JPH0784351B2 - Semiconductor heat treatment apparatus, high-purity silicon carbide member for semiconductor heat treatment apparatus, and method for manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to the oxidation of silicon wafers, diffusion of doping elements,
The present invention relates to a high-purity silicon carbide member such as a soaking tube, a reaction tube, a boat, a cantilever, a susceptor of a semiconductor heat treatment apparatus such as a diffusion furnace or a CVD furnace, which is used in a process such as thin film formation, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In a heat treatment apparatus member used in a semiconductor element manufacturing process, an impurity element contained in the member is
It contaminates silicon wafers and semiconductor devices to be processed and causes defects, which causes a reduction in product yield. In order to prevent contamination of impurities and improve the yield of products, a high-purity quartz glass member or a high-purity silicon carbide member is used in a semiconductor heat treatment apparatus.

Quartz glass has been widely used as a material for a member for a heat treatment apparatus because it can be easily manufactured. However, when the heat treatment temperature is raised to 1100 ° C. or higher, it is softened and deformed or lost. In addition to being permeable (crystallized) and causing cracks, it has a drawback that it is easily damaged due to its small bending strength of about 6 kg / mm ² and its service life is short.

On the other hand, with respect to the silicon carbide material, although high-purity material such as quartz glass material is not obtained, it is 1200 ° C.
It has the advantages of being stable under the above high temperatures, having a large bending strength of 20 kg / mm ² or more at room temperature and high temperature, having no fear of deformation, less likely to be damaged, and having good durability. A conventional method for producing a silicon carbide-based sintered body, which is mainly used as α-type silicon carbide (hereinafter abbreviated as α-SiC) and silicon and is used as a member for a diffusion furnace, is disclosed in, for example, Japanese Patent Publication No. 54-10825. Is disclosed in.

Since powders of α-SiC are widely used as abrasives, powders classified into a narrow particle size range are commercially available, and these powders are used as raw materials for a silicon carbide sintered body. Select the green one with high purity and use it.

[0006] α-SiC is a substance having particularly excellent corrosion resistance to corrosive substances such as acids, and has sufficient corrosion resistance not only to hydrofluoric acid, hydrochloric acid and nitric acid but also to mixed acids thereof.
This property is used for refining α-SiC powder, and it is disclosed in
As described in 8622, the α-SiC raw material powder is highly purified by washing with a mixed acid of hydrofluoric acid and nitric acid and pure water. According to this method, α-SiC raw material powder containing impurities of 15 ppm level can be obtained. Then, α-SiC refined to this level is used for manufacturing silicon carbide based components for diffusion furnaces.

However, as the degree of integration of semiconductor elements to be manufactured such as LSI and VLSI increases, contamination of the element to be processed due to the impurity element greatly affects the yield of the product, so that there is no fear of contamination due to the impurity element. There is a strong desire to use high-purity heat treatment equipment members.

As one countermeasure for this, Japanese Patent Laid-Open No. 63-2
In JP 57218 and JP-A 1-282152, a high-purity and dense film is formed on the surface of a silicon carbide member by a CVD method, and this film is used as a barrier for preventing impurity diffusion, and A method of preventing product contamination is disclosed. Although this method is an effective method, it is not easy to form a film without pinholes, and peeling of the film may occur, which completely prevents diffusion of impurities contained in the silicon carbide material. Is difficult to do.

Further, since the impurity element existing inside the CVD apparatus is sometimes taken into the CVD film, the problem of yield reduction due to contamination of the impurity element is still urgent in the manufacture of highly integrated LSI.

[0010]

DISCLOSURE OF THE INVENTION The present invention is directed to a semiconductor heat treatment apparatus which can prevent contamination of wafers and semiconductor elements due to impurity elements caused by a silicon carbide member for semiconductor heat treatment apparatus such as a diffusion furnace and further improve the product yield. It is intended to provide a high-purity silicon carbide material for a semiconductor heat treatment apparatus and a method for manufacturing the same.

[0011]

The high-purity silicon carbide-based member for a semiconductor heat treatment apparatus of the present invention is a silicon carbide-based member for a semiconductor heat treatment apparatus, which is mainly composed of α-SiC and silicon, and which constitutes α-SiC. The crystal grain size of SiC is 44μ
m or less, the weight average crystal particle diameter is in the range of 2 to 25 μm, silicon fills the space between the crystal particles of α-SiC, and the pressurized portion of iron that is an impurity contained in the member.
The solution analysis method is characterized in that the content is 2.5 ppm or less.

[0012]

Two crystal phases of α-SiC and β-type silicon carbide (hereinafter referred to as β-SiC) are known as crystals of silicon carbide.
Among these, β-SiC synthesized by vapor phase synthesis or reaction of silica and carbon produces fine powder of relatively high purity, and if high-purity powder is used as the raw material for the sintered body, it will be burned. Impurities are hardly taken into the inside of the crystal grains of the bonded member, and it is relatively easy to wash and highly purify. However, the β-SiC powder is difficult to form because the particles are too fine, and only a compact having a high porosity can be obtained even when compacted, and it is not possible to sinter a high-purity silicon carbide member that does not use a sintering additive. Since there is almost no firing shrinkage, a sintered body with high strength cannot be obtained.

Further, in the case of a sintered body having fine pores composed of fine crystal grains, there is a problem that impregnation with molten silicon is difficult. In addition, β-SiC is
The corrosion resistance to acids is inferior to that of α-SiC, and the durability is inferior to members for diffusion furnaces that require repeated acid cleaning. For these reasons α-S rather than β-SiC
iC is a more suitable material for semiconductor heat treatment equipment members.

A silicon carbide material having a small content of iron as an impurity also has a small content of other impurities at the same time. Therefore, by using a high-purity silicon carbide material for a semiconductor heat treatment apparatus, a semiconductor heat treatment apparatus can be used. It is possible to further improve the yield of products such as wafers and semiconductor devices to be processed therein, and the durability of the heat treatment apparatus is far better than that of the silica glass material.

The method for producing a high-purity silicon carbide-based member for a semiconductor heat treatment apparatus of the present invention is a method for producing a silicon carbide-based member for a semiconductor heat treatment apparatus, which is mainly composed of α-SiC crystal grains and silicon. Crush and classify
The particle size is 44 μm or less, and the weight average particle size is 2 to 25 μm.
The powder in the range of m was washed with a mixed acid of hydrofluoric acid and nitric acid and pure water, and was subjected to pressure decomposition analysis of iron as an impurity in the powder .
Content of 5 ppm or less, an organic binder is added to this powder, and the mixture is molded and fired at 1500 to 2300 ° C., and then high-purity silicon is melt-impregnated.

Particles of the raw material powder obtained by pulverizing and classifying α-SiC synthesized by the Acheson method are mostly single crystal grains of α-SiC. In the method for producing a high-purity silicon carbide-based member for a semiconductor heat treatment apparatus of the present invention, α-SiC powder has a particle size of 44 μm or less, which is finer than that of conventional ones.
-We found that impurities in the SiC powder particles could be easily dissolved by washing with a mixed acid of hydrofluoric acid and nitric acid, and made it possible to make powder of higher purity. Ion exchange water or distilled water is usually used as pure water.

To specifically exemplify the member for a semiconductor heat treatment apparatus according to the present invention, a soaking tube, a reaction tube, a boat, etc. used in an oxidation furnace, a diffusion furnace, a CVD furnace, etc. used in a wafer processing step. Wafer jig, cantilever,
Such as a susceptor. In the conventional method for producing a silicon carbide-based member for a semiconductor diffusion furnace described in Japanese Patent Publication No. 54-10825, α-SiC powder having an average particle size of 0.1 to 8 μm, as described in Examples, for example. 50% by weight and average particle size 30 to 1
70 μm α-SiC powder 50% by weight was used as a starting material,
High-purity silicon is melt-impregnated into what is molded and sintered, or carbon remaining in the sintered body is reacted with silicon at the same time as impregnation to form silicon carbide (this sintering process is called reactive sintering). Called) is manufactured.

However, α-SiC having such a conventional grain structure is used.
It has been found that when the powder raw material is used, the purity of the finally obtained silicon carbide sintered body is limited even if the α-SiC raw material powder and the sintered body are sufficiently washed. Crystals of α-SiC as a starting material are usually synthesized by a method called the Acheson method. In the Acheson method, silica sand and petroleum coke are usually used as raw materials, and the mixed raw materials are heated to 2200 to 2500 ° C. in an indirect electric resistance furnace to synthesize silicon carbide by a reaction such as SiO ₂ + 3C → SiC + 2CO. Since the reaction temperature is higher than 2100 ° C, all the silicon carbide crystals become stable α-SiC in this temperature range.

The obtained α-SiC is obtained as a lump in which a large number of coarse crystals are solidified. When this is used as a raw material for manufacturing a semiconductor heat treatment apparatus member, it is pulverized and classified, and then an impurity element such as iron is dissolved out using a mixed acid of hydrofluoric acid and nitric acid, and then pure water is used. Purify by washing. When the present inventors investigated,
Impurity elements adhering to the surface of the particles introduced in the crushing process can be removed relatively easily, but impurities taken in at the grain boundaries and inside the crystal particles can be removed even by washing with mixed acid and pure water. It was found that these residual impurities diffused inside the sintered body in the subsequent firing or silicon impregnation step and remained in the sintered body.

Therefore, the iron concentration is 5 ppm or less, further 2.5p
In order to obtain a high-purity silicon carbide-based member for a semiconductor heat treatment apparatus of pm or less, it is not enough to simply select and use a high-purity α-SiC raw material, which is difficult to remove. It is necessary to remove impurities existing inside. In order to confirm this fact and to establish the manufacturing method, it was necessary to develop and utilize a new analytical method described later.

As a result of various studies, it was found that most of the impurities existing inside the crystal adhere to the surface of the void formed inside the crystal. When the maximum particle size of the α-SiC raw material powder is set to 44 μm or less and the weight average particle size is crushed to 25 μm or less, most of the iron existing in the grain boundaries and the surfaces of the voids formed inside the crystals are present. It was found that impurity elements such as are exposed on the surface of the crystal particles and can be removed by washing with mixed acid and pure water.

If the weight average particle diameter of the α-SiC powder is made finer to 2 μm or less, the iron content can be reduced to 5 ppm or less by washing with mixed acid in terms of purity, but the concentration of impurities mixed in the raw material in the crushing step Becomes high, and it takes time and effort to clean the raw material powder with an impurity concentration of 5 ppm or less.
Further, if the particles of the powder are fine, the raw workability before firing of the molded body is poor, and the pore structure of the fired body becomes fine,
It is not preferable because impregnation with silicon becomes difficult.

On the contrary, the weight average particle diameter of the α-SiC raw material powder is
If it is larger than 25 μm, the raw material powder has a maximum particle size of 44 μm.
A large amount of powder that does not pass through the sieve remains when the product is classified by, and the ratio of the raw material powder that can be used decreases, and the moldability of the powder, especially in the case of sludge pouring, the smoothness of the sludge discharge surface (inside the compact) is reduced. This lowers the physical properties of the material such as bending strength, which is not preferable.

In the step of removing iron as an impurity, most of other impurity elements are also removed at the same time. The reason for this is that the mixed acid of hydrofluoric acid and nitric acid used for cleaning dissolves most of the impurity elements, and α-SiC crystals do not dissolve most of the impurity elements into the inside of the crystal. It exists only on the surface of. The molding, firing and impregnation of high-purity silicon for the semiconductor diffusion furnace member must be carried out with care so as not to deteriorate the purity level of the α-SiC powder as much as possible. However, the starting material α
-High purity of SiC powder is most important.

As a molding method for manufacturing the silicon carbide material for a semiconductor heat treatment apparatus, a slurry casting molding method, an isostatic pressing method, an extrusion molding method or the like can be adopted depending on the shape of the product. Also in the case of using the molding method, it is convenient that the width of the particle size distribution is wide because the moldability is good and the density of the molded body can be increased. In a preferred aspect of the method for producing a high-purity silicon carbide material for a semiconductor heat treatment apparatus of the present invention, the molding is performed by a sludge casting molding method.

The raw material powder used in the method for producing a high-purity silicon carbide member of the present invention has a particle size distribution particularly suitable as a sludge for the sludge casting molding method. That is, it becomes a sludge that is easy to use and stable, and by applying the sludge casting molding method, a molded body with a higher density than other molding methods can be obtained, and even if the molded body is thin, it is necessary and sufficient for handling and raw processing. Since it has various strengths, thin-walled tubes of various shapes and long-sized molded products can be easily obtained, and the particle size of the raw material α-SiC powder is 44 μm or less. The sedimentation rate of α-SiC powder in the slurry, which is a suspension, is low, and there are advantages such as being able to obtain a molded product with a small difference in wall thickness between parts.

The member obtained by the method for producing a high-purity silicon carbide member for a semiconductor heat treatment apparatus of the present invention has high strength and has sufficient strength even if it is thin, and the semiconductor heat treatment apparatus is light in weight and easy to use. It can be a device.
The isostatic pressing method can be preferably used for molding a susceptor having a relatively thick shape, a boat, and the like.

Further, although the molded body is subjected to raw processing to form molded bodies of various shapes, in this case as well, workability is better when a powder having a certain degree of coarseness is present. When considering the particle size suitable for highly purifying the raw material, the formability in production, raw workability, and the material properties of the resulting sintered body, α-SiC
The range of the weight average particle diameter particularly suitable as the raw material powder is 3 to
15 μm.

After firing, the amount of high-purity silicon impregnated into the pores of the sintered body is usually 7% by weight, because if the porosity of the sintered body is small, the number of closed pores increases and it becomes difficult to impregnate silicon. It is preferable that the above is impregnated with silicon.
By setting the silicon content of the sintered body to 35% by weight or less, more preferably 25% by weight or less, preferable physical properties such as high bending strength can be secured.

In the method for producing a high-purity silicon carbide-based member for a semiconductor heat treatment apparatus of the present invention, an organic binder is used, but since sintering is performed without a sintering aid, sintering is mainly surface diffusion or evaporation. And the condensation mechanism, the gap between particles does not shrink, and there is almost no firing shrinkage. Therefore, in order to obtain a dense sintered body having a small porosity, it is necessary to obtain a compact having a high density.

As the organic binder, phenol resin, polyvinyl acetate emulsion, acrylic resin emulsion or the like can be preferably used. When the phenol resin is used as the binder, carbon remains in the fired body. When carbon is impregnated with carbon, it reacts with silicon and changes to β-SiC.

In the firing step of the molded body made of α-SiC powder, the firing temperature may be low in the sense that strength that can be handled in the next silicon impregnation step is obtained, but firing is performed at 1500 ° C. or higher. As a result, sufficient strength for handling can be obtained. However, especially when a binder such as a phenol resin in which carbon remains is used, the firing temperature can be set to about 1000 ° C. Firing 21
If the temperature is higher than 00 ° C., crystal growth (called recrystallization) will proceed, and the structure of the sintered body will change due to the growth of crystal grains. At this time, the characteristics of the material gradually deteriorate, but the crystal growth is not remarkable up to 2300 ° C even if the firing temperature is increased. However, if the temperature is raised above 2300 ℃,
Crystal growth becomes remarkable, and there is a tendency that the material strength and the fracture toughness are reduced due to a decrease in the amount due to evaporation of the silicon carbide component.

[0034]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited thereto. The purification treatment of α-SiC powder was attempted for α-SiC powder having various particle sizes, and the results of analyzing the purity of the treated powder are shown in Table 1. That is, α-SiC
The operation of pouring the powder into a mixed acid of hydrofluoric acid and nitric acid (2: 1), stirring for 5 hours, and then washing with pure water was repeated 3 times. The iron in the powder after each washing was boiled and eluted in a mixed acid of hydrofluoric acid and nitric acid, and the iron in the obtained solution was quantitatively analyzed by atomic absorption spectrometry.

However, in order to quantify a trace amount of impurities, the reagents used were high-purity reagents for analysis, such as hydrofluoric acid and nitric acid (both having impurities of 1 ppb or less), instead of the usually used special grade reagents. . Here, the average particle size is a value obtained by obtaining the particle size distribution by an integrated weight distribution and reading the particle size at a position of 50% by weight.

From the analysis results in Table 1, it is understood that the α-SiC powder after pulverization and classification has a larger particle size, but contains more impurities, and more impurities are mixed during pulverization.
However, by repeating the washing, the analysis value by this analysis method settles at a certain purity level regardless of the particle size.

Therefore, if the particle diameter of the raw material powder is small, the impurity concentration increases, but the impurities introduced in the pulverizing step can be removed by washing with mixed acid and pure water. However, the method of analyzing impurities in silicon carbide based on JIS R6124 is a method of eluting only the impurity element present on the particle surface, and boiling the acid to analyze the impurities that can be eluted,
The impurity elements present in the crystal grain boundaries of α-SiC and inside the crystal are not dissolved and analyzed. Only α-S
It was clarified from the results of the following study that only the impurity elements on the surface of the iC powder particles were analyzed.

If the α-SiC particles can be decomposed and all or most of the impurity elements existing inside can be dissolved and analyzed, the true purity or an analysis value close to the true purity can be obtained. Should be obtained. Generally, alkali melting is performed as a method for decomposing silicon carbide crystal particles, but impurities derived from a reagent used for melting and a container used for melting often hinder the determination of a very small amount of impurities.

An attempt was made to apply a pressure decomposition method as a decomposition method capable of compensating for these drawbacks. That is, α-SiC
The powder of was stored in a container (using a fluorine resin) with corrosion resistance together with a mixed acid of hydrofluoric acid and nitric acid, sealed, and heated in a pressure resistant container to increase the pressure inside the container,
Promotes the decomposition of α-SiC crystal particles. When this method is applied, total decomposition of α-SiC particles is also possible, but by performing decomposition of 50% or more, the amount of impurity elements to be analyzed approaches the true content and saturates. However, it was found from the following examination that the amount of impurities can be analyzed with high accuracy.

First, the α-SiC powders shown in Table 1 which have been washed with mixed acid three times, that is, the α-SiC powders which have the same purity in the analysis by JIS method are decomposed by pressure. Was decomposed by, and the impurity element iron in the solution was analyzed by atomic absorption spectrometry. It should be noted that pressure decomposition is not completely performed, and the degree of decomposition is 50 to 60%,
Table 2 shows the analysis results of the obtained iron.

As can be seen from Table 2, the α-SiC powder contains iron, which is an impurity that could not be dissolved by the conventional washing method using mixed acid, inside the α-SiC particles. It can be seen that a large amount of iron is contained inside the particles. Considering the opposite, a certain value, for example 44μ
It can be seen that if the maximum particle diameter is smaller than m, the impurity element existing inside the particle is exposed on the surface of the particle and can be removed by washing with mixed acid.

This particle size is α-S synthesized by the Acheson method.
The particle size is significantly smaller than the average particle size of iC crystals.
In order to clarify in what state the impurity elements are contained in the α-SiC powder particles, we investigated the α-SiC powder particles with an X-ray microanalyzer and found that the iron present inside the particles was mainly found. It was found that the impurity element formed mainly adheres to the surfaces of the voids existing inside the crystal grains.

From these results, α-SiC powder particles were
When crushed to a particle size of m or less, almost all of the voids inside these crystal particles are exposed on the particle surface,
It can be explained that the impurity element can be removed by washing with mixed acid. In the above discussion, iron, which is an impurity element, was discussed, but it is an impurity element in which iron is most easily mixed in the process from the manufacturing stage of α-SiC raw material to the manufacturing of members, and the manufacturing process of the semiconductor element. Because it is one of the most impure elements to be excluded.

[0044]

[Table 1]

[0045]

[Table 2]

Example 1 An α-SiC powder having a maximum particle size of 44 μm and an average particle size of 8 μm classified by a 325 mesh sieve was washed with a mixed acid of hydrofluoric acid and nitric acid (2: 1) and pure water. Iron content 2.1ppm
Pure water and water-soluble phenolic resin are added to the raw material powder of
A slurry having a solid content concentration of about 80% by weight was obtained. Next, this sludge is poured into a vertically long gypsum mold to form a meat of about 4 mm, and the sludge remaining inside is discharged (called a sludge moulding method), the outer diameter is 310 mm, the inner diameter is 302 mm. A cylindrical shaped body having a length of 1780 mm was obtained. The difference in wall thickness between the upper part and the lower part of this molded body was as small as 0.5 mm.

After the molded body was dried, it was baked at 2000 ° C. in an electric furnace in an inert atmosphere. Next, the sintered body was transferred to another electric furnace, and the high-purity silicon used as the raw material of the semiconductor single crystal was melt-impregnated in vacuum at 1800 ° C., and the carbon remaining in the sintered body was simultaneously impregnated. Was reacted with silicon to form silicon carbide (in which case β-SiC is generated), and a sintered body was obtained in which all the pores were filled with high-purity silicon. After that, the product further washed with mixed acid and pure water is used as a liner tube of a semiconductor diffusion furnace.
When a small piece was cut from this sintered body and analyzed by the pressure decomposition analysis method described above, the iron content was 2.2 ppm.

Example 2 α-SiC powder having a maximum particle size of 30 μm and an average particle size of 4.5 μm, which had been classified using a custom-made sieve, was washed with a mixed acid of hydrofluoric acid and nitric acid (1: 2) and pure water to obtain iron. To obtain 1.8-ppm α-SiC powder. The α-SiC powder was granulated by adding a polyvinyl acetate emulsion aqueous solution as a binder. 15 of this granulated powder
Isostatic press molding at 00kg / cm ² , 50mm × 50mm
A rod-shaped molded body of × 1000 mm was obtained.

Next, this molded body was rawly processed into a columnar body having an outer diameter of 14 mm, and the slurry used in Example 1 was used as an adhesive agent for adhesion processing to obtain a wafer boat shape. The molded body after processing was fired and impregnated with silicon under the same conditions as in Example 1. Then, cut it with a diamond wheel to 1m to hold the silicon wafer.
A groove having a width of m was formed and further washed with a mixed acid and pure water to obtain a wafer boat.

When the iron content of the small piece cut out from the boat for wafers was analyzed by the pressure decomposition analysis method described above, it was 1.2 ppm. Simultaneously with the analysis of iron, the contents of other impurity elements were analyzed in the same sample solution.
Is 0.5ppm, Cu is 0.1ppm, Ca is 2ppm, Na and K are both 1p
The result is less than pm.

Example 3 α-SiC powder having a maximum particle size of 44 μm and an average particle size of 5 μm obtained by classification with a 325 mesh sieve was treated with hydrofluoric acid and nitric acid (1: 2).
The iron content obtained by washing with mixed acid and pure water is 1.1p
Pure water and an acrylic resin emulsion as a binder were added to the raw material powder of pm to obtain a slurry having a solid content concentration of about 75% by weight.
With this slurry, drainage mud casting is performed using a plaster mold,
Further, raw processing was performed to obtain a fork-shaped molded body for mounting on a wafer boat.

After this molded body was dried, it was fired at 1900 ° C. in an electric furnace in an inert atmosphere of argon. The porosity of the obtained sintered body was 18%, and the iron content examined by the pressure decomposition analysis method was 1.0 ppm. Then, the sintered body was transferred to another electric furnace, and the sintered body was melt-impregnated with high-purity silicon at 1800 ° C. in vacuum to obtain a sintered body in which all pores were filled with high-purity silicon.

Thereafter, the iron content was analyzed by the pressure decomposition analysis method described above for the small pieces cut from the sintered body which were washed with mixed acid and pure water, and found to be 1.1 ppm. A test piece was cut from the same sintered body, and the 3-point bending strength was measured by the JIS test method. It was 45 kg / mm ² at room temperature and 52 kg / m at 1200 ° C.
m ² and fracture toughness value K _1C is 4.5 MN / m ^3/2 at room temperature, 1200 ℃
At 6.5 MN / m ^3/2 was obtained. Therefore, it was found that the obtained sintered body had sufficient strength and practicality as a fork-shaped molded body for a diffusion furnace.

Example 4 Maximum particle size obtained by classification with a custom-made sieve 30 μm, average particle size
The 6 μm α-SiC powder was washed three times with mixed acid and pure water. The iron content of this α-SiC powder as determined by pressure decomposition analysis was 1.8 ppm. Pure water and a polyvinyl butyral emulsion having a low degree of polymerization as a binder were added to the α-SiC powder to prepare a slurry. 3 kg / cm of this slurry in a porous urethane mold
^It was injected at a pressure of ² and molded into the shape of a wheel with a shaft.

After the molded body was dried, it was fired at 1700 ° C. in an electric furnace in a nitrogen gas atmosphere, then the sintered body was transferred to another electric furnace, and high-purity silicon was melt-impregnated in vacuum at 1800 ° C., A mother boat wheel containing 31% by weight of silicon was obtained. When the content of iron in this sintered body was analyzed by the pressure decomposition method described above, it was 1.4 ppm, and the physical properties at 1200 ° C. of the test piece cut from the shaft portion of the wheel were examined, and the bending strength was 23 kg / mm ² , fracture toughness value K _1C is 7.1 MN / m
It was ^3/2 .

Example 5 An α-SiC powder having a maximum particle size of 15 μm and an average particle size of 3.3 μm obtained by classification by a water sedimentation method was washed under the same conditions as in Example 1 to obtain pure water and dextrin as a binder. In addition, it was slurried. Using this slurry, a liner tube having the same shape as that of Example 1 was molded and fired at 2150 ° C. in an electric furnace under vacuum to melt-impregnate high-purity silicon. 11% by weight
A liner tube containing silicon was obtained.

When the content of iron in this sintered body was analyzed by the pressure decomposition method described above, it was 0.5 ppm. The liner tube had a rough surface due to the high firing temperature, and the zircon insulation coating layer adhered well to this surface.

Example 6 Maximum particle size 15 μ obtained by classification in the same manner as in Example 5
α-SiC powder having m 2 and an average particle diameter of 2.4 μm was washed under the same conditions as in Example 1, and pure water and hydroxyethyl cellulose as a binder were added to this powder to obtain a plastic kneaded clay. Using an extruder having a cylinder coated with polytetrafluoroethylene (PTFE) and a plunger, a tube with an outer diameter of 10 mm and an inner diameter of 7 mm was extruded, and the tip was closed with the same clay to form a protective tube. .

After the molded body was dried, it was fired at 1600 ° C. in an electric furnace in an argon gas atmosphere, and silane gas was flown with hydrogen as a carrier gas to impregnate the sintered body with silicon. The content of iron in the obtained protective tube was analyzed by the above-mentioned pressure decomposition analysis method and found to be 0.4 ppm. It was confirmed that this protective tube was placed in a diffusion furnace and the surface of the sintered body was oxidized to produce silica, which has an insulating property and can be used as it is as a protective tube for a thermocouple.

Example 7 The powder obtained in Example 1 was further classified by air flow to remove particles of 10 μm or less, and the maximum particle size was 44 μm and the average particle size was 20 μm.
A μm α-SiC powder was obtained. This powder was washed under the same conditions as in Example 1, mixed with a small amount of stearic acid as a lubricant, and press-molded at 500 kg / cm ² to obtain 160 mm × 500 mm.
A 6 mm plate was used. This molded body was fired at 1550 ° C. in an electric furnace in an argon gas atmosphere, and then high-purity silicon was melt-impregnated to obtain a plate-shaped sintered body.

This sintered body was further ground to obtain a susceptor for a 6-inch wafer. The iron content of the obtained susceptor was analyzed by the above-mentioned pressure decomposition method and found to be 4.2 p.
pm and the chromium content simultaneously analyzed was 0.4 ppm. When a test piece was cut out from this sintered body and the bending strength was measured, it was 20 kg / mm ² at room temperature and 22 kg / mm ² at 1200 ° C.

Example 8 Maximum particle size 28 obtained by classification by the same method as in Example 5
α-SiC powder having a particle size of 12 μm and an average particle size of 12 μm was washed under the same conditions as in Example 1, and pure water and polyvinyl alcohol as a binder were added to prepare a slurry. Using this sludge, drainage sludge molding was performed to obtain a process tube having the same shape as in Example 1.

After the molded body was dried, it was calcined at 850 ° C. to remove the binder, and then calcined at 1800 ° C. in an electric furnace in a nitrogen atmosphere containing hydrogen. The sintered body was transferred to an electric furnace in a vacuum atmosphere, and high-purity silicon was melt-impregnated at 1800 ° C. to obtain a process tube containing about 15% by weight of silicon. When the content of iron in this sintered body was analyzed by the pressure decomposition method described above, it was 0.9 ppm.

Example 9 α-SiC powder having a maximum particle size of 44 μm and an average particle size of 12 μm obtained by classification with a 325 mesh sieve was washed by the same method as in Example 1, and the thickness was increased by the same method as in Example 4. 6mm, diameter 150mm
A circular plate was molded. The compact was fired at 1700 ° C in an electric furnace in a nitrogen gas atmosphere, the sintered compact was transferred to another electric furnace, and high-purity silicon was melt-impregnated at 1800 ° C in vacuum.

A small piece was cut out from this sintered body, and the iron content was analyzed by the pressure decomposition analysis method described above, and it was 3.1 ppm. Also, grinding this disc to make a radiation prevention plate,
The influence on the silicon wafer was examined by mounting it on a cantilever, but no influence by impurities was observed.

Comparative Example 1 α-SiC powder having a maximum particle size of 297 μm and an average particle size of 32 μm obtained by classification with a 48-mesh sieve was treated with a mixed acid of hydrofluoric acid and nitric acid and pure water in the same manner as in Example 1. After washing twice, the iron content of this powder was analyzed by the pressure decomposition analysis method and found to be 17.2 ppm. Using this α-SiC powder, a liner tube having a wall thickness of about 4 mm was produced in the same manner as in Example 1. The difference in wall thickness between the upper and lower sides of the molded body was 1.5 because the sedimentation rate of the particles of the slurry was large. It became mm.

[0067] Next in was analyzed cut pieces from the sintered body, the content of iron is 16.8Ppm, 3-point bending strength 21 kg / mm ² at 18kg / mm ^2, 1200 ℃ at room temperature, fracture toughness value
K _1C was 4.0 mN / m ^3/2 at room temperature 3.1MN / m ^3/2, at 1200 ° C..

Comparative Example 2 α-SiC powder having a maximum particle size of 105 μm and an average particle size of 22 μm obtained by classification with a 150-mesh sieve was washed under the same conditions as in Example 1, and the powder was analyzed by pressure decomposition analysis. The content of iron in the powder was analyzed and found to be 9.2 ppm. Using this raw material powder, a process tube was manufactured under the same conditions as in Example 1. A small piece was cut out from this process tube, and the content of iron was analyzed by the pressure decomposition analysis method, and it was 10.5 ppm.

Comparative Example 3 An α-SiC powder having a maximum particle size of 10 μm and an average particle size of 0.8 μm obtained by classification by the water sedimentation method was washed under the same conditions as in Example 1 to obtain an iron content of 0.8 ppm. A raw material powder was obtained. Using this powder, molding was performed in the same manner as in Example 2 to form a wafer boat, and firing was performed at 2000 ° C. in an electric furnace in an argon gas atmosphere. Next, this sintered body was melt-impregnated with silicon under the same conditions as in Example 2, but a portion not impregnated with silicon remained, and a crack was generated in the sintered body, and a satisfactory product was not obtained.

[0070]

The maximum particle size of the α-SiC raw material powder is 44 μm or less, and the average particle size is in the range of 2 to 25 μm, so that the α-SiC powder particles are almost single crystal particles, Impurities existing at the grain boundaries and inside the crystal can be barely exposed on the surface of the particles, and by cleaning this α-SiC raw material powder with a mixed acid such as hydrofluoric acid and nitric acid, and pure water. It has become possible to refine the iron content to 5 ppm or less, and further to 2.5 ppm or less.

A sintered body obtained by molding and firing α-SiC powder refined by this refining method as a raw material and impregnated with high-purity silicon has an extremely low content of iron, which is a representative impurity element, Concentration of less than 5ppm, and even 2.5ppm
It will be of the following high purity. Silicon carbide material for semiconductor heat treatment equipment manufactured by this high-purity sintered body and semiconductor heat treatment equipment such as diffusion furnace, oxidation furnace, CVD furnace, etc., in which this member is incorporated are used for heat treatment of semiconductor elements such as wafers and LSIs. By doing so, the product yield and productivity of semiconductor products can be further improved.

The high-purity silicon carbide material of the present invention is
Since the material strength and fracture toughness value are larger than those of conventional members, it is less likely to be damaged and reliable, and thin-walled members can be used to make a lightweight and easy-to-use semiconductor heat treatment apparatus. It's a lot.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location C04B 41/88 U H01L 21/22 501 M C04B 35/56 101 Y (72) Inventor Nobuo Kageyama Hyogo Asahi Glass Co., Ltd. Takasago Plant, Takasago City, Takasago Prefecture, Japan (72) Inventor Koji Furukawa 5-6-1, Umei, Takasago City, Hyogo Prefecture Asahi Glass Company, Takasago Plant (72) Inventor Ryuhei Makimura Toyama Prefecture, Toyama Prefecture Minami Ichibata 78-17 (56) Reference Japanese Patent Laid-Open No. 64-72964 (JP, A) JP-B 1-36981 (JP, B2)

Claims (1)

[Claims] 1. A silicon carbide-based member for a semiconductor heat treatment apparatus, which is mainly composed of α-type silicon carbide and silicon, wherein the α-type silicon carbide constituting the member has a crystal grain size of 44 μm or less, and a weight average crystal grain size thereof. 2 to 25 μm, silicon fills the crystal grains of silicon carbide, and the content of iron, which is an impurity contained in the member, by the pressure decomposition analysis method is 2.5 ppm or less. A high-purity silicon carbide member for a semiconductor heat treatment apparatus. 2. A semiconductor heat treatment apparatus incorporating a member made of a sintered body mainly composed of α-type silicon carbide and silicon, wherein the crystal grain size of α-type silicon carbide in the sintered body is 44 μm or less. , The weight average crystal particle diameter is 2 to 25 μ
In the range of m, silicon fills the crystal grains of silicon carbide, and the content of iron, which is an impurity contained in the sintered body,
A semiconductor heat treatment apparatus, characterized in that a high-purity silicon carbide member having a content of 2.5 ppm or less by a pressure decomposition analysis method is incorporated in a high temperature portion in the apparatus. 3. The semiconductor heat treatment apparatus according to claim 2, wherein the semiconductor heat treatment apparatus is a semiconductor diffusion furnace. 4. A method for manufacturing a silicon carbide-based member for a semiconductor heat treatment apparatus, which mainly comprises α-type silicon carbide and silicon, wherein α-type silicon carbide is crushed and classified to have a particle diameter of 44 μm.
Hereinafter, the powder having a weight average particle diameter in the range of 2 to 25 μm was washed with a mixed acid of hydrofluoric acid and nitric acid and pure water to reduce the content of iron in the powder by the pressure decomposition analysis method to 5 ppm or less. Add an organic binder to the powder and shape it into 1500-500
A method for producing a high-purity silicon carbide-based member for a semiconductor heat treatment apparatus, comprising melt-impregnating high-purity silicon after firing at 2300 ° C. 5. The method for producing a high-purity silicon carbide member for a semiconductor heat treatment apparatus according to claim 4, wherein the molding is performed by a sludge casting molding method.