JPS58170012A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the accurring of trouble in a post-process, and to obviate the formation of an undesired impurity layer, by forming a buried diffusion region of the solid phase using glass containing an impurity. CONSTITUTION:An antimony-glass film 12 is formed onto a silicon semiconductor substrate 11. A silicon dioxide film 13 is grown. The silicon dioxide film 13 is patterned, and windows are formed to a position where the buried diffusion region need not be formed and a position where a positioning mark is formed previously. The same windows are formed through the etching of the film 12 through the windows, and the surface of the substrate 11 is exposed. A mask film 14 consisting of a photo-resist is formed, a window is formed at the position where the positioning mark is formed previously through the patterning of the film 14, and the surface of the substrate 11 is exposed to the window again. The mask film 14 and the silicon dioxide film 13 are removed, and a cover film 15 of silicon dioxide is formed through a chemical vapor deposition method. Antimony is diffused into the substrate 11 from the antimony-glass films 12 through heat treatment, and the n<+> type buried diffusion regions 16 are formed.

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to improvements in methods of manufacturing semiconductor devices having buried diffusion regions.

Prior art and problems As one of the techniques for forming a buried diffusion region, one based on in-phase diffusion is known. That is, as shown in FIG. 1, for example, an antimony glass (Sb glass) film 2 is formed on a portion of a silicon semiconductor substrate 1 where a buried diffusion region is to be formed, and then a heat treatment is performed to diffuse antimony into the substrate 1. death,? This forms a mold buried diffusion region 5.

However, when the above technique is adopted, antimony is diffused out from the antimony glass film 2 as an impurity source as shown by the arrow in the figure, and a hollow-shaped impurity diffusion layer is formed on the surface of the substrate 10. It will be formed. Needless to say, if that part becomes conductive, isolation between elements will be hindered.

Therefore, the next method that can be considered is the one shown in Figure 2. That is, a cover film 4 made of silicon nitride, for example, is formed on the antimony glass film 2, and then thermal oxidation is performed to form a silicon dioxide film 5, while antimony is diffused from the antimony glass film 2. This forms a mold buried diffusion region 3.

According to this technique, the outer mold impurity diffusion layer described in connection with FIG. 1 is not formed, but the substrate 1 after removing the antimony glass film 2, the cover film 4, and the silicon dioxide film 5 can be seen in FIG. It has five steps like this. conventionally,
This step 5 is used as a positioning mark. However, it is originally desirable for the subsequent steps that such a step hB does not exist.

Purpose of the Invention The present invention aims to prevent the formation of an undesired impurity diffusion layer or step on the surface of a semiconductor substrate even when a buried diffusion region is formed by solid-phase diffusion, and also to form alignment marks with a textured shape. The purpose is to ensure that

Embodiment of the Invention FIGS. 4 to 6 are cross-sectional views of main parts of a semiconductor device at key points in the process for explaining embodiments of the present invention.
This will be explained with reference to these figures.

(See Figure 4) (1) Antimony glass is coated on the silicon semiconductor substrate 11 to make the antimony glass film 12 thick)
For example, it is formed to about 2000 (,;:).

(2) Silicon dioxide film 1 as an example of chemical vapor deposition method
5 is grown to a thickness of, for example, about 2000 (j).

(3) The silicon dioxide film 15 is patterned using the photo ring 2-fi technique to form windows in areas where buried diffusion region formation is unnecessary and in areas where alignment marks are to be formed.

(4) Etching the antimony glass film 12 through the window to form a similar window and expose the surface of the substrate 11;

(5) A mask film 14 made of photoresist is formed, and this is patterned to form a window in a portion where an alignment mark is to be formed, and the surface of the substrate 11 is again raised there. However, the pattern on the cover film 15 at this time does not need to be very precise.

161 Etching the substrate 11 to form alignment marks 11 and 4.

See FIG. 5 (7) Remove the photoresist mask film 14 and silicon dioxide film 13.

(8) Cover film 1 of silicon dioxide by chemical vapor deposition method
5 is formed to have a thickness of, for example, about 2000 (A).

See Figure 6 (9) Temperature 1200 (C, l, time 40 (minutes)
A heat treatment is performed to diffuse antimony from the antimony glass film 12 into the substrate 11 to form a buried diffusion region 16.

However, since the silicon dioxide film 15 in the above embodiment is a mask for patterning the antimony glass film 12, it may be replaced with another mask film, such as a nitride silicon film. The silicon dioxide cover film 15 may be a polycrystalline silicon film that is initially formed and then oxidized; in other words, it may be a film through which oxygen permeates during heat treatment.

Effects of the Invention As can be seen from the above explanation, according to the present invention, although the method of forming a solid-phase buried diffusion region using impurity-containing glass as a source is adopted, the surface is maintained flat. Since no inconvenience is caused in subsequent steps and no undesired impurity layer is formed, it is possible to manufacture a device with good characteristics.

Furthermore, since a clear alignment mark can be formed at the same time, there is no difficulty in alignment during subsequent steps, for example, when forming separation regions.

[Brief explanation of drawings]

1 to 3 are cross-sectional views of main parts of a semiconductor device at key process points for explaining the conventional technology, and FIGS. 4 to 6 are key process steps for explaining an embodiment of the present invention. 1 is a sectional view of a main part of a semiconductor device in FIG. In the figure, 11 is a silicon semiconductor substrate, 12 is an antimony glass film, 13 is a silicon dioxide film, 14 is a mask film, 15 is a cut-off film, and 16 is a ゜-shaped buried diffusion region. Patent applicant: Fujitsu Co., Ltd.

Claims (1)

[Claims] An impurity source glass film is selectively formed on the semiconductor substrate, and then the semiconductor substrate is selectively etched to form alignment marks consisting of recesses, and then a cover film is applied over the entire surface using chemical vapor. 1. A method of manufacturing a semiconductor device, comprising the step of performing heat treatment after phase growth to diffuse impurities from the impurity source glass film into the semiconductor substrate to form a buried diffusion region.