JPS6018935A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain double layer poly Si structure having high insulating properties by removing a thermal oxide film formed on the surface of a first layer poly Si film and forming a thermal oxide film on the surface of the first layer poly Si film again. CONSTITUTION:A Si oxide film 2 is grown on a semiconductor base body 1. A first layer poly Si film 3 is grown on the film 2, and phosphorus as an N type impurity is introduced. The film 3 is patterned to a desired shape to form a first layer poly Si film 3'. The film 3' is thermally oxidized in a high-temperature oxidizing atmosphere to form a Si oxide film 5. A film 4 is removed, and a final Si oxide film 5 between the first poly Si film-a second poly Si film is grown through second thermal oxidation in the high-temperature oxidizing atmosphere. Since a stepped section is reduced through the formation of the first oxide film and a removal by subsequent etching in the film 3' at that time, corner sections are rounded, and the film 5 shaped on the film 3' is formed in uniform thickness. A second layer poly Si film 6 is formed on the film 5. According to the method, the concentration of an electric field in the layer 3' section can be relaxed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for manufacturing a semiconductor device having a two-layer polysilicon structure.

[Prior art]

In general, the silicon oxide film obtained when polysilicon is thermally oxidized has poor insulation properties compared to the silicon oxide film obtained when monocrystalline silicon is oxidized, and to improve this, high-temperature oxidation is It is well known that it is effective.

However, if the first layer polysilicon has a step part, electric field concentration occurs in this part, and when a thin silicon oxide film is required, such as in an insulating quantum element, the insulation property decreases at the step part. There is a drawback.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks, alleviate electric field concentration at the stepped portion of the first layer polysilicon film, and provide a double layer with a highly insulating oxide film between the first layer polysilicon and the second layer polysilicon. An object of the present invention is to provide a method for manufacturing a semiconductor device having a layered polysilicon structure.

[Configuration of the Invention] A method for manufacturing a semiconductor device according to the first aspect of the present invention includes the steps of growing a first layer polysilicon film on the upper surface of a semiconductor substrate having an insulating film on the surface, and growing the first layer polysilicon film on the upper surface of a semiconductor substrate having an insulating film on the surface. a step of buttering the film into a desired shape, a step of forming a silicon oxide film on the surface of the buttered first layer polysilicon film in a high temperature oxidizing atmosphere, and a step of removing the silicon oxide film; A step of forming a silicon oxide film again in a high-temperature oxidizing atmosphere on the surface of the first layer polysilicon film from which the silicon oxide film has been removed, and a step of growing a second layer polysilicon film on the entire surface treated with the silicon oxide film. It consists of:

The method for manufacturing a semiconductor device according to the second aspect of the present invention includes the steps of growing a first layer polysilicon film on the upper surface of a semiconductor substrate 2 having an insulating film on the surface, and forming an acid-resistant polysilicon film on the first layer polysilicon film. a step of growing an oxidation-resistant material film, a step of sequentially patterning the oxidation-resistant material film and the first layer polysilicon film into a desired shape, and oxidation in a high-temperature oxidation atmosphere using the oxidation-resistant material film as a mask. a step of growing a silicon oxide film on the side surface of the first layer polysilicon film; a step of etching away the silicon oxide film; a step of etching and removing the oxidation-resistant material film; a step of forming a silicon oxide film in a high-temperature oxidizing atmosphere on the surface of the first layer polysilicon film from which the oxidizing material film has been removed; and a step of growing a second layer polysilicon film on the entire surface covered with the silicon oxide film. It consists of:

[Explanation of Examples]

Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1(a) to 1(d) are cross-sectional views shown in order of steps for detailed explanation of the first invention of the present invention.

First, as shown in FIG. 1(a), a cricon oxide film 2 is grown on a semiconductor substrate J to a thickness of 500 mm. Next, a first layer polysilicon film 3 is grown on the silicon oxide film 2 to a thickness of 2000^ by the CVD method, and then phosphorus, which is an N-type impurity, is added to the first layer using a normal vapor phase thermal diffusion method. It diffuses into the polysilicon film 3. This phosphorus may be introduced by ion implantation at °C.

Next, as shown in FIG. 1(b), the first layer polysilicon film 3 is patterned into a desired shape by plasma etching using an ordinary resist as a mask to form a first layer polysilicon film 3'. The first layer polysilicon film 3' is 11
Thermal oxidation in a high-temperature oxygen atmosphere at 00°C to a thickness of approximately 80OA.
A silicon oxide film 4 is formed.

Next, as shown in FIG. 1(C), after removing the silicon oxide film 4 by etching with buffered hydrofluoric acid, thermal oxidation is performed again in a dry atmosphere at a high temperature of 1100° C. to form the final first polyurethane. A silicon oxide film 5 between the silicon film and the second polysilicon film is grown to a thickness of 40 OA.

In this case, the first layer polysilicon film 3' has fewer steps due to the initial oxide film formation and subsequent etching removal, so the corners are rounded as shown in FIG. The silicon oxide film 5 thus formed has a uniform thickness.

Next, as shown in FIG. 1(d), a second layer polysilicon film 6 is formed on the silicon oxide film 5 at a film thickness of 500 nm by the CVD method.
When grown to a thickness of A, a capacitive element with a two-layer polysilicon structure can be formed.

The semiconductor device with the two-layer polysilicon structure formed as described above, for example, the capacitor element, has rounded corners due to the process of the present invention.
The insulating film between the second polysilicon layer and the second polysilicon layer is smooth with no corners and has a uniform thickness, improving insulation and reducing leakage current. Furthermore, since N-type impurities are diffused into the first layer polysilicon film 3', the resistance of this portion is reduced, and the characteristics of the capacitive element are greatly improved.

FIGS. 2(a) to 2(e) are cross-sectional views showing the process order of the second aspect of the present invention for detailed explanation.

First, as shown in FIG. 2(a), a silicon oxide film 2 is grown on a silicon substrate 1 to a thickness of 50 OA. Next, a first layer polysilicon film 3 is deposited on the silicon oxide film 2.
It is grown to a thickness of 2000^ by the V'D method, and phosphorus, which is an N-type impurity, is diffused by a thermal diffusion method from the normal gas phase. Note that in this step, a method other than the CVD method may be used for growing the polysilicon film. Further, ion implantation may be used to introduce phosphorus. Next, a silicon nitride film 7 is grown to a thickness of 400 nm over the entire surface by CVD.

Next, as shown in FIG. 2 (b), the silicon nitride film 7
Then, the first layer polysilicon film 3 is sequentially patterned into a desired shape by plasma etching using an ordinary resist as a mask to form a first layer polysilicon film 3' and a silicon nitride film 7'.

Next, as shown in FIG. 2(c), K, silicon nitride film 7'
1 on the side surface of the first layer polysilicon film 3' using as a mask.
A silicon oxide film 8 is formed by oxidation in a dry oxygen atmosphere at a high temperature of 100°C. At this time, the first mth polysilicon film 3'
The corners become rounded due to oxidation.

Next, as shown in FIG. 2(d), the silicon oxide film 8 grown on the side surface of the first layer polysilicon film 3' is removed by etching with buffered hydrofluoric acid, and then silicon nitride film 8, which is used as an oxidation-resistant mask, is removed. The film 7' is sequentially etched away using hot phosphoric acid. Next, the surface of the exposed first layer polysilicon film 3' is thermally oxidized in a high temperature dry oxygen atmosphere at 1100° C. to grow a silicon oxide film 5 to a thickness of 40 OA.

Next, as shown in FIG. 2(e), a second layer polysilicon film 6 is formed on the silicon oxide film 5 at a thickness of 500 OA by CVD.
When grown, a capacitive element made of two-layer polysilicon can be formed.

The above embodiment according to the second aspect of the present invention exhibits the same effect as the above embodiment, and in the first high temperature oxidation and etching process, the surface of the first layer polysilicon film 3' is made of an oxidation-resistant control film. No deterioration of a certain silicon film surface condition occurs, and the surface condition of the first layer polysilicon film is maintained as in the conventional example.

Therefore, the effect of improving the insulation properties due to the edge blunting of the first layer polysilicon film is not reduced by deterioration of the surface condition of the first layer polysilicon film, so that the first layer polysilicon film is flat without any steps. It exhibits insulation properties equivalent to those with a similar structure. Also in this example, N is added to the first layer polysilicon film.
Since type impurities are added, the characteristics of the completed capacitive element can be greatly improved.

FIG. 3 is a cross-sectional view of a capacitive element having a two-layer polysilicon structure in which there is no step in the first layer polysilicon film, and is cited for comparison.

FIG. 4 shows a leakage current-voltage characteristic diagram of the capacitive elements of the first and second aspects of the present invention, the flat structure, and the conventional example.

As is clear from the figure, the embodiment of the first invention of the present invention exhibits higher insulation than the conventional example, but the embodiment of the second invention of the present invention has even higher insulation than the embodiment of the first invention. It shows C. It is clear that the IV characteristic is equivalent to that of a capacitive element having a flat structure as shown in FIG.

〔Effect of the invention〕

As explained above, according to the present invention, etching of the stepped portion of the first layer polysilicon film is slowed down, electric field concentration at that portion is alleviated, leakage is suppressed, and the first layer polysilicon film with high A semiconductor device having a two-layer polysilicon structure having an oxide film between the film and the second layer polysilicon film is obtained.

[Brief explanation of drawings]

FIGS. 1(a) to (d) are cross-sectional views shown in order of steps for detailed explanation of the first invention of the present invention, and FIGS. 2(a) to (e)
) is a cross-sectional view shown in the order of steps for detailed explanation of the second invention of the present invention, FIG. FIG. 4 is a leakage current-voltage characteristic diagram of an embodiment of the first invention and the second invention of the present invention, a conventional example, and a capacitor element with a flat structure. 1°゛°°°° silicon semiconductor substrate, 2... silicon oxide film, 3... first layer polysilicon film,
4...Silicon oxide film, 5...First layer-second layer polysilicon interlayer insulating film, 6゛゛・°゛second
Polysilicon film 7... ...Mask nitride film, 8...Silicon oxide film. 3 9 83 Wards Figure 4

Claims (3)

[Claims] (1) A step of growing a first layer polysilicon film on the upper surface of a semiconductor substrate having an insulating film on the surface, a step of patterning the first layer polysilicon film into a desired shape, and a step of A step of forming a silicon oxide film on the surface of the first layer polysilicon film in a high temperature oxidizing atmosphere, a step of removing the silicon oxide film, and a step of forming a silicon oxide film on the surface of the first layer polysilicon film from which the silicon oxide film has been removed in a high temperature oxidizing atmosphere. A method for manufacturing a semiconductor device, comprising the steps of: forming a silicon oxide film again; and growing a second layer polysilicon film on the entire surface covered with the silicon oxide film. (2) a step of growing a first layer polysilicon film on the upper surface of the semiconductor substrate t having an insulating film on the surface; a step of growing an oxidation-resistant material film on the first layer polysilicon film; and a step of growing an oxidation-resistant material film on the first layer polysilicon film; a step of sequentially patterning the oxidation-resistant material film and the first layer polysilicon film into a desired shape, and oxidizing the oxidation-resistant material film in a high temperature oxidizing atmosphere using the oxidation-resistant material film as a mask to form the first layer polysilicon simulated surface. A step of growing a silicon oxide film, a step of etching away the silicon oxide film, a step of etching away the oxidation-resistant material film, and a first layer from which the silicon oxide film and the first oxidation-resistant material film have been removed. A step of forming a silicon oxide film on the surface of the polysilicon film in a high-temperature oxidizing atmosphere, and a step of forming a second silicon oxide film on the entire surface defined by the silicon oxide film.
A method for manufacturing a semiconductor device, comprising the step of growing a layered polysilicon film. (3) A method for manufacturing a semiconductor device according to claim (1) or (2), characterized in that an N-type impurity is added to the first polysilicon film.