JPH11199323A - Dummy wafer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be used in a process for cleaning the inside of a chamber for plasma etching and the like and a process for heat-treating a product wafer in a diffusion furnace, a vertical furnace, etc., and has a small warpage and excellent corrosion resistance.
A dummy wafer made of a VD-SiC molded body is provided. SOLUTION: This is a SiC molded body obtained by applying a SiC coating on a substrate surface by a CVD method and then removing the substrate, wherein the half-width 2θ of the SiC (111) surface obtained by X-ray diffraction is 0. .18 to 0.32 ° and SiC (11
The intensity ratio of the diffraction peak of the crystal plane to the 1) plane is as follows: I (200) / (111) = 0 to 0.4, I (220) / (11)
1) = 0-1.0, I (222) / (111) = 0-0.0
8. A dummy wafer comprising a CVD-SiC molded body having a crystal property of I (311) / (111) = 0 to 0.8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dummy wafer used in a process for cleaning the inside of a plasma etching chamber in a semiconductor manufacturing process such as an IC or an LSI, or an end position where product wafers are lined up in a diffusion furnace or a vertical furnace. And a dummy wafer used for stabilizing the processing properties of a product wafer.

[0002]

2. Description of the Related Art In a plasma etching process, high-frequency power is applied between electrodes while introducing a reactive gas (a gas containing atoms such as C, H, F, and O) into an etching apparatus provided with a pair of parallel plane electrodes. This is a process step of forming a fine circuit pattern with high precision by etching a portion that is not photoresisted using generated gas plasma.

[0003] This plasma etching process needs to be performed under uniform plasma conditions, but it is difficult to maintain uniform reaction conditions. For example, when etching is performed by a low-pressure CVD method using a vertical furnace, a furnace is used. In the upper part and the lower part, the flow of the reactive gas, the temperature distribution, and the like tend to be non-uniform. Therefore, a method has been adopted in which dummy wafers are set at the upper and lower portions of a furnace in which the wafers are set, and the etching conditions for the wafers are stabilized.

[0004] Further, if the plasma etching process is repeatedly performed, there arises a problem that the etched silicon adheres to an electrode or a wafer holder in the chamber or particles are generated due to the detachment of the adhered silicon. Therefore, it is necessary to periodically set a dummy wafer instead of a wafer and perform plasma etching processing to clean the inside of the system.

[0005] Accordingly, the dummy wafer is required to have a material property that is hardly etched, that is, excellent heat resistance and corrosion resistance, and high purity that does not cause impurity contamination. As the material of the dummy wafer, silicon, quartz, graphite, and the like have been studied. However, quartz cannot be used because it has no conductivity, and graphite has a problem that particles fall off from tissue due to its material. Further, when a silicon wafer is used as a dummy wafer, there is a problem that corrosion resistance to acid cleaning is not sufficient. For this reason, SiC which is hardly eroded by hydrochloric acid gas used for cleaning the dummy wafer is regarded as a promising material for the dummy wafer.

SiC has heat resistance, high temperature strength, thermal shock resistance,
It is excellent in material properties such as abrasion resistance and corrosion resistance, and is useful as a member for semiconductor manufacturing and various industrial members. As a method of manufacturing a SiC compact, there has been a method of sintering SiC powder for a long time. However, SiC is a hardly sinterable material and requires a sintering aid to obtain a compact compact body with a smooth surface. It is difficult to obtain a pure product. for that reason,
The SiC molded body manufactured by the sintering method has a drawback that it is not suitable for use in a semiconductor field particularly requiring high purity.

On the other hand, a method for producing a SiC molded body using a CVD method (chemical vapor deposition method) is based on a method in which a carbon-containing organic silicon compound such as trichloromethylsilane and hydrogen, or an organic silicon compound such as silicon tetrachloride and methane are mixed. Gas-phase reaction using a mixed gas such as hydrocarbons and hydrogen as a raw material gas to deposit a SiC product on the surface of the base material to form a film, and then remove the base material. Purity S
An iC molded body can be obtained. The removal of the substrate is performed by cutting, polishing, or the like. However, when a carbon material is used as the substrate, there is an advantage that the process can be simplified since it can be easily burned and removed by heat treatment in air.

However, when SiC is vapor-phase deposited by a CVD method using a carbon material, for example, a graphite material having a flat surface and a flat surface, a difference in the coefficient of thermal expansion between the graphite substrate and the SiC film and the SiC film. Due to the change in the crystal structure due to the difference in the vapor deposition rate of the SiC film, there is a problem in that the SiC film molded body obtained by removing the graphite base material is warped. That is, when the coefficient of thermal expansion of the graphite base material is larger than the coefficient of thermal expansion of SiC, compressive stress is applied to the SiC film, and the surface of the SiC film warps to a convex shape. Conversely, when the coefficient of thermal expansion of the graphite base material is small, a tensile stress acts on the SiC film, so that the surface of the SiC film warps into a concave shape.

The formation of the SiC film deposited by the CVD method involves forming nuclei of SiC first on the substrate, then growing it into amorphous or fine-grained polycrystals, and further growing into a columnar crystal structure. The process of depositing and depositing the SiC film is followed. In this case, since the thermal expansion coefficient of the amorphous or fine-grained polycrystalline SiC film in contact with the base material is smaller than the thermal expansion coefficient of the columnar crystal structure, the graphite material as the base material is heated in air. In the case of combustion removal, a compressive stress acts on an amorphous or fine-grained polycrystalline portion, and a tensile stress acts on a columnar crystal structure portion, so that a concave shape as a whole is warped.

Therefore, as a method of manufacturing a SiC molded body by a CVD method, a SiC film is formed on a surface of a base by a CVD method, and an SiC film is further formed on both surfaces of a SiC substrate obtained by removing the base. A method for producing a SiC molded body by a CVD method (Japanese Patent Laid-Open No. Hei 8-188408), or a method of forming a SiC film on a surface of a substrate by a CVD method and removing the substrate to form a SiC molded body. In the manufacturing method, a step of forming a SiC layer by a CVD method and then flattening the surface of the SiC layer is repeated a plurality of times, so that each layer has a thickness of 100 μm or less.
There has been proposed a method of manufacturing a SiC molded body by a CVD method, which comprises removing the substrate after laminating the iC layer to a desired thickness or more (Japanese Patent Application Laid-Open No. 8-188468).

The inventions of the above-mentioned Japanese Patent Application Laid-Open Nos. 8-188408 and 8-188468 are intended to suppress the occurrence of cracks and warpage in a SiC molded body without forming a SiC film to a desired thickness at one time. Stopping in the middle, minimizing the internal stress accumulated in the SiC film, the crystal grains are uniform in size, and the surface of the film is reduced in the degree of irregularities.
The step of forming a film or stopping the formation of the SiC layer at an initial stage and flattening the layer surface is repeated a plurality of times. That is, JP-A-8-188408 and 8-
According to the manufacturing method disclosed in Japanese Patent No. 188468, the SiC film formed by the CVD method is stopped in the middle without being formed all at once to a desired film thickness, and a process such as a planarization process is required. There is a problem that decreases.

[0012]

The present inventor has conducted research on the crystal properties of the SiC film in order to solve the above-mentioned problems. As a result, the crystallinity of the SiC crystal forming the SiC film is high, and If it is large or SiC (11
1) When the degree of orientation to the crystal plane is high, C
It has been found that the warpage generated in the VD-SiC molded body can be reduced and the corrosion resistance is improved.

The present invention has been developed on the basis of this finding, and its purpose is to clean a chamber of a heat treatment furnace for plasma etching, or to heat-treat a product wafer in a diffusion furnace or a vertical furnace. An object of the present invention is to provide a dummy wafer formed of a CVD-SiC molded body having a small warpage and excellent corrosion resistance.

[0014]

In order to achieve the above object, a dummy wafer of the present invention is provided on a substrate surface by CVD.
SiC obtained by removing the substrate after applying the iC coating
It is a molded product and is made of SiC (11
1) The half width 2θ of the surface is 0.18 to 0.32 ° and S
The intensity ratio of the diffraction peak of the crystal plane to the iC (111) plane is: I (200) / (111) = 0 to 0.4, I (220) / (11)
1) = 0-1.0, I (222) / (111) = 0-0.0
8, I (311) / (111) = 0 to 0.8, characterized in that it is composed of a CVD-SiC compact having the following crystal properties.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION For a substrate on which a SiC film is deposited by vapor deposition of SiC by a CVD method, a carbon material, particularly a graphite material, which can be easily removed by heat treatment in air, is preferably used. It is preferable to use a graphite material having a smooth surface and high flatness. The SiC film formed by vapor-phase deposition on the surface of the graphite base material by the CVD method can obtain a CVD-SiC molded body by removing the graphite base material. The graphite substrate can be removed by a suitable method such as a method of cutting and removing a graphite material, a method of polishing and removing by a shot blast or the like, or a method of burning and removing by heating in air. Is preferred because the operation is simple.

The present invention relates to a CVD for forming a dummy wafer.
As the SiC crystal plane of the SiC molded body, the value of the half width 2θ of the SiC (111) plane obtained by X-ray diffraction was 0.1
The angle is set in the range of 8 to 0.32 °. SiC
The value of the half value width 2θ of the (111) plane is related to the size and number of crystallites oriented to the (111) plane, and in the present invention,
By setting the value of the half-width 2θ of the iC (111) plane to a specific range, the crystallinity can be changed to a crystal state in which many large crystallites exist, that is, crystal defects and crystal irregularities existing in the SiC crystal can be corrected. It is intended to improve the quality.

That is, the half width 2 of the SiC (111) plane
When the value of θ is large and the value fluctuates greatly,
Since the crystallinity of SiC is low, warpage due to a change in the crystal structure is likely to occur. Accordingly, the present invention sets the half-width 2θ of the SiC (111) plane obtained by X-ray diffraction to a small value within a narrow range to control the CVD-S
This is to suppress the warpage generated in the iC molded body to a small value.

Furthermore, in the present invention, SiC (111)
It is characterized by high orientation to the crystal plane and small orientation to other crystal lattice planes. Specifically, the intensity ratio of the diffraction peak of the other crystal plane to the SiC (111) plane is I (200) / (1
11) = 0-0.4, I (220) / (111) = 0-1.0,
I (222) / (111) = 0 to 0.08, I (311) / (11
1) Set to a value of = 0 to 0.8. Thus, CV
The crystal growth directions of SiC by the D method are uniform, and SiC (11
1) A dummy wafer composed of a CVD-SiC molded body having a high orientation to a plane has a very small change in crystal structure caused by a heat treatment process, so that it is possible to provide a dummy wafer with little warpage and excellent corrosion resistance. Become.

In the X-ray diffraction, an applied voltage: 40 KV, an applied current: 20 mA, a scanning speed: 4 ° / min., A divergence slit: 1 °, an entrance slit;
1 °, scattering slit; 0.3 mm, filter: Ni, and the half value width of the SiC (111) plane and the intensity ratio of the diffraction peak are determined from the diffraction peak value.

The CVD forming the dummy wafer of the present invention
The SiC molded body is formed on a substrate surface such as graphite by CVD method.
It is obtained by removing the base material after depositing the SiC film by depositing C in the vapor phase. For the SiC coating by the CVD method, a graphite base is set in a CVD reactor, and hydrogen gas is used as a carrier gas, and a carbon-containing organic material such as trichloromethylsilane, trichlorophenylsilane, dichloromethylsilane, dichlorodimethylsilane, chlorotrimethylsilane, etc. A SiC film is deposited by performing a thermal decomposition reaction using a silicon compound or an organic silicon compound such as silicon tetrachloride and a hydrocarbon such as methane as raw material gases. In this case, the crystallinity of the deposited SiC film is controlled by setting the thermal decomposition reaction temperature, the raw material gas concentration, the raw material gas supply amount, and the like to appropriate values. For example, the thermal decomposition reaction temperature is 120
0-1600 ° C, raw gas concentration 5-20 Vol%,
The pressure inside the reactor is set to 760 Torr or more.

The thus formed CVD-SiC compact is preferably heat-treated again in order to improve the crystal structure and enhance the crystallinity and to correct the warpage. The heat treatment is performed by appropriately maintaining the temperature at a predetermined temperature in an inert atmosphere. The heat treatment temperature must be lower than the recrystallization temperature of SiC and lower than the temperature at which crystal transformation or decomposition reaction occurs. On the other hand, if the heat treatment temperature is low, the effect of correcting the crystal structure is not sufficient, so the temperature is preferably set to 1400 to 1800 ° C.

As described above, the present invention comprises a CVD-SiC compact having a crystal structure having a high orientation to the SiC (111) plane and an extremely small orientation to other crystal lattice planes. Crystal defects, crystal irregularities, and the like are corrected, high crystallization is achieved, and a dummy wafer with less warpage and excellent corrosion resistance can be provided.

[0023]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples.

Example 1 An isotropic graphite material having a bulk density of 1.85 g / cm ³ , a coefficient of thermal expansion of 4.5 × 10 ^-6 , and an ash content of 10 ppm was processed to a diameter of 202 mm and a thickness of 5 mm to prepare a base material. Produced. This graphite substrate was set in a CVD reactor, and trichloromethylsilane (C
H ₃ SiCl ₃ ), hydrogen gas as a carrier gas, CV under the conditions of a source gas concentration of 10 Vol% and a reaction temperature of 1400 ° C.
A 1.2 mm thick SiC coating was deposited by performing a D reaction.
Next, after heating in air to burn off the graphite substrate, the surface was polished by shot blasting and a diamond wheel to obtain a 0.5 mm thick CVD-SiC molded body.

Examples 2-5, Comparative Examples 1-4 A CVD-SiC compact was produced in the same manner as in Example 1 except that the CVD reaction temperature and the raw material gas concentration were changed.

Examples 6 to 8 The CVD-SiC compacts produced in Example 1 were heat-treated at different temperatures in an argon gas atmosphere.

Table 1 shows the manufacturing conditions of the obtained CVD-SiC compact.

[0028]

[Table 1]

The thus formed CVD-SiC compact was subjected to X-ray diffraction under the following conditions, and the half-width of the SiC (111) plane and the SiC (11
1) The intensity ratio of the diffraction peak to the plane was determined. Note that X
Line diffraction was measured by Kα of Cu. X-ray diffraction conditions; applied voltage: 40 KV, applied current: 20 mA, scanning speed: 4 °
/ Min., Divergence slit; 1 °, entrance slit; 1 °, scattering slit; 0.3 mm, filter; Ni,

Next, the amount of warpage was measured by a three-dimensional shape measuring machine. The amount of warpage was determined by measuring the height of the CVD-SiC molded body that had been allowed to stand, and using the maximum value of the height difference as the amount of warpage (mm). Further, the corrosion resistance was tested by measuring the weight loss rate when left in a hydrogen chloride gas at a temperature of 1200 ° C. for 100 hours. The results thus obtained are shown in Table 2 together with the crystal properties.

[0031]

[Table 2]

From the results shown in Table 2, it can be seen that the CVD-SiC molded body of the example having the requirements of the present invention has less warpage and excellent corrosion resistance to hydrogen chloride gas at high temperatures as compared with the comparative example. Is recognized.

[0033]

As described above, in the dummy wafer of the present invention, the half width 2θ of the SiC (111) plane is in the specific range, and the crystal planes (200), (220), (222), and (311) planes of
Since it is constituted by a CVD-SiC compact having a crystal property with a small intensity ratio of the diffraction peak to the (111) plane, a change in the crystal structure caused during the heat treatment process can be extremely reduced, and as a result, the warpage is reduced. Thus, it is possible to provide a dummy wafer which is small and has excellent corrosion resistance.

Claims (1)

[Claims] 1. A SiC molded body obtained by applying a SiC coating on a substrate surface by a CVD method and then removing the substrate, wherein the half-value width 2θ of the SiC (111) surface obtained by X-ray diffraction is 0.18 to 0.32 ° and SiC (11
The intensity ratio of the diffraction peak of the crystal plane to the 1) plane is as follows: I (200) / (111) = 0 to 0.4, I (220) / (11)
1) = 0-1.0, I (222) / (111) = 0-0.0
8. A dummy wafer comprising a CVD-SiC molded body having a crystal property of I (311) / (111) = 0 to 0.8.