JPS62145833A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To prevent conductive layers from shortcircuiting by preventing the conductive layers and an interlayer insulating film from being disconnected in an element separating region. CONSTITUTION:Silicon nitride film 8 are formed on the side walls of a silicon nitride film 4 and a polycrystalline silicon layer 3, and a boundary between the film 4 and the layer 3 is not exposed. Accordingly, when forming a field oxide film 10, the films 8 prevent a boundary between the film 4 and the film 3 from oxidizing as a protector and also prevent the ends of the polycrystalline silicon layer from being oxidized. Thus, the film 10 can be formed without a projecting shape to prevent the conductive layers and an interlayer insulating film formed on the film 10 from being disconnected and to also prevent the conductive layers from being disconnected and between the conductive layers from being shortcircuited.

Description

[Detailed description of the invention] [Technical field of invention] The present invention relates to a method for manufacturing a semiconductor device.

[Technical front of the invention and its problems]

A conventional MOS LSI element isolation technique will be explained with reference to FIG. a silicon oxide film 2 on a semiconductor substrate 1;
A polycrystalline silicon layer 3, a silicon nitride film 4, and a polycrystalline silicon layer 5 are sequentially formed (FIG. 2(a)).

Next, after applying a resist 6 to the entire surface, a portion of the surface of the polycrystalline silicon layer 5 and silicon nitride film 4 at a predetermined location is etched by photolithography (FIG. 2(b)). After removing the remaining resist 6, the polycrystalline silicon layer 5 is oxidized to form a silicon oxide film 7 (FIG. 2(C)).

Using this silicon oxide film 7 as a mask, parts of the surfaces of silicon nitride film 4 and polycrystalline silicon layer 3 are etched by anisotropic etching. Then, the silicon oxide film 7 is removed (FIG. 2(d)).

Next, the surfaces of polycrystalline silicon layer 3 and semiconductor substrate 1 are oxidized by wet oxidation to form field oxide film 11. This bulge of the field oxide film 11 lifts up the ends of the adjacent polycrystalline silicon layer 3 and silicon nitride film 4 (FIG. 2(e)).

Thereafter, the silicon nitride film 4 and the polycrystalline silicon layer 3 are removed (FIG. 2(f)). In this way, element isolation is performed on the field oxide film 11 in rows 2Z.

However, in the above conventional device isolation technology, when forming field oxide 1111 by wet oxidation, protrusions appear at the interface between polycrystalline silicon layer 3 and silicon nitride film 4, as shown in A of FIG. 2(e). part occurs.

This is considered to be because the interface is more easily oxidized than the other interfaces depending on the adhesion between the polycrystalline 99712 layer 3 and the silicon nitride film 4 and the film quality of each of the polycrystalline silicon layer 3 and the silicon nitride film. And Figure 2 (f
) The field oxide film 11 having an overhanging protrusion as shown in part 8 of this field oxide film 11 is
When a conductive layer and an interlayer insulating film are formed on the conductive layer, the conductive body may be disconnected, or the interlayer insulating film may be disconnected in the same manner as the conductive layer, causing a short circuit between the 41ffi layer and the conductive layer. There was a problem with letting people do things.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a semiconductor device in which an element isolation region is formed in which a conductive layer and an interlayer insulating film are not cut.

[Summary of the invention]

A method for manufacturing a semiconductor device according to the present invention includes the steps of sequentially forming a silicon oxide film, a polycrystalline silicon layer, and a first silicon nitride film on a semiconductor substrate, and forming a first silicon nitride film and a polycrystalline silicon film at predetermined locations. A step of etching a part of the crystalline silicon body and forming a second silicon nitride film on the entire surface,
A step of leaving the second silicon nitride film only on the first silicon nitride film and the side wall of the polycrystalline silicon body by anisotropic etching, and etching the remaining second silicon nitride film and first silicon nitride film with oxidation resistance. This method includes a process of forming a field oxide film by wet oxidizing the polycrystalline silicon layer and the semiconductor substrate as a chemical mask, and prevents the field oxide film used for element isolation from having a protrusion shape. .

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 shows an embodiment of a method for manufacturing a semiconductor device. First, a silicon oxide film 2 with a thickness of 500 to 1000 wafers is formed by thermal oxidation on a semiconductor substrate 1 made of, for example, a p-type silicon substrate, and then a CVD (C
chemical vapor mouth position)
Polycrystalline silicon layer 3 with a thickness of 500 to 1500
Deposit. Subsequently, CVD is performed on this polycrystalline silicon layer 3.
Silicon nitride film with a film thickness of 100° to 2000° by method 4
After depositing this silicon nitride film 4. Hini CV
A polycrystalline silicon layer 5 is deposited to a thickness of 500 to 1500 using the D method (FIG. 1(a)).

Next, after coating the entire surface with resist 6, the resist 6 at predetermined locations is removed by photolithography, and the remaining resist 6 is removed.
Using this as a mask, a portion of the surfaces of the polycrystalline silicon layer 5 and silicon nitride film 4 are etched (FIG. 1(b)). After removing the remaining resist 6, the polycrystalline silicon layer 5 is oxidized by wet oxidation to a film thickness of 8,000 to 15,000.
A silicon oxide film 7 is formed (FIG. 1(C)). Using this silicon oxide film 7 as a mask, anisotropic etching is performed to etch the remaining part of the silicon nitride film 4 whose surface has already been partially etched and a part of the surface of the polycrystalline silicon layer 3. And silicon oxide film 7 as a mask
(Fig. 1(d)).

Next, a silicon nitride film 8 is deposited to a thickness of 500 to 2,000 layers over the entire surface by the CVU' method (FIG. 1(e)). Then, by anisotropic etching, the silicon nitride film 8 deposited on the side walls of the silicon nitride film 4 and the polycrystalline silicon layer 3 is left, and the silicon nitride film 8 on other parts is removed. The remaining silicon nitride film 8 and silicon nitride film 4 are combined to form a silicon nitride film 9 (FIG. 1(f)).

Next, using the silicon nitride film 9 as a blocking mask, ions of n-type impurities such as boron are implanted into the surface of the semiconductor substrate 1 to perform an inversion prevention process (not shown).

Next, wet oxidation is performed using the silicon nitride film 9 as an acid-resistant bamboo mask to oxidize the polycrystalline silicon layer 3 and the semiconductor substrate 1 to form a field oxide film 10 having a thickness of 6,000 to 10,000.

At this time, the edges of the adjacent polycrystalline silicon layer 3 and silicon nitride film 4 are lifted by the bulge of the field oxide film 10 (FIG. 1(q)). Thereafter, the silicon nitride film 9 and the polycrystalline silicon layer 3 are removed (FIG. 1(b)).

In this way, Field Oxidation II! Element isolation is performed by 110.

Thereafter, according to a conventional method, MOS l-transistors and the like are formed in the element regions separated by field oxidation 11110, and conductive layers and the like are further formed to manufacture a semiconductor device.

According to this embodiment, the silicon nitride film 8 is formed on the sidewalls of the silicon nitride film 4 and the polycrystalline silicon layer 3, and the interface between the silicon nitride film 4 and the polycrystalline silicon layer 3 is not exposed. In, field oxidation i! When forming the polycrystalline silicon layer 10, the silicon nitride film 8 acts as a protector to prevent oxidation at the interface between the silicon nitride film 4 and the polycrystalline silicon layer 3, and also prevents oxidation at the end of the polycrystalline silicon body. For this reason, the field oxide film 10 can be formed without having a protrusion shape, which prevents the conductive layer and the interlayer insulating film formed on the field oxide film 10 from being disconnected, and prevents disconnection of the conductive body and conductive layer. Shows 1 to 1 between the conductive layer and the conductive layer can be prevented.

Furthermore, according to this embodiment, the silicon nitride film 4 and the polycrystalline silicon layer 3 are formed with silicon nitride grooves 8 on the sidewalls, so that the conversion difference can be reduced, so that the element isolation region can be reduced. It can be made narrower, and therefore higher integration can be achieved.

Although the above embodiments have been described using an n-type silicon substrate, the present invention can also be implemented using an n-type silicon substrate. However, in that case, n-type impurities are used for ion implantation for anti-inversion processing.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to prevent the occurrence of disconnection of the conductive layer and the interlayer insulating film in the element isolation region.

[Brief explanation of drawings]

FIG. 1 is a process diagram showing a method for manufacturing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a process diagram showing a conventional WA manufacturing method for a semiconductor device. 1...Semiconductor substrate, 2.7.10.11...Silicon oxide film, 3,5...Polycrystalline silicon layer, 4,8゜9
...Silicon nitride film, 6...Resist.

Claims (1)

[Scope of Claims] A first step of sequentially forming a first silicon oxide film, a first polycrystalline silicon layer, a first silicon nitride film, and a second polycrystalline silicon layer on a semiconductor substrate; a second step of sequentially etching the second polycrystalline silicon layer and a part of the first silicon nitride film surface at the location by photolithography, and oxidizing the second polycrystalline silicon layer, a third layer forming a second silicon oxide film;
a fourth step of etching a part of the surface of the first silicon nitride film and the first polycrystalline silicon layer using the second silicon oxide film as a mask; and etching a second silicon nitride film over the entire surface. a fifth step of forming a film and leaving the second silicon nitride film only on the first silicon nitride film and the side wall portion of the first polycrystalline silicon body by anisotropic etching; a sixth step of wet-oxidizing the first polycrystalline silicon layer and the semiconductor substrate using the second silicon nitride film and the first silicon nitride film as an oxidation-resistant mask to form a field oxide film; A method for manufacturing a semiconductor device, comprising: