JPH05121398A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress a length of a bird's beak of a LOCOS and prevent diffusion of a channel stopper in an active unit by forming and patterning a silicon nitride film on an oxidized Si substrate, wet etching an oxide film with the nitride film as a mask and then implanting B. CONSTITUTION:After an Si substrate 1 is oxidized to form a silicon oxide film 2, an Si nitride film 3 is formed. The film 2 is formed thicker than that of a conventional laid oxide film. A LOCOS pattern is formed of photoresist 4. With the photoresist 4 as a mask the film 3 is etched, and then the resist 4 is removed. With the film 3 as a mask the film 2 is wet etched. In this case a side etch is intentionally formed. With the film 3 as a mask B for a channel stopper is ion-implanted. After a LOCOS is formed by thermally oxidizing, the film 3 is removed. The film 3 on an active part is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a method of manufacturing an element isolation region in an integrated circuit.

[0002]

2. Description of the Related Art FIGS. 2A to 2D are schematic views showing a method of forming an element isolation region in an integrated circuit.

In FIG. 2, 1 is a silicon substrate, 2 is a silicon oxide film, 3 is a silicon nitride film, 5 is B (boron), and 6 is LOCOS.

Since this manufacturing method is a method of forming LOCOS in a general semiconductor process at present, it will be described only briefly.

In FIG. 2A, the silicon substrate 1 is thermally oxidized,
After forming the silicon oxide film 2, the silicon nitride film 3 is deposited by the CVD method.

In FIG. 2B, the silicon nitride film 3 is formed by LOCO.
After etching only the S portion, B (boron) for the channel stopper is ion-implanted using this as a mask.

In FIG. 2 (c), LOCOS6 is formed by thermal oxidation.
To form.

In FIG. 2D, the silicon nitride film 3 is removed.

[0009]

2 (a) to FIG. 2 described above.
The following points are pointed out as problems in the forming method of the conventional example of (d).

First, the LO formed by the conventional manufacturing method.
In COS, the silicon oxide film penetrates into the end portion of the silicon nitride film to form a so-called bird's beak. This bird's beak not only hinders the miniaturization of the device, but also brings about an adverse effect such as a narrow channel effect in terms of characteristics.

Secondly, in the conventional manufacturing method, B (boron) for the channel stopper is implanted to the end portion of the silicon nitride film. Therefore, when LOCOS is formed, B (boron) diffuses to the outside of the LOCOS. I will end up. The diffusion of this channel stopper (B) is caused by the source. Even after the drain is formed and the contact is opened, it remains under the contact hole and causes a leak. In order to suppress this leak, it is necessary to perform ion implantation after forming the contact.

The present invention has been made in order to solve the above-mentioned problems, in which the bird's beak length is made shorter and the diffusion of the channel stopper (B) is LO.
It is possible to form without reaching the COS edge, L
It is intended to provide a method for forming OCOS.

[0013]

A method of manufacturing a semiconductor device according to the present invention comprises a first step of forming a silicon oxide film on a semiconductor substrate and then forming a silicon nitride film on the silicon oxide film. A second step of forming a photoresist pattern for forming an element isolation region on the silicon nitride film, and etching the silicon nitride film using the photoresist pattern as a mask, and then peeling and removing the photoresist pattern. A third step; a fourth step of wet-etching the silicon oxide film with the silicon nitride film pattern as a mask; a fifth step of ion-implanting into the semiconductor substrate with the silicon nitride film pattern as a mask; Sixth step of removing the silicon nitride film after forming an element isolation region by thermal oxidation after implantation After the silicon nitride film is removed, a manufacturing method of a semiconductor device which comprises a silicon oxide film on Akti _Lee blanking region seventh step of removing by wet etching, and.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 1A to 1G are sectional views showing the sequence of steps in the process of LOCOS showing an embodiment of the present invention.

1A to 1G will be described below in the order of steps.

In FIG. 1A, the silicon substrate 1 is oxidized to form a silicon oxide film 2, and then a silicon nitride film 3 is deposited by the CVD method. In this step, the silicon oxide film 2 is formed thicker than the underlying oxide film of the prior art.

In FIG. 1 (b), the LOC is formed by the photoresist.
An OS pattern is formed.

In FIG. 1C, the silicon nitride film 3 is etched using the photoresist 4 as a mask, and then the photoresist 4 is peeled and removed.

In FIG. 1D, the silicon oxide film 2 is etched using the silicon nitride film 3 as a mask.

At this time, a side etch is intentionally formed.

In FIG. 1E, B (boron) for a channel stopper is ion-implanted using the silicon nitride film 3 as a mask. This ion implantation is formed thicker than usual.

After forming the LOCOS 6 by thermal oxidation in FIG. 1D, the silicon nitride film 3 is removed.

In FIG. 1E, the silicon oxide film on the active is removed.

In this embodiment, in FIG. 1D, the silicon oxide film is intentionally side-etched by wet etching so that the ion-implanted region of the channel stopper (B) is at the center of the LOCOS formation portion. Since it is formed only in the vicinity, it is possible to suppress the length of the bird's beak due to the difference in the oxidation rate between the LOCOS (ion implantation region) and the LOCOS end. Further, since there is a gap between the end of the ion implantation region and the end of the exposed portion of the silicon substrate, it is possible to prevent the diffusion of the channel stopper (B) after forming the LOCOS from reaching the LOCOS end.

[0025]

As described above, the present invention makes it possible to suppress the bird's beak length of LOCOS with respect to LOCOS in an integrated circuit, and to prevent the diffusion of the channel stopper to the active portion. Become.

[Brief description of drawings]

1A to 1E are cross-sectional structural views in order of steps of LOCOS showing an embodiment of the present invention.

2A to 2D are cross-sectional structural views in order of the steps, showing a conventional method for manufacturing a LOCOS.

[Explanation of symbols]

 1 Silicon Substrate 2 Silicon Oxide Film 3 Silicon Nitride Film 4 Photoresist 5 B (Boron) 6 LOCOS

[Procedure amendment]

[Submission date] October 29, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1A to FIG. 1G are sectional views showing a process sequence of LOCOS showing an embodiment of the present invention.

2A to 2D are cross-sectional structural views in order of the steps, showing a conventional method for manufacturing a LOCOS.

Claims (1)

[Claims] 1. A first step of forming a silicon nitride film on the silicon oxide film after forming a silicon oxide film on a semiconductor substrate, and a photolithography process for forming an element isolation region on the silicon nitride film. A second step of forming a resist pattern, a third step of etching the silicon nitride film using the photoresist pattern as a mask, and then a peeling removal of the photoresist pattern, and a third step of using the silicon nitride film pattern as a mask. A fourth step of wet etching the silicon oxide film, a fifth step of ion-implanting the semiconductor substrate using the silicon nitride film pattern as a mask, and a step of forming an element isolation region by thermal oxidation after the ion implantation, and then the silicon Sixth step of removing the nitride film, and silicon on the active region after removing the silicon nitride film. A seventh step of removing the oxide film by wet etching, and a method of manufacturing a semiconductor device.