JP2973762B2 - Method for producing silicon carbide sintered body for semiconductor production - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide sintered body for semiconductor production which is useful for producing parts for semiconductor production such as a semiconductor jig and a method for producing the same.

[0002]

2. Description of the Related Art In the semiconductor manufacturing process, conventionally, a jig made of quartz glass or silicon and other semiconductor manufacturing parts have been mainly used. Examples of the semiconductor jig include heat treatment jigs such as a wafer boat, a mother boat, a vertical long boat, a process tube, a liner tube, a fork, and a drawer bar. In addition, as a semiconductor manufacturing component used in a semiconductor manufacturing apparatus, there are a hand, a vacuum chuck, a bell jar spacer, a fixing / positioning jig, and the like.

[0003] However, quartz glass jigs and parts tend to be deformed or distorted during heat treatment because the strain point of quartz is as low as about 1100 ° C. May devitrify and destroy due to transfer to Therefore, especially in the case of a jig for heat treatment, the service life thereof is considerably limited under the use condition of the high temperature heat treatment. On the other hand, jigs and parts made of silicon have several problems that need to be solved industrially, such as low toughness and many restrictions on molding.

[0004] On the other hand, silicon carbide is chemically stable at high temperatures and has excellent corrosion resistance, and since its strength and rigidity at high temperatures are much higher than those of quartz glass, silicon carbide sintered bodies are partially used. However, at present, a metal impurity gas is often generated during diffusion heat treatment, and thus is not often used in a process of manufacturing a high-quality wafer. Therefore, it does not substantially contain metal impurities as a raw material of the silicon carbide sintered body.
High-purity silicon carbide powder (that is, each having a metal impurity content of 1 ppm or less) has been desired.

Silicon carbide has two crystal forms, α-type (hexagonal) which is stable at high temperatures and β-type (cubic) which is stable at low temperatures, but is industrially stable at low temperatures. β-type silicon carbide powder is more suitable for manufacturing jigs because β-type is easier to obtain a more uniform and high-purity powder. Methods for producing silicon carbide powder include (1) a reaction between SiO ₂ and C, (2) a reaction between metal Si and C, and (3) a gaseous phase of Si compound (eg, silicon tetrachloride) and hydrocarbon. A gas phase synthesis method in which the reaction is performed is known, but industrially, the raw materials are inexpensive and the reaction control is easy.
Silicon carbide powder is manufactured by the method (1).

It is said that the production of silicon carbide powder by the reaction between SiO ₂ and C in (1) proceeds by the following reaction at a high temperature. SiO ₂ + C → SiO (g) + CO (g) (a) SiO (g) + 2C → SiC + CO (g) (b) In the above formula, (g) means a gas.

[0007] These reactions include the solid-gas reaction of the above (b), and the diffusion on the solid side determines the rate of the reaction.
If the particle size on the solid side is large, there is a possibility that it is difficult to obtain a homogeneous powder.

[0008] The Acheson method is best known as a method for producing silicon carbide by these reactions. In the Acheson method, a mixture of two types of solid materials, a silicon material (SiO ₂ or SiO ₂ source) and a carbon material (C or C source), is heated in a discontinuous Acheson type electric resistance furnace. This is a method of producing silicon carbide by reacting with silicon. In this method, the accuracy of temperature control is not very good because of direct current heating, but the reaction becomes a high temperature, so that α-type silicon carbide which is stable on the high temperature side is formed in a lump. However, both of the two types of solid raw materials used contain a large amount of metal impurities, and it is necessary to pulverize the generated massive high-strength silicon carbide to pulverize it. Many metal impurities are mixed. Therefore, the powder obtained by this method includes:
That considerable amounts of metal impurities are inevitable.
There were major drawbacks. In addition, there is another problem in terms of the working environment that the workability is extremely poor because the bulky product is collected by removing the side wall of the furnace for each reaction.

Regarding the improvement of work efficiency, Japanese Patent Publication No. Sho 58-18
No. 325 and Nos. 58-34405, the continuous production of β-type silicon carbide powder without the need for a pulverizing step by solidifying the raw material mixture using a binder such as pitch. Has been proposed. Japanese Patent Application Laid-Open No. 61-6110 discloses an improved method of continuous production in which a silicon compound and a carbon compound are mixed with a liquid silicon compound and a functional group-containing organic compound which cures by polymerization or crosslinking. Using the raw material mixture, the raw material mixture is pre-heated to harden the functional group-containing organic compound to be solidified, and the obtained solid is fired in a non-oxidizing atmosphere to obtain β.
A method for continuously producing silicon carbide powder is described.

It is also known to homogenize a raw material mixture using a liquid raw material in order to produce silicon carbide powder having a uniform particle size and shape. For example, JP-A-57-8801
No. 9 proposes producing a silicon carbide powder by heating and firing a raw material mixture obtained by treating a carbonaceous raw material with a silicate liquid in a non-oxidizing atmosphere. In this publication, as a preferable method, a carbonaceous raw material is also used in a liquid form,
It is described that mixing takes place in the liquid phase. 1-42
No. 886 discloses that in order to improve the disadvantage that silica sol is slightly generated in the above reaction, a liquid silicon-based raw material, a liquid organic compound which generates carbon by heating, and a polymerization or a solution which uniformly dissolves the organic compound. A cured product containing Si, O and C obtained by reacting a mixed solution containing a cross-linking catalyst is used as a silicon carbide precursor, and this is fired in a non-oxidizing atmosphere to obtain a β-type silicon carbide powder. A method of manufacture is described.

However, in any of the above-mentioned methods for producing β-type silicon carbide powder, the final product contains unacceptable amounts of metal impurities in the semiconductor manufacturing process, for example, 3 ppm or more of at least one metal species. Residuals were confirmed and the metal impurity content was 1 pp for all metals.
m or less, it was difficult to produce a desirable high-purity β-type silicon carbide powder. Cleaning is effective for removing impurities, but it is extremely difficult industrially to reduce the impurity content to 1 ppm or less by cleaning. Since such powdered raw materials are used, the content of metal impurities in each of the silicon carbide sintered bodies (obtained by molding and sintering silicon carbide powder) used in the production of semiconductor jigs and parts is 1 ppm for each metal. It was not possible to reach the following desirable levels.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a β-type silicon carbide powder having a content of each metal element harmful to semiconductor production of 1 ppm or less, the content of each metal element harmful to semiconductor production. It is an object of the present invention to provide a method for producing a silicon carbide sintered body for semiconductor production having a high purity of 1 ppm or less, which is high enough to be used in a semiconductor production process.

[0013]

Means for Solving the Problems The present inventors have studied to achieve the above object, and found that most of metal impurities contained in β-type silicon carbide powder are derived from carbonaceous raw materials. I found out. That is, the silicon-based raw material can be industrially highly purified and can be easily obtained without substantially containing an impurity metal harmful to semiconductor production, but is preferably used as a solid carbon-based raw material. Various organic resins
(Eg, phenolic resin) contains a considerable amount of metal impurities harmful to semiconductor production derived from the catalyst at the time of production, and it is industrially difficult to reduce this to, for example, 1 ppm or less. In addition, since carbon easily adsorbs metals and the like, metal impurities harmful to semiconductor production inevitably remain in the final product silicon carbide powder. In addition, in the process of manufacturing silicon carbide sintered bodies through the steps of molding, calcining, and reaction sintering by impregnation of molten metal silicon from silicon carbide powder, there is a possibility that metal impurities harmful to semiconductor manufacturing may be mixed in from the outside. Attention should be paid to this point.

As a result of further research focusing on these two points, as a result of using an organic compound which is produced without using a metal catalyst and which is cured by polymerization or cross-linking as a carbonaceous raw material, it is possible to obtain a desired high carbonaceous material. That β-type silicon carbide powder of a purity can be obtained, and molding using this powder,
When manufacturing silicon carbide sintered body through each process of calcination and reaction sintering by impregnation of high purity molten metal silicon impregnation, the amount of impurities mixed in from outside may be during or after the process if sufficient care is taken. It can be easily suppressed to a level that can be removed by a subsequent high-purification treatment (eg, heat treatment or washing in an HCl gas atmosphere). The present inventors have found that a silicon sintered body can be manufactured, and have completed the present invention.

Here, the gist of the present invention is that a molded body obtained by molding silicon carbide powder is calcined in a non-oxidizing atmosphere, and the obtained porous body is impregnated with molten metallic silicon to carry out reaction firing. A method for producing a silicon carbide sintered body for semiconductor production, wherein the silicon carbide powder comprises: (a) a liquid silicon compound; and a silicon solid which is synthesized from a hydrolyzable silicon compound. At least one silicon-containing material selected from the group; and (b) at least one carbon selected from a polymerizable or crosslinkable organic compound synthesized using a catalyst containing no harmful elements for semiconductor production. A raw material mixture containing carbon and silicon and containing at least one component in a liquid state is solidified by heating and / or using a catalyst or a cross-linking agent, and the resulting solid is subjected to a non-oxidizing atmosphere. Heat and bake It was obtained by the average particle size of 0.5
Silicon carbide powder having a free carbon content of 20% by weight or less and a content of each metal element harmful to semiconductor production of 1 ppm or less (hereinafter, this silicon carbide powder is referred to as "high-purity precursor method powder"). Yes, the porous body obtained after calcination does not contain fine carbon particles or is 1 μm in the matrix of the porous silicon carbide.
A method for producing a silicon carbide sintered body for semiconductor production, characterized by having a structure in which m or less carbon fine particles are uniformly dispersed.

According to a preferred embodiment of the present invention, when a silicon carbide sintered body is manufactured through the steps of molding, calcining, metal silicon impregnation, and reaction sintering using the high-purity precursor method powder, In order to avoid contamination from outside as much as possible and to make it easy to remove impurities even when contamination cannot be avoided, heat treatment, washing, and cleaning in an atmosphere (inert gas or vacuum) are necessary. If the impurities are removed by a high-purification treatment or the like by a heat treatment in a halogen gas, the silicon carbide sintered body obtained after the reaction sintering becomes a β-type silicon carbide matrix of 50 to 80% by weight. And 0 to 30% by weight of a reactive silicon carbide phase and 0 to 40% by weight of a metallic silicon phase.
In addition, a high-purity sintered silicon carbide for semiconductor production can be obtained in which the content of each impurity element in this structure is 1 ppm or less in total of all phases.

In the present invention, elements harmful to semiconductor manufacturing (hereinafter referred to as "harmful elements") are vaporized as chlorides and the like in a heat treatment step of the wafer, taken into the wafer as impurities, and insulated from the Si wafer. It is an element that easily causes a decrease in resistance and a decrease in withstand voltage of SiO ₂ . Specific examples of this "harmful element" include heavy metal elements such as Fe, Ni, Cu, Cr, V and W, alkali metal elements such as Li, Na and K,
And alkaline earth or amphoteric metal elements such as Be, Mg, Ca, B, Al, and Ga.

The raw material mixture used in the method of the present invention comprises (a)
(B) at least one silicon-containing raw material selected from the group consisting of a liquid silicon compound and a siliconaceous solid synthesized from a hydrolyzable silicon compound, and (b) synthesized using a catalyst containing no harmful elements. And at least one carbon-containing raw material selected from polymerizable or crosslinkable organic compounds,
At least one component in the raw material mixture is a liquid component.
In order to obtain the desired β-type silicon carbide powder having a desired “harmful element” content of 1 ppm or less for each element, it is particularly preferable that all the raw materials used have a “harmful element” content of 1 ppm or less.

The liquid silicon compound as the component (a) was synthesized using a raw material containing no "harmful elements" and, if necessary, a catalyst containing no "harmful elements" in the production process.
It is preferable to use those having a "harmful element" content of 1 ppm or less. Examples of the liquid silicon compound include a group of polymers obtained by trimethylating a hydrolyzable silicate compound, an ester of the hydrolyzable silicate compound with a monohydric or polyhydric alcohol (diol, triol, etc.),
For example, ethyl silicate synthesized by a reaction between silicon tetrachloride and ethanol, a reaction product other than an ester obtained by a reaction between a hydrolyzable silicon compound and an organic compound (eg,
Tetramethylsilane, dimethyldiphenylsilane, polydimethylsilane).

The siliconaceous solid synthesized from the hydrolyzable silicon compound used as the component (a) is also referred to as a "harmful element".
It is preferable to use those having a content of 1 ppm or less. Such a siliconaceous solid may be any as long as it reacts with carbon in a high-temperature non-oxidizing atmosphere to generate silicon carbide. An example of a preferred siliceous solid is amorphous silica fine powder obtained by hydrolysis of silicon tetrachloride.

The component (b) may be any one or more of any kind that can be cured by polymerization or crosslinking by heating and / or a catalyst or a crosslinking agent, which is synthesized using a catalyst containing no harmful elements. It is composed of an organic compound and may be any of a monomer, an oligomer and a polymer. Preferred specific examples of such organic compounds include phenol resins, furan resins, urea resins, epoxy resins, unsaturated polyester resins, polyimide resins, polyurethane resins, and the like, which are synthesized using a catalyst containing no harmful elements. Resin. Among them, a resol type or novolak type phenol resin having a high residual carbon ratio and excellent workability is preferable.

The resole type phenolic resin useful in the present invention is obtained by converting a monovalent or divalent phenol such as phenol, cresol, xylenol, resorcin, bisphenol A and an aldehyde such as formaldehyde, acetaldehyde, benzaldehyde into a harmful element. Can be produced by reacting in the presence of ammonia or an organic amine as a catalyst that does not contain the same. Conventional resol-type phenolic resins have generally been produced using an alkali metal compound as a catalyst. However, such conventional resol-type phenolic resins have a "harmful element" content of more than 1 ppm, so that the present invention provides Not suitable for use.

The organic amines used as catalysts are primary,
Any of secondary and tertiary amines may be used. Representative amines include dimethylamine, trimethylamine, diethylamine, triethylamine, dimethylmonoethanolamine, monomethyldiethanolamine, N
-Methylaniline, pyridine, morpholine and the like. As a method for synthesizing a resol-type phenol resin by reacting a phenol and an aldehyde in the presence of ammonia or an organic amine, a conventionally known method can be employed as it is, except that a different catalyst is used. That is, with respect to 1 mole of phenol, 1 to 3 moles of aldehyde and 0.02 to 0.2
Add mole organic amine or ammonia and add 60-100 ° C
It may be heated to.

On the other hand, a novolak-type phenol resin useful in the present invention is produced by mixing a monohydric or dihydric phenol and an aldehyde as described above, and adding hydrochloric acid, sulfuric acid, p- It can be produced by reacting with an acid such as toluenesulfonic acid or oxalic acid as a catalyst. A conventionally known method can be employed as it is for the production of the novolak type phenol resin. That is, 0.5 to 0.9 moles of aldehydes and 0.02 to
0.2 mol of an inorganic or organic acid containing no "harmful elements" may be added and heated to 60 to 100 ° C.

In the production of the high-purity precursor method powder of the present invention, a raw material mixture in which at least one, preferably all, of the components (a) and (b) is liquid is used. For example, a liquid silicon compound is used as the component (a), and / or a liquid resin is used as the component (b).
For example, a liquid resol type phenol resin is used. Alternatively, in the case of a solid component such as a novolak type phenol resin, the solid component is dissolved in an appropriate organic solvent and used in the form of a solution. If all the components that make up the raw material mixture are solid,
Uniform mixing of the raw material components becomes difficult, and the particle size and shape of the silicon carbide powder obtained as the final product become uneven.

The above component (a) (silicon-containing raw material) and component (b) (carbon-containing raw material) are mixed, and if necessary, a polymerization or crosslinking catalyst or a crosslinking agent is added thereto. Prepare a raw material mixture. When the component (b) is a liquid such as a resol-type phenolic resin, the component (a) and the component (b) are mixed and preferably very thoroughly stirred to obtain a raw material mixture having a uniform composition. . When the component (b) is a solid such as a novolak type phenol resin, it is preferably
After dissolving the component (b) in a suitable solvent (eg, alcohol in the case of a novolak type phenol resin), the obtained solution is mixed with the component (a), and the mixture is preferably stirred very thoroughly.

When the component (b) is rapidly solidified only by heating, it is not necessary to add a polymerization or crosslinking catalyst. In many cases, however, a polymerization or crosslinking catalyst or a crosslinking agent for accelerating curing is used. Add to the raw material mixture and mix uniformly. As the catalyst, a catalyst for polymerization or crosslinking reaction containing no "harmful elements" is used. For example, as a curing catalyst for the resol-type phenol resin, inorganic acids such as hydrochloric acid and sulfuric acid, organic peroxides and organic sulfonic acids are suitable. (b) When the component is a novolak type phenol resin, a crosslinking agent such as hexamethylenetetramine is blended.

The resulting raw material mixture is then left at room temperature or heated to cause a polymerization or cross-linking reaction, and by curing the component (b), the mixture is solidified to form Si, C and oxygen. Is obtained as a silicon carbide precursor. For example, when the component (b) is a resol-type phenol resin or a novolak-type phenol resin, curing usually proceeds simply by leaving it alone. The heating temperature at the time of heating may be any temperature that is sufficient for curing the component (b), and can be appropriately determined according to the type of resin and the catalyst / crosslinking agent. At this stage, decomposition of the resin
Do not heat to a temperature high enough to cause carbonization. The heating atmosphere is not particularly limited, and the heating can be performed in the air or in a non-oxidizing atmosphere.

The obtained solid to be a silicon carbide precursor is
Next, by heating and firing in a non-oxidizing atmosphere, for example, vacuum, nitrogen, helium or argon, the solid is carbonized and silicified to obtain the desired β-type silicon carbide powder. The heating temperature is not particularly limited as long as it is a temperature necessary for this firing, but is generally about 1600 to 2000 ° C. The firing time is generally from about 30 minutes to 3 hours.

Before performing the heating and firing, as a pretreatment,
The solid matter obtained by curing is heat-treated at a temperature of 500 ° C. or more and 1300 ° C. or less to remove volatile components that are not carbonized, which are mainly contained in the organic compound (b). effective. The heat treatment as this pretreatment is
(b) The heat treatment is appropriately performed according to the resin type of the component, and the heat treatment atmosphere is preferably a non-oxidizing atmosphere as described above. When the volatile component is small, the solid obtained by curing can be directly heated and fired in a non-oxidizing atmosphere. There is no particular limitation on the rate of temperature increase during the heat treatment and the heating and firing.

The mixing ratio of the silicon-containing raw material and the carbon-containing raw material of the components (a) and (b) is determined by heat-treating a solid sample obtained by curing the raw material mixture at a temperature of 800 to 1400 ° C. in a non-oxidizing atmosphere. As a result, a heat-treated product containing no non-volatile components is formed, and the heat-treated product is determined on the basis of the atomic ratio of Si and C in the heat-treated product.
The mixing ratio of the components (a) and (b) is such that the atomic ratio of C to Si (C / Si atomic ratio) in the heat-treated product is 1 <C / Si <1.
It is desirable to determine such that 0, preferably C / Si = about 3. Since a part of carbon of the carbonaceous raw material is volatilized and lost during this heat treatment, the actual blending amount of the component (b) is determined in consideration of the C residual ratio (residual carbon ratio) in the mixture after the heat treatment. In addition, it is necessary to further add the lost C amount to the blending ratio determined for the heat-treated product. Note that the heat treatment at a temperature of 800 to 1400 ° C. in the non-oxidizing atmosphere is performed to determine the atomic ratio of C / Si in the carbide for the purpose of determining the mixing ratio. It is not necessary to carry out such a heat treatment for the production of. However, as described above, when heat treatment is performed before heating and firing the solid obtained from the raw material mixture, heat treatment can be performed within the range of these conditions.

When a solid raw material such as a hydrolyzable siliconaceous solid is blended into the raw material mixture, the ratio of the liquid raw material (including a solution obtained by dissolving the solid raw material in an appropriate solvent) is 5% by weight of the whole. It is preferable to avoid such a mixing ratio that the mixing ratio becomes less, because it hinders the homogenization of the raw material. That is, the liquid raw material is at least 5% by weight or more, preferably at least
It is present in a proportion of 15% by weight, particularly preferably 100% by weight.

The high-purity precursor method powder obtained after the final heating and sintering step by the above-described method is composed of fine powder of β-type silicon carbide having a relatively uniform particle size and shape. According to the powder X-ray analysis method, the mixing ratio of α-type silicon carbide in the powder was 1%.
% Or less, and if the reaction conditions are selected, a powder of a β-type silicon carbide single phase can be obtained. The average particle size of the powder mainly depends on the heating and firing temperature at the time of silicon carbide, and is generally 0.5 to 1000.
It is in the range of μm.

(B) a curable organic compound produced using a catalyst containing no "harmful elements" as a component,
(a) It is possible to obtain a high-purity precursor method powder having a "harmful element" content of 1 ppm or less by preferably using a high-purity raw material having a "harmful element" content of 1 ppm or less. Becomes

As described above, some "harmful elements" can be removed by high-purification heat treatment or cleaning, but the difficulty of removal greatly affects not only the types of the elements but also the bonding state and location of those elements. Is done. That is, it is in the state of adhering or adsorbing,
In addition, elements having a high vapor pressure are easily removed by heat treatment for purification or cleaning, but generally, it is not easy to remove harmful elements contained in silicon carbide polycrystal grains as a raw material. In particular, metal elements having a low vapor pressure even at a high temperature need to be reduced as much as possible at the raw material stage. For this reason, the content of “harmful elements” contained in the silicon carbide powder was set to 1 ppm or less.

The upper limit of the "harmful element" content in the silicon carbide powder is such that a silicon carbide sintered member manufactured from a β-type silicon carbide powder having a "harmful element" content of 1 ppm or less is currently used. Tests were conducted using Si wafer contamination check methods, such as the lifetime method and the X-ray transmission method.
It was determined because no adverse effects were observed. The smaller the "harmful element" is, the more preferable it is. Therefore, it is desirable to use a raw material having the lowest possible "harmful element" content.

In order to manufacture a silicon carbide sintered body useful for manufacturing a semiconductor jig and other semiconductor manufacturing parts from the high-purity precursor method powder, a suitable powder molding method such as a cold isostatic pressing method and a casting method is used. The above-mentioned silicon carbide powder is formed by a method, and the obtained formed body is calcined in a non-oxidizing atmosphere to form a porous body. At the same time, the porous body is impregnated with high-purity molten metal silicon at a high temperature. Reaction sintering is performed to obtain a silicon carbide sintered body. From this silicon carbide sintered body, a desired jig or component can be manufactured by an appropriate molding process.

In the manufacturing process of this sintered body, as described above, care should be taken to minimize the intrusion of "harmful elements" from the outside. For example, use a resin or the like that does not contain "harmful elements" for the contact parts and sliding parts with powder,
Coating with resin etc. that does not contain "harmful elements", impurities contained in deflocculants and binders used during molding by the casting method are limited to elements that can be easily removed by high purification treatment and washing, and can be removed Attention should be paid to reducing the amount. In this way, it is possible to obtain a silicon carbide sintered body having a target “harmful element” content of 1 ppm or less.

The particle size of the high-purity precursor method powder used for molding is adjusted, if necessary, so that the average particle size is in the range of 0.5 to 20 μm. If the average particle size is less than 0.5 μm,
When compacted by cold isostatic pressing, the density of the compact tends to be non-uniform due to a decrease in the fluidity of the powder, and in the molding by the casting method, the slurry in which the powder, the deflocculant and the binder are mixed is high. Due to the viscosity, the molded body is likely to be heterogeneous. On the other hand, if the average particle size exceeds 20 μm, when the molded body is calcined in the next step to form a porous body, the total cross-sectional area of the grains decreases, and the strength of the porous body decreases. Becomes difficult and industrially unsuitable.

It is desirable that the high purity precursor method powder used has a free carbon content of 20% by weight or less. The amount of free carbon in the silicon carbide powder can be adjusted by changing the mixing ratio of the silicon-containing raw material (a) and the carbon-containing raw material (b) in the raw material mixture. This free carbon has a mean particle size of 0.5 to 20 μm as carbon fine particles having a size of about 0.01 to 0.1 μm.
Is preferably distributed around the polycrystalline silicon carbide. Such atomization of free carbon can be achieved by preparing a precursor powder in which the component A and the component B are uniformly dispersed and hardened.

When the compact obtained from the finely divided silicon carbide powder containing free carbon is calcined into a porous body in a non-oxidizing atmosphere, a part of free carbon is adsorbed by oxygen atoms or the like. , And is removed, but the remainder remains in the matrix of the porous silicon carbide in a state of being uniformly dispersed as fine carbon particles of 1 μm or less. When the free carbon content in the silicon carbide powder before molding exceeds 20% by weight, when the porous body is impregnated with metallic silicon and subjected to reaction sintering, it is formed by a reaction between the impregnated metallic silicon and free carbon. Cracks are easily caused by the volume expansion of the silicon carbide. Therefore, the free carbon content in the silicon carbide powder is desirably 20% by weight or less.
The preferred range of the free carbon content is 0 to 10% by weight.

The molded body of the high-purity precursor method powder is calcined to obtain a porous body. As the calcination atmosphere, for example, a non-oxidizing atmosphere such as vacuum, nitrogen, argon, and helium is used. The calcination conditions are generally about 500-2000 ° C. for about 1-10 hours, depending on the size of the compact. This porous body does not contain fine carbon particles or has a structure in which fine carbon particles are uniformly dispersed in a matrix of porous silicon carbide.

Thereafter, the porous body is impregnated with a high-temperature, high-purity metallic silicon in a molten state for reaction sintering to obtain a silicon carbide sintered body which is the object of the method of the present invention. The reaction sintering by impregnation with metallic silicon is preferably performed under an inert gas or a vacuum atmosphere (however, nitrogen is not preferable because it reacts with silicon). The processing temperature conditions are generally a temperature of about 1450 to 1600 ° C. and a processing time of about 1 hour. ~
10 hours. The amount of metallic silicon impregnation is generally
It is about 20 to 50% by weight.

In the reaction sintering by impregnation of metallic silicon,
Fine-grained free carbon remaining in the porous body reacts with metallic silicon to form silicon carbide, and at the same time, silicon carbide particles are sintered by molten metallic silicon. Therefore, the sintered body obtained after the reaction sintering is composed of three phases: a silicon carbide matrix caused by silicon carbide powder, a reaction silicon carbide phase generated by a reaction between free carbon and metal silicon, and a metal silicon phase. Will be. The amount of residual oxygen contained in the silicon carbide powder is 1
In the case where the content is less than 99% by weight, silicon carbide accounts for 99% by weight or more of the free carbon.
To 80% by weight, 0 to 30% by weight of the reactive silicon carbide phase and 0 to 40% by weight of the metallic silicon phase. A preferred composition ratio is 50 to 70% by weight of a silicon carbide matrix phase, 0 to 10% of a reacted silicon carbide phase.
% By weight and 10-40% by weight of the metallic silicon phase.

It is easy to reduce the impurity of metallic silicon to less than 0.1 ppm, and the amount of harmful elements mixed in the production of this sintered body should not exceed the amount removed by high purification treatment or washing. Is not extremely difficult, so long as the silicon carbide powder used is of high purity (that is, the content of “harmful elements” is 1 ppm or less each), it is harmful to the semiconductor production contained in the sintered body. It is industrially relatively easy to realize that the total amount of these elements is 1 ppm or less in total of the three phases.

The high-purity sintered silicon carbide obtained by the method of the present invention can be easily formed into various shapes. Especially 10
In the high temperature region of 00 ° C or higher, the deformation is smaller than quartz, the strength is high, the strength is maintained up to about 1350 ° C, and gas generation of elements harmful to semiconductor production does not occur,
When applied to heat treatment jigs for manufacturing semiconductors such as wafer boats, mother boats, vertical long boats, process tubes, liner tubes, forks, drawer rods, etc., their strength and heat resistance are utilized.

Further, even in a temperature range of less than 1000 ° C. to room temperature,
Higher strength and higher purity than conventionally used quartz, so it is applicable to the manufacture of other semiconductor manufacturing equipment parts such as hands, vacuum chucks, belgers, spacers, fixing / positioning jigs, etc. It is also possible.

In particular, the use of the silicon carbide sintered body obtained by the method of the present invention as a material for a higher-purity semiconductor manufacturing apparatus required in a manufacturing process of a wafer having a high integration density is industrially difficult. It is reasonable to look at.

[0049]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In the examples, parts and% are parts by weight and% by weight unless otherwise specified.

Example 1 As a raw material, ethyl silicate as a liquid silicon compound was used.
(SiO ₂ content 40%, "toxic elements" does not substantially contain)
And a resol type phenol resin A having a nonvolatile content of 65%. The phenolic resin A was synthesized by a conventional method from high-purity phenol and formaldehyde, except that triethylamine was used as a catalyst.

Phenol resin A in 62 parts of ethyl silicate
After adding 38 parts and mixing uniformly, 16 parts of a 33% aqueous p-toluenesulfonic acid solution substantially free of "harmful elements" as a catalyst is further added, and sufficiently stirred and mixed.
A homogeneous raw material mixture was obtained. This raw material mixture is allowed to
Allowed to cure for minutes. The obtained resinous solid was heated to 1000 ° C. at a rate of 10 ° C./min in an electric furnace under a nitrogen atmosphere to obtain a heat-treated product containing no nonvolatile components. This heat-treated product was a homogeneous and dense solid, and the content of C and Si was estimated to be C / Si = 3 from the residual carbon ratio. This heat-treated product was heated at a rate of 10 ° C./min for 18 hours in an Ar atmosphere using the same furnace as above.
The temperature was raised to 00 ° C and maintained for 30 minutes.
After holding for a while, the mixture was allowed to cool to obtain high-purity silicon carbide powder A.

When the obtained silicon carbide powder A was examined by X-ray diffraction, it was substantially composed of only β-type silicon carbide, the average particle diameter was about 5 μm, and the free carbon content was 10%. Table 1 shows the results of impurity analysis of the silicon carbide powder A by activation analysis.

To 60 parts of the silicon carbide powder A obtained above, 3 parts of ammonium polycarboxylate as a deflocculant, 3 parts of an acrylic water-soluble emulsion as a binder, and 24 parts of water were mixed to form a slurry. This slurry was cast-molded in a mold, and the molded body was calcined in a vacuum atmosphere at 1000 ° C. or higher for 3 hours. The obtained porous body was impregnated with high-purity silicon (impurity content of ten nines) in an amount of 30% with respect to the total weight at 1500 ° C. for 1 hour, followed by reaction sintering. The obtained silicon carbide sintered body A had a silicon carbide matrix phase of 56% by weight, a reactive silicon carbide phase of 18% by weight, and a metal silicon phase of 26% by weight. Table 1 shows the result of analyzing the fragments of the silicon carbide sintered body A by activation analysis. The impurity contents of the sintered bodies shown in Table 1 are all the total amounts of the above three phases.

Comparative Example 1 As a comparative material, commercially available high-purity silicon carbide powder B was mixed, molded, calcined, impregnated with metal silicon, and reaction-sintered in the same steps as described above, and the obtained silicon carbide sintered body B was obtained. Table 1 also shows the results of the analysis of the fragment by activation analysis.

[0055]

[Table 1]

According to the present invention, when a phenolic resin synthesized using a catalyst containing no harmful elements and having a harmful element content of 1 ppm or less is used as the carbonaceous raw material, the harmful element content is 1 ppm each. The following silicon carbide powder (high-purity precursor method powder) can be obtained. From this powder, through the steps of molding, calcining, metal silicon impregnation and reaction sintering, silicon carbide having a "harmful element" content of 1 ppm or less each It was confirmed that a sintered body was obtained.

On the other hand, as in the comparative example, the commercially available high-purity silicon carbide powder contains at least one “harmful element” in an amount exceeding 1 ppm, and the obtained silicon carbide sintered body The "harmful element" content of at least one element exceeded 1 ppm, and was of unsuitable quality for use as a jig for semiconductor production.

[0058]

As described in detail above, a high-purity precursor method powder having a specific property obtained by a specific method is used as a raw material for sintering powder, and is formed, molded, calcined, impregnated with metallic silicon and reactively sintered. Depending on the process, the content of "harmful elements" is 1pp each
m or less silicon carbide sintered bodies could be obtained. Since the jig manufactured from this sintered body has a low content of "harmful elements", there is no need to worry about contamination of the wafer, and the jig can be sufficiently used for manufacturing a high quality wafer. This provides a high-performance semiconductor jig that is excellent in stability at high temperatures, corrosion resistance and strength, and does not contaminate the wafer, and is extremely useful in industry.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Haruyuki Kano, Inventor, Haruyuki Kano, Kashima-gun, Ibaraki Prefecture, Sumikin Chemical Co., Ltd. Inside Bridgestone (72) Inventor Hiroaki Wada 3-1-1 Ogawa Higashi-cho, Kodaira-shi, Tokyo Bridgestone Corporation (56) References JP-A-5-339057 (JP, A) JP-A-6-16404 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C04B 35/56 C01B 31/36 C04B 41/85

Claims (2)

(57) [Claims] 1. A semiconductor, comprising: sintering a molded body obtained by molding silicon carbide powder in a non-oxidizing atmosphere, impregnating the obtained porous body with molten metal silicon, and performing reaction sintering. A method for producing a silicon carbide sintered body for production, wherein the silicon carbide powder comprises at least one selected from the group consisting of (a) a liquid silicon compound and a silicon solid synthesized from a hydrolyzable silicon compound. Species of silicon-containing raw material, and (b)
At least one component containing carbon and silicon, comprising at least one carbon-containing raw material selected from polymerizable or crosslinkable organic compounds synthesized using a catalyst containing no element harmful to semiconductor production. The liquid raw material mixture is solidified by heating and / or using a catalyst or a cross-linking agent, and the obtained solid is heated and calcined under a non-oxidizing atmosphere. A silicon carbide powder having a carbon content of 20% by weight or less and a content of each metal element harmful to semiconductor production of 1 ppm or less, and the porous body obtained after calcination does not contain fine carbon particles or is porous. A method for producing a silicon carbide sintered body for semiconductor production, characterized by having a structure in which carbon fine particles are uniformly dispersed in a matrix of silicon carbide. 2. A silicon carbide sintered body for semiconductor production produced by the method according to claim 1, wherein the β-type silicon carbide mother phase is 50 to 50%.
It is composed of 80% by weight, 0 to 30% by weight of a reactive silicon carbide phase, and 0 to 40% by weight of a metal silicon phase, and the content of each metal element harmful to semiconductor production is 1 ppm or less in total of all phases. A silicon carbide sintered body for semiconductor production, characterized in that: