JP3220730B2 - Graphite wafer holding jig for atmospheric pressure CVD equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wafer holding jig used in a normal-pressure CVD apparatus for holding a raw material wafer for a semiconductor device, and more particularly to a wafer holding jig mostly formed of a graphite material. It is about.

[0002]

2. Description of the Related Art A wafer holding jig used in a normal pressure CVD apparatus is shown in FIG. 6 for forming an oxide film on a wafer formed of silicon or the like as a raw material in a process of manufacturing a semiconductor device. Thus, the wafer is inserted into the atmospheric pressure CVD apparatus while holding a large number of wafers. In the step of forming an oxide film on the wafer,
At the same time, an oxide film is formed on the jig. However, if this jig is used repeatedly, the oxide film will gradually become thicker, which will peel off during use and adversely affect the wafer. Cleaning of the oxide film is required.

[0003] By the way, a general wafer holding jig is mainly formed using a quartz material. However, since this quartz material is weak to hydrofluoric acid, if the hydrofluoric acid cleaning is repeated many times, the quartz material is removed. The resulting wafer holding jig becomes so thin that it cannot be used, resulting in poor durability.

Therefore, it has been considered to form a wafer holding jig of this type using ceramics having resistance to hydrofluoric acid. However, the diameter of the wafer itself has been increased due to recent technological advances. Therefore, it is very difficult to form a large-sized wafer holding jig in consideration of shrinkage of firing of ceramics. In particular, ceramics are very poor in workability due to their excellent hardness, and the dimensional accuracy is inferior as the size increases. Most of all, ceramics are fired using a firing aid, but the firing aid remains as an impurity after firing, and this residual impurity becomes a problem as a wafer holding jig. It is.

On the other hand, in order to be able to form an oxide film on a wafer at normal pressure, a normal pressure CV as shown in FIG.
Although the D apparatus 30 has been developed, the normal pressure CVD apparatus 30 moves a wafer holding jig made of Inconel (nickel-chromium alloy) on a heater by, for example, driving a chain. This atmospheric pressure CVD device 3
In No. 0, the gas dispersion head is divided into three zones to facilitate the formation of an oxide film on the wafer, and nitrogen gas curtains are provided on both sides of the growth layer formation region.

What is important in such a normal pressure CVD apparatus 30 is that the temperature distribution of each wafer on the holding jig moving on the heater is uniform. Focusing on this temperature distribution, the normal pressure CVD apparatus 3 shown in FIG.
At 0, the reaction gas or curtain gas is flowing, the wafer holding jig moves, and the wafer holding jig is formed of a material having good thermal conductivity such as Inconel. For these reasons, it is very difficult to make the temperature of each wafer uniform. If the wafer has an uneven temperature during the formation of the oxide film, the oxide film cannot be made uniform, which is very disadvantageous. Further, when Inconel is used, warping is easily caused by heating, so that adhesion to a wafer is deteriorated, and an oxide film to be formed tends to be non-uniform.

Therefore, at present, heat resistance, low thermal conductivity,
There has been proposed one using a graphite material having many advantages as a component of a wafer holding jig such as easy workability and chemical resistance. High-density graphite used as a material for such a wafer holding jig has at least excellent chemical stability and heat resistance and is easily densified. is there.

However, in a wafer holding jig formed using a graphite material, if the use is repeated, a part of the graphite material may become fine particles and fall off, which is a cause of the contamination of the wafer. It was sometimes. In addition, this high-density graphite is graphitized by forming fine powder of coke or carbon with a binder component such as tar pitch at a high density and then firing,
Macroscopically, it has a textured structure due to the aggregation of graphite particles, which causes disadvantages such as not only consumption due to falling particles, but also contamination of the dropped graphite particles on the upper surface of the wafer. Furthermore, since high-density graphite has pores (pores) in its tissue structure, when a graphite jig is washed with hydrofluoric acid, hydrofluoric acid enters the pores, and the hydrofluoric acid that once enters the pores is hard to be removed. There is also an inconvenience.

As a result of a detailed study of the development and improvement process of this kind of wafer holding jig as described above, the present inventors have found that all materials for forming this kind of wafer holding jig are used. Although it was concluded that the graphite material was excellent in view of the surface, the problem described above had to be solved in order to use the graphite material.
Thus, the present inventors have conducted various studies on how to prevent the particles from falling off from the graphite material and how to prevent the entry of hydrofluoric acid during hydrofluoric acid cleaning. He realized that the use of cracked carbon produced good results and completed the present invention.

[0010]

SUMMARY OF THE INVENTION The present invention has been made on the basis of the above circumstances, and the problem to be solved is the falling off of graphite particles when a wafer holding jig is formed of a graphite material. .

An object of the present invention is to provide a wafer holding jig capable of preventing the graphite particles from falling off the graphite material and solving the problem of contamination on the wafer while making full use of the advantages of the graphite material. To provide.

[0012]

Means for Solving the Problems In order to solve the above problems, first, the means adopted by the present invention according to claim 1 is:
"The whole is isotropic, high-density, high-purity, the average coefficient of thermal expansion at 20 ° C to 400 ° C is 1.3 to 7.0 × 10 ^-6 / ° C, and the average pore radius measured by the mercury intrusion method is A raw material wafer 20 for a semiconductor element formed of a graphite material 11 of 18000 Å or less and formed in a normal pressure CVD apparatus.
Is a wafer holding jig 10 for holding the normal pressure C
A wafer holding jig 10 for a normal pressure CVD apparatus, wherein a pyrolytic carbon film 14 is formed on the surface of a VD apparatus 30.

The means adopted by the invention according to claim 2 is that the whole is isotropic, high-density, high-purity, 20 ° C. to 400 ° C.
Is formed of a graphite material 11 having an average thermal expansion coefficient of 1.3 to 7.0 × 10 ⁻⁶ / ° C. and an average pore radius measured by a mercury intrusion method of 18000 angstroms or less. A wafer holding jig 10 for holding a raw material wafer 20 for a semiconductor element therein;
An inner layer 12 formed by converting the surface of the graphite 11 into silicon carbide, and an outer layer formed by depositing a denser silicon carbide or pyrolytic carbon on the inner layer 12 on the surface of the graphite 11. A graphite wafer holding jig 1 for an atmospheric pressure CVD apparatus, characterized by being covered with a coating 13.
0 ".

A wafer holding jig 10 according to the invention of each claim
In the case of the graphite material as a base material,
The average coefficient of thermal expansion at 1.3 ° C. is 1.3 to 7.0 × 10 ⁻⁶ /
It must be in ° C. The reason is that when the pyrolytic carbon coating 14 or the outer coating 13 is formed on the surface of the graphite material, the pyrolytic carbon coating 14 or the outer coating 13 is formed.
However, even if the entire wafer holding jig 10 is subjected to a severe heat cycle, the surface of the graphite material 11 is not cracked or peeled off. That is, there is no difference between the graphite material 11 and the thermal expansion coefficient of the pyrolytic carbon coating 14 or the outer coating 13 to be formed on the graphite material 11 or the like. This is because it is necessary to make itself excellent in durability. In this sense, the average thermal expansion coefficient of the graphite material 11 in the above temperature range is 2.0 to 5.0 × 10 ^−6.
Is more preferable, and the anisotropic ratio is more preferably 1.5 or less.

Further, in order to know the average coefficient of thermal expansion between the room temperature of the graphite material 11 and an arbitrary temperature, the correction values shown in Table 1 may be used. In other words, since the amount of change in thermal expansion coefficient of general graphite materials due to temperature is almost constant regardless of the type, it is necessary to add the correction values shown in Table 1 to the values measured at 20 ° C to 100 ° C. Thus, the average coefficient of thermal expansion between room temperature and any temperature can be determined.

[0016]

In the wafer holding jig 10 according to the present invention, the graphite material 11 as a base material thereof has an average pore radius measured by a mercury intrusion method of 18,000 angstroms or less. is necessary. The reason is that the pyrolytic carbon coating 14 or the outer coating 13 formed on the surface of the graphite material 11 needs to have a sufficient anchor effect. If the average pore radius of the graphite material 11 measured by the mercury intrusion method is larger than 18000, the flatness of the pyrolytic carbon film 14 or the outer layer film 13 formed on the surface of the graphite material 11 is sufficient. When the wafer holding jig 10 is placed in an intense heat cycle, concentrated stress is likely to be partially applied to the outer layer coating 13 and the pyrolytic carbon coating 14, so that the outer layer coating formed at an angle is formed. This is because cracks enter the cracks 13 and the pyrolytic carbon coating 14 at an early stage or peel off in some cases.

The method for forming the pyrolytic carbon coating layer 14 on the surface of the graphite material 11 to form the wafer holding jig 10 according to the first aspect can be performed by various chemical vapor deposition methods. Usually, the graphite material 11 is heated, and a hydrocarbon gas such as methane or propane is brought into contact with the high-temperature graphite material 11 to cause a reaction, thereby generating pyrolytic carbon on the surface of the graphite material 11. In this case, hydrogen gas is suitable for adjusting the concentration of the hydrocarbon gas or for the carrier gas. The reaction is carried out under normal pressure or reduced pressure. However, the reaction is preferably carried out under reduced pressure in order to obtain the uniformity and smoothness of the coating film 14, and preferably at 300 Torr or less.

The pyrolytic carbon coating layer 14 has a thickness of 10 μm.
It is desirable that the thickness be in the range of m to 800 μm.
The optimum is about m to 300 μm.

On the other hand, in order to form the wafer holding jig 10 according to the second aspect, a method of converting the surface layer of the graphite material 11 to silicon carbide to form the inner layer coating 12 includes the following.
There is a method of reacting with silicon vapor or various silicon compounds, or a method of applying pack cementation, and the most preferable method is a method of reacting silicon monoxide gas with the graphite material 11 according to the following formula. SiO (g) + 2C = SiC + CO (g)

By using this method, the inner layer film 12 having a crystal structure (polytype) such as 2H, 3C or the like by Ramsdale notation while maintaining the shape and dimensions of the graphite material 11 for the wafer holding jig 10 is maintained. Can be formed.

The above reaction proceeds by heating in a temperature range of 1200 ° C. to 2000 ° C. Here, in order to generate silicon monoxide gas, a mixture of silicon powder and silicon dioxide powder, a mixture of silicon carbide powder and silicon dioxide powder, a mixture of carbon powder and silicon dioxide powder, and other various silicon It can be carried out by heating the compound to 1200 ° C to 2000 ° C.

When the graphite material 11 is reacted with silicon monoxide to convert the surface of the graphite material 11 to silicon carbide and form the inner layer 12, the treatment temperature is selected in the range of 1200 ° C. to 1650 ° C. The unreacted carbon remains in the silicide layer on the surface of the graphite material 11 to form silicon carbide having a crystal structure of 2H and a polytype as a main component;
It is possible to produce variously changed silicidation rate, which is the weight ratio of silicon carbide. The thickness of the silicide layer on the surface of the graphite material 11 can be controlled by adjusting the processing time in addition to the processing temperature. In addition, the silicidation rate and the thickness of the silicide layer can be controlled by adjusting the concentration of silicon monoxide.

Similarly, by selecting the reaction temperature between the graphite material 11 and silicon monoxide in the range of 1650 ° C. to 2000 ° C., unreacted carbon remains in the silicide layer on the surface of the graphite material 11 and the crystal structure Is a mixture of polytypes of 2H and 3C,
Alternatively, silicon carbide having a 3C polytype as a main component can be produced. It is desirable that the silicidation ratio, which is the silicon carbide fraction in the entire composite carbon obtained by converting the surface of the graphite material 11 into silicon carbide, is 98% by weight or less.

The outer coating 13 is formed by depositing and coating denser silicon carbide or pyrolytic carbon on the inner coating 12 obtained as described above. In other words, the outer layer coating 13 in the wafer holding jig 10 according to the second aspect of the present invention is composed of a silicon carbide coating and the above-described pyrolytic carbon coating 14.
There are types.

The formation of the outer layer film 13 by depositing and coating silicon carbide can be performed by a CVD method, a PVD method, or the like. In the CVD method, an organic silicon halide compound having a skeleton of silicon tetrachloride and toluene or Si-C, specifically, trichloromethylsilane or dichloromethylsilane is thermally decomposed at 1000 ° C. to 1800 ° C. in a hydrogen atmosphere. A silicon carbide film, that is, an outer film 13 is formed.

A specific example of the PVD method is that the target is S
There is a sputtering deposition performed using i or SiC.
What is necessary is just to carry out under conditions of 0 degreeC or more.

The crystal structure of the dense silicon carbide forming the outer layer coating 13 is made of a 3C polytype or 2H polytype in order to maintain consistency with the coefficient of thermal expansion of silicon carbide generated by the conversion reaction. Preferably, the main component is a type or a mixture thereof, but 4H or 6H may be the main component.

When the outer layer 13 is formed of a pyrolytic carbon film, the method of forming the pyrolytic carbon film layer on the surface of the inner layer film 12 on the graphite material 11 is as described above. As in the case of the coating film 14, it can be performed by various chemical vapor deposition methods. Normally, the graphite material 11 on which the inner layer coating 12 is formed is heated, and a hydrocarbon gas such as methane or propane is brought into contact with the high-temperature inner layer coating 12 to cause a reaction, thereby generating pyrolytic carbon on the surface of the inner layer coating 12. Depends on the method. In this case, hydrogen gas is suitable for adjusting the concentration of the hydrocarbon gas or for the carrier gas. The reaction is carried out under normal pressure or reduced pressure, but is preferably carried out under reduced pressure in order to obtain uniformity and smoothness of the film, and is preferably carried out at 300 Torr or less.

The thickness of the outer coating 13 made of a pyrolytic carbon coating is desirably in the range of 10 μm to 800 μm. If the outer coating 13 is too thick, the outer coating 13 is liable to peel off or crack. Optimal.

[0031]

The operation of the wafer holding jig 10 according to the present invention will be described below.

First, the wafer holding jig 10 according to each invention
Since most of the wafers are formed by the graphite material 11, not only the processing thereof is easy, but also the dimensional accuracy is excellent, and the
In other words, it can withstand the temperature at which the oxide film is formed at 0.

In the wafer holding jig 10 according to each invention, the pyrolytic carbon coating 14 is directly formed on the surface of the graphite material 11 (the wafer holding jig 10 of claim 1), or the surface side of the graphite material 11 Since the inner coating 12 and the outer coating 13 are formed from the inside toward the surface (the wafer holding jig 10 of claim 2), the entire surface thereof is pyrolytic carbon coating 14 or dense silicon carbide or thermal silicon coating. It is covered with pyrolytic carbon. This pyrolytic carbon coating 14
And the silicon carbide coating, the graphite material 11 located inside has a texture structure as an aggregate of granules,
It has a dense structure different from the granular aggregate. That is,
The pyrolytic carbon film 14 and the silicon carbide film have almost no pores, a high density, and a very low gas permeability similar to that of glass.

Further, a wafer holding jig 10 according to each claim is provided.
Since the average pore radius measured by the mercury intrusion method is 18000 angstroms or less, the graphite material 11 forming each of the constituent members was used.
The anchor effect of the pyrolytic carbon film 14 or the outer layer film 13 to be formed on the surface of the graphite material 11 is very excellent. In addition to the above, the outer layer film 13 or the pyrolytic carbon film The adhesive strength of the graphite material 11 to the graphite material 11 is sufficient.

What is particularly important is that the graphite material 11 constituting the wafer holding jig 10 is as described above, so that the wafer holding jig 10 is at normal pressure C shown in FIG.
That is, the temperature distribution when the heater is arranged in the VD device 30 and is heated by the heater is equalized. Therefore, the temperature distribution of each wafer 20 placed on the wafer holding jig 10 is made uniform.

Further, as the graphite material 11 of the wafer holding jig 10 of each claim, a material having an average coefficient of thermal expansion at 20 ° C. to 400 ° C. of 1.3 to 7.0 × 10 ⁻⁶ / ° C. was used. Thus, when the pyrolytic carbon film 14 or the outer layer film 13 is formed on the surface of the graphite material 11, even if the entire wafer holding jig 10 is subjected to a severe heat cycle, the graphite material 1
1 and the outer layer coating 13 or the pyrolytic carbon coating 14 hardly causes a difference in thermal expansion. Therefore, even when the wafer holding jig 10 is repeatedly subjected to the heat cycle, the outer layer coating 13 or the pyrolytic carbon coating 14 does not crack or peel off from the graphite material 11. Compared to a wafer holding jig simply made of graphite material 11, the life was about three times as long.

The above is a description of the wafer holding jig 1 according to each claim.
In particular, in the wafer holding jig 10 according to each claim, since the coating having the above-described configuration is formed on the surface side of the graphite material 11, It has the following operational characteristics. This will be described separately for each wafer holding jig 10 according to each claim.

Regarding the wafer holding jig 10 of the present invention, the wafer holding jig 10 of the present invention is such that the graphite material 11 constituting the wafer holding jig 10 is as described above. Pyrolytic carbon coating 1 formed on the surface
No. 4 has sufficient flatness and flatness, and even when the wafer holding jig 10 is placed in a severe heat cycle, a partial concentrated stress is particularly applied to the pyrolytic carbon film 14. Never. This also improves the adhesiveness of the pyrolytic carbon coating 14 to the graphite material 11 and improves the durability of the pyrolytic carbon coating 14 itself.

That is, since the entire outer surface of the wafer holding jig 10 is covered with the pyrolytic carbon film 14 having the above-described properties as shown in FIG. Atmospheric pressure CVD device 3 as shown in FIG.
When the wafer is exposed many times during a heat cycle in which it is heated in a temperature range of 0 ° C. and then kept at room temperature, the wafer holding jig 1
The pyrolytic carbon film 14 on the zero surface is not affected by the heat cycle, and the particles do not fall off unlike the graphite material 11. Further, since there are almost no pores, even when the gas is taken out of the furnace and exposed to the atmosphere, there is no adsorption of moisture and gas, and the amount of gas released during use is extremely small. Therefore, if the wafer holding jig 10 is used, the contamination of the wafer 20 is avoided. Since the total ash content of the pyrolytic carbon coating 14 itself can be suppressed to 20 ppm or less, as will be described later, the contamination of the wafer 20 by the ash of the pyrolytic carbon coating 14 It is completely negligible.

Further, since the pyrolytic carbon film 14 itself has very good resistance to hydrofluoric acid, even if the wafer holding jig 10 coated with it is washed many times with hydrofluoric acid. This allows the wafer holding jig 1
Zero is not consumed. Therefore, the wafer holding jig 10 is extremely excellent in durability. Furthermore, since the pyrolytic carbon film 14 has a dense structure different from that of the graphite material 11 having a structure structure as a granular aggregate, and hardly contains pores, there is no inconvenience that hydrofluoric acid enters and is difficult to be removed. .

Regarding the wafer holding jig 10 of the present invention, in the wafer holding jig 10 of the present invention, the outer layer coating 13 made of the pyrolytic carbon coating 14 or the dense silicon carbide coating according to the first aspect is provided. Since this is formed on the surface side of the graphite material 11 which is converted into the inner coating film 12 by converting the same, the following operation by the inner coating film 12 is important.

That is, in the wafer holding jig 10 according to the second aspect, the inner layer 12 is first formed on the surface of the graphite 11 by converting it into silicon carbide. There is a completely continuous organization between the two. That is, the inner layer coating 12 is made of the graphite material 11.
Is changed by reacting the surface with a silicon-containing gas such as silicon monoxide, so that the boundary with the graphite material 11 has a completely continuous structure. Therefore, the inner layer coating 12 functions as a support material for protecting the outer layer coating 13 on the surface side, and the outer layer coating 13 formed on the surface side of the inner layer coating 12 is attached to the wafer holding jig 1.
No cracking or delamination occurs when 0 is subjected to a severe heat cycle.

The inner coating 12 of the wafer holding jig 10
Is coated with an outer layer 13 made of a silicon carbide film or a pyrolytic carbon film 14, so that the outer layer 13 protects the entire graphite material 11 mainly constituting the wafer holding jig 10. It is being done.

That is, the outer coating 13 made of silicon carbide
Since the material itself is high in hardness and is integrated with the graphite material 11 via the inner layer coating 12, the graphite material 11 located inside is completely wrapped and protected. is there. And this outer layer coating 13
Since it is formed on the surface of the inner layer film 12 of substantially the same quality by the CVD method or the like, not only the adhesive strength to the inner layer film 12 is sufficient, but also the wafer holding jig 10 is placed in a heat cycle. In this case, it can withstand the thermal shock in the event that it occurs.

On the other hand, the outer layer coating 13 is
In this case, the pyrolytic carbon coating 14 has the same function as that of the wafer holding jig 10 according to the first aspect of the present invention. Thus, the pyrolytic carbon film 14 as the outer layer film 13 is firmly held on the surface of the graphite material 11. Accordingly, even if the wafer holding jig 10 is placed in a heat cycle, the pyrolytic carbon coating 14 as the outer layer coating 13 is formed.
It does not crack or peel.

[0046]

Next, a wafer holding jig 10 according to each invention will be described.
To explain according to the embodiment shown in the drawings, as shown in FIG. 1, the wafer holding jig 10 is composed of a flat support having a graphite material 11 as a main material. It has isotropic properties and high density (1.7 to 2.0 g / cm
³ ) It is formed of a graphite material 11 of high purity (total ash content not more than 20 ppm). The graphite material 11 forming the wafer holding jig 10 has an average pore radius measured by a mercury intrusion method of 18,000 angstroms or less. Further, the graphite material 11 constituting the wafer holding jig 10 has an average thermal expansion coefficient of 1.3 to 7.0 × 10 ⁻⁶ / ° C. at 20 ° C. to 400 ° C.
A pyrolytic carbon film 14 is formed on the surface of the graphite material 11 as shown in FIG. 3 (wafer holding jig 10 of claim 1), and is shown in FIG. 4 or FIG. As described above, the inner layer film 12 and the inner layer film 12 made of pyrolytic carbon or silicon carbide are formed in order from the inside (the wafer holding jig 10 of claim 2).

In the graphite material 11 used in this embodiment, the volume occupied by the pores having the average pore radius in the above range is 0.02 cc / g to 0.20 cc.
cc / g. The pores having such a volume are formed to make the anchor effect of the outer layer coating 13 and the pyrolytic carbon coating 14 formed on the surface of the graphite material 11 more effective. This is for ensuring the adhesion of the carbon coating 14 and preventing the occurrence of concentrated stress during the heat cycle on the outer coating 13 and the pyrolytic carbon coating 14.

The following is a detailed description of embodiments of the present invention, based on the conditions of the graphite material 11 as a base material as described above.

Regarding the wafer holding jig 10 according to the first aspect, in the wafer holding jig 10, as shown in FIG.
A pyrolytic carbon film 14 having a thickness of about 0 to 500 μm is formed so as to cover at least the surface of the support table on which the wafers 20 are mounted.

The method of forming the coating 14 of pyrolytic carbon on the surface of the graphite material 11 can be performed by various commonly used chemical vapor deposition methods (CVD).
Heated to 00 to 2600 ° C., and a hydrocarbon or halogenated hydrocarbon is brought into contact with a substrate in the presence of hydrogen gas,
A dense layer of pyrolytic carbon is formed on a graphite material having many pores. These reactions are performed under normal pressure or reduced pressure. However, considering the uniformity and smoothness of the pyrolytic carbon film 14, it is preferable to perform the reaction under reduced pressure, particularly at 300 Torr or less. The thickness of the pyrolytic carbon coating 14 is 10
μm to 500 μm is desirable. The reason is that if the thickness is less than 10 μm, sufficient wear resistance cannot be obtained.
If the thickness is more than μm, there is a high possibility that cracks will occur in the coating due to the difference in thermal expansion with the graphite material 11.

Of course, the pyrolytic carbon formed as described above has high purity, but various impurities such as iron, nickel, cobalt, and vanadium are contained in the graphite material 11 used for laminating the pyrolytic carbon itself. It may be mixed,
These may remain on the pyrolytic carbon side. Possible routes through which impurities are mixed in the pyrolytic carbon are that the impurities in the graphite material 11 are diffused during the formation of the pyrolytic carbon and that the impurities are mixed in the supply gas. Can be These impurities are high purity graphite material 1
1 and the purity of the supply gas (select the structure and material of the gas supply parts, supply pipe and reaction vessel, etc.)
It can prevent mixing in pyrolytic carbon. By such a method, the amount of all ash (impurities such as iron) in the pyrolytic carbon coating 14 can be reduced to 20 ppm or less.

As a raw material gas for forming the pyrolytic carbon film 14, a hydrocarbon gas such as methane, propane or benzene from which impurities have been sufficiently removed is used, and hydrogen gas and argon gas are used as carrier gases for adjusting the concentration. Gas was used. As a result, the raw material gas is decomposed, bonded, and the like on the surface of the graphite material 11 at a high temperature.
Deposited as pyrolytic carbon.

Regarding the wafer holding jig 10 according to the second aspect, in the wafer holding jig 10, the surface of the graphite material 11 is first converted into silicon carbide to be continuous with the graphite material 11. The inner layer film 12 was formed, and the outer layer film 13 composed of a denser silicon carbide or pyrolytic carbon film was formed on the surface of the inner layer film 12.

The inner coating 12 and the outer coating 13 are formed as follows. That is, first, the inside of a furnace in which a predetermined atmospheric gas is circulated or supplied is set at 1200 ° C. to 20 ° C.
The temperature is set to 00 ° C. In addition, silicon monoxide gas is used to generate silicon monoxide gas in a graphite crucible at 1200 ° C to 2000 ° C.
It is generated by heating to a high temperature, and is introduced through a silicon monoxide gas supply port to react with the graphite material. Residual silicon monoxide gas is exhausted from the exhaust gas port in the furnace.

The graphite material 11 whose surface has been converted to silicon carbide is transferred to a sedimentary coating zone separated by slits,
VD processing or the like is performed. A mixed gas of a silicon halide compound or the like and hydrogen gas or the like as a carrier gas is introduced from a raw material gas supply port and is supplied to a deposition coating heater for 100 hours.
An outer layer coating 13 is formed by depositing and coating dense silicon carbide or pyrolytic carbon on the graphite material 11 at 0 ° C. to 1800 ° C. For the pyrolytic carbon coating, a method similar to that of the pyrolytic carbon coating 14 described above may be employed.

Of course, the inner layer film 12 formed as described above
And the outer layer coating 13 itself has high purity, but various impurities such as iron, nickel, cobalt, and vanadium may be mixed in the graphite base material used for laminating the same, and It may remain on the inner layer coating 12. It is considered that the impurities in the inner coating film 12 and the outer coating film 13 are mixed into the above-mentioned route in which the impurities in the graphite substrate are diffused during the formation of the pyrolytic carbon, and the impurities are mixed in the supply gas. That is. These impurities do not mix into the inner layer coating 12 or the outer layer coating 13 due to the use of a high-purity graphite base material and the purity of the supply gas (select the structure and materials of the gas supply parts, supply pipes and reaction vessels, etc.). That is what you can do. By such a method, the total amount of ash (impurities such as iron) in the inner layer coating 12 and the outer layer coating 13 is reduced by 20%.
ppm or less.

[0057]

As described above in detail, in each of the inventions, as exemplified in the above-mentioned embodiment, the graphite material 11 to be the base material is entirely made of an isotropic, high-density, high-purity material.
Average thermal expansion coefficient of 1.3 to 7.0 × 10 ° C. to 400 ° C.
^-6 / ° C and the average pore radius measured by the mercury intrusion method is 1
Since a wafer having a thickness of 8000 angstroms or less is employed, it is possible to provide a wafer holding jig 10 which is excellent in heat resistance and chemical stability as a whole and is easy to process. What is more, an excellent environment for forming an oxide film or the like on each wafer 20 can be provided.

In addition to the above effects, in particular, in the wafer holding jig 10 according to the first aspect, the graphite material 11
Since the pyrolytic carbon coating 14 is formed on the surface of the substrate 20, the pyrolytic carbon coating 14 can surely prevent the graphite powder, which is likely to be an impurity, from falling off the wafers 20 and have excellent resistance to hydrofluoric acid. You can do it.

Further, the wafer holding jig 10 according to claim 2
In the above, the wafer holding jig 10 according to claim 1
You can get the same effect as in
Since the outer coating 13 made of silicon carbide or pyrolytic carbon is supported by the inner coating 12 formed by converting the surface of the graphite material 11 into silicon carbide, the adhesion strength of the outer coating 13 to the graphite material 11 is improved. Can be made even more satisfactory.

[Brief description of the drawings]

FIG. 1 is a plan view showing a state where a wafer is held by a wafer holding jig according to each invention.

FIG. 2 is a side view of the same.

FIG. 3 is a partially enlarged cross-sectional view of the wafer holding jig according to claim 1;

FIG. 4 is a partially enlarged cross-sectional view showing a wafer holding jig according to claim 2, particularly when a pyrolytic carbon film is employed as an outer layer film.

FIG. 5 is a partially enlarged cross-sectional view showing a wafer holding jig according to claim 2, particularly when a silicon carbide film is used as an outer layer film.

FIG. 6 is a normal pressure CV in which the wafer holding jig of the present invention is used.
It is a side view of D device.

[Explanation of symbols]

 Reference Signs List 10 Wafer holding jig 11 Graphite material 12 Inner layer coating 13 Outer layer coating 14 Pyrolytic carbon coating 20 Wafer 30 Normal pressure CVD apparatus

Continuation of front page (56) References JP-A-63-227783 (JP, A) JP-A-63-74995 (JP, A) JP-A-64-9900 (JP, A) JP-A-1-145400 (JP) JP-A-3-129729 (JP, A) JP-B-48-26597 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 21/205 B65D 85/00 B65D 85/86

Claims (2)

(57) [Claims] 1. The whole isotropic, high-density, high-purity, 20 ° C.
The average coefficient of thermal expansion at 400 ° C. is 1.3 to 7.0 × 10 ⁻⁶ /
C. and an average pore radius of 180 measured by a mercury intrusion method.
A wafer holding jig formed of a graphite material having a thickness of not more than 00 angstrom and holding a raw material wafer for a semiconductor element in an atmospheric pressure CVD apparatus, wherein a coating made of pyrolytic carbon is formed on a surface of the graphite material. A wafer holding jig for a normal pressure CVD apparatus, characterized in that a jig is formed. 2. The whole isotropic, high-density, high-purity, 20 ° C.
The average coefficient of thermal expansion at 400 ° C. is 1.3 to 7.0 × 10 ⁻⁶ /
C. and an average pore radius of 180 measured by a mercury intrusion method.
A wafer holding jig formed of a graphite material having a thickness of not more than 00 Å and holding a raw material wafer for a semiconductor device in a normal pressure CVD apparatus, wherein the surface of the graphite material is provided on the surface of the graphite material. Atmospheric pressure CVD characterized by being coated with an inner layer film converted to silicon carbide and an outer layer film formed by depositing and coating denser silicon carbide or pyrolytic carbon on the inner layer film.
Graphite wafer holding jig for equipment.