JPH0268922A - Susceptor for vapor growth - Google Patents

Abstract

PURPOSE:To reduce development of slip of crystal defect through uniformed temperature distribution inside a wafer surface by making a specular surface of a recessed section wherewith a semiconductor substrate is brought into contact and by improving adhesion of the wafer and the spherical recessed section. CONSTITUTION:In a vapor growth susceptor 1 having a recessed section 2 for mounting a semiconductor substrate, a surface of the recessed section 2 wherewith the semiconductor substrate is brought into contact is made specular. For example, SiC1A is applied to an entire surface of a carbon core material of the vapor growth susceptor 1 having the spherical recessed section 2 to mount a wafer so that turbulence of atmosphere due to impurity is not caused during vapor growth reaction. The surface of the spherical recessed section 2 of the susceptor 1 is polished specular. According to this constitution, when the wafer is set to the spherical recessed section 2 at a room temperature and heated to a reaction temperature, the wafer comes to close contact with a surface of the spherical recessed section 2, thus making a temperature distribution inside the wafer uniform like inside a surface of the susceptor 1.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vapor phase growth apparatus for vapor phase growth of a semiconductor material on a semiconductor substrate such as silicon, particularly a vapor phase growth apparatus that holds a semiconductor substrate and is heated by high frequency. The present invention relates to a susceptor for use.

[Conventional technology]

In the crystal growth method using vapor-phase chemical reactions used in the manufacture of semiconductors, a susceptor on which a number of semiconductor substrates (hereinafter referred to as wafers) are stacked is installed in a reaction furnace, and crystals are grown on the wafers while flowing a reaction gas. Growth takes place. Figure 4(a),
(b) shows the structure of a conventional susceptor.As shown in Fig. 0, a susceptor l made of a disc-shaped carbon core material has recesses 2,2,2... on which the wafer is placed. Its surface is coated with silicon carbide (hereinafter referred to as SiC) IA.

The diameter of this recess 2 is selected to be slightly larger than the diameter of the wafer, and its depth 4 is approximately equal to the thickness of the wafer. This susceptor 1 has a function as a wafer support when heating is performed for crystal growth by a gas phase chemical reaction.

When the susceptor 1 is heated using high-frequency induction heating, it is heated from the inside of the susceptor 1 (carbon core material), so heat is released to the outside by thermal conduction.
The outer peripheral part of the wafer placed on the susceptor 1 is less likely to be heated than the central part, and the wafer is likely to warp due to thermal stress caused by the temperature difference. It is machined to a depth of several tens of meters in the shape of a concave spherical radius (hereinafter referred to as a concave spherical surface).

[Problem to be solved by the invention]

By the way, if the shape of this concave spherical surface is machined, it will have a satisfactory value in terms of accuracy, but during the vapor phase growth chemical reaction of 5iCIA, the surface roughness of the spherical concave portion 2 is 20 to 50 μm, and abnormal growth occurs. , flatten to a uniform flat surface, Figure 5(a)
As shown in (b), the protrusions 2A bridge 5 in the spherical recess 2, and the wafer 6 placed in the recess 2 does not come into close contact with the bottom surface of the spherical recess 2 of the susceptor 1. The temperature distribution becomes non-uniform, and the effect of machining the two concave portions 2 into spherical surfaces does not appear, and this is also a factor in the occurrence of slippage of crystal defects. Note that FIG. 5fa) shows the state at room temperature, and FIG. 5(b) shows the state during reaction. In addition, there are concavities, convexities, and undulations on the surface of the SiC layer after the spherical concave processing, and when the diameter of the wafer is increased or the thickness of the wafer is increased, the warpage becomes smaller due to thermal stress at a constant temperature.

Therefore, the accuracy during machining of the spherical surface and the growth of the SiC coat layer is difficult, which lowers the manufacturing yield of the susceptor and causes slippage of crystal defects.

An object of the present invention is to provide a susceptor for vapor phase growth that solves the above problems.

[Differences between the invention and the prior art]

In contrast to the conventional susceptor described above, the present invention has a protrusion that has abnormally grown on the surface of the spherical recess on which the wafer is placed.

The difference is that it is polished to remove undulations.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a susceptor for vapor phase growth having a recess for placing a semiconductor substrate, in which the surface of the recess with which the semiconductor substrate is brought into contact is mirror-finished.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1(a) is a plan view showing an embodiment of the present invention, FIG. 1(b) is a partially enlarged view taken along line A-A in FIG. 1(a), and FIG.
a) to (C) are enlarged cross-sectional views showing the state before and after polishing of the surface of the spherical concave portion on which the wafer is placed on the susceptor for vapor phase growth of the present invention, and FIGS. 3(a) and (b) are FIG. 3 is an enlarged cross-sectional view showing the state in which a wafer is placed in the spherical recess of the present invention at room temperature and at reaction temperature.

As shown in FIGS. 1(a) and 1(b), the entire surface of the carbon core material was coated with 5iCIA using a susceptor J for vapor phase growth having a slanted spherical recess 2 in which the wafer was placed. Although this was done to prevent impurities from leaking out during the phase growth reaction, when the 5iCIA coating was subjected to a gas phase chemical reaction, abnormal growth such as protrusions 2A and undulations occurred on the bottom of the spherical surface as shown in Figure 2 (b). do.

Therefore, in the present invention, the surface of the spherical concave portion 2 of the susceptor 1 with which the wafer 3 comes into contact is subjected to polishing treatment 2A to make the surface a mirror surface.

According to the present invention, the wafer 3 is set in the spherical concave portion 2 at room temperature as shown in FIG. 3(a), and heated.
When the temperature is raised to the reaction temperature as shown in b), the surface of the spherical recess 2 becomes a mirror surface and no protrusions or undulations occur on the surface, and the wafer 3 comes into close contact with the surface of the spherical recess 2. The temperature distribution within the wafer 3 can be made uniform in the same way as within the surface of the susceptor 1.

〔Effect of the invention〕

As explained above, in the present invention, by polishing the bottom surface of the spherical recess on which the wafer is placed, the wafer is brought into close contact with the spherical recess, and a uniform temperature distribution can be achieved.

Conventionally, when the wafer thickness is increased by increasing the diameter of the wafer (5φ to 6φ), the high-frequency induction heating method starts heating from inside the susceptor and heats the wafer by heat conduction. The thicker the wafer is, the less warping occurs, making it difficult to control the depth of the spherical recess. However, according to the present invention, by polishing the bottom surface of the spherical recess, reproducibility can be improved. The improved adhesion between the wafer and the spherical concave portion has the effect of making the in-plane temperature distribution of the wafer uniform, thereby minimizing the slip occurrence rate of crystal defects.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view showing one embodiment of the present invention, FIG. 1(b) is an enlarged sectional view taken along the line A-A in FIG. 1(a), and FIG.
a) to (C) are enlarged cross-sectional views taken along line A-A in FIG. 1(a);
FIGS. 3(a) and 3(b) are partial cross-sectional views of the wafer placed on the stage for vapor phase growth of the present invention at room temperature and at reaction temperature, and FIG. A plan view showing a susceptor for growth, FIG. 4(b) is an enlarged sectional view taken along the line B-B in FIG. 4(a), and FIGS. FIG. 3 is a partial cross-sectional view of a state in which a sample is placed at room temperature and at a reaction temperature. 1...Susceptor IA...SiC2...
Spherical concave portion 3...Wafer patent applicant NEC Corporation (b) Figure (a) Figure (a) (d) (b) (b) Figure Figure A (α) Figure ((1' ) ('b) Figure

Claims (1)

[Claims] (1) A susceptor for vapor phase growth having a recess for placing a semiconductor substrate, characterized in that the surface of the recess with which the semiconductor substrate comes into contact is mirror-finished.