Semiconductor device manufacturing: process – Coating with electrically or thermally conductive material – To form ohmic contact to semiconductive material
Reexamination Certificate
1998-07-08
2001-04-24
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Coating with electrically or thermally conductive material
To form ohmic contact to semiconductive material
C438S592000, C438S680000
Reexamination Certificate
active
06221771
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a forming method of forming tungsten silicide (WSi
x
) on polysilicon or single crystal silicon in manufacturing a semiconductor device, and to a semiconductor manufacturing method and a semiconductor device to which this method is applied.
2. Background Art
It has become usual that, in a semiconductor device, a tungsten silicide (WSi
x
) film is formed on a polysilicon or single crystal silicon included in a silicon wafer. The tungsten silicide (WSi
x
) has a possibility of exhibiting a low electrical resistance. On the other hand, the film forming process of the tungsten silicide is very much influenced by a surface condition of a polysilicon or a silicon. This tends to cause a process failure such as peeling of a silicide film, so that stable depositing of a silicide film having superior characteristics is difficult. This is a problem in the application to the mass production. Hereinafter, in the present invention, a technical term of the silicon wafer is used to mean either a polysilicon or a single crystal silicon.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the above-mentioned problems, and the object thereof is to stably obtain a tungsten silicide film of superior performances.
According to one aspect of the present invention, a method of forming a tungsten silicide film comprises the following processes in the following order. First, a temperature raising process of disposing a silicon wafer in an inert gas atmosphere and raising the temperature thereof. Next, a first dichlorosilane (DCS) treatment process of introducing DCS so as to generate a surface reaction of the silicon wafer. Next, a first deposition process of introducing WF
6
in addition to the DCS so as to generate a surface reaction of the silicon wafer. Then, a second DCS treatment process of shutting off the WF
6
and introducing the DCS. Finally, a second deposition process of introducing WF
6
in addition to the DCS so as to deposit tungsten silicide.
In the method of forming a tungsten silicide film, a surface of the silicon wafer is preferably reduced through the temperature raising process and the first DCS treatment process.
In the method of forming a tungsten silicide film, the first DCS treatment process and the first deposition process are performed preferably at an atmospheric pressure which is 1.5 to 3.0 times as high as an atmospheric pressure in the temperature raising process, the second DCS treatment process, and the second deposition process.
In the method of forming a tungsten silicide film, a mixture ratio between the WF
6
and the DCS in the first deposition process is preferably in a range of 1:300 to 1:500, and a mixture ratio between the WF
6
and the DCS in the second deposition process is preferably in a range of 1:30 to 1:50.
In the method of forming a tungsten silicide film, an introduced quantity of the DCS in the second DCS treatment process is set preferably to be substantially equal to that in the second deposition process.
In the method of forming a tungsten silicide film, a flow quantity ratio of the DCS between the first deposition process and the second deposition process is preferably set to be in a range of 1:1 to 5:1.
In the method of forming a tungsten silicide film, preceding the first DCS treatment process, preferably performed is a surface treatment process of processing the surface of the silicon wafer into a surface state in which the DCS decomposes easily.
In the method of forming a tungsten silicide film, the surface state has preferably termination of Si with fluorine (F).
In the method of forming a tungsten silicide film, the surface treatment process comprises preferably a process of processing the surface of the silicon wafer with dilute hydrofluoride solution (DHF) the concentration of which is not less than 0.05%, and a process of drying the surface of the silicon wafer with F constituent left thereon.
In the method of forming a tungsten silicide film, the surface treatment process preferably comprises a process of processing the surface of the silicon wafer using any of gas phase HF, NF
3
or ClF
3
.
In the method of forming a tungsten silicide film, instead of the temperature raising process, preferably performed is a treatment process of processing the silicon wafer using H
2
gas in a range of 300° C. to 850° C.
In the method of forming a tungsten silicide film, instead of the temperature raising process and the first DCS treatment process, preferably performed is a treatment process of processing the silicon wafer using H
2
gas in a range of 300° C. to 850° C.
In the method of forming a tungsten silicide film, preceding to the temperature raising process, preferably performed is a treatment process of processing the silicon wafer with either a processing solution of hydrogen peroxide the concentration of which is in a range of 0.1 to 35%, a processing solution in which solved is O
3
the concentration of which is in a range of 0.5 to 30 ppm, or a processing solution in which hydrogen peroxide and ozone are solved.
In the method of forming a tungsten silicide film, any of the processing solutions preferably contain HF the concentration of which is in a range of 0.001 to 0.5%.
In the method of forming a tungsten silicide film, instead of the temperature raising process, preferably performed is a treatment process of processing the silicon wafer using either O
2
gas, O
3
gas, or H
2
O vapor.
In the method of forming a tungsten silicide film, instead of the temperature raising process or the first DCS treatment process, preferably performed is a treatment process of processing the silicon wafer using either O
2
gas, O
3
gas, or H
2
O vapor.
In the method of forming a tungsten silicide film, preferably a tungsten-high constituting layer is deposited on an interface with the silicon wafer, and a tungsten-low constituting layer is deposited on the tungsten-high constituting layer.
In the method of forming a tungsten silicide film, the ratio in number between tungsten atoms and silicon atoms in the tungsten silicide film is preferably 2.4 or less in the tungsten-high constituting layer, and is preferably 2.5 or more in the tungsten-low constituting layer.
According to another aspect of the present invention, a method of fabricating a semiconductor device comprises a process in which the tungsten silicide film is formed through a forming process as defined above.
According to another aspect of the present invention, a semiconductor device comprises the tungsten silicide film formed through a forming process as defined above.
Other and further objects, features and advantages of the invention will appear more fully from the following description.
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Patent Abstracts of Japan -E-839 Nov. 2, 1989 vol. 13/No. 483.
Ban Cozy
Teramoto Akinobu
Hoang Quoc
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Nelms David
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