JPS61222158A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To improve a layer insulation withstand-voltage and reform a side surface shape of the first polycrystalline silicon film, by overetching a nitrided film, covering only the side surface part with a thin polycrystal silicon film, and then forming a layer insulation oxide film. CONSTITUTION:Likewise as before, the first polycrystalline silicon film 15 is etched, with patterning-processed photo-sensitive resin 16 serving as mask, and after removing the photo-sensitive resin 16, a nitrided film 14 is overetched, with a patterning-processed first polycrystalline silicon film 15 serving as mask. Then, a thin polycrystalline silicon film 17 is piled all over the surface, and the thin polycrystalline silicon film 17 is etched, by thickness of he film, by the use of an anisotropic etching, so that only the side surface part of the nitrided film 14 is covered with the thin polycrystalline silicon film 17. Next, with the first polycrystalline silicon film 15 serving as mask, the first gate oxide film 13 is removed, and a layer insulation oxide film is formed by thermally oxidizing a semiconductor substrate 11, and then the second polycrystalline silicon film is made to grow into a desired shape patterning.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a semiconductor device (semiconductor integrated circuit: silicon game).
MOS dynamic memory integrated circuit, etc.).

<Summary of the Invention> The method of manufacturing a semiconductor device of the present invention includes the following steps a) to e.
).

a) Step of forming a two-layer insulating film by overlapping a gate oxide film and a nitride film on a semiconductor substrate, and further forming a first polycrystalline silicon film on this two-layer insulating film.

b) Patterning the first polycrystalline silicon film into a predetermined shape.

C) After excessively etching the nitride film, a step of depositing a polycrystalline silicon film thinner than the first polycrystalline silicon film over the entire surface of the raised conductor substrate.

d) A step of anisotropically etching the thin polycrystalline silicon film by its thickness, leaving the thin polycrystalline silicon film only on the side surfaces of the nitride film.

e) After oxidizing the thin polycrystalline silicon film on the side surface of the nitride film and the surface layer of the first polycrystalline silicon film, a second polycrystalline silicon film is deposited on the entire surface, and this second polycrystalline silicon film is A process of patterning a film into a predetermined shape.

<Conventional technology> First, a conventional method will be explained.

FIG. 2 is a manufacturing process diagram of a conventional method.

I gate oxide film 8. A nitride film 4 is formed, and then a polycrystalline silicon film 5 is formed, and a photosensitive resin 6 is left behind so that a desired pattern is formed using a normal photolithography technique.

Next, as shown in FIG. 2(b), using the patterned photosensitive resin 6 as a mask, the polycrystalline silicon film 5, the nitride film 4. After sequentially etching the first gate oxide film 3, the second gate oxide film 3 is etched.
As shown in Figure (e), an interlayer insulating oxide film 7 is formed by thermally oxidizing the semiconductor substrate l.

Next, as shown in FIG. 2(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> According to the above conventional method, the oxide film 7 formed at the location shown as 9 in FIG. 2(e), that is, the side surface of the nitride film 4
(An enlarged view is shown in FIG. 3+11), the first polycrystalline silicon film 5 and the second polycrystalline silicon film 8 become thinner locally (an enlarged view is shown in FIG. 3+11). In addition, when patterning the second polycrystalline silicon film 8 by anisotropic etching, the insulating oxide film 7 between the eyebrows is Because it becomes an eave shape at the part (an enlarged view is shown in Figure 8 (2)),
The second polycrystalline silicon 8 remains in this part without being etched, and there is a high possibility that the second polycrystalline silicon will short-circuit with each other, and the expected yield rate cannot be obtained. was.

The present invention aims to solve the above-mentioned problems in the conventional method. That is, the present invention provides a method of manufacturing a semiconductor device that eliminates the above-mentioned drawbacks and makes it possible to improve the glabellar dielectric strength and the shape of the side surface of the first polycrystalline silicon film.

<Means for resolving the problem> The nitride film is over-etched, only the side surfaces thereof are covered with a thin polycrystalline silicon film, and then an interlayer insulating oxide film is formed.

<Function> By having the above structure, it is possible to prevent a local decrease in the thickness of the interlayer insulating oxide film, thereby solving the problem of short circuits between polycrystalline silicon films, which has been a problem in the past. It is.

<Example> Hereinafter, the present invention will be described in detail based on Examples.

FIG. 1 is a manufacturing process diagram of an embodiment of the present invention.

First, a field oxide film 12 is formed on a semiconductor substrate 11 by the Locos oxidation method, and then a first gate oxide film 13. After forming a nitride film 14, a first polycrystalline silicon film 15 with a thickness of 4000 to 500oλ is formed by chemical vapor deposition.
and photosensitive resin 16i by ordinary photolithography technology.
The structure shown in FIG. 1(a) is obtained by leaving it in a desired shape.

Next, the first polycrystalline silicon film 15i is etched using the patterned photosensitive resin 16 as a mask, and after removing the photosensitive resin 16, the nitrided silicon film 15i is etched onto the patterned first polycrystalline silicon film 15i as a mask. The film 14 is over-etched by about 200λ with a phosphoric acid solution to obtain the structure shown in FIG. 1(b).

Next, as shown in FIG. 1(c), a thin polycrystalline silicon film 17i with a thickness of 100 to 100 OA is deposited over the entire surface.

Next, the thin polycrystalline silicon film 17 is etched by the thickness thereof by anisotropic etching, and only the side surfaces of the nitride film 14 are covered with the thin polycrystalline silicon film 17, resulting in the structure shown in FIG. 1(d). get.

Next, the first gate electrode patterned in the shape of the first gate electrode is
Using the polycrystalline silicon film 15 as a mask, portions of the first gate oxide film 13 where the first polycrystalline silicon film does not exist are removed by oxide film etching to obtain the shape shown in FIG. 1(e).

Next, by thermally oxidizing the semiconductor substrate 11, as shown in FIG. 1(f), an insulating oxide film 18i between the eyebrows is formed, followed by a second polycrystalline silicon film! Growing up to 9, Figure 1 (b)
) to obtain the structure. This second polycrystalline silicon film 19 is patterned into a desired shape to obtain the structure shown in FIG. 1(h).

<Effects of the Invention> As described above in detail, according to the present invention, the nitride film is over-etched and only the side surfaces thereof are covered with a thin polycrystalline silicon film, thereby making it possible to form the interlayer insulating oxide film. , it is possible to prevent the local reduction in oxide film thickness at the lower side of the first polycrystalline silicon film, which was seen in the conventional method, and improve the dielectric breakdown strength of the glabella insulating oxide film, which was a drawback of the conventional method. In addition, it is possible to prevent etching residues from occurring during patterning of the second polycrystalline silicon film by anisotropic etching, and it is also possible to prevent short circuits between the second polycrystalline silicon films. be.

[Brief explanation of the drawing]

Figures 1 (a) to (h) are manufacturing process diagrams of an embodiment of the present invention, Figures 2 (a) to (e) are manufacturing process diagrams of a conventional manufacturing method, and Figures 3 (1), ( 2) is a partially enlarged view of FIG. 2(e). Explanation of symbols 1: Semiconductor substrate, 2: Field oxide film, 3: First gate oxide film, 4: Gate nitride film, 5: First polycrystalline silicon film, 6: Photosensitive resin, 7: Interlayer insulation oxide film, 8: second polycrystalline silicon film, 9: locally thin portion of interlayer insulating oxide film, 10: etched remaining portion of second polycrystalline silicon film, 11: semiconductor substrate, 12: ° field oxide film, 18
: first gate oxide film, 14: gate nitride film, 15: first
Polycrystalline silicon film! 6: photosensitive resin, 17: thin polycrystalline silicon film, 18 bibrow insulating oxide film, 19: second polycrystalline silicon film. Agent Patent attorney Aihiko Fukushi (and 2 others) Figure 1

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device, characterized by comprising the following steps a) to e). a) Step of forming a two-layer insulating film by overlapping a gate oxide film and a nitride film on a semiconductor substrate, and further forming a first polycrystalline silicon film on this two-layer insulating film. b) Patterning the first polycrystalline silicon film into a predetermined shape. c) After excessively etching the nitride film, depositing a polycrystalline silicon film thinner than the first polycrystalline silicon film over the entire surface of the semiconductor substrate. d) A step of anisotropically etching the thin polycrystalline silicon film by the thickness thereof, leaving the thin polycrystalline silicon film only on the side surfaces of the nitride film. e) After oxidizing the thin polycrystalline silicon film on the side surface of the nitride film and the surface layer of the first polycrystalline silicon film, a second polycrystalline silicon film is deposited on the entire surface, and this second polycrystalline silicon film is A process of patterning a film into a predetermined shape.