U.S. patent application number 11/192029 was filed with the patent office on 2006-03-02 for plasma etching apparatus.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Hayato Aoyama, Akira Obi, Michishige Saito, Hiroshi Suzuki, Toshikatsu Wakaki, Ryoichi Yoshida, Tetsuo Yoshida.
Application Number | 20060042754 11/192029 |
Document ID | / |
Family ID | 35941387 |
Filed Date | 2006-03-02 |
United States Patent
Application |
20060042754 |
Kind Code |
A1 |
Yoshida; Ryoichi ; et
al. |
March 2, 2006 |
Plasma etching apparatus
Abstract
In order to improve a controllability of etching characteristics
by way of precisely and freely controlling a flow or a density
distribution of a processing gas introduced into a processing
chamber, a plasma etching apparatus includes, as a gas inlet for
introducing an etching gas into a plasma generation region PS in a
chamber 10, an upper gas inlet (an upper central shower head 66a
and an upper peripheral shower head 68a) for introducing a gas
through an upper electrode 38; and a side gas inlet for introducing
a gas through a sidewall of the chamber 10. The side gas inlet 104
has a side shower head 108 attached to the sidewall of the chamber
10.
Inventors: |
Yoshida; Ryoichi;
(Nirasaki-shi, JP) ; Yoshida; Tetsuo;
(Nirasaki-shi, JP) ; Saito; Michishige;
(Nirasaki-shi, JP) ; Wakaki; Toshikatsu;
(Nirasaki-shi, JP) ; Aoyama; Hayato;
(Nirasaki-shi, JP) ; Obi; Akira; (Nirasaki-shi,
JP) ; Suzuki; Hiroshi; (Nirasaki-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Minato-ku
JP
|
Family ID: |
35941387 |
Appl. No.: |
11/192029 |
Filed: |
July 29, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60635488 |
Dec 14, 2004 |
|
|
|
60603547 |
Aug 24, 2004 |
|
|
|
Current U.S.
Class: |
156/345.1 ;
257/E21.252 |
Current CPC
Class: |
H01J 37/32091 20130101;
H01J 37/32449 20130101; H01L 21/31116 20130101; H01J 37/3244
20130101 |
Class at
Publication: |
156/345.1 |
International
Class: |
H01L 21/306 20060101
H01L021/306 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 30, 2004 |
JP |
2004-224274 |
Dec 2, 2004 |
JP |
2004-349608 |
Claims
1. A plasma etching apparatus comprising: a depressurizable
processing chamber; a lower electrode for mounting thereon a
substrate to be processed in the processing chamber; an upper
electrode facing the lower electrode in the processing chamber with
a plasma generation region formed therebetween; a radio frequency
power supply unit for applying a radio frequency power between the
upper electrode and the lower electrode to thereby form a radio
frequency electric field in the plasma generation region; an upper
gas inlet for introducing a first gas including etchant gas through
the upper electrode into the plasma generation region; and a side
gas inlet for introducing a second gas including dilution gas
through a sidewall of the processing chamber into the plasma
generation region.
2. The plasma etching apparatus of claim 1, wherein the upper gas
inlet has a first mass flow control unit for independently
controlling a flow rate of the first gas.
3. The plasma etching apparatus of claim 1, wherein the first gas
is a mixed gas, and the upper gas inlet has a first mixing ratio
control unit for independently controlling a mixing ratio of the
first gas.
4. The plasma etching apparatus of claim 1, wherein the upper gas
inlet has an upper gas injection portion provided at the upper
electrode, for injecting the first gas toward the plasma generation
region.
5. The plasma etching apparatus of claim 4, wherein the upper gas
inlet has a first gas supply line for supplying the first gas
toward the upper gas injection portion and an upper gas buffer
space for accumulating the first gas supplied through the first gas
supply line in front of the upper gas injection portion.
6. The plasma etching apparatus of claim 1, wherein the side gas
inlet has a second mass flow control unit for independently
controlling a flow rate of the second gas.
7. The plasma etching apparatus of claim 1, wherein the second gas
is a mixed gas, and the side gas inlet has a second mixing ratio
control unit for independently controlling a mixing ratio of the
second gas.
8. The plasma etching apparatus of claim 1, wherein the side gas
inlet has a side gas injection portion provided at the sidewall of
the processing chamber, for injecting the second gas toward the
plasma generation region.
9. The plasma etching apparatus of claim 8, wherein the side gas
injection portions are circumferentially provided at the sidewall
of the processing chamber at regular intervals.
10. The plasma etching apparatus of claim 8, wherein the side gas
injection portion is made of a material selected from a group
consisting of Si, SiC and quartz.
11. The plasma etching apparatus of claim 8, wherein the side gas
inlet has a second gas supply line for supplying the second gas
toward the side gas injection portion and a side gas buffer space
for accumulating the second gas supplied through the second gas
supply line in front of the side gas injection portion.
12. A plasma etching apparatus comprising: a depressurizable
processing chamber; a lower electrode for mounting thereon a
substrate to be processed in the processing chamber; an upper
electrode facing the lower electrode in the processing chamber with
a plasma generation region formed therebetween; a radio frequency
power supply unit for applying a radio frequency power between the
upper electrode and the lower electrode to thereby form a radio
frequency electric field in the plasma generation region; an upper
central gas inlet for introducing a first gas including dilution
gas through a central portion of the upper electrode into the
plasma generation region; an upper peripheral gas inlet for
introducing a second gas including etchant gas through a peripheral
portion provided at an outside of the central portion of the upper
electrode along its radial direction into the plasma generation
region; and a side gas inlet for introducing a third gas including
dilution gas a sidewall of the processing chamber into the plasma
generation region.
13. The plasma etching apparatus of claim 12, wherein the upper
central gas inlet has a first mass flow control unit for
independently controlling a flow rate of the first gas.
14. The plasma etching apparatus of claim 12, wherein the first gas
is a mixed gas, and the upper central gas inlet has a first mixing
ratio control unit for independently controlling a mixing ratio of
the first gas.
15. The plasma etching apparatus of claim 12, wherein the upper
central gas inlet has an upper central gas injection portion
provided at the central portion of the upper electrode, for
injecting the first gas toward the plasma generation region.
16. The plasma etching apparatus of claim 15, wherein the upper
central gas inlet has a first gas supply line for supplying the
first gas toward the upper central gas injection portion and an
upper central gas buffer space for accumulating the first gas
supplied through the first gas supply line in front of the upper
central gas injection portion.
17. The plasma etching apparatus of claim 12, wherein the upper
peripheral gas inlet has a second mass flow control unit for
independently controlling a flow rate of the second gas.
18. The plasma etching apparatus of claim 12, wherein the second
gas is a mixed gas, and the upper peripheral gas inlet has a second
mixing ratio control unit for independently controlling a mixing
ratio of the second gas.
19. The plasma etching apparatus of claim 12, wherein the upper
peripheral gas inlet has an upper peripheral gas injection portion
provided at an outside of the central portion of the upper
electrode along its radial direction, for injecting the second gas
toward the plasma generation region.
20. The plasma etching apparatus of claim 19, wherein the upper
peripheral gas injection portion has a plurality of gas injection
openings disposed at regular intervals.
21. The plasma etching apparatus of claim 19, wherein the upper
peripheral gas inlet has a second gas supply line for supplying the
second gas toward the upper peripheral gas injection portion and an
upper peripheral gas buffer space for accumulating the second gas
supplied through the second gas supply line in front of the upper
peripheral gas injection portion.
22. The plasma etching apparatus of claim 12, wherein the side gas
inlet has a third mass flow control unit for independently
controlling a flow rate of the third gas.
23. The plasma etching apparatus of claim 12, wherein the third gas
is a mixed gas, and the side gas inlet has a third mixing ratio
control unit for independently controlling a mixing ratio of the
third gas.
24. The plasma etching apparatus of claim 12, wherein the side gas
inlet has a side gas injection portion provided at the sidewall of
the processing chamber, for injecting the third gas toward the
plasma generation region.
25. The plasma etching apparatus of claim 24, wherein the side gas
injection portions are circumferentially provided at the sidewall
of the processing chamber at regular intervals.
26. The plasma etching apparatus of claim 24, wherein the side gas
injection portion has a plurality of gas injection openings
disposed at regular intervals.
27. The plasma etching apparatus of claim 24, wherein the side gas
injection portion is made of a material selected from a group
consisting of Si, SiC and quartz.
28. The plasma etching apparatus of claim 24, wherein the side gas
inlet has a third gas supply line for supplying the third gas
toward the side gas injection portion and a side gas buffer space
for accumulating the third gas supplied through the third gas
supply line in front of the side gas injection portion.
29. The plasma etching apparatus of claim 12, further comprising a
flow rate ratio control unit for controlling a flow rate ratio of
the first and the third gas depending on processes.
30. The plasma etching apparatus of claim 12, wherein the first gas
contains all or most of an additive gas.
31. The plasma etching apparatus of claim 12, wherein the second
gas contains all or most of an additive gas.
32. The plasma etching apparatus of claim 1, wherein the first and
the third gas contain all or most of an additive gas.
33. A plasma etching apparatus comprising: a depressurizable
processing chamber; a lower electrode for mounting thereon a
substrate to be processed in the processing chamber; an upper
electrode facing the lower electrode in the processing chamber with
a plasma generation region formed therebetween; a radio frequency
power supply unit for applying a radio frequency power between the
upper electrode and the lower electrode to thereby form a radio
frequency electric field in the plasma generation region; a first
gas inlet for introducing a first gas including dilution gas
through a first region containing a central portion of the upper
electrode into the plasma generation region; a second gas inlet for
introducing a second gas including etchant gas through a second
region of the upper electrode provided at an outside of the first
region along its radial direction into the plasma generation
region; and a third gas inlet for introducing a third gas including
dilution gas through a third region of the upper electrode provided
at an outside of the second region along its radial direction into
the plasma generation region.
34. The plasma etching apparatus of claim 33, wherein the first gas
inlet has a first mass flow control unit for independently
controlling a flow rate of the first gas.
35. The plasma etching apparatus of claim 33, wherein the first gas
is a mixed gas, and the first gas inlet has a first mixing ratio
control unit for independently controlling a mixing ratio of the
first gas.
36. The plasma etching apparatus of claim 33, wherein the first gas
inlet has a first gas injection portion provided in the first
region of the upper electrode, for injecting the first gas toward
the plasma generation region.
37. The plasma etching apparatus of claim 36, wherein the first gas
inlet has a first gas supply line for supplying the first gas
toward the first gas injection portion and a first gas buffer space
for accumulating the first gas supplied through the first gas
supply line in front of the first gas injection portion.
38. The plasma etching apparatus of claim 33, wherein the second
gas inlet has a second mass flow control unit for independently
controlling a flow rate of the second gas.
39. The plasma etching apparatus of claim 33, wherein the second
gas is a mixed gas, and the second gas inlet has a second mixing
ratio control unit for independently controlling a mixing ratio of
the second gas.
40. The plasma etching apparatus of claim 33, wherein the second
gas inlet has a second gas injection portion provided in the second
region of the upper electrode, for injecting the second gas toward
the plasma generation region.
41. The plasma etching apparatus of claim 40, wherein the second
gas injection portion has a plurality of gas injection openings
disposed at regular intervals.
42. The plasma etching apparatus of claim 40, wherein the second
gas inlet has a second gas supply line for supplying the second gas
toward the second gas injection portion and a second gas buffer
space for accumulating the second gas supplied through the second
gas supply line in front of the second gas injection portion.
43. The plasma etching apparatus of claim 33, wherein the third gas
inlet has a third mass flow control unit for independently
controlling a flow rate of the third gas.
44. The plasma etching apparatus of claim 33, wherein the third gas
is a mixed gas, and the third gas inlet has a third mixing ratio
control unit for independently controlling a mixing ratio of the
third gas.
45. The plasma etching apparatus of claim 33, wherein the third gas
inlet has a third gas injection portion provided in the third
region of the upper electrode, for injecting the third gas toward
the plasma generation region.
46. The plasma etching apparatus of claim 45, wherein the third gas
injection portion has a plurality of gas injection openings
disposed at regular intervals.
47. The plasma etching apparatus of claim 45, wherein the third gas
injection portion is made of a material selected from a group
consisting of Si, SiC and quartz.
48. The plasma etching apparatus of claim 45, wherein the third gas
inlet has a third gas supply line for supplying the third gas
toward the third gas injection portion and a third gas buffer space
for accumulating the third gas supplied through the third gas
supply line in front of the third gas injection portion.
49. The plasma etching apparatus of claim 33, further comprising a
flow rate ratio control unit for controlling a flow rate ratio of
the first and the third gas depending on processes.
50. The plasma etching apparatus of claim 33, wherein the first gas
contains all or most of an additive gas.
51. The plasma etching apparatus of claim 33, wherein the second
gas contains all or most of an additive gas.
52. The plasma etching apparatus of claim 33, wherein the first and
the third gas contain all or most of an additive gas.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a plasma etching apparatus;
and, more particularly, to a parallel plate plasma etching
apparatus.
BACKGROUND OF THE INVENTION
[0002] A recent trend towards a miniaturized semiconductor device
structure in design criteria intensifies a demand for processing a
material to be etched in a cross sectional shape of a high-density
pattern. Currently, in a plasma etching apparatus for use in
manufacturing a semiconductor device or a flat panel display (FPD),
a generation of high-density plasma is indispensable for a
miniaturization of a semiconductor device structure or a high-rate
etching process for a substrate to be processed (a semiconductor
wafer, a glass substrate or the like). Accordingly, in a parallel
plate plasma etching apparatus, in order to generate the
high-density plasma, various investigations or trials have been
attempted by way of increasing a frequency of a plasma exciting
radio frequency RF from a conventional standard frequency of 13.56
MHz to a remarkably high frequency (e.g., 40 MHz or higher).
[0003] Along with the high density of the plasma, a demand for
uniformity of etching characteristics (especially, an etching rate,
an etching pattern or the like) on a substrate becomes more and
more strict. Conventionally, in the parallel plate plasma etching
apparatus, an upper electrode serves as a shower head having a
plurality of gas injection openings, and an etching gas is
discharged through the shower head toward a substrate on a lower
electrode. Further, a glow discharge occurs between the electrodes
due to a radio frequency power applied thereto, thereby generating
a plasma of the etching gas. As for the etching gas, there has been
widely used a mixed gas wherein an etchant gas containing halogen
atoms such as chlorine or fluorine is mixed with an inert gas,
e.g., Ar, and/or an additive gas, e.g., O.sub.2.
[0004] However, in the conventional parallel plate plasma etching
apparatus, it is difficult to realize uniform etching
characteristics on a substrate to be processed and, further, it is
hard to control etching characteristics, especially on a peripheral
portion of the substrate. According to the finding of the inventors
of the present invention, even if a flow rate of an etching gas to
be introduced into a processing chamber or a pressure in the
chamber is adjusted to be set at predetermined specific values, it
is difficult to precisely control a flow or a density distribution
of the etching gas in a space above a substrate, i.e., in a plasma
generation region, and especially those in a vicinity of the
peripheral portion of the substrate are likely to be nonuniform and
incontrollable.
SUMMARY OF THE INVENTION
[0005] It is, therefore, an object of the present invention to
provide a parallel plate plasma etching apparatus capable of
improving a controllability of etching characteristics by way of
precisely and freely controlling a flow or a density distribution
of a processing gas introduced into a processing chamber.
[0006] In accordance with an aspect of the present invention, there
is provided a first plasma etching apparatus including: a
depressurizable processing chamber; a lower electrode for mounting
thereon a substrate to be processed in the processing chamber; an
upper electrode facing the lower electrode in the processing
chamber with a plasma generation region formed therebetween; a
radio frequency power supply unit for applying a radio frequency
between the upper electrode and the lower electrode to thereby form
a radio frequency electric field in the plasma generation region;
an upper gas inlet for introducing a first gas including etchant
gas through the upper electrode into the plasma generation region;
and a side gas inlet for introducing a second gas including
dilution gas through a sidewall of the processing chamber into the
plasma generation region.
[0007] In the first plasma etching apparatus, the first gas
including etchant gas is introduced downward through the upper gas
inlet into the plasma generation region between the upper electrode
and the lower electrode and, at the same time, the second gas
including dilution gas is introduced inwardly through the side gas
inlet into the plasma generation region. In accordance with such
gas introduction manner for introducing and mixing different
etching gas species from two directions of the upper and the side
portion, gas species, gas mixing ratios and gas flow rates of each
system can be properly selected and adjusted and, further, a
balance between both systems can be controlled. Accordingly, it is
possible to precisely and freely control a flow or a density
distribution of a processing gas in the plasma generation region,
thereby improving a controllability of etching characteristics on a
substrate.
[0008] Preferably, the upper gas inlet has a first mass flow
control unit for independently controlling a flow rate of the first
gas. Further, in case the first gas is a mixed gas, it is
preferable to provide at the upper gas inlet a first mixing ratio
control unit for independently controlling a mixing ratio of the
first gas.
[0009] Preferably, the upper gas inlet has an upper gas injection
portion provided at the upper electrode, for injecting the first
gas toward the plasma generation region. The upper gas injection
portion preferably has a plurality of gas injection openings
disposed at regular intervals. Further, the upper gas inlet has a
first gas supply line for supplying the first gas toward the upper
gas injection portion and an upper buffer space for accumulating
the first gas supplied through the first gas supply line in front
of the upper gas injection portion.
[0010] Preferably, the side gas inlet has a second mass flow
control unit for independently controlling a flow rate of the
second gas. In case the second gas is a mixed gas, it is preferable
to provide at the side gas inlet a second mixing ratio control unit
for independently controlling a mixing ratio of the second gas.
[0011] Preferably, the side gas inlet has a side gas injection
portion provided at the sidewall of the processing chamber, for
injecting the second gas toward the plasma generation region. The
side gas injection portion preferably has a plurality of gas
injection openings disposed at regular intervals. Further, the side
gas inlet has a second gas supply line for supplying the second gas
toward the side gas injection portion and a side gas buffer space
for accumulating the second gas supplied through the second gas
supply line in front of the upper gas injection portions. The side
gas injection portion is preferably made of a material without
causing any contamination problem, e.g., Si and SiC, or a
heat-resistance material such as quartz.
[0012] A gas to be added to the etchant gas can be introduced
through the upper gas inlet and the side gas inlet while being
distributed at an arbitrary ratio. Generally, it is preferable to
introduce all or most of the additive gas through the upper gas
inlet or the side gas inlet.
[0013] In accordance with another aspect of the present invention,
there is provided a second plasma etching apparatus including: a
depressurizable processing chamber; a lower electrode for mounting
thereon a substrate to be processed in the processing chamber; an
upper electrode facing the lower electrode in the processing
chamber with a plasma generation region formed therebetween; a
radio frequency power supply unit for applying a radio frequency
between the upper electrode and the lower electrode to thereby form
a radio frequency electric field in the plasma generation region;
an upper central gas inlet for introducing a first gas including
dilution gas through a central portion of the upper electrode into
the plasma generation region; an upper peripheral gas inlet for
introducing a second gas including etchant gas through a peripheral
portion provided at an outside of the central portion of the upper
electrode along its radial direction into the plasma generation
region; and a side gas inlet for introducing a third gas including
dilution gas through a sidewall of the processing chamber into the
plasma generation region.
[0014] In the second plasma etching apparatus, the first gas
including dilution gas is introduced downward through the upper
central gas inlet into the plasma generation region between the
upper electrode and the lower electrode; the second gas including
etchant gas is introduced downward through the upper peripheral gas
inlet into the plasma generation region; and the third gas
including dilution gas is introduced inwardly (toward the center)
through the side gas inlet. In accordance with such gas
introduction manner for introducing two gas species for etching
from two directions, i.e., from above and side and mixing the first
and the third gas including dilution gas respectively through the
upper central gas inlet and the side gas inlet so that the second
gas including etchant gas introduced through the upper peripheral
gas inlet can be maintained between the central portion and the
side portion, it is possible to precisely and freely control a flow
or a density distribution of a processing gas in the plasma
generation region. Accordingly, a controllability of etching
characteristics on a substrate can be further enhanced.
[0015] Preferably, the upper central gas inlet has a first mass
flow control unit for independently controlling a flow rate of the
first gas. In case the first gas is a mixed gas, it is preferable
to provide in the upper central gas inlet a first mixing ratio
control unit for independently controlling a mixing ratio of the
first gas. Further, preferably, the upper central gas inlet has
upper central gas injection portions provided at a central portion
of the upper electrode, for injecting the first gas toward the
plasma generation region. The upper central gas injection portions
preferably have a plurality of gas injection openings disposed at
regular intervals. Further, the upper central gas inlet preferably
has a first gas supply line for supplying the first gas toward the
upper central gas injection portions and an upper central gas
buffer space for accumulating the first gas supplied through the
first gas supply line in front of the upper central gas injection
portions.
[0016] Preferably, the upper peripheral gas inlet has a second mass
flow control unit for independently controlling a flow rate of the
second gas. In case the second gas is a mixed gas, the upper
peripheral gas inlet preferably has a second mixing ratio control
unit for independently controlling a mixing ratio of the second
gas. Further, preferably, the upper peripheral gas inlet has an
upper peripheral gas injection portion provided at an outside of
the central portion of the upper electrode along its radial
direction, for injecting the second gas toward the plasma
generation region. The upper peripheral gas injection portion
preferably has a plurality of gas injection openings disposed at
regular intervals. Further, the upper peripheral gas inlet
preferably has a second gas supply line for supplying the second
gas toward the upper peripheral gas injection portion and an upper
peripheral gas buffer space for accumulating the second gas
supplied through the second gas supply line in front of the upper
peripheral gas injection portion.
[0017] Preferably, the side gas inlet has a third mass flow control
unit for independently controlling a flow rate of the third gas. In
case the third gas is a mixed gas, the side gas inlet preferably
has a third mixing ratio control unit for independently controlling
a mixing ratio of the third gas. Further, preferably, the side gas
inlet has side gas injection portions provided on a sidewall of the
processing chamber, for injecting the third gas toward the plasma
generation region. The side gas injection portion preferably has a
plurality of gas injection openings disposed at regular intervals
and preferably are circumferentially provided on the sidewall of
the processing chamber at regular intervals. Furthermore, the side
gas inlet preferably has a third gas supply line for supplying the
third gas toward the side gas injection portion and a side buffer
space for accumulating the third gas supplied through the third gas
supply line in front of the side gas injection portion. The side
gas inlet is preferably made of a material without causing any
contamination problem, e.g., Si and SiC, or a heat-resistance
material such as quartz.
[0018] A gas to be added to the etchant gas can be introduced
through the upper central gas inlet, the upper peripheral gas inlet
and the side gas inlet while being distributed at an arbitrary
ratio. Generally, it is preferable to introduce all or most of the
additive gas through the upper central gas inlet or the upper
peripheral gas inlet and the side gas inlet.
[0019] In accordance with still another aspect of the present
invention, there is provided a third plasma etching apparatus
including: a depressurizable processing chamber; a lower electrode
for mounting thereon a substrate to be processed in the processing
chamber; an upper electrode facing the lower electrode in the
processing chamber with a plasma generation region formed
therebetween; a radio frequency power supply unit for applying a
radio frequency between the upper electrode and the lower electrode
to thereby form a radio frequency electric field in the plasma
generation region; a first gas inlet for introducing a first gas
including dilution gas through a first region containing a central
portion of the upper electrode into the plasma generation region; a
second gas inlet for introducing a second gas including etchant gas
through a second region of the upper electrode provided at an
outside of the first region along its radial direction into the
plasma generation region; and a third gas inlet for introducing a
third gas including dilution gas through a third region of the
upper electrode provided at an outside of the second region along
its radial direction into the plasma generation region.
[0020] In the third plasma etching apparatus, the first gas
including dilution gas is introduced downward through the first
upper gas inlet into the plasma generation region between the upper
electrode and the lower electrode; the second gas including etchant
gas is introduced downward through the second upper gas inlet into
the plasma generation region; and the third gas including dilution
gas is introduced downward through the third gas inlet into the
plasma generation region. In accordance with such gas introduction
manner for introducing and mixing the first and the third gas
including dilution gas respectively through the first and the third
upper gas inlet so that the second gas including etchant gas
introduced through the second upper gas inlet located at a middle
portion of the upper electrode in a diametric direction, can be
maintained between the central portion and the peripheral portion,
it is possible to precisely and freely control a flow or a density
distribution of a processing gas in the plasma generation region.
Accordingly, a controllability of etching characteristics on a
substrate can be further improved.
[0021] Preferably, the first upper gas inlet has a first mass flow
control unit for independently controlling a flow rate of the first
gas. In case the first gas is a mixed gas, the first upper gas
inlet preferably has a first mixing ratio control unit for
independently controlling a mixing ratio of the first gas. Further,
Preferably, the first upper gas inlet has a first upper gas
injection portion provided in the first region of the upper
electrode, for injecting the first gas toward the plasma generation
region. The first upper gas injection portion preferably has a
plurality of gas injection openings disposed at predetermined
specific intervals. Further, the first upper gas inlet preferably
has a first gas supply line for supplying the first gas toward the
first upper gas injection portion and a first upper gas buffer
space for accumulating the first gas supplied through the first
upper gas supply line in front of the first upper gas injection
portion.
[0022] Preferably, the second upper gas inlet has a second mass
flow control unit for independently controlling a flow rate of the
second gas. In case the second gas is a mixed gas, the second upper
gas inlet preferably has a second mixing ratio control unit for
independently controlling a mixing ratio of the second gas.
Further, preferably, the second upper gas inlet has a second upper
gas injection portion provided in the second region of the upper
electrode, for injecting the second gas toward the plasma
generation region. It is preferable that the second upper gas
injection portion has a plurality of gas injection openings
disposed at predetermined specific intervals. Further, the second
upper gas inlet preferably has a second gas supply line for
supplying the second gas toward the second upper gas injection
portion and a second upper buffer space for accumulating the second
gas supplied from the second gas supply line in front of the second
upper gas injection portion.
[0023] In accordance with a preferred embodiment of the present
invention, the third upper gas inlet has a third mass flow control
unit for independently controlling a flow rate of the third gas. In
case the third gas is a mixed gas, the third upper gas inlet has a
third mixing ratio control unit for independently controlling a
mixing ratio of the third gas. Further, preferably, the third upper
gas inlet has a third upper gas injection portion provided in the
third region of the upper electrode, for injecting the third gas
toward the plasma generation region. The third upper gas injection
portion has a plurality of gas injection openings disposed at
predetermined specific intervals. Further, the third upper gas
inlet has a third gas supply line for supplying the third gas
toward the third upper gas injection portion and a third upper
buffer space for accumulating the third gas supplied through the
third gas supply line in front of the third upper gas injection
portion. The third upper gas inlet is made of a material without
causing any contamination problem, e.g., Si and SiC, or a
heat-resistance material such as quartz.
[0024] A gas to be added to the etchant gas can be introduced
through the first, the second and the third upper gas inlet while
being distributed at an arbitrary ratio. Generally, it is
preferable to introduce all or most of the additive gas through the
second upper gas inlet or the first and the third upper gas
inlet.
[0025] In accordance with the plasma etching apparatus of the
present invention, by the aforementioned configuration and
operation, it is possible to precisely and freely control a flow or
a density distribution of a processing gas introduced into a
processing chamber, so that etching characteristics can be
improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] FIG. 1 is a schematic cross-sectional view of a composition
of a plasma etching apparatus in accordance with a preferred
embodiment of the present invention;
[0027] FIG. 2 shows an enlarged cross-sectional view of principal
parts of a composition of surroundings of an upper electrode of the
plasma etching apparatus;
[0028] FIG. 3 illustrates a fragmentary sectional top view
depicting a detailed composition of a side gas inlet in accordance
with a first preferred embodiment;
[0029] FIG. 4 describes a processing gas flow rate control system
in accordance with the first preferred embodiment;
[0030] FIG. 5 provides a top view showing a distribution pattern of
gas injection openings in an upper shower head in accordance with
the first preferred embodiment;
[0031] FIG. 6 presents a top view illustrating a distribution
pattern of gas injection openings in a side shower head in
accordance with the first preferred embodiment;
[0032] FIG. 7 represents a schematic cross-sectional view
schematically depicting a processing gas flow in a chamber in
accordance with the first preferred embodiment;
[0033] FIG. 8 offers a schematic top view schematically depicting
the processing gas flow in the chamber in the first preferred
embodiment;
[0034] FIG. 9 illustrates a composition of principal parts of a gas
introduction mechanism in accordance with a second preferred
embodiment;
[0035] FIG. 10 describes a composition of a processing gas flow
rate control system in accordance with the second preferred
embodiment;
[0036] FIG. 11 provides a schematic sectional view schematically
depicting a processing gas flow in a chamber in accordance with the
second preferred embodiment;
[0037] FIG. 12 presents an additional example of a processing gas
flow rate control system in accordance with the second preferred
embodiment;
[0038] FIG. 13A represents a graph of a pressure being monitored
for a maintenance of two PCVs forming a flow rate ratio control
unit of the processing gas flow rate control system;
[0039] FIG. 13B depicts a monitored pressure difference in FIG.
13A;
[0040] FIG. 14A is a wave form chart showing time characteristics
of a monitored pressure (pressure measurement value) obtained from
an examination of `gas pressure stability check`;
[0041] FIG. 14B illustrates another wave form chart depicting time
characteristics of a monitored pressure (pressure measurement
value) obtained from an examination of `gas pressure stability
check`;
[0042] FIG. 15A provides span characteristics of a correlation
between a gas flow rate and a pressure (responsiveness of the gas
flow rate to the pressure);
[0043] FIG. 15B depicts another span characteristics of a
correlation between a gas flow rate and a pressure;
[0044] FIG. 16 describes a schematic sectional view illustrating
locations of coolant passageways in an upper electrode of the
plasma etching apparatus in accordance with the preferred
embodiments;
[0045] FIG. 17 is a top view showing coolant flow directions in the
coolant passageways of the upper electrode;
[0046] FIG. 18 provides a cross-sectional view illustrating cross
sectional shapes of the coolant passageways of the upper
electrode;
[0047] FIG. 19 presents a fragmentary sectional view showing a
composition of a joint portion of a processing gas introduction
line connected to an upper shower head;
[0048] FIG. 20A is a fragmentary enlarged side view (separated
state) of principal parts of a chamber separating/coupling portion
in a plasma etching apparatus in accordance with a preferred
embodiment;
[0049] FIG. 20B offers a fragmentary enlarged sectional view
(separated state) of the principal parts in FIG. 20A;
[0050] FIG. 21A provides a fragmentary enlarged side view (coupled
state) of the principal parts of the chamber separating/coupling
portion in the plasma etching apparatus in accordance with a
preferred embodiment;
[0051] FIG. 21B offers a fragmentary enlarged sectional view
(coupled state) of the principal parts in FIG. 21A;
[0052] FIG. 22 depicts an overall perspective view illustrating an
attachment state and a structure of an EMI shield spiral in a
preferred embodiment; and
[0053] FIG. 23 represents a perspective view describing a structure
of the EMI shield spiral in the preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0054] Hereinafter, preferred embodiments of the present invention
will be described with reference to the accompanying drawings.
[0055] FIG. 1 shows a composition of a plasma etching apparatus in
accordance with a preferred embodiment of the present invention.
The plasma etching apparatus is a capacitively coupled plasma
etching apparatus of a parallel plate electrode structure having a
cylindrical chamber (processing chamber) 10 made of aluminum,
wherein an inner wall surface thereof is covered with an alumina
film or an yttrium oxide (Y.sub.2O.sub.3) film. The chamber 10 is
frame grounded.
[0056] A columnar susceptor support 14 is provided on a bottom of
the chamber 10 via an insulating plate 12 made of ceramic or the
like. Further, a susceptor 16 made of, e.g., aluminum is installed
on the susceptor support 14. The susceptor 16 forms a lower
electrode of a parallel plate electrode structure, and a
semiconductor wafer W as a substrate to be processed is mounted
thereon.
[0057] Provided on top of the susceptor 16 is an electrostatic
chuck 18 for supporting the semiconductor wafer W with the help of
an electrostatic adsorptive force. The electrostatic chuck 18 has a
structure in which an electrode 20 made of a conductive film is
inserted by being sandwiched between a pair of insulating layers or
sheets, and a DC power supply 22 is electrically connected to the
electrode 20. Further, the semiconductor wafer W is adsorptively
held on the electrostatic chuck 18 by a Coulomb force generated by
a DC voltage from the DC power supply 22.
[0058] Provided on a top surface of the susceptor 16 so as to
surround the electrostatic chuck 18 is a focus ring 24 made of,
e.g., silicon for improving an etching uniformity. A cylindrical
inner wall member 26 made of, e.g., quartz is provided on lateral
surfaces of the susceptor 16 and the susceptor support 14.
[0059] A coolant chamber 28 is circumferentially provided inside
the susceptor support 14. A coolant, e.g., cooling water kept at a
predetermined temperature is supplied from a chiller unit (not
shown) installed at an outside into the coolant chambers 28 through
lines 30a and 30b to be circulated therein, so that a processing
temperature of the semiconductor wafer W on the susceptor 16 can be
controlled by using the temperature of the coolant. Moreover, a
thermally conductive gas, e.g., He gas, is supplied from a
thermally conductive gas supply unit (not shown) to a space between
the top surface of the electrostatic chuck 18 and a bottom surface
of the semiconductor wafer W through a gas supply line 32.
[0060] An upper electrode 34 is installed above the susceptor 16 so
as to face the susceptor 16 in parallel. Furthermore, a space
between the upper and the lower electrode 16 and 34 forming a
parallel plate electrode structure becomes a plasma generation
region PS. The upper electrode 34 forms a facing surface, i.e., a
surface being in contact with the plasma generation region PS while
facing the semiconductor wafer W on the susceptor (lower electrode)
16.
[0061] The upper electrode 34 includes an annular or a donut-shaped
outer upper electrode 36 which faces the susceptor 16 and is
separated therefrom by a predetermined distance; and an insulated
circular plate shaped inner upper electrode 38 provided in an inner
space of the outer upper electrode 36 along its radial direction.
The outer and the inner upper electrode 36 and 38 play a main and a
secondary role in a plasma generation, respectively.
[0062] Hereinafter, arrangements around the upper electrode 34 in
this embodiment will be described in detail with reference to FIG.
2. As shown in FIG. 2, the outer upper electrode 36 is divided into
an upper electrode member 36A and a lower electrode member 36B. The
upper electrode member 36A that is a main body is formed of, e.g.,
alumite-treated aluminum. The replaceable lower electrode member
36B is made of, e.g., silicon and detachably fixed to the upper
electrode member 36A with bolts (not shown) or the like in such a
way that it is protruded downwardly from a bottom surface of the
inner upper electrode 38 by a protruding amount H. Provided between
the electrode members 36A and 36B is a coating or sheet 40 for
increasing a thermal conductance.
[0063] The protruding amount H and an inner diameter .phi. of the
lower electrode member 36B of the outer upper electrode 36
determine a strength, a direction or the like of an electric field
applied from the outer or the inner upper electrode 36 or 38 to the
plasma generation region and further serve as factors for
controlling spatial distribution characteristics of a plasma
density.
[0064] When a high-density plasma is generated, the protruding
amount H affects uniformity in an electron density spatial
distribution along a diametrical direction of the semiconductor
wafer. According to experimental data of the inventors, the
protruding amount H is preferably smaller than or equal to 25 mm
and, more preferably, about 20 mm. The important thing is that the
lower electrode member 36B, i.e., a protrusion of the outer upper
electrode 36, serves to confine the plasma in the plasma generation
region by forming an electric field from a peripheral portion
toward an inner portion thereof along its radial direction in the
plasma generation region. Accordingly, in order to achieve the
uniformity in the plasma density spatial distribution
characteristics, the lower electrode member 36B is preferably
positioned further outside in a radial direction from an edge
portion of the semiconductor wafer W. Meanwhile, a radial width of
the lower electrode member 36B is not critical, so that it can be
arbitrarily selected.
[0065] In this embodiment, the lower electrode member 36B is formed
to have a tapered surface 37 such that the protruding amount
thereof gradually decreases toward its central portion, thereby
resulting in no right-angled portion (corner portion) formed
thereon. With such a tapered surface structure having no angled
portion, it is possible to avoid or suppress an adhesion of
reaction products generated by a plasma etching.
[0066] An annular gap of about 0.25 to 2.0 mm is formed between the
outer upper electrode 36 and the inner upper electrode 38. Further,
a dielectric material 42 made of, e.g., quartz is provided in the
gap, thereby forming a capacitor between the electrodes 36 and 38
having the dielectric material 42 inbetween. The capacitance
C.sub.42 is selected or adjusted to be set at a desired value
determined on the basis of a size of the gap and a dielectric
constant of the dielectric material 42. Airtightly attached between
the outer upper electrode 36 and a sidewall of the chamber 10 is an
annular insulating shielding member 44 made of, e.g., alumina
(Al.sub.2O.sub.3).
[0067] A first radio frequency power supply 54 is electrically
connected to the upper electrode member 36A of the outer upper
electrode 36 via a matching unit 46, an upper power feed rod 48, a
connector 50 and a cylindrical power feeder 52. The first radio
frequency power supply 54 outputs a radio frequency power of 40 MHz
or higher, e.g., 60 MHz, thereby generating a high-density plasma
in the plasma generation region. The matching unit 46 matches a
load impedance to an internal (or output) impedance of the first
radio frequency power supply 54. When the plasma is generated in
the chamber 10, the matching unit 46 serves to make the output
impedance of the first radio frequency power supply 54 and the load
impedance be seemingly matched to each other. An output terminal of
the matching unit 46 is connected to a top end of the upper power
feed rod 48.
[0068] The power feeder 52 is made of a conductive plate, e.g., an
aluminum or copper plate, of a cylindrical or conical shape or the
like. A lower portion thereof is connected to the upper electrode
member 36A of the outer upper electrode 36 continuously along a
circumferential direction, whereas an upper portion thereof is
electrically connected to a lower portion of the upper power feed
rod 48 by the connector 50. Outside the power feeder 52, a sidewall
of the chamber 10 upwardly extends to a position higher than the
upper electrode 34 to form a cylindrical grounding conductor 10a.
An upper portion of the cylindrical grounding conductor 10a is
electrically insulated from the upper power feed rod 48 by a
general insulation member 56. In such a configuration, a coaxial
cable path having the power feeder 52 and the outer upper electrode
36 as a waveguide is formed by the power feeder 52, the outer upper
electrode 36 and the cylindrical grounding conductor 10a in a load
circuit, viewed from the connector 50.
[0069] As shown in FIG. 2, a shielding member 58 is provided on
bottom surfaces of a part of the lower electrode member 36B of the
outer upper electrode 36 and the insulating shielding member 44.
The shielding member 58 is made of, e.g., a thin aluminum plate
having an alumite-treated surface, and physically and electrically
coupled to a sidewall of the processing chamber 10. Further, the
shielding member 58 is horizontally extended from the sidewall of
the processing chamber 10 and covers the bottom surfaces of the
lower electrode member 36B and the insulating shielding member 44
in a non-contact state or an insulating state. The shielding member
58 serves to block or seal a radio frequency discharge from the
bottom surfaces of the lower electrode member 36B of the outer
upper electrode 36 and the insulating shielding member 44, thereby
suppressing a plasma generation right under those bottom surfaces.
Accordingly, the plasma can be more effectively confined in a
region right above the semiconductor wafer W.
[0070] Referring back to FIG. 1, the inner upper electrode 38
includes an electrode plate 60 having a plurality of gas injection
openings 60a, the electrode plate 60 being formed of a
semiconductor material such as silicon, silicon carbide or the
like; and an electrode support 62 formed of a conductive material,
e.g., aluminum, whose surface is treated by an anodic oxidization,
for detachably supporting the electrode plate 60.
[0071] The inner upper electrode 38 serves as a part of an upper
gas introduction mechanism to be described later. Provided inside
the electrode support 62 are two upper buffer spaces, i.e., an
upper central buffer space 66 and an upper peripheral buffer space
68, partitioned by an annular partition member 64 formed of, e.g.,
an O-ring. Moreover, an upper central shower head 66a is formed by
the upper central buffer space 66 and a plurality of gas injection
openings 60a provided in a bottom surface thereof, whereas an upper
peripheral shower head 68a is formed by the upper peripheral buffer
space 68 and a plurality of gas injection openings 60a provided in
a bottom surface thereof. Gas types, gas mixing ratios, gas flow
rates or the like can be independently selected or controlled in
the upper central shower head 66a and the upper peripheral shower
head 68a, respectively.
[0072] The electrode plate 60 of the upper electrode 34 is an
exchangeable component consumed by an exposure to a plasma.
Further, since reaction products are attached to surfaces of the
electrode plate 60 and the gas injection openings 60a, a
maintenance work is required to remove them. Accordingly, the
chamber 10 is dividable into an upper and a lower chamber assembly
along a line X.sub.1-X.sub.1 shown in FIG. 1, and in-chamber
members can be taken out by opening and removing the upper
assembly.
[0073] Electrically connected to the electrode support 62 of the
inner upper electrode 38 is the first radio frequency power supply
54 via the matching unit 46, the upper power feed rod 48, the
connector 50 and a lower power feed rod 70. A variable capacitor 72
for variably controlling a capacitance is provided in the middle of
the lower power feed rod 70.
[0074] The variable capacitor 72 adjusts a ratio, i.e., a balance
between an outer electric field strength right under the outer
upper electrode 36 (or an input power to the outer upper electrode
36) and an inner electric field strength right under the inner
upper electrode 38 (or an input power to the inner upper electrode
38). By changing a capacitance C.sub.72 of the variable capacitor
72 to increase or decrease an impedance or reactance of the
waveguide of the lower power feed rod 70 (inner waveguide), it is
possible to change a relative fraction of a voltage drop in the
waveguide of the power feeder 52 (outer waveguide) and that in the
inner waveguide and to control a ratio of the outer electric field
strength (outer input power) to the inner electric field strength
(inner input power).
[0075] As will be described later, a coolant chamber or a coolant
passageway (not shown) is provided at a top portion of the outer
and the inner upper electrode 36 and 38. Due to a coolant flowing
in the coolant passageway from a chiller unit provided at an
outside, a temperature of the upper electrode 34 can be regularly
controlled.
[0076] A gas exhaust port 74 is provided at a bottom portion of the
chamber 10, and a gas exhaust unit 78 is connected to the gas
exhaust port 74 via a gas exhaust line 76. The gas exhaust unit 78
can depressurize the plasma generation region in the chamber 10 to
a desired vacuum level with a vacuum pump such as a turbo vacuum
pump or the like. Moreover, provided at a sidewall of the chamber
10 is a gate valve (not illustrated) for opening/closing a gate for
loading/unloading the semiconductor wafer W.
[0077] In the plasma etching apparatus of this embodiment, a second
radio frequency power supply 82 is electrically connected to the
susceptor 16 serving as a lower electrode via a matching unit 80.
The second radio frequency power supply 82 outputs a radio
frequency power ranging from 2 MHz to 20 MHz, e.g., 2 MHz. Herein,
the second radio frequency power supply 82 serves to attract ions
from the high-density plasma to the semiconductor wafer W.
[0078] Electrically connected to the inner upper electrode 38 is a
low pass filter (LPF) 84 for passing the radio frequency (2 MHz)
from the second radio frequency power supply 82 through the ground
without passing the radio frequency (60 MHz) from the first radio
frequency power supply 54 therethrough. Although the LPF 84
preferably includes an LR filter or an Lc filter, it may also
include a single conducting wire capable of applying sufficient
reactance to the radio frequency (60 MHz) from the first radio
frequency power supply 54. Meanwhile, electrically connected to the
susceptor 16 is a high pass filter (HPF) 86 for passing the radio
frequency (60 MHz) from the first radio frequency power supply 54
to the ground.
First Embodiment
[0079] Hereinafter, there will be described a gas introduction
mechanism for introducing a processing gas (etching gas) into the
chamber 10 in the plasma etching apparatus. Major features of the
gas introduction mechanism in the first embodiment will be
described as follows. As a gas inlet for introducing an etching gas
into the plasma generation region PS in the chamber 10, there are
provided an upper gas inlet (the upper central shower head 66a and
the upper peripheral shower head 68a) for introducing a gas through
the upper electrode 38 side and a side gas inlet 104 for
introducing a gas through the sidewall side of the chamber 10. As
illustrated in FIG. 1, the side gas inlet 104 has a side shower
head 108 attached to the sidewall of the chamber 10.
[0080] Referring to FIG. 1, a processing gas supply source 88
provides an etchant gas to a gas supply line 90 at a desired flow
rate and a dilution gas to a gas supply line 94 at a desired flow
rate. The gas supply line 90 communicates with the upper peripheral
shower head 68a, and an opening/closing valve 92 is provided
therein. Further, the processing gas supply source 88 provides the
dilution gas to gas supply branch lines 94a and 94b at desired flow
rates, respectively. The gas supply branch line 94a communicates
with the upper central shower head 66a, and the gas supply branch
line 94b communicates with the side shower head 108. Provided in
the gas supply lines 94a and 94b are mass flow controllers (MFC) 96
and 100 and opening/closing valve 98 and 102, respectively.
[0081] In accordance with the gas introducing mechanism of this
embodiment, the etchant gas is discharged (introduced) through the
upper peripheral shower head 68a toward the plasma generation
region PS in the chamber 10 and, at the same time, the dilution gas
is discharged (introduced) through the upper central shower head
66a and the side shower head 108 toward the plasma generation
region PS in the chamber 10. Accordingly, the etchant gas and the
dilution gas are mixed in the plasma generation region PS, thereby
generating a plasma of the mixed gas.
[0082] By controlling the MFCs 96 and 100, a gas control unit 106
can arbitrarily control a flow rate and a flow rate ratio of the
dilution gas in the upper central shower head 66a and the side
shower head 108. Further, the gas control unit 106 controls a mass
flow control unit in the processing gas supply source 88.
[0083] FIG. 3 depicts a detailed composition of the side gas inlet
104 in this embodiment. As illustrated in FIG. 3, a plurality of
(four in this example) side shower heads 108 (108a, 108b, 108c and
108d), which are circumferentially spaced from each other at
regular intervals (away from the wafer gate), are installed at the
sidewall of the chamber 10.
[0084] The side shower heads 108 (108a, 108b, 108c and 108d) have
gas injection portions 110 (110a, 110b, 110c and 110d) inserted in
the chamber 10 with a thickness of 40 mm to face the plasma
generation region PS and side buffer spaces 112 (112a, 112b, 112c
and 112d) of a manifold structure provided at an outer wall of the
chamber 10 to communicate with the gas injection portions 110,
respectively. The gas injection portions 110 are provided with a
plurality of gas injection openings 114 (114a, 11b, 114c and 114d).
The gas injection portions 110 and the side buffer spaces 112 are
preferably made of a semiconductor material such as Si or SiC
causing no contamination problem or a heat-resistance material such
as quartz. A diameter of the gas injection opening 114 is
preferably about 1 mm, for example.
[0085] The gas supply line 94b from the processing gas supply
source 88 is divided into a plurality of (four) gas supply branch
lines 116 (116a, 116b, 116c and 116d) communicating with the
respective buffer spaces 112 (112a, 112b, 112c and 112d) of the
side shower heads 108 (108a, 108b, 108c and 108d). The gas supply
branch lines 116 (116a, 116b, 116c and 116d) are provided with flow
rate control valves 118 (118a, 118b, 118c and 118d), respectively.
Due to a flow rate controlling function of the flow rate control
valves 118 (118a, 118b, 118c and 118d), it is possible to uniformly
or arbitrarily and individually control a discharge amount of each
of the side shower heads 108 (108a, 108b, 108c and 108d) or a flow
rate thereof per unit area.
[0086] FIG. 4 provides a composition of a processing gas flow rate
control system in this embodiment. The processing gas supply source
88 has separate gas supply sources for supplying respective
different gases and MFCs. The separate gas supply sources are
selected depending on a material to be etched or a processing
condition. In this example, there are provided separate gas supply
sources of CxFy and CxHyFz as an etchant gas, a separate gas supply
source of Ar as a dilution gas and separate gas supply sources of
CO and O.sub.2 as an additive gas. Herein, CxFy indicates a
fluorocarbon-based fluorine compound, e.g., CF.sub.4,
C.sub.4F.sub.6, C.sub.4F.sub.8 and C.sub.5F.sub.8. Further, CxHyFz
indicates a perfluorocarbon-based fluorine compound, e.g.,
CH.sub.2F.sub.2 and CHF.sub.3. Furthermore, each of the separate
gas supply sources is turned on/off under the control of the
control unit 106, and a combination of gas species used in the
etching process can be arbitrarily selected.
[0087] A CxFy gas from the CxFy supply source or a CxHyFz gas from
the CxHyFz supply source is provided to the gas supply line 90 via
the MFC 124 or 126 and then supplied to the upper peripheral shower
head 68a provided at a top portion of the chamber 10 through the
gas supply line 90. The control unit 106 controls a flow rate of
the etchant gas, i.e., the CxFy gas or the CxHyFx gas supplied to
the upper peripheral shower head 68a, by controlling the MFC 124 or
126.
[0088] CO gas from the CO supply source, O.sub.2 gas from the
O.sub.2 supply source and Ar gas from the Ar supply source are
provided to the gas supply line 94 via the MFCs 128, 130 and 132,
respectively, and then mixed in the gas supply line 94. The control
unit 106 controls flow rates of the CO gas, the O.sub.2 gas and the
Ar gas by controlling the MFCs 128, 130 and 132 and hence a mixing
ratio of the mixed CO/O.sub.2/Ar gas.
[0089] A part of the mixed dilution gas of CO/O.sub.2/Ar formed in
the gas supply line 94 is provided to the gas supply line 94a via
the MFC 96 and then supplied to the upper central shower head 66a
provided at the top portion of the chamber 10 through the gas
supply line 94a. A remaining mixed dilution gas of CO/O.sub.2/Ar is
provided to the gas supply line 94b via the MFC 100 and then
supplied to the side shower heads 108 (108a, 108b, 108c and 108d)
provided on the sidewall of the chamber 10 through the gas supply
line 94b. The control unit 106 controls a flow rate and a flow rate
ratio of the mixed dilution gas of CO/O.sub.2/Ar supplied to the
upper central shower head 66a and those of the mixed dilution gas
of CO/O.sub.2/Ar supplied to the side shower head 108 by
controlling the MFCs 96 and 100.
[0090] In the MFCs 96, 100, 124, 126, 128, 130 and 132, opening
degrees of the flow rate control valves 96a, 100a, 124a, 126a,
128a, 130a and 132a are adjusted based on gas flow rates detected
by the flowmeters 96b, 100b, 124b, 126b, 128b, 130b and 132b,
respectively.
[0091] FIG. 5 describes an exemplary distribution pattern of gas
injection openings 60a provided in gas injection portions of the
upper central shower head 66a and the upper peripheral shower head
68a. As shown in FIG. 5, the gas injection openings 60a are spaced
from each other at prededtermined pitches or intervals in the
electrode plate 60 of the inner upper electrode 38 and are
distributed in a predetermined ratio in the upper central shower
head 66a and the upper peripheral shower head 68a partitioned by
the annular partition member 64. The illustrated distribution
pattern is for an exemplary purpose only, and a radial pattern, a
concentric pattern, a matrix pattern or the like may be
employed.
[0092] FIG. 6 presents an exemplary distribution pattern of the gas
injection openings 114 provided at the gas injection portion 110 of
the side shower head 108. In this example, the gas injection
portion 110 is formed in a rectangular shape, and the gas injection
openings 114 are spaced from each other at predetermined pitches in
a matrix pattern in the X and the Y direction. Such configuration
is an exemplary purpose only, and the gas injection portion 110 may
have a circular shape and the distribution pattern of the gas
injection openings 114 may be distributed in a radial pattern, a
concentric circular pattern or the like. Optimal shape and pattern
can be selected by repeating experiments or trials.
[0093] Hereinafter, an operation of the plasma etching apparatus in
this embodiment will be described. In the plasma etching apparatus,
in order to perform an etching process, a semiconductor wafer W to
be processed is loaded into the chamber 10 through a gate (not
shown) provided on the sidewall of the chamber and then mounted on
the susceptor 16 while a gate valve (not shown) is opened. Next, a
DC voltage is applied from the DC power supply 22 to the electrode
20 of the electrostatic chuck 18, and the semiconductor wafer W is
fixed on the susceptor 16.
[0094] Etching gases of predetermined flow rates are introduced
through the shower heads 66a, 68a and 108 of a triple system into
the plasma generation region PS between the upper electrode 34 (36
and 38) and the susceptor (lower electrode) 16 by the
aforementioned gas introduction mechanism. In other words, the
dilution gas containing an additive gas is introduced through the
upper central shower head 66a at a predetermined flow rate; the
etchant gas is introduced through the upper peripheral shower head
68a at another predetermined flow rate; and the dilution gas
containing an additive gas is introduced through the side shower
head 108 at yet another predetermined flow rate. The gases from the
triple system, which are introduced into the plasma generation
region PS, are mixed and become a mixed gas. Meanwhile, an inner
pressure of the chamber 10 is depressurized to a preset value
(e.g., 10.sup.-1 Pa to 10.sup.2 Pa) by the gas exhaust unit 78.
Moreover, a power of a radio frequency (60 MHz) for generating a
plasma is applied from the first radio frequency power supply 54 to
the upper electrode 34 (36 and 38). And also, a power of a radio
frequency (2 MHz) is applied from the second radio frequency power
supply 82 to the susceptor 16.
[0095] By application of such powers, a glow discharge is generated
between the upper electrode 34 (36 and 38) and the susceptor (lower
electrode) 16 to plasmarize the etching gas in the chamber 10.
Then, a to-be-processed surface of the semiconductor wafer W is
etched by radicals and/or ions generated in the plasma.
[0096] In such plasma etching apparatus, by applying a radio
frequency power of a radio frequency domain (above 5 MHz to 10 MHz
where ions are immovable) to the upper electrode 34, it is possible
to form a high density plasma in a desirable dissociation state
under a lower pressure condition.
[0097] Moreover, in the upper electrode 34, the outer upper
electrode 36 and the inner upper electrode 38 are used as a main
and a secondary radio frequency electrode for generating a plasma,
respectively. Since a ratio of an electric field strength applied
from the electrodes 36 and 38 to electrons right below those
electrodes can be adjusted, a spatial distribution of a plasma
density can be controlled in a diametric direction and, further,
spatial characteristics of a reactive ion etching can be
arbitrarily and precisely controlled.
[0098] In addition, in such plasma etching apparatus, most or
majority of the plasma is generated right under the outer upper
electrode 36 and then diffused to portions right under the inner
upper electrode 38. Therefore, since the inner upper electrode 38
serving as a shower head is less bombarded by plasma ions, a
sputtering at the gas injection openings 56a of the replaceable
electrode plate 60 can be effectively suppressed, resulting in a
considerably increased lifespan of the electrode plate 60.
Meanwhile, since the outer upper electrode 36 does not have gas
injection openings where an electric field is concentrated, the ion
bombardment thereto is small and, thus, the lifespan thereof is not
shortened.
[0099] In such plasma etching apparatus, types, mixing ratios, flow
rates or the like of gases introduced through the shower heads 66a,
68a and 108 of the triple system into the plasma generation region
PS in the chamber 10 are balanced. Accordingly, it is possible to
optimize the spatial distribution characteristics, e.g., an etching
rate, an etching shape or the like, for various etching
processes.
[0100] FIGS. 7 and 8 schematically represent a pattern of a flow of
a processing gas in the chamber 10 (especially, in the plasma
generation region PS). Hereinafter, a gas introduction method of
this embodiment in a specified etching process will be descried
with reference to FIGS. 7 and 8.
[0101] As a specific example, there will be described a case where
a contact hole is formed in a silicon oxide film or a silicon
nitride film for covering a semiconductor device forming a
semiconductor apparatus. In such etching process, it is preferable
to use a perfluorocarbon-based gas such as CH.sub.2F.sub.2 gas or
CHF.sub.3 gas as an etchant gas and CO gas or O.sub.2 gas as an
additive gas. However, if the perfluorocarbon-based gas is used as
the etchant gas, an organic polymer may be formed due to radicals
of an etching gas generated by a plasma excitation. Especially,
reaction products may be adhered to a peripheral region of the
semiconductor wafer W and, further, an acute tapered contact hole
tends to be formed in the peripheral region of the wafer by
deposits of the reaction products.
[0102] Therefore, as depicted in FIG. 7, a balance is adjusted such
that a flow rate of an Ar flow [3] discharged through the side
shower head 108 into the chamber 10 becomes greater than that of an
Ar flow [1] discharged through the upper central shower head 66a
into the chamber 10. With such balance adjustment, a
perfluorocarbon-based etchant gas flow [2] introduced through the
upper peripheral shower head 68a into the chamber 10 flows more
right under the inner upper electrode 38 than the outer upper
electrode 36. Accordingly, the radicals of the etchant are reduced
in the peripheral region of the semiconductor wafer W. Further,
argon ions generated by the plasmarization of Ar gas function to
remove the aforementioned reaction products by sputtering. Due to
those operations, the deposition amount of the reaction products
becomes reduced in the peripheral region of the semiconductor wafer
W, which improves the acute tapered shape of the contact hole. As a
result, a cross sectional shape of the contact hole in a surface of
the semiconductor wafer W becomes uniform.
[0103] As illustrated in FIG. 8, the Ar flow [3] discharged through
the side shower head 108 becomes extended further widely toward the
peripheral portion of the semiconductor wafer W. Thus, it is
preferable to discharge more O.sub.2 gas and CO gas both of which
are capable of removing the reaction products from the side shower
head 108.
[0104] Hereinafter, as an additional specific example of the
etching process, there will be described a case where a via hole or
a Damascene wiring groove is formed in an interlayer insulating
film of a multilayer interconnection structure provided on a top
layer of the semiconductor device. Such interlayer insulating film
is formed of an insulating layer having a lower dielectric constant
than that of a silicon oxide film, e.g., a silicon oxide film, a
SiC film, a SiOC film or the like containing a methyl group or an
ethyl group. Therefore, in case the via hole or a Damascene wiring
groove is formed in the interlayer insulating film, a hard mask
formed of a silicon oxide film or a silicon nitride film is used.
In such case, a fluorocarbon-based gas, e.g., C.sub.4F.sub.8 gas,
can be preferably used as the etchant gas.
[0105] In case such fluorocarbon-based etchant gas is used, flow
rates of the Ar flow [1] discharged through the upper central
shower head 66a into the chamber 10 and the Ar flow [3] discharged
through the side shower head 108 into the chamber 10 are adjusted
such that the former is greater than the latter. In other words,
the balance in the flow rates thereof is adjusted reversely to that
done in the case where the contact hole is formed, so that the
cross sectional profile of the via hole or the Damascene wiring
groove in the surface of the semiconductor wafer W becomes uniform.
In this case, it is preferable to introduce more CO gas or O.sub.2
gas for removing the reaction products through the upper central
shower head 66a.
[0106] By discharging Ar gas and O.sub.2 gas or CO gas for removing
the reaction products through the upper central shower head 66a and
the side shower head 108 to maintain the etchant gas introduced
through the upper peripheral shower head 68a between the central
portion and the side portion and, further, by appropriately
adjusting the balance of the gas injection amount between the upper
central shower head 66a and the side shower head 108, it is
possible to freely and optimally control the etching
characteristics on the semiconductor wafer W in various etching
processes (e.g., regardless of whether the amount of reaction
products is large or small).
Second Embodiment
[0107] Hereinafter, a gas introduction mechanism of a second
preferred embodiment, for introducing a processing gas (an etching
gas) into the chamber 10 in the plasma etching apparatus, will be
described with reference to FIGS. 9 to 11. A major feature of the
gas introduction mechanism in accordance with the second preferred
embodiment is that instead of the side gas inlet 104 in the first
preferred embodiment, a third upper shower head is provided at an
outer portion of the upper peripheral shower head 68a as a gas
inlet for introducing an etching gas into the plasma generation
region PS in the chamber 10. In other words, the gas introduction
mechanism of the second preferred embodiment includes a first upper
shower head (the upper central shower head of the first preferred
embodiment), a second upper shower head (the upper peripheral
shower head of the first preferred embodiment) and the third upper
shower head, which are sequentially provided from the central
portion of the upper electrode toward the outer portion thereof in
a diametric direction. The compositions other than the gas
introduction mechanism in the plasma etching apparatus are
identical to those of the first preferred embodiment.
[0108] FIG. 9 illustrates a composition of principal parts of the
gas introduction mechanism of the second preferred embodiment. The
inner upper electrode 38 includes an electrode plate 60 formed of a
semiconductor material such as Si, SiC or the like, the electrode
plate 60 having a plurality of gas injection openings 60a; and an
electrode support 62 formed of a conductive material, e.g.,
aluminum whose surface is treated by an anodic oxidization, for
detachably supporting the electrode plate 60.
[0109] The inner upper electrode 38 serves as a part of an upper
gas introduction mechanism to be described later. Provided inside
the electrode support 62 are three upper buffer spaces, i.e., a
first upper buffer space 66, a second upper buffer space 68 and a
third upper buffer space 208, partitioned by annular partition
members 64 and 264 formed of, e.g., O-rings. Moreover, a first
upper shower head 66a includes the first upper buffer space 66 and
a plurality of gas injection openings 60a provided in a bottom
surface thereof; a second upper shower head 68a includes the second
upper buffer space 68 and a plurality of gas injection openings 60a
provided in a bottom surface thereof; and a third upper shower head
208a includes the third upper buffer space 208 and a plurality of
gas injection openings 60a provided in a bottom surface thereof.
Gas species, gas mixing ratios, gas flow rates or the like can be
independently selected or controlled in the first, the second and
the third upper shower head 66a, 68a and 208a, respectively.
[0110] Referring to FIG. 9, a processing gas supply source 88
provides an etchant gas to a gas supply line 90 at a desired flow
rate and a dilution gas to a gas supply line 94 at a desired flow
rate. The gas supply line 90 communicates with the second upper
shower head 68a and an opening/closing valve 92 is provided
therein. Further, the processing gas supply source 88 provides the
dilution gas to gas supply lines 94a and 94c at desired flow rates,
respectively. The gas supply line 94a communicates with the first
upper shower head 66a, and the gas supply line 94c communicates
with the third upper shower head 208a. Provided in the gas supply
lines 94a and 94c are MFCs 96 and 200 and opening/closing valves 98
and 202, respectively.
[0111] In accordance with the gas introducing mechanism of the
second preferred embodiment, the etchant gas is discharged
(introduced) through the second upper shower head 68a toward the
plasma generation region PS in the chamber 10 and, at the same
time, the dilution gas is discharged (introduced) through the first
and the third upper shower head 66a and 208a toward the plasma
generation region PS in the chamber 10. Accordingly, the etchant
gas and the dilution gas are mixed in the plasma generation region
PS, thereby generating a plasma of the mixed gas.
[0112] By controlling the MFCs 96 and 200, a gas control unit 106
can arbitrarily control a flow rate and a flow rate ratio of the
dilution gas in the first and the third upper shower head 66a and
208a. Further, the gas control unit 106 controls a mass flow
control unit in the processing gas supply source 88.
[0113] FIG. 10 provides a composition of a processing gas flow rate
control system in this embodiment. The processing gas supply source
88 has separate gas supply sources for supplying respective
different gases and MFCs. The separate gas supply sources are
selected depending on a material to be etched or a processing
condition. In this example, as in the first preferred embodiment,
there are provided separate gas supply sources of CxFy and CxHyFz
as an etchant gas, a separate gas supply source of Ar as a dilution
gas and separate gas supply sources of CO and O.sub.2 as additive
gases. Further, each of the separate gas supply sources is turned
on/off under the control of the control unit 106, and a combination
of gas species used in the etching process can be arbitrarily
selected.
[0114] A CxFy gas from the CxFy supply source or a CxHyFz gas from
the CxHyFz supply source is provided to the gas supply line 90 via
the MFC 124 or 126 and then supplied to the second upper shower
head 68a provided at a top portion of the chamber 10 through the
gas supply line 90. The control unit 106 controls a flow rate of
the etchant gas, i.e., the CxFy gas or the CxHyFx gas supplied to
the second upper shower head 68a, by controlling either the MFC 124
or 126.
[0115] CO gas from the CO supply source, O.sub.2 gas from the
O.sub.2 supply source and Ar gas from the Ar supply source are
provided to the gas supply line 94 via the MFCs 128, 130 and 132,
respectively, and then mixed in the gas supply line 94. The control
unit 106 controls flow rates of the CO gas, the O.sub.2 gas and the
Ar gas by controlling the MFCs 128, 130 and 132, respectively, and
hence a mixing ratio of the mixed gas of CO/O.sub.2/Ar.
[0116] A part of the mixed dilution gas of CO/O.sub.2/Ar formed in
the gas supply line 94 is provided to the gas supply line 94a via
the MFC 96 and then supplied to the first upper shower head 66a
provided at the top portion of the chamber 10 through the gas
supply line 94a. The remaining mixed dilution gas of CO/O.sub.2/Ar
is provided to the gas supply line 94c via the MFC 200 and then
supplied to the third upper shower head 208a provided at the top
portion of the chamber 10 through the gas supply line 94c. The
control unit 106 controls a flow rate and a flow rate ratio of the
mixed dilution gas of CO/O.sub.2/Ar supplied to the first upper
shower head 66a and those of the mixed dilution gas of
CO/O.sub.2/Ar supplied to the third upper shower head 208a by
controlling the MFCs 96 and 200.
[0117] In the MFCs 96, 100, 124, 126, 128, 130 and 132, opening
degrees of the flow rate control valves 96a, 100a, 124a, 126a,
128a, 130a and 132a are adjusted based on gas flow rates detected
by the flowmeters 96b, 100b, 124b, 126b, 128b, 130b and 132b,
respectively.
[0118] Although it is not illustrated, the gas injection openings
60a provided at a gas injection portion of the first, the second
and the third upper shower head 66a, 68a and 208a are spaced from
each other at predetermined pitches or intervals in the electrode
plate 60 of the inner upper electrode 38 and are distributed in a
predetermined ratio at the first, the second and the third upper
shower head 66a, 68a and 208a partitioned by the annular partition
members 64 and 264. Further, the gas injection openings may be
distributed in a radial pattern, a concentric circular pattern, a
matrix pattern or the like.
[0119] Hereinafter, an operation of the plasma etching apparatus of
the second preferred embodiment will be described. In the plasma
etching apparatus, in order to perform an etching process, a
semiconductor wafer W to be processed is loaded into the chamber 10
through a gate (not shown) provided on the sidewall of the chamber
and then mounted on the susceptor 16 while a gate valve (not shown)
is opened. Next, a DC voltage is applied from the DC power supply
22 to the electrode 20 of the electrostatic chuck 18, and the
semiconductor wafer w is fixed on the susceptor 16.
[0120] Etching gases of predetermined flow rates are respectively
introduced from the shower heads 66a, 68a and 208a of a triple
system into the plasma generation region PS between the upper
electrode 34 (36 and 38) and the susceptor (lower electrode) 16 by
the aforementioned gas introduction mechanism. In other words, the
dilution gas containing an additive gas is introduced through the
first shower head 66a at a predetermined flow rate; the etchant gas
is introduced through the second shower head 68a at a predetermined
flow rate; and the dilution gas containing an additive gas is
introduced through the third upper shower head 208a at a
predetermined flow rate. The gases from the triple system, which
are introduced into the plasma generation region PS, are mixed and
become a mixed gas. Meanwhile, an inner pressure of the chamber 10
is depressurized to a preset value (e.g., 10.sup.-1 Pa to 10.sup.2
Pa) by the gas exhaust unit 78. Moreover, a power of a radio
frequency (60 MHz) for generating a plasma is applied from the
first radio frequency power supply 54 to the upper electrode 34 (36
and 38). And also, a power of a radio frequency (2 MHz) is applied
from the second radio frequency power supply 82 to the susceptor
16.
[0121] By application of such powers, a glow discharge occurs
between the upper electrode 34 (36 and 38) and the susceptor (lower
electrode) 16 to thereby plasmarize the etching gas in the chamber
10. Then, a to-be-processed surface of the semiconductor wafer W is
etched by radicals and/or ions generated in the plasma.
[0122] In such plasma etching apparatus of the second preferred
embodiment, species, mixing ratios, flow rates or the like of gases
introduced through the shower heads 66a, 68a and 208a of the triple
system into the plasma generation region PS in the chamber 10 are
balanced. Accordingly, it is possible to optimize the spatial
distribution characteristics such as an etching rate, an etching
shape or the like, in various etching processes.
[0123] FIG. 11 schematically represents a flow of a processing gas
in the chamber 10 (especially, in the plasma generation region PS).
Hereinafter, a gas introduction method of this embodiment in a
specified etching process will be described with reference to FIG.
11.
[0124] As a specific example, there will be described a case where
a contact hole is formed in a silicon oxide film or a silicon
nitride film for covering a semiconductor device forming a
semiconductor apparatus as in the first preferred embodiment. In
such etching process, it is preferable to use a
perfluorocarbon-based gas such as CH.sub.2F.sub.2 gas or CHF.sub.3
gas as an etchant gas and CO gas or O.sub.2 gas as an additive gas.
However, if the perfluorocarbon-based gas is used as the etchant
gas, an organic polymer may be formed due to radicals of an etching
gas generated by a plasma excitation. Especially, reaction products
may be adhered to a peripheral region of the semiconductor wafer W
and, further, an acute tapered contact hole tends to be formed in
the peripheral region of the wafer by deposits of the reaction
products.
[0125] Therefore, as depicted in FIG. 11 a balance is adjusted such
that a flow rate of an Ar flow [3] discharged through the third
upper shower head 208a into the chamber 10 becomes greater than
that of an Ar flow [1] discharged through the first upper shower
head 66a into the chamber 10. With such balance adjustment, a
perfluorocarbon-based etchant gas flow [2] introduced through the
second upper shower head 68a into the chamber 10 flows more right
under the inner upper electrode 38 than right under the outer upper
electrode 36. Accordingly, the radicals of the etchant are reduced
in the peripheral region of the semiconductor wafer W. Further,
argon ions generated by the plasmarization of Ar gas function to
remove the aforementioned reaction products by sputtering. Due to
those operations, the deposition amount of the reaction products
becomes reduced in the peripheral region of the semiconductor wafer
W, which improves an acute tapered shape of the contact hole. As a
result, a cross sectional shape of the contact hole in a surface of
the semiconductor wafer W becomes uniform.
[0126] Hereinafter, as an additional specific example of the
etching process, there will be described a case where a via hole or
a Damascene wiring groove is formed in an interlayer insulating
film of a multilayer interconnection structure provided on a top
layer of the semiconductor device, as in the first preferred
embodiment. Such interlayer insulating film is formed of an
insulating layer having a lower dielectric constant than that of a
silicon oxide film, e.g., a silicon oxide film, a SiC film, a SiOC
film or the like containing a methyl group or an ethyl group.
Therefore, in case the via hole or a Damascene wiring groove is
formed in the interlayer insulating film, a hard mask formed of a
silicon oxide film or a silicon nitride film is used. In this case,
it is preferable to use a fluorocarbon-based gas, e.g.,
C.sub.4F.sub.8 gas, as the etchant gas.
[0127] In case such fluorocarbon-based etchant gas is used, a flow
rate of the Ar flow [1] discharged through the first upper shower
head 66a into the chamber 10 and that of the Ar flow [3] discharged
through the third upper shower head 208a into the chamber 10 are
adjusted such that the former is greater than the latter. In other
words, the balance of the flow rates thereof are adjusted reversely
to that done in the case where the contact hole is formed, so that
the cross sectional profile of the via hole or the Damascene wiring
groove in the surface of the semiconductor wafer W becomes uniform.
In this case, it is preferable to introduce more CO gas or O.sub.2
gas for removing the reaction products from the first upper shower
head 66a.
[0128] By discharging Ar gas and O.sub.2 gas or CO gas for removing
the reaction products from the first and the third upper shower
head 66a and 208a to maintain the etchant gas introduced through
the second upper shower head 68a between the central portion and
the side portion and, further, by appropriately adjusting the
balance of the gas injection amount between the first and the third
upper shower head 66a and 208a, it is possible to freely and
optimally control the etching characteristics on the semiconductor
wafer W in various etching processes (e.g., regardless of whether
the amount of reaction products is large or small).
[0129] Although it is not illustrated, it is possible to add the
side shower head 108 of the first preferred embodiment to the gas
introduction mechanism of the second preferred embodiment.
[0130] Hereinafter, a modified example (an additional example) of
the processing gas flow rate control system in this embodiment will
be described with reference to FIGS. 12 to 15. FIG. 12 shows a
composition of the modified example. The parts common to the system
of FIG. 10 will be assigned like reference numerals. In such
processing gas flow rate control system, flow rates or distribution
amounts of the dilution gas to be distributed to the first and the
third shower head 66a and 208a, respectively, are controlled by a
pressure control unit PCV, thereby achieving a high responsiveness
to a change of a gas species.
[0131] Referring to FIG. 12, in the processing gas supply source
88, CO gas from the CO supply source, O.sub.2 gas from the O.sub.2
supply source and Ar gas from the Ar supply source are provided to
the gas supply line 94 via the MFCs 128, 130 and 132, respectively,
and then mixed in the gas supply line 94. The control unit 106
controls flow rates of the CO gas, the O.sub.2 gas and the Ar gas
and hence a mixing ratio of the mixed gas of CO/O.sub.2/Ar by
controlling the MFCs 128, 130 and 132.
[0132] A part of the mixed dilution gas of CO/O.sub.2/Ar formed in
the gas supply line 94 is provided to the gas supply line 94a via a
first PCV 300 and then supplied to the first shower head 66a
provided at the top portion of the chamber 10 through the gas
supply line 94a. Herein, the first PCV 300 has a pressure control
valve 300a, e.g., a normal open type air operator valve, and a
pressure sensor 300b. The remaining mixed dilution gas of
CO/O.sub.2/Ar is provided to the gas supply line 94b via a second
PCV 302 forming a mass flow control unit and then supplied to the
third shower head 208a provided at the top portion of the chamber
10 through the gas supply line 94c. The second PCV 302 also has a
pressure control valve 302a, e.g., a normal open type air operator
valve, and a pressure sensor 302b.
[0133] The gas control unit 106 adjusts respective opening degrees
of the pressure control valves 300a and 302a in the first and the
second PCV 300 and 302. In this case, it is possible to adjust the
opening degrees of both or either one of the pressure control
valves 300a and 302a. For example, an arbitrary pressure ratio can
be selected by adjusting the opening degree of the pressure control
valve 302a whose output pressure becomes relatively lower while
keeping the pressure control valve 300a whose output pressure
becomes relatively higher fully opened. With such pressure ratio
control, it is possible to arbitrarily control a ratio of a flow
rate of the mixed dilution gas of CO/O.sub.2/Ar supplied to the
first shower head 66a to that of the mixed dilution gas of
CO/O.sub.2/Ar supplied to the third shower head 208a.
[0134] Monitored pressure signals respectively outputted from the
pressure sensors 300b and 302b of the PCVs 300 and 302 are
transmitted to a maintenance control unit 304 via the gas control
unit 106. The maintenance control unit 304 includes a microcomputer
and performs a maintenance process to be described later based on
the monitored pressures (pressure measurement values) from the
pressure sensors 300b and 302b.
[0135] In accordance with this example, in case preset values of
the flow rates (gas distribution amounts) of the dilution gas to be
distributed respectively to the first and the third shower head 66a
and 208a are changed, the gas control unit 106 can control both or
either one of the pressure control valves 300a and 302a in response
to a command from a main control unit such that the gas flow rate
can be instantly changed. Accordingly, it is possible to adjust a
balance of the gas flow rate ratio between the Ar flow [1]
discharged (introduced) through the first shower head 66a into the
chamber 10 and the Ar flow [3] discharged (introduced) through the
third shower head 208a into the chamber 10 with high accuracy
during the etching process. By improving such function of adjusting
a flow rate balance, it is possible to improve etching
characteristics such as a uniformity of an in-surface etching shape
of the semiconductor wafer W or the like. Moreover, a flow rate
ratio controlling method employing the aforementioned pressure
control unit is not limited to the gas distribution to the first
and the third shower head 66a and 208a, and may be applied to an
arbitrary application for performing the same gas distribution.
[0136] As described above, the processing gas flow rate control
system of FIG. 12 can respond more rapidly to a change of a gas
flow rate compared to the processing gas flow rate control system
described in FIG. 10. However, it has a drawback in which the
accuracy of a gas distribution amount is easily affected by a
conductance change of a gas channel at a downstream of the pressure
control units (the PCVs 300 and 302). In such case, a monitoring
and a maintenance of the pressure control unit become
significant.
[0137] Hereinafter, a desired maintenance work for the pressure
control unit in this embodiment will be described. The maintenance
work is mainly performed by a maintenance processing unit 304 and
includes `gas pressure span deviation (error) check`, `gas pressure
stability check` and a determination process thereof.
[0138] (Gas Pressure Span Deviation Check)
[0139] For instance, during a process for purging an inner space of
the chamber 10 with N.sub.2 gas, the respective pressure control
valves 300a and 302a of the first and the second PCV 300 and 302
are fully opened, as described above. Further, the N.sub.2 gas is
supplied at a predetermined flow rate from an N.sub.2 gas supply
source (not shown) to the gas supply line 94 while keeping an
exhaust rate of the inside of the chamber 10 constant. Accordingly,
as illustrated in FIG. 13A, monitored pressures P.sub.C and P.sub.E
(pressure measurement values) obtained from the pressure sensors
300b and 302b of the PCVs 300 and 302 start to increase
exponentially when the N2 gas supply begins to reach at stable
constant pressures [P.sub.C] and [P.sub.E]. In general, since the
first shower head 66a has a smaller number of gas injection
openings (a smaller gas channel conductance) than the third shower
head 208a, the pressure [P.sub.C] of the first PCV 300 becomes
higher than the pressure [P.sub.E] of the second PCV 302. In a
normal state, the gas pressure difference, i.e.,
A=[P.sub.C]-[P.sub.E], falls within a predetermined span.
[0140] The maintenance processing unit 304 obtains the monitored
pressures (pressure measurement values) P.sub.C and P.sub.E from
the pressure sensors 300b and 302b and then calculates the gas
pressure difference, i.e., A=[P.sub.C]-[P.sub.E], at
100-millisecond intervals, to thereby monitor the pressures. The
pressure monitoring is carried out for a predetermined time period
t.sub.1 after the start of the purging process until the pressure
becomes stabilized, e.g., until the purging process is completed.
To be specific, it is checked whether or not the gas pressure
difference A falls within a preset tolerance range (lower limit
A.sub.L-upper limit A.sub.H). Then, if it deviates from the
tolerance range (lower limit A.sub.L-upper limit A.sub.H) for a
specified time, e.g., for three seconds (thirty times of sampling
consecutively performed at 100-millisecond intervals), it is
determined as `abnormality` and, then, an alarm is displayed.
Herein, the `abnormality` indicates that a relative balance between
a gas distribution system of the PCV 300 or the first shower head
66a and that of the PCV 302 or the second shower head 68a is lost,
which generally occurs when either one of the gas systems is
broken.
[0141] As described above, when the alarm of `abnormality` is
displayed, a next semiconductor wafer W is prohibited from being
loaded into the chamber 10 of the plasma etching apparatus by the
interlock to perform a required maintenance work.
[0142] (Gas Pressure Stability Check)
[0143] `Gas pressure stability check` is carried out during a
regular maintenance. In this examination as well, N.sub.2 gas is
supplied at a predetermined flow rate from an N.sub.2 gas supply
source (not shown) to the gas supply line 94 while keeping an
exhaust rate of the inside of the chamber 10 constant. However, the
N.sub.2 gas is provided to not both of the gas distribution systems
but only one of the gas distribution systems. That is, either one
of the pressure control valves 300a and 302a of the PCVs 300 and
302 is tightly closed, whereas the other is fully opened.
[0144] To be more specific, an opening/closing state of the
pressure control valves 300a and 302a is converted into two steps.
In the first step, the pressure control valve 300a of the PCV 300
is tightly closed, whereas the pressure control valve 302a of the
PCV 302 is fully opened. At this time, it is preferable to tightly
close only the pressure control valve 300a after both of the
pressure control valves 300a and 302a are fully opened first. On
the contrary, in the second step, the pressure control valve 302a
of the PCV 302 is tightly closed, whereas the pressure control
valve 300a of the PCV 300 is fully opened. Further, in each step,
monitored pressures (pressure measurement values) obtained from the
pressure sensors 300b and 302b of the PCVs 300 and 302 are
acquired.
[0145] FIGS. 14A and 14B provide waveforms of time characteristics
of the monitored pressures (the pressure measurement values)
obtained from the pressure sensors 300b and 302b while setting
N.sub.2 gas flow rates L.sub.1 and L.sub.2 respectively at 600 sccm
and 1000 sccm, for example, in the examination of the `gas pressure
stability check`. As illustrated, in the first step, a considerably
higher pressure P.sub.EL can be obtained from the fully opened PCV
302 than in an ordinary operation, whereas a considerably lower
pressure P.sub.CO can be obtained from the fully closed PCV 300
than in the ordinary operation. Moreover, in the second step, a
considerably higher pressure P.sub.CL can be obtained from the
fully opened PCV 300 than in the ordinary operation, whereas a
considerably lower pressure P.sub.EO can be obtained from the fully
closed PCV 302 than in the ordinary operation.
[0146] In the first step, the maintenance processing unit 304
calculates an average of the monitored pressures P.sub.EL and
P.sub.CO, which are sampled at regular intervals (e.g., at
one-second intervals) for a specified period (e.g., nine seconds)
from a specific time t.sub.2 when the gas pressure becomes
stabilized. Thereafter, in the second step, the maintenance
processing unit 304 calculates an average of the monitored
pressures P.sub.CL and P.sub.CO, which are sampled at regular
intervals for a specified period from a specific time t.sub.3 when
the gas pressure becomes stabilized.
[0147] Next, the maintenance processing unit 304 performs a
determination process for several examination items based on the
monitored pressure data obtained from a plurality of, e.g., two
examinations where the N.sub.2 gas flow rate is set as a
parameter.
[0148] A first examination item is span characteristics of a
responsiveness of a pressure to a gas flow rate. As shown in FIG.
15A, in the gas distribution system of the first PCV 300 or the
first shower head 66a, an increasing rate or an inclination
G.sub.PC between a pressure P.sub.CL1 of a fully opened pressure
valve obtained from a first (N.sub.2 gas flow rate L.sub.1)
examination and a pressure P.sub.CL2 of a fully opened pressure
valve obtained from a second (N.sub.2 gas flow rate L.sub.2)
examination is calculated by using a first order linear approximate
equation (P.sub.CL2-P.sub.CL1)/(L.sub.2-L.sub.1). Further, it is
checked whether the inclination G.sub.PC falls within a preset
tolerance range (lower limit G.sub.L-upper limit G.sub.H). In the
same manner, as illustrated in FIG. 15B, in the gas distribution
system of the second PCV 302 or the third shower head 208a, an
increasing rate or an inclination H.sub.PE between a pressure
P.sub.EL1 of a fully opened pressure valve obtained from the first
(N.sub.2 gas flow rate L.sub.1) examination and a pressure
P.sub.EL2 of a fully opened pressure valve obtained from the second
(N.sub.2 gas flow rate L.sub.2) examination is calculated by using
a first order linear approximate equation
(P.sub.EL2-P.sub.EL1)/(L.sub.2-L.sub.1). Furthermore, it is checked
whether the inclination G.sub.PC falls within a preset tolerance
range (lower limit H.sub.L-upper limit H.sub.H). As a cause of the
deviation from the tolerance range, there may be considered a
breakdown of a pressure control valve or a pressure sensor in the
corresponding PCV or the like. Since the distribution control
cannot be performed as it is planned, it is preferable to display
an alarm instructing an inspection or a component replacement.
[0149] A second examination item is a CEL abrasion, i.e., an
abrasion (deterioration) of the gas injection openings in the
shower head. In the plasma etching apparatus, the shower head
serving as an upper electrode is abraded and deteriorated by ion
bombardments. Especially, an electric field is concentrated around
the gas injection openings, resulting in an easy sputtering
thereof. If the gas injection openings are abraded, the conductance
thereof decreases, thereby lowering a pressure in the corresponding
gas distribution system.
[0150] In order to determine an abrasion state (CEL abrasion in the
center) of the gas injection openings in the first shower head 66a
in the gas distribution system of the first PCV 300 or the first
shower head 66a, it is checked whether or not the pressure
P.sub.CL2 of the fully opened pressure valve obtained under a
predetermined N.sub.2 gas flow rate (e.g., L.sub.2) falls within a
preset tolerance range (lower limit K.sub.L-upper limit K.sub.H),
as illustrated in FIG. 14B. If it falls within the tolerance range
(lower limit K.sub.L-upper limit K.sub.H), it is determined to be
within a specification (normality). If otherwise, it is determined
to be out of the specification (abnormality).
[0151] In the same manner, in order to determine an abrasion state
(CEL abrasion in an edge) of the gas injection openings of the
third shower head 208a in the gas distribution system of the first
PCV 300 or the first shower head 66a, it is checked whether or not
the pressure P.sub.CE2 of the fully opened pressure valve obtained
under a predetermined N.sub.2 gas flow rate (e.g., L.sub.2) falls
within a preset tolerance range (lower limit J.sub.L to upper limit
J.sub.H), as illustrated in FIG. 14B. If it falls within the
tolerance range (lower limit J.sub.L-upper limit J.sub.H), it is
determined to be within a specification (normality). If otherwise,
it is determined to be out of the specification (abnormality).
[0152] A third examination item is a gas leak in the gas
distribution system. In the `gas pressure stability check`, as
illustrated in FIGS. 14A and 14B, pressures P.sub.CO and P.sub.EO
due to the gas leak can be detected even in the gas distribution
system whose pressure control valves are tightly closed. Such gas
leak includes a leak flowing back from the outside via the inside
of the chamber 10 as well as a leak in the gas distribution system
(especially, the annular partition members 64 and 264 in the shower
heads). For example, in the first step, nitrogen gas distributed
from the fully opened third shower head 208a into the chamber 10
flows into the gas distribution system through the gas injection
openings of the first shower head 66a on the close side. A large
amount of gas leak is not desirable.
[0153] Accordingly, as described above, it is checked whether or
not the monitored pressures P.sub.CO and P.sub.EO obtained from the
closed gas distribution system are higher than an allowable value
M. If the monitored pressures P.sub.CO and P.sub.EO are lower than
the allowable value M, it is determined to be normal, which
indicates that the gas leak does not exceed the allowable amount.
On the other hand, if the monitored pressures P.sub.CO and P.sub.EO
are higher than the allowable value M, it is determined to be
abnormal, which indicates that the gas leak exceeds the allowable
amount.
[0154] Various reference values and tolerance ranges used in the
aforementioned maintenance process can be changed at any time
depending on a difference between apparatuses, a period of use, a
processing gas or the like of the corresponding apparatus.
Moreover, it is preferable to check a zero point of the pressure
sensor of the pressure control unit by using a separate inspection
unit.
[0155] Hereinafter, a cooling mechanism for the shower head also
serving as an electrode in this embodiment will be described with
reference to FIGS. 16 to 18. In a capacitively coupled plasma
etching apparatus for generating a high-density plasma, it is very
critical to control parallel plate electrodes at a specified
temperature by reducing a temperature increase of the electrode,
wherein the temperature thereof may be easily increased due to a
radio frequency power applied to the electrodes.
[0156] FIG. 16 represents an installation position of a coolant
passageway 138 provided in the upper electrode 34 (the outer upper
electrode 36 and the inner upper electrode 38) in the plasma
etching apparatus of this embodiment. FIG. 17 provides a pattern of
a coolant path in the coolant passageway 138. FIG. 18 depicts a
cross-sectional structure of the coolant passageway 138, which is
taken along line X.sub.2-X.sub.2 of FIG. 17.
[0157] A coolant maintained at a specific temperature, e.g., a
cooling water, is supplied and circulated from a chiller unit (not
shown) provided at an outside into the coolant passageway 138
through a line. As shown in FIG. 17, the coolant supplied from the
chiller unit via a line (not shown) flows through an inner entrance
140 into the coolant passageway 138. Next, the coolant goes around
a central portion and then flows along a first coolant passageway
148a in an arrow direction. After the coolant goes around
approximately concentrically along the first coolant passageway
148a, it flows along a second coolant passageway 148b in a
direction opposite to that of the flow in the first coolant
passageway 148a. Then, the coolant flows along a third coolant
passageway 148c in a direction opposite to that of the flow in the
second coolant passageway 148b and then goes through an inner
outlet 142. Herein, the inner outlet 142 and an outer entrance 144
are connected to each other by a line (not illustrated), and the
coolant flowing from the inner outlet 142 to the outer entrance 144
flows along a fourth coolant passageway 148d in a direction
opposite to that of the flow in the third coolant passageway 148c.
Since the directions of the coolant flows in the adjacent coolant
passageways are opposite to each other, a temperature nonuniformity
in the outer and the inner upper electrode 36 and 38 can be
considerably reduced.
[0158] FIGS. 18A and 18B show two favorable cross-sectional shapes
of the coolant passageway 148. In other words, FIG. 18A provides a
comb-shaped cross section of the coolant passageway, and FIG. 18B
describes a serpentine cross section of the coolant passageway.
With such comb-shaped or serpentine cross sectional structure of
the passageway, an area of a sidewall of the coolant passageway
increases. Accordingly, a contact area between the coolant and the
coolant passageway increases, thereby improving a heat absorption
efficiency of the coolant. Further, in any of the cases, the cross
sectional area of the coolant passageway 138 has a similar size to
that of the aforementioned outer line. Since the coolant passageway
has such large cross sectional area, it is possible to suppress a
pressure loss and prevent a flow velocity of the coolant from being
deteriorated. In fact, whereas a conventional temperature
difference between the coolant and the outer and the inner upper
electrode 36 and 38 is 20.degree. C., in this embodiment, the
temperature difference is reduced to 2.degree. C.
[0159] With such cooling unit for the shower head also serving as
the electrode, it is possible to perform a highly precise
temperature control of the upper electrode which generates a
high-density plasma by a radio frequency power applied thereto.
Thus, an adhesion of reaction products onto the electrode 60 shown
in FIG. 16 is reduced, thereby considerably reducing the clogging
of the gas injection openings 60a. As a result, the maintenance of
the plasma etching apparatus becomes simple.
[0160] The following is a description on a gas line for introducing
a processing gas into the central gas introduction chamber 66 or
the peripheral gas introduction chamber 68 of the shower head also
serving as the electrode. In this embodiment, all of the gas supply
lines including the gas supply line 90, the branch line 94a and the
like in the chamber 10 are made of an insulating material. This is
because if the gas supply line is formed of a conductive material
such as SUS, a radio frequency transmission in the chamber becomes
disturbed, thereby significantly affecting the etching
characteristics.
[0161] FIG. 19 illustrates an enlarged view of an area 150 of FIG.
1. As shown in FIG. 19, a leading end portion of the gas supply
line 90, which is made of Teflon (registered mark), is provided
with a protruded portion 152, and a top surface of the electrode
support 62 is provided with a recess portion corresponding to the
protruded portion 152. Since the protruded portion 152 is fitted in
the recess portion without forming any substantial space or gap
therebetween, the gas supply line 90 is airtightly attached to the
electrode support 62 via an O-ring 154 and a center ring 156.
Herein, the processing gas is supplied into the peripheral gas
introduction chamber 68 through a gas channel 158 of the gas supply
line. Likewise, if a joint portion of the gas supply line 90
connected to the shower head of the upper electrode 34 is blocked
by an insulating material such as Teflon (registered trade mark)
without forming a gap, it is possible to actually prevent an
abnormal discharge in a processing gas introduction line.
[0162] Hereinafter, a safety function of the plasma etching
apparatus of this embodiment, especially, an electromagnetic wave
leakage preventing function, i.e., an electro-magnetic interference
(EMI) shielding function, will be described with reference to FIGS.
1 and 20 to 22.
[0163] As described in FIGS. 20A and 20B, the chamber 10 is divided
into a lower chamber assembly 162 and an upper chamber assembly 164
by line X.sub.1-X.sub.1 depicted in FIG. 1. FIG. 20A is a side view
of principal parts, showing opposite portions of the separated
assemblies 162 and 164, and FIG. 20B provides a cross-sectional
view thereof.
[0164] As depicted in FIG. 20A, a lower claw 168 is fixedly
attached to a predetermined specific location of a cylindrical
joint member 166 of the lower chamber assembly 162, and an upper
claw 172 is provide at a predetermined specific location of a
cylindrical joint member 170 of the upper chamber assembly 164.
Herein, the upper claw 172 is circumferentially movable within a
predetermined range with the help of a bearing mechanism to be
described later. Further, a plurality pairs of the upper and the
lower claws 172 and 168 facing each other are disposed at regular
intervals along a circumference of the chamber.
[0165] As illustrated in FIG. 20B, a shield groove 174 is formed in
a top surface of the cylindrical lower joint member 166 such that
it extends along the top surface portion, and an annular EMI shield
spiral 176 is inserted in the shield groove 174. Further, an
insulating member 178 is provided adjacently to an inner side of
the lower joint member 166 along its radial direction. In the
meantime, a bearing support 180 is fixed on an outer wall of the
cylindrical upper joint member 170, and a bearing drive 182 is
mounted on the bearing support 180 via the bearing mechanism 184
such that it can move in a circumferential direction. Moreover, the
insulating member 186 is provided adjacently to an inner side of
the upper joint member 170 along its radial direction. The upper
and the lower insulating member 186 and 178 form the insulating
shielding member 44 shown in FIG. 1.
[0166] FIGS. 21A and 21B present a state where the lower chamber
assembly 162 and the upper chamber assembly 164 are coupled to each
other along the line X.sub.1-X.sub.1 shown in FIG. 1. FIG. 21A is a
side view of principal parts of the coupled chamber joint portion,
and FIG. 20B provides a cross-sectional view thereof.
[0167] As depicted in FIG. 21A, the upper claw 172 of the upper
chamber assembly 164 is engaged with the lower claw 168 of the
lower chamber assembly 162 wherein a top surface 172a is in contact
with a bottom surface 168a. After the top surface of the lower
joint portion 166 makes a contact with the bottom surface of the
upper joint portion 170, the bearing mechanism 184 moves or
displaces the upper claw 172 by a predetermined distance in a
circumferential direction with the help of a driving and movement
converting mechanism (not shown) such as a pinion and rack, thereby
achieving the engagement between the upper and the lower claw 172
and 168.
[0168] In the coupled state of this embodiment, as shown in FIG.
21B, the lower joint member 166 is electrically connected to the
upper joint member 170 by the EMI shield spiral 176, thereby
preventing a radio frequency inputted in this apparatus from being
leaked out of the chamber 10. Moreover, the lower and the upper
joint member 166 and 170 make an airtight contact via a well-known
airtight sealing member (not shown) such as an O-ring. Furthermore,
the airtight sealing member such as the O-ring may be provided on
the inner side of the EMI shield spiral 176.
[0169] A mechanism for preventing an electromagnetic wave leakage
or a noise generation is provided at desired places in addition to
the above-described place in the plasma etching apparatus of this
embodiment. At all places, as can be seen from the enlarged view of
the FIG. 22, the EMI shield spiral 176 made of, e.g., stainless
steel, is inserted in a spiral attachment groove provided in a top
surface of a cylindrical lower joint member (e.g., the lower joint
member 166) and, further, an upper joint member (e.g., the upper
joint member 170) is detachably connected thereto from above such
that it pushes the EMI shield spiral 176 thereabove.
[0170] In this embodiment, as shown in FIG. 23, the EMI shield
spiral 176 is formed as a ring body having a required diameter or
length, and the ring-shaped EMI shield spiral 76 is inserted into
the spiral groove. With such ring-shaped EMI shield spiral, the
stability and safety in an assembly or a maintenance of the plasma
etching apparatus can be considerably enhanced. Conventionally, the
EMI shield spiral is cut into a required length, and the linear EMI
shield spiral is inserted into the spiral attachment groove.
However, in case of the linear EMI shield spiral, if both ends
thereof are not perfectly met to each other in the inserted state,
the electromagnetic wave leakage preventing function becomes poor
or the insertion operation becomes difficult. Further, the linear
EMI shield spiral can be formed as the ring-shaped EMI shield
spiral by welding both ends thereof to be connected.
[0171] Although the preferred embodiments of the present invention
have been described, the present invention is not limited to those
preferred embodiments. It will be understood by those skilled in
the art that various changes and modifications may be made without
departing from the spirit and scope of the invention.
[0172] For example, in the first embodiment, there is provided the
triple shower head system including the upper central shower head
66a, the upper peripheral shower head 68a and the side shower head
108, wherein the upper central shower head 66a and the upper
peripheral shower head 68a form the upper shower head provided at
the upper electrode 34 (the inner upper electrode 38), and the side
shower head 108 is provided on the sidewall of the chamber 10.
However, it is possible to provide a dual shower head system
including the upper shower head (66a and 68a) and the side shower
head 108, wherein the upper shower head is a single system obtained
by omitting the annular partition member 64, for example. In such
case, it is preferable to introduce an etchant gas through the
upper shower head (66a and 68a) and a dilution gas through the side
shower head 108. Further, in the side gas inlet, a processing gas
can be introduced through a gas pipe instead of the shower head 108
of this embodiment.
[0173] In the first preferred embodiment, an additive gas such as
O.sub.2 gas or CO gas is introduced together with a dilution gas
(especially, an inert gas such as Ar) through the side shower head
108 or the upper central shower head 66a into the chamber 10.
However, the additive gas may be introduced together with an
etchant gas through the upper central shower head 66a into the
chamber 10. Further, the additive gas may be introduced into the
chamber 10 after being distributed based on the classification by
gas species or at a desired flow rate ratio between the shower
heads 108 and 66a for the dilution gas and the shower head 68a for
the etchant or between the shower heads 108 and 68a for the
dilution gas. Furthermore, it is also possible to add a
predetermined amount of etchant gas to the gas introduced through
the shower heads 108 and 66a for the dilution gas or a
predetermined amount of dilution gas (especially, an inert gas) to
the gas introduced through the shower head 68a of the etchant.
[0174] In the second preferred embodiment, an additive gas such as
O.sub.2 gas or CO gas is introduced together with a dilution gas
(especially, an inert gas such as Ar) through the third shower head
208a or the first upper shower head 66a into the chamber 10.
However, the additive gas may be introduced together with an
etchant gas through the second upper shower head 68a into the
chamber 10. Further, the additive gas may be introduced into the
chamber 10 after being distributed based on the classification by
gas species or at a desired flow rate ratio between the shower
heads 208a and 66a for the dilution gas and the shower head 68a for
the etchant or between the shower heads 208a and 68a for the
dilution gas. Furthermore, it is also possible to add a
predetermined amount of etchant gas to the gas introduced through
the shower heads 208a and 66a for the dilution gas or a
predetermined amount of dilution gas (especially, an inert gas) to
the gas introduced through the shower head 68a for the etchant.
[0175] Although, in the aforementioned embodiment, there has been
described a case where gases are distributed to two gas supply
lines for a flow rate ratio control, the gases may be distributed
to three or more gas supply lines. For example, in case a mass flow
control unit is included as the pressure control unit described in
FIG. 12, the gas supply lines may be branched by providing in
parallel three or more PCVs corresponding to the number of the gas
supply lines. Further, when the maintenance check of the flow rate
ratio control unit is performed by using three or more PCVs, two
PCVs are selected and, then, the check and the determination
described above with reference to FIGS. 13 to 15 can be carried
out. At this time, it is preferable to check and determine for
every combination of two PCVs. Moreover, a method and an apparatus
for performing a maintenance of the PCVs of the aforementioned
embodiment may also be applied to any processing apparatuses other
than the plasma etching apparatus.
[0176] The plasma etching apparatus of the present invention may
arbitrarily employ an etchant gas, a dilution gas and an additive
gas depending on processes. For instance, an organic compound gas
containing halogen may contain chlorine Cl, bromine Br or iodine I
without being limited to fluorine F.
[0177] Although the single annular outer upper electrode 36 forming
the upper electrode 34 is provided in the aforementioned
embodiment, two or more outer upper electrodes 36 spaced from each
other at regular intervals may be provided around a peripheral
portion of the inner upper electrode 38. The upper electrode 34 may
be formed in either one part or separate parts.
[0178] Further, although a substrate to be processed is a
semiconductor wafer in the aforementioned embodiment, the substrate
to be plasma-processed may also be a glass substrate for use in a
flat display panel such as an LCD glass substrate and a PDP
substrate.
[0179] Although the plasma etching apparatus has been described in
the aforementioned embodiment, the present invention may be applied
to a plasma CVD apparatus for forming an insulating film, a
conductive film, a semiconductor film or the like and an apparatus
for plasma cleaning of an insulating substrate surface, a chamber
inner wall or the like.
[0180] While the invention has been shown and described with
respect to the preferred embodiments, it will be understood by
those skilled in the art that various changes and modification may
be made without departing from the spirit and scope of the
invention as defined in the following claims.
* * * * *