JPS5875845A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To suppress the production of a bird beak by surrounding the side of a mask layer with an Si3N4 film and then selectively oxidizing it. CONSTITUTION:A thin SiO2 film 2 and a thin silicon oxynitride (SixNyOz) film 3 are sequentially formed on a silicon substrate 1, are photolithographically patterned, thereby removing the SiO2 film and the SixNyOz film except on an element forming region 5. Then, an Si3N4 film 4 is formed by a CVD method on the overall surface. Then, the region 5 is removed, the film 4 is removed, and the film is allowed to remain only at the periphery of a laminated mask. Thereafter, a selective oxidation is performed, thereby forming an isolating oxidized film 6. In this manner, lateral oxidation is suppressed, thereby preventing the productin of a bird beak.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device that suppresses the occurrence of bird's beak. In semiconductor devices such as MOS and IC, a large number of semiconductor elements are simultaneously manufactured on a silicon substrate by the same process. 6 Semiconductor elements are separated by a thick oxide film layer with 1-2 grooves.This oxide film is called an isolation oxide film or field oxide film, and is formed in an oxidizing atmosphere. ing.

Now, in the case of a semiconductor element (for example, a MOS transistor), an oxide film with a thickness of approximately 5 oool is formed in advance in the element formation region for the purpose of preventing crystal defects. An oxide film at the edges also grows at the same time, which becomes an obstacle when forming sources, drains, and gates in those regions.

During the formation of this isolation oxide film, the oxide layer produced in the element formation region by lateral oxidation is called a bird's beak and is an hindrance to the manufacture of semiconductor devices.

An object of the present invention is to suppress the occurrence of bird's beaks during the manufacture of semiconductor devices17, and as a method for this purpose, a semiconductor element forming area having a laminated pattern of silicon oxide/silicon oxynitride is coated with silicon nitride, and then oxidation for isolation is performed. By forming a film, lateral oxidation is suppressed.

The inventor filed a patent application No. 55-138316 (October 3, 1982).
A pattern consisting of three layers of silicon oxide/silicon oxynitride/silicon nitride formed on a silicon substrate is formed on a semiconductor element formation area, and this is humidified and thermally oxidized in an oxygen atmosphere. In particular, a method for forming an isolation oxide film is currently pending, and the present invention is a further development of this method.

The present invention will be explained below with reference to the drawings in comparison with the previous application. FIG. 1 is a process diagram according to the previous application, FIG. 2 is an explanatory diagram of the bird's beak that occurs at this time, and FIG. 3 is a process diagram according to the present invention.

FIG. 1 is a process diagram for forming a semiconductor element on a silicon substrate, in which the silicon substrate 1 is heat-treated in a dry oxygen atmosphere at 1000°C to form a silicon oxide (hereinafter referred to as S) of approximately 500×.
low) Form a thin film 2 (Figure A).

Next, a thin film 3 of silicon oxide nitride (hereinafter referred to as 81 x Ny Oz) having a thickness of 0.2 or more layers is formed on this film by chemical vapor deposition (hereinafter referred to as CVD method) (Figure B).

This formation of S i x Ny Oz 463 is a feature of the previous application, and no thin film is provided in the conventional process.

The 8 i x Ny Os thin film 3 is formed using the same equipment and similar gas composition to the next thin film formation of silicon nitride (hereinafter referred to as 811N4). ) s oxygen (0
1).

By introducing a mixed gas of nitrogen (N) in which the flow rate ratio of oxygen and monosilane is O, S or higher (0,: 81H, ≧0.3) into a device heated to approximately 800°C, silicon substrates can be melted. The one in Marugame is made to grow to the top.

There is a limit of 0.2 seconds or more of blurring (MOB): It
Is this related to the improvement in voltage resistance of the gate SiO snow film when manufacturing transistors (conventional MOS)? The defective gate breakdown voltage of the transistor is caused by the reaction between the 7jC and 5isN+ thin films during the process of forming the isolation oxide film.Nitrogen compounds such as 9NHs NOx diffuse into the 81jN thin film and the 5ins thin film and react with them. , 5ilN4 thin film and 5l because of the relationship between producing silicon nitride.
S1 with a thickness of 0.2 layers or more between the ot thin film
x NyOz thin film was provided as the buffer 1.

Next, a S 1 s N4 thin film 4 is formed using a conventional CVD method (Fig.
After coating the isNa4 film 4 with photoresist, freon gas (
Pattern etching is performed by dry etching using a reactive gas such as CF4) (Figure D).
By heating at a temperature of 900 to 1100° C. in an oxygen atmosphere, selective oxidation is performed except for the semiconductor element forming region 5, resulting in an isolating oxidation layer consisting of a stow with a thickness of 0.8 to 2 mm. A film 6 is formed (Figure E).

Figure 2 shows the 8 i x N y Oz thin films 3 and 8 that served as pattern Jung masks in Figure 1 (Figure E).
This is an enlarged partial cross-sectional view of a laminated film consisting of a 11 Nm thin film 4, with a 5i (h thin film 2) having a thickness of about 50 OA on the silicon substrate 1 in the semiconductor element formation region 5, and a thick isolation layer around it. However, the SiO snow thin film 2 at this boundary is affected by this during selective oxidation, resulting in a bird's beak shape in which an oxide film with a width of X grows around the periphery. A phenomenon can be seen.

This phenomenon always occurs during the manufacturing of conventional semiconductor devices, and although the gate breakdown voltage of semiconductor devices has improved in the inventor's previous application, this bird's beak phenomenon has significantly improved in nine cases compared to the conventional method. Although it has been reduced, it has not been possible to eliminate it.

However, if this bird's beak exists, the effective area will be different from the design area when forming sources, drains, etc. in the semiconductor element forming region 5, which will make it difficult to miniaturize the integrated circuit.
I was playing K.

The present invention relates to a previously filed method for manufacturing a semiconductor device using a 98xNyOz thin film as an intermediate layer, and relates to a manufacturing method for suppressing bird's beak.

FIG. 3 shows the process according to the present invention, including the formation of an 810-thick thin film 2 on a silicon substrate 1 (Figure A), and the formation of an 810-thick film 2 on the silicon substrate 1 (Figure A).
The formation of the 1N, OS thin film 3 (Figure B) is the same as the previous step.

Next, after coating the entire surface with photoresist, photolithography is applied to remove the semiconductor element forming area 5 and remove the Bl.
ot and 81 x NyOz g (Fig. 0)
Next, a SlsNm thin film 4 is formed on the entire surface by the CVD method (Fig. D), and then the 811N4 thin film 4 is removed except for the half-bond/body element preformation region 5 by photolithography (Fig. E). There is a pattern in which 5iXNyO2 thin film 3 is laminated on top of 5ins thin film 2. This is Big! 'ta thin film 4
It is covered by S10! The thin film 2 is isolated from the atmosphere.

Next, when selective oxidation is performed in this state, an isolation oxide film 6 is grown on the substrate 1, but since the semiconductor element forming region 5 is covered with 511N4 thin [4], lateral oxidation is suppressed, and therefore bird's beak is prevented. Does not occur.

The present invention relates to a method for manufacturing a semiconductor device that suppresses bird's beak, and the manufacturing method has been explained using a pending device structure in which the gate breakdown voltage of a semiconductor device such as an MO8φ IC is set to several values, but the method is not limited to this. do not have.

[Brief explanation of drawings]

1(4) to (G) are explanatory diagrams of the manufacturing process of the semiconductor device according to the previous application, FIG. 2 is an explanatory diagram of a bird beak, and FIGS. It is a perspective view of the manufacturing process. In the figure, 1 is a silicon substrate, 2 is a thin brittle SiO film, 3 is an 81xNyOx thin film, 4 is a 5lsN+ thin film, 5 is a semiconductor element formation region, and 6 is an isolation oxide film. Figure 2

Claims (1)

[Claims] Semiconductor element formation area Kl on silicon substrate * After selectively laminating a silicon oxide film and a silicon oxynitride film to form a pattern, the scissors frame portion is selectively covered with a silicon nitride film, and then The silicon nitride film! 1. A method for manufacturing a semiconductor device, comprising: forming an isolation oxide film by selectively oxidizing a silicon substrate.