JPS61268038A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form an element isolation region having fine and high-performance element isolation characteristics, and to improve the degree of integration of an element by shaping a non-oxidizable mask onto the surface of a substrate except a groove shaped to the semiconductor substrate, oxidizing a semiconductor film used for burying the groove and changing the semiconductor film into an insulating film. CONSTITUTION:An silicon oxide film 2 and an silicon nitride film 3 are formed onto an silicon semiconductor substrate 1, and sections up to some depth of the nitride film 3, the oxide film 2 and the semiconductor substrate 1 are removed while using a photo-resist 4 as a mask, thus shaping a groove 7. The photo-resist 4 is removed, a silicon oxide film 8 is formed onto the surface of the nitride film 3 and the inner surface of the groove 7, and a polycrystalline silicon film 9 is shaped and the polycrystalline silicon film 9 is oxidized and converted into the silicon oxide film 8. The polycrystalline silicon film 9 is turned into the oxide film 8 up to a level where the nitride film 3 is formed at that time. When the oxide film 8 is removed through etching and the silicon nitride film 3 and the silicon oxide film 2 are removed, the groove 7 is buried completely with the silicon oxide film 8 and the polycrystalline silicon film 9, thus forming an element isolation region.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a semiconductor device, and particularly to a method for forming an element isolation structure on a silicon semiconductor substrate.

[Conventional technology]

A conventional method for forming an element isolation structure in a semiconductor device using a single selective oxidation method will be described with reference to FIGS. 92(a) to 92(c).

That is, in this conventional method, first, an underlying silicon thickening film (
2) A silicon nitride film +31, which serves as an oxidation-resistant mask during selective oxidation, is sequentially formed, and a photoresist mask (41 is used as an etching-resistant mask) formed by photolithography to separate the elements of this silicon nitride III t3+. For example, if the conductivity type of the silicon semiconductor substrate (1) is p-type, the silicon semiconductor is etched by selectively etching away the formation region and using the photoresist mask (4) as a mask for ion implantation. A p-type impurity such as boron is ion-implanted into the substrate (1) to form an impurity implantation layer +51 which will later become a channel cut region [FIG. 2(a)].

Next, by selectively oxidizing using the silicon nitride film (3) as a mask, a silicon oxide film (61 ft) for element isolation is formed in the element isolation region [Fig. 2 (bl)]. , the silicon nitride film 131 and the underlying silicon/oxide film (2) on these element forming regions are removed to expose the substrate surface in the same portions [FIG. 2(C)],
In this way, the element isolation layer is formed.

[Problem that the invention seeks to solve]

However, in the element isolation structure according to the conventional method, as is clear from FIG. 2(C), during selective intoxication treatment, the oxidation-resistant mask is From the pattern edge of a certain silicon nitride film (3), the element isolation silicon oxide film (6) largely digs into the element formation area, narrowing the element formation area.
There was a problem in improving the degree of device integration.

This invention aims to improve the drawbacks of conventional methods, and provides a semiconductor device manufacturing method that forms a fine device isolation region with high-performance device isolation characteristics and enables an improvement in device integration. It is not intended to provide.

[Means for solving problems]

In the method for manufacturing a semiconductor device according to the present invention, an oxidation-resistant mask is formed on the substrate surface other than the groove formed in the semiconductor substrate, and the semiconductor film used for filling the groove is oxidized and converted into an insulating film. The silicon trench is easily filled with an insulating film and used as an element isolation layer.

[Effect]

In the method of this invention, an oxidation-resistant mask is formed only on the flat portion of the semiconductor substrate, and an insulating film and a semiconductor film are formed on the surface of the semiconductor substrate including the groove portion, and this semiconductor film is applied to at least the portion on the flat portion of the substrate. By oxidizing to such an extent that the entire structure is oxidized to form an insulating film, it is possible to form a flat element isolation region without creating a void in the trench.

[Embodiments of the invention]

Hereinafter, a practical example of the method for manufacturing a semiconductor device according to the present invention will be explained with reference to FIGS. 1(a) to 1(f).

In this embodiment method, first, on a silicon semiconductor substrate (II), an underlying silicon oxide film (2) and a silicon nitride film (31) which will serve as a oxidation-resistant mask in the subsequent process are sequentially formed, and this silicon nitride film 13+ A 7-photoresist mask (41) formed on the top by photolithography is used as an etching-resistant mask to form a silicon nitride film (3I) in the element isolation formation region, a silicon oxide film (2), and a silicon semiconductor substrate [1] at a certain depth. The grooves are selectively etched away to form grooves ( ) [FIG. 1(a)].

Next, the photoresist mask (41yk) is removed, and if necessary, the silicon semiconductor substrate (
An impurity implanted layer (51) is formed by diffusing an impurity having the same conductivity as in 1).Furthermore, an insulating film, for example, a silicon oxide film (8) is formed on the surface of the silicon nitride film (31 and the inner surface of the groove j7). Further, a semiconductor film, for example, a polycrystalline silicon film 1914-groove (7) is formed on this silicon oxide film (8).
) is completely embedded [Figure 1 (bD
.

Furthermore, a polycrystalline silicon film (9
1 is oxidized in an oxidizing atmosphere and converted into a silicon oxide film (8). At this time, since the silicon nitride film +31, which is a t-1 oxidation-resistant film, is formed on the element formation region, the element formation region is maintained without any influence even if the oxidation treatment is performed. The oxidation progresses to the depth of the polycrystalline silicon film (91ij) formed on the silicon oxide film (81ij).
), and the polycrystalline silicon film (91) is converted to a silicon oxide film (8) to the level where the silicon nitride film (3) is formed [FIG. 1(C)].Next,
After removing the silicon oxide film (8) by etching until the surface of the silicon nitride film (3) is exposed [see button in Figure 1], and removing the silicon nitride film (3j) and the underlying silicon oxide film (2), a groove (7) is formed. is completely buried with a silicon oxide film (8) and a polycrystalline silicon film (91) to form an element isolation region [FIG. 1(e)].

Further, in the above embodiment, the oxidation of the polycrystalline silicon film (9) is stopped midway, and the trench (7) is surrounded by the silicon oxide film (8).
It is also possible to completely convert 1 to a silicon oxide film.

〔Effect of the invention〕

As described above, in this invention, a trench formed in a semiconductor substrate is filled with an insulating film and a semiconductor film, so the trench can be filled without any voids, and the semiconductor film can be oxidized by the oxidation-resistant film formed on the flat part. Even if the device is separated, it does not adversely affect the device formation region (it is possible to form a fine device isolation region, and it is possible to achieve flat isolation).

[Brief explanation of drawings]

FIGS. 1(a-1f) are cross-sectional views showing one embodiment of the present invention, and FIGS. 2(a)-(c) are cross-sectional views showing the main stages of forming an element isolation region in a conventional semiconductor device manufacturing method. In the figure, fil is a semiconductor substrate, (3) is a silicon nitride film as an oxidation-resistant film, (6) is an impurity diffusion layer, and (7) is a silicon nitride film as an oxidation-resistant film.
) trench, +81 I/f insulating film, such as a silicon oxide film, (91 is a semiconductor film, such as a polycrystalline silicon film. Note that the same reference numeral J8 in each figure indicates the same or a corresponding portion.

Claims (3)

[Claims] (1) A first step of forming an oxidation-resistant film having an opening in an element isolation formation region on a semiconductor substrate; a second step of forming a groove in the semiconductor substrate using this oxidation-resistant film as an etching mask; a third step of sequentially forming an insulating film and a semiconductor film on the surface of the oxidation-resistant film on the semiconductor substrate including the inside of the groove; oxidizing the semiconductor film;
a fourth step of converting at least all of the semiconductor film on the flat upper surface of the semiconductor substrate into an insulating film, and removing the insulating film and the oxidation-resistant film on the flat upper surface of the semiconductor substrate, A method of manufacturing a semiconductor device, comprising a fifth step of exposing a flat upper surface of the substrate and leaving an element isolation insulating layer in the groove. (2) A patent characterized in that the insulating film and the semiconductor film in the third step are formed after diffusing impurities of the same conductivity type as that of the semiconductor substrate into at least a portion of the semiconductor substrate on the inner surface of the groove. A method for manufacturing a semiconductor device according to claim 1. (3) A silicon single crystal semiconductor substrate as a semiconductor substrate,
A method for manufacturing a semiconductor device according to claim 1 or 2, characterized in that a silicon nitride film is used as the oxidation-resistant film, a silicon oxide film is used as the insulating film, and a polycrystalline silicon film is used as the semiconductor film. .