Plasma processing apparatus

Details Plasma processing apparatus Plasma processing apparatus

2000-03-22

2002-01-22

Mills, Gregory (Department: 1734)

Coating apparatus

Gas or vapor deposition

With treating means

C156S345420

Reexamination Certificate

active

06339997

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
Referenced-applications
This application claims the priority of Japanese Patent Application No. 11-103946, filed on Apr. 12, 1999, the entire contents of which is hereby incorporated herein by reference.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
Not Applicable
REFERENCE TO A MICROFICHE APPENDIX
Not Applicable
BACKGROUND OF THE INVENTION
DESCRIPTION OF THE RELATED ART
FIG. 17
is a front-surface sectional view of a conventional plasma processing apparatus possessing an inductively coupled plasma generation system. A vacuum chamber consists of a lower chamber
10
and an upper chamber
12
, these two being in communication with one another. The lower chamber
10
, which has a generally cylindrical shape, is made of metal. The upper chamber
12
constitutes a discharge chamber, and its sidewall includes a power lead-in window
14
which is made of a dielectric material. The power lead-in window
14
has the shape of a cylinder with, for example, an inner diameter of 362 mm and a height of 100 mm. Around the power lead-in window
14
, a generally ring-shaped (loop-shaped) antenna
18
is disposed in a manner such that it surrounds this window
14
. The top plate
16
of the upper chamber
12
is made of metal, and is grounded. The interior of the vacuum chamber can be pumped out via an exhaust port
20
. Process gas is introduced from a gas delivery system
22
which is connected to the top plate
16
. A substrate
26
which is to be processed is set on a substrate holder
24
. When the substrate holder
24
is in position for plasma processing, its top surface (the surface on which the substrate
26
is set) is located near the lower end of the upper chamber
12
(the portion thereof which is in communication with the lower chamber
10
).
The plasma processing apparatus of
FIG. 17
is used in the following manner. Process gas is introduced into the vacuum chamber and maintained at a required discharge pressure of
100
Pa or less. In this state, high-frequency power with a frequency of 13.56 MHz is supplied to the antenna
18
, and power is supplied into the upper chamber
12
through the power lead-in window
14
. This results in the production of a plasma in the concentrations in the upper chamber
12
. Active species in the plasma effect processing (e.g., etching or deposition of a film) of the substrate
26
which is carried by the substrate holder
24
.
FIG. 19
is a perspective view of the antenna
18
which is used in the apparatus of FIG.
17
. The antenna
18
is essentially ring-shaped and has, in a portion thereof, a cut-out constituting a power supply portion. The shape of the transverse section of the antenna
18
is that of a long, thin rectangle. In its transverse section, the dimension a in the vertical direction is 2 mm, and the dimension b in the horizontal direction is 15 mm. The dimension a in the vertical direction is the dimension measured parallel to the central axis of the cylindrical power lead-in window, and can be called the antenna width. The dimension b in the horizontal direction is the dimension measured normally to the central axis of the power lead-in window, and can be called the antenna thickness.
When high-frequency power with a frequency of 13.56 MHz is used when the antenna
18
is employed for the production of a plasma, a plasma can be produced by an almost perfect inductively coupled mode (see the disclosure of Japanese Laid-open Patent Application No. 8-203695). Since the area of the antenna
18
inner periphery portion which faces the plasma in the upper chamber
12
is small (i.e., since the antenna width a is small), it is possible to achieve plasma formation solely by a practically perfect inductively coupled mode, and so efficient plasma generation is possible.
FIG. 18
is a front sectional view which shows the state at the time of substrate change in the apparatus of FIG.
17
. After the substrate holder
24
has been lowered, a gate valve
28
is opened to open a substrate transfer-in/out port
30
, and replacement of the substrate
26
is effected using a suitable substrate transfer device (not shown). Since it is difficult to provide the substrate transfer-in/out port
30
in the power lead-in window
14
made of a dielectric, it is necessary to provide it in the lower chamber
10
and effect substrate
26
replacement after lowering the substrate holder
24
as described above.
FIELD OF THE INVENTION
The present invention relates to a plasma processing apparatus, and more particularly it relates to a plasma processing apparatus which has special features by which alternating-current power which produces a plasma is led into a vacuum chamber.
BRIEF SUMMARY OF THE INVENTION
Generally, when plasma processing is effected in a vacuum chamber, a film is deposited on the inner wall surface of the vacuum chamber. For example, when an oxide film on a substrate is etched, a freon-based process gas is used, with the result that an organic film is deposited. Also, in a CVD process, a film is deposited on portions other than a substrate. A film which has been deposited on the inner wall surface of a vacuum chamber is liable to peel off if the temperature of this wall surface changes. This occurs because the coefficient of thermal expansion of the deposited film and the coefficient of thermal expansion of the inner wall surface of the vacuum chamber are different, and, consequently, stress is produced in the deposited film when the temperature of the vacuum chamber inner wall surface changes. The deposited film which has peeled off falls inside the vacuum chamber and becomes a source of dust particle contamination. In order to prevent peel-off of the deposited film due to stress, it is necessary to keep the vacuum chamber heated to a constant temperature.
In the plasma processing apparatus shown in
FIG. 17
, the power lead-in window
14
is used for leading in high-frequency power. However, since the power lead-in window
14
is made of a dielectric material, it is more difficult to heat it to a constant temperature than it is to thus heat the lower chamber
10
made of metal. Ways of heating the power lead-in window
14
include resistance heating, heating by light, and heating by a liquid medium, etc. However, the high-frequency electric field becomes strong in the vicinity of the power lead-in window
14
, and this field becomes disordered by the electric circuit used in resistance heating or light heating using a lamp, in addition to which there is a risk of damage to the electric circuit used for heating, since high-frequency power is superimposed on it. Further, when ordinary quartz glass is used as a dielectric material, the heating efficiency is poor and it is difficult to effect uniform heating in a method of heating using light, since the quartz glass passes hardly any light of the infrared region. In heating using a liquid medium, the procedure is that the power lead-in window is made a double structure, and power lead-in window temperature control is effected by flowing a liquid medium in the space of this structure, but there is a risk of leakage of the liquid, and, in addition, the structure of the power lead-in window is complex. Thus, it is not easy to heat the power lead-in window uniformly. However, if the power lead-in window is not heated uniformly, the risk of a film which has been deposited on the inner wall surface of the power lead-in window peeling off because of stress increases.
Since, accompanying the increase of the area of substrates, there is a trend to increase the area of power lead-in windows, a temperature gradient is liable to be produced in a power lead-in window. This temperature gradient too is the cause of easy peel-off of a deposited film. Further, when a power lead-in window made of a dielectric material is made larger, there is an increased risk of breakage.
Thus, in a conventional plasma processing apparatus, when a film has been deposited on the inner wall surface of the power lead-in window made of a dielectric, it is difficult to prevent peel-off

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