JPH03280429A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To avoid the occurrence of bird's beak during the selective oxidation process by a method wherein the second oxidation resistant insulating film is deposited on the whole surface of the first insulating film having an opening part on a semiconductor substrate, a coated film at almost the same etching rate is formed leaving the second insulating film only in the opening part by the whole surface etching process to be selectively oxidized for element isolation. CONSTITUTION:A CVD oxide film 11 as the first insulating film is deposited on a semiconductor substrate 10 further exposed and developed for patterning to make an opening part. Next, after depositing a CVD nitride film 13 as the second insulating film, a coated film 14 at almost the same etching rate is deposited, the surface is flattened and etched away until the nitride film 13 on the CVD oxide film 11' disappears and then the coated film 14' and the CVD oxide film 11' are removed by wet etching process. Next, the whole surface is selectively oxidized to form a field oxide film 16 after ion implantation for preventing the interelement parasitic channel using the CVD nitride film 13' as a mask. Finally, the CVD nitride film 13' is wet-etched to finish the element isolation.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and in particular to an element isolation technique in an LSI.

[Conventional technology]

As an LSI manufacturing technique, an element isolation technique using a thick oxide film by selective oxidation using a nitride film as a mask is well known. This technique will be explained with reference to FIG. The same figure (a
), a thermal oxide film 2 and a CV
Deposit D nitride film 3. Thermal oxidation W22 acts as a relaxing material to prevent stress during dry etching for patterning the CVD nitride film 3. Next, as shown in FIG. After removing the CVD nitride film in the element isolation region as a mask, ion implantation is performed to prevent parasitic channels between elements. After removing the photoresist 4 as shown in Figure (C), for example! 000
Oxidation is carried out at 0.degree. C. in H7-02 atmosphere. The CVD nitrided W23 has strong oxidation resistance and acts as a mask against oxidation, and is thickly oxidized only in the area excluding the element area, forming the field oxide film 6. Next, when the thin underlying thermally oxidized W22 is removed, the same figure ( As shown in d), element isolation is completed.

[Problem to be solved by the invention]

In the conventional device isolation method described above, the thermal oxide film (pad oxide film) underlying the nitride film of the oxidation-resistant mask is oxidized in the lateral direction during field oxidation, resulting in bird's beaks.
There was a drawback that an oxide film was formed in the shape of a rd's beak, and the width of the element region was different from the mask dimension. It also became a restriction on high integration.

An object of the present invention is to provide a method for manufacturing a semiconductor device that eliminates the above-mentioned drawbacks.

[Means to solve the problem]

The method for manufacturing a semiconductor device of the present invention includes a step of forming a first insulating film having an opening on a semiconductor substrate at a predetermined location of an element region, and then growing an oxidation-resistant second insulating film over the entire surface. a step of forming a coating film having an etching rate similar to that of the second insulating film on the second insulating film and flattening the surface; and a ninth step of forming a second insulating film only in the opening by etching the entire surface Element isolation is performed by a step of leaving the oxide film and a step of performing selective oxidation using the second insulating film.

[Effect]

In the present invention, Im! When creating a mask using a oxidizing insulating film, dry etching is not performed, so there is no need for a pad oxide film that acts as a stopper to prevent damage during dry etching.Therefore, bird's beaks do not occur during selective oxidation. There is no.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view showing the first embodiment in the order of steps. As shown in FIG. 4A, CVD oxidation 17911 is deposited on the semiconductor substrate 10 as a first insulating film.

After coating the photoresist 12, exposure and development are performed to pattern and open only the element region so that there is no photoresist. As shown in FIG. 4B, after CVD nitride film 13 is deposited as a second insulating film, a coating film 14 having a knee and ting rate similar to that of the nitride film is deposited to flatten the surface.

Next, as shown in the same figure (C), while performing reactive ion etching until the nitride film on the CVD oxide [11' is removed], the coating mx, a' and Cv are etched.
PS 11111' is removed by 7-torching. After that, as shown in the same figure (d), the CVD nitride film 13 is
′ as a mask, after ion implantation (15 boron ions in the case of N channel) to prevent parasitic channels between elements, selective oxidation is performed at 1000° C. in H2-07 atmosphere, for example.
A field oxide film 16 is formed. Finally, as shown in FIG. 2(e), device isolation is completed by weight-etching the CVD nitride film 13'.8 If the semiconductor substrate is doped with a high degree of impurity, Unlike the case in the example, ion implantation for channel prevention is unnecessary, so the CVD method in Fig. 1(c)
Oxidation j! In this example, where II1' is not removed but field oxidized, the degree of selective oxidation required to obtain a desired field oxide film thickness is small, so that the influence of stress during selective oxidation is small.

〔Effect of the invention〕

In the selective oxidation isolation method, selective oxidation is performed by forming an oxidation-resistant insulating film at the intended location of the element region. Conventionally, there is a thin oxide film under the oxidation-resistant insulating film, A bird's beak was occurring. However, in the present invention, the step of forming the pattern of the oxidation-resistant insulating film (second insulating film) in the element region is performed so that the IFL oxidizing insulating film remains in the opening of the first insulating film in direct contact with the substrate. Do it in a certain way. Therefore, there is no oxide film under the oxidation-resistant insulating film, and bird's beaks do not occur during selective oxidation.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing one embodiment of the present invention, and FIG. 2 is a vertical cross-sectional view of a conventional example. 10... Semiconductor substrate, 11, 11'... CVD 1'l film (whistle th
& kn W5) 13.13'...CVD nitride film (second insulation M) 14.14'...Coating film, 15...Boron ion, 16...Field oxide film. Patent applicant NEC Corporation

Claims (1)

[Claims] a step of forming a first insulating film having an opening on a semiconductor substrate at a predetermined location of an element region; a step of growing an oxidation-resistant second insulating film over the entire surface; a step of forming a coating film having an etching rate similar to that of the second insulating film and flattening the surface; a step of leaving the second insulating film only in the opening by etching the entire surface;
1. A method of manufacturing a semiconductor device, which includes a step of performing selective oxidation using an insulating film to perform element isolation.