JPS61206240A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To contrive to improve the dielectric breaking strength by a method wherein the thinly formed recessed parts of the second oxide film on the side surfaces of the nitride film are filled with a polycrystalline Si film thinner than the first polycrystalline Si film, which is then oxidized to form a polycrystalline Si oxiden films, and moreover, through a thermal oxidation the polycrystallinen Si oxide film is formed into an interlayer insulating film. CONSTITUTION:An etching is performed on a first polycrystalline Si film 5 and a nitride film 4 using a photosensitive resin film 6 performed a patterning as a mask, and after that, a thermal oxidation is performed, whereby an interlayer insulating film 7 is formed and parts 9 and 9' are formed on the side surfaces of the nitride film 4. When a polycrystalline Si film 11 thinner than the first polycrystalline Si film 5 is deposited on the whole surface of a semiconductor substrate 1, parts of the polycrystalline Si film 11 are deposited on the recessed parts 9 and 9' and become overhang-shaped parts (b) and (b'). An oxidation is performed on the polycrystalline Si film 11 and polycrystalline Si oxide films 12 and 12' are formed on the whole surface. In this process, the interlayer insulating film 7 and the polycrystalline Si film 11 thinner than the first polycrystalline Si film 5 are oxidized and in case the polycrystalline Si oxide film 12 is seen as a whole, the polycrystalline Si oxide film 12 is eliminated parts to become thinner locally.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of manufacturing a semiconductor device such as a MOSLSI (MOS integrated circuit).

<Prior art> Conventionally, for example, silicon gate MOS dynamic memory LS as shown in FIGS. 2(a) to 2(g)
There is a method for producing I. First, as shown in FIG. 2(a), a field oxide film 2 is formed on a semiconductor substrate 1 by the Locos oxidation method, and then a first gate oxide film 3 and a nitride film 4 are formed, and then a first multilayer film 2 is formed. A crystalline silicon film 5 is formed, and a photosensitive resin 6 is left behind so that a desired pattern is formed using a conventional photolithography technique. Next, as shown in FIG. 2(b), using the patterned photosensitive resin 6 as a mask, the first polycrystalline silicon film 5. Nitride film 4
．． After sequentially etching the first gate oxide film 3, as shown in FIG. 2C, the semiconductor substrate 1 is thermally oxidized to form an interlayer insulation M7. After that, see Figure 2 (
As shown in d), a second polycrystalline silicon film 8 is deposited;
Finally, as shown in FIG. 2(e), the second polycrystalline silicon film 8 is patterned into a predetermined shape using a normal photolithography technique.

<Problems to be Solved by the Invention> However, in the above manufacturing method, the portion a shown in FIG. 2(f), that is, the portion a of the interlayer insulating film 7 formed on the side surface of the nitride film 4 is As a result, the first polycrystalline silicon film 5 and the second polycrystalline silicon film 8 are
) There is a problem in that there is a high possibility of electrical short-circuiting at part a.

Furthermore, when patterning the second polycrystalline silicon film 8 by anisotropic etching, the interlayer insulating film 7 is etched as shown in FIG. 2(g).
As shown in , since the part adjacent to the thinned part of the interlayer insulating film 7 has already formed an eaves shape, the second polycrystalline silicon film 8 remains in this part without being etched. There is a problem that the possibility of short-circuiting between the wiring lines 8 becomes high, and the expected yield cannot be obtained.

Therefore, an object of the present invention is to improve the breakdown voltage of the interlayer insulating film and the shape of the side surface of the first polycrystalline silicon film.
The expected yield can be obtained by preventing electrical short-circuiting between the first polycrystalline silicon film and the second polycrystalline silicon film, as well as preventing short-circuiting between the second polycrystalline silicon wirings. An object of the present invention is to provide a method for manufacturing a semiconductor device.

In order to achieve the above object, the method for manufacturing a semiconductor device of the present invention includes forming a two-layer insulating film by overlapping a first gate oxide film and a nitride film on a semiconductor substrate. , forming a first polycrystalline silicon film on the two-layer insulating film, patterning the first polycrystalline silicon film and the nitride film, forming a second oxide film by thermal oxidation; A polycrystalline silicon film thinner than the first polycrystalline silicon film is deposited over the entire surface of the semiconductor substrate covering the oxide film, and then the thin polycrystalline silicon film is oxidized to form a polycrystalline silicon oxide film. Next, the polycrystalline silicon oxide film is etched to form the first
The polycrystalline silicon oxide film is removed from the portion where the polycrystalline silicon film does not exist, and then an interlayer insulating film is formed by thermal oxidation, and then a second polycrystalline silicon film is deposited on the entire surface of the interlayer insulating film. The method is characterized in that the second polycrystalline silicon film is patterned into a predetermined shape.

<Example> Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments.

First, as shown in FIG. 1(a), a field oxide film 2 is formed on a semiconductor substrate I by the Locos oxidation method, and then a two-layer insulating film consisting of a first gate oxide film 3 and a nitride film 4 is formed. Then, a first polycrystalline silicon film 5 is further formed thereon. Then, the photosensitive resin 6 is left behind so that a desired pattern is formed using a normal photolithography technique.

Next, as shown in FIG. 1(b), using the patterned photosensitive resin 6 as a mask, the first polycrystalline silicon film 5 is
．． The nitride film 4 is etched. After that, Figure 1 (C)
As shown in FIG. 2, an interlayer insulating film 7 is formed by thermal oxidation. At this time, thinned portions 9, 9 of the interlayer insulating film 7 are formed on the side surfaces of the nitride film 4. Figure 1 (
As shown in d), a polycrystalline silicon film 11 thinner than the first polycrystalline silicon film 5 is deposited on the entire surface of the semiconductor substrate 1.
0-1000 people deposit. Then, the polycrystalline silicon film 11 is deposited on the thinned portions 9.9, that is, the recessed portions 9, 9, forming eaves-like portions.

It becomes bo. As shown in FIG. 1(e), the polycrystalline silicon film 11 is oxidized to form a polycrystalline silicon oxide film 12.12' over the entire surface. In this process, the interlayer insulating film 7
Then, the thin polycrystalline silicon film ti is oxidized, and when looking at the polycrystalline silicon oxide film 12 as a whole, there is no locally thinned portion a as in the conventional example shown in FIG.

Next, as shown in FIG. 1(f), by etching the polycrystalline silicon oxide film 12 over the entire surface of the polycrystalline silicon oxide film 12, the oxide film is etched in the areas where the first polycrystalline silicon film 5 does not exist. Remove 12°. Next, in Figure 1 (g
), an interlayer insulating film 7 is formed, and then, as shown in FIG. 1(h), a second polycrystalline silicon film 8 is deposited. Thereafter, the second polycrystalline silicon film 8 is patterned into a desired shape as shown in FIG.
A dynamic memory LSI is manufactured.

By going through this process, as shown in FIG. 2(d), the recessed part a of the oxide film on the side surface of the nitride film 4 is filled with a thin polycrystalline silicon film, and by oxidizing it, the conventional method It is possible to prevent the decrease in the thickness of the oxide film on the side surface of the nitride film, which is seen in the above, and to improve the dielectric breakdown strength of the interlayer insulating film 7, and to pattern the second polycrystalline silicon film 8 by anisotropic etching. It is possible to prevent the second polycrystalline silicon film 8 from remaining on the side surface of the nitride film during this process.

<Effects of the Invention> As is clear from the above description, according to the present invention, the thinned hollow portion of the second oxide film on the side surface of the nitride film is filled with a polycrystalline silicon film that is thinner than the first polycrystalline silicon film. Fill,
Next, this is oxidized to form a polycrystalline silicon oxide film, which is then thermally oxidized to form an interlayer insulating film, so that the interlayer insulating film has a uniform thickness when viewed as a whole, and is locally thinned. Since the dielectric breakdown strength of the interlayer insulating film is eliminated, the dielectric breakdown strength of the interlayer insulating film can be improved, and the eaves shape that occurs in the conventional example on the side surface of the nitride film during patterning by anisotropic etching of the second multicrystalline silicon film can be eliminated. Since there is no remaining portion, the performance of the semiconductor device can be improved and the yield can also be improved.

[Brief explanation of the drawing]

1(a) to 1(i) are diagrams showing the manufacturing process of an embodiment of the present invention, and FIGS. 2(a) to 2(8) are diagrams showing the manufacturing process of a conventional semiconductor device. Figure 2(f) is an enlarged view of part A in Figure 2(e), and Figure 2(g) is an enlarged view of part A in Figure 2(e).
) is an enlarged view of part B of FIG. DESCRIPTION OF SYMBOLS 1... Semiconductor substrate, 3... First gate oxide film, 4...
... nitride film, 5... first polycrystalline silicon film, 7...
- Interlayer insulating film, 8... second polycrystalline silicon film, 11.
...Polycrystalline silicon film, 12.12°...Polycrystalline silicon oxide film. Patent applicant: Sharp Corporation Agent
Patent attorney, previously mentioned, 2 people Fig. 1 ((1) Tei 1 m (hJ 2nd (0) j No. 29 (b) Fig. 2 (C) Fig. 2 (d) Fig. 2 (e)

Claims (1)

[Claims] (1) forming a two-layer insulating film by overlapping a first gate oxide film and a nitride film on a semiconductor substrate; forming a first polycrystalline silicon film on the two-layer insulating film; After patterning the film and the nitride film, a second layer is formed by thermal oxidation.
forming an oxide film, depositing a polycrystalline silicon film thinner than the first polycrystalline silicon film over the entire surface of the semiconductor substrate covering the second oxide film, and then oxidizing the thin polycrystalline silicon film. Next, the polycrystalline silicon oxide film is etched to remove the polycrystalline silicon oxide film in the area where the first polycrystalline silicon film does not exist, and then thermal oxidation is performed to form a polycrystalline silicon oxide film. Manufacturing a semiconductor device characterized by forming an interlayer insulating film, then depositing a second polycrystalline silicon film on the entire surface of the interlayer insulating film, and patterning the second polycrystalline silicon film into a predetermined shape. Method.