JPH04188720A - Etching of vapor growth susceptor - Google Patents

Abstract

PURPOSE:To provide a stabilized quality epitaxial layer by placing a thin plate on a wafer pocket part of a susceptor upon removal of a polysilicon film using hydrochloric acid. CONSTITUTION:A silicon wafer 1 is placed in a wafer pocket part 3 of a susceptor 2 to grow an epitaxial layer 4. In this case, a polysilicon film 5 is grown on the susceptor 2. With the epitaxial growth repeated several times, the polysilicon film 5 is superimposed into a thick one. Then, the unnecessary polysilicon film 5 is etched and removed with high concentration hydrochloric acid gas. Thereupon, an SiC thin plate 6 of the same shape as the silicon wafer is placed in the wafer pocket part. Accordingly, the wafer pocket part 3 is protected by the thin plate 6 and does not make direct contact with the hydrochloric acid gas and hence is not etched. Thus, the wafer pocket part 3 keeps its original shape as designed to ensure a stabilized quality epitaxial layer with satisfactory reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for etching a susceptor used for epitaxial growth of semiconductor wafers.

BACKGROUND OF THE INVENTION Epitaxial growth techniques are widely used in the manufacture of semiconductor devices. Susceptors for epitaxial growth are generally made of graphite coated with a 5iC (silicon kerf s+ite) film, and are also made of semiconductor wafers,
For example, the processed wafer 1 is placed in a recessed counterbore called a wafer pocket. When epitaxial growth is performed, an epitaxial layer grows on the silicon wafer, while a polysilicon film grows on the susceptor. If epitaxial growth is performed multiple times, the polysilicon film will accumulate and become thicker, causing adverse effects such as particles and crystal defects on the epitaxial layer. and remove it. FIG. 2 shows a cross section during conventional susceptor etching. 2 is a susceptor, 3 is a wafer pocket, and 5 is a polysilicon film grown on the susceptor.

Problems to be Solved by the Invention However, in the above-mentioned conventional method, the wafer pocket 3 without the polysilicon film is directly exposed to the highly concentrated carbonic acid gas, so that although it is coated with the S]C film, etching is not possible. As the process progresses, pinholes and the like occur as the shape changes, and during subsequent epitaxial growth, there are problems such as crystal defects in the silicon wafer due to thermal strain and resistivity variations due to contamination.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and aims to provide a method for etching a susceptor for vapor phase growth without changing the shape of a wafer pocket.

Means for Solving the Problems To achieve this object, the method of etching a susceptor for vapor phase growth of the present invention includes placing a thin plate in the wafer pocket of the susceptor when removing a polysilicon film with hydrochloric acid gas. .

The wafer pocket portion of the working susceptor does not come into direct contact with the hydrochloric acid gas and is not etched because the thin plate is inserted therein.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a method of etching a susceptor for vapor phase growth in one embodiment of the present invention. First, as shown in FIG. 1, a silicon wafer/%l is placed in the wafer pocket 3 of the susceptor 2 and an epitaxial layer 4 is grown. In this case, a polysilicon film 5 is grown on the susceptor 2. When this epitaxial growth is repeated several times, the polysilicon film 5 is stacked and becomes thicker, as shown in FIG. 1fbl. Next, this unnecessary polysilicon film 5 is removed by etching with highly concentrated hydrochloric acid and gas. At this time, a thin SiC plate 6 having the same shape as the silicon wafer is placed in the wafer pocket. Therefore, the wafer pocket portion 3 is protected by the thin plate 6 and does not come into direct contact with the hydrochloric acid gas and is not etched.

Therefore, the Ueno 1 pocket portion 3 maintains its designed shape and does not change, so that an epitaxial layer of stable quality can be obtained with good reproducibility. Furthermore, since the generation of pinholes is prevented, there is no fear of contamination, and the life of the susceptor itself is dramatically increased. The material of the thin plate 6 is preferably SiC, which is relatively resistant to hydrochloric acid gas, and since SiC itself is highly pure, there is no fear of contamination from SiC.

Although SiC is used as the thin plate in the embodiment, the effects of the present invention can be maintained even if a quartz plate or a high-purity silicon wafer dummy is used.

Further, in the embodiment, a susceptor having a wafer pocket has been described, but the present invention can also be applied to a flat plate type susceptor without a wafer pocket.

Effects of the Invention The method of etching a susceptor for vapor phase growth of the present invention prevents the wafer pocket from being etched by placing a thin plate on the wafer pocket of the susceptor when removing a polysilicon film with hydrochloric acid gas, thereby improving quality. Not only can a stable epitaxial layer be obtained, but also the excellent effect of increasing the life of the susceptor can be obtained.

[Brief explanation of the drawing]

FIG. 1 (al, (bl) is a sectional view of the etching method for a susceptor for vapor phase growth in an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional etching method for a susceptor for vapor phase growth. 1. ... Silicon wafer, 2 ... Susceptor, 3 ... Wafer pocket, 4 ... Epitaxial layer, 5 ... Polysilicon film, 6.
...Thin plate.

Claims (2)

[Claims] (1) A vapor phase characterized in that when a polysilicon film deposited on a susceptor by a predetermined number of epitaxial growths is removed using hydrochloric acid gas, a thin plate having the same shape as the semiconductor wafer is placed on the semiconductor wafer placement area. Etching method for growth susceptor. (2) A method for etching a susceptor for vapor phase growth according to claim 1, wherein the thin plate is made of SiC.