JPS63152155A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To reduce an element isolation region and simultaneously prevent generation of damage in a substrate, by performing selective oxidation after forming the offset of an Si3N4 film wherein an SiO thin film is formed for an Si substrate. CONSTITUTION:An SiO2 12, and Si3N4 13 and an SiO2 14 are stacked on a P-type Si substrate 11. A mask is formed, RIE is performed, an SiO2 thin film 15 is arranged, and an Si3N4 thin film 16 and an SiO2 film 17 are deposited. Then a sidewall 17' of SiO2 is formed by RIE, and the Si3N4 16 and the SiO2 15 are eliminated by etching. The SiO2 14 and the sidewall 17' are subjected to wet etching, and an offset 16' of the Si3N4 film is formed. Thus an offset of Si3N4 is formed which has the SiO2 thin film 15 as a buffer layer arround a prearranged element isolation region. After a P-type inversion protection layer 18 is formed by implanting ions, a field oxide film 19 is formed by wet oxidation. By this constitution, the element isolation region can be reduced, and damages do not generate in the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming a fine element isolation region by selective oxidation. More specifically, the present invention relates to an improvement in a method for forming an element isolation region in which an offset If made of a silicon nitride film is provided to suppress the extension of a bird's beak.

<Prior Art> FIGS. 2(a) to 2(e) are sectional views showing all the main process steps of a conventional manufacturing method.

After forming a thermal oxide film 2 on a silicon substrate 1, a silicon nitride film 3 and a silicon oxide film 4 are sequentially deposited, and by mask formation and reactive ion etching, the thermal oxide film 2 and silicon Nitride film 3, silicon oxide film 4
A pattern is formed (FIG. 2(a)). Subsequently, a thin silicon nitride film 5 and a silicon oxide film 6'f are deposited (
Figure 2(b)). A silicon oxide film sidewall 6 is formed around the planned device area by reactive ion etching.
Then, the silicon nitride film 5 is etched on the sidewall 6' and the silicon oxide film 4 as a mask (FIG. 2(C)). The silicon oxide film 4 and the silicon oxide film sidewall 6' are removed by etching, and the silicon nitride film offset 5' is formed (FIG. 2(d)). As a result, an offset of the silicon nitride film is formed around the intended element isolation region. After that, selective oxidation is carried out in a steam atmosphere.
A field oxide film 7 is formed (FIG. 2(e)).

-<Problems to be Solved by the Invention> However, the above-mentioned conventional manufacturing method has encountered the following problems. That is, in the conventional method, the edge of the element isolation region has a steep shape, and the substrate is easily damaged.

The present invention is aimed at solving the above-mentioned problems, and forms an appropriate bird's beak while reducing the width of the element isolation region, thereby improving the shape of the edge of the element isolation region. The present invention provides a method for manufacturing a semiconductor device that is gentle and reduces the occurrence of damage.

Means for Solving Problems〉 A silicon nitride film with a thin silicon oxide film is formed on its lower surface, that is, between it and the silicon substrate, and then selective oxidation is performed to form an element isolation region. .

Effect> By forming the groove bottom as described above, an appropriate bird's beak is formed, and the shape of the edge of the element isolation region becomes gentle.

<Example> Hereinafter, the present invention will be described in detail based on examples.

FIGS. 1(a) to 1(g) are cross-sectional views showing the main process steps of an embodiment of the present invention.

First, a thermal oxide film I2 is formed on a P-type silicon substrate II, and then a silicon nitride film 13 and a silicon oxide film 14 are sequentially deposited (FIG. 1(a)). Next, mask formation,
A pattern of a thermal oxide film 12, a silicon nitride film 13, and a silicon oxide film 14 is formed on the intended device region by reactive ion etching (FIG. 1(b)). Next, a thin thermal oxide film 15 is formed, and a thin silicon nitride film 1 is formed.
6. Deposit a silicon oxide film 17 (FIG. 1(C)).

A silicon oxide film sidewall 17' is formed around the intended device area by reactive ion etching (
Figure 1(d)). Next, using the silicon oxide film sidewall 17' and the silicon oxide film 14 as masks, the silicon nitride film 16 and the thin thermal oxide film 15 are etched (
Figure 1 (e). Then, the silicon oxide film I4 and the silicon oxide film sidewall 17' are removed by wet etching, and an offset +6'4 silicon nitride film is formed (FIG. 1(f)). As a result, an offset of the silicon nitride film having the thin thermal oxide film I5 as the pack 7 layer is formed around the intended element isolation region. During the process, in the step shown in FIG. 1(e), impurities such as IIB+ are ion-implanted to prevent field inversion (18: P-type inversion prevention layer), and then selective oxidation is carried out in a steam atmosphere.
A field oxide film 19 is formed (FIG. 1(g)).

Thereafter, elements are formed in the element region surrounded by the field oxide film 19 to form a semiconductor device according to normal steps (not shown).

<Effects of the Invention> As explained in detail above, the method for manufacturing a semiconductor device of the present invention involves forming a thin silicon oxide film between a silicon substrate and then performing selective oxidation to form an element isolation region. According to the present invention, there is provided an extremely useful semiconductor device that can reduce the size of the element isolation region and at the same time prevent the occurrence of damage in the substrate. It is possible to provide a manufacturing method.

[Brief explanation of the drawing]

1(a) to (g) are cross-sectional views showing the element isolation region forming process according to the present invention in process order, and FIGS. 1(a) to (e) are cross-sectional views showing the conventional element isolation area forming process in process order. It is a diagram. Explanation of symbols: +1: P-type silicon substrate, 12: thermal oxide film, 13. silicon nitride film, 14: silicon oxide film, +5: thin thermal oxide film, 16: thin silicon nitride film, 16' rainbow IJ-con nitride film. +7: IJ con oxide film, 17':
Sidewall of silicon oxide film, 18: P-type anti-inversion layer, +9: field oxide film.

Claims (1)

[Claims] 1. After forming an offset made of silicon nitride film,
A semiconductor device manufacturing method in which a field oxide film for element isolation is formed by selective oxidation, characterized in that a thin silicon oxide film is provided between the offset and the silicon substrate. manufacturing method.