JPH02240927A - Manufacture of insulating film for isolation of element in semiconductor device - Google Patents

Abstract

PURPOSE:To enable formation of an element isolation region in uniform dimensions by forming a side wall by making a high-temperature silicon oxide film grow by a chemical vapor deposition method after patterning of a first silicon nitride film and by making a second silicon nitride film thereafter. CONSTITUTION:After formation of a first silicon nitride film 8 serving as an oxidation-resistant masking material, a high-temperature silicon oxide film 9 is made to grow by a chemical vapor growth method in the sidewall part of the first silicon nitride film 8 before a second silicon nitride film 10 is formed as a side wall therein. Therefore, the high-temperature silicon oxide film 9 formed by the chemical vapor deposition method shows a high etching selection ratio at the time of anisotropic dry etching for forming the side wall of the second silicon nitride film 10, and it is left without being etched nearly at all. Accordingly, the first silicon nitride film located under the high-temperature silicon oxide film 9 is not etched at all and acts as the oxidation-resistant masking material with a uniform initial film thickness at the time of its growth left as it is. Thereby the expansion of an element isolation region in the lateral direction is made uniform.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to the production of an insulating film for element isolation of a semiconductor device, in which a silicon oxide film serving as an insulating film for element isolation is formed on a desired portion of the surface of a silicon substrate. It is about the method.

[Conventional technology]

In recent years, with the development of higher integration and miniaturization of MO3 type semiconductor devices, etc., LOC
O3 method, improved LOCO3 method, etc. have come into use.

Below, a conventional method for manufacturing an insulating film for element isolation of a semiconductor device using the improved LOCO3 method will be described.

2(al) to (d) are step-by-step cross-sectional views showing a conventional manufacturing method of an insulating film for element isolation of a semiconductor device using the improved LOCO3 method. In the same figure, l is a P-type silicon substrate;
2 is a silicon oxide film, 3 is a first silicon nitride film, 4 is a second silicon nitride film, and 5 is a silicon oxide film for element isolation.

Next, the steps of the method for manufacturing the element isolation insulating film of this semiconductor device will be described below.

First, a silicon oxide film 2 is grown over the entire surface of a P-type silicon substrate l by a thermal oxidation method, and then a first silicon nitride film 3 is grown on the silicon oxide film 2 by a chemical vapor deposition method.
grow. Next, after patterning with photoresist, dry etching is performed to form a P-type silicon substrate.
The first silicon nitride film 3 outside the upper element region (which becomes the element bone ill tin region) is removed, and then wet etching is performed to remove the silicon oxide film 2 outside the element region on the P-type silicon substrate l. This state, in which the silicon oxide film 2 and the first silicon nitride film 3 are left only in the element region on the P-type silicon substrate l, is shown in FIG. 2 (11).

Next, as shown in FIG. 2(b), a second silicon nitride film 4 is grown over the entire surface of the P-type silicon substrate 1.

Thereafter, as shown in FIG. 2 (c), the second silicon nitride film 4 is etched away by anisotropic dry etching (indicated by arrows), thereby removing the second silicon nitride film 4 grown directly on the P-type silicon substrate l. The film 4 is left only on the sidewall portions of the first silicon nitride film 3 as a sidewall.

Then, as shown in FIG. 2, 1dl, thermal oxidation growth is performed using the first silicon nitride film 3 and the second silicon nitride film 4 remaining on its sidewalls as oxidation-resistant masking material, and the elements are isolated only in the element isolation region. silicon oxide [5] is formed.

As a result, the second silicon nitride film 4 grown directly on the P-type silicon substrate 1 suppresses the lateral growth of the silicon oxide a5 for element isolation, making it possible to miniaturize the element region and the element bone jilt region. Become.

[Problem to be solved by the invention]

However, in the above-described conventional method for manufacturing an insulating film for element isolation of a semiconductor device, during anisotropic dry etching of the second silicon nitride film 4, etching residues of the second silicon nitride film 4 are left on the P-type silicon substrate l. Over-etching is performed to prevent this from occurring. For this reason, the first silicon nitride film 3 is also overetched, the film thickness of the first silicon nitride film 3 is reduced, and the film thickness of the remaining first silicon nitride film 3 is uneven for each P-type silicon substrate 1. becomes. As a result,
The device isolation region extends in the lateral direction, causing variations in the dimensions of the bird's beak, which is not suitable for microprocessing.

In addition, since the second silicon nitride film 4 remaining on the side wall portion of the first silicon nitride film 3 is grown directly on the P-type silicon substrate l, the P-type silicon substrate l below it receives stress and the device There is a problem that when forming the isolation silicon oxide film 5, crystal defects are induced in the P-type silicon substrate 1 from the second silicon nitride film 4, and leakage current is generated at the boundary between the element region and the element isolation region. .

Therefore, an object of the present invention is to provide a method for manufacturing an insulating film for element isolation of a semiconductor device, which can make the dimensions of an element isolation region uniform and can prevent crystal defects from occurring.

[Means to solve the problem]

A method of manufacturing an insulating film for element isolation of a semiconductor device according to the present invention includes the steps of: forming a first silicon nitride film serving as an oxidation-resistant masking material at a location other than the formation area of the insulating film for element isolation on the surface of a silicon substrate; After forming the first silicon nitride film, growing a high temperature silicon oxide film over the entire surface of the silicon substrate by chemical vapor deposition; and after forming the high temperature silicon oxide film, growing a second nitride film to serve as an oxidation-resistant masking material. forming a silicon film as a sidewall on the side wall of the first silicon nitride film; and oxidizing the surface of the silicon substrate using the first silicon nitride film and the second silicon nitride film as a mask, thereby forming the device isolation layer. The method includes a step of forming a silicon oxide film to serve as an insulating film.

[For production]

According to the method of the present invention, after forming the first silicon nitride film serving as an oxidation-resistant masking material, and before forming the second silicon nitride film to be formed as a sidewall on the side wall portion of the first silicon nitride film, chemical By growing a high-temperature silicon oxide film by a chemical vapor deposition method, the high-temperature silicon oxide film formed by the chemical vapor deposition method is It exhibits a high etching selectivity, and most of the material remains unetched. Therefore, the first silicon nitride film underlying the high-temperature silicon oxide film is not etched at all, and functions as an oxidation-resistant masking material while maintaining the uniform initial film thickness during growth. As a result, element bone I
The horizontal spread of the I fil region can be made uniform. Therefore, the dimensions of the element bone jll SI region can be made uniform.

Furthermore, since the second silicon nitride film does not come into direct contact with the silicon substrate, it is possible to prevent the occurrence of crystal defects induced by stress in the second silicon nitride film.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

181 to 181 (dl) are step-by-step cross-sectional views showing a method of manufacturing an insulating film for element isolation of a semiconductor device according to an embodiment of the present invention. In the figure, 6 is a P-type silicon substrate;
8 is a silicon oxide film, 8 is a first silicon nitride film grown only on the element region, 9 is a high-temperature silicon oxide film grown to cover the entire surface of the first silicon oxide film 8, and IO is a silicon oxide film grown by forming sidewalls. The second silicon nitride film 11 remaining only on the side wall portion of the first silicon nitride film 8 is a silicon oxide film for element isolation which is an insulating film for element isolation grown by LOCO5.

Next, the steps of the method for manufacturing the element isolation insulating film of this semiconductor device will be described below.

First, the P-type silicon substrate 6 is subjected to RCA cleaning, and the silicon oxide film 7 is grown to a thickness of, for example, 500 nm using a thermal oxidation method. Then, by chemical vapor deposition, 5iH2Cj,
Using a mixed gas of 2 (dichlorosilane) gas and NH3 (ammonia) gas, the first silicon nitride 1I18 is grown to a thickness of, for example, 1500 nm over the entire surface at a temperature of, for example, 780°C. Then, the device region and the device bone 1 m 8N region are patterned using photoresist, and the first silicon nitride film 8 on the device isolation region (outside the device region) of the P-type silicon substrate 6 is removed by dry etching. Then, the silicon oxide film 7 at the same location is removed by wet etching, and the silicon oxide IT and the first silicon nitride film 8 are formed only on the element region of the P-type silicon substrate 6.
and create a shape that remains.

This state is shown in FIG. 1 (al).

Next, as shown in FIG. 1 1bl, SiH, Cm! After growing a high-temperature silicon oxide film 9 to a thickness of, for example, 150 mm on the entire surface of the P-type silicon substrate 6 at a temperature of, for example, 870° C. using a mixed gas of 2 gas and N20 gas, the first silicon nitride@ A second silicon nitride film 1O is grown to a thickness of, for example, 1000 nm under the same growth conditions as B.

Then, as shown in Figure 1 (C1), anisotropic dry etching (
) is performed for, for example, 1 minute and 40 seconds, and then additional dry etching is performed for, for example, 10 seconds so that there is no etching residue on the second silicon nitride film 10. As a result, the etching is performed only on the side wall portion of the first silicon nitride film 8. The silicon 2 nitride film 10 remains as a sidewall.

At this time, even if additional dry etching is performed, the high temperature silicon oxide 119 on the first silicon nitride M8 is CH2F2
/ 02 fA Since it is hardly etched by the combined gas, the l! of the first silicon nitride film 8 is reduced by additional dry etching. In other words, when forming the sidewall with the second silicon nitride 1110, it is possible to leave the first silicon nitride film 8 having a uniform thickness during growth on the entire surface of the P-type silicon substrate 6. It is.

Then, as shown in FIG. 1(d), the element isolation silicon oxide film 11 is grown to a thickness of, for example, 7,000 layers by thermal oxidation to form the element bone R region.

At this time, as shown above, since the film thickness of the first silicon nitride 11a8 is uniform on the surface of the P-type silicon substrate 6, the silicon oxide film for element isolation! The size of the region (bird's beak) where l extends in the lateral direction is constant, and the dimensions of the element region and the element isolation region on the surface of the P-type silicon substrate 6 are uniform.

Further, after forming the high temperature silicon oxide film 9, in order to form the second silicon nitride film IO, the second silicon nitride film 10 is
does not come into direct contact with the P-type silicon substrate 6, the stress from the second silicon nitride film lO to the P-type silicon substrate 6 is relaxed, and it is possible to prevent crystal defects from occurring within the P-type silicon 5IliS. Therefore, it is also possible to prevent leakage current from occurring at the boundary between the element region and the element bone HSI region.

〔Effect of the invention〕

According to the method of manufacturing a vA edge film for element isolation of a semiconductor device of the present invention, after patterning the first silicon nitride film, a high temperature silicon oxide film is grown by chemical vapor deposition, and then a second silicon nitride film is grown. By growing and forming sidewalls, element isolation regions can be formed with uniform dimensions on the surface of the silicon substrate. Furthermore, since the second silicon nitride film is formed on the high-temperature silicon oxide film, stress from the second silicon nitride film to the silicon substrate is alleviated, making it possible to prevent crystal defects from occurring within the silicon substrate. .

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a method of manufacturing an insulating film for element isolation of a semiconductor device according to an embodiment of the present invention, and FIG.
FIG. 3 is a step-by-step cross-sectional view showing an example of a conventional method for manufacturing an insulating film for element isolation of a semiconductor device using three methods. 6... P-type silicon substrate, 7... silicon oxide film,
8... First silicon nitride film, 9... High temperature silicon oxide film, 10... Second silicon nitride film, 11... Silicon oxide film for element isolation.

Claims (1)

[Claims] a step of forming a first silicon nitride film serving as an oxidation-resistant masking material on a surface of the silicon substrate other than the formation region of an insulating film for element isolation; and a step of forming a first silicon nitride film as an oxidation-resistant masking material over the entire surface of the silicon substrate after forming the first silicon nitride film. a step of growing a high-temperature silicon oxide film by a chemical vapor deposition method; and a second step of growing a high-temperature silicon oxide film as an oxidation-resistant masking material after the formation of the high-temperature silicon oxide film.
forming a silicon nitride film as a sidewall on the side wall of the first silicon nitride film; and oxidizing the surface of the silicon substrate using the first silicon nitride film and the second silicon nitride film as a mask to separate the elements. 1. A method for manufacturing an insulating film for element isolation of a semiconductor device, comprising the step of forming a silicon oxide film to serve as an insulating film.