JPS635567A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To make it possible to form with a simple process a gate electrode of low resistance and excellent accuracy, by employing a dry etching method of polycrystalline silicon and a selective chemical vapor growth of tungsten. CONSTITUTION:After a polycrystalline silicon layer is formed on a silicon oxide film 2 formed on the surface of a silicon substrate 1, a mask 4 is formed. Successively the polycrystalline silicon layer is subjected to an etching, and a lower layer of gate electrode 3, is formed. In this process, the mask 4 is used, and a dry etching method applying a reaction gas containing oxygen, for example SF6+O2 gas, is employed. By this etching, a thin oxide film 5 is simultaneously formed on the side surface of the lower layer of gate electrode 3. After the mask 4 is eliminated, a tungsten film is selectively grown on the lower layer of gate electrode 3, at a forming temperature of tungsten silicide, by a chemical vapor growth method applying WF6 gas. Thereby, a gate electrode of low resistance can be formed with excellent accuray in a simple process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming a gate electrode made of polycrystalline silicon and tungsten silicide having low resistance.

[Conventional technology]

Conventionally, in order to form a low-resistance gate electrode using a two-layer structure of polycrystalline silicon and tungsten silicide, the polycrystalline silicon layer on the semiconductor substrate was buttered to form the lower layer of the gate electrode, and then the 5102 film was chemically processed. It is formed on the entire surface by chemical vapor deposition method, etc., and then reactive ion etching method (
After removing the 5I02 film on the upper surface of the lower layer of the gate electrode by RIE method (hereinafter referred to as RIE method), depositing tungsten on the entire surface of the substrate by sputtering or vapor deposition, and siliciding only the upper part of the lower layer of the gate electrode by heat treatment.
A commonly used method was to remove unreacted tungsten.

[Problem that the invention seeks to solve]

However, in the conventional method for forming a gate electrode made of polycrystalline silicon and tungsten silicide, the formation of the 5I02 for side surface coating of the lower layer of the gate electrode includes a chemical vapor deposition process and an RIE process for the 5I02 film, so the process is slow. It had the disadvantage of being complex.

Additionally, since tungsten covers the entire surface of the substrate in the silicidation heat treatment process, S1 atoms diffuse into the silicide film formed during the heat treatment, forming silicide even in unnecessary parts above the source/drain regions. There were also drawbacks.

An object of the present invention is to provide a method for manufacturing a semiconductor device that can form a low-resistance gate electrode with high accuracy through simple steps.

[Means for solving problems]

The method for manufacturing a semiconductor device of the present invention includes the steps of forming a polycrystalline silicon layer on an oxide film formed on the surface of a semiconductor substrate, and forming a mask made of photoresist on the polycrystalline silicon layer, and then containing oxygen. The polycrystalline silicon layer is etched by a dry etching method using a reactive gas to form a gate electrode lower layer, and at the same time an oxide film is formed on the side surfaces of the gate electrode lower layer, and after the mask is removed, a chemical etching process using WF6 gas is performed. forming a tungsten silicide film by selectively growing a tungsten film on the lower layer of the gate electrode at a tungsten silicide formation temperature by a vapor phase growth method, and forming a gate electrode made of the lower layer of the gate electrode and the tungsten silicide film; It consists of:

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are cross-sectional views of a semiconductor chip shown in the order of steps for explaining an embodiment of the present invention.

First, as shown in FIG. 1 (a), a polycrystalline silicon layer is formed on a silicon oxide film 2 formed on the surface of a silicon substrate 1, and then a mask 4 made of photoresist is formed on this polycrystalline silicon layer. Next, using this mask 4, the polycrystalline silicon layer is etched by a dry etching method using a reactive gas containing oxygen, such as SF6+02 gas, to form the gate electrode lower layer 3. Through this etching, the gate electrode lower layer 3 is etched. A thin oxide film 5 is simultaneously formed on the side surfaces of.

Next, as shown in FIG. 1(b), after removing the mask 4, a tungsten film is selectively grown on the gate electrode lower layer 3 at the tungsten silicide formation temperature by chemical vapor deposition using WF6 gas. let

The chemical vapor deposition method for tungsten is WF using silicon.
Since this is a reduction reaction of No. 6, tungsten does not adhere to the side surfaces of the gate electrode lower layer 3 coated with S+02. At this stage, if the temperature of the silicon substrate 1 is set to the tungsten silicide formation temperature (approximately 600° C.), the deposited tungsten immediately reacts with the underlying polycrystalline silicon to form a tungsten silicide film 6.

Here, by setting the deposition rate of tungsten to be smaller than the rate of the silicidation reaction and the diffusion rate of silicon that diffuses upward from the gate electrode lower layer 3 into the tungsten silicide film 6, the tungsten deposition surface becomes tungsten. The tungsten silicide film 6 is continuously generated without stopping the reaction between the WF 6 and the silicon, and the low resistance gate electrode 10 consisting of the gate electrode lower layer 3 and the tungsten silicide film 6 can be formed with high precision. can.

〔Effect of the invention〕

As explained above, the present invention uses a dry etching method for polycrystalline silicon using a reactive gas containing oxygen and a selective chemical vapor deposition method for tungsten, thereby achieving low resistance etching in a simple process. A method for manufacturing a semiconductor device is obtained in which a gate electrode can be formed with high precision.

[Brief explanation of drawings]

FIGS. 1(a) and 1(b) are cross-sectional views of a semiconductor chip shown in order of steps for explaining an embodiment of the present invention.

Claims (1)

[Claims] A polycrystalline silicon layer is formed on the oxide film formed on the surface of the semiconductor substrate, and after a mask made of photoresist is formed on the polycrystalline silicon layer, a polycrystalline silicon layer is formed using a dry etching method using a reactive gas containing oxygen. etching the crystalline silicon layer to form a gate electrode lower layer and simultaneously forming an oxide film on the side surfaces of the gate electrode lower layer;
After removing the mask, a tungsten film is selectively grown on the lower layer of the gate electrode by chemical vapor deposition using WF_6 gas at the tungsten silicide formation temperature to form a tungsten silicide film, and the tungsten silicide film is bonded to the lower layer of the gate electrode. 1. A method of manufacturing a semiconductor device, comprising the step of forming a gate electrode made of a silicide film.