JPH09235163A - Heat-treatment jig and production thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-treatment jig having an excellent heat-cycle and thermal-shock resisting characteristics to be suitable for the use as a member for heat treatment in semiconductor production, and provide a method for producing the jig. SOLUTION: This jig comprises a SiC-coated silicon carbide substrate produced by forming a SiC film on a silicon-impregnated silicon carbide by CVD (chemical vapor deposition) so that no bubbles of 2μm or larger diameter are present in the substrate surface layer within 200μm from the surface of silicon carbide substrate in contact with the SiC film when observed with a 400-magnification scanning electron microscope. The method for producing the heat- treatment jig comprises introducing a raw-material compound that forms a SiC film, and forming the SiC film in a non-oxidizing atmosphere at temperature of 1000-1290 deg.C under pressure of 500-760Torr when forming the SiC film on the silicon-impregnated silicon carbide substrate by CVD.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a jig for heat treatment, which is suitable as a member for manufacturing semiconductors and has excellent heat cycle characteristics and thermal shock resistance, and a manufacturing method thereof.

For heat treatment jigs such as liner tubes, process tubes, and wafer boats used in diffusion furnaces for semiconductor manufacturing, high-purity in addition to heat cycle characteristics against rapid heat and quenching, thermal shock resistance characteristics and mechanical strength. The non-contamination property that does not contaminate the silicon wafer is required. Conventionally,
High-purity quartz glass has been used as a jig for these heat treatments. However, as the temperature of the heat treatment process has increased, quartz glass has become insufficient in high-temperature strength, and as a substitute material, US Pat. (Japanese Patent Sho 54
No. 10825) discloses a silicon carbide material impregnated with silicon. However, this material has a defect that the impurity level is high as compared with high-purity quartz glass.

[0003]

2. Description of the Related Art As means for solving this drawback, JP-A-54-90966, JP-A-54-90967, JP-A-63-35452, and JP-A-1-282 are known.
No. 152, for example, a method of forming a SiC film on the surface of a silicon carbide substrate impregnated with silicon by a CVD method (chemical vapor deposition method) to prevent evaporation of impurities is effective. Usually, the formation of the SiC film by the CVD method is performed by CH ₃ SiCl ₃ , CH ₃ S containing Si and C.
a method of thermally decomposing an organosilicon compound such as iHCl ₂ ;
Alternatively, it is formed by a method of precipitating SiC by a heating reaction of a silicon compound such as SiCl ₄ and a carbon compound such as CH _4, but a part of the silicon impregnated in the silicon carbide base material is volatilized during heating and the base material is evaporated. Porosity is likely to occur on the surface, resulting in poor adhesion between the silicon carbide base material and the SiC coating, resulting in a decrease in adhesive strength.
There is a drawback that peeling of the iC coating is likely to occur. In addition, Si
If the denseness of the C coating is impaired and pinholes are generated, a part of the impregnated silicon is eroded and eluted during chemical cleaning, resulting in pores. Therefore, impurities are likely to accumulate in the generated pores and become a source of generation of impurities. Further, there is a proposal (Japanese Unexamined Patent Publication No. 63-210276) in which the crystal growth direction of the SiC film is aligned to give the film denseness, but since the SiC film is formed at a temperature exceeding the melting point of silicon, a silicon carbide group is used. There is a problem that a large number of pores are generated in the material and the strength of the base material is reduced.

As a technique for solving this problem, silicon carbide-based ceramics impregnated with silicon is reduced to 850 under reduced pressure.
A silicon-impregnated silicon carbide that is heated to ℃ to 1000 ℃, introduces a reaction gas that produces SiC to start the film formation of SiC and raises the temperature without cooling to form a film at a temperature of 1200 to 1400 ℃. A method of forming a silicon carbide coating on a fine ceramic has been proposed by one of the present applicants (Japanese Patent Laid-Open No. 4-65374). According to this method, by starting the formation of the SiC coating at a temperature of 1000 ° C. or less at which the evaporation rate of silicon is low, 1000 ° C.
Even if the temperature is increased above, the effect of suppressing evaporation of silicon is brought about by the formed film.

[0005]

However, in a material in which a SiC film is formed on a silicon carbide base material impregnated with silicon by the CVD method, the heat cycle characteristics and the heat shock characteristics depend on the texture of the interface of the SiC coating layer. Change subtly, and when used as a semiconductor member that is subjected to severe heat history, there is a problem that a crack occurs in the SiC coating or the SiC coating peels off.

The inventors of the present invention have conducted extensive studies in order to elucidate the above-mentioned cause. As a result, the pores existing in a specific surface layer portion of the silicon carbide base material in contact with the coated SiC film and the properties of the SiC film are heat-resistant. It was confirmed that it affects the cycle characteristics and thermal shock resistance characteristics.

The present invention has been developed on the basis of the above findings, and its object is to provide a heat treatment jig and a manufacturing method thereof that exhibit excellent heat cycle characteristics and thermal shock resistance characteristics when used in the manufacture of semiconductors. To provide.

[0008]

A jig for heat treatment according to the present invention for achieving the above object is a SiC-coated silicon carbide material in which a SiC film is formed by a CVD method on a silicon carbide base material impregnated with silicon. The silicon carbide base material is SiC
In the surface layer of the base material within 200 μm from the interface in contact with the coating,
When the surface layer portion is observed and measured with a scanning electron microscope at a magnification of 400 times, it is characterized in that there are no pores having a diameter of 2 μm or more.

Normally, the interlayer strength when a SiC substrate is coated with SiC by the CVD method is largely controlled by the denseness and adhesion of the layer interface portion, but silicon carbide impregnated with silicon is used as the substrate. In the coating structure, the texture density of the surface layer within a depth of 200 μm in the silicon carbide base material in contact with the SiC coating has a significant effect on the interlaminar strength, and the presence of pores with a diameter of 2 μm or more within 200 μm causes a thermal history. When this happens, cracks and peeling easily occur in the interlayer structure. Therefore, the silicon carbide substrate specified in the present invention is Si
By forming a microstructure having no pores with a diameter of 2 μm or more in the surface layer of the base material within 200 μm from the interface in contact with the C coating, heat cycle characteristics and thermal shock resistance that sufficiently endure severe thermal history are imparted. The pore diameter is observed and measured with a scanning electron microscope at a magnification of 400 times.

In addition to the above requirements, the ratio of the diffraction intensity value of the (200) plane to the (111) plane in the X-ray diffraction of the formed SiC film, I (200) / I (111), is set to 0.
When it is 005 or less, the thermal shock resistance of the material can be further improved by strengthening the orientation of the SiC film crystal to the (111) plane. The diffraction intensity value by X-ray diffraction in this case is a value measured by Kα of Cu, and the X-ray diffraction intensity is an applied voltage of 40 KV and an applied current of 20 m.
Measured under the conditions of A, filter Cu / Ni, and divergence slit 1 °.

Further, according to the method for manufacturing a heat treatment jig of the present invention, the surface of a silicon carbide substrate impregnated with silicon is subjected to CVD.
In forming the SiC coating by the method, a raw material compound for forming the SiC coating is introduced, and the raw material compound is placed in a non-oxidizing atmosphere for 10 minutes.
The structural feature is that the SiC film is formed at a temperature of 00 to 1290 ° C. and a pressure of 500 to 760 Torr.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The silicon carbide base material impregnated with silicon, which is the base material of the present invention, is obtained by impregnating recrystallized silicon carbide obtained by heat-treating a molded body of silicon carbide at high temperature with molten silicon. Or a molded body of silicon carbide and carbon impregnated with molten silicon and then heat-treated at high temperature to form a reaction sintered silicon carbide. The silicon content is about 10 to 30% by weight.

CV is formed on the surface of the silicon-impregnated silicon carbide substrate.
As a method of forming the SiC coating by the D method, 600 to 85 at a temperature rising rate of 5 to 50 ° C./min after deaeration under reduced pressure of 1 Torr or less.
First step of heating to a temperature of 0 ° C., then 50-760
After introducing a non-oxidizing gas to a pressure of Torr, the second step of further heating to a temperature of 1000 to 1290 ° C. at a temperature rising rate of 5 to 50 ° C./min, and subsequently 500 to 760 Torr
It is preferable to apply the third step in which the raw material compound is introduced together with the carrier gas and the raw material compound is thermally decomposed or chemically reacted at a temperature of 1000 to 1290 ° C. to form a SiC film. Examples of the raw material compound include CH ₃ SiC containing Si atom and C atom in one molecule.
l _3, CH ₃ which are used in combination with carbon compounds such as organosilicon compounds, such as SiHCl _2, or silicon compounds such as SiCl ₄ and CH ₄ is exemplified. Examples of the carrier gas include non-oxidizing gases such as hydrogen gas and argon gas. Further, upon introduction, it is preferable that the carrier gas and the raw material compound have a molar ratio (carrier gas / raw material compound) of 4 to 100. In the calculation of this molar ratio, when a silicon compound and a carbon compound are used together as raw material compounds, the number of moles converted to silicon carbide is the number of moles of the raw material compound.

The temperature rising rate in the first step and the second step is set to 5 to 50 ° C./min. When the temperature rising rate exceeds 50 ° C./min, thermal stress is generated in the base material and cracks occur. And less than 5 ° C./min, the temperature rise is slow and the productivity is poor. A more preferable temperature rising rate is 10 to 30 ° C./min. In the first step,
If the pressure after degassing exceeds 1 Torr, the surface of the silicon carbide base material is oxidized by residual oxygen and moisture, and the corrosion resistance is reduced and the adhesion of the SiC coating is reduced, which is not preferable.
Further, if the heating temperature is lower than 600 ° C., the removal of adsorbed oxygen and the like becomes insufficient and the surface of the silicon carbide base material is easily oxidized, which is not preferable. On the other hand, if the heating temperature exceeds 850 ° C., silicon is evaporated under reduced pressure and pores are easily generated in the silicon carbide base material, and the adhesion of the SiC coating is deteriorated, which is not preferable. Furthermore, in the second step, when the pressure exceeds 760 Torr, the hydrogen gas is likely to leak and the hydrogen gas is wasted.
Further, the pressure vessel needs to be strengthened and the equipment becomes complicated, which is not preferable.

In the second step and the third step, the temperature rising conditions below the vapor pressure of silicon and the temperature and pressure of the CVD reaction system are controlled so that the silicon on the surface impregnated in the silicon carbide base material does not volatilize by heat. By controlling the conditions, the heat treatment jig made of the SiC-coated silicon carbide of the present invention can be obtained. That is, when the pressure in the second step is less than 50 Torr, and in the third step exceeds 1290 ° C,
Under a temperature and pressure condition of less than 00 Torr, pores are formed in the surface layer portion of the base material because the silicon in the surface layer portion impregnated in the silicon carbide base material is thermally evaporated. Further, if the heating temperature in the third step is less than 1000 ° C., the heat vaporization of silicon is suppressed but the growth rate of the SiC coating is reduced, which is not practical. In the third step, at a pressure exceeding 760 Torr, the gas of the raw material compound produces silicon carbide powder before the chemical vapor deposition on the surface of the silicon carbide base material, so that the production rate of the SiC film is suppressed.

In addition to the above-described method for suppressing the generation of pores in the base material, the crystal properties of the SiC coating formed by the CVD method and having high thermal shock resistance, that is, the crystal plane of the (111) plane on the base material is highly enhanced. The SiC film grown by orientation has a molar ratio of a carrier gas such as hydrogen or argon to a raw material compound of 4 to 100, preferably 5 to 20 under conditions of a temperature of 1100 to 1290 ° C. and a pressure of 500 to 760 Torr.
It is achieved by controlling to. When the temperature is lower than 1100 ° C, the thermal shock resistance of the SiC coating deteriorates. Further, when the carrier gas / raw material compound molar ratio is less than 4, the SiC film formed tends to become crystal nuclei on the surface of the silicon carbide base material, resulting in coarsening of the formed SiC film, resulting in a decrease in denseness. This is because the polycrystallization in (3) is likely to occur and the orientation of the SiC film crystal on the (111) plane is lowered.

CVD on a silicon carbide substrate impregnated with silicon
When used as a member such as a heat treatment jig that undergoes a severe thermal cycle, the material coated with SiC by the method causes cracks and peeling between layers, resulting in defects.
The main cause is that silicon impregnated during coating by the method D is volatilized and pores having a diameter of 2 μm or more are present in the surface layer portion of the base material, particularly the surface layer portion within a depth of 200 μm in the silicon carbide base material in contact with the SiC coating. Since the jig for heat treatment of the present invention does not have pores having a diameter of 2 μm or more in the surface layer portion of the silicon carbide base material within 200 μm in contact with the coated SiC film, S
The iC coating firmly adheres to the silicon carbide base material, and when used as a heat treatment jig, exhibits excellent durability performance against heat cycles of rapid heating and rapid cooling.

Further, the ratio of the diffraction intensity values of the X-ray diffraction of the SiC coating, I (200) / I (111), is set to 0.005 or less so that the (111) plane of the crystal structure of the SiC coating is adjusted. By strengthening the orientation, since the (111) plane is a close-packed crystal plane, the chemical bonding force between the silicon carbide and silicon forming the silicon carbide base material and the SiC coating increases, so that the SiC coating The thermal shock resistance can be further improved.

[0019]

Hereinafter, examples of the present invention will be described in detail in comparison with comparative examples.

Examples 1 to 6 and Comparative Examples 1 to 20 Silicon was added to 50 × 50 × 10 mm recrystallized silicon carbide.
A silicon carbide base material was obtained by impregnating it with a weight percentage. The base material was placed in an annular furnace, the gas contained in the base material was degassed under a vacuum of 2 × 10 ⁻³ Torr, and the temperature was raised to 800 ° C. at a heating rate of 20 ° C./min. It was introduced and the pressure was kept at 150 Torr for 30 minutes. Next, after heating at a temperature rising rate of 20 ° C./min to raise the temperature to that shown in Table 1 and holding for 30 minutes, SiC
Using CH ₃ SiCl ₃ as a starting compound for film formation, the molar ratio of hydrogen gas (H ₂ / CH ₃ SiC
l ₃ ) was changed and supplied. At this time, the supply amount was changed to adjust the furnace pressure to a predetermined pressure. In this way, the silicon carbide base material was coated with SiC by changing the temperature in the furnace, the pressure in the furnace and the molar ratio of the raw material gas when the SiC film was formed.

Examples 7 to 9 and Comparative Examples 3 to 4 50 × 50 × 10 mm reaction-bonded silicon carbide substrate (residual Si
1.7% by weight) was degassed under the same conditions as in Example 1, and then 33
The temperature was raised to 700 ° C. at a heating rate of ° C./min, argon gas was introduced, and the pressure was kept at 300 Torr for 20 minutes. Then, after heating to a temperature shown in Table 2 at a temperature rising rate of 10 ° C./min, SiCl was used as a raw material gas for forming a film of SiC.
₄ and CH ₄ , using a molar ratio to argon gas (2A
r / SiCl ₄ + CH ₄ ) is changed and supplied.
In the same manner as in 6, the furnace temperature and the furnace pressure were adjusted to coat the silicon carbide base material with SiC.

Comparative Example 5 The same silicon carbide substrate as in Examples 1 to 6 was degassed under the same conditions as in Examples 1 to 6 and then heated to 950 ° C. at a temperature rising rate of 20 ° C./min.
After the temperature is raised to 1, the pressure is increased to 150 Torr by introducing hydrogen gas to 30 Torr.
Hold for 1 minute, then 1300 ℃ at a heating rate of 20 ℃ / minute
After raising the temperature to 1, the raw material gas (H ₂ / CH ₃ SiCl ₃ molar ratio of 4.0) was supplied while maintaining the furnace pressure at 200 Torr to coat the SiC film on the silicon carbide base material.

Comparative Example 6 The same reaction-bonded silicon carbide substrate as in Example 7 was degassed under the same conditions as in Example 1, and then 1100 at a temperature rising rate of 10 ° C./min.
The temperature is raised to ℃ and the pressure is increased to 15 Torr by introducing argon gas.
It was adjusted to and held for 20 minutes. Then, after heating to 1200 ° C. at a temperature rising rate of 20 ° C./min, SiCl ₄ and CH ₄ are used as a raw material gas for forming the SiC film, and the pressure is set to 4
The molar ratio to argon gas (2A
r / SiCl ₄ + CH ₄ ) was supplied as 2.5.

Then, the SiC-coated silicon carbide materials obtained in the above-mentioned Examples and Comparative Examples were cut, and the cross section thereof was examined by a scanning electron microscope at a magnification of 400 times to find pores having a diameter of 2 μm or more in the surface layer portion within 200 μm. Presence was observed and measured. Further, the diffraction intensity of X-ray diffraction was measured to obtain the diffraction intensity ratio I (200) / I (111). For X-ray diffraction, applied voltage 40KV, applied current 20mA, filter Cu / N
i, the divergence slit was measured at 1 °.

With respect to the SiC-coated silicon carbide material thus obtained, the temperature inside the furnace, the pressure inside the furnace and the molar ratio of the raw material gas at the time of forming the SiC film, and the SiC film in contact with the SiC film 200
Tables 1 and 2 show the presence / absence of pores having a diameter of 2 μm or more in the surface layer of the substrate within μm, the X-ray diffraction intensity and the ratio of the diffraction intensity.

[0026]

[Table 1] (Table Note) * 1 A; H ₂ / CH ₃ SiCl ₃ molar ratio * 2 Presence of pores with a diameter of 2 μm or more within 200 μm of the surface layer of the base material. * 3 I (200) / I (111) diffraction intensity ratio.

[0027]

[Table 2] (Table Note) * 1 B; 2Ar / (SiCl ₄ + CH ₄ ) molar ratio * 2 Presence of pores with a diameter of 2 μm or more within 200 μm of the surface layer of the base material. * 3 I (200) / I (111) diffraction intensity ratio.

Next, these SiC-coated silicon carbide materials were tested for thermal cycle characteristics and thermal shock resistance by the following methods, and the results are shown in Tables 3 and 4.
The heat resistance cycle characteristic is 13
After raising the temperature to 00 ° C. for 15 minutes and holding for 15 minutes, the cycle of taking out from the heating furnace, allowing to cool and returning to normal temperature was repeated 20 times, and the occurrence of cracks and the peeling state of the SiC coating surface were observed. Regarding the thermal shock resistance, the generation of cracks and the peeling state of the SiC coating surface were observed when the material was held in an electric furnace at a temperature of 500 ° C and 1000 ° C for 30 minutes, then put in water at 20 ° C and rapidly cooled.

[0029]

[Table 3]

[0030]

[Table 4]

From the results of Tables 1 to 4, in the SiC-coated silicon carbide material of the present invention, the silicon carbide base material is in contact with the SiC coating 200.
Since there are no pores with a diameter of 2 μm or more in the surface layer of the base material within μm, cracks and peeling do not occur even when subjected to heat treatment in which heating and cooling are repeated at high temperatures.
It can be seen that the durability is high even against thermal shock of quenching from a temperature of 0 ° C to a temperature of 20 ° C. In addition, X of the SiC film
By setting the ratio I (200) / I (111) of the diffraction intensity values of the line diffraction to 0.005 or less, the durability against the thermal shock of quenching from the temperature of 1000 ° C. to the temperature of 20 ° C. is improved. However, in each of the comparative examples in which the presence of pores was recognized, cracks were generated in the SiC coating, and further peeling was recognized in part of the coating.

[0032]

As described above, since the SiC-coated silicon carbide material of the present invention has excellent heat cycle characteristics and thermal shock resistance, it is used under a temperature condition where it is rapidly heated or cooled from a high temperature to a low temperature. It is extremely useful as a heat treatment jig for semiconductor manufacturing.

Front page continuation (72) Inventor Hisao Yamamoto 5-6-1, Umei, Takasago-shi, Hyogo Asahi Glass Co., Ltd. Takasago Plant (72) Innovator Nobuo Kageyama 5-6-1 Umei, Takasago, Hyogo Takasago Asahi Glass Co., Ltd. in the factory

Claims (7)

[Claims] 1. A CV on a silicon carbide substrate impregnated with silicon.
A SiC-coated silicon carbide material having a SiC coating formed by the D method, wherein the silicon carbide base material is at a surface layer portion of the base material within 200 μm from the interface in contact with the SiC coating, and the surface layer portion is magnified 400 times by a scanning electron microscope. A jig for heat treatment, characterized in that it has no pores with a diameter of 2 μm or more when observed and measured at a magnification of. 2. The (11) in X-ray diffraction of a SiC coating
The ratio of the diffraction intensity value of the (200) plane to the 1) plane, I (2
00) / I (111) is 0.005 or less.
The heat treatment jig described. 3. When forming a SiC film on a surface of a silicon carbide base material impregnated with silicon by a CVD method, Si is used.
Introducing a raw material compound for forming a C coating, in a non-oxidizing atmosphere, at a temperature of 1000 to 1290 ° C., 500 to 760 Torr
Of manufacturing a jig for heat treatment for forming a SiC film under the pressure of. 4. The method for manufacturing a heat treatment jig according to claim 3, wherein the temperature is 1100 to 1290 ° C. 5. The raw material compound is introduced together with a carrier gas, and its molar ratio (carrier gas / raw material compound).
Is 4-100, The manufacturing method of the jig for heat processing of Claim 4. 6. The method for manufacturing a jig for heat treatment according to claim 5, wherein the molar ratio of the carrier gas and the raw material compound is 5 to 20. 7. A silicon carbide base material impregnated with silicon is 1 To
After degassing to rr or less, 600 ~ at a heating rate of 5 ~ 50 ° C / min
First step of heating to a temperature of 850 ° C., 50 to 760 Torr
5 ~ 50 ℃ / min after introducing non-oxidizing gas until
Second step of heating to 1000 to 1290 ° C. at a heating rate of 1, a carrier gas and a raw material compound that forms silicon carbide are introduced to form a SiC coating on the surface of the silicon carbide base material at 1000 to 1290 ° C. and 500 to 760 Torr. A method for manufacturing a heat treatment jig, comprising: a third step.