JPS61119056A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable to reduce the stress to be applied to the boundary part of the surface of the silicon semiconductor substrate and the isolated groove in the process of thermal oxidation to be performed atfer the isolated groove is formed and to suppress the malfunction of the element, which is caused by the generation of deterioration of the characteristics of the element and a defect of the element due to strain, by a method wherein a curvature is made to hold at the boundary part by the thermal oxide film forming process and the thermal oxide film etching process. CONSTITUTION:A silicon nitride film 12 is coated on a silicon semiconductor substrate 11 in a thickness of 1,000-5,000Angstrom , a pattern is formed by a photo etching method and part of the silicon semiconductor substrate 11 is made to expose. After that, an oxidation is selectively performed on the silicon semiconductor substrate 11 by a thermal oxidation method, a silicon dioxide film 13 of the thickness of 1,000-2,000Angstrom is formed and this silicon dioxide film 13 is removed by an isotropic etching method. Then, an etching is selectively performed on the silicon semiconductor substrate 11 to a depth of 1-6mum by an an isotropic etching method using the silicon nitride films 12 as masks and an isolated groove is formed. After an etching is performed on the silicon nitride films 12, an thickness of 1,000-7,000Angstrom by a thermal oxidation method and a second silicon dioxide film 14 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a method of manufacturing a semiconductor device having an isolation trench on a silicon semiconductor substrate.

(Prior art) Conventionally, in order to form an isolation trench in a silicon semiconductor substrate, an insulating film is formed on the silicon semiconductor substrate, an opening is formed in the insulating film, and the opening is formed using the insulating film as a mask. The silicon semiconductor substrate is etched by an anisotropic etching method to form a separation groove, but according to this method, the boundary between the silicon semiconductor substrate surface and the corresponding groove is straight; In the thermal oxidation step after the #O formation, stress is applied to the nuclear boundary portion, resulting in undesirable problems in terms of device characteristics such as generation of defects. Therefore, the distance between the m-groove and the element becomes large, which becomes an obstacle to high integration of the element.

(Object of the Invention) The present invention provides a method for manufacturing a semiconductor device that eliminates the above-mentioned drawbacks and makes it possible to reduce the stress in the oxidized two sets of the silicon semiconductor substrate surface and the isolation trench.

(Structure of the Invention) The present invention includes a step of forming a silicon nitride film on a silicon semiconductor substrate, a step of selectively etching the silicon nitride film, and a step of etching the silicon nitride film on the silicon/semiconductor substrate. A step of selectively oxidizing to form a silicon dioxide film, a step of removing the silicon dioxide film, and etching the silicon semiconductor substrate by an anisotropic etching method using the silicon nitride film as a mask to form an insulating isolation groove. 1. A method of manufacturing a semiconductor device, comprising: a step of forming a semiconductor device;

(Effects of the Invention) According to the present invention, the thermal oxide film forming step and the thermal oxide film forming step can provide a curvature at the boundary between the silicon semiconductor substrate surface and the isolation trench, and It is possible to reduce the stress applied to the boundary part during the thermal oxidation process, and it is possible to suppress the deterioration of element characteristics due to strain and the occurrence of defects in the element, which allows the distance between the groove and the element to be reduced, resulting in higher height. This has the effect of enabling integration.

(Example) Next, in order to better understand the characteristics of the present invention, one conventional method and the method of the present invention will be explained using the drawings. First, a conventional method will be explained.

FIGS. 1(a) to 1(d) are cross-sectional views illustrating the main steps of a conventional method for forming isolation trenches in semiconductor devices. First, Figure 1 (J
L) 1 is a silicon semiconductor substrate.

A silicon dioxide film (or silicon nitride pa>z) is coated on the silicon conductive substrate to a thickness of 300X using the CVD method, and a pattern is formed by photolithography (FIG. 1(b)).

Thereafter, using the silicon dioxide film 2 as a mask, the silicon semiconductor substrate 1 is etched to a depth of 3 μm by an anisotropic etching method to form a separation groove (FIG. 1C). After etching, the silicon semiconductor substrate 1 is oxidized to a thickness of 4000 Å by thermal oxidation to form a @2 silicon dioxide film 3 (FIG. 1 (ψ)).

As described above, when the conventional manufacturing method is followed, there is a drawback that when the silicon semiconductor substrate 1 is thermally oxidized, stress is applied to the boundary between the ILI groove and the surface of the silicon semiconductor substrate, causing defects. Next, the present invention will be explained by examples.

FIGS. 2(JL) to 2(f) are first views of a semiconductor device for explaining the present invention in detail. In FIG. 2 (&), 11 is a silicon semiconductor substrate, and a silicon nitride film 12 is deposited on the silicon semiconductor substrate 11 by CVD method.
A layer of OA to 5000A is deposited, and a pattern T is formed by photolithography to expose a part of the silicon semiconductor substrate 11 (FIG. 2 φ)). Thereafter, the silicon semiconductor substrate 11 is selectively converted into 3 by thermal oxidation method.
A silicon dioxide film 13 having a thickness of 0X to 20,000X is formed (FIG. 2(C)), and the silicon dioxide film 13 is removed by an isotropic etching method (FIG. 2(Φ)).Then, the silicon nitride film 12 is As a mask, the silicon semiconductor substrate 'Ji, 11 is etched using an anisotropic etching method.
Figure 2 (e))
After etching the silicon nitride film 12, a film 14 is formed on the silicon semiconductor substrate 11 by a thermal modification method.
(f)).

As explained above, according to the present invention, silicon semiconductor 1
Since the boundary between the first surface and the isolation trench has a curvature, the stress applied to the i-2 part during the thermal oxidation process after the isolation trench is formed is reduced, causing deterioration of device characteristics and defects due to strain. Element defects due to the occurrence of this can be suppressed. As a result, the distance between the isolation trench and the element can be reduced, making it possible to achieve high integration.

[Brief explanation of the drawing]

Figures 1 (A) to (d) are cross-sectional views showing the conventional manufacturing method, and Figures 2 (a) to (f) are process cross-sectional views showing the manufacturing method according to the present invention. It is. In the figure, 1, 11...Silicon/semiconductor substrate, 2...Silicon dioxide film by CVD method, 1
2... Nitrogen silicon film, 3.13.14...
・Silicon dioxide film.

Claims (1)

[Claims] A step of forming a silicon nitride film on a silicon semiconductor substrate, a step of selectively etching the silicon nitride film, and a step of selectively oxidizing the silicon semiconductor substrate in the etched portion of the silicon nitride film to form silicon dioxide. a step of forming a film, a step of removing the silicon dioxide film, and a step of etching the silicon semiconductor substrate by an anisotropic etching method using the silicon nitride film as a mask to form an insulating isolation groove. A method for manufacturing a semiconductor device, characterized in that: