possessed by the silicon carbide sintered body. It has various characteristics such as abrasion resistance as it is, and exhibits a remarkable effect of suppressing impurity emission over a wide temperature range from a low temperature range to a high temperature range. Therefore, members used in the precision industrial field that requires high cleanliness in the surrounding environment, especially fork jigs for wafer transfer, lap plates, susceptors and the like used in the semiconductor manufacturing industry field, as well as a wafer boat, It can be suitably used as a semiconductor heat treatment member such as a core tube.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the heating temperature and the amount of impurity boron emission in the silicon carbide sintered body members of Example 1 and Comparative Example 1.

FIG. 2 is a diagram showing the relationship between the heating temperature and the amount of impurity Fe emission in the silicon carbide sintered body members of Example 1 and Comparative Example 1.

FIG. 3 is a diagram showing the relationship between the heating temperature and the amount of impurity boron emission in the silicon carbide sintered body members of Example 2 and Comparative Example 2.

FIG. 4 is a diagram showing the relationship between the heating temperature and the amount of impurity Fe emission in the silicon carbide sintered body members of Example 2 and Comparative Example 2.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shigeaki Sugisaki 30 Soya, Hadano City, Kanagawa Prefecture, Research & Development Laboratory, Toshiba Ceramics Co., Ltd. (56) Reference JP-A-10-194876 (JP, A) JP-A-3- 83861 (JP, A) JP 5-339080 (JP, A) JP 6-116072 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C04B 41/80-41 / 91

Claims (8)

(57) [Claims] 1. A surface of a sintering aid-containing silicon carbide sintered body member that has been machined after sintering is cleaned to remove adhering particles, dried, and then heat-treated in an oxidizing atmosphere. Method for producing a silicon carbide sintered body member, characterized in that after the oxide film is oxidized and the generated oxide film layer is removed by acid cleaning, it is further heated and purified in an inert gas atmosphere or a hydrogen chloride-containing gas atmosphere. . 2. The method for manufacturing a silicon carbide sintered body member according to claim 1, wherein the surface of the silicon carbide sintered body member after the heat purification treatment is further subjected to a silicon carbide coating treatment. 3. The method for manufacturing a silicon carbide sintered body member according to claim 2, wherein the silicon carbide coating treatment is performed by a chemical vapor deposition method. 4. The silicon carbide sintered body member according to claim 1, wherein the sintering aid contained in the silicon carbide sintered body member is composed of boron. Manufacturing method. 5. The silicon carbide sintered body member according to claim 4, wherein the content of the boron sintering aid contained in the silicon carbide sintered body member is less than 1% by weight. Manufacturing method. 6. The heat treatment temperature in the oxidizing atmosphere is 6
The method for manufacturing a silicon carbide sintered body member according to any one of claims 1 to 5, wherein the temperature is from 00 to 1300 ° C. 7. The cleaning solution used for the acid cleaning is an aqueous solution containing hydrofluoric acid.
A method for manufacturing a silicon carbide sintered body member according to any one of 1. 8. The heat purification treatment is carried out at a temperature of 1200 ° C. or higher.
A method for manufacturing a silicon carbide sintered body member according to any one of 1.