JPH10256247A - Semiconductor device manufacturing method - Google Patents

Abstract

(57) [Problem] To form an element isolation region, a conventional OSE
While making use of the advantages of the flatness and element isolation withstand voltage, which have been advantages of the LO method, further miniaturization is possible and high integration of a semiconductor device is enabled. SOLUTION: A semiconductor substrate 1 is oxidized to form an SiO ₂ film 2.
Is formed thereon, and a SiN film 3 and a SiO ₂ film 4 are formed thereon.
_{The two-} layer film 2, the SiN film 3, and the SiO ₂ film 4 are selectively left, and the SiN film 5 and the polysilicon film 9 are entirely formed from above.
Then, only the polysilicon film 9 is etched, and the SiN film 5 is left on the three-layer film and on the side walls.
A polysilicon sidewall 10 is formed outside the sidewall of the substrate, and is oxidized and grown to increase the width. Subsequently, the SiN film 5 is removed.
Exposing a portion of the semiconductor substrate 1 to be the element isolation region 8;
After removing the SiO ₂ film 4 and the polysilicon sidewall 10,
Using the SiN films 5 and 3 as a mask, the whole is oxidized to form an element isolation region 8, and then the SiN films 5, 3 and the SiO ₂ film 2 are removed, thereby leaving the element isolation region 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an element isolation region suitable for high integration of a semiconductor element.

[0002]

2. Description of the Related Art In recent years, miniaturization of element isolation regions has become a major issue with the increase in integration of semiconductor devices. To address such issues, LOCOS (Local
Oxidation) method and improved LO
The COS method is being used.

FIGS. 3 and 4 are process explanatory views of a conventional method of manufacturing a semiconductor device, and particularly show a method of forming an element isolation region using a conventionally proposed improved LOCOS method.

As shown in FIG. 3A, first, a semiconductor substrate 1 is oxidized to form a thin silicon oxide film,
An iO ₂ film 2 is formed, and a silicon nitride film is formed thereon.
An SiN film 3 is formed. Further, an SiO ₂ film 4 is formed as a silicon oxide film on the SiN film 3.

[0005] Subsequently, as shown in FIG. 3 (B), etching is performed through a lithography process, and a three-layered film of SiO ₂ film 2, SiN film 3 and SiO ₂ film 4 is selectively formed in the active region. Leave.

Next, as shown in FIG. 3C, a SiN film 5 is formed as a silicon nitride film as a whole, and a SiO ₂ film 6 is further formed thereon as a silicon oxide film.

Following the above steps, as shown in FIG. 3D, the SiO ₂ film 6 and the SiN film 5 are removed by RIE.
(Ieactive Ion Etching) method, and the SiO ₂ film 2, the SiN film 3 and the S
A sidewall is formed while leaving only the sidewall of the three-layer film of the iO ₂ film 4 as the SiO ₂ sidewall 7.

Subsequently, as shown in FIG. 4A, the SiO ₂ film 4 and the SiO ₂ side walls 7 are wet-etched.
Is removed to leave regions of the SiO ₂ film 2, the SiN film 5, and the SiN film 3 on the semiconductor substrate 1.

Thereafter, as shown in FIG. 4B, the semiconductor substrate 1 is entirely oxidized to form an element isolation region 8.

Subsequently, as shown in FIG.
The films 3 and 5 and the SiO ₂ film 2 are removed, and finally, an element isolation region 8 is formed.

According to the above-described steps, the ordinary L
Compared with the OCOS method, since there is no thin SiO ₂ film, that is, a buffer oxide film below the SiN offset portion, a bird's peak is less likely to occur, an element isolation region can be reduced, and oxidation above the semiconductor substrate 1 can be prevented. It is suppressed and is advantageous for flattening. Also, since the oxide film region extends downward by that amount, there is an advantage that the breakdown voltage of the element isolation region is higher than that of a semiconductor device formed by the LOCOS method having the same width of the element isolation region.

[0012]

The conventional method for forming an element isolation region by the improved LOCOS method in the method of manufacturing a semiconductor device is constructed as described above.
Although it has many advantages as compared with the OS method, it cannot simply cope with further miniaturization of element isolation regions due to the growing demand for higher integration of semiconductor devices in recent years. It has been the limit of the improved LOCOS method.

The present invention seeks to solve the above-mentioned problems of the prior art, and further utilizes the advantages of the improved LOCOS method of the prior art, such as flatness and element isolation withstand voltage, while further improving the characteristics. It is an object of the present invention to provide a method of manufacturing a semiconductor device which enables miniaturization and enables high integration of the semiconductor device.

[0014]

According to the present invention, there is provided a semiconductor device comprising: a step of selectively forming a coating film covering an active region on a semiconductor substrate; After the silicon films are sequentially buried, only the polysilicon film is etched, and the polysilicon film is left as a sidewall on the side surface of the coating film via the nitride film. A laterally extending area of the bottom surface of the side wall covering the nitride film to form an enlarged side wall, and etching the nitride film thereunder using the enlarged side wall as a mask. A semiconductor device comprising: a step of forming a mask nitride film as a mask for an oxide film extending to the side of a cover film; and a step of forming an element isolation region by oxidizing using the mask nitride film as a mask. Manufacture It is intended to provide the law.

Further, in order to achieve the above object, according to the present invention, a semiconductor substrate is oxidized to form a thin first silicon oxide film, and a first silicon nitride film is formed thereon.
A first step of forming a second silicon oxide film from above the first silicon nitride film, and etching the first silicon oxide film, the first silicon nitride film, A second step of selectively leaving the three-layer film of the second silicon oxide film, and a third step of forming a second silicon nitride film on the whole and further forming a polysilicon film thereon Etching only the polysilicon film,
On the second silicon nitride film, a three-layer film of the first silicon oxide film, the first silicon nitride film, and the second silicon oxide film, and a poly-silicon film on a side wall of the three-layer film. A fourth step of leaving the silicon film as a polysilicon sidewall, and oxidizing and growing the polysilicon sidewall,
A fifth step of further widening the width, a sixth step of etching and removing an exposed portion of the second silicon nitride film, and removing the second silicon oxide film and the polysilicon sidewall. A seventh step of leaving the first silicon oxide film and the first and second silicon nitride films in a portion corresponding to the active region of the semiconductor substrate; and oxidizing the semiconductor substrate as a whole to form an element isolation region. An object of the present invention is to provide a semiconductor device manufacturing method comprising: an eighth step of forming; and a ninth step of removing the first and second silicon nitride films and the first silicon oxide film.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a process chart of a method for manufacturing a semiconductor device according to an embodiment of the present invention, and particularly illustrates a process related to formation of an element isolation region.

As shown in FIG. 1A, first, a semiconductor substrate 1 is oxidized to form a thin SiO ₂ film 2 and a SiN film 3 is formed thereon. Further, a SiO ₂ film 4 is formed on the SiN film 3.

Subsequently, as shown in FIG. 1B, etching is performed through a lithography process, and a three-layered film of SiO ₂ film 2, SiN film 3 and SiO ₂ film 4 is selectively formed in the active region. Leave.

Next, as shown in FIG.
The iN film 5 is slightly thicker than the OSELO method, for example,
A film of about 000 Å is formed, and a polysilicon film 9 is formed thereon.

Following the above steps, as shown in FIG. 1D, only the polysilicon film 9 is etched by RIE, and the SiO ₂ film 2 and the Si
A sidewall is formed by leaving only the sidewall of the three-layer film of the N film 3 and the SiO ₂ film 4 as the polysilicon sidewall 10.

Subsequently, as shown in FIG. 1E, the polysilicon side wall 10 is oxidized and grown.
Is further expanded to form an enlarged polysilicon sidewall 10A.
That is, the area of the element isolation region to be formed thereafter is relatively reduced.

Thereafter, as shown in FIG.
By IE, the SiN film 5 is left only in a part of the active region and the others are removed.

Subsequently, as shown in FIG. 2B, the SiO ₂ film 4 and the polysilicon side wall 10 are removed by wet etching, and the SiO ₂ film 2 is formed on the semiconductor substrate 1.
The regions of the SiN film 5 and the SiN film 3 are left.

Thereafter, as shown in FIG. 2C, the semiconductor substrate 1 is entirely oxidized to form an element isolation region 8.

Subsequently, as shown in FIG.
The films 3 and 5 and the SiO ₂ film 2 are removed, and finally, an element isolation region 8 is formed in a region other than a portion corresponding to the active region.

In the embodiment described above, after the polysilicon side wall 10 is formed, it is oxidized to increase the width of the polysilicon side wall 10 in advance.
Thereafter, since the SiN film 5 is etched away, the width of the subsequently formed element isolation region 8 can be reduced. As a result, miniaturization of the element isolation region is achieved.

[0027]

As described above, according to the method of manufacturing a semiconductor device of the present invention, a polysilicon sidewall formed as a sidewall of an active region is etched prior to etching a SiN film serving as a mask for forming an element isolation region. Is oxidized to increase its width, and as a result, the area of the SiN film is increased in advance, and the oxidized area in forming the element isolation region by oxidizing the semiconductor substrate using the SiN film as a mask is reduced. Therefore, the area of the element isolation region can be reduced,
As a result, there is an effect that a semiconductor device manufacturing method suitable for high integration of a semiconductor device can be realized.

[Brief description of the drawings]

FIG. 1 is a part of a process chart for explaining an embodiment of a semiconductor device manufacturing method of the present invention.

FIG. 2 is a part of a process chart for describing an embodiment of a semiconductor device manufacturing method of the present invention.

FIG. 3 is a part of a process chart for explaining a conventional semiconductor device manufacturing method.

FIG. 4 is a part of a process chart for explaining a conventional semiconductor device manufacturing method.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 semiconductor substrate 2, 4, 6 SiO ₂ film 3, 5 SiN film 7 SiO ₂ side wall 8 element isolation region 9 polysilicon film 10 polysilicon side wall 10A enlarged polysilicon side wall

Claims (2)

[Claims] 1. A step of selectively forming a coating film covering an active region on a semiconductor substrate, and a step of selectively embedding a nitride film and a polysilicon film over the whole, and then removing only this polysilicon film. Etching to leave the polysilicon film as a sidewall on the side surface of the coating film via the nitride film; and expanding the sidewall in the lateral direction by oxidation so that the bottom surface of the sidewall covers the nitride film. Enlarging the area in the lateral direction to form an enlarged side wall; and using the enlarged side wall as a mask, etching the nitride film thereunder to thereby form a mask nitride as an oxide film mask extending to the side of the coating film. A method of manufacturing a semiconductor device, comprising: a step of forming a film; and a step of forming an element isolation region by oxidizing using the mask nitride film as a mask. 2. A semiconductor substrate is oxidized to form a thin first silicon oxide film, a first silicon nitride film is formed thereon, and a second silicon nitride film is formed on the first silicon nitride film. A first step of forming a silicon oxide film, and a three-layer film of the first silicon oxide film, the first silicon nitride film, and the second silicon oxide film are selected in the active region by etching. A second step in which a second silicon nitride film is formed entirely, and a third step in which a polysilicon film is further formed thereon; etching the polysilicon film only; A three-layer film of the first silicon oxide film, the first silicon nitride film and the second silicon oxide film on the second silicon nitride film, and a polysilicon film on a side wall of the three-layer film. Process of leaving each as a polysilicon sidewall A fifth step of oxidizing and growing the polysilicon sidewall and further widening the width thereof; a sixth step of etching and removing an exposed portion of the second silicon nitride film; A seventh step of removing the silicon oxide film and the polysilicon sidewall and leaving the first silicon oxide film and the first and second silicon nitride films in a portion corresponding to the active region of the semiconductor substrate; An eighth step of oxidizing the semiconductor substrate to form an element isolation region; and a ninth step of removing the first and second silicon nitride films and the first silicon oxide film. Semiconductor device manufacturing method.