U.S. patent application number 13/049462 was filed with the patent office on 2011-07-07 for plasma processing apparatus, electrode plate for plasma processing apparatus, and electrode plate manufacturing method.
Invention is credited to Shinji HIMORI, Hiroki MATSUMARU, Shoichiro MATSUYAMA, Kazuya NAGASEKI, Katsuya OKUMURA, Toshiki TAKAHASHI.
Application Number | 20110162802 13/049462 |
Document ID | / |
Family ID | 32854099 |
Filed Date | 2011-07-07 |
United States Patent
Application |
20110162802 |
Kind Code |
A1 |
OKUMURA; Katsuya ; et
al. |
July 7, 2011 |
PLASMA PROCESSING APPARATUS, ELECTRODE PLATE FOR PLASMA PROCESSING
APPARATUS, AND ELECTRODE PLATE MANUFACTURING METHOD
Abstract
A plasma processing apparatus for performing a plasma process on
a target substrate includes a process container configured to
accommodate the target substrate and to reduce pressure therein. A
first electrode is disposed within the process container. A supply
system is configured to supply a process gas into the process
container. An electric field formation system is configured to form
an RF electric field within the process container so as to generate
plasma of the process gas. A number of protrusions are discretely
disposed on a main surface of the first electrode and protrude
toward a space where the plasma is generated.
Inventors: |
OKUMURA; Katsuya; (Tokyo,
JP) ; HIMORI; Shinji; (Nirasaki-shi, JP) ;
NAGASEKI; Kazuya; (Nirasaki-shi, JP) ; MATSUMARU;
Hiroki; (Nirasaki-shi, JP) ; MATSUYAMA;
Shoichiro; (Nirasaki-shi, JP) ; TAKAHASHI;
Toshiki; (Esashi-shi, JP) |
Family ID: |
32854099 |
Appl. No.: |
13/049462 |
Filed: |
March 16, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12505940 |
Jul 20, 2009 |
7922862 |
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13049462 |
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11195803 |
Aug 3, 2005 |
7585386 |
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12505940 |
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PCT/JP04/01042 |
Feb 3, 2004 |
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11195803 |
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Current U.S.
Class: |
156/345.44 ;
118/723E; 156/345.43 |
Current CPC
Class: |
H01J 37/32541 20130101;
H01J 37/32009 20130101; H01L 21/3065 20130101; H01J 37/32082
20130101 |
Class at
Publication: |
156/345.44 ;
156/345.43; 118/723.E |
International
Class: |
H01L 21/00 20060101
H01L021/00; C23F 1/08 20060101 C23F001/08; H05H 1/24 20060101
H05H001/24; C23C 16/509 20060101 C23C016/509; C23C 16/458 20060101
C23C016/458; C23C 16/455 20060101 C23C016/455 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 3, 2003 |
JP |
2003-025899 |
May 12, 2003 |
JP |
2003-132810 |
Feb 2, 2004 |
JP |
2004-025007 |
Claims
1. A plasma processing apparatus for performing a plasma process on
a target substrate, the apparatus comprising: a process container
configured to accommodate the target substrate and to reduce
pressure therein; a first electrode disposed within the process
container; a gas supply system configured to supply a process gas
into the process container; an electric field formation system
configured to form a radio frequency (RF) electric field within the
process container so as to generate plasma of the process gas; and
a dielectric body disposed on a main surface of the first electrode
and having a thickness larger at an electrode central portion than
at an electrode edge portion, wherein the first electrode is
provided with an outer electrode portion protruding by a required
protruding amount relative to the main surface toward a space where
the plasma is generated, the outer electrode portion being distant
from an outer edge of the dielectric body by a required distance
outward in a radial direction.
2. The apparatus according to claim 1, wherein the outer electrode
portion is covered with a dielectric protection layer.
3. The apparatus according to claim 2, wherein the dielectric
protection layer is a layer prepared by processing a surface of the
outer electrode portion.
4. The apparatus according to claim 2, wherein the dielectric
protection layer is a thermal-sprayed film formed on the outer
electrode portion.
5. The apparatus according to claim 4, wherein the thermal-sprayed
film consist essentially of a material selected from the group
consisting of Al.sub.2O.sub.3 and Y.sub.2O.sub.3.
6. The apparatus according to claim 1, wherein the outer electrode
portion and an inner electrode portion of the first electrode are
connected by an inclined portion having a surface inclined outward
in a radial direction.
7. The apparatus according to claim 6, wherein the inclined portion
starts from the inner electrode portion at a position outside an
edge of the target substrate in a radial direction.
8. The apparatus according to claim 1, wherein the required
protruding amount is set to adjust a distribution characteristic of
an intensity of the electric field to increase the intensity near
an edge of the target substrate.
9. The apparatus according to claim 1, wherein the dielectric body
includes a tapered portion disposed at its periphery and having a
thickness that decreases taper-wise toward the outer edge.
10. The apparatus according to claim 1, wherein the dielectric body
includes a flat portion disposed at a center to be concentric with
the first electrode and having a first diameter and a first
constant thickness, and a tapered portion disposed outside the
first diameter to be concentric with the flat portion and having a
thickness that decreases taper-wise toward the electrode edge
portion.
11. The apparatus according to claim 10, wherein the tapered
portion is directly connected to the flat portion in the dielectric
body.
12. The apparatus according to claim 1, wherein the apparatus
further comprises a second electrode disposed opposite to the first
electrode within the process container, such that the first
electrode is an upper electrode, and the second electrode is a
lower electrode on which the target substrate is placed.
13. The apparatus according to claim 12, wherein the second
electrode is configured to place thereon the target substrate
essentially having a circular contour.
14. The apparatus according to claim 12, wherein the electric field
formation system includes an RF power supply connected to the first
electrode or the second electrode and configured to apply an RF
power thereto.
15. The apparatus according to claim 1, wherein the gas supply
system is configured to supply as the process gas a gas for etching
the target substrate.
16. The apparatus according to claim 14, wherein the RF power
supply is connected to the second electrode and configured to apply
an RF power having a frequency of 50 MHz or more.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a division of application Ser.
No. 12/505,940, filed on Jul. 20, 2009, which is a division of
application Ser. No. 11/195,803, filed on Aug. 3, 2005, which is a
Continuation Application of PCT Application No. PCT/JP2004/001042,
filed Feb. 3, 2004, which was published under PCT Article 21(2) in
Japanese and claims the benefit of priority from prior Japanese
Patent Applications No. 2003-025899, filed Feb. 3, 2003; No.
2003-132810, filed May 12, 2003; and No. 2004-025007, filed Feb. 2,
2004, the entire contents of all of which are incorporated herein
by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a technique for subjecting
a target substrate to a plasma process, and specifically to a
plasma processing technique of the RF (radio frequency) discharge
type that applies an RF to an electrode to generate plasma.
Particularly, the present invention relates to a plasma processing
technique utilized in a semiconductor process for manufacturing
semiconductor devices. The term "semiconductor process" used herein
includes various kinds of processes which are performed to
manufacture a semiconductor device or a structure having wiring
layers, electrodes, and the like to be connected to a semiconductor
device, on a target substrate, such as a semiconductor wafer or a
glass substrate used for an LCD (Liquid Crystal Display) or FPD
(Flat Panel Display), by forming semiconductor layers, insulating
layers, and conductive layers in predetermined patterns on the
target substrate.
[0004] 2. Description of the Related Art
[0005] In manufacturing semiconductor devices and FPDs, plasma is
often used for processes, such as etching, deposition, oxidation,
and sputtering, so that process gases can react well at a
relatively low temperature. In general, plasma processing
apparatuses are roughly classified, in terms of the plasma
generation type, into those utilizing glow discharge or RF
discharge, and those utilizing microwave.
[0006] In general, a plasma processing apparatus of the RF
discharge type includes a process container or reaction chamber,
and an upper electrode and a lower electrode disposed therein in
parallel with each other. The lower electrode is configured to
support a target substrate (semiconductor wafer, glass substrate,
or the like) thereon. The upper electrode or lower electrode is
supplied with RF voltage for plasma generation through a matching
unit. Electrons are accelerated by an RF electric field formed by
the RF voltage and collide with a process gas, thereby ionizing the
gas and generating plasma.
[0007] In recent years, miniaturization proceeds in the design
rules used for manufacturing processes, and thus plasma processes
are required to generate higher density plasma at a lower pressure.
Under the circumstances, there is a trend in plasma processing
apparatuses of the RF discharge type described above, such that the
RF applied is selected from a range covering far higher frequencies
(for example, 50 MHz or more) than conventional values (typically,
27 MHz or less). However, if the frequency of the RF discharge is
set higher, when the RF power is applied from an RF power supply
through a feed rod to the electrode backside, it is transmitted
through the electrode surface by means of the skin effect and flows
from the edge portion to the central portion on the electrode main
surface (the surface facing the plasma). If an RF current flows
from the edge portion to the central portion on the flat electrode
main surface, the electric field intensity at the central portion
of the electrode main surface becomes higher than the electric
field intensity at the edge portion, so the density of generated
plasma becomes higher at the electrode central portion than at the
electrode edge portion. Further, the resistivity of plasma becomes
lower at the electrode central portion having a higher plasma
density, and, also on the counter electrode, an electric current
concentrates at the central portion, so the uniformity of the
plasma density is further lowered.
[0008] In order to solve this problem, a design is known in which
the main surface central portion of an RF electrode is formed of a
high resistivity member (for example, Jpn. Pat. Appln. KOKAI
Publication No. 2000-323456). According to this technique, the high
resistivity member is employed for the central portion of the main
surface (plasma contact surface) of an electrode connected to an RF
power supply. The high resistivity member consumes more RF power as
Joule heat there, so that the electric field intensity on the
electrode main surface is more reduced at the electrode central
portion than at the electrode peripheral portion. As a consequence,
the low uniformity described above in plasma density is
remedied.
[0009] However, in plasma processing apparatuses of the RF
discharge type described above, the high resistivity member
employed for the main surface central portion of an RF electrode
may consume too much RF power as Joule heat (energy loss).
BRIEF SUMMARY OF THE INVENTION
[0010] In consideration of problems of conventional techniques, an
object of the present invention is to provide a plasma processing
apparatus of the RF discharge type and an electrode plate for a
plasma processing apparatus, which can efficiently improve the
plasma density uniformity.
[0011] Another object of the present invention is to provide an
electrode plate manufacturing method for efficiently fabricating a
structure of an electrode plate for a plasma processing apparatus
according to the present invention provided with an electrostatic
chuck integrally disposed thereon.
[0012] In order to achieve the objects described above, according
to a first aspect of the present invention, there is provided a
plasma processing apparatus comprising a process container
configured to reduce pressure therein and a first electrode
disposed within the process container, such that an RF electric
field is formed within the process container and a process gas is
supplied thereinto to generate plasma of the process gas, thereby
performing a required plasma process on a target substrate by the
plasma, wherein a number of protrusions are discretely disposed on
a main surface of the first electrode and protrude toward a space
where the plasma is generated. According to this apparatus
structure, an RF for plasma generation may be applied to the first
electrode, or to another electrode, such as a second electrode of
the parallel-plate type facing the first electrode. Where the RF is
applied to the first electrode, the RF may be applied from a
backside of the first electrode reverse to the main surface.
[0013] Where the RF is applied from a backside of the first
electrode, when an RF current flows on the main surface of the
first electrode by means of the skin effect from the electrode edge
portion to the electrode central portion, it flows through the
surface layer of the protrusions. Since the protrusions protrude
toward the plasma space, they are electrically coupled with the
plasma with a lower impedance, as compared with the portion other
than the protrusions or the bottom portion on the main surface.
Accordingly, the RF power carried by the RF current flowing through
the surface layer on the main surface of the electrode is
discharged mainly from the top surface of the protrusions toward
the plasma. In this case, each of a number of protrusions
discretely disposed on the main surface of the first electrode
functions as a small electrode to apply an RF power to the plasma.
By suitably selecting properties (shape, size, distance, density,
and so forth) of the protrusions, the RF power application
characteristic of the first electrode relative to plasma can be
controlled as required.
[0014] For example, in order to ensure the RF power application
function described above of the protrusions, the protrusions on the
main surface of the first electrode may preferably have a height
and a width in an electrode radial direction, each of which is
three times or more a skin depth .delta. defined by the following
formula (1),
.delta.=(2/.omega..sigma..mu.).sup.1/2 (1)
[0015] where .omega.=2.pi.f (f: frequency), .sigma.: specific
electric conductivity, and .mu.: magnetic permeability.
[0016] Further, in order to improve the uniformity of electric
field intensity or plasma density in an electrode radial direction,
the protrusions on the main surface of the first electrode may
preferably have an area density that gradually increases from the
electrode central portion to the electrode edge portion. For
example, where the protrusions have a constant size, the
protrusions may have a number density that gradually increases from
the electrode central portion to the electrode edge portion.
[0017] In a preferable example, the protrusions may be formed of
columns. Alternatively, the protrusions may be formed of rings,
which are concentrically disposed as a whole.
[0018] Further, in order to improve the RF power discharge function
described above of the protrusions, a dielectric body may be
preferably disposed at least at a position other than the
protrusions on the main surface of the first electrode.
[0019] According to a second aspect of the present invention, there
is provided a plasma processing apparatus comprising a process
container configured to reduce pressure therein and a first
electrode disposed within the process container, such that an RF
electric field is formed within the process container and a process
gas is supplied thereinto to generate plasma of the process gas,
thereby performing a required plasma process on a target substrate
by the plasma, wherein a number of recesses are discretely disposed
on a main surface of the first electrode and dent opposite a space
where the plasma is generated. Also, according to this apparatus
structure, an RF for plasma generation may be applied to the first
electrode, or to another electrode, such as a second electrode of
the parallel-plate type facing the first electrode. Where the RF is
applied to the first electrode, the RF may be applied from a
backside of the first electrode reverse to the main surface.
[0020] Since the recesses are dent opposite the plasma space, they
are electrically coupled with the plasma with a higher impedance,
as compared with the portion other than the recesses (the top
portion of the electrode main surface). Accordingly, the RF power
carried by an RF current flowing through the surface layer on the
main surface of the first electrode is discharged mainly from the
portion other than the recesses (the top portion of the electrode
main surface) toward the plasma. In this case, each of a number of
recesses discretely disposed on the main surface of the first
electrode functions as an electrode mask portion to suppress
application of an RF power to the plasma. By suitably selecting
properties (shape, size, distance, density, and so forth) of the
recesses, the effect of the first electrode concerning plasma
generation can be controlled as required.
[0021] For example, in order to ensure the RF power application
mask function described above of the recesses, the recesses on the
main surface of the first electrode may preferably have a height
and a width in an electrode radial direction, each of which is
three times or more the skin depth 6 described above.
[0022] Further, in order to improve the uniformity of electric
field intensity or plasma density in an electrode radial direction,
the recesses on the main surface of the first electrode may
preferably have an area density that gradually decreases from the
electrode central portion to the electrode edge portion. For
example, where the recesses have a constant size, the recesses may
have a number density that gradually decreases from the electrode
central portion to the electrode edge portion.
[0023] In a preferable example, the recesses may be formed of
columnar recesses. Further, in order to improve the RF power
application mask function described above of the recesses, a
dielectric body may be preferably disposed at least within the
recess on the main surface of the first electrode.
[0024] According to a third aspect of the present invention, there
is provided a plasma processing apparatus comprising a process
container configured to reduce pressure therein and a first
electrode disposed within the process container, such that an RF
electric field is formed within the process container and a process
gas is supplied thereinto to generate plasma of the process gas,
thereby performing a required plasma process on a target substrate
by the plasma, wherein a dielectric body is disposed on a main
surface of the first electrode and has a thickness larger at an
electrode central portion than at an electrode edge portion. Also,
according to this apparatus structure, an RF for plasma generation
may be applied to the first electrode, or to another electrode,
such as a second electrode of the parallel-plate type facing the
first electrode. Where the RF is applied to the first electrode,
the RF may be applied from a backside of the first electrode
reverse to the main surface.
[0025] In this electrode structure, since the electrode central
portion has a higher impedance than the electrode edge portion, an
RF electric field is formed such that the intensity is enhanced at
the electrode edge portion while it is weakened at the electrode
central portion. As a consequence, the uniformity of the electric
field intensity or plasma density is improved.
[0026] In this structure, the dielectric body may preferably have a
profile such that the thickness of the dielectric body gradually
decreases (preferably in an arch-shape) from the electrode central
portion to the electrode edge portion. Alternatively, the
dielectric body may preferably have a thickness that is essentially
constant inside a first diameter including the electrode central
portion. In this case, the dielectric body may have a thickness
that decreases taper-wise toward the electrode edge portion outside
the first diameter, or the dielectric body may have a thickness
that is essentially constant between the first diameter and a
second diameter larger than the first diameter, and then decreases
taper-wise toward the electrode edge portion outside the second
diameter. The area size of the dielectric body can be arbitrarily
set in accordance with the size of the target substrate, and may be
typically set to be the same as the size of the target substrate.
In other words, the edge portion of the dielectric body where the
thickness takes on a minimum value may be located around a position
facing the edge portion of the target substrate. Further, since
there is a constant correlation between the dielectric constant of
the dielectric body and the thickness of the dielectric body at the
electrode central portion to provide a good planar uniformity, the
dielectric body at the electrode central portion may have a
thickness set in accordance with a dielectric constant of the
dielectric body in use.
[0027] In a preferable example, a conductive shield member may be
disposed to partly cover the dielectric body, e.g., near the edge
portion, on the main surface of the first electrode. According to
this structure, the effect of the dielectric body for reducing the
electric field intensity is attenuated at the portion covered with
the shield member. Accordingly, by adjusting the shape and/or size
of the shield member, the distribution characteristic of electric
field intensity can be adjusted. The shield member may be
preferably detachable or replaceable.
[0028] In a preferable example, the main surface of the first
electrode may be provided with an outer electrode portion
protruding by a required protruding amount toward a space where the
plasma is generated, the outer electrode portion being distant from
an outer edge of the dielectric body by a required distance outward
in the radial direction. In this electrode structure, the
protrusion disposed outside the dielectric film in the radial
direction allows the distribution characteristic of electric field
intensity to be controlled or adjusted such that the electric field
intensity becomes higher near the edge of the target substrate.
This adjustment of the electric field intensity distribution by the
protrusion can be controlled by the protruding amount of the
protrusion or the position of the protrusion shoulder.
[0029] In another preferable example, the dielectric body on the
main surface of the first electrode may have a portion protruding
by a required protruding amount toward a space where the plasma is
generated. In this electrode structure, the protrusion of the
dielectric film allows the distribution characteristic of electric
field intensity to be controlled or adjusted such that the electric
field intensity becomes higher at respective position of the plasma
generation space facing the dielectric body.
[0030] In another preferable example, the dielectric body on the
main surface of the first electrode may have a void formed therein,
which contains a dielectric fluid (preferably an organic solvent).
In this structure, the dielectric constant or dielectric impedance
of the entire dielectric body can be arbitrarily adjusted by
suitably selecting or setting the amount of the dielectric fluid
contained in the void or occupation space shape thereof. The void
may be formed within a solid dielectric body. Alternatively, at
least the front surface may be formed of a solid dielectric body on
the main surface of the first electrode, while an inner wall or
recess is defined by the electrode host material (conductor).
[0031] In the plasma processing apparatus according to the first,
second, or third aspect, even where the first electrode provided
with the protrusions, recesses, or dielectric body described above
is designed to be supplied with no RF, such as where the first
electrode is connected to the ground potential, it is possible to
obtain the same effect as described above on the plasma generation
space.
[0032] A plasma processing apparatus according to the present
invention may include an electrostatic chuck for attracting and
holding the target substrate by a Coulomb force. The electrostatic
chuck may be disposed on the main surface of the first electrode to
be supplied with an RF power supply, or may be disposed on the main
surface of the counter electrode or second electrode. Where the
electrostatic chuck is disposed on the main surface of the first
electrode, the second electrode may be connected to the ground
potential through the process container, so that an RF current in
the plasma can flow to the ground through the process
container.
[0033] According to the first aspect of the present invention,
there is provided an electrode plate for a plasma processing
apparatus, which is to be disposed within a process container for
generating plasma in a plasma processing apparatus of an RF
discharge type, the electrode plate comprising a number of
protrusions discretely disposed on a main surface to face the
plasma. According to this electrode plate, it is possible to obtain
the same effect as the first or second electrode of a plasma
processing apparatus according to the first aspect, as described
above.
[0034] An electrode plate manufacturing method of the present
invention for manufacturing the electrode plate according to the
first aspect comprises: covering a main surface of an electrode
substrate with a mask that has openings in accordance with the
protrusions; applying a conductive metal or semiconductor by
thermal spray onto the main surface of the electrode substrate from
above the mask, thereby forming the protrusions in the openings;
and removing the mask from the main surface of the electrode
substrate.
[0035] According to the second aspect of the present invention,
there is provided an electrode plate for a plasma processing
apparatus, which is to be disposed within a process container for
generating plasma in a plasma processing apparatus of an RF
discharge type, the electrode plate comprising a number of recesses
discretely disposed on a main surface to face the plasma. According
to this electrode plate, it is possible to obtain the same effect
as the first or second electrode of a plasma processing apparatus
according to the second aspect, as described above.
[0036] An electrode plate manufacturing method of the present
invention for manufacturing the electrode plate according to the
second aspect comprises: covering a main surface of an electrode
substrate with a mask that has openings in accordance with the
recesses; applying a solid particles or liquid by blasting onto the
main surface of the electrode substrate from above the mask,
thereby physically removing portions of the electrode substrate in
the openings so as to form the recesses; and removing the mask from
the main surface of the electrode substrate.
[0037] The electrode plate manufacturing method of the present
invention may preferably further comprise, after removing the mask,
applying a dielectric body by thermal spray onto the main surface
of the electrode substrate, thereby forming a first dielectric
film. By doing so, a dielectric body for increasing the impedance
ratio is formed on the portion other than the protrusions in the
case of the electrode plate according to the first aspect, or
formed within the recess in the case of the electrode plate
according to the second aspect.
[0038] Further, in order to integrally dispose an electrostatic
chuck on the electrode plate according to the first or second
aspect, the method may preferably further comprise: forming the
first dielectric film to have a thickness entirely covering the
main surface of the electrode substrate; applying an electrode
material by thermal spray onto the first dielectric film, thereby
forming an electrode film of the electrostatic chuck; and then,
applying a dielectric body by thermal spray onto the electrode
film, thereby forming a second dielectric film. With this method,
it is possible to simultaneously and integrally form a dielectric
body for increasing the impedance ratio with the lower insulating
film of the electrostatic chuck, on the main surface of the
electrode plate according to the first or second aspect.
[0039] According to the third aspect of the present invention,
there is provided an electrode plate for a plasma processing
apparatus, which is to be disposed within a process container for
generating plasma in a plasma processing apparatus of an RF
discharge type, the electrode plate comprising a dielectric body on
a main surface to face the plasma, which has a thickness larger at
an electrode central portion than at an electrode edge portion.
According to this electrode plate, it is possible to obtain the
same effect as the first or second electrode of a plasma processing
apparatus according to the third aspect, as described above.
[0040] 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 hereinafter.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0041] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate embodiments of
the invention, and together with the general description given
above and the detailed description of the embodiments given below,
serve to explain the principles of the invention.
[0042] FIG. 1 is a sectional side view showing a plasma etching
apparatus according to an embodiment of the present invention;
[0043] FIG. 2 is a plan view showing a susceptor structure
according to the first embodiment of the present invention;
[0044] FIG. 3 is an enlarged partial and sectional side view
showing the susceptor structure according to the first
embodiment;
[0045] FIG. 4 is a view showing a distribution characteristic
concerning the protrusion number density on the susceptor structure
according to the first embodiment;
[0046] FIG. 5 is a view schematically showing an RF discharge
scheme in the plasma etching apparatus shown in FIG. 1;
[0047] FIG. 6 is a plan view showing the flow directions of an RF
current on the main surface of an RF electrode in the plasma
etching apparatus shown in FIG. 1;
[0048] FIG. 7 is a sectional side view schematically showing flows
of an RF current and radiations of RF power (electric field) in the
susceptor structure according to the first embodiment;
[0049] FIG. 8 is a characteristic view showing an attenuation
characteristic in the depth direction of an electro-magnetic wave
(RF current) flowing through a conductor;
[0050] FIG. 9 is a view showing distribution characteristics of
electric field intensity in the electrode radial direction, using
as a parameter a ratio in protrusion number density between the
electrode central portion and edge portion according the first
embodiment;
[0051] FIG. 10 is a sectional side view showing a structure in
which an electrostatic chuck is integrally formed with a susceptor
according to the first embodiment;
[0052] FIG. 11 is a view showing the impedance ratio characteristic
between the protrusions and bottom portion in the susceptor
structure with the electrostatic chuck shown in FIG. 10;
[0053] FIGS. 12A to 12F are views showing steps of a method of
manufacturing the susceptor structure with the electrostatic chuck
shown in FIG. 10;
[0054] FIG. 13 is a view showing a modified susceptor structure
according to the first embodiment;
[0055] FIG. 14 is a sectional side view showing an arrangement in
which an electrode protrusion structure according to the first
embodiment is applied to an upper electrode;
[0056] FIG. 15 is a plan view showing an electrode structure
according to a second embodiment of the present invention;
[0057] FIG. 16 is an enlarged partial and sectional side view of
the electrode structure shown in FIG. 15;
[0058] FIG. 17 is a view showing a distribution characteristic
concerning the recess number density on the electrode structure
shown in FIG. 15;
[0059] FIGS. 18A to 18F are views showing steps of a method of
manufacturing an electrode structure with an electrostatic chuck
integrally formed therewith, according to the second
embodiment;
[0060] FIG. 19 is a plan view showing a lower electrode structure
according to a third embodiment;
[0061] FIG. 20 is a plan view showing an upper electrode structure
according to the third embodiment;
[0062] FIG. 21 is a view showing a parallel-plate electrode
structure according to third embodiment;
[0063] FIG. 22 is a view showing distribution characteristics of
electric field intensity in the electrode radial direction, using
as a parameter the film thickness at the upper electrode central
portion of the parallel-plate electrode structure shown in FIG.
21;
[0064] FIGS. 23A to 23D are views showing specific present examples
concerning the film thickness profile of a dielectric film on an
upper electrode according to the third embodiment;
[0065] FIGS. 24A and 24B are views showing distribution
characteristics of electric field intensity in the radial direction
between electrodes, obtained by the present examples shown in FIGS.
23A to 23D and an ideal profile;
[0066] FIGS. 25A to 25D are views showing other specific present
examples concerning the film thickness profile of a dielectric film
on an upper electrode according to the third embodiment;
[0067] FIGS. 26A and 26B are views showing distribution
characteristics of electric field intensity in the radial direction
between electrodes, obtained by the present examples shown in FIGS.
25A to 25D;
[0068] FIGS. 27A to 27C are views showing other specific present
examples concerning the film thickness and film quality profiles of
a dielectric film on an upper electrode according to the third
embodiment;
[0069] FIGS. 28A and 28B are views showing distribution
characteristics of electric field intensity in the radial direction
between electrodes, obtained by the present examples shown in FIGS.
27A to 27C;
[0070] FIG. 29 is a view showing the correlation between the
dielectric constant of a dielectric film and the film thickness at
the electrode central portion, the dielectric film being designed
to provide a practically sufficient planar uniformity in accordance
with data points in FIGS. 28A and 28B;
[0071] FIGS. 30A and 30B are views showing distribution
characteristics of organic film etching rate, obtained in a present
example A of an upper electrode according to the third embodiment
and a comparative example B, respectively, for comparison;
[0072] FIGS. 31A and 31B are views showing a present example of a
lower electrode according to the third embodiment and a comparative
example, respectively, for comparison;
[0073] FIGS. 32A and 32B are views showing distribution
characteristics of organic film etching rate, obtained in the
present example shown in FIG. 31A and the comparative example shown
in FIG. 31B, respectively, for comparison;
[0074] FIGS. 33A and 33B are partial and sectional views showing
present examples of an upper electrode structure according another
embodiment of the present invention;
[0075] FIG. 34 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present examples shown in FIGS. 33A and
33B;
[0076] FIGS. 35A to 35C are partial and sectional views showing a
present example of an upper electrode structure according to
another embodiment of the present invention, a comparative example,
and a reference example, respectively;
[0077] FIG. 36 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present example, comparative example,
and reference example shown in FIGS. 35A to 35C;
[0078] FIGS. 37A to 37C are partial and sectional views showing
other present examples of an upper electrode structure, and a
comparative example, respectively;
[0079] FIG. 38 is a view showing distribution characteristics of
oxide film etching rate (normalized value), obtained by the present
examples and comparative example, shown in FIGS. 37A to 37C;
[0080] FIGS. 39A to 39C are partial and sectional views showing a
present example of an upper electrode structure according to
another embodiment of the present invention, a comparative example,
and a reference example, respectively;
[0081] FIG. 40 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present example, comparative example,
and reference example shown in FIGS. 39A to 39C;
[0082] FIG. 41 is a partial and sectional view showing an upper
electrode structure according to a modification of the embodiment
shown in FIGS. 35A to 38;
[0083] FIGS. 42A to 42D are partial and sectional views showing
upper electrode structures according to another embodiment of the
present invention;
[0084] FIG. 43 is a partial and sectional view showing a specific
present example of the embodiment shown in FIGS. 42A to 42D;
[0085] FIG. 44 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present example shown in FIG. 43;
and
[0086] FIGS. 45A to 45D are partial and sectional views showing
upper electrode structures according to a modification of the
embodiment shown in FIGS. 42A to 42D.
DETAILED DESCRIPTION OF THE INVENTION
[0087] Embodiments of the present invention will be described
hereinafter with reference to the accompanying drawings. In the
following description, the constituent elements having
substantially the same function and arrangement are denoted by the
same reference numerals, and a repetitive description will be made
only when necessary.
[0088] FIG. 1 is a sectional side view showing a plasma etching
apparatus according to an embodiment of the present invention. This
plasma etching apparatus is structured as a plasma etching
apparatus of the RIE type. The plasma processing apparatus includes
a cylindrical chamber (process container) 10 made of a metal, such
as aluminum or stainless steel. The chamber 10 is protectively
grounded.
[0089] The chamber 10 is provided with a lower electrode or
susceptor 12 formed of a circular plate disposed therein, on which
a target substrate or semiconductor wafer W is placed. The
susceptor 12 is made of, e.g., aluminum, and is supported through
an insulative cylindrical holder 14 on a cylindrical support
portion 16, which extends vertically upward from the bottom of the
chamber 10. A focus ring 18 made of, e.g., quartz is disposed on
top of the cylindrical holder 14 to surround the top surface of the
susceptor 12.
[0090] An exhaust passage 20 is defined between the sidewall of the
chamber 10 and the cylindrical support portion 16. The exhaust
passage 20 is provided with an annular baffle plate 22 attached at
the entrance or middle, and an exhaust port 24 formed at the
bottom. The exhaust port 24 is connected to an exhaust apparatus 28
through an exhaust line 26. The exhaust apparatus 28 includes a
vacuum pump for reducing the pressure of the process space within
the chamber 10 to a predetermined vacuum level. A transfer port for
a semiconductor wafer W is formed in the sidewall of the chamber 10
and is opened/closed by a gate valve 30.
[0091] The susceptor 12 is electrically connected to a radio
frequency (RF) power supply 32 for generating plasma, through a
matching unit 34 and a power feeding rod 36. The RF power supply 32
is arranged to apply an RF power of a predetermined frequency, such
as 60 MHz, to the susceptor 12 used as a lower electrode. A
showerhead 38 described later is disposed on the ceiling of the
chamber 10 and is used as an upper electrode at the ground
potential. The RF voltage from the RF power supply 32 is
capacitively applied across the space between the susceptor 12 and
showerhead 38.
[0092] The susceptor 12 is provided with an electrostatic chuck 40
on the top, for holding the semiconductor wafer W by an
electrostatic attraction force. The electrostatic chuck 40
comprises an electrode 40a made of a conductive film, and a pair of
insulating films 40b and 40c sandwiching the electrode 40a. The
electrode 40a is electrically connected to a direct-current (DC)
power supply 42 through a switch 43. With a DC voltage applied from
the DC power supply 42, the electrostatic chuck 40 attracts and
holds the semiconductor wafer W on the chuck by a Coulomb
force.
[0093] The susceptor 12 is further provided with a cooling medium
space 44 formed therein and annularly extending therethrough. A
cooling medium set at a predetermined temperature, such as cooling
water, is circulated within the cooling medium space 44 from a
chiller unit 46 through lines 48 and 50. The temperature of the
cooling medium is set to control the process temperature of the
semiconductor wafer W placed on the electrostatic chuck 40.
Further, a heat transmission gas, such as He gas, is supplied from
a heat transmission gas supply unit 52, through gas supply line 54,
into the interstice between the top surface of the electrostatic
chuck 40 and the backside of the semiconductor wafer W.
[0094] The showerhead 38 disposed at the ceiling includes an
electrode plate 56 on the bottom side having a number of gas
delivery holes 56a, and an electrode support 58 detachably
supporting the electrode plate 56. The electrode support 58 has a
buffer space 60 formed therein, which has a gas feed port 60a
connected to a process gas supply section 62 through a gas feed
line 64.
[0095] A magnetic member 66 is disposed around the chamber 10 to
extend annularly or concentrically. An RF electric field is formed
by the RF power supply 32 to extend vertically in the space between
the showerhead 38 and susceptor 12 within the chamber 10. High
density plasma is generated near the surface of the susceptor 12 by
RF discharge.
[0096] A control section 68 is arranged to control the operations
of respective parts of the plasma etching apparatus, such as the
exhaust apparatus 28, RF power supply 32, electrostatic chuck
switch 43, chiller unit 46, heat transmission gas supply unit 52,
and process gas supply section 62. The control section 68 is also
connected to the host computer (not shown).
[0097] When the plasma etching apparatus is used for etching, the
following operations are performed. Specifically, at first, the
gate valve 30 is opened, and a semiconductor wafer W to be
processed is transferred into the chamber 10, and placed on the
electrostatic chuck 40. Then, an etching gas (mixture gas in
general) is supplied at a predetermined flow rate and flow ratio
from the process gas supply section 62 into the chamber 10, while
the chamber 10 is exhausted by the exhaust apparatus 28, to set the
pressure within the chamber 10 at a set value. In addition, an RF
power is applied at a predetermined power level from the RF power
supply 32 to the susceptor 12. Further, a DC voltage is applied
from the DC power supply 42 to the electrode 40a of the
electrostatic chuck 40, so as to fix the semiconductor wafer W onto
the electrostatic chuck 40. With this arrangement, the etching gas
delivered from the showerhead 38 is turned into plasma by RF
discharge between the electrodes 12 and 38. The main surface of the
semiconductor wafer W is etched by radicals and ions generated from
the plasma.
[0098] In this plasma etching apparatus, the RF applied to the
susceptor (lower electrode) 12 is selected from a range covering
far higher frequencies (for example, 50 MHz or more) than
conventional values (typically, 27 MHz or less). As a consequence,
the plasma density is increased with a preferable dissociation
state, so that high density plasma is formed even under a low
pressure condition.
[0099] FIG. 2 is a plan view showing a susceptor structure
(susceptor 12) according to the first embodiment of the present
invention. FIG. 3 is an enlarged partial and sectional side view
showing the susceptor structure. FIG. 4 is a view showing a
distribution characteristic concerning the protrusion number
density on the susceptor structure. The main surface of the
susceptor 12 (the top surface of the susceptor 12, i.e., the
surface facing the plasma generation space, in this embodiment) is
provided with a number of columnar protrusions 70 made of a
conductor or semiconductor which have a constant size and are
discretely arrayed. Each of the protrusions 70 functions as a small
electrode to apply an RF power or RF electric field to plasma.
Preferably, as shown in FIG. 4, the protrusions 70 are arrayed on
the main surface of the susceptor 12 with a number density
distribution or area density distribution such that the density
gradually increases from the electrode central portion to the
electrode edge portion.
[0100] FIG. 5 is a view schematically showing an RF discharge
scheme in the plasma etching apparatus shown in FIG. 1. As shown in
FIG. 5, when an RF power is applied from the RF power supply 32 to
the susceptor 12, plasma PZ of the etching gas is generated near
the semiconductor wafer W by RF discharge between the susceptor
(lower electrode) 12 and upper electrode 38. The generated plasma
PZ diffuses all around, particularly upward and outward in the
radial direction. An electron current or ion current from the
plasma PZ flows to ground through the upper electrode 38, chamber
sidewall, and so forth.
[0101] FIG. 6 is a plan view showing the flow directions of an RF
current on the main surface of an RF electrode in the plasma
etching apparatus shown in FIG. 1. In the susceptor 12, when an RF
power is applied from the RF power supply 32 through the feed rod
36 to the susceptor backside or bottom, it is transmitted through
the electrode surface by means of the skin effect. As shown in FIG.
6, on the main surface of the susceptor 12, an RF current i flows
convergently from the edge portion to the central portion.
[0102] FIG. 7 is a sectional side view schematically showing flows
of an RF current and radiations of RF power (electric field) in the
susceptor structure (susceptor 12) according to the first
embodiment. As shown in FIG. 7, in this embodiment, an RF current i
flows through the surface layer of the protrusions 70 on the main
surface of the susceptor 12. Since the protrusions 70 protrude
toward the upper electrode 38 or plasma PZ, they are electrically
coupled with the plasma PZ with a lower impedance, as compared with
the bottom portion 12a on the main surface. Accordingly, the RF
power carried by the RF current i flowing through the surface layer
on the main surface of the susceptor 12 is discharged mainly from
the top surface of the protrusions 70 toward the plasma PZ.
[0103] As shown in FIG. 3, a dielectric body 72 is preferably
disposed around the protrusions 70 (on the bottom portion 12a).
With this arrangement, the impedance ratio Z.sub.12a/Z.sub.70
between the protrusions 70 and bottom portion 12a can be set higher
on the main surface of the susceptor 12. In other words, it is
possible to increase the RF power ratio or power application rate
applied to the plasma PZ through the protrusions 70.
[0104] As described above, in this embodiment, each of a number of
protrusions 70 discretely arrayed on the main surface of the
susceptor 12 functions as a small electrode to apply an RF power to
the plasma PZ. By suitably selecting properties (shape, size,
distance, density, and so forth) of the protrusions 70, the RF
power application characteristic of the susceptor 12 or a group of
small electrodes can be set as required.
[0105] For example, the number density of the protrusions 70 can be
set to have a distribution characteristic such that the density
gradually increases from the electrode central portion to the
electrode edge portion, as described above (see FIG. 4). This
arrangement make it possible to improve the uniformity of the RF
power or RF electric field (particularly, uniformity in the
electrode radial direction) applied from the susceptor 12 to the
plasma PZ, as shown in FIG. 9.
[0106] FIG. 9 is a view showing distribution characteristics of
electric field intensity in the electrode radial direction, using
as a parameter a ratio in protrusion number density between the
electrode central portion and edge portion according the first
embodiment. FIG. 9 shows distributions of electric field intensity
above the susceptor 12 in the radial direction, wherein the radius
of the susceptor 12 is set at 150 mm. The ratio Ne/Nc is set at
different values, 1 (time), 2 (times), 4 (times), 6 (times), 8
(times), between the number density Nc of the protrusions 70 at the
electrode central portion and the number density Ne of the
protrusions 70 at the electrode edge portion. The larger the ratio
Ne/Nc, the better the uniformity of electric field intensity, and
thus the uniformity of plasma density is further improved.
[0107] Of the other properties of the protrusions 70, the size
thereof is particularly important. If the protrusions 70 are too
short, and more specifically shorter than the skin depth (skin
depth) .delta., part or most of the RF current i passes straight
through a position below the protrusions 70 on the main surface of
the susceptor 12. In this case, the RF electric field applied from
the protrusions 70 to the plasma PZ is attenuated by that much. The
skin depth .delta. is defined such that the amplitude of an RF
current flowing through the surface layer of a conductor is
attenuated to 1/e at the depth .delta.. The skin depth .delta. is a
factor expressed by the following formula (1).
.delta.=(2/.omega..sigma..mu.).sup.1/2 (1)
[0108] In this formula, .omega.=2.pi.f (f: frequency), .sigma.:
specific electric conductivity, and .mu.: magnetic
permeability.
[0109] FIG. 8 is a characteristic view showing an attenuation
characteristic in the depth direction of an electromagnetic wave
(RF current) flowing through a conductor. As shown in FIG. 8, the
amplitude of an electromagnetic wave (RF current) flowing through
the surface layer of a conductor by means of the skin effect is
attenuated in the depth direction of the conductor, and decreases
to about 5% at a depth three times larger than the skin depth
.delta.. Accordingly, if the height of the protrusions 70 is set to
be three times the skin depth .delta. or more, most of the RF
current i (about 95% or more) can flow into the protrusions 70,
thereby efficiently discharging an RF power from the protrusions 70
to the plasma PZ. For example, where the susceptor 12 and
protrusions 70 are made of aluminum, and the frequency of the RF
power supply 32 is set at 100 MHz, the skin depth .delta. is 8
.mu.m. Accordingly, the height of the protrusions 70 should be set
at 24 .mu.m or more.
[0110] The width of the protrusions 70, particularly the width in
the electrode radial direction, is also important. The width in the
electrode radial direction is preferably larger for the RF current
i to sufficiently flow up to the top surface of the protrusions 70.
This width may be set to be three times the skin depth .delta. or
more, and preferably to be within a range of 30 .mu.m to 500 .mu.m
for a frequency of 100 MHz.
[0111] The distance between the protrusions 70 may also be selected
to optimize the impedance ratio Z.sub.12a/Z.sub.70 between the
protrusions 70 and bottom portion 12a. For example, this distance
is preferably set to be within a range of 100 .mu.m to 1 mm for 100
MHz.
[0112] FIG. 10 is a sectional side view showing a structure in
which an electrostatic chuck is integrally formed with a susceptor
according to the first embodiment. As shown in FIG. 10, an
electrostatic chuck 40 has a lower insulating film 40b formed on
the main surface of the susceptor 12, and more specifically on the
protrusions 70 and dielectric body 72. An electrode film 40a is
disposed on the lower insulating film 40b, and an upper insulating
film 40c is disposed on the electrode film 40a.
[0113] FIG. 11 is a view showing the impedance ratio characteristic
between the protrusions and bottom portion in the susceptor
structure with the electrostatic chuck shown in FIG. 10. In FIG.
11, the horizontal axis denotes as a parameter the ratio
S.sub.12a/S.sub.70 between the total area S.sub.70 of the
protrusions 70 (specifically the protrusion top surface) and the
total area S.sub.12a of the bottom portion 12a on the main surface
of the susceptor 12. Further, in FIG. 11, the vertical axis denotes
the ratio D2/D1 between the distance (D1) from the top surface of
the protrusions 70 to the electrode film 40a and the distance (D2)
from the susceptor bottom portion 12a to the electrode film 40a.
Functional values in FIG. 11 denote the ratio Z.sub.12a/Z.sub.70
between the impedance Z.sub.70 of the protrusions 70 and the
impedance Z.sub.12a of the bottom portion 12a on the main surface
of the susceptor 12.
[0114] In the multi-layered structure shown in FIG. 10, the film
thickness D1 of the lower insulating film 40b of the electrostatic
chuck 4 is an important factor. This film thickness D1 is
preferably set relatively low, as long as it is compatible with the
other conditions. As shown in FIG. 11, as D2/D1 is set larger,
Z.sub.12a/Z.sub.70 becomes larger. Judging from FIG. 11, this ratio
D2/D1 is preferably set at 2 (times) or more.
[0115] Further, the impedance ratio Z.sub.12a/Z.sub.70 (the
functional value in FIG. 11) can also be increased, by setting the
ratio S.sub.12a/S.sub.70 smaller, i.e., by setting the occupation
area ratio of the protrusions 70 higher. As described above, as the
impedance ratio Z.sub.12a/Z.sub.70 is set larger, the RF power
application rate from the protrusions 70 to the plasma PZ is
increased. Judging from FIG. 11, the ratio S.sub.12a/S.sub.70 is
preferably set at 4 (times) or less.
[0116] FIGS. 12A to 12F are views showing steps of a method of
manufacturing the susceptor structure with the electrostatic chuck
shown in FIG. 10.
[0117] First, as shown in FIG. 12A, the main surface of a susceptor
body (electrode substrate) 12 made of, e.g., aluminum is covered
with a mask 74 made of, e.g., a resin and having openings 74a
corresponding to protrusions 70. This mask 74 is arranged such that
the planar shape and planar size of each of the openings 74a define
the planar shape and planar size of each of the protrusions 70. The
depth of the openings 74a defines the height of the protrusions 70
(D2-D1: 150 .mu.m, for example).
[0118] Then, as shown in FIG. 12B, the material of the protrusions
70, such as aluminum (Al), is applied from above the mask 74 by
thermal spray, over the entire main surface of the susceptor body
12. The openings 74a of the mask 74 are thereby filled with
aluminum up to the height of the mask top surface.
[0119] Then, the mask 74 is removed from the main surface of the
susceptor body 12 by, e.g. dissolving it with a chemical solution.
As a consequence, as shown in FIG. 12C, a number of protrusions 70
with a predetermined size are discretely left in a predetermined
distribution pattern on the main surface of the susceptor body
12.
[0120] Then, as shown in FIG. 12D, a dielectric body material, such
as alumina (Al.sub.2O.sub.3), is applied by thermal spray, over the
entire main surface of the susceptor body 12. Thus, a dielectric
film (72, 40b) is formed to have a film thickness reaching a
predetermined height (D1: 50 .mu.m, for example) relative to the
top surface of the protrusions 70.
[0121] Then, as shown in FIG. 12E, the material of the electrode
film 40a of an electrostatic chuck 40, such as tungsten (W), is
applied by thermal spray, on the dielectric film 40b over the
entire main surface of the susceptor body 12. Thus, an electrode
film 40a having a predetermined film thickness (D3: 50 .mu.m, for
example) is formed.
[0122] Then, as shown in FIG. 12F, a dielectric body material, such
as alumina, is applied by thermal spray, on the electrode film 40a
over the entire main surface of the susceptor body 12. Thus, the
upper insulating film 40c of the electrostatic chuck 40 is formed
to have a predetermined film thickness (D4: 200 .mu.m, for
example).
[0123] According to this embodiment, the dielectric body 72 filling
the portion around the protrusions 70 (to cover the bottom portion
12a) and the lower insulating film 40b of the electrostatic chuck
40 are simultaneously and integrally formed by one thermal spray
step on the main surface of the susceptor body 12.
[0124] In the embodiment described above, the protrusions 70
disposed on the main surface of the susceptor 12 are columnar, but
the protrusions 70 may have an arbitrary shape. FIG. 13 is a view
showing a modified susceptor structure according to the first
embodiment. In the modification shown in FIG. 13, a number of
annularly protrusions 70 are concentrically disposed. Also in the
susceptor structure shown in FIG. 13, when an RF current flows from
the electrode edge portion to the central portion, an RF power is
efficiently discharged toward the plasma PZ from the protrusions 70
having a lower impedance rather than from the bottom portion 12a.
The protrusions 70 are disposed with a distribution characteristic
such that the area density gradually increases from the electrode
central portion to the electrode edge portion. With this
arrangement, the uniformity of electric field intensity is
improved, and thus the uniformity of plasma density is improved, in
the electrode radial direction.
[0125] FIG. 14 is a sectional side view showing an arrangement in
which an electrode protrusion structure according to the first
embodiment is applied to an upper electrode. Specifically, a
counter electrode or upper electrode 38 may be structured in
accordance with the embodiment described above, as shown in FIG.
14, i.e., a number of protrusions 70 functioning as small
electrodes are discretely disposed on the main surface of the
electrode.
[0126] In the structure shown in FIG. 14, the main surface of an
electrode plate 56 disposed on a showerhead 38 (the bottom surface,
i.e., the surface facing the plasma generation space) is provided
with a number of protrusions 70 and a dielectric body 72 filling
the portion around the protrusions 70 (on a back portion 56b). Gas
delivery holes 56a are formed to vertically pass through the
protrusions 70. With this arrangement, the upper electrode 38
receives an RF current from the plasma PZ mainly through the
protrusions 70. Accordingly, the uniformity of plasma density is
further improved by suitably selecting the properties of the
protrusions 70 of the upper electrode 38. For example, the
protrusions 70 may be arrayed with a distribution characteristic
such that the area density gradually increases from the electrode
central portion to the electrode edge portion.
[0127] FIG. 15 is a plan view showing an electrode structure (a
susceptor 12) according to a second embodiment of the present
invention. FIG. 16 is an enlarged partial and sectional side view
of the structure. FIG. 17 is a view showing a distribution
characteristic concerning the recess number density on the
structure. The main surface of the susceptor 12 is provided with a
number of columnar recesses 80 which have a constant size and are
discretely arrayed. Since the recesses 80 are dent opposite the
counter electrode or plasma PZ, they are electrically coupled with
the plasma PZ with a higher impedance than the top portion 12a of
the main surface. Accordingly, the RF power carried by an RF
current i flowing through the surface layer on the main surface of
the susceptor 12 is discharged mainly from the top portion 12a
toward the plasma PZ.
[0128] As shown in FIG. 16, a dielectric body 82 is preferably
disposed in the recesses 80. With this arrangement, the impedance
ratio Z.sub.80/Z.sub.12a between the recesses 80 and top portion
12a can be set higher on the main surface of the susceptor 12. In
other words, it is possible to increase the RF power ratio applied
to the plasma PZ through the top portion 12a.
[0129] As described above, in this embodiment, each of a number of
recesses 80 discretely arrayed on the main surface of the susceptor
12 functions as an electrode mask portion to suppress application
of an RF power to the plasma PZ. By suitably selecting properties
(shape, size, distance, density, and so forth) of the recesses 80,
the RF power application characteristic of the susceptor 12 can be
set as required.
[0130] For example, as shown in FIG. 17, the number density of the
recesses 80 can be set to have a distribution characteristic such
that the density gradually decreases from the electrode central
portion to the electrode edge portion. This arrangement make it
possible to improve the uniformity of the RF power or RF electric
field (particularly, uniformity in the radial direction) applied
from the susceptor 12 to the plasma PZ, and thus improve the
uniformity of plasma density. The other properties of the recesses
80 may be treated in accordance with essentially the same idea for
those of the protrusions 70 according to the first embodiment. For
example, the depth size and width size of the recesses 80 may be
set at three times the skin depth .delta. or more.
[0131] FIGS. 18A to 18F are views showing steps of a method of
manufacturing an electrode structure with an electrostatic chuck
integrally formed therewith, according to the second
embodiment.
[0132] First, as shown in FIG. 18A, the main surface of a susceptor
body (electrode substrate) 12 made of, e.g., aluminum is covered
with a mask 84 made of, e.g., a resin and having openings 84a
corresponding to recesses 80. This mask 84 is arranged such that
the planar shape and planar size of each of the openings 84a define
the planar shape and planar size of each of the recesses 80.
[0133] Then, as shown in FIG. 18B, solid particles (e.g., dry ice
pellets) or a fluid (e.g., high pressure jet water) is applied from
above the mask 84 by a blast method, over the entire main surface
of the susceptor body 12. Substances (aluminum) are thereby
physically removed in the openings 84a of the mask 84 to form the
recesses 80 with a required depth.
[0134] Then, the mask 84 is removed from the main surface of the
susceptor body 12. As a consequence, as shown in FIG. 18C, a number
of recesses 80 with a predetermined size are discretely left in a
predetermined distribution pattern on the main surface of the
susceptor body 12.
[0135] Then, as shown in FIG. 18D, a dielectric body material, such
as alumina (Al.sub.2O.sub.3), is applied by thermal spray, over the
entire main surface of the susceptor body 12. Thus, a dielectric
film (82, 40b) is formed to have a film thickness reaching a
predetermined height relative to the top portion 12a of the
susceptor.
[0136] Then, as shown in FIG. 18E, the material of the electrode
film of an electrostatic chuck, such as tungsten (W), is applied by
thermal spray, on the dielectric film 40b over the entire main
surface of the susceptor body 12. Thus, an electrode film 40a
having a predetermined film thickness is formed.
[0137] Then, as shown in FIG. 18F, a dielectric body material, such
as alumina, is applied by thermal spray, on the electrode film 40a
over the entire main surface of the susceptor body 12. Thus, an
upper insulating film 40c is formed to have a predetermined film
thickness.
[0138] Also, according to this embodiment, the dielectric body 82
filling the recesses 80 and the lower insulating film 40b of the
electrostatic chuck 40 are simultaneously and integrally formed by
one thermal spray step on the main surface of the susceptor body
12.
[0139] Further, although not shown, a counter electrode or upper
electrode 38 may be structured in accordance with this embodiment,
i.e., a number of recesses 80 functioning as electrode mask
portions are discretely disposed on the main surface of the
electrode. Accordingly, there may be a design such that a susceptor
12 is provided with protrusions 70 while an upper electrode 38 is
provided with recesses 80, or a design such that a susceptor 12 is
provided with recesses 80 while an upper electrode 38 is provided
with protrusions 70.
[0140] FIGS. 19 and 20 are plan views showing a lower electrode
structure and an upper electrode structure according to a third
embodiment, respectively. Specifically, FIG. 19 shows a structure
of a susceptor 12 to which the third embodiment is applied. FIG. 20
shows a structure of an upper electrode 38 (to be precise, an
electrode plate 56) to which the third embodiment is applied.
[0141] According to this embodiment, the main surface of an
electrode or the surface facing the plasma generation space (i.e.,
the bottom surface of an upper electrode 38 or the top surface of a
susceptor 12) is provided with a dielectric film or dielectric
layer 90. The dielectric film 90 is set to have a larger film
thickness at the electrode central portion than at the electrode
edge portion. The front surface of the dielectric film 90 (the
surface facing the plasma generation space) is essentially flat.
This dielectric film or dielectric layer 90 may be formed by
applying a ceramic, such as alumina (Al.sub.2O.sub.3), by thermal
spray to an electrode substrate made of, e.g., aluminum.
[0142] In this electrode structure, the electrode central portion
has a higher impedance to the plasma PZ than the electrode edge
portion. Accordingly, an RF electric field is formed such that the
intensity is enhanced at the electrode edge portion while it is
weakened at the electrode central portion. As a consequence, the
uniformity of the electric field intensity or plasma density is
improved. Particularly, in the structure shown in FIG. 19, an
electric current flowing from the backside of the electrode 12 to
the main surface by means of the skin effect and then into the
dielectric film 90 can be more easily discharged from a portion of
the film 90 with a smaller film thickness (a thinner portion of the
dielectric layer). For this reason, the RF power discharge and
plasma density are enhanced at the electrode edge portion.
[0143] FIG. 21 is a view showing a parallel-plate electrode
structure according to third embodiment. FIG. 22 is a view showing
distribution characteristics of electric field intensity in the
radial direction between electrodes, using as a parameter the film
thickness at the upper electrode central portion of the
parallel-plate electrode structure shown in FIG. 21. The film
thickness at the electrode central portion is one of the important
parameters among distribution characteristics of the film thickness
of the dielectric film 90. As shown in FIG. 21, in the
parallel-plate electrode structure including an upper electrode 38
with a circular dielectric film 90 disposed thereon, the
distribution of electric field intensity in the radial direction
between the electrodes was obtained by simulation, using as a
parameter the film thickness Dc at the upper electrode central
portion.
[0144] In this simulation, it was assumed that the target substrate
was a semiconductor wafer with a diameter of 300 mm, the upper
electrode 38 was made of aluminum, the dielectric film 90 was made
of alumina (Al.sub.2O.sub.3), and the lower electrode 12 was made
of aluminum. As shown in FIG. 22, the planar uniformity of electric
field intensity was improved with increase in the film thickness of
the electrode central portion within a range of 0.5 mm to 10 mm.
Particularly, the film thickness within a range of 8 mm to 10 mm
was preferable. In FIG. 22, the position "0" in the horizontal axis
denotes the electrode central point.
[0145] Further, such a profile is also important in that the film
thickness of the dielectric film 90 is gradually reduced from the
electrode central portion to the electrode edge portion. FIGS. 23A
to 23D are views showing specific present examples concerning the
film thickness profile of the dielectric film on an upper electrode
according to the third embodiment. FIGS. 24A and 24B are views
showing distribution characteristics of electric field intensity in
the radial direction between electrodes, obtained by the present
examples shown in FIGS. 23A to 23D and an ideal profile.
[0146] In a present example [1] shown in FIG. 23A, the film
thickness D of the dielectric film 90 is set such that D=9 mm (flat
or constant) within a region of .phi. (diameter)=0 to 30 mm, D=8 mm
(flat) within .phi.=30 to 160 mm, and D=8 to 3 mm (tapered) within
.phi.=160 to 254 mm. In a present example [2] shown in FIG. 23B, D
is set such that D=9 mm (flat) within .phi.=0 to 30 mm, D=8 mm
(flat) within .phi.=30 to 80 mm, and D=8 to 3 mm (tapered) within
.phi.=80 to 160 mm. In a present example [3] shown in FIG. 23C, D
is set such that D=9 mm (flat) within .phi.=0 to 30 mm, D=8 mm
(flat) within .phi.=30 to 160 mm, and D=8 to 3 mm (tapered) within
.phi.=160 to 330 mm.
[0147] FIG. 23D simply shows the profiles of the present examples
[1], [2], and [3] by means of lines. Further, FIG. 23D also shows
the profile of a present example [4] where D=0.5 mm (flat) within
.phi.=0 to 150 mm, and an ideal profile, although their sectional
shapes are not shown. In the ideal profile, D is set such that D=9
to 0 mm (arch-shape) within .phi.=0 to 300 mm.
[0148] As shown in FIGS. 24A and 24B, the ideal profile shows the
most preferable planar uniformity, concerning the distribution
characteristic of electric field intensity. Of the present examples
[1], [2], [3], and [4], the present examples [1] and [3] show the
best planar uniformity closest to that obtained by the ideal
profile.
[0149] Since the upper electrode 38 (electrode plate 56) receives
an RF current from diffused plasma PZ, its edge portion can be
extended outward in the radial direction to have a larger diameter
than the target substrate. The main surface of the upper electrode
38 may be provided with a thermal spray film 92 having a film
thickness of, e.g., 20 .mu.m around the dielectric film 90 or
outside thereof in the radial direction. Although not shown, the
inner wall surface of the chamber 10 may also be provided with a
similar thermal spray film 92. The thermal spray film 92 is made
of, e.g., Al.sub.2O.sub.3 or Y.sub.2O.sub.3. The front surface or
surface exposed to plasma of the dielectric film 90 and thermal
spray film 92 is essentially flat.
[0150] FIGS. 25A to 25D are views showing other specific present
examples concerning the film thickness profile of a dielectric film
on an upper electrode according to the third embodiment. FIGS. 26A
and 26B are views showing distribution characteristics of electric
field intensity in the radial direction between electrodes,
obtained by the present examples shown in FIGS. 25A to 25D.
[0151] In a present example [5] shown in FIG. 25A, the film
thickness D of the dielectric film 90 is set such that D=5 mm
(flat) within a region of .phi.=0 to 250 mm. In a present example
[6] shown in FIG. 25B, D is set such that D=9 mm (flat) within
.phi.=0 to 30 mm, and D=8 to 3 mm (tapered) within .phi.=30 to 250
mm. In a present example [7] shown in FIG. 25C, D is set such that
D=9 mm (flat) within .phi.=0 to 30 mm, and D=5 to 3 mm (tapered)
within .phi.=30 to 250 mm. FIG. 25D simply shows the profiles of
the present examples [5], [6], and [7] by means of lines.
[0152] As shown in FIGS. 26A and 26B, of the present examples [5],
[6], and [7], the present example [6] shows the most preferable
planar uniformity closest to that obtained by the ideal profile.
However, the present example [5] also well provides a practical
use. In other words, as in the present example [6], even where the
profile is formed such that the film thickness D of the dielectric
film 90 decreases essentially linearly or taper-wise from the
electrode central portion to the electrode edge portion, the planar
uniformity thereby obtained can be close to that obtained by the
arch-shaped ideal profile. Further, as in the present example [5],
even where the profile is formed such that the film thickness D of
the dielectric film 90 is almost constant (flat) from the electrode
central portion to the electrode edge portion, the planar
uniformity thereby obtained can have a practical use.
[0153] FIGS. 27A to 27C are views showing other specific present
examples concerning the film thickness and film quality profiles of
a dielectric film on an upper electrode according to the third
embodiment. FIGS. 28A and 28B are views showing distribution
characteristics of electric field intensity in the radial direction
between electrodes, obtained by the present examples shown in FIGS.
27A to 27C.
[0154] In a present example [8] shown in FIG. 27A, the film
thickness D of the dielectric film 90 is set such that D=9 mm
(flat) within a region of .phi.=0 to 30 mm, and D=8 to 3 mm
(tapered) within .phi.=30 to 250 mm. In a present example [9] shown
in FIG. 27B, D is set such that D=5 mm (flat) within .phi.=0 to 30
mm, and D=5 to 3 mm (tapered) within .phi.=30 to 250 mm. FIG. 27C
simply shows the profiles of the present examples [8] and [9] by
means of lines.
[0155] The present example [8] includes present examples [8]-A and
[8]-B different from each other, in terms of their dielectric
constant E as a parameter. As the material of the dielectric film
90, the present examples [8]-A and [8]-B employ alumina
(Al.sub.2O.sub.3) with a dielectric constant E=8.5 and silicon
oxide (SiO.sub.2) with .di-elect cons.=3.5, respectively. The
present example [9] also includes present examples [9]-A and [9]-B,
which employ alumina (Al.sub.2O.sub.3) with E=8.5 and silicon oxide
(SiO.sub.2) with .di-elect cons.=3.5, respectively.
[0156] As shown in FIGS. 28A and 28B, of the present examples [8]-A
and [9]-A both with E=8.5, the [8]-A having a larger film thickness
Dc of the electrode central portion is better than the [9]-A in the
planar uniformity of electric field intensity E. Of the present
examples [8]-B and [9]-B both with .di-elect cons.=3.5, the [9]-B
having a smaller film thickness Dc of the electrode central portion
is better than the [8]-B in the planar uniformity of electric field
intensity E.
[0157] FIG. 29 is a view showing the correlation between the
dielectric constant .di-elect cons. of a dielectric film 90 and the
film thickness Dc at the electrode central portion, the dielectric
film 90 being designed to provide a practically sufficient planar
uniformity in accordance with data points in FIGS. 28A and 28B. As
shown in this graph, the film thickness Dc at the central portion
is preferably set in accordance with the dielectric constant
.di-elect cons. of the dielectric film 90.
[0158] FIGS. 30A and 30B are views showing distribution
characteristics of organic film etching rate, obtained in a present
example A of an upper electrode according to the third embodiment
and a comparative example B, respectively, for comparison. They
show distribution characteristics of organic film etching rate (in
X and Y directions) obtained by the plasma etching apparatus (FIG.
1) according to the embodiment. The present example A uses a
dielectric film 90 according to the third embodiment on the upper
electrode 38. The comparative example B uses no dielectric film 90
on the upper electrode 38. The present example A corresponds to the
present example [1]. The main etching conditions employed here are
as follows.
[0159] Wafer diameter: 300 mm
[0160] Etching gas: NH.sub.3
[0161] Gas flow rate: 245 sccm
[0162] Gas pressure: 30 mTorr
[0163] RF power: lower side=2.4 kW
[0164] Wafer backside pressure (central portion/edge portion):
20/30 Torr (He gas)
[0165] Temperature (chamber sidewall/upper electrode/lower
electrode)=60/60/20.degree. C.
[0166] As shown in FIGS. 30A and 30B, the present example A is far
better than the comparative example B also in the planar uniformity
of etching rate, as in the distribution characteristic of electric
field intensity.
[0167] FIGS. 31A and 31B are views showing a present example of a
lower electrode according to the third embodiment and a comparative
example, respectively, for comparison. In the present example A
shown in FIG. 31A, with reference to a semiconductor wafer W with a
diameter of 300 mm, the film thickness D of a dielectric film 90 on
the susceptor 12 is set at 4 mm at the electrode central portion,
and at 200 .mu.m at the electrode edge portion. In the comparative
example B shown in FIG. 31B, a dielectric film 94 with a uniform
film thickness of 0.5 mm is disposed on the top surface of the
susceptor 12. Each of the dielectric films 90 and 94 may be made of
alumina (Al.sub.2O.sub.3).
[0168] FIGS. 32A and 32B are views showing distribution
characteristics of organic film etching rate, obtained in the
present example A shown in FIG. 31A and the comparative example B
shown in FIG. 31B, respectively, for comparison. They show
distribution characteristics of organic film etching rate (in X and
Y directions) obtained by the plasma etching apparatus (FIG. 1)
according to the embodiment. The etching conditions are the same as
those for FIGS. 30A and 30B.
[0169] As shown in FIGS. 32A and 32B, also in the case of the
susceptor (lower electrode) 12, the present example A is far better
than the comparative example B in the planar uniformity of etching
rate. Further, in terms of the value of etching rate, the present
example A is larger than the comparative example B by about 10%. As
regards the film thickness D of the dielectric film 90 at the
electrode central portion, although that of the present example A
is 4 mm, the same effect can be obtained by a thickness up to about
9 mm.
[0170] FIGS. 33A and 33B are partial and sectional views showing
present examples of an upper electrode structure according another
embodiment of the present invention. This embodiment may be
preferably applied to a structure where an upper electrode 38 is
provided with a dielectric film 90.
[0171] As shown in FIGS. 33A and 33B, the dielectric film 90
disposed on the main surface of the upper electrode 38 is covered
with a conductive shield plate 100 in part (typically near the edge
portion). This shield plate 100 is formed of, e.g., an aluminum
plate with an alumite-processed surface (92), and preferably
attached to the upper electrode 38 by screws 102 as a detachable or
replaceable member. The shield plate 100 has an opening 100a with a
required diameter .theta. at the central portion, which is
concentric with the dielectric film 90 and exposes at least the
central portion of the dielectric film 90. The thickness of the
shield plate 100 may be set at, e.g., about 5 mm.
[0172] More specifically, .theta.=200 mm in the present example A
shown in FIG. 33A, and .theta.=150 mm in the present example B
shown in FIG. 33B. In either of the present examples A and B, the
dielectric film 90 is a disc with a diameter of 250 mm, and has a
film thickness profile set such that D=8 mm (flat) within .phi.=0
to 160 mm, and D=8 to 3 mm (tapered) within .phi.=160 to 250
mm.
[0173] FIG. 34 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present examples shown in FIGS. 33A and
33B. As shown in FIG. 34, where the dielectric film 90 is partly
covered with the conductive shield plate 100, the influence of the
dielectric film 90 or reduction of electric field intensity is
remarkably attenuated or cancelled at the covered portion.
Accordingly, by adjusting the diameter .theta. of the opening 100a
of the shield plate 100 (by replacing the shield plate 100 with
another one), the distribution characteristic of electric field
intensity can be adjusted between the electrodes 12 and 38.
[0174] FIGS. 35A to 35C are partial and sectional views showing a
present example of an upper electrode structure according to
another embodiment of the present invention, a comparative example,
and a reference example, respectively. This embodiment may also be
preferably applied to a structure where an upper electrode 38 is
provided with a dielectric film 90.
[0175] As shown in FIG. 35A, in this embodiment, an electrode
portion 38f on the main surface of the upper electrode 38 radially
outside the dielectric film 90 (or outside from a diameter of
.omega. protrudes toward the susceptor 12 or toward the plasma
generation space by a required protruding amount (or extending
amount) h. In other words, the electrode portion 38f provides an
inter-electrode gap Gf smaller than an inter-electrode gap GO at
the dielectric film 90.
[0176] In the present example A shown in FIG. 35A, the dielectric
film 90 with a diameter of 80 mm has a film thickness profile set
such that D=3 mm (flat) within .phi.=0 to 60 mm, D=3 to 1 mm
(tapered) within .phi.=60 to 80 mm, and .omega.=260 mm. With
reference to an inter-electrode gap Go=40 mm at the dielectric film
90, it is set such that h=10 mm and thus an inter-electrode gap
Gf=30 mm. The outer electrode protrusion 38f has a protrusion
shoulder inclined by about 60.degree.. This inclination angle can
be arbitrarily set.
[0177] In the comparative example B shown in FIG. 35B, the upper
electrode 38 is provided with no protrusion 38f, but with a
dielectric film 90 having the same diameter and film thickness
profile as those of the present example A. In the present example C
shown in FIG. 35C, the upper electrode 38 is provided with no
protrusion 38f or dielectric film 90. In either of FIGS. 35B and
35C, the inter-electrode gap is constant at Go=40 mm in the radial
direction.
[0178] FIG. 36 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present example A, comparative example
B, and reference example C shown in FIGS. 35A to 35C. As shown in
FIG. 36, according to the present example A, the protrusion 38f
disposed outside the dielectric film 90 allows the distribution
characteristic of electric field intensity to be controlled or
adjusted such that the electric field intensity E becomes higher
near the edge of the semiconductor wafer W (a region within a
radius of about 90 mm to 150 mm from the center, in this example).
This adjustment of the electric field intensity distribution by the
protrusion 38f can be controlled by the protruding amount h, which
is preferably set at h=10 mm or more.
[0179] The position of the protrusion shoulder of the outer
electrode protrusion 38f (a value of the diameter .omega..) can be
arbitrarily selected. FIGS. 37A to 37C are partial and sectional
views showing other present examples of an upper electrode
structure, and a comparative example, respectively.
[0180] The present example A shown in FIG. 37A is set at
.omega.=350 mm, and the present example B shown in FIG. 37B is set
at .omega.=400 mm. In either of the present examples A and B, the
dielectric film 90 has a film thickness profile set such that D=8
mm (flat) within .phi.=0 to 60 mm, and D=8 to 3 mm (tapered) within
.phi.=80 to 160 mm. With reference to an inter-electrode gap Go=30
mm at the dielectric film 90, it is set such that the protruding
amount h=10 mm and thus an inter-electrode gap Gf=20 mm. The outer
electrode protrusion 38f has a protrusion shoulder inclined by
about 60 .degree.
[0181] In the comparative example C shown in FIG. 37C, the upper
electrode 38 is provided with no protrusion 38f, but with a
dielectric film 90 having the same diameter and film thickness
profile as those of the present examples A and B. The
inter-electrode gap is constant at Go=30 mm in the radial
direction.
[0182] FIG. 38 is a view showing distribution characteristics of
oxide film etching rate (normalized value), obtained by the present
examples A and B and comparative example C, shown in FIGS. 37A to
37C. AS regards the main etching conditions, the wafer diameter is
300 mm, the pressure is 15 mTorr, and the process gas is
C.sub.4F.sub.6/Ar/O.sub.2/CO. In the present examples A and B shown
in FIGS. 37A and 37B, the protrusion shoulder of the outer
electrode protrusion 38f formed on the main surface of the upper
electrode 38 is located outside the edge of the semiconductor wafer
W in the radial direction. As shown in FIG. 38, according to this
arrangement, as the position of the protrusion shoulder is closer
to the wafer edge (as .omega. decreases), the effect of increasing
the etching rate (or electric field intensity or plasma electrons
density) near the wafer edge (a region within a radius of about 70
mm to 150 mm from the center, in this example) is enhanced.
[0183] In the embodiments shown in FIGS. 35A to 38, as described
above, an electrode portion on the main surface of the upper
electrode 38 radially outside the dielectric film 90 protrudes
toward the plasma generation space. To the contrary, as shown in
FIG. 39A, the dielectric film 90 on the main surface of the upper
electrode 38 may protrude toward the plasma generation space by a
required protruding amount (or extending amount) k. FIGS. 39A to
39C are partial and sectional views showing a present example of an
upper electrode structure according to another embodiment of the
present invention, a comparative example, and a reference example,
respectively.
[0184] In the present example A shown in FIG. 39A, the dielectric
film 90 with a diameter of 250 mm has a film thickness profile set
such that D=8 mm (flat) within .phi.=0 to 160 mm, and D=8 to 3 mm
(tapered) within .phi.=160 to 250 mm. A tapered surface 90a is set
at k=5 mm toward the susceptor 12, and thus the dielectric film 90
provides an inter-electrode gap Gm=35 mm. The electrode portion
outside the dielectric film 90 in the radial direction is flat and
provides an inter-electrode gap Go=40 mm.
[0185] In the comparative example B shown in FIG. 39B, the upper
electrode 38 is provided with a dielectric film 90 having the same
film thickness profile as that of the present example A, but the
dielectric film 90 protrudes in the opposite direction (i.e., the
taper 90a is formed toward the backside). In the present example C
shown in FIG. 39C, the upper electrode 38 is provided with no
dielectric film 90. In either of FIGS. 39B and 39C, the
inter-electrode gap is constant at Go=40 mm in the radial
direction.
[0186] FIG. 40 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present example A, comparative example
B, and reference example C shown in FIGS. 39A to 39C. As shown in
FIG. 40, according to the present example A, the protrusion of the
dielectric film 90 allows the distribution characteristic of
electric field intensity to be controlled or adjusted such that the
electric field intensity E becomes higher at respective positions
in the radial direction, as compared with the comparative example B
with no protrusion. This adjustment of the electric field intensity
distribution by the protrusion can be controlled by the protruding
amount k, which is preferably set at k=5 mm or more.
[0187] FIG. 41 is a partial and sectional view showing an upper
electrode structure according to a modification of the embodiment
shown in FIGS. 35A to 38. As shown in FIG. 41, a protrusion 38f is
formed on the main surface of the upper electrode 38 radially
outside the dielectric film 90. In this respect, the edge portion
of the dielectric film 90 may be continuous to the outer electrode
protrusion 38f, or the edge portion of the dielectric film 90 may
protrude along with the outer electrode protrusion 38f.
[0188] FIGS. 42A to 42D are partial and sectional views showing
upper electrode structures according to another embodiment of the
present invention. As shown in FIGS. 42A to 42D, according to this
embodiment, a dielectric film 90 having a void 104 therein is
disposed on the main surface of the upper electrode 38, and formed
of a hollow dielectric body, such as a hollow ceramic. Also in this
embodiment, the hollow dielectric body 90 preferably has a profile
set such that the thickness is larger at the central portion than
at the edge portion in the radial direction.
[0189] The void 104 of the hollow dielectric body 90 contains a
required amount of a dielectric fluid NZ. The dielectric fluid NZ
within the void 104 counts as part of the dielectric body 90,
depending on its occupation volume. The dielectric fluid NZ is
typically preferably formed of an organic solvent (e.g., Galden),
although it may be a powder.
[0190] The void 104 may be connected at different positions (e.g.,
at the central portion and edge portion) to, e.g., pipes 106 and
108 extending from the backside of the electrode 38, which are used
as inlet and outlet ports for the dielectric fluid NZ. As shown in
FIG. 42B, when the dielectric fluid NZ is supplied into the void
104 of the hollow dielectric body 90, the dielectric fluid NZ is
fed through the pipe 106 while air is released from the void 104
through the other pipe 108. As shown in FIG. 42D, when the
dielectric fluid NZ within the void 104 is reduced, air is fed
through the pipe 106 while the dielectric fluid NZ is released from
the void 104 through the other pipe 108.
[0191] FIG. 43 is a partial and sectional view showing a specific
present example of the embodiment shown in FIGS. 42A to 42D. In
this present example, the hollow dielectric film 90 is a disc with
a diameter of 210 mm, and has a thickness profile set such that D=6
mm (flat) within .phi.=0 to 60 mm, and D=6 to 3 mm (tapered) within
.phi.=60 to 210 mm. The void 104 of the hollow dielectric body 90
has a thickness .alpha. of 2 mm, and a diameter .beta. of 180
mm.
[0192] FIG. 44 is a view showing distribution characteristics of
electric field intensity in the radial direction between
electrodes, obtained by the present example shown in FIG. 43. In
FIG. 44, a distribution characteristic A with .di-elect cons.=1 is
obtained by the state shown in FIG. 42A or a state where the void
104 of the hollow dielectric body 90 is completely empty and filled
with air. A distribution characteristic B with .di-elect cons.=2.5
is obtained by the state shown in FIG. 42C or a state where the
void 104 of the hollow dielectric body 90 is completely filled with
Galden. An arbitrary characteristic can be obtained between the
characteristics A and B by adjusting the amount of Galden contained
in the void 104.
[0193] As described above, according to this embodiment, the
dielectric constant or dielectric impedance of the entire
dielectric body 90 can be adjusted or controlled by changing the
type and amount of the dielectric fluid NZ contained in the void
104 of the hollow dielectric body 90.
[0194] FIGS. 45A to 45D are partial and sectional views showing
upper electrode structures according to a modification of the
embodiment shown in FIGS. 42A to 42D.
[0195] In the modification shown in FIG. 45A, the front surface of
a dielectric body 90 is formed of a ceramic plate 91, and the inner
wall of the void 104 facing the ceramic plate 91 is made of the
host material (aluminum) of the upper electrode 38. In other words,
a recess 38c is formed in the main surface of the upper electrode
38 in accordance with the shape of the dielectric body 90, and the
recess 38c is covered with the ceramic plate 91. A seal member 110,
such as an O-ring, is preferably disposed to seal the periphery of
the ceramic plate 91. In this case, the shape of the recess 38c or
void 104 is important, and the thickness is preferably set larger
at the central portion than at the edge portion.
[0196] In the modification shown in FIGS. 45B and 45C, a specific
region for containing the dielectric fluid NZ is limited or
localized within the space or void 104 of the hollow dielectric
body 90. For example, as shown in FIG. 45B, this space of the void
104 is localized on the central side of the dielectric body 90.
Alternatively, as shown in FIG. 45C, the thickness of the ceramic
plate 91 is changed in the radial direction (or gradually reduced
from the central portion to the edge portion), so that the space of
the void 104 described above is localized relatively on the
peripheral side. The function of adjusting the dielectric constant
by the dielectric fluid NZ can be varied by adjusting the position
or shape of the space of the void 104 within the hollow dielectric
body 90, as required.
[0197] In the modification shown in FIG. 45D, the void 104 of the
hollow dielectric body 90 is divided into a plurality of spaces,
which are controlled independently of each other in terms of the
inflow, outflow, and filling amount of the dielectric fluid NZ. For
example, as shown in FIG. 45D, an annular partition 91a integrally
formed with the ceramic plate 91 is used to divide the void 104
into a space 104A on the central side and a space 104B on the
peripheral side.
[0198] The present invention has been described with reference to
preferable embodiments independently of each other, but electrode
structures according to different embodiments may also be combined
with each other. For example, an electrode structure according to
the third embodiment or an embodiment thereafter may be combined
with an electrode structure having protrusions 70 according to the
first embodiment, or with an electrode structure having recesses 80
according to the second embodiment.
[0199] For example, it may be arranged such that an electrode
structure according to the third embodiment or an embodiment
thereafter is applied to the susceptor 12, as shown in FIG. 19,
while an electrode structure according to the first embodiment (see
FIGS. 2 and 3) is applied to the upper electrode 38, or while an
electrode structure according to the second embodiment (see FIGS.
15 and 16) is applied to the upper electrode 38. Alternatively, it
may be arranged such that an electrode structure according to the
third embodiment or an embodiment thereafter is applied to the
upper electrode 38, as shown in FIG. 20, while an electrode
structure according to the first embodiment (see FIGS. 2 and 3) is
applied to the susceptor 12, or while an electrode structure
according to the second embodiment (see FIGS. 15 and 16) is applied
to the susceptor 12.
[0200] As a matter of course, an electrode structure according to
the first, second, or third embodiment, or an embodiment thereafter
may be applied to both of the upper and lower electrodes.
Alternatively, an electrode structure according to the first,
second, or third embodiment, or an embodiment thereafter may be
applied to only one of the upper and lower electrodes, while a
conventional electrode structure is applied to the other
electrode.
[0201] The plasma etching apparatus (FIG. 1) according to the
embodiments is of the type in which an RF power for plasma
generation is applied to the susceptor 12. Alternatively, although
not shown, the present invention may be applied to the type in
which an RF power for plasma generation is applied to the upper
electrode 38. Further, the present invention may be applied to the
type in which first and second RF powers with different frequencies
are respectively applied to the upper electrode 38 and susceptor 12
(the type applying RF powers to the upper and lower sides).
Alternatively, the present invention may be applied to the type in
which first and second RF powers with different frequencies are
superposed and applied to the susceptor 12 (the type applying two
superposed frequencies to the lower side).
[0202] In a broad sense, the present invention is applicable to a
plasma processing apparatus which has at least one electrode
disposed within a process container configured to reduce the
pressure therein. Further, the present invention is applicable to a
plasma processing apparatus for another process, such as plasma
CVD, plasma oxidation, plasma nitridation, or sputtering.
Furthermore, in the present invention, the target substrate is not
limited to a semiconductor wafer, and it may be one of various
substrates for flat panel displays, or a photo-mask, CD substrate,
or printed circuit board.
[0203] With a plasma processing apparatus or an electrode plate for
a plasma processing apparatus according to the present invention,
the uniformity of plasma density is efficiently improved by the
structures and effects described above.
[0204] Further, with a method of manufacturing an electrode plate
according to the present invention, a structure can be efficiently
fabricated in which an electrostatic chuck is integrally formed
with an electrode plate for a plasma processing apparatus according
to the present invention.
[0205] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
representative embodiments shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general inventive concept as defined by the
appended claims and their equivalents.
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