JPH01186659A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable an element separation area with less defects for achieving highly integrated semiconductor by forming a silicon nitride film after introducing a large amount of phosphor into oxide film on a silicon substrate. CONSTITUTION:An oxide film 202 and an oxide film 203 including phosphor are formed on a silicone substrate 201. Then, it is left at a high temperature for a specified amount of time and phosphor is diffused into the lower-layer thermal oxide film 202. Then, after performing etching elimination of the oxide film 203 including phosphor, a silicon nitride film 204 is formed, an organic resist film 205 is formed, and a resist film at the element separation area 205 is eliminated. With the remaining resist as a mask, the silicon nitride film 204 and the silicon oxide film 202 are opened 206, the organic resist 205 is eliminated, and the silicon substrate is subject to wet oxidation at a high temperature. The silicon oxide film 202 directly below the silicon nitride film 204 becomes soft due to high temperature and relaxes expansion of volume by viscosity flow, and reduces stress for the silicon substrate 201. It allows an element area with less defects to be formed and high integration of semiconductor element to be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method for manufacturing a semiconductor device, and more particularly to an improvement in a method for manufacturing a region for separating elements formed on a semiconductor.

(Prior Art) As is well known, a semiconductor thermal oxide film has conventionally been used as a region for separating elements, and the method for forming this is to use a silicon nitride film as a mask and cover it with a silicon nitride film. A widely used method is to form an element isolation region by thermally oxidizing a region that does not exist. According to this technique, as shown in FIG. 2, at the end of the silicon nitride film, since the silicon nitride film 103 is hard, the thermal oxide film 102, which has been oxidized and expanded in volume, is deformed by stress. The stress in the thermal oxide film is alleviated by the deformation, but at the same time, the influence of stress spreads to the semiconductor substrate 101, causing countless defects in the semiconductor.

For this reason, a region that cannot be used as a device is generated around the semiconductor device region, which effectively reduces the degree of integration of semiconductor devices.

(Problems to be Solved by the Invention) As described above, the method of forming element isolation regions using thermal oxide films hinders high integration of semiconductors. Therefore, it is an object of the present invention to improve the manufacturing method and provide an element isolation method that enables high integration.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, in the present invention, a large amount of phosphorus is introduced into an oxide film on a silicon substrate, a silicon nitride film is formed, and an opening in the silicon nitride film is formed. It is characterized by forming a thermal oxide film after removing the thermal oxide film below.

(Function) When phosphorus is introduced into a silicon oxide film and the temperature is raised, the silicon oxide film becomes soft, so the oxide film directly under the silicon nitride film undergoes viscous flow, which alleviates the volumetric expansion and increases the resistance to the silicon substrate. Reduces stress and prevents defects from occurring. Therefore, an element region with fewer defects is formed, and higher integration of semiconductor elements becomes possible.

(Example) The effects of the present invention will be explained below using examples.

FIG. 1 is a process diagram for explaining an example.

First, as shown in FIG. 1(a), for example, an oxide film 202 of 500 layers is formed on an n-type silicon substrate 201 by thermal oxidation. An oxide film 203 containing phosphorus is formed thereon by a known vapor phase growth method (FIG. 1(b)).

After this, the oxide film 203 is left at a high temperature of 950°C for 1 hour.
The phosphorus contained in the phosphorus is diffused into the underlying thermal oxide film. After removing the phosphorus-containing oxide film 203 using a known etching technique, a silicon nitride film 204 is removed using a known vapor phase growth method.
Form 000 people. An organic resist film 205 is formed thereon (FIG. 1C), and the resist film in the element isolation region is removed by known light exposure and development techniques. Using the remaining resist as a mask, the silicon nitride film and silicon oxide film are formed into openings 206 by known anisotropic reaction etching.
Furthermore, the organic resist film is removed (Fig. 1 (d)), and the silicon substrate is then oxidized by wet oxidation at 1000°C (Fig. 1 (c)). The silicon oxide film directly under the silicon nitride film is softened by the high temperature. This causes viscous flow.

Therefore, although the oxide film on the silicon type substrate that is not covered with the silicon nitride film expands in volume, the shape of the silicon oxide film directly under the silicon nitride film hardly changes. Therefore, the intermediate region for element isolation becomes smaller, and the influence of stress on the silicon substrate can also be reduced. In this way, an element region with fewer defects can be formed.

Further, the method of introducing phosphorus into the silicon oxide film used in the present invention is not limited to diffusion from a solid phase, and various methods such as ion implantation can be used.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to form an element region with few defects, and it is possible to realize highly integrated semiconductor elements.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the manufacturing process of an embodiment of the present invention;
FIG. 2 is a cross-sectional view of a manufacturing process using a conventional element isolation method. 101, 201...Silicon substrate. 102, 202... silicon oxide film, 103, 204
... silicon nitride film, 203 ... phosphorus glass,
205...Organic resist film, 206...Opening. Figure 1

Claims (1)

[Claims] After forming a silicon oxide film containing 10^1^9 cm^-^2 or more of phosphorus on a semiconductor substrate and forming a silicon nitride film on this, an opening is formed in the silicon nitride film, and a surface is formed in the opening. 1. A method of manufacturing a semiconductor device, which comprises removing a silicon oxide film and thermally oxidizing the exposed semiconductor surface.