JPH11163118A - Manufacture of semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form such an STI structure such that a plurality of insulating films are embedded in a trench and the trench section has no step in it. SOLUTION: After a trench has been formed into a semiconductor substrate 10, a first silicon oxide film 12 is formed halfway in the trench. Then a silicon nitride film 14 is formed on the surface of the silicon oxide film 12 and the remaining internal surface of the trench, and a second silicon oxide film 15 is formed so that the film 15 is embedded in the recessed section of the silicon nitride film 14. After the second silicon oxide film 15 has been formed, the surface of the substrate 10 is exposed by etching the silicon nitride film 14 by the use of the film 15 as a mask, and then the second silicon oxide film 15 is removed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device having an STI (Shallow Trench Isolation) structure for isolating an element region.

[0002]

2. Description of the Related Art LOCOS element isolation is used to isolate elements formed in a semiconductor, and the area of the element isolation region occupies more than half of a chip.
In order to reduce the area of the element isolation region, adoption of an STI structure having a small occupied area has been studied.

The STI structure is formed by embedding an insulating film in a trench formed in an element isolation region of a substrate. A silicon oxide film is used as an insulating film to be embedded in the trench. However, in a normal manufacturing process, a process of forming a silicon oxide film as a protective film on the substrate surface and etching the silicon oxide film many times is performed. There is a problem that the film is etched and the film is reduced.

[0004] In order to prevent the silicon oxide film in the trench from being reduced in thickness, an STI in which a plurality of insulating films are formed in the trench is formed.
A method of manufacturing the structure is disclosed in Japanese Patent Application Laid-Open No. 8-227938. FIG. 2 shows a method of manufacturing the STI structure.
This will be described with reference to FIG. First, as shown in FIG.
After a silicon oxide film 21 is buried and formed halfway in a trench formed in an element isolation region of a semiconductor substrate 20, a silicon nitride film 22 is deposited on the entire surface. And FIG.
As shown in (b), the silicon nitride film 22 is polished by the CMP method to remove the silicon nitride film on the semiconductor substrate 20, and a plurality of insulating films are formed in the trench.

With this structure, the silicon oxide film is selectively etched in the step of etching the protective film made of the silicon oxide film, so that the silicon nitride film formed on the uppermost layer in the trench is not etched. There is no loss of the insulating film in the trench. However, when the width of the element isolation region is large, there is a problem that dishing occurs and a step occurs when the silicon nitride film is polished by the CMP method.

[0006]

As described above, when forming an STI structure in which a plurality of insulating films are formed in a trench, in the case of a device isolation region having a wide width, the uppermost insulating film is formed by a CMP method. There is a problem that dishing occurs when polishing is performed by using, and a step is generated. An object of the present invention is to provide a method of manufacturing a semiconductor device in which a step does not occur in an element isolation region when an STI structure including a plurality of insulating films is formed.

[0007]

Means for Solving the Problems [Configuration] The present invention is configured as follows to achieve the above object. (1) The present invention (Claim 1) is a method for manufacturing a semiconductor device including an element isolation region for isolating an element formed on a semiconductor substrate, the method comprising: forming a groove in the semiconductor substrate;
A step of burying and forming a first insulating film halfway in the groove of the semiconductor substrate, and a step of forming a second insulating film having a concave portion above the groove on the entire surface of the semiconductor substrate and the groove; Forming a stopper film in the recess of the second insulating film, etching the second insulating film using the stopper film as a mask, exposing the semiconductor substrate surface, and removing the stopper film And characterized in that:

A preferred embodiment of the present invention will be described below.
In the step of forming a second insulating film having a concave portion over the entire surface, the second insulating film is formed such that the height of the surface of the second insulating film at the bottom of the groove is substantially equal to the surface of the substrate.

The first insulating film and the stopper film are silicon oxide films, and the second insulating film is a silicon nitride film. [Operation] By forming a second insulating film having a concave portion on the first insulating film in the trench, a stopper film serving as a mask can be buried in the concave portion in a self-aligned manner. Then, using the stopper film as a mask, the second
By etching the insulating film of step S
A TI structure can be formed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process sectional view showing a manufacturing process of an STI structure according to one embodiment of the present invention.

First, as shown in FIG. 1A, after a trench is formed in a silicon substrate 10, a thin first thermal oxide film 11 is formed on the surface of the silicon substrate 10 exposed by thermal oxidation. Next, a first silicon oxide film (first insulating film) 12 is deposited on the entire surface by a chemical vapor deposition method. Then, the first thermal oxide film 11 and the first silicon oxide film 12
Is etched, and a silicon oxide film 12 is buried partially in the trench. At this time, the silicon oxide film 12 is deposited on the substrate 10 by the predetermined thickness of the silicon nitride film to be deposited later.
Lower than the surface.

Next, as shown in FIG. 1B, after a thin second thermal oxide film 13 is formed on the exposed surface of the substrate 10 by thermal oxidation, the entire surface is formed by chemical vapor deposition. A silicon nitride film (second insulating film) 14 is deposited. At this time, the recess is formed above the first silicon oxide film 12 in the trench. It is desirable that the surface of the silicon nitride film 14 in the trench is equal to the surface of the substrate 10, but not necessarily. Then, a second silicon oxide film (stopper film) 1 is formed on the entire surface by a chemical vapor deposition method.
5 is deposited.

Next, as shown in FIG. 1C, the second silicon oxide film 15 is etched using reactive ion etching, a CMP method or the like under conditions that the silicon nitride mask 14 is not etched. An oxide film 15 is buried in the recess of the silicon nitride film 14 and formed. At this time, the second silicon oxide film 15 may be etched slightly over the surface of the silicon nitride film 14, and it is sufficient that the second silicon oxide film 15 remains as a mask in a later step.

Next, as shown in FIG. 1D, using the second silicon oxide film 15 as a mask, the silicon nitride film 1 is formed.
4 is etched so that the surface of the silicon nitride film 14 is
Make it almost the same as the zero surface.

Next, as shown in FIG. 1E, the second silicon oxide film 15 used as a mask material is etched by wet etching or the like. As described above, according to the present embodiment, the silicon nitride film 14 can be embedded only in the element isolation region in a self-aligned manner. And
Since the CMP method is not used, dishing does not occur and no step occurs.

The present invention is not limited to the above embodiment. For example, a material other than a silicon nitride film can be used for the second insulating film. In the above embodiment, the first insulating film and the stopper film are the same, but different materials may be used. Further, the stopper film does not need to be an insulator, and a conductor or a semiconductor can be used as long as the material functions as a mask when the second insulating film is selectively etched. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0017]

As described above, according to the present invention, a second insulating film having a concave portion on a first insulating film in a trench is formed by embedding a stopper film in the concave portion, and the stopper film is formed. By etching the second insulating film as a mask, an STI structure without a step can be formed. Further, the stopper film serving as a mask can be formed in a self-aligned manner by burying the stopper film in the concave portion of the second insulating film without requiring a lithography step.

[Brief description of the drawings]

FIG. 1 is a process sectional view showing a manufacturing process of a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing a manufacturing process of a conventional STI structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Silicon substrate 11 ... 1st thermal oxide film 12 ... 1st silicon oxide film (1st insulating film) 13 ... 2nd thermal oxide film 14 ... Silicon nitride film (2nd insulating film) 15 ... 2 Silicon oxide film (stopper film)

Claims (3)

[Claims] 1. A method of manufacturing a semiconductor device including an element isolation region for isolating an element formed on a semiconductor substrate, comprising: forming a groove in the semiconductor substrate; Forming a second insulating film having a concave portion above the groove on the entire surface of the semiconductor substrate and the groove; and forming a stopper in the concave portion of the second insulating film. A semiconductor device comprising: a step of burying a film; a step of exposing a surface of the semiconductor substrate by etching a second insulating film using the stopper film as a mask; and a step of removing the stopper film. Manufacturing method. 2. The step of forming a second insulating film, wherein the height of the surface of the second insulating film at the bottom of the groove is substantially equal to the surface of the semiconductor substrate. A method for manufacturing a semiconductor device according to claim 1. 3. The method according to claim 1, wherein the first insulating film and the stopper film are silicon oxide films, and the second insulating film is a silicon nitride film.