JPH0925185A - Silicon carbide film coated member and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress impurity diffusion from a base material and to improve corrosion resistance against fluorine plasma etching, polishing characteristics and mirror surface converging accuracy by CVD treating an SiC base material after previously heat treating at a temp. higher than the CVD treating temp. SOLUTION: A CVD treating furnace in which the SiC base material is arranged is heated at the rate of 100-600 deg.C/hr and is kept at a temp. range from at least 1.05 times of the CVD treating temp. to that lower than the m.p. of the SiC base material (e.g. <=1400 deg.C) for 0.5-2.0hr. Thereafter, the furnace is cooled to the CVD treating temp. and is kept for a prescribed period, the SiC film having the low oxygen content of <=30ppm (by weight) and >=20μm in film thickness is applied on the surface of the SiC base material by CVD treatment while passing a CVD gaseous starting material to remove moisture or the like being an oxygen source in the furnace members or the base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a silicon carbide coated member and a method for manufacturing the same, and more particularly, to a furnace core tube used in a heat treatment step in semiconductor manufacturing, jigs such as wafer boats, and plasma etching in semiconductor manufacturing. Susceptor or synchrotron radiation (SOR) used in the process
The present invention relates to a silicon carbide coated member used as a mirror for reflecting high energy light such as light) and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, in a semiconductor manufacturing process,
Various members mainly composed of silicon carbide are used.
In particular, a reaction-sintered SiC (Si) obtained by impregnating a molded body of silicon carbide (SiC) and carbon (C) with silicon (Si)
-SiC) A member whose surface is covered with a SiC film has excellent heat resistance and corrosion resistance, has an extremely low content of metal impurities, can suppress the diffusion of metal impurities from the inside of the base material into the wafer, and has dense internal pores. It has high hardness without
It has excellent features such as excellent polishing characteristics and is used as a base material for heat treatment jigs for semiconductor manufacturing and mirrors for SOR light. The above characteristics are mainly due to the characteristics of the CVD-SiC film coated on the surface, and when used as a heat treatment jig for semiconductor manufacturing or a mirror for SOR light,
The CVD-SiC film generally needs to be coated with a film thickness of 20 μm or more, and is usually formed by a thermal CVD method.

[0003]

However, for example, a conventional CVD-SiC CVD-SiC formed on the inner surface of a reaction-sintered SiC tube as a furnace core tube for a semiconductor diffusion furnace.
The film was not sufficient for the recent semiconductor manufacturing in which ultra high purity is required because the outward diffusion of metal impurities from the furnace core tube base material or the furnace core tube outer periphery is not sufficiently suppressed. . Further, as a susceptor for semiconductor plasma etching, a conventional CVD-SiC film formed on the surface of a reaction-sintered SiC plate by the conventional thermal CVD method cannot be said to have sufficient corrosion resistance to fluorine plasma serving as an etching medium,
The replacement frequency was high. Furthermore, as a mirror for synchrotron radiation reflection, a conventional CVD-SiC film formed on the surface of a self-sintered SiC substrate by a thermal CVD method,
In the diamond polishing of the light-reflecting surface, a sufficient mirror surface could not be formed, and therefore, a sufficient value was not obtained in converging accuracy. The inventors of the present invention used the above thermal CVD method to produce Si.
Fundamentally and comprehensively, the fact that various semiconductor manufacturing members coated with a C film could not sufficiently exhibit the performance in various applications was examined. As a result, it was found that all of them are deeply related to the oxygen concentration in the CVD-SiC film, and by setting the oxygen concentration in the CVD-SiC film of each member to a predetermined value or less, the performance of each member can be improved. Therefore, the present invention has been completed.

[0004]

According to the present invention, SiC
Si on the surface of high quality substrate by CVD method to a thickness of 20 μm or more
There is provided a silicon carbide film-covered member which is formed by coating a C film and has an oxygen concentration in the SiC film of 30 ppm (weight) or less.

The silicon carbide film-coated member of the present invention is constructed as described above, and CVD-S coated on the surface of the SiC-based substrate.
Since the oxygen content of the iC film is 30 ppm or less, it is excellent in suppressing the diffusion of impurities, has a sufficient effect on the corrosion resistance to fluorine plasma, and has high flatness by surface polishing with diamond or the like. Therefore, for example, it is possible to exhibit high focusing accuracy of the synchrotron radiation light.

Further, according to the present invention, a CVD treatment furnace for arranging a SiC base material is used at 100 to 600 ° C./hour for 1000 to 1
The temperature is raised to a high temperature that is higher than the CVD treatment temperature of 300 ° C. and lower than the melting point of the SiC-based substrate, and is held at the high temperature for a predetermined time, and then, is lowered to the CVD temperature and is held for a predetermined time, and then CVD is performed. Provided is a method for manufacturing a silicon carbide film-coated member, which is characterized in that a source gas is circulated and a CVD process is performed. In the method for manufacturing a silicon carbide film-coated member of the present invention, the high temperature is at least 1.0 of the CVD processing temperature.
It is preferable that the temperature is 5 times or more and 1400 ° C. or less. Further, it is preferable that the predetermined time of holding at the high temperature is 0.5 to 2.0 hours. Furthermore, it is preferable that the SiC base material is made of reaction-sintered SiC.

In the method for manufacturing a silicon carbide film-coated member of the present invention, the temperature is raised to a predetermined temperature equal to or higher than the CVD processing temperature at a predetermined temperature rising rate, and the temperature is maintained for the predetermined time, and then the CV is applied.
D The temperature is lowered to the treatment temperature, and the temperature is further maintained at the CVD treatment temperature for a predetermined time, and then the same CVD treatment as in the conventional method is performed, whereby moisture or the like serving as an oxygen source in the furnace member and the base material can be removed and formed. The CVD-SiC film has a low oxygen content, and a silicon carbide film coating member having a low oxygen content can be obtained.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the silicon carbide-coated member of the present invention, the base material coated with silicon carbide may be, for example, reaction-sintered SiC (Si-SiC), which is conventionally known as a heat-resistant base material. The present invention utilizes the high strength of the above reaction-sintered SiC at high temperature, and at the same time, prevents the impurities contained therein from scattering or diffusing.
Prevent by D-SiC film coating, and further coating CVD-
It improves the properties of the SiC film. Further, the CVD-SiC film of the present invention is formed to have a thickness of 20 μm or more like the conventional CVD-SiC film. Below 20 μm,
This is because the characteristics of the SiC film cannot be sufficiently exhibited. The oxygen concentration in the CVD-SiC film coated on the reaction sintered SiC substrate of the present invention is 30 ppm or less, preferably 10 ppm or less. This is because when it exceeds 30 ppm, the presence of SiO _{2 in} the film cannot be ignored. In this case, the oxygen concentration is most preferable to be zero, but it is difficult to set it to zero in view of the CVD processing operation, and 0.3 ppm was the minimum value in Examples described later.

The above CVD-SiC film of the present invention is a thermal CV film.
It can be obtained by increasing the temperature to or above the CVD processing temperature at a predetermined temperature rising rate before the D processing step and then processing at the CVD processing temperature. The inventors have for the first time found that maintaining the temperature at or above this CVD treatment temperature is effective for coating a CVD-SiC film of reaction-sintered SiC. That is, the formation of CVD-SiC by the thermal CVD method is reported to be 1200 to 2200K (92
7 to 1927 ° C.) in a wide temperature range, but in a practical CVD process, the material changes from the material of the base material to that of the base material. No setting has been considered from the viewpoint of maintaining the base material. For example, when reaction-sintered SiC is used as the base material, since silicon exists in the base material, the melting point of silicon is less than 1420 ° C., usually about 1000.
The CVD process is performed at ˜1300 ° C. However, the present inventors have the fact that oxygen is contained in a high concentration in a normal CVD-SiC coating, and according to the present inventors, particularly, a carbon material or the like is used in a CVD furnace. If it is present, the oxygen content will be high, so it will be adsorbed to jigs used in the base material or in the CVD furnace even at the normal processing temperature for coating the SiC film on the reaction-sintered SiC by CVD processing. And recognize that the contained water, CO, and CO ₂ gas have not been completely removed, so that a method that can remove the oxygen source in the furnace as much as possible by a simple operation is studied. As a result, after processing at a temperature higher than the CVD processing temperature, the SiC coating was performed by the CVD processing. Further, the temperature of the high temperature treatment and the CVD treatment process, the holding time thereof, the treatment temperature pattern such as the temperature drop rate, were examined.

That is, FIG. 1 is a relational diagram of temperature and time showing the temperature process in the CVD furnace. In FIG. 1, 0-A is a temperature raising step, AB is a step of maintaining the temperature at point A reached by the temperature raising, BC is a temperature decreasing step,
CD is a process of maintaining the temperature at point C. Also, E
-F is a step of maintaining the temperature at point E in the middle of temperature raising step 0-A up to point F. In FIG. 1, the temperature raising rate in the 0-A temperature raising step is the same as the temperature raising rate of a normal CVD processing furnace, and can be performed at 100 to 600 ° C./hour. Points E, F, C, and D are all temperatures of the CVD process, and when reaction-sintered SiC is used as the base material, the CVD process is performed at about 1000 to 1300 ° C. as in the conventional case. Points A and B are temperatures around the melting point of Si contained in the reaction-sintered SiC and are about 1350 to 1400 ° C. In the 0-EF line process, when the CVD processing temperature is almost reached, the CVD process is performed.
To start. This pattern is a conventional CVD-SiC film coating pattern, and is a CV pattern without high temperature treatment.
Since the D treatment is started, the oxygen concentration in the CVD-SiC film is high as in the conventional case. 0-A-B-C-D
The process pattern for starting the CVD process in the line process was examined. When the CVD process is started at the point A or B near the melting point of silicon, the holding time at 1400 ° C. is 1.5
If the time is set longer than the time, the water removal is sufficient, but the resulting CVD film is not preferable as a heat treatment jig for semiconductors or a mirror because it has a crystal form in which columnar crystals are significantly developed. Further, if the CVD process is started directly at the point C where the temperature has dropped, the temperature becomes unstable and the reproducibility of the film quality is poor, which is not preferable. CV in 0-E-C-D line process
The pattern in which the CVD process is started by holding the D process temperature for a relatively long time shows a slight reduction as compared with the conventional method.
Moisture and CO gas in the furnace are not sufficiently removed, and the oxygen concentration cannot be reduced.

The CVD process in the production of the silicon carbide film coated member of the present invention employs the temperature process of the 0-A-B-C-D line in FIG.
This is the method of starting the process. That is, the temperature is raised to a temperature higher than the CVD processing temperature, the temperature is maintained for a predetermined time,
In this method, the temperature is lowered to the D processing temperature, and then the CVD processing is performed in a temperature step in which the CVD processing is started by holding the temperature for a predetermined time. In this case, the temperature reached at the point A is 1000 to 13
The temperature is higher than the CVD treatment temperature of 00 ° C. and lower than the melting point of the SiC substrate, preferably at least 1.05 times the normal CVD treatment temperature of 1000 to 1300 ° C., and 1400 ° C. The temperatures are as follows:
Generally, if the temperature at point A is the melting point of the SiC-based substrate, for example, 1420 ° C. or higher, the silicon in the substrate melts and at the same time the substrate cannot maintain its shape, which is not preferable. on the other hand,
If the temperature is less than 1.05 times 1000 to 1300 ° C. of the CVD processing temperature, for example, less than 1030 ° C., it takes a long time to remove water and CO gas in the furnace and the efficiency is low. It is preferable to perform high temperature treatment in the range of ° C. Further, the holding time differs depending on the shape of the furnace body and the capacity of the carbon material used in the furnace, and may be appropriately selected according to each processing condition. Usually, it is sufficient to set the temperature to a predetermined temperature and then set the CVD process for about 0.5 to 4.0 hours, and preferably hold the high temperature treatment temperature for about 0.5 to 2.0 hours. Then, the temperature is lowered to the CVD processing temperature and maintained for about 1.0 to 2.0 hours. If the holding time at the above-mentioned high temperature treatment is less than 0.5 hours, the oxygen concentration cannot be sufficiently reduced, and even if the treatment is performed for more than 2.0 hours, the substantial effect is the same. Considering the manufacturing cost, it is preferably 2.0 hours or less.

[0012]

EXAMPLES The present invention will be described in more detail based on examples. However, the present invention is not limited to the following examples. Example 1 The surface of a reaction-sintered SiC-based substrate was subjected to a high temperature treatment and a CVD-SiC coating treatment as described below in the temperature step indicated by the 0-A-B-C-D line in FIG. In FIG. 1, the temperature raising step of 0-A was performed from room temperature to 1400 ° C. at a temperature raising rate of 400 ° C./hour in about 3.5 hours. afterwards,
After holding A-B at 1400 ° C. for 60 minutes, B-C
The temperature was dropped to 1200 ° C. in 1 hour. Further, the CD was held at 1200 ° C. for 60 minutes. After that, at the point D, at 1200 ° C., the raw material gas SiCl
₄ , CH ₄ and H ₂ are 0.5, 0.
Supply and distribute at 3 and 2.0 liters / minute for 150 minutes C
VD treatment was applied to cover a 50 μm thick SiC film.

The oxygen concentration in the CVD-SiC film formed above was measured. The oxygen in the CVD-SiC film was measured by SIMS (secondary ion mass spectrometry).
In this oxygen measuring method, the S
An iC standard sample was prepared, and a relative sensitivity coefficient (RSF) C _R was calculated from the following formula (1) from the Si ion strength and oxygen ion strength in SiC, and the sample was calculated from the obtained RSF by the following formula (2). The oxygen concentration D _{S in the} inside was calculated. This S
The oxygen concentration quantitative measurement by IMS can be easily performed with a sensitivity of ppm or less and an accuracy of about 10 to 20%. However, in the formula, D _O is the oxygen concentration (number of atoms / cm ² ) injected into the standard sample, I _r is the measured ionic strength of the matrix (Si or carbon (C)), and I _s is the measurement of oxygen element in the sample. Ionic strength, d represents the measurement depth (cm), and n represents the number of data up to the measurement depth. C _R = D _O · I _r · n / d · ΣI _s (1) D _S = C _R · I _s / I _r (2) In this embodiment, the oxygen concentration is 1 × 10 ¹⁵ atoms / cm 2.
Prepare a SiC standard sample adjusted to ² and
Using Elmer 6600 SIMS, primary ion species C
s ⁺ , primary ion acceleration voltage 5 KeV, primary ion current 5
The measurement was performed at a depth of about 2 μm from the surface under the conditions of 00 nA, raster region 200 × 315 (μm), and analysis region 90 × 140 (μm). As a result, the oxygen concentration was 3 ppm.

Examples 2 to 6 In the temperature process chart of FIG. 1, the temperature at the point A, the holding time at the point AB, the temperature at the point C and the holding time at the point C-D were changed as shown in Table 1, respectively. And Fe concentration 100ppm 1
A CVD-SiC film having a film thickness of 50 is formed on the surface of a 0x5x50 (mm) plate-shaped reaction sintered SiC material in the same manner as in Example 1.
coated with μm. Each Si measured in the same manner as in Example 1
Table 1 shows the oxygen concentration of the C film. At this time, the oxygen concentration is 0.
An attempt was made to form a CVD-SiC film having a content of less than 3 ppm, but it was not possible. The results of Example 1 are also shown in Table 1.

[0015]

[Table 1]

Comparative Examples 1 to 2 In the temperature process chart of FIG. 1, the temperature was raised up to point E in the same manner as in Example 1, then the temperature was maintained up to point E-F at the time shown in Table 2, and thereafter, As with the conventional CVD processing method, F
From this point, a CVD process was performed in the same manner as in Example 2 to coat a SiC film having a thickness of 50 μm. Table 2 shows the oxygen concentration of each SiC film measured similarly.

[0017]

[Table 2]

(Impurity Diffusion Evaluation Test) Above Examples 2 to 2
Diffusion evaluation of impurities was performed on the SiC plate samples coated with the respective CVD-SiC films obtained in Example 4 and Comparative Examples 1 and 2. In each of the heating devices shown in FIG.
e) It was put in 100 g of high-purity quartz powder 1 having a content of 0.001 ppm, the inside of the apparatus was made into an Ar atmosphere, and the heating was controlled to 1300 ° C. by using the thermocouple 3 by the external heater 2,
Heat treatment was performed for 1,000 hours and 2000 hours. After taking out the sample after each time, Fe in the quartz powder
The amount of increase was measured. The results are shown in Fig. 3. It is clear from FIG. 3 that the CVD-SiC film-coated reaction-sintered SiC substrate of the present invention has a high effect of preventing diffusion of impurities.

(Fluorine Plasma Etching Corrosion Resistance Evaluation Test) Each C obtained in the above Examples 2 to 4 and Comparative Examples 1 and 2
The SiC plate sample coated with the VD-SiC film was measured for corrosion resistance to fluorine plasma. A CDE (Chemical Dry Etching Equipment) is used as the test equipment, the output is 600 W, the CF ₄ flow rate is 120 cc / min in the standard state, and O
₂ flow rate in standard condition 40cc / min, sample temperature 150 ° C,
The etching rate by fluorine plasma of each sample surface was measured under the condition of exposure time of 100 minutes. Table 3 shows the results. Based on this corrosion resistance evaluation, the CVD-SiC of the present invention
It is clear that the film-coated reaction-sintered SiC substrate has an etching rate of one digit better than that of the comparative example and is excellent in fluorine plasma resistance. It is presumed that this is because the oxygen content is small and there is almost no Si—O bond.

[0020]

[Table 3]

(Polishing Characteristic Evaluation Test) S of each CVD-SiC film coating obtained in Examples 2 to 4 and Comparative Examples 1 to 2 above.
The polishing characteristics of the iC plate sample were evaluated. The surface of each sample was buffed with a diamond paste, and the surface roughness of the obtained mirror surface was measured. The results are shown in Table 4. As is clear from Table 4, the CVD-SiC of the present invention
It can be seen that the film-coated reaction-sintered SiC material has a better surface than the comparative example. Further, as a result, it is estimated that the CVD-SiC film of the present invention is as close as possible to compositionally uniform SiC, and the difference in physical properties (hardness) is small.

[0022]

[Table 4]

[0023]

The silicon carbide film-covered member of the present invention is formed by CVD.
Prior to the treatment, it is manufactured by performing a heat treatment in advance at a high temperature equal to or higher than the CVD treatment temperature and then performing a CVD treatment. The silicon carbide film-coated member obtained by the method of the present invention is made of Si
Since the oxygen concentration of the CVD-SiC film coated on the surface of the C-type substrate is significantly reduced as compared with the conventional CVD-SiC film, the diffusion of impurities from the substrate is suppressed and the fluorine plasma etching is performed. It is possible to obtain a mirror surface with excellent corrosion resistance and excellent polishing characteristics and good condensing accuracy. For example, various materials such as a furnace core tube of a semiconductor diffusion furnace, a susceptor for semiconductor plasma etching, and a base material for a mirror for synchrotron reflection light, etc. Can be suitably used as a structural member material in the semiconductor manufacturing process.

[Brief description of drawings]

FIG. 1 is a relationship diagram of temperature and time showing a temperature process in a CVD furnace in the present invention.

FIG. 2 is a schematic diagram of an impurity diffusion test furnace used in an example of the present invention.

FIG. 3 is a diagram showing the relationship between the heat treatment time and the amount of increase in impurities (Fe) showing the results of the impurity diffusion test in Examples and Comparative Examples of the present invention.

[Explanation of symbols]

 S sample 1 filled quartz powder 2 heater 3 thermocouple

Front page continuation (72) Inventor Shigeo Kato 378 Oguni-machi, Oguni-cho, Nishiokitama-gun, Yamagata Prefecture In the Oguni Factory of Toshiba Ceramics Co., Ltd. Company Oguni Factory

Claims (5)

[Claims] 1. A surface of a SiC substrate is coated with a SiC film having a thickness of 20 μm or more by a CVD method, and
A silicon carbide film-covered member, wherein the oxygen concentration in the iC film is 30 ppm (weight) or less. 2. A CVD furnace in which a SiC substrate is placed at 100 to 600 ° C./hour and a CV of 1000 to 1300 ° C.
D The temperature is raised to a high temperature higher than the treatment temperature and lower than the melting point of the SiC-based substrate, and the temperature is maintained at the high temperature for a predetermined time, and then the temperature is lowered to the CVD temperature and maintained for a predetermined time.
A method for manufacturing a silicon carbide film-covered member, which comprises subjecting a VD source gas to circulation to perform a CVD process. 3. The high temperature is at least 1.05 times higher than the CVD processing temperature, and 1400.
The method for producing a silicon carbide film-coated member according to claim 2, wherein the temperature is not higher than 0 ° C. 4. The predetermined time for holding at the high temperature is 0.5
The method for manufacturing a silicon carbide film-coated member according to claim 2 or 3, wherein the method is for 2.0 hours. 5. The method for manufacturing a silicon carbide film-covered member according to claim 2, 3 or 4, wherein the SiC base material is made of reaction-sintered SiC.