JPH04373124A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To inhibit the generation of a foreign substance at the time of removal of a natural oxide film on a polycrystalline silicon film as well as to ensure the adhesion of the polycrystalline silicon film to a tungsten silicide film in a method of forming a tungsten polysilicide film consisting of the polycrystalline silicon film and the tungsten silicide film. CONSTITUTION:An amorphous silicon film 4 is formed on a polycrystalline silicon film 3 formed on a silicon substrate 1 with an oxide film 2 formed thereon by a chemical vapor growth method using gas containing SiH4 as its main component and thereafter, a tungsten silicide film 5 is formed by a CVD method without exposing a silicon wafer to the atmosphere.

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 a method for manufacturing the same, and more particularly to the structure of a tungsten polycide film consisting of a polycrystalline silicon film and a tungsten silicide film, and a method for forming the same.

0002

[Prior Art] Polycrystalline silicon has been used as a gate material for a long time, but it generally has a higher resistivity than metals, and is one of the causes of signal transmission delays as devices become smaller. It started to become one. Therefore, a tungsten silicide film is being used as a new gate material. The advantages of tungsten silicide film are as follows. (1) Compared to polycrystalline silicon, resistivity is approximately one order of magnitude lower. (2) Its chemical properties are very similar to polycrystalline silicon, and it can be handled in almost the same way as polycrystalline silicon in the process.

However, the tungsten silicide film is
When used as a material for the gate electrode of an S transistor,
In order to make the threshold characteristics of MOS transistors the same as those of conventional polycrystalline silicon gates and to not impair the stability of MOS transistors, impurities are currently added to the bottom of the tungsten silicide film to have the desired polarity. A so-called tungsten polycide film, which is covered with a polycrystalline silicon film injected with tungsten, is widely used.

FIGS. 2A to 2C are step-by-step cross-sectional views showing a conventional method for forming a tungsten polycide film. In the figure, 1 is a silicon substrate, 2 is an oxide film, 3 is a polycrystalline silicon film, and 5 is a tungsten silicide film.

First, as shown in FIG. 2(a), a chemical vapor deposition method (
A polycrystalline silicon film 3 is formed by a CVD method (hereinafter abbreviated as CVD method). Thereafter, it is removed from the growth apparatus, and a desired type of impurity is implanted into the polycrystalline silicon 3 to determine its polarity. At this time, a natural oxide film is easily formed on the polycrystalline silicon film 3. In general, tungsten silicide films have poor adhesion to oxide films.

Therefore, as shown in FIG. 2(b), as a pretreatment before forming a tungsten silicide film, for example, reactive etching using CF4 gas 6 or sputter etching using Ar gas 7 is performed to form a polycrystalline film. The natural oxide film formed on the silicon film 3 is removed.

Next, as shown in FIG. 2(c), for example, WF6 and SiH4 or SiH2 Cl2
A tungsten silicide film 5 is formed on the polycrystalline silicon film 3 by the CVD method using a gas containing as a main component.

[0008]

[Problems to be Solved by the Invention] Conventional semiconductor devices and methods for manufacturing the same are constructed as described above, and a natural oxide film is interposed between the underlying polycrystalline silicon film and the tungsten silicide film to improve adhesion. was not good. Furthermore, when forming a tungsten polycide film, the natural oxide film on the polycrystalline silicon film is removed by etching in pretreatment to ensure adhesion between the underlying polycrystalline silicon film and the tungsten silicide film. When using reactive etching, reaction by-products adhere to the silicon wafer, and when using sputter etching, the etched polycrystalline silicon or oxide film adheres to the silicon wafer, which becomes foreign matter and damages the semiconductor. There is a problem in that the manufacturing yield of the device is reduced.

The present invention was made to solve the above-mentioned problems, and it is possible to ensure adhesion between the underlying polycrystalline silicon film and the tungsten silicide film, and to prevent the manufacturing yield from decreasing. The purpose of the present invention is to provide a semiconductor device and a method for manufacturing the same.

0010

SUMMARY OF THE INVENTION In a semiconductor device according to the present invention, an amorphous silicon layer is interposed between a polycrystalline silicon film serving as a base and a tungsten silicide film.

The method for manufacturing a semiconductor device according to the present invention also includes a step of doping a polycrystalline silicon film formed on a wafer with a predetermined impurity, and a step of chemical vapor deposition using a gas containing SiH4 as a main component. forming an amorphous silicon layer on the polycrystalline silicon film by a method;
After the formation of the amorphous silicon layer, a tungsten silicide film is formed on the amorphous silicon layer by chemical vapor deposition without exposing the wafer to the atmosphere.

0012

[Operation] In this invention, as a pretreatment before forming a tungsten silicide film on a polycrystalline silicon film doped with impurities, an amorphous silicon layer is formed on the surface of the polycrystalline silicon film using a gas mainly composed of SiH4. After the tungsten silicide film is formed, the tungsten silicide film is formed by the CVD method, so the tungsten silicide film and the natural oxide film on the polycrystalline silicon are not in direct contact with each other through the amorphous silicon layer, and the tungsten silicide film is Adhesion to the base can be ensured. Furthermore, since etching is not used as a pretreatment before forming the tungsten silicide film, generation of foreign matter due to etching can be suppressed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to process cross-sectional views of FIGS. 1(a) to 1(c). In the figure, the same reference numerals as in FIG. 2 indicate the same or corresponding parts, and 4 indicates an amorphous silicon layer formed between the polycrystalline silicon film 3 and the tungsten silicide film 5.

Next, the manufacturing method will be explained. Figure 1 (a
) As shown in the conventional example, an oxide film 2 and a polycrystalline silicon film 3 are formed on a silicon substrate 1. Thereafter, the film is removed from the growth apparatus, and a desired type of impurity is implanted into the polycrystalline silicon film 3 to determine its polarity. At this time, a natural oxide film is formed on the surface of the polycrystalline silicon film 3.

Next, as shown in FIG. 1(b), SiH4
An amorphous silicon layer 4 is formed on the polycrystalline silicon film 3 using a gas containing as a main component. At this time, since the amorphous silicon layer 4 has good adhesion to the natural oxide film on the polycrystalline silicon film 3, it is thought that the resistance can be lowered even if there is a natural oxide film between it and the polycrystalline silicon film 3. .

Furthermore, as shown in FIG. 1(c), the silicon wafer is processed by WF6 in the same device in which the amorphous silicon layer 4 is formed, without releasing the silicon wafer to the atmosphere.
Then, a tungsten silicide film 5 is formed on the amorphous silicon layer 4 by CVD using a gas containing SiH4 or SiH2 Cl2 as a main component.

As described above, according to this embodiment, as a pretreatment before forming a tungsten silicide film on the polycrystalline silicon film 3 doped with impurities, the surface of the polycrystalline silicon film 3 is coated with SiH4 as a main component. After forming the amorphous silicon layer 4 with a gas of 100%, the wafer is then subjected to CVD using a gas containing WF6 and SiH4 or SiH2 Cl2 as main components without exposing the wafer to the atmosphere.
Since the tungsten silicide film 5 is formed by the method, the tungsten silicide film 5 and the natural oxide film on the polycrystalline silicon 3 do not come into direct contact with each other, and the amorphous silicon layer 4 does not come into direct contact with the natural oxide film below and the natural oxide film above. It has good adhesion to the tungsten silicide film 5, and by interposing the amorphous silicon layer 4, the adhesion between the tungsten silicide film 5 and the underlying polycrystalline silicon film 3 can be ensured. Furthermore, since etching is not used as a pretreatment before forming the tungsten silicide film 5, unlike the conventional method, generation of foreign matter due to etching can be suppressed, and the manufacturing yield can be improved.

[0018]

As described above, according to the present invention, SiH4
After forming an amorphous silicon layer on the surface of the polycrystalline silicon film using a gas whose main component is , a tungsten silicide film is formed using the CVD method.
The tungsten silicide film and the natural oxide film on the polycrystalline silicon do not come into direct contact with each other, ensuring good adhesion with the base of the tungsten silicide film, and etching can be used as a pretreatment before forming the tungsten silicide film. Since it is not used, the generation of foreign matter due to etching is suppressed, and as a result, the manufacturing yield can be improved.

[Brief explanation of drawings]

FIG. 1 is a process cross-sectional view showing a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

1 Silicon substrate 2 Oxide film 3 Polycrystalline silicon film 4 Amorphous silicon layer 5 Tungsten silicide film

Claims (2)

[Claims] 1. A tungsten polyester film composed of a polycrystalline silicon film formed on a wafer, an amorphous silicon layer formed on the polycrystalline silicon film, and a tungsten silicide film formed on the amorphous silicon layer. A semiconductor device characterized by having a side film. 2. A semiconductor device manufacturing method in which a polycrystalline silicon film is formed as a base on a wafer, doped with a predetermined impurity, and then a tungsten silicide film is formed thereon. A step of doping a crystalline silicon film with a predetermined impurity, and
A step of forming an amorphous silicon layer on the polycrystalline silicon film by chemical vapor deposition using a gas mainly composed of 1. A method of manufacturing a semiconductor device, comprising: forming a tungsten silicide film by a method.