JPS6260233A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the growth of a bird's beak by a method wherein an oxide layer is formed on a semiconductor substrate to form a nitride layer on the oxide layer, which is heat-treated in an oxidizing atmosphere, and after the nitride layer is pattern-etched, a field oxide layer is formed by selective oxidation. CONSTITUTION:A base Si oxide film 2 is formed on an Si substrate 1, and thereafter, an Si nitride film 3 is grown in a decompression vaporphase growing furnace, this nitride film 3 is heat-treated in an oxidizing atmosphere of H2O, an Si oxide layer 5 is grown in a pinhole and a resist 4 is applied and is patterned in an insular region. Then, the Si nitride film 3 other than the element isolation region is etched for about 120sec in CF4+O2 plasma of 0.4Torr using the resist 4 as a mask. At this time, such a defect as the Si substrate is etched up does not generate even through the pinhole exists in the Si nitride film because of the Si oxide layer grown in the pinhole. Hereby, a bird's beak can be reduced to 0.5mum or thereabouts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a semiconductor device, and particularly to an element isolation technique for electrically insulating each element on a semiconductor substrate from each other.

[Summary of the invention]

The present invention relates to a semiconductor device manufacturing method related to element isolation technology, in which an oxide layer is formed on a semiconductor substrate, a nitride layer is formed on the oxide layer, the layer is heat-treated in an oxidizing atmosphere, and the nitride layer is After pattern etching, a field oxide layer is formed by selective oxidation to reduce bird's beaks occurring in the active region and to miniaturize the semiconductor device.

[Conventional technology]

Conventionally, a selection technique called the LOOOB method using a silicon nitride film as a mask, as described in Japanese Patent Application Laid-Open No. 47-2517, has been widely used for device isolation of MO13-LSIs and the like. This is a method of covering the active region with a silicon nitride film and forming a silicon oxide film on the field, but as the field silicon film grows, it digs into the silicon nitride film, forming a so-called bird's beak. Therefore, it was necessary to take a large dimensional margin in pattern design and manufacturing, making it difficult to stably supply integrated circuits with fine rules.

In recent years, separation techniques have been proposed that utilize the sidewalls of silicon oxide films or silicon nitride films by anisotropic etching to reduce bird's beaks. However, these inventions cannot be put into practical mass production due to many problems in process and electrical characteristics, such as crystal defects occurring during etching and excessive junction leakage and channel leakage.

On the other hand, when forming the element isolation region, bird's beak can be reduced by increasing the thickness of the silicon nitride film covering the active region and thinning the underlying silicon oxide film.

However, the O used when removing this silicon nitride film
Parallel plate plasma etching using a mixed gas of IF, 10, has an etching selectivity of silicon nitride film to silicon oxide film of 2.0 to 2.5, and eliminates defects such as pinholes that occur in silicon nitride film. Therefore, the thickness of the underlying silicon oxide film is limited to 700 to 9 oo, and the thickness of the silicon nitride film is limited to 1,500 to 16 oo, and in these structures, a bird's beak of 1.4 to 1.7 .mu.m is formed.

On the other hand, for example, the underlying silicon oxide film of 4ooH and the
In the silicon nitride film structure of 0.000, the bird's beak is reduced to about 0.05 μm.

[Problems and Objectives to be Solved by the Invention] However, the surface of the silicon substrate is etched through defects such as pinholes that occur in the silicon nitride film. As shown in FIG. 2, a base silicon oxide film 9 is formed on a silicon substrate 8.
゜A silicon nitride film 10 is applied. At this time, in order to form the silicon nitride film 10 by vapor phase growth, the pinhole 1
The generation of defects such as 2 is unavoidable. Furthermore, a resist 11 is applied and patterned into island regions (FIG. 2-α). When this is etched using a dry etcher, the underlying silicon oxide film 9 is etched through the pinhole 12.
Furthermore, the etching extends to the silicon substrate 8 and produces etch pits 13 (FIG. 2-b). After removing resist 11,
This is heat-treated in an oxidizing atmosphere to form a field oxide film 14, but defects in the silicon substrate 8 (etch bits 15)
) is located at the junction or channel portion, this causes an increase in leakage current under the field oxide film 14. To prevent this, the base silicon oxide film 9 could be made thicker and the silicon nitride film 10 thinner, but this would conflict with suppressing the growth of the bird's beak.

[Means to solve the problem]

The method for manufacturing a semiconductor device of the present invention includes forming an oxide layer on a semiconductor substrate, forming a nitride layer on the oxide layer, heat-treating this in an oxidizing atmosphere, and pattern-etching the nitride layer. After that, a field oxide layer is formed by selective oxidation.

〔Example〕

The details of the present invention will be explained below based on FIG. After forming a base silicon oxide film 2 of about 400× on a silicon substrate 1, a silicon nitride film 5 of about 200× is formed in a reduced pressure vapor phase growth furnace.
01 Grow. This was heat-treated for 20 minutes in a H, O oxidation atmosphere at 1000° C., thereby growing a silicon oxide layer 5 in the pinhole. Apply resist 4,
It was patterned into an island region (Fig. 1-α). Next, as shown in FIG. 1, using the resist 4 as a mask, the silicon nitride film 5 outside the element isolation region is coated with an OF of 0.4 Torr,
．． It was etched for about 120 seconds using a 7' lasma. At this time,
Although there were pinholes in the silicon nitride film 3,
No defects such as etching of the silicon substrate 1 were caused due to the silicon oxide grown in the pinholes. In addition, silicon oxide 5 grown in the pinhole
remained somewhat thicker than the surrounding underlying silicone enhancement film 2,
During the formation of the thick field oxide film 7 in the next process, it is almost buffered and there is no problem, and the bird's beak is also reduced to o, 5.
It was limited to about μ.

Note that this is only one embodiment of the present invention, and the same effect can be obtained by changing the oxidation conditions, such as heat-treating a silicon nitride film in which pinholes exist in a 0° atmosphere. Also, 81!6- for dry etching.
f-He or N? It is also possible to use , and in this case, the selection ratio increases, the underlying silicon oxide film can be made thinner, the silicon nitride film can be made thicker, and the bird's beak can be further reduced.

〔Effect of the invention〕

In the present invention, the structure of a thin base silicon oxide layer and a thick silicon nitride layer is achieved by performing heat treatment in an oxidizing atmosphere and filling pinholes existing in the silicon nitride layer formed on the base silicon oxide layer. This makes it possible to reduce the bird's beak to about 0.5 μm. This realizes a stable supply of semiconductor devices with fine rules.

[Brief explanation of the drawing]

Figures 1 (α) to (1) are cross-sectional views of the process of the present invention, and Figure 2 (
a) to (C) are process cross-sectional views of the prior art. 1.8...Semiconductor substrate 2.9...Base oxide layer 6.10...Nitride layer 4.11...Resist 5... ...Oxide layer 6.14...Field oxide layer 12...Pinhole 15...Etch bit or more Structure ≦\A silicon ring-, @ -1-it (Fig. 2 fight)

Claims (1)

[Claims] forming an oxide layer on a semiconductor substrate; forming a nitride layer on the oxide layer; heat-treating the nitride layer in an oxidizing atmosphere; pattern-etching the heat-treated nitride layer. A method of manufacturing a semiconductor device, comprising the step of: forming a field oxide layer by selective oxidation.