JPH09172006A - Formation of device separation membrane of semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of forming an element isolation film, which is superior in isolation characteristics, in a simple treating process. SOLUTION: An oxide film 22 for buffer use is formed on the whole surface of a semiconductor substrate 20 and an antioxidation film 24 is formed on the film 22. This film 24 is patterned to form an antioxidation film pattern 24a having a hole, through which the film 22 on an insert region is made to expose, and the film 22 exposed through this hole is wet-etched, whereby an undercut is formed between the pattern 24a and the substrate 20. An oxidation-resistant material layer is formed on the whole surface of the substrate, which is a resultant material, and the oxidation- resistant material layer, which is formed on the upper part and sidewall part of the pattern 24a and the inert region, is removed, whereby a pattern of the above oxidation- resistant material layer is left in the undercut. The substrate, which is the result material, is exposed to an oxidizing atmosphere to form an element isolation film on the inert region. After a pattern of an oxinitride film 26 is formed on the edge part of an active region, the generation of a bird's beak is reduced for forming an element isolation film on the active region and the film 24 is formed of a material film, which is superior in the selectivity of etching to the film 22, whereby a damage to the substrate 20 is reduced.

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, and more particularly, to a semiconductor capable of reducing bird's beak while preventing damage to an active region of a semiconductor substrate. The present invention relates to a method for forming an element isolation film of an element.

[0002]

2. Description of the Related Art In manufacturing a semiconductor element, a method of forming an element isolation film for electrically isolating elements from each other is as follows.
In general, a local oxidation (hereinafter referred to as LOCOS) method is often used.

When the element isolation film is formed by the LOCOS method, there is a problem that a bird's beak occurs. The bird's beak is a bird's beak-shaped insulator formed by part of oxide atoms penetrating to the active region in the oxidation step for forming the element isolation film. With the high integration of semiconductor devices, the isolation region for isolating the devices is gradually becoming smaller. As a result, the bird's beak becomes a major factor in hindering high integration of the device. Therefore, the bar
Various methods have been proposed for suppressing the occurrence of zubik.

One of the methods is to use oxynitride instead of oxide as a buffer film formed to relieve the stress between the semiconductor substrate and the nitride film in the oxidation step for forming the element isolation film. Is the way.

1A to 1D are sectional views for explaining a conventional method for forming an element isolation film.

After the oxynitride film 12 for oxidation buffer is formed on the entire surface of the semiconductor substrate 10, a nitride film 14 for oxidation prevention is formed on the oxynitride film 12 (see FIG. 1A).

Next, the region where the element isolation film is formed, that is, the nitride film 14 formed on the inactive region C is etched to expose the oxynitride film 12 on this inactive region. After the nitride film pattern 14a having the holes 1 is formed, the oxynitride film 12 in the inactive region C is etched using the nitride film pattern 14a as an etching mask to form the oxynitride film pattern. Form a horn 12a (see FIG. 1B).

Next, the resulting substrate is exposed to an oxidizing atmosphere to form an element isolation film 16 in the inactive region (see FIG. 1C).

FIG. 1D shows that after the material layers (that is, the nitride film pattern 14a (see FIG. 1C) and the oxynitride film pattern 12a (see FIG. 1C)) stacked on the semiconductor substrate 10 are removed. FIG.

According to the conventional method of using an oxynitride film between the semiconductor substrate 10 and the nitride film 14 in order to reduce the occurrence of bird's beak, a bar that permeates the oxide film for stress relaxation. It is possible to remarkably reduce the occurrence of zubiks,
It may damage the surface of the semiconductor substrate.

The cause of damaging the surface of the semiconductor substrate will be described in detail below. The etching selectivity of the nitride film 14 to the oxynitride film 12 is lower than the etching selectivity of the nitride film to the oxide film. Therefore, when the nitride film 14 is etched to expose the oxynitride film in the inactive region (see FIG. 1B), the oxynitride film formed under the nitride film 14 is also removed. As a result, a defect occurs in the semiconductor substrate (A portion in FIG. 1B) below the oxynitride film.

Further, after forming the element isolation film 16,
When the material layers stacked to form the device isolation film are removed (see FIG. 1D), the nitride substrate has a low etching selectivity with respect to the oxynitride film, so that the semiconductor substrate (B portion) in the active region has defects. Occur.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and reduces the occurrence of bird's beak during the formation of an element isolation film, and the surface of a semiconductor substrate. An object of the present invention is to provide a method for forming an element isolation film of a semiconductor element for preventing damage to the semiconductor element.

[0014]

In order to achieve the above-mentioned object, a method of forming an element isolation film according to the present invention comprises: (a) an oxidation resistant material layer at an edge of an active region adjacent to an inactive region of a semiconductor substrate. The method is characterized by including a step of forming a pattern and (b) forming an element isolation film in the inactive region.

In the present invention, the step (a) is
1) a step of forming a buffer oxide film on the entire surface of a semiconductor substrate, and forming an antioxidant film on the buffer oxide film;
2) forming an antioxidant film pattern having holes for exposing the buffer oxide film in the inactive region by patterning the antioxidant film; and (a3) exposing through the hole. The step of forming an undercut between the pattern of the antioxidant film and the semiconductor substrate by wet-etching the buffer oxide film thus formed, (a4) obtained in the step (a3) Forming an oxidation resistant material layer on the entire surface of the resultant substrate, and (a5) removing the oxidation resistant material layer formed on the upper and side walls of the antioxidant film pattern and on the inactive region. The method includes the step of forming an oxidation resistant material layer pattern in the undercut.

The pattern of the oxidation resistant material layer is preferably made of oxynitride.

Further, in order to achieve the above object, the method for forming an element isolation film according to the present invention comprises: (a) a step of forming a buffer oxide film on the entire surface of a semiconductor substrate; and (b) the buffer oxidation. Forming an antioxidant film on the film, and (c) forming an antioxidant film pattern having holes for exposing the buffer oxide film in the inactive region by patterning the antioxidant film. And (d) forming an undercut between the pattern of the antioxidant film and the semiconductor substrate by wet etching the buffer oxide film exposed through the hole. , (E) a step of forming an oxidation resistant material layer on the entire surface of the substrate obtained as a result of the step (d), and (f) an upper portion and sidewalls of the antioxidant pattern and an inactive region. Remove the formed oxidation resistant material layer. And (g) exposing the substrate resulting from the step (f) to an oxidizing atmosphere to form an element isolation film in the inactive region. And a step of performing.

In the present invention, after the step (d),
The method may further include the step of forming a pad oxide film on the surface of the semiconductor substrate exposed by wet etching, and the pad oxide film may be formed to a thickness of about 20Å to 80Å.

In the present invention, it is preferable that the antioxidant film is formed of a material having excellent etching selectivity with respect to the buffer oxide film, for example, a nitride film.

In the present invention, the step (f) of partially removing the oxidation resistant material layer is preferably performed by wet etching.

In the present invention, the oxidation resistant material layer is preferably made of oxynitride.

[0022]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

2A to 2E are sectional views for explaining a method of forming an element isolation film according to the first embodiment of the present invention.

FIG. 2A shows a step of forming the buffer oxide film 22 and the antioxidant film 24. Specifically, first, an oxide film 22 for buffering is formed by growing an oxide on the entire surface of the semiconductor substrate 20. Then, an antioxidant film 24 such as a nitride is applied on the buffer oxide film 22 to form an antioxidant film 24.

In this step, the buffer oxide film 22 is preferably formed to a thickness of about 160Å. Also,
The antioxidant film 24 is formed, for example, by chemical vapor deposition 15
It is preferably formed to a thickness of about 00Å.

FIG. 2B shows a process of forming an undercut (UC) at the boundary between the active region and the inactive region.
Specifically, by partially etching the antioxidant film 24, an antioxidant film pattern 24a having a hole 1 for exposing the buffer oxide film 22 on the inactive region (D) is formed. Form. Then, the buffer oxide film 22 exposed through the hole 1 is wet-etched to form an undercut (UC) between the antioxidant film pattern 24a and the semiconductor substrate 20.

In the present embodiment, the antioxidant film 24 is formed of a material having excellent etching selectivity with respect to the buffer oxide film 22 (for example, nitride), and is used as a buffer when the antioxidant film is etched. The oxide film 22 is used as an etch stop layer. Therefore, when etching the antioxidant film, the conventional problem that the buffer oxide film is also etched and the surface of the semiconductor substrate is damaged does not occur. In addition, undercut (U
C) is formed at the boundary between the inactive region (D) and the active region (region other than the inactive region: E), which is formed on the inactive region (D) during wet etching. This is because the oxide film for buffer is removed and the oxide film for buffer formed at the boundary between the inactive region and the active region is also removed. As is well known, wet etching is a type of isotropic etching.

The wet etching for forming the undercut (UC) has, for example, an etching rate of the oxide film of 1 per minute.
Buffered Oxide Etcha for 200Å buffer
nt; BOE) for 10 seconds. According to the process under such conditions, the undercut (UC) is about 200Å ~
It can be formed to a depth of about 300Å (that is, a lateral length as shown in FIG. 2B).

FIG. 2C shows an undercut ("U" in FIG. 2B).
C ”) is formed on the entire surface of the resultant substrate, for example, 3
FIG. 6 is a cross-sectional view after forming an oxynitride film 26 by depositing oxynitride to a thickness of about 000Å. At this time, the oxynitride is under
It should be deposited to completely fill the cut.

In FIG. 2D, the pattern 24a of the antioxidant film is formed so that the oxynitride film remains only in the undercut.
FIG. 4 is a cross-sectional view after removing the oxynitride film formed on the upper and side walls and the inactive region. In the following, the oxynitride film that remains undercut will be referred to as a "plugged oxynitride film" 2
6a.

Embedded oxynitride film 26a
Is formed by performing wet etching for 3 minutes using BOE having an etching rate of the oxynitride film per minute of about 60Å to 90Å.

In FIG. 2E, the resultant structure shown in FIG. 2D is exposed to an oxidizing atmosphere to expose the device isolation film 28 in the inactive region.
FIG. 3 is a cross-sectional view after forming a.

When the element isolation film is formed by the normal LOCOS method, the bird's beak having a shape penetrating into the active region is
The embedded oxynitride film 26a prevents its formation. This is because the embedded oxynitride film 26a made of an oxidation resistant material is the oxide film 2 for buffering.
This is because oxygen is prevented from penetrating into 2.

The element isolation film 28 is formed to have a thickness of, for example, about 3500Å.

When the antioxidant film pattern 24a (see FIG. 2) is removed after the element isolation film 28 is formed, the buffer oxide film 22 is used as an etch stop layer. As described in the description of FIG. 2B, this is the pattern of the antioxidant film 24a.
Is formed of a material having excellent etching selectivity with respect to the buffer oxide film 22. Therefore, the conventional problem of damaging the surface of the semiconductor substrate by etching the buffer oxide film when the antioxidant film pattern is removed does not occur.

3A to 3E are sectional views for explaining a method for forming an element isolation film according to the second embodiment of the present invention.

In this embodiment, after forming an undercut (UC) by the same method as described with reference to FIG. 2B (see FIG. 3A), an undercut (UC) is formed.
A pad oxide film 30 having a thickness of, for example, 20Å to 80Å is formed on the surface of the semiconductor substrate exposed by the antioxidant film 24a (see FIG. 3B). Then, the oxynitride film 26 is formed by a method similar to that described with reference to FIG. 2C (see FIG. 3C). Then, the oxynitride film formed on the upper and side walls of the antioxidant film pattern 24a and the pad oxide film in the inactive region is removed by wet etching and embedded in the undercut. 26b (see FIG. 3D). Next, the element isolation film 32 is formed by exposing the resultant substrate shown in FIG. 3D to an oxidizing atmosphere.

As described above, according to the method of forming the element isolation film of the embodiment of the present invention, the oxynitride film is formed at the boundary between the active region and the inactive region to form the element isolation film. In the oxidization step for preventing the occurrence of bird's beak, it is possible to prevent oxygen atoms from penetrating into the buffer oxide film formed in the active region. Further, by forming the antioxidant film from a material having excellent etching selectivity with respect to the buffer oxide film, surface damage of the semiconductor substrate can be prevented.

The present invention is not limited to the above specific embodiments, and it is obvious that various modifications can be made by a person having ordinary knowledge in the technical field to which the present invention belongs.

[0040]

According to the present invention, it is possible to reduce the occurrence of bird's beak at the time of forming the element isolation film and prevent damage to the surface of the semiconductor substrate.

[0041]

[Brief description of the drawings]

FIG. 1A

FIG. 1B

[FIG. 1C]

FIG. 1D is a cross-sectional view illustrating a conventional method for forming an element isolation film.

FIG. 2A

FIG. 2B

FIG. 2C

[Fig. 2D]

FIG. 2E is a cross-sectional view illustrating the method for forming the element isolation film according to the first embodiment of the invention.

FIG. 3A

FIG. 3B

FIG. 3C

[Fig. 3D]

FIG. 3E is a sectional view illustrating the method for forming the element isolation film according to the second embodiment of the invention.

[Explanation of symbols]

 1 hole 10 semiconductor substrate 12 oxynitride film 12a oxynitride film pattern 14 nitride film 14a nitride film pattern 20 semiconductor substrate 22 oxide film 24 antioxidant film 24a antioxidant film pattern 26, 26b oxynitride film 30 pad oxide film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Shin, 103-23 Bunjeong-dong, Songpa-gu, Seoul, Republic of Korea

Claims (10)

[Claims] 1. A step of: (a) forming a pattern of an oxidation resistant material layer on an edge of an active region adjacent to an inactive region of a semiconductor substrate; and (b) forming an element isolation film on the inactive region. A method of forming an element isolation film of a semiconductor element, comprising: 2. The step (a) comprises: (a1) forming a buffer oxide film on the entire surface of the semiconductor substrate,
A step of forming an antioxidant film on the buffer oxide film, and (a2) by patterning the antioxidant film,
Forming an anti-oxidation film pattern having holes for exposing the buffer oxide film on the inactive region; and (a3) wet the exposed buffer oxide film through the holes. By etching, the antioxidant film pattern
A step of forming an undercut between the semiconductor substrate and the semiconductor substrate; (a4) a step of forming an oxidation resistant material layer on the entire surface of the substrate obtained as a result of the step (a3); A step of forming an oxidation resistant material layer pattern in the undercut by removing the oxidation resistant material layer formed on the upper and side wall portions and the inactive region of the antioxidant film pattern; The method for forming an element isolation film of a semiconductor element according to claim 1, further comprising: 3. The method of claim 1, wherein the pattern of the oxidation resistant material layer is made of oxynitride. 4. (a) forming a buffer oxide film on the entire surface of the semiconductor substrate; (b) forming an antioxidant film on the buffer oxide film; and (c) preventing the oxidation. Patterning the film to form an antioxidant film pattern having holes for exposing the buffer oxide film in the inactive region; and (d) exposing the buffer through the holes. A step of forming an undercut between the anti-oxidation film pattern and the semiconductor substrate by wet etching an oxide film for use in etching, and (e) the resulting product obtained in the step (d). A step of forming an oxidation resistant material layer on the entire surface of the substrate, and (f) removing the oxidation resistant material layer formed on the upper and side walls of the anti-oxidation film pattern and the inactive region, Under-cut oxidation resistant material layer pattern
A step of leaving an element isolation film in the inactive region by exposing the substrate resulting from the step (f) to an oxidizing atmosphere. Method for forming element isolation film of element. 5. The device according to claim 4, further comprising the step of forming a pad oxide film on the surface of the semiconductor substrate exposed by wet etching after the step (d). Method for forming separation membrane. 6. The method of claim 5, wherein the pad oxide film is formed to a thickness of about 20Å to 80Å. 7. The method of claim 4, wherein the antioxidant film is formed of a material having a high etching selectivity with respect to the buffer oxide film. 8. The method of forming an element isolation film of a semiconductor device according to claim 7, wherein the oxidation prevention film is formed of a nitride film. 9. The method of claim 4, wherein the step (f) of partially removing the oxidation resistant material layer is performed by wet etching. 10. The method of claim 4, wherein the oxidation resistant material layer is made of oxynitride.