Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
2000-02-09
2001-11-06
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C118S7230ER, C118S7230IR, C156S345420
Reexamination Certificate
active
06311638
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a plasma processing method and apparatus that produces a plasma by the energy of a high-frequency wave, such as a microwave, etc. and processes a workpiece, such as a semiconductor wafer, with the plasma.
2. Description of the Related Art
Semiconductor device fabricating processes include a plasma processing process that processed semiconductor wafers (hereinafter referred to simply as “wafers”) with a plasma.
FIG. 12
shows a known microwave plasma processing system for carrying out such a plasma processing process. This known microwave plasma processing system has a vacuum vessel
9
, a work support table
91
placed in the vacuum vessel
9
to support a wafer W thereon, and a plane slot antenna
92
disposed in an upper region of the interior of the vacuum vessel
9
. Microwaves radiated by a microwave power generator
93
is fed through a waveguide
94
to the antenna
92
, the microwaves are fed from the antenna
92
to produce a plasma by ionizing a processing gas supplied from a gas supply pipe
95
, and a film is deposited on the surface of the wafer W or the surface of the wafer W is etched with the plasma. In
FIG. 12
, indicated at
96
is a quartz window.
A load matching device
97
is placed on the waveguide
94
to make conjugate the impedance of a section of the waveguide
94
between the load matching device
97
and the plasma and the impedance of a section of the same between the load matching device
97
and the microwave power generator
93
to suppress reflection of the microwave from the plasma.
The electron density of the plasma is one of factors dominating the condition of the process for processing the wafer W. When a gas that does not produce negative ions is used, electron density is substantially equal to plasma density. When a gas that produces negative ions is used, negative ion density increases as electron density decreases. Therefore, it is desirable for stable processing to keep electron density constant during the process. However, it is difficult to know electron density and hence it is not easy to control electron density.
The condition of a plasma is dependent on the microwave power and pressure in the vacuum vessel
9
. Therefore, microwave utilization factor in using a microwave for producing a plasma decreases even if the impedances are matched by the load matching device
97
because some condition of the plasma increases the amount of the microwave reflected by the plasma toward the microwave power generator
93
and the reflected microwave generates heat due to dielectric loss or ohmic loss.
The present invention has been made in view of such problems and it is therefore an object of the present invention to enable monitoring the electron density of a plasma by measuring the reflection coefficient of high-frequency waves, such as microwaves or RF waves, radiated by a power generator.
SUMMARY OF THE INVENTION
According to an aspect of the present invention, the above object is attained by a plasma processing method comprising the steps of: placing an object to be subjected to a processing into a vacuum vessel; supplying a processing gas into the vacuum vessel; supplying a high-frequency wave into the vacuum vessel from a high-frequency power generator; subjecting the object to the processing by generating a plasma of the processing gas in the vacuum vessel by the high-frequency wave; measuring a state of a reflected high-frequency wave reflected at the plasma, relative to an advancing high-frequency wave travelling toward the plasma; and controlling an electron density of the plasma in response to a measured state of the reflected high-frequency wave.
According to another aspect of the present invention, the above object is attained by a plasma processing apparatus comprising: a vacuum vessel; a device for supplying a processing gas into the vacuum vessel; a high-frequency power generator for supplying a high-frequency wave into the vacuum vessel to produce plasma of the processing gas; a measuring unit for measuring state of a reflected high-frequency wave reflected at the plasma, relative to an advancing high-frequency wave travelling from the high-frequency power generator toward the plasma; and a control unit for controlling an electron density of the plasma in response to the state of the reflected high-frequency wave measured by the measuring unit.
The above and other object, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings.
REFERENCES:
patent: 5458732 (1995-10-01), Butler et al.
patent: 5472561 (1995-12-01), Williams et al.
patent: 5688357 (1997-11-01), Hanawa
patent: 5698036 (1997-12-01), Ishii et al.
patent: 5702562 (1997-12-01), Wakahara
patent: 09-063793 (1997-03-01), None
Ando Makoto
Goto Naohisa
Ishii Nobuo
Yasaka Yasuyoshi
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Hassanzadeh P.
Mills Gregory
Tokyo Electron Limited
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