JPH0653139A - Susceptor - Google Patents

Abstract

PURPOSE:To improve uniformity of film thickness by making gas loading effect of a susceptor part and a wafer part uniform in a CVD device wherein a wafer is mounted on a susceptor and the wafer is indirectly heated to form a film. CONSTITUTION:A susceptor structure is provided which has a susceptor cover 6 which is applied to a surface of a susceptor 2 to enclose a wafer 1 of a film formation object with a material having the same surface roughness and thermal conductivity as the wafer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a susceptor, and more particularly to a susceptor for an epitaxial growth apparatus and a vapor phase growth apparatus (CVD) in a semiconductor device manufacturing apparatus.

[0002]

2. Description of the Related Art A conventional susceptor is used for mounting a wafer on an epitaxial growth apparatus and a CVD apparatus, heating the susceptor by high-frequency induction heating of a work coil, and controlling the wafer to a desired process temperature by the heat. . Further, in the susceptor, high-purity carbon having an isotropic structure is coated with high-purity silicon carbide having a β structure (hereinafter referred to as SiC) by CVD for several tens of μm.

Conventionally, when performing CVD or the like using this susceptor, a pancake type flat surface having a surface roughness (Ra) as shown in the sectional view of FIG. The wafer 1 is placed as it is on the susceptor 2 having a size of about 20 μm as shown in FIG. 5, or when the wafer 1 to be heated is always a fixed shape as shown in the sectional view of FIG. Surface roughness (Ra) of SiC coating is 2μm
The process temperature is controlled and the gas flow rate and pressure are set to the prescribed values by using a susceptor with a spot facing shape that is moderately smooth and takes into account the thermal characteristics of the wafer generated in the wafer diffusion process. Let the membrane.

[0004]

This prior art FIG. 5 (a)
The susceptor of the type can deal with an irregularly shaped wafer, but since it has a structure that prevents the wafer from being displaced due to the static friction between the susceptor and the wafer, a surface roughness as shown in FIG. Will be needed. Further, in the susceptor of the type shown in FIG. 5C, since the surface roughness of the susceptor is small, the contact area between the wafer and the susceptor is large, and the thermal uniformity within the wafer surface is high. However, since the ratio of the surface area per unit area between the wafer surface and the susceptor surface is large, a process gas loading effect occurs, and the process gas is consumed more on the susceptor side. There was a problem that the thickness became thin on the side and the uniformity was poor.

[0005]

The susceptor of the present invention is made of isotropic graphite of high density and high purity as a base material and has β-structure SiC.
(Bulk density ≈ 3.25 g / cm ³ , hardness: 2800-3
500knoop, thermal expansion coefficient: 4.5 × 10 ⁻⁶ / ° C.,
Resistivity: 1 to 10 Ω · cm) 120 μm by CVD method
A susceptor cover having the same material and thickness as the wafer is provided on the entire front surface except for mounting the wafer on the susceptor having a surface roughness Ra of approximately 2 μm.

[0006]

The present invention will be described below with reference to the drawings. FIG. 1A is a sectional view of a susceptor according to a first embodiment of the present invention. After setting the susceptor 2 in the CVD apparatus as shown in the sectional view of FIG. 2, at least 20 mm on the susceptor 2 surrounding the wafer 1 to be grown by CVD has the same surface area per unit area as the wafer 1 and has the same thermal conductivity. Cover with susceptor cover 10. In this embodiment, the layer resistance is 30Ω
Using the above silicon, the wafer 1 and the susceptor cover 10
The clearance between and is 0.5 mm or less.

Then, the susceptor 2 is heated by high-frequency induction heating of the work coil 3, the process temperature is controlled to 750 ° C., N ₂ is used as a process gas of 40 SLM, SiH ₄
Flow from the 200SCCM gas nozzle 5, pressure 500m
The film thickness on the wafer surface when the polysilicon film is formed by decompressing the inside of the bell jar 6 with mH ₂ O is shown in the graph of FIG. 3 and compared with the conventional susceptor not using the susceptor cover. From the figure, it can be seen that the uniformity of the film thickness on the wafer edge side is improved. The measurement result of the surface roughness (Ra) of the susceptor used in this example is shown in FIG. R
A susceptor having a of about 2 μm is used.

Next, a second embodiment of the present invention has a structure in which a divided susceptor cover 10 is attached to each surface of the barrel type susceptor 2 as shown in the perspective view of FIG. This embodiment can also be applied to a vertical CVD apparatus.

[0009]

As described above, according to the present invention, the susceptor surface is covered with the silicon susceptor cover so as to surround the wafer placed on the susceptor, and the outer peripheral portion of the wafer is set to the same condition as the wafer. The adsorption probability, which has an important effect on the surface reaction, that is, the loading effect of the process gas becomes uniform, the surface coverage of the susceptor is improved, and the film thickness uniformity of the wafer is improved.

[Brief description of drawings]

1A and 1B are views showing a first embodiment of the present invention, in which FIG. 1A is a sectional view and FIG. 1B is a surface roughness diagram.

FIG. 2 is a cross-sectional view of a CVD apparatus using the first embodiment.

FIG. 3 is a diagram comparing the film thicknesses formed using Example 1 and a conventional example.

FIG. 4 is a perspective view of a second embodiment.

5A and 5B are views showing a conventional susceptor, in which FIG. 5A is a sectional view, FIG. 5B is a surface roughness diagram, and FIG. 5C is another sectional view.

[Explanation of symbols]

 1 wafer 2 susceptor 3 work coil 4 gas nozzle 5 bell jar 6 susceptor cover

Claims (1)

[Claims] 1. A susceptor having the same surface roughness and thermoconductivity as a wafer on a SiC-coated carbon susceptor for mounting a wafer and heating it by high frequency induction heating to indirectly heat the wafer to a process temperature. A susceptor comprising a cover around the mounting surface of the wafer.