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BACKGROUND OF THE INVENTION
The present invention relates to plasma processing method and apparatus
used for dry etching and plasma CVD etc.
In recent years, to effect processing or the like on a semiconductor
element at a high aspect ratio by dry etching technique or effect
embedding or the like at a high aspect ratio by plasma CVD technique
coping with developing dimensional fineness of semiconductor elements, it
has been required to effect plasma processing in higher vacuum.
For instance, in the case of dry etching, when a high density plasma is
generated in high vacuum, there is a reduced possibility of collision
between ions and ions or other neutral gas particles in an ion sheath
formed on a substrate surface, and therefore, directions of the ions are
aligned toward the substrate surface. Furthermore, because of a high
degree of electrolytic dissociation, there results a high incident
particle flux ratio of ions arriving at the substrate to neutral radicals.
For the above-mentioned reasons, etching anisotropy is improved by
generating a high density plasma in high vacuum, thereby allowing
processing to be achieved at a high aspect ratio.
Furthermore, in the case of plasma CVD, when a high density plasma is
generated in high vacuum, an effect of embedding and flattening a fine
pattern can be obtained by a sputtering effect with ions, thereby allowing
embedding to be achieved at a high aspect ratio.
As one of plasma processing apparatuses capable of generating high density
plasmas in high vacuum, there is a high frequency induction type plasma
processing apparatus which generates plasma inside a vacuum vessel by
applying a high frequency voltage to a discharge coil. The plasma
processing apparatus of this type generates a high frequency magnetic
field inside the vacuum vessel and accelerates electrons by generating an
induction field inside the vacuum vessel by the high frequency magnetic
field to generate plasma.
A known high frequency induction type plasma processing apparatus, has a
planar spiral discharge coil 13 as shown in FIG. 15. The planar spiral
discharge coil 13 is fixed on a surface opposite to a substrate 14. In
FIG. 15, when an appropriate gas is introduced from an introduction inlet
20 into a vacuum vessel 15 while gas inside the vacuum vessel 15 is
discharged from a discharge outlet 21 and a high frequency voltage is
applied to the planar spiral discharge coil 13 by a discharge coil
connected to high frequency power source 16 with the vacuum vessel 15 kept
internally at an appropriate pressure, a plasma is generated inside the
vacuum vessel 15 to allow the substrate 14 placed on a lower electrode 17
to be subjected to plasma processing such as etching, deposition, and
surface improvement. In this case, as shown in FIG. 15, an ion energy
reaching the substrate 14 can be controlled by additionally applying a
high frequency voltage to the lower electrode 17 from a lower electrode
using high frequency power source 18.
However, with the system shown in FIG. 15 a plasma density in-plane
distribution is hardly controlled since the planar spiral discharge coil
13 is fixed on the surface opposite to the substrate 14. This will be
described in detail below.
As a principal control parameter with regard to the generation of plasma,
there can be enumerated gas type, gas flow rate, pressure, high frequency
powers, and high frequency power frequencies. In a case where an identical
discharge coil is used, the plasma density in-plane distribution varies
when these control parameters are varied. An example of the above is shown
in FIGS. 16A and 16B. FIG. 16A shows a measurement result obtained by
measuring a plasma density distribution on a line parallel to the
substrate by a Langmuir probe in the case where the gas type is argon, the
gas flow rate is 30 SCCM, the pressure is 5 mTorr and the high frequency
power is 1000 W. Uniformity within a range in diameter of 200 mm was a
satisfactory value of .+-.2.3%. However, the plasma density distribution
in the case where the pressure is 50 mTorr and the other conditions are
same results as shown in FIG. 16B, when the uniformity within the range in
diameter of 200 mm was .+-.8.8%.
In the case of dry etching, it is sometimes desired to etch a variety of
thin films by means of an identical plasma processing apparatus. In such a
case, the control parameters such as the gas type and pressure also differ
depending on the thin film that is desired to be etched. In the prior art
plasma processing apparatus, a certain thin film can be uniformly etched,
however, the etching uniformity cannot always be obtained for other thin
films. In regard to plasma CVD, the same issue exists.
Furthermore, in the case of dry etching, are varied the control parameters
in the course of processing when processing one substrate. For example, in
polysilicon etching, there is a process of etching a natural oxide film
formed on a surface of polysilicon, and this is followed by a process of
etching the polysilicon. These two processes are performed within an
identical plasma processing apparatus. However, they have different
control parameters, and normally the gas type is changed. In such a case,
there arises the issue that no substrate in-plane uniformity of etching
characteristics such as etching rate and etching form cannot be obtained
when varied plasma density in-plane distributions are provided in the
first process and the second process. Not limited to the polysilicon
etching, it has been known to change the control parameters in the course
of processing one substrate in many plasma processing cases by dry etching
and plasma CVD. However, when such a process is performed by means of the
prior art plasma processing apparatus as shown in FIG. 15, the substrate
in-plane uniformity of the plasma processing cannot be obtained.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a plasma
processing method and apparatus having an excellent controllability of a
plasma density in-plane distribution.
In accomplishing these and other aspects, according to a first aspect of
the present invention, there is provided a plasma processing method for
processing a substrate by placing the substrate on an electrode in a
vacuum chamber, introducing a gas into the vacuum chamber while
discharging from inside the vacuum chamber gas, applying a high frequency
voltage to a spiral discharge coil while keeping the vacuum chamber
internally at a pressure to generate a plasma inside the vacuum chamber.
At least one of the control parameters of gas type, gas flow rate,
pressure, magnitudes of high frequency powers applied to the coil and the
electrode, and their high frequency power frequencies is varied while the
substrate is processed.
The method comprises a step of allowing a plasma density in-plane
distribution to be controlled in accordance with a timing of varying any
of the control parameters.
According to a second aspect of the present invention, there is provided a
plasma processing apparatus comprising:
an electrode for receiving thereon a substrate in a vacuum chamber;
a spiral discharge coil for generating a plasma inside the vacuum chamber
by applying a high frequency voltage to the discharge coil; and
a device for changing a shape of the spiral discharge coil so that a pitch
in a diameter direction of the coil is partially changed, thereby allowing
a plasma density in-plane distribution to be controllable.
According to a third aspect of the present invention, there is provided a
plasma processing method for forming a film on a substrate by placing the
substrate on an electrode in a vacuum chamber, introducing a gas into the
vacuum chamber while discharging inside gas, applying a high frequency
voltage to a spiral discharge coil while keeping the vacuum chamber
internally at a pressure to generate a plasma inside the vacuum chamber.
The method comprises the steps of:
varying at least one of control parameters of gas type, gas flow rate,
pressure, magnitudes of high frequency powers applied to the coil and the
electrode, and their high frequency power frequencies while the substrate
is processed; and
thereby changing a shape of the spiral discharge coil so that a uniformity
of film forming rate obtained before and after varying the control
parameter is compensated in accordance with a timing of varying the
control parameter in a course of forming the film.
According to a fourth aspect of the present invention, there is provided a
plasma processing method for etching a substrate by placing the substrate
on an electrode in a vacuum chamber, introducing a gas into the vacuum
chamber while discharging inside gas, applying a high frequency voltage to
a spiral discharge coil while keeping the vacuum chamber internally at a
pressure to generate a plasma inside the vacuum chamber.
The method comprises the steps of:
varying at least one of control parameters of gas type, gas flow rate,
pressure, magnitudes of high frequency powers applied to the coil and the
electrode, and their high frequency power frequencies while the substrate
is processed; and
thereby changing a shape of the spiral discharge coil so that a uniformity
of etching rate obtained before and after varying the control parameter is
compensated in accordance with a timing of varying the control parameter
in a course of etching.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other aspects and features of the present invention will become
clear from the following description taken in conjunction with the
preferred embodiments thereof with reference to the accompanying drawings,
in which:
FIG. 1 is a partial sectional view showing the construction of a plasma
processing apparatus according to a first embodiment of the present
invention;
FIG. 2 is a plan view showing the details of a planar spiral discharge coil
of the first embodiment;
FIG. 3 is a graph showing an in-plane distribution characteristic of a film
forming rate according to the first embodiment;
FIG. 4 is a graph showing an in-plane distribution characteristic of the
film forming rate of the first embodiment;
FIG. 5 is a graph showing an in-plane distribution characteristic of the
film forming rate of the first embodiment;
FIG. 6 is a graph showing an in-plane distribution characteristic of the
film forming rate of the first embodiment;
FIGS. 7A, 7B, and 7C are sectional views showing film forming processes of
the first embodiment;
FIG. 8 is a graph showing in-plane distributions of film thickness in the
case where the shape of the planar spiral discharge coil is changed and a
film forming rate in the case where the shape of the planar spiral
discharge coil is not changed in the first embodiment;
FIG. 9 is a graph showing an in-plane distribution characteristic of an
etching rate according to a second embodiment of the present invention;
FIG. 10 is a graph showing an in-plane distribution characteristic of the
etching rate of the second embodiment;
FIG. 11 is a graph showing an in-plane distribution characteristic of the
etching rate of the second embodiment;
FIG. 12 is a graph showing an in-plane distribution characteristic of the
etching rate of the second embodiment;
FIG. 13 is a plan view showing the construction of a planar spiral
discharge coil according to a third embodiment of the present invention;
FIG. 14 is a plan view showing the construction of a planar spiral
discharge coil according to a fourth embodiment of the present invention;
FIG. 15 is a perspective view of a prior art plasma processing apparatus;
FIGS. 16A and 16B are characteristic charts showing plasma density
distributions of the prior art;
FIG. 17 is a perspective view showing the construction of a
three-dimensional spiral discharge coil according to a fifth embodiment of
the present invention;
FIG. 18 is a partial sectional view showing the construction of a
three-dimensional spiral discharge coil according to a sixth embodiment of
the present invention;
FIG. 19 is an enlarged sectional view of a part of the discharge coil of
FIG. 18;
FIG. 20 is a plan view showing a part of the construction of a spiral
discharge coil according to a seventh embodiment of the present invention;
FIG. 21 is a plan view showing a part of the construction of a spiral
discharge coil according to an eighth embodiment of the present invention;
FIG. 22 is a plan view showing a part of the construction of a spiral
discharge coil according to a ninth embodiment of the present invention;
and
FIG. 23 is a plan view showing a part of the construction of a spiral
discharge coil according to a tenth embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Before the description of the present invention proceeds, it is to be noted
that like parts are designated by like reference numerals throughout the
accompanying drawings.
A first embodiment of the present invention will be described with
reference to FIGS. 1 through 8 taking formation of a silicon oxide film by
means of the plasma CVD method as an example.
In FIG. 1, a planar spiral discharge coil 1 is provided on a surface
opposite to a substrate 8. A center side end 2 of the planar spiral
discharge coil 1 is connected to a rotary shaft 4 of a stepping motor 3
which serves as a rotary actuator. The stepping motor 3 is driven under
the control of a controller 100 and the controller 100 controls the plasma
processing based on control parameters stored in a memory 101. The control
parameters are composed of gas type, gas flow rate, pressure, high
frequency power applied to the coil 1, high frequency power applied to a
lower electrode 7, and high frequency power frequencies of the high
frequency powers. A plasma density in-plane distribution is controlled in
accordance with the timing of varying at least one of the control
parameters.
By introducing an appropriate gas from an introduction inlet 20 into a
vacuum vessel 5 while discharging inner gas from a discharge outlet 21 and
applying a high frequency voltage to the planar spiral discharge coil 1 by
means of a discharge coil connected to high frequency power source 6 while
keeping the vacuum vessel 5 internally at an appropriate pressure, a
plasma is generated inside the vacuum vessel 5 to allow the substrate 8
placed on a lower electrode 7 to be subjected to plasma processing such as
etching, deposition, and surface improvement.
In the above case, by additionally applying a high frequency voltage to the
lower electrode 7 from a lower electrode use high frequency power source
9, ion energy reaching the substrate 8 can be controlled.
As shown in FIG. 2, the planar spiral discharge coil 1 has a structure such
that its outer peripheral side end 10 is fixed, however, the other portion
thereof is not fixed so that the planar spiral discharge coil 1 can change
its shape when its center side end 2 is turned.
On both sides of a plurality of portions in the lengthwise direction of the
planar spiral discharge coil 1 is oppositely provided a pair of guides 11.
The and the planar spiral discharge coil 1 can take a shape as indicated
by a solid line in FIG. 2 (this shape will be referred to as an A-shape
hereinafter) and a shape as indicated by a dashed line in FIG. 2 (this
shape will be referred to as a B-shape hereinafter) depending on the
rotary angle of the rotary shaft 4 of the stepping motor 3.
By turning the rotary shaft 4 of the stepping motor 3 clockwise by an angle
of 150.degree. from the A-shape of the planar spiral discharge coil 1, the
shape of the planar spiral discharge coil 1 changes into the B-shape. In
the case of the A-shape, an interval between mutually adjacent portions of
the conductive wire constituting the planar spiral discharge coil 1, on
the other words, a pitch in the diameter direction of the discharge coil 1
is smaller in the center portion of the planar spiral discharge coil 1
than at the peripheral portion as compared with the B-shape. When the
control parameter values are same, the plasma density in the center
portion of the planar spiral discharge coil 1 is made relatively greater
than in the peripheral portion.
FIG. 3 shows an in-plane distribution of a film forming rate when a silicon
oxide film is formed on the substrate 8 with the planar spiral discharge
coil 1 made to have the B-shape. The control parameters of gas type, gas
flow rate, pressure, high frequency power applied to the coil 1, high
frequency power applied to the lower electrode 7, and their high frequency
power frequencies are SiH.sub.4 /O.sub.2 /Ar=5/10/50 sccm, 5 mTorr, 1500
W, 800 W, and 13.56 MHz, respectively.
As is apparent from FIG. 3, the in-plane distribution of the film forming
rate is satisfactory, and its value was 1500 .ANG./min.+-.1.3%.
The above film forming conditions are the conditions for obtaining the
effect of embedding and flattening a fine pattern taking advantage of a
sputtering effect by Ar ions through incorporation of Ar into a reaction
gas. When performing the embedding of a fine pattern, the film forming
condition is sometimes changed into a high speed film forming condition by
stopping the supply of Ar in the course of processing. FIG. 4 shows an
in-plane distribution of the film forming rate when a silicon oxide film
is formed on the substrate 8 with the planar spiral discharge coil 1 made
to have the A-shape. The control parameters of gas type, gas flow rate,
pressure, high frequency power applied to the coil 1, high frequency power
applied to the lower electrode 7, and their high frequency power
frequencies were SiH.sub.4 /O.sub.2 =15/30 sccm, 5 mTorr, 1500 W, 100 W,
and 13.56 MHz, respectively. As is apparent from FIG. 4, the in-plane
distribution of the film forming rate is satisfactory, and its value was
5000 .ANG./min.+-.1.0%.
For the sake of comparison, FIG. 5 shows an in-plane distribution of the
film forming rate when a silicon oxide film is formed on the substrate 8
under the embedding and flattening conditions with the planar spiral
discharge coil 1 made to have the A-shape.
The control parameter values are the same as those in the case where the
result shown in FIG. 3 is obtained. As is apparent from FIG. 5, when the
planar spiral discharge coil 1 has the A-shape, the plasma density is high
in the center portion of the substrate 8, and conversely the plasma
density is low in the peripheral portion of the substrate 8. Therefore,
the sputtering rate is greater in the center portion of the substrate 8,
while the film forming rate is greater in the peripheral portion of the
substrate 8. The film forming rate with its uniformity was 1400
.ANG./min.+-.3.7%. Further, FIG. 6 shows an in-plane distribution of the
film forming rate when a silicon oxide film is formed on the substrate 8
with the planar spiral discharge coil 1 having the B-shape. The control
parameter values are the same as those in the case where the result shown
in FIG. 4 is obtained.
As is apparent from FIG. 6, when the planar spiral discharge coil 1 has the
B-shape, the plasma density is low in the center portion of the substrate
8, and conversely the plasma density is high in the peripheral portion of
the substrate 8. Therefore, decomposition of the reaction gas is promoted
more in the peripheral portion, and thus, the film forming rate is made
greater in the peripheral portion. The film forming rate with its
uniformity was 4900 .ANG./min.+-.2.8%.
From the above results, in order to perform processing with satisfactory
uniformity in regard to both the embedding and flattening conditions and
the high speed film forming condition, it can be found best to perform the
processing with the planar spiral discharge coil made to have the B-shape
when using the embedding and flattening conditions, and to perform the
processing with the planar spiral discharge coil made to have the A-shape
when using the high speed film forming condition.
Therefore, when forming a silicon oxide film 23 on the surface of the
substrate 8 on which a wiring layer 22 having a step height of 8000 .ANG.
is formed as shown in FIG. 7A, the silicon oxide film 23 is deposited for
four minutes under the embedding and flattening conditions with the shape
of the planar spiral discharge coil 1 having the B-shape. When the silicon
oxide film is deposited up to a thickness of 6000 .ANG. (=75% of the step
height) as shown in FIG. 7B, the control parameters are varied. In
accordance with this timing, the shape of the planar spiral discharge coil
1 is made to have the A-shape, and then, the silicon oxide film is
deposited for two minutes under the high speed film forming condition with
the planar spiral discharge coil 1 having the A-shape to form a silicon
oxide film having a thickness of 10400 .ANG. as shown in FIG. 7C. As a
result, the film thickness with its uniformity was a satisfactory value of
1.6 .mu.m.+-.1.1%. The resulting in-plane distribution of the film
thickness in this case is indicated by a characteristic curve "A .fwdarw.
B" in FIG. 8. In regard to the timing of changing the control parameters,
a satisfactory result was obtained approximately in the range of 60% to
100% of the step height.
For the sake of comparison with the case of the characteristic curve "A
.fwdarw. B", a film thickness distribution in a case where a silicon oxide
film is deposited for four minutes under the embedding and flattening
conditions with the planar spiral discharge coil 1 kept in the B-shape,
thereafter the control parameters are varied, and a silicon oxide film is
deposited under the high speed film forming condition is indicated by a
characteristic curve "B .fwdarw. B" in FIG. 8. In this case, the film
thickness with its uniformity was 1.6 .mu.m.+-.2.3%.
The above embodiment has been described by exemplifying the case where the
control parameters are varied only once during the course of the
processing, whereas the control parameters are sometimes changed a
plurality of times in the course of the processing. In this case, the
shape of the planar spiral discharge coil is changed as needed so that the
uniformity of the film forming rate in the plane of the substrate obtained
before and after varying each control parameter is compensated.
In the above embodiment, the plasma processing apparatus constructed so
that the planar spiral discharge coil 1 is allowed to take any of the two
types of the A-shape and the B-shape is shown as an example, however, the
planar spiral discharge coil may have a construction capable of taking any
of three or more shape types.
A second embodiment of the present invention will be described with
reference to FIGS. 1, 2 and 9 through 12 taking etching of a silicon oxide
film by means of the dry etching method as an example. Regarding FIGS. 1
and 2, they are provided for expressing the same things as those stated in
the first embodiment, and therefore, no description is provided therefor
herein.
FIG. 9 shows an in-plane distribution of an etching rate when a substrate 8
provided with a full surface silicon oxide film is etched with the planar
spiral discharge coil 1 made to have the A-shape. The control parameters
of gas type, gas flow rate, pressure, high frequency power applied to the
coil 1, high frequency power applied to the lower electrode 7, and their
high frequency power frequencies are C.sub.4 F.sub.8 /H.sub.2 =50/15 sccm,
50 mTorr, 1000 W, 300 W, and 13.56 MHz, respectively. As is apparent from
FIG. 9, the in-plane distribution of the etching rate was satisfactory,
and its value was 6500 .ANG./min.+-.1.5%.
FIG. 10 shows an in-plane distribution of the etching rate when the shape
of the planar spiral discharge coil 1 has the B-shape and a silicon oxide
film on the substrate 8 provided with a pattern of a number of holes each
having a diameter of 0.5 .mu.m is etched (its resist is provided with a
window so that only the inside of the holes can be etched). The higher the
pressure is, the greater the etching rate is. Therefore, in the case of
full surface etching, the etching was performed at a relatively high
pressure of 50 mTorr. However, when etching minute holes, the resulting
shape through the processing will worsen if the pressure is great.
Furthermore, the probability of reach of ions to the bottom of the holes
reduces according as the etching progresses, and therefore, the etching
rate reduces. Therefore, when etching a substrate having a hole pattern,
the control parameters of gas type, gas flow rate, pressure, high
frequency power applied to the coil 1, high frequency power applied to the
lower electrode 7, and their high frequency power frequencies were C.sub.4
F.sub.8 /H.sub.2 =40/12 sccm, 5 mTorr, 1000 W, 300 W, and 13.56 MHz,
respectively. As is apparent from FIG. 10, the in-plane distribution of
the etching rate was satisfactory, and its value was 4500
.ANG./min.+-.0.9%.
For the sake of comparison, FIG. 11 shows an in-plane distribution of the
etching rate when the substrate 8 provided with the full surface silicon
oxide film is etched with the planar spiral discharge coil 1 made to have
the B-shape. The control parameter values are the same as those in the
case where the result shown in FIG. 9 is obtained. As is apparent from
FIG. 11, when the planar spiral discharge coil 1 has the B-shape, the
plasma density is low in the center portion of the substrate, and
conversely the plasma density is high in the peripheral portion of the
substrate. Therefore, the in-plane distribution of the etching rate was
worsened as compared with the case of FIG. 9. The etching rate with its
uniformity was 6100 .ANG./min.+-.9.7%.
Further, FIG. 12 shows an in-plane distribution of the etching rate when
the substrate 8 provided with a pattern of a number of holes each having a
diameter of 0.5 .mu.m is etched with the planar spiral discharge coil 1
has the A-shape. The control parameter values are the same as those in the
case where the result shown in FIG. 10 is obtained. As is apparent from
FIG. 12, when the planar spiral discharge coil 1 has the A-shape, the
plasma density is high in the center portion of the substrate, and
conversely the plasma density is low in the peripheral portion of the
substrate. Therefore, the in-plane distribution of the etching rate was
worsened as compared with the case of FIG. 10. The etching rate with its
uniformity was 4300 .ANG./min.+-.6.8%.
From the above results, in order to effect the etching process with
satisfactory uniformity on both the substrate provided with the full
surface silicon oxide film and the substrate provided with the hole
pattern, it can be considered best to perform the processing with the
planar spiral discharge coil having the A-shape when processing the
substrate provided with the full surface silicon oxide film, and perform
the processing with the planar spiral discharge coil having the B-shape
when processing the substrate provided with the hole pattern. With the
plasma processing apparatus used in the present embodiment, the above was
able to be achieved easily.
A third embodiment of the present invention will be described with
reference to FIGS. 1 and 2 taking etching of a multi-layer film comprised
of a tungsten silicide film and a polysilicon film according to the dry
etching method as an example. Regarding FIGS. 1 and 2, they are provided
for expressing the same things as those stated in the first embodiment,
and therefore, no description is provided therefor herein.
With the planar spiral discharge coil 1 having the A-shape, the tungsten
silicide film which is the upper layer film of the multi-layer film
comprised of the tungsten silicide film and the polysilicon film and is
patterned with a resist on a substrate is etched under the following
conditions.
The control parameters of gas type, gas flow rate, pressure, high frequency
power applied to the coil 1, high frequency power applied to the lower
electrode 7, and their high frequency power frequencies are CF.sub.4
/SF.sub.6 =15/15 sccm, 25 mTorr, 400 W, 200 W, and 13.56 MHz,
respectively. The in-plane distribution of the etching rate was
satisfactory, and its value was 2500 .ANG./min.+-.2.5%.
Subsequently, the planar spiral discharge coil 1 is moved to the B-shape in
the proximity of an etching terminating point of the tungsten silicide
film, and the polysilicon film which is the lower layer film was etched
under the following conditions. The control parameters of gas type, gas
flow rate, pressure, high frequency power applied to the coil 1, high
frequency power applied to the lower electrode 7, and their high frequency
power frequencies are Cl.sub.2 /HCl=30/70 sccm, 10 mTorr, 400 W, 150 W,
and 13.56 MHz, respectively. The in-plane distribution of the etching rate
was satisfactory, and its value was 2700 .ANG./min.+-.2.0%.
For the sake of comparison, the multi-layer film comprised of the tungsten
silicide film and the polysilicon film was etched with the planar spiral
discharge coil 1 kept in the A-shape. As a result, the in-plane
distribution of the etching rate of the polysilicon film was 2600
.ANG./min.+-.8.5%. It is to be noted that the etching was effected under
the conditions that the control parameters of gas type, gas flow rate,
pressure, high frequency power applied to the coil 1, high frequency power
applied to the lower electrode 7, and their high frequency power
frequencies were respectively CF.sub.4 /SF.sub.6 =15/15 sccm, 25 mTorr,
400 W, 200 W, and 13.56 MHz up to the proximity of the terminating point
of the etching of the tungsten silicide film, and thereafter the etching
was effected by varying the control parameter values to Cl.sub.2
/HCl=30/70 sccm, 10 mTorr, 400 W, 150 W, and 13.56 MHz, respectively.
The aforementioned embodiments have been described in the example where the
silicon oxide film is formed, the example where the substrate provided
with the full surface silicon oxide film and the substrate provided with
the hole pattern are etched, and the example where the multi-layer film
comprised of the tungsten silicide film and the polysilicon film are
etched. However, the plasma processing is not limited to these, and it can
be also applied to the etching of a variety of other thin films, CVD and
so forth.
Furthermore, in each of the aforementioned embodiments, there is
exemplified the plasma processing apparatus having the mechanism for
turning the center axis of the planar spiral discharge coil relative to
the peripheral end of the coil. However, the means for changing the shape
of the planar spiral discharge coil is not limited to this. For example,
as shown in FIG. 13, a mechanism for switching between coil taps 12a
through 12d provided at the planar spiral discharge coil 1 may be used. In
FIG. 13, comparing a case where the coil taps 12a and 12c are
short-circuited when each other with a switch 72 is turned off and a
switch 71 is turned on and a case where the coil taps 12b and 12d are
short-circuited with each other when the switch 72 is turned on and a
switch 71 is turned off, the discharge coil has a greater density in its
peripheral portion as a substantial discharge coil in the case where the
coil taps 12a and 12c are short-circuited with each other.
In each of the aforementioned embodiments, there is exemplified the plasma
processing apparatus in which the planar spiral discharge coil is
constructed so that it can assume any of the two types of the A-shape and
the B-shape. However, the planar spiral discharge coil may be constructed
so that it can assume any of three or more shape types.
In each of the aforementioned embodiments, the planar spiral discharge coil
201 may have a multi-coil spiral shape comprised of planar spiral
discharge coil elements 1a, 1b, 1c, and 1d as shown in FIG. 14. When such
a coil is used, as described in the embodiments, it is acceptable to use
the mechanism for turning the center axis of the planar spiral discharge
coil 201 relative to the peripheral end of the coil 1 or the mechanism
such as switches for switching between the coil taps provided at the
discharge coil 201. Although not shown in FIG. 14, the peripheral ends of
the coils are earthed or grounded.
The application of the present invention is not limited to the planar
spiral discharge coil but the present invention can be applied to a
discharge coil having a three dimensional shape as shown in FIG. 17 as an
example. According to a fifth embodiment of the present invention, a
discharge coil 31 in FIG. 17 has an approximately bell-shaped
configuration in three dimensions and the center portion 32 of the coil 31
is rotated by the rotary shaft 4 of the stepping motor 3 so as to change
the pitch in the diameter direction of the coil 31 with the planar shape
of the coil 31 being the same as that of FIG. 14.
According to a sixth embodiment of the present invention, FIG. 18 shows a
spiral discharge coil 41 capable of forming both a planar spiral shape and
an inverted approximately bell-shaped configuration in three dimensions.
The center portion 42 of the coil 41 is rotated by the rotary shaft 4 of
the stepping motor 3 so as to change the pitch in the diameter direction
of the coil 41 and change the three-dimensional shape. As shown in FIG.
19, wedge members 44 each of which has an inclined surface 44a are
arranged at suitable intervals (e.g. 45 degrees) around the coil 41 with
each of the wedge members 44 capable of moving along a diameter of the
coil 41 back and forth. The coil 41 has an inclined surface 41a formed at
the peripheral side of the lower end surface of the discharge coil 41
which is capable of sliding on the inclined surfaces 44a of the wedge
members 44. When the wedge members 44 are moved toward the center of the
coil 41, the inclined surfaces 44a of the wedge members 44 come in contact
with the inclined surface 41a of the coil 41 at a plurality of portions of
the coil 41 and the inclined surface 41a slides on the inclined surfaces
44a and the coil 41 is moved upward so that the coil 41 will form the
approximately bell-shaped configuration in three dimensions as sectionally
shown in FIG. 18. On the other hand, when the wedge members 44 are moved
toward the peripheral side opposite to the center side of the coil 41, the
inclined surfaces 44a of the wedge members 44 move away from the inclined
surfaces 41a of the coil 41 so that the coil 41 forms a planar spiral
shape in two dimensions. By adjusting the moving amounts of the wedge
members 44 and thus, adjusting the upward moving amounts of the coil 41,
the coil 41 can assume either one of the inverted approximately
bell-shaped configuration in three dimensions as shown in FIG. 18 and the
planar spiral shape. As a result, by adjusting the upward moving amounts
of the portions of the coil 41, the pitch of the coil 41 in its diameter
direction can be changed to change the shape of the coil 41 so as to
control the plasma density in-plane distribution.
According to a seventh embodiment of the present invention, as shown in
FIG. 20, a discharge coil 51 may have a multi-coil spiral shape comprised
of the planar spiral discharge coil elements 51a, 51b, 51c, and 51d which
is similar to the multi-coil spiral shape comprised of the planar spiral
discharge coil elements 1a, 1b, 1c, and 1d as shown in FIG. 14. Only a
portion of each of the planar spiral discharge coil elements 51a, 51b,
51c, and 51d from its center side 52 of each element to a section which is
fixed by a pair of stoppers 57 can be moved between a gap defined by a
pair of guides 56 in the diameter direction of the coil 51. Then, each
movable portion of the coil 51 can move between a position shown by one
dotted chain lines clockwise located from the solid line position and a
position shown by two dotted chain lines counterclockwise located from the
solid line position while between the pair of guides 56. Thus, the pitch
in the diameter direction of the coil 51 is varied to change the shape of
the coil 51 so as to control a plasma density in-plane distribution.
According to an eighth embodiment of the present invention, as shown in
FIG. 21, a planar spiral discharge coil 61 may have a multi-coil spiral
shape comprised of planar spiral discharge coil elements 61a, 61b, 61c,
and 61d which is similar to the multi-coil spiral shape comprised of the
planar spiral discharge coil elements 1a, 1b, 1c, and 1d as shown in FIG.
14. The coil 61 has switches 64, 65, 66, and 67 for opening and closing
the coil elements 61a, 61b, 61c, and 61d which are arranged between center
side ends 62 and peripheral side ends. Then, the switches 64, 65, 66, and
67 are turned on or turned off to select any number and any position of
coil elements among the four coil elements 61a, 61b, 61c, and 61d. | | |
