JPS62183139A - Manufacture of substrate for formation of semiconductor device - Google Patents

Abstract

PURPOSE:To form a gate oxide film on an Si substrate without decreasing a withstanding voltage by laminating an SiO2 film, a polysilicon film, and an oxidation resistant film patterned in a predetermined pattern on the substrate, oxidizing the substrate to form a field oxide film to obtain the field oxide film without bird beaks. CONSTITUTION:An SiO2 film 12 is formed by a thermal oxidation method on an Si substrate 11, a polysilicon film 13 is formed thereon by a CVD method, and a silicon nitride film 14 is sequentially laminated. After a photoresist film 15 of a predetermined pattern is then formed on the substrate, and the film 13 is etched in a predetermined pattern by anisotropic dry etching with the film 15 as a mask. The film 15 used as the mask is then removed. Subsequently, with the film 14 formed by patterning by exposing the substrate in an oxidative atmosphere as a mask the substrate 11 is oxidized together with the film 13 by a thermal oxidation method to form a field oxide film 16. Thereafter, after the film 15 is removed by hot phosphoric acid, the film 13 disposed thereunder is etched with an acid etchant, the film 12 disposed thereunder is removed by etching with hydrofluoric acid to obtain the substrate 11 formed with the film 16.

Description

[Detailed Description of the Invention] [Summary] A method for manufacturing a substrate for forming a semiconductor element, which comprises laminating a SiO2 film, a poly-Si film, and an oxidation-resistant film patterned in a predetermined pattern on a Si substrate. By oxidizing the field oxide film to form a field oxide film, bird's beaks do not occur in the field oxide film, and the withstand voltage of the gate oxide film formed on the element formation area defined by the field oxide film decreases. A method of manufacturing a substrate for forming a semiconductor element in which the formation of a semiconductor element is avoided.

[Industrial application field]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly, to a semiconductor device having a field oxide film that does not generate bird's beak and preventing a gate oxide film formed in a region defined by the field oxide film from causing a drop in breakdown voltage. The present invention relates to a method for manufacturing a forming substrate.

When forming a semiconductor device such as an IC, a method of forming a field oxide film for element isolation on a Si substrate and forming semiconductor elements within a region defined by this oxide film for element isolation to perform element isolation. is taken.

When forming such a field oxide film, it is necessary to prevent the occurrence of bird's beaks in the oxide film and reduce the area of the element formation region, and to prevent the formation of the field oxide film from reducing the area of the Si substrate in the element formation region. It is desired to prevent the gate oxide film formed on the surface of the gate oxide film from decreasing in breakdown voltage.

[Conventional technology]

Conventionally, when forming such a substrate for forming a semiconductor element, as shown in FIG.
A predetermined pattern of silicon nitride I*3 is formed by sequentially using the VD method, photolithography method, and plasma etching method.

Next, using this silicon nitride film 3 as a mask, the substrate 1 is exposed to an oxidizing atmosphere for thermal oxidation to form a field oxide film 4 in the area where the silicon nitride film 3 is opened, as shown in FIG. After that, this silicon nitride film 3 is removed using phosphoric acid or the like to form a field oxide film 4 in a predetermined pattern.
was forming.

[Problem that the invention seeks to solve]

However, with this method, it takes a long time to oxidize the Si substrate 1, so as shown in FIG. During the oxide film formation process, oxidizing gas enters into the silicon dioxide film 2. Furthermore, due to the intrusion of this oxidizing gas, the field oxide film 4 is formed in a bird's beak shape in the element formation region in the lateral direction, and field oxide l
It! 4, a so-called bird's beak 5 extending like a bird's beak is generated in the element forming region in the lateral direction of the substrate 1.

The element formation region is eroded by this bird's beak 5,
This poses a problem that makes it impossible to form fine semiconductor elements.

Therefore, as shown in FIG. 9, a silicon nitride film 3 is directly formed on the substrate 1 without the step of forming the thin oxide film 2, which is the core of the bird's beak generation, and this silicon nitride film 3 is used as a mask. Field oxide film 4 on substrate 1
A process is also being taken to form a

However, in this method, the silicon nitride film 3 is formed directly on the substrate 1, so if the silicon nitride film 3 used as a mask is removed after forming the field oxide film 4, the silicon nitride film 3 will be removed. The surface of the substrate l at the bottom of No. 3 is rough, causing a problem that the withstand voltage of the gate oxide film formed in that portion is reduced.

The present invention eliminates the above-mentioned problems, forms a field oxide film that does not generate bird's beak, and is a method for manufacturing a substrate for forming a semiconductor element, which prevents a drop in breakdown voltage of the gate oxide film formed in the element formation region. The purpose is to provide.

[Means for solving problems]

In the method of manufacturing a semiconductor device of the present invention, S is formed on a Si substrate 11.
a step of sequentially laminating an iO2 film 12, a poly-Si film 13, and an oxidation-resistant film 14; a step of anisotropically etching the oxidation-resistant film 14 into a predetermined pattern to open the oxidation-resistant film 14; a step of exposing the substrate 11 to an oxidizing atmosphere as a mask to oxidize the poly-Si film 13 under the opening of the oxidation-resistant film 14 and the Si substrate 11 thereunder to form a field oxide film 16; A step of etching away the oxidation-resistant film 14 used, the poly-Si film 13 formed on the substrate other than the field oxide film 16, and the 5iO211112 underneath it.
Features [Function] The method for manufacturing a semiconductor device of the present invention is characterized by having a step of removing the field oxide film 1 by etching.
6, the SiO2 film 12 formed on the substrate 11
A poly-Si film 13 whose oxidation rate is about 1.5 times that of the substrate 11 is formed on the poly-Si film 13, and an oxidation-resistant film 14 having an opening where the field oxide film 16 will be formed is formed thereon.

When the substrate 11 thus prepared is introduced into an oxidizing atmosphere using the open oxidation-resistant film 14 as a mask,
Since the oxidation rate of poly 5t13 is fast, it is oxidized quickly,
The time required for oxidation is short, and therefore the time for lateral spread and oxidation is also short, so that bird's beaks do not occur.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, a SiO2 film 12 is formed on a Si substrate 11.
is formed by a thermal oxidation method, and a poly-Si film 1 is formed on it by a CVD method.
3, a Si nitride film 14 as an oxidation-resistant film is sequentially laminated.

Next, as shown in FIG. 2, after forming a photoresist film 15 in a predetermined pattern on the substrate, nitriding 5 is performed using anisotropic dry etching using the photoresist film 15 as a mask.
Ill13 is etched into a predetermined pattern.

Next, as shown in FIG. 3, the photoresist 15 used as a mask is removed.

Next, as shown in FIG. 4, the substrate is exposed to an oxidizing atmosphere, and the poly-Si film 13 and the underlying substrate 11 are oxidized by a thermal oxidation method using the patterned Si nitride film 14 as a mask. A field oxide film 16 is then formed.

In this way, the poly-Si film 13 is oxidized at a rate approximately 1.5 times that of oxidizing the Si substrate, so that the time required to form the field oxidation layer 16 is significantly shortened. Therefore, the time required for the formation of bird's beaks, which are formed by extending the field oxide film in the lateral direction of the opened Si nitride film, is also eliminated, and the formation of bird's beaks is no longer observed.

Next, after removing the Si nitride film 15 with hot phosphoric acid, etching the underlying poly-Si film 13 using an acid-based etching solution, and etching away the underlying SiO2 film 12 using hydrofluoric acid. , a Si substrate 11 having a predetermined pattern of field oxidation 1i116 as shown in FIG. 5 is obtained.

By doing this, bird's beaks will not occur, and since the SiO2 film 12 is formed on the substrate, the substrate surface will not be eroded, and therefore a decrease in the withstand voltage of the gate oxide film formed on this substrate will not be observed. This has the effect that a highly reliable semiconductor device can be obtained.

〔Effect of the invention〕

As described above, according to the method of manufacturing a substrate for forming a semiconductor element of the present invention, a field oxide film that does not generate bird's beaks can be obtained, and even if a gate oxide film is formed on the substrate, a semiconductor device with no decrease in breakdown voltage can be obtained. There is an effect that a substrate for forming an element can be obtained.

[Brief explanation of drawings]

Figures 1 to 5 are cross-sectional views for explaining the manufacturing method of a substrate for forming semiconductor elements according to the present invention in order of steps, and Figures 6 to 7 are cross-sectional views for explaining the conventional method of manufacturing a substrate for forming semiconductor elements. FIG. 8 is a cross-sectional view showing an inconvenient state in the conventional method, and FIG. 9 is a cross-sectional view for explaining the process of a conventional semiconductor element forming substrate. In the figure, 11 is a Si substrate, 12 is an SiO2 film, 13 is a poly-Si film, 14 is an oxidation-resistant film, 15 is a photoresist film, and 16 is a field oxide film. 2t NeJ4arSiO2,,i”JSi#!,@7
#I'-"@ff') FxTnm@ 1 Every year q suspension intoxication → ° Nakoshi r・yf＞7・Nio" dllw
I z fig % 4 qli d 11 t i 14 tt Rt=8F\'ui
c No. 3 Kuni 3 O 4 and a) f's 74-11 lip tie e-Moon mo shape゛T potato ¥ 1 Tomoe J@ 4 flash @ 5Fj! J q;ljf:4rtWt<t! -tqH'fs,'1:
RM Figure 6

Claims (2)

[Claims] (1) A step of sequentially laminating a silicon dioxide (SiO_2) film (12), a poly-Si film (13), and an oxidation-resistant film (14) on a silicon (Si) substrate (11), the oxidation-resistant film ( a step of opening the substrate (14) in a predetermined pattern, using the opened oxidation-resistant film (14) as a mask;
11) in an oxidizing atmosphere, and the oxidation-resistant film (14) is exposed to an oxidizing atmosphere.
) and the poly-Si film (13) under the opening of
A step of oxidizing the i-substrate (11) to form a field oxide film (16), a step of removing the oxidation-resistant film (14) used as the mask by anisotropic etching, and leaving it on the substrate (11). A method for manufacturing a substrate for forming a semiconductor element, comprising a step of etching away a poly-Si film (13) and an underlying SiO_2 film (12). (2) The method of manufacturing a substrate for forming a semiconductor element according to claim 1, wherein the oxidation-resistant film (14) is a silicon nitride film.