JP2008156169A - Silicon carbide granule, method for producing silicon carbide sintered compact using it and silicon carbide sintered compact - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a silicon carbide granule where a silicon carbide sintered compact with less defects such as pores and the like can be produced. <P>SOLUTION: The silicon carbide granule is characterized by containing a silicon carbide particle and having a mean strain value of 20% or more when pressed with a strength of 0.5 N/mm<SP>2</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a silicon carbide granule used for manufacturing a silicon carbide sintered body, a method for manufacturing a silicon carbide sintered body using the same, and a silicon carbide sintered body.

Silicon carbide sintered bodies are used for semiconductor wafers, sputtering targets, heater heating elements, and the like.
The silicon carbide sintered body used for such applications is required to have high density and plasma resistance, and for this purpose, it is preferable that there are few defects such as pores.

  On the other hand, as a method for producing a ceramic sintered body, a method using granules having excellent powder flowability is generally known. In this method, first, a slurry obtained by mixing a ceramic raw material powder (primary particles) with a particle size of about several μm with a solvent, a binder, or the like is spray-dried by a spray dryer (spray dryer) to form primary particles. A granule having a particle size of about several tens to 200 μm is produced. Subsequently, this granule is filled in a molding die and subjected to pressure and heat treatment to obtain a ceramic sintered body.

In the method for producing a ceramic sintered body using such granules, various methods have been studied for the purpose of reducing pores.
For example, a method for obtaining a silicon carbide sintered body by applying a humidification treatment to a pre-formed body that has been put into a granule mold obtained by using a spray dryer and then pressurizing, and then subjected to pressurization or heat treatment is proposed. (See Patent Document 1). According to this method, since the binder in the preform absorbs moisture and the glass transition temperature is lowered, the granules in the preform are easily deformed plastically, and the adhesion between the granules is increased by hydrostatic pressure. Therefore, it is possible to reduce the amount of pores of the sintered body to make it uniform and improve the mechanical characteristics.

In addition, in order to suppress the generation of coarse pores and obtain a homogeneous sintered body, water is added to the molded body obtained by removing the organic material forming aid contained in the ceramic molded body by heating to improve fluidity. There has been proposed a method of applying hydrostatic pressure, drying and firing after the application (see Patent Document 2).
JP-A-8-119751 JP-A-5-12302

However, the conventional techniques as described in Patent Document 1 and Patent Document 2 may not sufficiently suppress the occurrence of pore defects in the sintered body.
An object of the present invention is to solve the above problems. That is, an object of the present invention is to provide a silicon carbide granule capable of producing a silicon carbide sintered body with few defects such as pores, a silicon carbide sintered body using the same, and a method for producing the same.

  In order to solve the above-mentioned problems, the present inventor diligently studied the cause of the generation of pore defects in the silicon carbide sintered body. First, to suppress pore defects in a sintered silicon carbide body, it is easiest to increase the pressure applied during the production of the sintered body. However, this method is not practical from the viewpoint of practicality such as equipment. Therefore, it is necessary to study on the premise of general sintered body manufacturing conditions.

On the other hand, on the premise of general sintered body production conditions, the invention described in Patent Document 1 described above attempts to suppress pore defects by pre-humidifying the preform. However, even in this case, pore defects are generated. It is considered that the primary particles constituting the granules are not affected by the humidification process, and the same state as before the humidification process is maintained.
In addition, in the invention described in Patent Document 2, pore defects are attempted to be suppressed by adding water to a molded body obtained by removing the organic material forming aid by heating to impart fluidity. However, in this case as well, it is considered that pore defects are generated because the shape of the granules is maintained at a temperature of about the calcination for removing the organic material forming aid.
Therefore, the present inventor considered that it is important to use granules that are easily plastically deformed when pressurized in order to suppress pore defects based on the above findings, and found the following invention. .

That is, the present invention
<1>
A silicon carbide granule comprising silicon carbide particles and having an average strain amount of 20% or more when compressed at a strength of 0.5 N / mm ² .

<2>
A method for producing a silicon carbide sintered body comprising a step of pressing and sintering the silicon carbide granules according to <1> to form a sintered body.

<3>
A silicon carbide sintered body characterized by being produced through at least a step of pressing and sintering the silicon carbide granules according to <1>.

  As described above, according to the present invention, it is possible to provide a silicon carbide granule capable of producing a silicon carbide sintered body having few defects such as pores, a silicon carbide sintered body using the same, and a method for producing the same. it can.

<Silicon carbide granules>
The silicon carbide granule of the present invention contains silicon carbide particles, and is characterized in that an average value of strain amount when compressed at a strength of 0.5 N / mm ² is 20% or more.
Therefore, if a sintered body is produced using the silicon carbide granules of the present invention, a silicon carbide sintered body is produced using the silicon carbide granules under the same conditions as compared with the case of using a conventional sintered body manufacturing method. Even in this case, a silicon carbide sintered body with few defects such as pores can be obtained.
In addition, when the number of pore defects is reduced, the acceleration of plasma damage due to the pore portion is suppressed, so that the effect of improving the plasma resistance can be obtained.

The strain amount needs to be 20% or more, but is preferably 25% or more, and more preferably 30% or more. If the amount of strain is less than 20%, it becomes difficult to plastically deform when a pressure is applied to the granule, so that the generation of pore defects cannot be suppressed.
The upper limit of the amount of strain is not particularly limited, but it is practically 40% or less because the strength of the granule itself is lowered and it may be difficult to handle or it may be difficult to produce the granule. Preferably there is.

-Measurement method of strain-
In addition, the average value of the amount of distortion was calculated | required as an average value of the amount of distortion obtained about ten granule particles using the micro compression tester (made by Shimadzu Corporation, MCFW). Here, in the present invention, the amount of strain means “100 × size of the granule after being compressed by the indenter / size of the granule before being compressed by the indenter (%)”. .
The measurement with a micro compression tester was carried out by compressing granules left for 1 hour in an environment of temperature 25 ° C. and humidity 70 RH% at a strength of 0.5 N / mm ² until the granules were broken. .

-Average particle diameter of silicon carbide granules-
The average particle diameter of the silicon carbide granules is preferably in the range of 50 μm to 200 μm, and more preferably in the range of 50 μm to 200 μm. If the average particle size is less than 50 μm, the fluidity of the granules will be low, and even if the mold is filled with granules to form a sintered body, the filling rate will decrease, so pore defects are likely to occur. There is. Moreover, when the average particle diameter exceeds 200 μm, the gap between the granules filled in the mold becomes large, so that pore defects may easily occur in the obtained silicon carbide sintered body.

-Manufacturing method of silicon carbide granules-
The method for producing the silicon carbide granule is not particularly limited as long as the average value of the strain amount can be controlled to 20% or more. However, in the conventional method of granulating the slurry droplets, which have been atomized by spray-drying the slurry for granule production, by heating, the droplets are heated at a high temperature of about 120 ° C. within a very short time. Since the particles are heated, the bonding force between the primary particles becomes strong, and even when compressed, the plastic deformation of the granules hardly occurs.

  For this reason, the silicon carbide granule of the present invention is a solidification step in which a solvent is volatilized and dried to obtain a solidified product from a raw material slurry obtained by mixing silicon carbide particles, a sintering aid, a binder and a solvent, It is preferable that the solidified product is produced through at least a crushing step of crushing the solidified product to obtain a pulverized product. In order to remove coarse particles contained in the pulverized product, it is usually particularly preferable to perform a classification step of classifying the pulverized product with a sieve after the crushing step.

  Here, in the solidification step, in order to make the bonding between the silicon carbide particles (primary particles) constituting the silicon carbide granules loose, basically only the solvent is volatilized and the sintering aid and binder are chemically treated. It is particularly preferable that the reaction be carried out in a temperature range that does not cause any modification (for example, the temperature at which crosslinking does not occur when the binder is crosslinked by heating).

  Such a temperature range is appropriately selected according to the volatilization temperature and volatilization rate of the solvent to be used, and the temperature at which the sintering aid and binder begin to denature, but generally room temperature (20 ° C.) or more and 80 It is preferable that the temperature is within a range of 50 ° C. or less, and more preferable is a range of 50 ° C. or more and 70 ° C. or less. Below 20 ° C, the solvent may take too much time to volatilize, and above 80 ° C, chemical modification of the sintering aid and binder occurs and the bonding between the silicon carbide particles becomes stronger, and the silicon carbide granules Since it becomes difficult to plastically deform, the occurrence of pore defects may not be suppressed.

  Further, the time required for the solidification step depends on the processing temperature, the boiling point of the solvent, the solvent content in the slurry, etc., but is preferably in the range of 3 hours to 10 hours, and in the range of 5 hours to 8 hours. The inside is preferable. If it is less than 3 hours, it is necessary to process at a high temperature. Therefore, chemical modification of the sintering aid and binder occurs, the bonds between the silicon carbide particles become strong, and the granules are difficult to plastically deform. In some cases, the occurrence of defects cannot be suppressed. Further, if it takes 10 hours or more, it takes too much time, and the productivity of the granule and the sintered body using the same may be lowered.

  The solidification step is preferably performed so that the content of the solvent remaining in the obtained solidified product is 5% by weight or less, and more preferably 3% by weight or less. If the content of the solvent remaining in the solidified product is 5% by weight or more, brittle fracture of the solidified product is difficult to occur in the crushing step, so that sufficient crushing may not be possible.

  In a crushing process, if it is a well-known grinding | pulverization method, it can utilize without a restriction | limiting especially, For example, a ball mill, a mortar, etc. can be utilized.

  In the classification step, coarse particles and fine particles contained in the pulverized product are removed using a sieve in order to narrow the particle size distribution of the granules. The opening of the sieve depends on the pulverized product obtained in the pulverization step, but is preferably 200 μm or more for the purpose of removing coarse particles, for example, for the purpose of removing fine particles. Is preferably 50 μm or less.

Next, the raw material used for preparation of the silicon carbide granule of the present invention will be described.
-Silicon carbide particles (primary particles)-
The silicon carbide particles are not particularly limited as long as the particle diameter is about several μm produced by a known method, and α-type, β-type, amorphous, or a mixture thereof can be widely used. A commercially available product may be used. Of these, β-type silicon carbide particles are preferably used.
In addition, specifically, the average particle diameter of the silicon carbide particles is preferably in the range of 0.5 μm to 5 μm, and more preferably in the range of 1 μm to 3 μm. When the average particle size is less than 0.5 μm, handling in processing steps such as weighing and mixing becomes difficult. On the other hand, when it exceeds 5 μm, the specific surface area of the powder, that is, the contact area with the adjacent powder is small. It may be difficult to increase the density.

Further, from the viewpoint of increasing the purity of the obtained silicon carbide sintered body, it is preferable that the silicon carbide particles to be used have a higher purity.
High-purity silicon carbide particles were obtained, for example, by mixing a silicon compound (hereinafter sometimes referred to as “silicon source”), an organic material that generates carbon by heating, and a Z polymerization catalyst or a crosslinking catalyst. It can be produced by firing the solid in a non-oxidizing atmosphere.

  As the silicon source, liquid and solid compounds can be widely used, but at least one liquid compound is used. Examples of the liquid silicon source include polymers of alkoxysilanes (mono-, di-, tri-, tetra-). Among the alkoxysilane polymers, tetraalkoxysilane polymers are preferably used. Specific examples include methoxysilane, ethoxysilane, propyloxysilane, butoxysilane, and the like. From the viewpoint of handling, ethoxysilane is preferable. When the degree of polymerization of the tetraalkoxysilane polymer is about 2 to 15, a liquid low molecular weight polymer (oligomer) is obtained. In addition, there is a liquid silicate polymer having a high degree of polymerization.

Examples of the solid silicon source that can be used in combination with the liquid silicon source include silicon carbide. In this case, silicon carbide includes silicon monoxide (SiO), silicon dioxide (SiO ₂ ), and silica sol (a colloidal ultrafine silica-containing liquid containing colloidal molecules containing OH groups or alkoxy groups. ), Fine silica, quartz powder and the like.
Among these silicon sources, an oligomer of tetraalkoxysilane or a mixture of an oligomer of tetraalkoxysilane and fine powder silica, which has good homogeneity and handling properties, are preferable. Further, these silicon sources are preferably highly pure. Specifically, the initial impurity content is preferably 20 ppm or less, and more preferably 5 ppm or less.

  As an organic material that generates carbon by heating, in addition to a liquid material, a liquid material and a solid material can be used in combination. An organic material that has a high residual carbon ratio and is polymerized or crosslinked by a catalyst or heating is preferable. Specifically, monomers such as phenol resin, furan resin, polyimide, polyurethane, polyvinyl alcohol, and prepolymer are preferable. In addition, liquid materials such as cellulose, sucrose, pitch, and tar are also used. Among them, a resol type phenol resin is preferable in terms of thermal decomposability and purity. The purity of the organic material may be appropriately controlled according to the purpose. In particular, when high-purity silicon carbide particles are required, it is preferable to use an organic material having an impurity element content of less than 5 ppm each.

The blending ratio of the silicon source and the organic material can be determined in advance by using a molar ratio of carbon to silicon (hereinafter abbreviated as “C / Si”) as a guide. Here, C / Si is C / Si obtained from elemental analysis of a silicon carbide intermediate obtained by carbonizing a mixture of a silicon source and an organic material at 1000 ° C., and analyzing the result. As represented by the following reaction formula (I), carbon reacts with silicon oxide and changes to silicon carbide.
Formula (I) SiO ₂ + 3C → SiC + 2CO

Accordingly, in terms of stoichiometry, when C / Si is 3.0, the free carbon in the silicon carbide intermediate is 0%. However, since SiO gas or the like is actually volatilized, C / Si is Even at lower values, free carbon is generated. Since free carbon has an effect of suppressing grain growth, C / Si may be determined according to the particle size of the target powder particles, and the silicon source and the organic material may be blended so as to obtain the ratio.
For example, when firing a mixture of a silicon source and an organic material at about 1 atm and 1600 ° C. or higher, the generation of free carbon is suppressed by blending so that C / Si is in the range of 2.0 to 2.5. can do. When C / Si is blended so as to exceed 2.5 under the same conditions, the generation of free carbon becomes remarkable and silicon carbide particles having a small particle diameter can be obtained. Thus, the blending ratio can be appropriately determined according to the purpose.

  The impurity carbon contained in the silicon carbide particles is preferably 30% by weight or more and 40% by weight or less. The carbon content of silicon carbide (SiC) is theoretically 30% by weight, but it decreases from 30% by weight when it contains non-carbon impurities and increases from 30% by weight when it contains carbon impurities. To do. Since the silicon carbide particles obtained by adding and firing an organic material as described above contain carbon-based impurities, the carbon content is greater than 30% by weight. Therefore, if the carbon content in the silicon carbide particles is less than 30% by weight, the proportion of non-carbon impurities is high, which is not preferable in terms of purity. On the other hand, if it exceeds 40% by weight, the density of the obtained silicon carbide sintered body is lowered, which is not preferable in terms of strength, oxidation resistance and the like.

A mixture of a silicon source and an organic material can be cured to form a solid. Examples of the curing method include a method using a crosslinking reaction by heating, a method using a curing catalyst, a method using an electron beam and radiation. The curing catalyst to be used can be appropriately selected according to the organic material to be used. However, when phenol resin or furan resin is used as the organic material, acids such as toluenesulfonic acid, toluenecarboxylic acid, acetic acid, oxalic acid, hydrochloric acid, sulfuric acid, hexamine, etc. And the like.
The solid containing the silicon source and the organic material is heated and carbonized as necessary. Carbonization is performed by heating at 800 ° C. to 1000 ° C. for 30 to 120 minutes in a non-oxidizing atmosphere such as nitrogen or argon. Furthermore, silicon carbide is produced when heated at 1350 ° C. to 2000 ° C. in a non-oxidizing atmosphere. The firing temperature and firing time affect the particle size and the like of the resulting silicon carbide particles, and may be determined as appropriate. However, firing at 1600 to 1900 ° C. is efficient and preferable.
The method for obtaining the high purity silicon carbide particles described above is described in more detail in JP-A-9-48605.

-Sintering aid-
As the sintering aid, known sintering aids can be used. Examples of the metal-based sintering aid include alumina and yttria. Examples of the non-metal-based sintering aid include coal tar. In addition to pitch, pitch tar, phenol resin, furan resin, epoxy resin, phenoxy resin, various saccharides such as monosaccharides such as glucose, small saccharides such as sucrose, polysaccharides such as cellulose and starch, and the like. Further, two or more kinds of sintering aids may be used in combination, and when a nonmetallic sintering aid is used, it may also serve as a binder. In addition, when it is desired to produce a high-purity silicon carbide sintered body, only a nonmetallic sintering aid is used.
Among these sintering aids, in the present invention, it is preferable to use a phenol resin because a high-density silicon carbide sintered body can be obtained and also has a binder function, and in particular, a resol type phenol resin is used. More preferred.

-Binder-
As the binder, a known binder can be used, and examples thereof include polyvinyl alcohol and carboxymethyl cellulose.

-Solvent-
As the solvent, any known solvent can be used as long as it can disperse and dissolve the silicon carbide particles, the sintering aid, and the binder, and in the solidification step, the solvent is efficiently volatilized. From the viewpoint of facilitating handling at room temperature, it is preferable to use a solvent having a boiling point of 60 ° C. or higher and 150 ° C. or lower.
For example, when a phenol resin is used as a sintering aid, lower alcohols such as ethyl alcohol, acetone or the like can be selected.
In addition to the four types of components described above, for example, a dispersant may be used as necessary.

-Raw material slurry-
The content of each component in the raw slurry used for the production of silicon carbide granules is not particularly limited, but the content of silicon carbide particles is preferably within the range of 40 wt% or more and 75 wt% or less, A range of 50% by weight or more and 70% by weight or less is more preferable.
Further, the content of the sintering aid is preferably in the range of 9% by weight to 14% by weight, and more preferably in the range of 10% by weight to 12% by weight. The binder content is preferably in the range of 1% by weight to 5% by weight, and more preferably in the range of 2% by weight to 3% by weight.
However, when the sintering aid also serves as a binder, such as a phenol resin, a binder component is unnecessary.
The solvent content is preferably in the range of 25% by weight to 50% by weight, and more preferably in the range of 28% by weight to 38% by weight.

  In preparing the raw slurry, the silicon carbide particles, the sintering aid, the binder, and the solvent can be mixed using a known mixing method such as a mixer or a planetary ball mill. The instrument used for mixing is preferably made of a synthetic resin material in order to prevent mixing of metal element impurities. The mixing is preferably performed for about 10 to 30 hours, particularly about 16 to 24 hours, and sufficiently mixed.

<Silicon carbide sintered body and manufacturing method thereof>
The silicon carbide sintered body of the present invention is produced through at least a step of pressing and sintering the silicon carbide granules of the present invention. In addition, although pressurization and sintering can also be implemented simultaneously like a hot press method, when implementing separately, it implements sintering after implementing pressurization. Further, in order to obtain a silicon carbide sintered body with fewer pores and higher density, it is preferable to use a hot press method.

  In producing the silicon carbide sintered body, the silicon carbide granules are usually placed in a molding die prior to pressurization. Although the material which comprises a shaping die is not specifically limited, From a viewpoint of preventing mixing of the metal impurity in a silicon carbide sintered compact, it is preferable to use the shaping die made from graphite. Even in the case of a metal molding die, the contact part is made of graphite or a Teflon (registered trademark) sheet is used for the contact part so that the raw material powder and the metal part of the mold do not directly contact each other. If it interposes, it can be used conveniently. In particular, when it is desired to produce a high-purity silicon carbide sintered body, it is preferable to use a high-purity graphite material for the mold and the heat insulating material in the furnace. Specifically, a graphite material or the like that is sufficiently baked in advance at a temperature of 2500 ° C. or higher and does not generate impurities even when used at a high temperature.

Next, a case where a hot press method is used as an example of a method for producing a silicon carbide sintered body will be described.
In this case, the raw material powder (silicon carbide granules) arranged in the molding die is subjected to hot pressing. Although there is no restriction | limiting in particular about the pressure of a hot press, For example, the range of 300-700 kgf / cm < ² > is preferable. However, when pressurizing at 400 kgf / cm ² or more, it is preferable to use a hot press component, for example, a die, a punch or the like that has excellent pressure resistance.

  The processing temperature at the time of hot pressing is preferably in the range of 2000 ° C. to 2400 ° C., and it is preferable to raise the temperature up to the hot pressing processing temperature gently and stepwise. When the temperature is raised in this way, chemical changes, state changes, and the like that occur at each temperature can be sufficiently advanced, and as a result, contamination with impurities, cracks, and vacancies can be prevented.

An example of a preferred temperature raising step is shown below.
First, a molding die containing 5 to 10 g of raw material powder is placed in a furnace, and the furnace is evacuated to 40 Pa. Gently raise the temperature from room temperature to 200 ° C. and keep it at 200 ° C. for about 30 minutes. Thereafter, the temperature is raised to 700 ° C. in 6 to 10 hours and maintained at 700 ° C. for 2 to 5 hours. In the temperature raising process from room temperature to 700 ° C., desorption of adsorbed moisture and solvent occurs, and when a nonmetallic sintering aid is used, the carbonization proceeds. The holding time for holding the temperature at a constant value varies depending on the size of the silicon carbide sintered body, and may be set to a suitable time as appropriate. In addition, the determination of whether the holding time is sufficient can be based on the time point when the decrease in the degree of vacuum is reduced to some extent.

Next, the temperature is raised from 700 ° C. to 1500 ° C. in 6 to 9 hours, and can be maintained at 1500 ° C. for about 1 to 5 hours.
Here, when silicon oxide is used as a silicon source when producing silicon carbide particles, a reaction in which silicon oxide is reduced to silicon carbide proceeds while being maintained at 1500 ° C. (See formula (I) described above). If the holding time is insufficient, silicon dioxide remains and adheres to the surface of the silicon carbide particles, which may hinder densification of the particles and cause large grains to grow. The determination as to whether or not the holding time is sufficient is based on whether or not the generation of carbon monoxide as a by-product is stopped, that is, the reduction of the vacuum degree is stopped, and the reduction reaction start temperature is 1300 ° C. It can be used as a guide whether the vacuum has been recovered.

  The hot pressing is preferably performed after the inside of the furnace is heated to about 1500 ° C. at which the sintering starts, and then filled with an inert gas in order to make the inside of the furnace a non-oxidizing atmosphere. Nitrogen gas or argon gas is used as the inert gas, but it is preferable to use argon gas that is non-reactive even at high temperatures. When it is desired to produce a high-purity silicon carbide sintered body, it is preferable to use a high-purity inert gas.

After making the inside of the furnace a non-oxidizing atmosphere, the inside of the furnace is heated and pressurized so that the temperature becomes 2000 ° C. to 2400 ° C. and the pressure becomes 300 to 700 kgf / cm ² . If the maximum temperature is less than 2000 ° C, densification may be insufficient. On the other hand, if the maximum temperature exceeds 2400 ° C., the powder or raw material may be sublimated (decomposed). It is preferable that the temperature is raised from about 1500 ° C. to the maximum temperature over 2 to 4 hours and held at the maximum temperature for 1 to 3 hours. Sintering proceeds rapidly at 1850-1900 ° C. and is completed during the maximum temperature holding time.
Incidentally, the pressure conditions, there are cases where the density is less than 300 kgf / cm ² is insufficient, there is a case where graphite of the mold exceeds 700 kgf / cm ² may be damaged. The pressure in order to suppress the abnormal grain growth, it is preferable to 300kgf / cm ² ~700kgf / cm ² approximately in the range.

The density and porosity of the silicon carbide sintered body of the present invention are not particularly limited, but the density is preferably 2.9 g / cm ³ or more and the porosity is preferably 1% or less. It is particularly preferable that the concentration is 0 g / cm ³ or more and the porosity is 0.8% or less. When a silicon carbide sintered body having a high density is used, mechanical properties such as bending strength and fracture strength, and electrical properties of the obtained silicon carbide sintered body are improved. In addition, when a silicon carbide sintered body having a high density is used, the constituent particles are reduced in size, which is preferable in terms of contamination.

  In addition, when utilizing a hot press method, there exists a method of implementing a shaping | molding process prior to a sintering process as a method of densifying a silicon carbide sintered compact. This molding process is performed at a lower temperature and lower pressure than the sintering process. By carrying out this sintering step, the bulky powder can be made compact (small volume) in advance, and by repeating this step many times, it becomes easy to produce a large compact.

An example of various conditions of the molding process performed in advance prior to the sintering process is shown below.
The raw material powder is placed in a molding die and pressed at a temperature of 80 ° C. to 300 ° C., preferably 120 ° C. to 140 ° C. and a pressure of 50 kgf / cm ^{2 to} 100 kgf / cm ² for 5 to 60 minutes, preferably 20 to 40 minutes. Then, a molded body is obtained.
The heating temperature may be appropriately determined according to the characteristics of the sintering aid used. The density of the obtained molded body is, for example, 1.8 g / cm ² or more when silicon carbide granules having an average particle diameter of about 1 μm are used, and silicon carbide granules having an average particle diameter of about 0.5 μm are used. When used, it is preferably pressed to 1.5 g / cm ² . It is preferable for the density of the molded body to be used to be within this range because the silicon carbide sintered body can be easily densified.
The molded body may be cut so that the obtained molded body is compatible with a molding die used in the sintering process.

  The total content of impurity elements in the silicon carbide sintered body of the present invention (elements of atomic number 3 or more excluding C, N, O, Si in the periodic table of the 1989 IUPAC inorganic chemical nomenclature revised edition) 5 ppm or less is preferable, 3 ppm or less is more preferable, and 1 ppm or less is particularly preferable. By setting it to 5 ppm or less, it can be used for a process requiring high cleanliness, for example, a semiconductor manufacturing process.

  Moreover, in order to reduce the impurity element content of the silicon carbide sintered body, the content of impurity elements contained in the raw materials used (for example, silicon carbide particles and nonmetallic sintering aid) and the inert gas is 1 ppm or less. Or a method of removing impurities by adjusting various sintering conditions such as sintering time and temperature. The impurity element here is the same as described above, and has an atomic number of 3 or more (except for C, N, O, and Si) in the periodic table of the 1989 IUPAC inorganic chemical nomenclature revised edition. This element.

Other physical property values of the silicon carbide sintered body in the present invention are as follows: bending strength at room temperature 550 to 800 kgf / mm ² , Young's modulus 3.5 × 10 ^{4 to} 4.5 × 10 ⁴ , Vickers hardness 550 to 800 kgf / mm ² , Poisson's ratio 0.14 to 0.21, coefficient of thermal expansion 3.8 × 10 ^{−6 to} 4.2 × 10 ⁻⁶ l / ° C., thermal conductivity 150 W / m · K or more, specific heat 0.15 to 0 .18 cal / g · ° C., thermal shock resistance of 500 to 700 ΔT ° C., and specific resistance of 1 Ω · cm are preferable because various properties of the obtained silicon carbide sintered body are improved.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated, this invention is not limited only to a following example.

-Production of silicon carbide particles-
In the examples and comparative examples, the silicon carbide particles used to produce the silicon carbide granules were produced as follows.
First. 1700 g of ethyl silicate having a SiO ₂ content of 40% (produced by Air Water Co., Ltd., ethyl silicate 40) and a liquid resol type phenol resin having a water content of 20% (manufactured by Colcoat Co., Ltd., high purity phenol resin SR-1 101) 762.5 g was mixed, and 342.5 g of a 28 wt% aqueous solution of p-toluenesulfonic acid was added as a catalyst and cured and dried to obtain a homogeneous resinous solid. This was carbonized at 900 ° C. for 1 hour in a nitrogen atmosphere. The C / Si ratio of the obtained carbide was 2.40 as a result of elemental analysis.
1000 g of this carbide intermediate was put in a carbon container, heated to 1750 ° C. under an argon atmosphere, stored for 30 minutes, then heated to 1850 ° C. and held for 1 hour. The obtained powder was yellowish green and the average particle size was 25 μm.

(Example 1)
-Production of silicon carbide granules-
Silicon carbide particles: 89.5 parts by weight Phenolic resin (manufactured by Colcoat Co., Ltd., high-purity phenolic resin SR-1 101): 10.5 parts by weight Ethanol: 60 parts by weight The above ingredients were mixed for 16 hours with a ball mill 160 g of the raw material slurry was prepared, and this raw material slurry was put in a 500 ml beaker and heated at 40 ° C. for 8 hours to obtain a solidified product.

Subsequently, the solidified product was pulverized with an agate mortar and then classified using a sieve having an opening of 200 μm and a sieve having an opening of 50 μm to obtain silicon carbide granules.
The average particle diameter of the silicon carbide granules was 170 μm, and the average value of strain was 23%.

-Production of sintered silicon carbide-
Subsequently, the obtained silicon carbide granules are filled into a carbon graphite mold, and heated and pressurized at 2300 ° C. for 4 hours under a pressure of 500 kg / cm ² in an Ar atmosphere, and have a diameter of 30 mm and a thickness of 5 mm. A silicon carbide sintered body was obtained.

(Example 2)
A silicon carbide sintered body was produced and evaluated in the same manner as in Example 1 except that a silicon carbide granule produced by the procedure shown below was used. The results are shown in Table 1.

-Production of silicon carbide granules-
Silicon carbide particles: 89.5 parts by weight Phenolic resin (manufactured by Colcoat Co., Ltd., high-purity phenolic resin SR-1 101): 10.5 parts by weight Ethanol: 60 parts by weight The above ingredients were mixed for 16 hours with a ball mill 160 g of the raw material slurry was prepared, and this raw material slurry was put in a 500 ml beaker and heated at 40 ° C. for 6 hours to obtain a solidified product.

Subsequently, the solidified product was pulverized with an agate mortar and then classified using a sieve having an opening of 200 μm and a sieve having an opening of 50 μm to obtain silicon carbide granules.
The average particle diameter of the silicon carbide granules was 180 μm, and the average value of strain was 30%.

(Example 3)
A silicon carbide sintered body was produced and evaluated in the same manner as in Example 1 except that a silicon carbide granule produced by the procedure shown below was used. The results are shown in Table 1.

-Production of silicon carbide granules-
Silicon carbide particles: 89.5 parts by weight Phenolic resin (manufactured by Colcoat Co., Ltd., high-purity phenolic resin SR-1 101): 10.5 parts by weight Ethanol: 60 parts by weight The above ingredients were mixed for 16 hours with a ball mill 160 g of the raw material slurry was prepared, and this raw material slurry was put in a 500 ml beaker and heated at 30 ° C. for 8 hours to obtain a solidified product.

Subsequently, the solidified product was pulverized with an agate mortar and then classified using a sieve having an opening of 200 μm and a sieve having an opening of 50 μm to obtain silicon carbide granules.
The average particle diameter of the silicon carbide granules was 185 μm, and the average value of strain was 37%.

(Comparative Example 1)
A silicon carbide sintered body was produced and evaluated in the same manner as in Example 1 except that a silicon carbide granule produced by the procedure shown below was used. The results are shown in Table 1.

-Production of silicon carbide granules-
Silicon carbide particles: 89.5 parts by weight Phenolic resin (manufactured by Colcoat Co., Ltd., high-purity phenolic resin SR-1 101): 10.5 parts by weight Ethanol: 60 parts by weight The above ingredients were mixed for 16 hours with a ball mill 160 g of the raw material slurry was prepared, and this raw material slurry was put in a 500 ml beaker and heated at 100 ° C. for 3 hours to obtain a solidified product.

Subsequently, the solidified product was pulverized with an agate mortar and then classified using a sieve having an opening of 200 μm and a sieve having an opening of 50 μm to obtain silicon carbide granules.
The average particle diameter of the silicon carbide granules was 160 μm, and the average value of strain was 15%.

(Comparative Example 2)
A silicon carbide sintered body was produced and evaluated in the same manner as in Example 1 except that a silicon carbide granule produced by the procedure shown below was used. The results are shown in Table 1.

-Production of silicon carbide granules-
Silicon carbide particles: 89.5 parts by weight Phenolic resin (manufactured by Colcoat Co., Ltd., high-purity phenolic resin SR-1 101): 10.5 parts by weight Ethanol: 70 parts by weight The above ingredients were mixed for 16 hours with a ball mill Thus, 10,000 g of raw material slurry was prepared. Subsequently, the raw material slurry was spray-dried at 120 ° C. to obtain a powder.

Next, the obtained powder was classified using a sieve having an opening of 200 μm and a sieve having an opening of 50 μm to obtain silicon carbide granules.
The average particle diameter of the silicon carbide granules was 165 μm, and the average value of strain was 2%.

(Comparative Example 3)
A silicon carbide sintered body was produced and evaluated in the same manner as in Example 1 except that a silicon carbide granule produced by the procedure shown below was used. The results are shown in Table 1.

-Production of silicon carbide granules-
-Silicon carbide particles: 88 parts by weight-Phenol resin (manufactured by Colcoat Co., Ltd., high-purity phenol resin SR-1 101): 12 parts by weight-Ethanol: 70 parts by weight 10,000 g was adjusted. Subsequently, the raw material slurry was spray-dried at 120 ° C. to obtain a powder.

Next, the obtained powder was classified using a sieve having an opening of 200 μm and a sieve having an opening of 50 μm to obtain silicon carbide granules.
The average particle diameter of the silicon carbide granules was 160 μm, and the average value of strain was 2%.

-Evaluation-
About the obtained silicon carbide sintered compact, while measuring the bulk density by Archimedes method and evaluating plasma damage, the structure | tissue observation by the optical microscope was performed.
The plasma damage is 500 W in an atmosphere in which a silicon carbide sintered body is installed in a plasma generator (produced by Nihon Spindle, plasma generator 500), and a CF ₄ flow rate is 100 sccm, an O ₂ flow rate is 100 sccm, and a pressure is 50 Pa. The plasma treatment was performed for 1 hour, and the silicon carbide sintered body was evaluated by measuring the weight loss per unit area of the region where the silicon carbide sintered body was exposed to the plasma. The results are shown in Table 1.

In addition, as microscopic observations using an optical microscope, optical microscope photographs of the silicon carbide sintered body of Example 1 and the silicon carbide sintered body of Comparative Example 1 having the same bulk density are shown in FIGS. 1 and 2, respectively.
As apparent from the comparison between FIG. 1 and FIG. 2, if the bulk density is approximately the same, the sintered silicon carbide produced using the silicon carbide granules of the present invention is at the interface between the silicon carbide granule particles. It can be seen that there are few pore defects due to it and it has a dense structure.

  FIG. 3 is a graph showing changes in plasma damage with respect to the bulk density. In the figure, “◯” indicates the results of the example, and “■” indicates the results of the comparative example. As is apparent from FIG. 3, if the bulk density is approximately the same, it can be seen that the silicon carbide sintered body of the example produced using the granule of the present invention has smaller plasma damage.

3 is an optical micrograph of the silicon carbide sintered body of Example 1. FIG. 2 is an optical micrograph of a silicon carbide sintered body of Comparative Example 1. It is a graph which shows the change of the plasma damage with respect to bulk density.

Claims (3)

Silicon carbide granules comprising silicon carbide particles and having an average strain amount of 20% or more when compressed at a strength of 0.5 N / mm ² .   A method for producing a silicon carbide sintered body comprising a step of pressing and sintering the silicon carbide granules according to claim 1 to form a sintered body.   A silicon carbide sintered body produced through at least the steps of pressing and sintering the silicon carbide granules according to claim 1.