Semiconductor device manufacturing: process – Chemical etching – Vapor phase etching
Reexamination Certificate
1999-04-30
2001-02-20
Powell, William (Department: 1765)
Semiconductor device manufacturing: process
Chemical etching
Vapor phase etching
C438S715000, C438S719000, C438S720000, C438S738000, C216S072000, C216S075000, C216S079000
Reexamination Certificate
active
06191045
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of treating the surface of a sample such as a semiconductor device and, more particularly, to a sample surface treating method of performing etching by using a plasma.
2. Related Background Art
For etching a semiconductor device, a system utilizing a plasma is widely used. The invention is applied to such a system using the plasma. Conventionally, as a plasma for etching a tungsten film, fluorine gas, chlorine gas, bromine gas, or a mixed gas of those gases is used as described in “Semiconductor Process Handbook”, supervised by Yasuo Tarui, pp. 92-93, Press Journal.
As a semiconductor device becomes faster and power consumption becomes lower, resistance in a conductive part such as an electrode and a wire part has to be made lower. Consequently, in order to form a gate electrode of a MOS (Metal Oxide Semiconductor) device, which conventionally employs a polysilicon film, a polysilicon film is formed on a silicon oxide film, and a tungsten film is formed on the polysilicon film. Further, in order to suppress counter diffusion, a barrier film such as a tungsten nitride film is necessary between the polysilicon film and the tungsten film.
When the films having such a multilayer structure are etched, a problem which does not occur conventionally arises due to an etch reaction difference between polysilicon and tungsten. For example, in case of applying a fluorine gas as an etching gas, since the etch rate of polysilicon is faster, it is difficult to suppress the etch rate of the polysilicon film after etching the tungsten film. The silicon oxide film is therefore exposed to a fluorine gas plasma and etched. In case of applying the chlorine gas as an etching gas, since the etch rate of tungsten is slower, the tungsten film or the barrier film remains partially on the polysilicon film. A problem such as occurrence of roughness on the etch surface arises. It is known that means of increasing the etch rate of the tungsten film by the chlorine gas plasma can be improved by increasing the temperature of a sample. Since the temperature of the sample is high at the time of performing etching to the polysilicon film after completion of the etching to the tungsten film, there is a problem such that the etching develops isotropically and side etching occurs.
SUMMARY OF THE INVENTION
It is an object of the invention to solve the problems and to provide a sample surface treating method adapted to treat a sample having a multilayer which is deposited on a semiconductor substrate and includes at least a metal film and a semiconductor film.
In order to achieve the object, according to a feature of the present invention, there is provided a method of treating a sample having a multilayer which is deposited on a semiconductor substrate and includes at least a metal film and a semiconductor film by using a surface treating system comprising: a vacuum chamber; means for generating a plasma in the chamber; a stage on which a sample to be subjected to surface treatment with the plasma is placed; a temperature controlling mechanism for controlling the temperature of the stage; and a power supply for applying an rf (radio frequency) voltage to the stage, wherein the sample is maintained at a temperature from 100° C. to 200° C. at the time of treating the metal film.
In the invention, by etching the metal film while maintaining the sample at a temperature from 100° C. to 200° C., the etch rate of the metal film is increased.
Further, according to another feature of the invention, in order to suppress the etch rate of the polysilicon film and prevent the side etching, an oxygen gas is added to a gas containing a halogen element.
According to further another feature of the invention, the process of treating the multilayer is divided into a plurality of steps in which the sample temperatures are set to different values. More specifically, in order to suppress the etch rate of the silicon oxide film at the time of etching of the polysilicon film, the treatment is carried out by using etch parameters which are divided into at least metal film etch parameters and polysilicon film etch parameters.
REFERENCES:
patent: 4886571 (1989-12-01), Suzuki et al.
“Semiconductor Process Handbook”, supervised by Yasuo Tarui, Press Journal, pp. 92-93.
Akiyama Hiroshi
Hasegawa Hiroshi
Katou Kunihiko
Kawakami Hiroshi
Kojima Masayuki
Antonelli, Terry Stout & Kraus, LLP.
Hitachi , Ltd.
Powell William
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