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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to plasma process system and method suitable
for etching, ashing, sputtering and CVD-processing semiconductor wafers.
2. Description of the Related Art
When plasma is generated in an air-tight process chamber to etch the
semiconductor wafer in plasma atmosphere thus generated, "voltage of
sheath" is a parameter to check etching reaction because it gives great
effect to the energy of ions. Fundamentally, it is determined by potential
V.sub.p of plasma and negative potential V.sub.DC biased to the side of
the cathode. It is therefore asked that these potentials V.sub.p and
V.sub.DC are adjusted to adjust plasma when plasma is to be generated in
the process chamber.
Conventionally, an apparatus in which high frequency power is added to one
of upper and lower electrodes and the other of them is earthed is used to
generate plasma. Another apparatus in which one of two high frequency
power sources is connected to the upper electrode and the other is
connected to the lower electrode is also used.
In any of these conventional cases, the upper and lower electrodes and the
high frequency power source arranged outside the process chamber form a
series circuit when the process chamber is regarded as a circuit element.
When plasma voltage is to be adjusted, therefore, it is difficult to
independently and freely adjust only V.sub.DC in the apparatus in which
the high frequency power source is connected only to one of the upper and
lower electrodes.
Even in the case where the high frequency power sources are connected to
the upper and lower electrodes, adjustment is conducted in a series
circuit. The high frequency power sources used, therefore, must has same
power and same capacity. This makes the apparatus large in size.
In the case where plasma is generated in the process chamber and the
semiconductor wafer is processed in plasma atmosphere thus generated,
three main steps are applied to the wafer. They are anisotropic isotropic
etching steps and a discharge step. The discharge step is intended to
discharge the charged-up electrostatic chuck. The wafer once attracted by
the electrostatic chuck, sometimes, is not released from the chuck even
when the power source is switched off. This is because load caused from
electrostatic polarization causes the electrostatic chuck to still attract
the wafer. The discharge step is therefore needed to solve this problem.
To carry out the discharge step, however, weak plasma must be generated.
The wafer is thus unnecessarily etched and damaged in this case.
On the other hand, there has been desired a system in which all of the
anisotropic and isotropic etching steps and the electrostatic chuck
discharge step can be conducted only in a process chamber.
Jpn. Pat. Appln. KOKAI Publication No. Sho 56-84476 discloses a method of
using high frequency power having a frequency lower than 10 MHz and
placing the wafer adjacent to the frequency electrode arranged on the high
voltage side (or plasma etching method of the parallel plate type). It
further discloses a cathode and anode coupling method by which power
source and earthed electrodes are switched over between them.
Jpn. Pat. Appln. KOKAI Publication No. Hei 1-253238 discloses an apparatus
in which high frequency voltage can be added from a high frequency power
source to both of upper and lower electrodes at the same time and to one
of them independently of the other by means of a changeover means.
In these conventional method and apparatus, however, all of the anisotropic
and isotropic etching steps and the discharge step cannot be conducted in
a process chamber. Every step asks a chamber in these cases. Therefore,
they occupy a large space in a clean room. Particularly when matters to be
processed become large in size like an 8-inch wafer and an LCD substrate,
an extremely large system is needed. In addition, the conventional system
has a long wafer carrying passage. This means that their throughputs are
low and that they causes so many particles and others to adhere to the
wafer.
In order to reduce the amount of particles and others adhering to the
wafer, single or plural load lock chambers are located adjacent to the
plasma etching chamber. When their internal pressures are to be returned
to normal, it usually takes a relatively long time (or about one minute,
for example) because nitrogen gas must be gradually introduced into them
to prevent particles and others from floating in them. This asks the wafer
to be kept waiting for a long time when it is to be carried into and out
of them. The throughput is thus made low.
In the conventional magnetron plasma process system, plasma is
maldistributed, because of magnetic field, in the process chamber,
particularly along the inner circumference of it, even if plasma is made
uniform by scanning magnetic field. The rim portion of the wafer is thus
charged up, thereby causing age oxide film to be dielectrically broken
down at the rim portion of the wafer. The rate of dielectric breakdown
reaches about 10% of all products and the productivity of the system is
thus made low.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a plasma process
system smaller in size and simpler in structure but capable of adjusting
negative potential V.sub.DC independently of the other.
Another object of the present invention is to provide a plasma process
system capable of applying plural different steps to the wafer in a single
process chamber and discharging the electrostatic chuck without adding any
damage and unnecessary etching to the wafer.
A further object of the present invention is to provide a plasma process
system capable of preventing particles from adhering to the wafer while
keeping the throughput higher.
A still further object of the present invention is to provide a plasma
process system capable of making the rim portion of the wafer not be
charged up to prevent gate oxide film from being dielectrically broken
down there.
According to an aspect of the present invention, there can be provided a
plasma process system for producing gas plasma in an air-tight chamber by
high frequency power to process a substrate with the gas plasma comprising
a lower electrode on which the substrate to be plasma-processed is
mounted; an upper electrode arranged above the lower electrode; a plasma
generator circuit for generating gas plasma between the upper electrode
and the lower electrode; a power source for supplying high frequency power
to the plasma generator circuit; and bias generator means for generating
negative voltage in the upper or lower electrode when high frequency power
is supplied from the power source to the upper or lower electrode; wherein
the plasma generator circuit includes transformer means for supplying a
part of high frequency power, which is supplied from the power source, to
the bias generator means.
This system includes transformer means for supplying a part of high
frequency power supplied from a power source to a bias generator circuit.
This means that plasma and bias generator circuits form no series circuit.
Therefore, the bias generator circuit can be adjusted, independently of
the plasma generator circuit, to adjust negative potential V.sub.DC.
Further, the transformer means enables a part of high frequency power
supplied from the power source to be supplied, as high frequency power, to
the bias generator circuit. Therefore, single high frequency power source
only is needed.
According to another aspect of the present invention, there can be provided
a plasma process method comprising a first step of applying anisotropic
etching to a substrate in a chamber by supplying process gas into the
chamber and adding high frequency power to a lower electrode, on which the
substrate is mounted, through electrostatic chuck means to generate
plasma; a second step of applying isotropic etching to the substrate to
remove at least etching residues, damaged layer or resist from it by
changing process gas to another and adding high frequency power to an
upper electrode in the chamber to generate plasma; and a third step of
discharging the lower electrode by stopping the supply of power to the
electrostatic chuck while changing process gas to non-oxidizing gas and
adding high frequency power to the upper electrode to such an extent that
allows weak plasma to be generated.
Additional objects and advantages of the invention will be set forth in the
description which follows, and in part will be obvious from the
description, or may be learned by practice of the invention. The objects
and advantages of the invention may be realized and obtained by means of
the instrumentalities and combinations particularly pointed out in the
appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are incorporated in and constitute a part
of the specification, illustrate presently preferred embodiments of the
invention and, together with the general description given above and the
detailed description of the preferred embodiments given below, serve to
explain the principles of the invention.
FIG. 1 is a block diagram showing the plasma process system according to a
first embodiment of the present invention partly sectioned;
FIG. 2 is a block diagram showing the plasma process system according to a
second embodiment of the present invention partly sectioned;
FIG. 3 is a block diagram showing the plasma process system according to a
third embodiment of the present invention partly sectioned;
FIG. 4 is a block diagram showing the plasma process system according to a
forth embodiment of the present invention partly sectioned;
FIG. 5 is a block diagram showing process and load lock chambers of the
plasma process system according to a fifth embodiment of the present
invention partly sectioned;
FIG. 6 is a vertically-sectioned view showing a gas nozzle in the load lock
chamber;
FIG. 7 is a graph showing results obtained relating to the number of
particles adhering to each sample wafer;
FIG. 8 is a graph showing results obtained relating to the number of
particles adhering to each sample wafer;
FIG. 9 is a view showing those positions in the load lock chamber at which
the gas nozzle is set;
FIG. 10 is a vertically-sectioned view showing the plasma process system
according to a sixth embodiment of the present invention;
FIG. 11 is a sectional view showing a part of the upper electrode in the
plasma process system enlarged; and
FIG. 12 is a sectional view showing the main portion of a test device
enlarged, said test device being used to check the dielectric breakdown of
gate oxide film.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The plasma process systems and methods according to some embodiments of the
present invention will be described with reference to the accompanying
drawings.
As shown in FIG. 1, the plasma process system 1 according to a first
embodiment of the present invention is an etching apparatus having a
spiral coil 18 arranged above a process chamber 2. The side wall and
bottom of the process chamber 2 are made of aluminium alloy and the top 2a
thereof is made of quartz. An exhaust opening 2b is formed in the bottom
of the process chamber 2 and it is communicated with exhaust means such as
the vaccum pump (not shown) through an exhaust pipe 3.
A gas inlet 2c is formed in the side wall of the process chamber 2 at the
upper end portion thereof and it is communicated with a process gas (or
etching gas) supply source (not shown) through a gas pipe 4.
A suscepter support 6 is arranged on the center portion of the process
chamber 2 with an insulating plate 5 interposed between them. The
insulating plate 5 is made of ceramics such as alumina, SiC or SiN. A
suscepter 7 is detachably mounted on the top of the suscepter support 6
and it is made of aluminium or aluminium alloy.
A cooling jacket (not shown) is formed in the suscepter support 6 and a
coolant is circulated through it. A temperature control unit (not shown)
is attached to the suscepter 7 to keep it at a desired temperature which
is in a range of -100.degree. C. to +80.degree. C.
An electrostatic chuck 8 on which a wafer w is directly mounted is arranged
on the top of the suscepter 7. It comprises a conductive layer 9 made of
electrolytic stripping copper, for example, and insulators such as
polyimide film for inserting the conductive layer 9 between them. When DC
voltage is added from a high voltage DC power source 10 to the conductive
layer 9, the wafer W is attracted and held on the top of the electrostatic
chuck 8 due to coulomb force.
One end of a lead 12 having a blocking capacitor 11 is connected to the
suscepter 7. The other end thereof is connected to a terminal 14 of a
changeover switch SW arranged on the secondary circuit of a transformer
13. Plural changeover terminals T.sub.0, T.sub.1, T.sub.2, T.sub.3,--(only
four changeover terminals T.sub.0, T.sub.1, T.sub.2 and T.sub.3, are shown
for the sake of clarity in FIG. 1) are provided on the changeover side of
the changeover switch SW and power added from the secondary circuit of the
transformer 13 to the suscepter 7 can be thus changed by the changeover
switch SW.
The changeover terminal T.sub.0 serves as an earthed one and the value of
voltage supplied through the other terminals is reduced like a step in the
order of the terminals T.sub.1, T.sub.2, T.sub.3,--. Needless to say, the
voltage supplied may be changed not like a step but continuously. Power
which is in a range of 10%-30% of power supplied through the primary
circuit of the transformer 13 can be supplied through the secondary
circuit thereof in any case.
On the other hand, power supply and earthed line 14 and 15 are connected to
the primary circuit of the transformer 13. Output and earthed sides of a
high frequency power source 17 are connected to the power supply and
earthed lines 14 and 15 through an impedance matching unit 16. The high
frequency power source 17 has a frequency of 13.56 MHz, for example, and
it can supply a frequency power of 50 to 1500 W, for example.
The spiral coil 18 is arranged above the quartz-made top 2a of the process
chamber 2. Its one end is connected to the power supply lead 14 and its
other end to the earthed lead 15.
It will be described how a semiconductor wafer W is etching-processed.
The gate valve (not shown) is opened and a dummy wafer Wd is carried into
the process chamber 2 by the carrier unit (not shown). A resist pattern
has been formed on the dummy wafer Wd. When this dummy wafer Wd is mounted
on the electrostatic chuck 8, DC voltage is added from the high voltage DC
power source 10 to the conductive layer 9 of the electrostatic chuck 8.
The dummy wafer Wd can be thus held on the electrostatic chuck 8 at a
predetermined position.
The gate valve is closed and CF.sub.4 gas is introduced into the process
chamber 2 through the gas inlet 2c. The process chamber 2 is exhausted to
0.5 Torr. High frequency power, 1000 W and 13.56 MHz, is added from the
high frequency power source 17 to the spiral coil 18 through the power
supply lead 14. Plasma is thus generated in the process chamber by high
frequency induction.
When the changeover switch SW is connected to the terminal T.sub.1, voltage
which is arranged available through the terminal T.sub.1 is added from the
secondary circuit of the transformer 13 to the suscepter 7 through the
lead 12. Negative potential is thus biased to the suscepter 7. Anisotropic
etching, therefore, is applied to the dummy wafer Wd on the electrostatic
chuck 8.
After anisotropic etching is applied to the dummy wafer Wd in this manner,
the dummy wafer Wd is checked. If any defect is found about the dummy
wafer Wd because of insufficient plasma, for example, the terminal
connected to the changeover switch SW is changed over to another one to
adjust voltage added to the suscepter 7. When voltage added is adjusted in
this manner, negative potential V.sub.DC biased to the suscepter 7 can be
adjusted. On the other hand, the adjustment of power added to the spiral
coil 18 can be attained by directly adjusting the high frequency power
source 17. After the plasma generating condition is adjusted like this,
using the dummy wafer Wd, semiconductor wafers W to be processed are
successively processed one after another in the process chamber 2.
As apparent from the above, the power itself of plasma generated in the
process chamber 2 and negative potential V.sub.DC biased to the anode can
be adjusted independently of the other by adjusting the high frequency
power source 17 and by changing the terminal of the changeover switch SW
arranged on the secondary circuit of the transformer 13.
In this case, the supply of high frequency power can be attained only
through the high frequency power source 17. In addition, the transformer
13 may have a capacity enough to supply power equal to about 10% to 30% of
power supplied from the high frequency power source 17. The transformer 13
itself can be thus made more compact.
When the changeover switch SW is connected to the earthed terminal T.sub.0,
no voltage is added from the transformer 13 to the suscepter 7. Isotropic
etching can be thus made possible. This means that different etching
processes can be achieved in the single process chamber 2.
If inactive gas is introduced into the process chamber 2 and weak plasma is
generated in it after the finish of isotropic or anisotropic etching, load
remaining on the wafer thus isotropically or anisotropically etched can be
discharged. In addition to anisotropic and isotropic etchings, therefore,
the discharging of the electrostatic chuck can be attained in the common
process chamber 2.
A second embodiment of the present invention will be described referring to
FIG. 2. Same components as those of the first embodiment will be described
on when needed.
The circuit of a plasma process system 31 according to the second
embodiment of the present invention is substantially same as that of the
above-described first embodiment. The plasma process system 31 is
different from the system 1 only in an upper space 33 in the process
chamber, and upper electrodes 35 and 36. These space 33 and upper
electrodes 35 and 36 cooperate with the lower electrode (or suscepter) 7
to form a circuit of plasma generator.
A cap 34 is arranged on the top of a chamber 32 to form the upper space 33
in the chamber 32. It is made of quartz. The upper electrode 35 is
arranged outside a side wall of it while the other upper electrode 36
outside an opposed side wall of it. They are therefore parallel plate
electrodes with the cap 34 interposed between them. One 35 of them is
connected to the power supply lead 14 and the other 36 to the earthed lead
15. A gas inlet 32c is formed just below the upper space 33.
Then wafer W will be etched as follows by the plasma process system 31.
While exhausting the chamber 32, CF.sub.4 gas is supplied into it through
the gas inlet 32c and it is adjusted to about 0.1 Torr. When high
frequency power, 1000 W and 13.56 MHz, is added to the electrode 35,
plasma is generated in the upper space 33.
When the change over switch SW is connected not to the terminal T.sub.0 but
to any of the terminals T.sub.1, T.sub.2 and T.sub.3, negative voltage is
biased to the suscepter 7 and anisotropic etching is thus applied to a
dummy wafer Wd on the electrostatic chuck 8. The dummy wafer Wd thus
etched is checked. If it has any defects, the changeover switch SW is
changed over to another terminal to adjust voltage biased to the suscepter
7. The state of plasma can be thus made suitable for the etching process.
When the high frequency power source 17 is adjusted, the power of plasma
can also be changed.
According to the second plasma process system 31, the supply of high
frequency power can be attained only through the single power source 17.
In addition, the transformer may have a capacity enough to supply power
equal to about 10% to 30% of power supplied from the high frequency power
source 17. This makes the whole of the system smaller-sized.
When the changeover switch SW is connected to the terminal T.sub.0,
isotropic etching can be applied to the wafer W. When weak plasma is
generated in the process chamber 32, load remaining on the wafer w thus
etched can be discharged. In short, the system 31 enables three different
processes such as anisotropic and isotropic etchings and load discharge to
be achieved in the single process chamber 32.
A pair of one turn coil antennas may be used as plasma generator means
instead of the parallel plate electrodes 35 and 36. Helicon wave plasma
generator of the high frequency induction type can be provided in this
case.
A plasma process system 41 according to the third embodiment of the present
invention will be described referring to FIG. 3. Same components as those
of the first and second embodiments will be described only when needed.
The circuit of this third plasma process system 41 is substantially same as
those of the first and second embodiments. A chamber 42 comprises lower
and upper halves. The lower half of the chamber 42 is made of aluminium
alloy and the upper half 44 thereof of quartz. A top cylindrical portion
44a of the upper half 44 has a diameter smaller than that of the lower
half. This cylindrical portion 44a forms therein a space 43 in which
plasma is generated.
A gas inlet 44b is formed in the top of the cylindrical portion 44a and
CF.sub.4 gas is introduced into the chamber 42 through the gas inlet 44b.
A pair of ring electrodes 46 and 47 are attached to the outer
circumference of the cylindrical portion 44a. They are separated from each
other in the vertical direction and the power supply lead 14 is connected
to the lower one 46 while the earthed lead 15 to the upper one 47.
The wafer W will be etched as follows by the third plasma process system
41.
while exhausting the chamber 42 to 0.1 Torr, CF.sub.4 gas is introduced
into it through the gas inlet 44b. When high frequency power, 1000 W and
13.56 MHz, is added to the lower ring electrode 46, gas is made plasma in
the cylindrical portion 44a. This plasma gas flows, as down flow, from the
upper space 43 onto the wafer W below. The wafer W is thus etched.
According to the plasma process system 41, the supply of high frequency
power can be attained only through the high frequency power source 17. In
addition, the transformer may have a capacity enough to supply power equal
to about 10% to 30% of power supplied from the power source 17. Therefore,
the whole of the system 41 can be smaller-sized.
A plasma process system 51 according to the fourth embodiment of the
present invention will be described with reference to FIG. 4. Same
components as those of the first through third embodiments will be
described only when needed.
The chamber 51 is a sealed container made of aluminium alloy and it is
earthed. A suscepter support 53 is arranged on its floor with an
insulating plate 52 interposed between them. A cooling jacket 54 is formed
in the suscepter support 53. Coolant introducing and exhausting pipes 55
and 56 are communicated with the cooling jacket 54. Coolant is introduced
from a coolant supply source (not shown) into the jacket 54 through the
coolant introducing pipe 55 and exhausted from it through the coolant
exhausting pipe 56.
A suscepter 57 made of aluminium alloy is detachably attached to the top of
the suscepter support 53. An electrostatic chuck 58 is mounted on the top
of the suscepter 57.
Gas passages 60 are formed in the suscepter 57, communicating with a gas
introducing pipe 59. When He gas is supplied from a gas supply unit (not
shown) into the gas passages 60 through the gas introducing pipe 59, heat
is exchanged between the suscepter support 53 and the wafer W by
introduced He gas. The wafer W on the electrostatic chuck 58 can be thus
cooled.
The electrostatic chuck 58 comprises a conductive layer 61 and polyimide
film layers between which the conductive layer 61 is interposed. The
conductive layer 61 is connected to a high voltage DC power source 63
through a supply lead 62. When DC voltage is added to the conductive layer
61, the wafer W is attracted onto the electrostatic chuck 58 due to
coulomb force. This addition of DC voltage from the power source 63 is
made by turning a switch SW.sub.1 on and off.
An insulating focus ring 64 is arranged on the top of the suscepter 57 and
along the peripheral portion thereof, enclosing the wafer W on the
electrostatic chuck 58. This focus ring 64 enables reactive ions, which
have been made plasma, to effectively act on the wafer W.
One end of a lead 65 is connected to the suscepter 57 and the other end
thereof to a terminal 66 on the lower electrode side of an electrode
changeover switch Sw.sub.2.
An upper shower electrode 71 has a plurality apertures 72 in the bottom
thereof. It is electrically insulated from the chamber 51 and at least its
face 72a which is opposed to the suscepter 57 is made of amorphous carbon
or silicon.
The upper electrode 71 is made hollow and three gas supply sources 83, 84
and 85 are communicated with the hollow portion in the upper electrode 71
through a valve 76 and pipes 77 to 80. The valve 76 is arranged in a top
gas inlet 73 of the upper electrode 71. The main pipe 77 is divided into
three pipes 78, 79 and 80. The first branching pipe 78 is communicated
with the first gas supply source 83 via a valve 81 and a mass flow
controller (MFC) 82. The second branching pipe 79 is communicated with the
second gas supply source 84 via a valve 81 and an MFC 82. The third
branching pipe 80 is communicated with the third gas supply source 85 via
a valve 81 and an MFC 82. The first gas supply source 83 contains CF.sub.4
gas therein, the second one 84 oxygen gas therein, and the third one 85
argon gas therein.
One end of a connecting lead 74 is connected to the upper electrode 71.
This lead 74 is insulated from the process chamber 51. The other end of
the lead 74 is connected to a terminal 75 on the upper electrode side of
the changeover switch SW.sub.2.
An exhaust opening 91 is formed in the bottom of the process chamber 51. It
is communicated with a vacuum pump 93 via a valve 92 and an exhaust pipe
94.
The electrode changeover system of this example will be described below.
The changeover of polarities is made by the electrode changeover switch
WS.sub.2. This switch SW.sub.2 has the upper and lower electrode terminals
75 and 66. It is also provided with terminals on earthed and power source
sides which are switched on and off to the terminals 75 and 66 on the
upper and lower electrode sides.
More specifically, earthed and power source terminals 101 and 102 are
switched on and off to the upper electrode side terminal 75 while power
source and earthed terminals 103 and 104 to the lower electrode side
terminal 66. The power source terminals 102 and 103 are connected to their
corresponding matching units 105 and 106, which are further connected to a
high frequency power source 108, which can change its output, through a
blocking capacitor 107.
The control system of this example will be described below.
The valves 76, 81, 92, MFCs 82, vacuum pump 93, DC power source switch
SW.sub.1, electrode changeover switch WS.sub.2 and high frequency power
source 107 are controlled by a controller 111. This controller 111 has
three operation modes, that is, RIE (reactive ion etching), PE (plasma
etching) and discharge modes, and it controls the abovementioned
components responsive to the mode switched. The RIE mode is intended to
add RF power to the suscepter 57. The PE mode is intended to add RF power
to the upper electrode 71. The discharge mode is intended to generate weak
plasma under the PE mode to discharge the charged surface of the
electrostatic chuck 58 through the impedance of this plasma.
It will be described how a wafer W is etched.
The controller 111 is set to carry out the RIE mode. The semiconductor
wafer W on which a resist pattern has been formed is mounted on the
electrostatic chuck 58. When the valves 76 and 81 are opened and CF.sub.4
gas is supplied to the upper electrode 71, gas is uniformly discharged
onto the wafer w through the apertures 72 of the upper electrode 71. The
process chamber 51 is kept about 0.5 Torr.
In the section of the electrode changeover switch Sw.sub.2, the controller
111 keeps the upper electrode side terminal 75 connected to the earthed
terminal 101 and the lower electrode side terminal 66 connected to the
power source terminal 103. When the power source 108 is switched on, high
frequency power, 1 kw and 13.56 MHz, set by the controller 111 is added to
the lower electrode 57. Anisotropic etching is thus applied to the wafer W
under the RIE mode.
when anisotropic etching is finished, the controller 111 is set to carry
out the PE mode. The high frequency power source 57 is switched off and
CF.sub.4 gas remaining in the process chamber 51 is then exhausted outside
through the exhaust opening 91. The controller 111 causes O.sub.2 gas to
be supplied from the O.sub.2 gas bomb 84 into the process chamber 51,
which is kept about 1 Torr.
In the section of the electrode changeover switch Sw.sub.2, the controller
111 keeps the upper electrode side terminal 75 connected to the power
source terminal 102 and the lower electrode side terminal 66 connected to
the earthed terminal 104 (which is reverse to the state shown in FIG. 4).
When the power source 108 is switched on, high frequency voltage which is
set to have a power value of 400 to 800 W by the controller 111 is added
to the upper electrode 71. Isotropic etching is thus applied to the wafer
w to remove etching residues, damaged layer and resist film from it.
When isotropic etching is finished, the controller 111 is set to carry out
the discharge mode. The high frequency power source 108 is switched off
and O.sub.2 gas remaining in the process chamber 51 is then exhaust
outside through the exhaust opening 91. The controller 111 causes Ar gas
to be supplied from the Ar gas bomb 85 into the process chamber 51, which
is kept about 2 Torr. The switch SW.sub.1 is turned off to stop the supply
of DC voltage from the high frequency DC power source 63 to the
electrostatic chuck 58.
On the other hand, the electrode changeover switch Sw.sub.2 is kept same as
under the PE mode. When the high frequency power source 107 is switched
on, high frequency power, 80 W, set by the controller 11 is added to the
upper electrode 71. Weak plasma of inactive gas is thus generated. Load
remaining on the electrostatic chuck 58 is discharged through this weak
plasma of inactive gas. The electrostatic chuck 58 (or charged-up surface
thereof) can be thus discharged.
When the electrostatic chuck 58 is discharged in this manner, the high
frequency power source 108 is switched off and Ar gas remaining in the
process chamber 51 is exhausted outside. A new wafer W is exchanged with
the processed one and the controller 111 is again set to carry out the RIE
mode. The new wafer W can be thus processed in the same way as described
above.
According to the fourth embodiment of the present invention, three
different processes such as the isotropic and anisotropic etching and
discharge ones can be applied to a sheet of the semiconductor wafer in a
same process chamber. The whole of the system can be thus smaller-sized.
In addition, the time needed to process the wafer can be shortened and the
throughput can be enhanced. Further, the productivity can be increased
because the amount of particles adhering to the wafer W can be reduced to
a greater extent.
Those related components such as the carrier units and the auxiliary vacuum
chambers may be controlled by the controller 111 in addition to the
above-mentioned ones.
The modes which are carried out by the controller 111 are not limited to
the above-mentioned three ones. The controller 111 can also be set to
carry out those modes which meet the kinds and steps of processes
employed. In addition, control modes can be set relative to those various
process apparatuses such as CVD, ashing and sputtering ones, for example,
in each of which various different treatments are applied to the matter to
be processed.
Even in the case of the above-described controller which has only three
modes, it can be arranged that anisotropic and isotropic etching processes
are repeated after they are once conducted and that discharge process is
then conducted. It can also be arranged that anisotropic etching process
is carried out after isotropic etching process and that discharge process
is then carried out.
In any cases, these processes can be realized only by changing the
controller program a little while leaving the mechanical and electrical
components of the system itself unchanged.
In the above-described plasma process system, plasma and bias generator
mean do not form a series circuit. Therefore, the power of plasma and
negative potential V.sub.DC biased to the cathode can be adjusted
independently of the other.
In addition, power supplied to the bias generator means is a part of that
power which is supplied from the high frequency power supply means through
the transformer means. This enables only the high frequency power source
to be used.
Further, power added to the cathode may be equal to 10% to 30% of that
power which is added to the plasma generator means. The rated capacity of
the transformer means can be thus made smaller and the whole of the system
can be made more compact.
A fifth embodiment of the present invention will be described referring to
FIGS. 5 through 9.
As shown in FIG. 5, this plasma process system includes etching and load
lock chambers 301 and 302. A gate valve 304 is arranged between the
etching 301 and the load lock chamber 302 to shield a wafer carrying
passage 303. When the gate valve 304 is opened, both of the chambers 301
and 302 are communicated with each other through the wafer carrying
passage 303. The etching chamber 301 is a cylindrical housing made of
aluminium alloy. The load lock chamber 302 is a housing like a rectangular
parallel-epiped made of aluminium alloy. The volume of the load lock
chamber 302 is smaller than that of the etching chamber 301. The load lock
chamber 302 for a 6-inch wafer, for example, has a volume of about 10
liters. It has an opening 305 through which the wafer W is carried from
outside into it. A gate valve 306 is attached to the opening 305. An
auto-loader 318 is located outside and adjacent to the gate valve 306.
A lower electrode 308 is arranged in the etching chamber 301. The wafer W
is mounted on the lower electrode 308. A coolant circulating passage 309
through which helium gas is circulated is formed in the lower electrode
308. Pipes 332 and 333 are connected to the coolant circulating passage
309. Coolant is circulated through these passage 309 and pipes 332, 333 to
cool the wafer W on the lower electrode 308.
A clamp ring 311 is supported by plural rods 312 and moved up and down by
cylinders 313. When it is moved down, it pushes the rim portion of the
wafer W against the lower electrode 308.
Further, an upper electrode 314 is arranged above the lower one 308. It is
opposed to and separated from the lower electrode 308. It has a plurality
of apertures 314a in its bottom. These apertures 314a are distributed in
the bottom of the upper electrode 314 at a certain pitch interval. A gas
supply pipe 315 is connected to the top of the upper electrode 314 to
supply process gas from a gas supply source (not shown) into the etching
chamber 301 through it. An exhaust pipe 316 extends from the lower portion
of the side wall of the etching chamber 301.
A carrier unit 317 is arranged in the auxiliary vacuum chamber 302 and the
wafer W is carried between the carrier unit 317 and the auto-loader 318.
An exhaust pipe 319 is connected to the bottom of the auxiliary vacuum
chamber 302. The chamber 302 is thus exhausted through the pipe 319. A gas
nozzle 321 is arranged above the carrier unit 317 in the auxiliary vacuum
chamber 302. It is communicated with a gas supply source 341 through a
pipe 320. A regulator 342 and a valve 343 are attached to the pipe 320.
These gas supply source 341, regulator 342 and valve 343 are controlled by
a controller 111.
The gas nozzle 321 and its making manner will be described, referring to
FIG. 6.
The gas nozzle 321 comprises a cylindrical porous body 322, a pair of end
plates 323 and 324 fixed to both ends of the body 322, and a seal member
interposed between one end of the porous body 322 and the end plate 323.
The front end portion of the pipe 320 is inserted into the gas nozzle 321
along the longitudinal center line thereof and it has one or two lines of
apertures 320 which are arranged at an equal pitch interval. The seal
member 327 is made of flexible material. The pipe 320 and the end plates
323, 324 are made of stainless steel and the pipe 320 is fixed to the end
plates 323 and 324 at welding points 325 and 326.
It is desirable that ceramics sinter such as alumina, silicon nitride and
silicon carbide or metal sinter such as aluminium alloy is used as the
porous body 322. The average dia | | |
