Coating apparatus – Work holders – or handling devices
Reexamination Certificate
1999-05-20
2001-07-03
Mills, Gregory (Department: 1763)
Coating apparatus
Work holders, or handling devices
C118S724000, C118S728000, C118S725000, C156S345420
Reexamination Certificate
active
06254683
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field of the Invention
The present invention relates to a substrate temperature control method and device in a thin-film forming step in the manufacture of semiconductor elements, liquid crystal display panels or solar cells etc., or plasma processing apparatuses used in micro-processing steps.
2. Description of Related Art
In recent years, in plasma processing apparatuses, in order to achieve higher device functionality and lower processing costs, great efforts are being made to achieve higher precision, higher speeds, increase of area, and lower damage rates. In this connection, it is desired in particular to achieve uniform and precise control of the substrate temperature over its surface in order to obtain uniformity of film quality within the substrate during deposition and to ensure dimensional accuracy in the dry etching which is used in micro-processing. In order to achieve this, mechanical clamps or electrostatic attracting electrodes are employed as means for controlling substrate temperature and plasma processing apparatuses have begun to be used in which cooling is performed by introducing heat-conducting gas between the substrate and substrate holder.
A plasma processing apparatus using a conventional substrate temperature control device is described below.
FIG. 2
shows the reaction chamber of a plasma processing apparatus constituting an example of the prior art. In
FIG. 2
,
101
is a vacuum chamber having means for reactive gas supply
130
and means for vacuum evacuation
131
,
102
is an item to be treated or a substrate such as a silicon wafer, and
103
is an electrostatic attraction-type substrate holder comprising an alumina dielectric part
104
of thickness 5 mm and an aluminum base part
105
provided with a cooling water passage (not shown) in its interior. A pair of internal electrodes
106
A,
106
B for providing electrostatic attraction and consisting of tungsten are embedded 500 &mgr;m within the outer surface of alumina dielectric part
104
. A substrate push-up mechanism
120
is provided for substrate feed purposes within substrate holder
103
.
121
is a spacer made of ceramics which electrically insulates vacuum chamber
101
and substrate holder
103
. Holes for supplying heat-conductive gas are provided on the face of substrate holder
103
that contacts substrate
102
. In this example, holes of diameter 1 mm are regularly arranged at five locations.
107
is a high frequency filter,
108
is a positive electrode DC power source,
109
is a negative electrode DC power source,
110
is a capacitor,
111
is a high frequency power source of frequency 13.56 MHz, and
112
is a grounded upper electrode.
113
is means for heat-conductive gas supply that supplies heat-conductive gas such as He to the gap between the upper surface of substrate holder
103
and the under-surface of substrate
102
, comprising a valve and flow rate controller.
114
is a vacuum meter for monitoring the pressure of the heat-conductive gas at the under-surface of substrate
102
; the pressure of the heat-conductive gas is controlled by an automatic pressure control valve
115
controlled by a signal from this vacuum meter
114
. The flow rate of heat-conductive gas is changed in steps by means of a mass flow controller
116
and constructed so as to supply heat-conductive gas in a short time into a reservoir space comprising piping.
The operation of the plasma processing apparatus constructed as above will now be described. First of all, vacuum chamber
101
is evacuated to vacuum and substrate
102
is arranged on substrate holder
103
; by applying positive and negative DC voltages of 1.0 kV from respective DC power sources
108
and
109
through high-frequency filters
107
to the pair of internal electrodes
106
A and
106
B, substrate
102
is electrostatically attracted on to substrate holder
103
.
Next, He gas is supplied to the under-surface of substrate
102
by means for heat-conductive gas supply
113
and is regulated in pressure by automatic pressure control valve
115
and vacuum meter
114
for pressure monitoring at the under-surface of substrate
102
. Vacuum meter
114
is set to a pressure such as to maintain attraction of substrate
102
on to substrate holder
103
; in this case the pressure is controlled to 2000 Pa. When He gas is supplied by mass flow controller
116
, cut-off valves
140
,
141
are opened in order to raise the pressure in the gap between substrate holder
103
and substrate
102
to a set value. He gas flows from the holes in the surface of the substrate holder
103
contacting substrate
102
through He gas supply line
118
.
Next, vacuum meter
114
for pressure monitoring at the under-surface of substrate
102
controls the pressure of the heat-conductive gas to a set value by regulating the pressure by opening and closing automatic pressure control valve
115
. In the initial condition where the pressure is low, mass flow controller
116
permits a flow of He gas of 50 sccm; when the pressure rises to the set value of 2000 Pa, the flow rate of He gas drops to 30 sccm.
After this, the reaction gases CF
4
at 30 sccm and O
2
at 5 sccm are simultaneously introduced from means for reactive gas supply
130
and regulated to a pressure of 30 Pa by means for vacuum evacuation
131
. A plasma is generated by branching the high-frequency power from high-frequency power source
111
into two, these being supplied to the pair of internal electrodes
106
A and
106
B through capacitors
110
that cut off the DC voltage. The required dry etching is thus performed whilst efficiently cooling substrate
102
from the under-surface using He gas.
When plasma processing has been completed, mass flow controller
116
is stopped, cut-off valve
140
is closed, the heat-conductive gas is evacuated through an evacuation line
119
, and the pressure is lowered by fully opening automatic pressure control valve
115
until the pressure of the gap between substrate holder
103
and substrate
102
reaches the pressure in the initial condition. Substrate
102
is then lifted off from substrate holder
103
by means for pushing-up
120
.
However, there are the following problems with the above prior art construction. As mentioned above, in order to supply heat-conductive gas in a short time into the reservoir space containing the piping, heat-conductive gas is delivered by mass flow controller
116
at 50 sccm in the initial low-pressure condition, and the pressure is regulated by dropping to 30 sccm when the pressure rises to 2000 Pa. This upper limiting value of the flow rate i.e. 50 sccm is determined by considering a flow rate such that attraction between substrate holder
103
and substrate
102
is not released and a flow rate such that dust is not entrained into the gap between substrate holder
103
and substrate
102
by the gas flow.
Since the upper limiting value of the supply flow rate of the heat-conductive gas was thus restricted, there was the problem that a long time was required before the pressure of the gap between the substrate holder
103
and substrate
102
could be raised to the set value.
A further problem was that the evacuation time after completion of plasma processing was also long, owing to the large evacuation resistance of automatic pressure control valve
115
when the pressure was lowered by fully opening automatic pressure control valve
115
.
The conventional plasma processing apparatus therefore suffered from the problems of generation of dust at the under-surface of the substrate, or lowering of through-put.
It should be noted that means for heat-conductive gas supply/evacuation in respect of the gap between the substrate holder
103
and substrate
102
has been proposed in which the time required for supply of heat-conductive gas can be shortened, or it can be made possible to control the pressure to different values in different regions, by providing two or more substrate temperature control devices comprising a valve and flow rate controller. However, there is
Haraguchi Hideo
Matsuda Izuru
Hassanzadeh P.
Matsushita Electric - Industrial Co., Ltd.
Mills Gregory
Price and Gess
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