JPH07201839A - Manufacturing for semiconductor device - Google Patents

Abstract

PURPOSE:To prevent a bird's beak at an end of a device isolation oxide film, by enlarging the size of a preventive film for preventing an oxidant from diffusing when an insulating film is formed in a semiconductor device. CONSTITUTION:A semiconductor substrate 11 is thermally oxidized and a nitride film is deposited thereon. A region for forming a device isolation oxide film is exposed and developed to remove a resist. An oxide film 12 and a nitride film 13 are formed in an anisotropic dry etching step. The substrate 11 is isotropically dry-etched to remove the photoresist. After an oxide film 14 is formed in a thermal oxidation step, a nitride film 15 and a nitride film 16 are deposited. A photoresist with a tapered shape is embedded in a space between the nitride film 15 and the nitride film 16. Then, part of the nitride film 15 and the oxide film 14 is removed in an anisotropic dry etching step, and a frame oxide film 18, a nitride film 9, and a base oxide film 20 are formed. The substrate 11 is thermally oxidized to form a device isolation oxide film 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device which is an integrated circuit element having a fine size in which an active region of a transistor is isolated by an insulating film.

[0002]

2. Description of the Related Art In recent years, semiconductor devices have been highly integrated and highly functionalized due to advances in fine processing techniques such as photolithography and dry etching. As a method of manufacturing a semiconductor device, a method of isolating an active region of a transistor with an insulating film is mainly used.

However, as the degree of integration of semiconductor devices increases, the dimensional margin of the insulating film separating the active region of the transistor from each other is becoming smaller. The bird's beak generated at the edge of the element isolation region when forming an insulating film that isolates the active region of the transistor from each other reduces the width of the active region of the transistor and hinders high integration of the semiconductor device. Therefore, it is important to establish a device isolation formation method in which bird's beak does not occur.

An example of a conventional method for manufacturing the above-described semiconductor device will be described below with reference to the drawings.

FIG. 2 is a device isolation process flow chart of a conventional semiconductor device manufacturing method. In FIG. 2, 1 is a semiconductor substrate, 2 is a buffer oxide film, and 3 is a nitride film. Reference numeral 4 is a buffer oxide film, and 5 and 6 are nitride films. 7 is a frame made of an oxide film, 8 is a frame made of a nitride film, 9
Is an underlying oxide film. Reference numeral 10 is an element isolation oxide film.

First, the semiconductor substrate 1 is thermally oxidized to form an oxide film. A nitride film is deposited on it. Further, a photoresist is applied, and exposure and development are performed so that the photoresist does not remain only in the portion to be the element isolation region.
The nitride film and the oxide film are removed by anisotropic dry etching, leaving the oxide film 2 and the nitride film 3. The semiconductor substrate 1 is removed by isotropic dry etching to form a dug. After this, the photoresist is removed. Furthermore, after the semiconductor substrate 1 is thermally oxidized to form an oxide film, the oxide film is removed by wet etching, and the crystal defects of the semiconductor substrate 1 caused by dry etching are removed (FIG. 2A).

Next, the semiconductor substrate 1 is thermally oxidized to form an oxide film 4
To form. A nitride film is deposited thereon to form nitride films 5, 6
Are formed (FIG. 2B).

Next, using the nitride film 6 as an etching mask, a part of the nitride film 5 and the oxide film 4 is removed by anisotropic dry etching to form a frame composed of the oxide films 7 and 8 and a base oxide film 9. (FIG. 2C).

Next, the element isolation oxide film 10 is formed by thermal oxidation (FIG. 2D).

[0010]

However, in the above structure, since the nitride film 6 is used as an etching mask for the nitride film 8 by anisotropic dry etching, the nitride film 6 continues to be etched. The nitride film 8 is etched, and the frame length of the nitride film 8 is shortened. That is,
The nitride film 6 only gains time until the nitride film 8 is etched. The nitride film 6 is used as an etching mask for the nitride film 8, but since it is a film made of the same material,
It has no effect as an etching mask. Therefore, it is necessary to newly provide an etching mask for the nitride film 8.

The mechanism by which bird's beaks are generated at the edges of the element isolation oxide film 10 is as follows. Nitride film 8
Has the function of preventing the oxidant from diffusing. If the length of the nitride film 8 becomes shorter, the distance from the end of the nitride film 8 to the end of the element isolation oxide film 10 becomes shorter. Therefore, the amount of the oxidant reaching the end of the element isolation oxide film 10 is increased as compared with before the length of the nitride film 8 is shortened. As a result, the edge of the element isolation oxide film 10 is more oxidized than before the length of the nitride film 8 is shortened, and bird's beak is likely to occur.

Therefore, in order to reduce the occurrence of bird's beak, the nitride film 8 (oxidant diffusion blocking film) may be formed long.

Therefore, for the reasons given above, FIG.
There is a problem that bird's beaks are likely to occur at the edges of the element isolation oxide film 10 when thermally oxidized in (d).

In view of the above problems, the present invention provides a method of manufacturing a semiconductor device in which bird's beak is unlikely to occur at the edge of an element isolation oxide film.

[0015]

In order to solve the above problems, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming a first insulating film on a semiconductor substrate, and an isotropic method using the insulating film as a mask. Of etching the semiconductor substrate by anisotropic dry etching, forming a second insulating film on the semiconductor substrate, applying a resist to the entire surface of the semiconductor substrate, and forming an eaves by the isotropic dry etching. A step of filling the resist with a resist, a step of etching a part of the second insulating film and the first insulating film by anisotropic dry etching, and a step of removing the resist,
An element isolation insulating film is formed on the semiconductor substrate.

[0016]

According to the present invention, when the nitride film frame having the above-mentioned structure is formed,
The nitride film frame (oxidant diffusion blocking film) does not recede. Further, since a frame length equal to or larger than the etching mask size of the nitride film can be arbitrarily obtained, bird's beak is less likely to occur at the end of the element isolation oxide film when the insulating film is formed by thermal oxidation.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device manufacturing method according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a flow chart of an element isolation process of a method of manufacturing a semiconductor device according to an embodiment of the present invention. In FIG. 1, 11 is a semiconductor substrate, 12 is a buffer oxide film, and 13 is a nitride film. 14 is a buffer oxide film, 1
Reference numerals 5 and 16 are nitride films, and 17 is a buried resist layer.
Reference numeral 18 is a frame formed of an oxide film, 19 is a frame formed of a nitride film, and 20 is a base oxide film. Reference numeral 21 is an element isolation oxide film.

The difference from FIG. 2 is that a buried resist layer 17 is provided in the space between the nitride film 19 which is a frame and the nitride film 16 which is an etching mask.

First, the semiconductor substrate 11 is thermally oxidized to a film thickness of 5
An oxide film of 0 nm is formed. A 120 nm-thickness nitride film is deposited thereon by low pressure CVD. Photoresist is applied, and exposure and development are performed so that the photoresist does not remain only in the portion where the element isolation region is formed.

Next, the nitride film and the oxide film are removed by anisotropic dry etching to remove the oxide film 12 and the nitride film 1.
Leave 3 Next, the semiconductor substrate 11 is removed by 380 nm by isotropic dry etching, and then the photoresist is removed. Next, the semiconductor substrate 11 is thermally oxidized to a film thickness of 200 nm.
After the oxide film is formed, the oxide film is removed by wet etching, and the crystal defects of the semiconductor substrate 11 caused by dry etching are removed (FIG. 1A).

Next, the semiconductor substrate 11 is thermally oxidized to a film thickness of 4
An oxide film 14 of 0 nm is formed. On top of that, low pressure CVD
Thus, a nitride film 15 having a film thickness of 40 nm and a nitride film 16 having a film thickness of 40 nm are formed. Next, a photoresist is applied to the entire surface of the semiconductor device to fill the space surrounded by the nitride film 15 and the nitride film 16. When the entire surface is exposed by using the nitride film 16 as an exposure mask and developed, the resist remains only in the space (overhang) surrounded by the nitride film 15 and the nitride film 16, and a buried resist layer 17 having a taper is formed (FIG. 1
(B)).

Using the nitride film 16 as an etching mask, a portion of the nitride film 15 and the oxide film 14 of about 10 to 20 nm is removed by anisotropic dry etching, and a frame composed of the oxide film 18 and the nitride film 19 and an underlying oxide film. 20 is formed (FIG. 1C).

Next, thermal oxidation is performed to obtain a film thickness of 1000.
A device isolation oxide film 21 having a thickness of nm is formed (FIG. 1D).

As described above, according to this embodiment, a positive photoresist is applied to the entire surface before forming a frame composed of the oxide film 18 and the nitride film 19 by dry etching to form the frame of the nitride film 19. A photoresist is formed in a self-aligning manner in a space between the nitride films 16 which are etching masks, and the photoresist shape after development has a configuration having a taper.

In this embodiment, after the nitride film 19 which is a frame is formed by the above-described structure, the nitride film 19 (oxidant diffusion blocking film) which is a frame does not recede, and the nitride film 19 which is an etching mask is formed. Since it is possible to arbitrarily obtain a frame length equal to or larger than the dimension, it is possible to suppress generation of bird's beaks at the ends of the element isolation oxide film when the insulating film is formed by thermal oxidation.

[0027]

As described above, according to the present invention, by providing a buried resist layer having a taper in a space between a nitride film which is an oxidant diffusion blocking film and a nitride film which is an etching mask in a self-aligning manner, Since the diffusion blocking film does not recede and the frame length longer than the etching mask size can be obtained arbitrarily, it is possible to suppress the occurrence of bird's beaks at the edges of the element isolation oxide film when the insulating film is formed by thermal oxidation. be able to.

[Brief description of drawings]

FIG. 1 is a process flow chart of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a process flow diagram of a conventional semiconductor device manufacturing method.

[Explanation of symbols]

 1 Semiconductor Substrate 2 Buffer Oxide Film 3 Nitride Film 4 Buffer Oxide Film 5,6 Nitride Film 7 Frame Made of Oxide Film 8 Frame Made of Nitride Film 9 Base Oxide Film 10 Element Isolation Oxide Film 11 Semiconductor Substrate 12 Buffer Oxidation Film Film 13 Nitride film 14 Buffer oxide film 15, 16 Nitride film 17 Embedded resist layer 18 Frame formed of oxide film 19 Frame formed of nitride film 20 Base oxide film 21 Element isolation oxide film

Claims (1)

[Claims] 1. A step of forming a first insulating film on a semiconductor substrate, a step of etching the semiconductor substrate by isotropic dry etching using the insulating film as a mask, and a second step of forming the second insulating film on the semiconductor substrate. After forming an insulating film, a step of applying a resist on the entire surface of the semiconductor substrate and filling the resist in a canopy formed by the isotropic dry etching; and a step of anisotropically etching the second insulating film. Etching a portion of the first insulating film,
A method of manufacturing a semiconductor device, comprising: removing the resist; and forming an element isolation insulating film on the semiconductor substrate.