U.S. patent application number 10/933422 was filed with the patent office on 2005-05-05 for plasma processing apparatus and method and apparatus for measuring dc potential.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Hayami, Toshihiro, Maebashi, Satoshi, Umehara, Naoyuki.
Application Number | 20050095732 10/933422 |
Document ID | / |
Family ID | 34556992 |
Filed Date | 2005-05-05 |
United States Patent
Application |
20050095732 |
Kind Code |
A1 |
Maebashi, Satoshi ; et
al. |
May 5, 2005 |
Plasma processing apparatus and method and apparatus for measuring
DC potential
Abstract
In a plasma processing apparatus, a member for propagating high
frequency from a high frequency power supply and/or to which the
high frequency is applied. A power feed rod is electromagnetically
shielded between a matching unit and a bottom plate of a chamber by
a coaxial cylindrical conductor connected to a ground potential. A
surface potential system disposed in an appropriate distance from
the power feed rod in radius direction is installed in the
cylindrical conductor, and measures in a non-contact state the
electrostatic surface potential of the power feed rod through
electrostatic capacitance and provides a controller with a surface
potential detection signal including surface potential measurement
value information. The controller performs a required signal
processing or operation processing on the basis of the surface
potential detection signal from the surface potential system,
thereby obtaining the measurement value of the DC potential on the
power feed rod.
Inventors: |
Maebashi, Satoshi;
(Nirasaki-shi, JP) ; Hayami, Toshihiro;
(Nirasaki-shi, JP) ; Umehara, Naoyuki;
(Nirasaki-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
34556992 |
Appl. No.: |
10/933422 |
Filed: |
September 3, 2004 |
Current U.S.
Class: |
438/17 ; 118/712;
118/723E |
Current CPC
Class: |
H01J 37/32174 20130101;
H01J 37/32935 20130101; H01J 37/32082 20130101 |
Class at
Publication: |
438/017 ;
118/723.00E; 118/712 |
International
Class: |
H01L 021/66 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 3, 2003 |
JP |
2003-311144 |
Sep 25, 2003 |
JP |
2003-333758 |
Aug 6, 2004 |
JP |
2004-231445 |
Claims
What is claimed is:
1. A DC voltage measuring method, for use with a plasma processing
apparatus in which a high frequency voltage from a high frequency
power supply is applied to a high frequency electrode provided in a
processing vessel through a high frequency feeding conductor, for
measuring a DC potential of the high frequency electrode or the
high frequency feeding conductor, wherein a measurement value of
the DC potential is obtained by non-contactly measuring an
electrostatic surface potential of the high frequency electrode or
the high frequency feeding conductor by using electrostatic
capacitance.
2. A DC voltage measuring apparatus, for use with a plasma
processing apparatus in which a high frequency voltage from a high
frequency power supply is applied to a high frequency electrode
provided in a processing vessel through a high frequency feeding
conductor, for measuring a DC potential of the high frequency
electrode or the high frequency feeding conductor, the DC voltage
measuring apparatus comprising: a unit for obtaining a measurement
value of the DC potential by non-contactly measuring an
electrostatic surface potential of the high frequency electrode or
the high frequency feeding conductor by using electrostatic
capacitance.
3. A plasma processing apparatus comprising: a processing vessel
for providing a depressurized space for performing a plasma
processing on a substrate to be processed; a first electrode
disposed in the processing vessel; a processing gas supply unit for
supplying a processing gas into the processing vessel; a high
frequency power supply for generating a high frequency voltage for
forming a plasma; a high frequency feeding conductor connected to
the first electrode for supplying the high frequency voltage from
the high frequency power supply to the first electrode; and a DC
potential measurement unit for non-contactly measuring an
electrostatic surface potential of the first electrode or the high
frequency feeding conductor by using electrostatic capacitance to
obtain the DC potential.
4. The plasma processing apparatus of claim 3, comprising a second
electrode disposed to face the first electrode in parallel in the
processing vessel.
5. The plasma processing apparatus of claim 4, wherein the
substrate to be processed is disposed on the first electrode, and
vent-holes for discharging the processing gas toward the first
electrode are provided in the second electrode.
6. The plasma processing apparatus of claim 3, comprising: a
matching unit for performing an impedance matching between the high
frequency power supply side and a load side, the matching unit
having an input terminal electrically coupled to the high frequency
power supply and an output terminal electrically coupled to the
high frequency feeding conductor.
7. The plasma processing apparatus of claim 6, wherein the matching
unit is installed outside the processing vessel, and the high
frequency feeding conductor between the matching unit and the
processing vessel is surrounded with a cylindrical conductor
connected to a ground potential.
8. The plasma processing apparatus of claim 7, wherein the
cylindrical conductor includes a first cylindrical conductor
portion whose one end is coupled to the processing vessel; a second
cylindrical conductor portion whose one end is coupled to the
matching unit; and a first connecting part for attachably and
detachably connecting the other ends of the first and the second
cylindrical conductor portion with each other; and wherein a probe
of the DC potential measurement unit is installed in the first
connecting part.
9. The plasma processing apparatus of claim 8, wherein the high
frequency feeding conductor includes a first bar-type conductor
whose one end is fixed to a rear surface of the first electrode; a
second bar-type conductor whose one end is fixed to the output
terminal of the matching unit; and a second connecting part for
attachably and detachably connecting the other ends of the first
and the second bar-type conductor with each other; and wherein the
second connecting part is disposed in a position corresponding to
the first connecting part.
10. An electrical joint member provided between conductive members
joined with each other in a processing apparatus in order to reduce
an electrical resistance between the conductive members,
comprising: an elastic body; and a surface metal layer of aluminum
formed on a surface of the elastic body.
11. The electrical joint member of claim 10, wherein the elastic
body is formed of an organic compound material.
12. The electrical joint member of claim 10, wherein the surface
metal layer is formed on the surface of the elastic body by
evaporation or CVD.
13. The electrical joint member of claim 10, wherein a thickness of
the surface metal layer is equal to or less than 100 .mu.m.
14. The electrical joint member of claim 10, wherein a high
frequency flows between the conductive members joined with each
other.
15. A plasma processing apparatus constituted by assembling a
plurality of conductive members and performing a predetermined
processing on a substrate to be processed by a plasma of a
processing gas, the processing gas being converted into the plasma
by using a high frequency, wherein the electrical joint member
described in claim 10 is provided between the conductive members
joined with each other.
16. The electrical joint member of claim 10, wherein the elastic
body is a spiral made of a metal material.
17. The electrical joint member of claim 16, wherein the metal
material constituting the elastic body is titanium, a stainless
steel or a copper alloy.
18. An electrical joint member provided between conductive members
joined with each other in a processing apparatus in order to reduce
an electrical resistance between the conductive members,
comprising: an elastic body made of a first metal material; and a
surface metal layer made of a second metal material and formed on a
surface of the elastic body, the second metal material having a
resistivity smaller than that of the first metal material and
causing no negative effects on a process.
19. The electrical, joint member of claim 18, wherein the elastic
body is a spiral.
20. The electrical joint member of claim 18, wherein the first
metal material is titanium, a stainless steel or a copper
alloy.
21. The electrical joint member of claim 18, wherein the second
metal material is aluminum.
22. The electrical joint member of claim 18, wherein the surface
metal layer is formed on the surface of the elastic body by
evaporation or CVD.
23. The electrical joint member of claim 18, wherein a thickness of
the surface metal layer is equal to or less than 100 .mu.m.
24. The electrical joint member of claim 18, wherein a high
frequency flows between the conductive members joined with each
other.
25. A plasma processing apparatus constituted by assembling a
plurality of conductive members and performing a predetermined
processing on a substrate to be processed by a plasma of a
processing gas, the processing gas being converted into the plasma
by using a high frequency, wherein the electrical joint member
described in claim 18 is provided between the conductive members
joined with each other.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a plasma processing
apparatus; and, more particularly, to a method and an apparatus for
measuring a DC potential of a member propagating or receiving a
high frequency from a high frequency power supply.
BACKGROUND OF THE INVENTION
[0002] Generally, in a parallel plate type plasma processing
apparatus, a negative DC potential V.sub.dc is generated in an
electrode or a high frequency electrode to which a high frequency
(RF) for generating a plasma is applied. From this, in a parallel
plate type plasma etching apparatus, a high frequency is
conventionally applied to a lower electrode or a susceptor on which
a substrate to be processed is mounted, in order for ions in a
plasma to be vertically drawn onto a surface of the substrate with
the force of an electric field by a negative DC potential V.sub.dc
on the surface of the susceptor, thereby performing anisotropic
etching or reactive ion etching (RIE). Further, such a DC potential
V.sub.dc on the high frequency electrode has a correlation with an
etching condition, a high frequency discharge state in a processing
vessel or the like. For example, if a gas pressure in the
processing vessel is lowered, the absolute value of the DC
potential V.sub.dc becomes higher. Moreover, if an extraordinary
condition occurs in a high frequency discharge system by, e.g.,
deterioration as a result of the elapse of time, it is reflected in
the DC potential V.sub.dc (generally, the absolute value of
V.sub.dc is increased). Thus, the DC potential V.sub.dc has been
measured to represent a process parameter indicating a variation of
plasma processing conditions or a maintenance parameter indicating
a repair or replacement timing of a high frequency component or a
member.
[0003] Conventionally, a voltage sense line is connected to a high
frequency electrode or a power feed rod directly coupled therewith,
and a DC potential V.sub.dc detected by the voltage sense line is
entered as an analog DC voltage to a voltage measurement circuit,
thereby obtaining a measurement value of the DC potential
V.sub.dc.
[0004] In a latest plasma processing apparatus, the power of a high
frequency used tends to be increased in order to enhance the
efficiency or miniaturization of a plasma processing; and
accordingly, a peak-to-peak value of a high frequency voltage being
propagated through the power feed rod or the high frequency
electrode is increased. For this reason, in a conventional
measurement method for introducing a DC potential V.sub.dc into a
voltage measurement circuit by putting a voltage sense line in
contact with the high frequency electrode or the power feed rod, a
high frequency that originally has to be supplied to a high
frequency electrode runs off to the ground from a place in which a
voltage measurement unit is installed (being leaked or discharged)
through a measurement circuit in the unit or a unit housing.
Therefore, the measurement unit itself may be damaged or cause to
be damaged, and there are problems that could have negative impact
on a high frequency discharge in a processing vessel and a
characteristic of a plasma generation and, further, a plasma
processing quality.
SUMMARY OF THE INVENTION
[0005] The present invention was conceived taking into
consideration the problems of the conventional technology. It is,
therefore, an object of the present invention to provide a DC
potential measuring method, a DC potential measuring apparatus and
a plasma processing, apparatus capable of safely and accurately
measuring a DC potential of a member propagating or receiving a
high frequency from a high frequency power supply.
[0006] In order to achieve the object described above, in
accordance with the present invention, there is a DC voltage
measuring method, for use with a plasma processing apparatus in
which a high frequency voltage from a high frequency power supply
is applied to a high frequency electrode provided in a processing
vessel through a high frequency feeding conductor, for measuring a
DC potential of the high frequency electrode or the high frequency
feeding conductor, wherein a measurement value of the DC potential
is obtained by non-contactly measuring an electrostatic surface
potential of the high frequency electrode or the high frequency
feeding conductor by using electrostatic capacitance.
[0007] Further, in accordance with the present invention, there is
provided a DC voltage measuring apparatus, for use with a plasma
processing apparatus in which a high frequency voltage from a high
frequency power supply is applied to a high frequency electrode
provided in a processing vessel through a high frequency feeding
conductor, for measuring a DC potential of the high frequency
electrode or the high frequency feeding conductor, the DC voltage
measuring apparatus including: a unit for obtaining a measurement
value of the DC potential by non-contactly measuring an
electrostatic surface potential of the high frequency electrode or
the high frequency feeding conductor by using electrostatic
capacitance.
[0008] Further, in accordance with the present invention, there is
provided a plasma processing apparatus including: a processing
vessel for providing a depressurized space for performing a plasma
processing on a substrate to be processed; a first electrode
disposed in the processing vessel; a processing gas supply unit for
supplying a processing gas into the processing vessel; a high
frequency power supply for generating a high frequency voltage for
forming a plasma; a high frequency feeding conductor connected to
the first electrode for supplying the high frequency voltage from
the high frequency power supply to the first electrode; and a DC
potential measurement unit for non-contactly measuring an
electrostatic surface potential of the first electrode or the high
frequency feeding conductor by using electrostatic capacitance to
obtain the DC potential.
[0009] In the present invention, a surface potential on a power
feed rod through which a high frequency voltage from a high
frequency power supply is propagated or an electrode (a high
frequency electrode) to which the corresponding high frequency
voltage is applied, is measured in a non-contact state through an
electrostatic capacitance without passing through a conductor,
thereby obtaining a measurement value of a DC potential from a
signal indicating a measurement value of the surface potential.
Because such a non-contact method is employed, even in case a high
frequency power is increased greatly, the problem of causing a
leakage or a discharge of a high frequency in a measurement point
does not exist while the measurement value of the DC potential can
be obtained safely and accurately without affecting the high
frequency discharge or plasma generation.
[0010] A typical example in accordance with the plasma processing
apparatus of the present invention has a configuration of disposing
a second electrode facing the first electrode in parallel in the
processing vessel. In such a parallel plate type apparatus, as a
typical example, a substrate to be processed is disposed on the
first electrode and vent-holes for discharging a processing gas
toward the first electrode are provided in the second
electrode.
[0011] Further, in case a matching unit for performing an impedance
matching between a high frequency power supply side and a load
side-is provided, a high frequency feeding conductor may be
connected to an output terminal of the matching unit. In this case,
preferably the matching unit may be installed in the outside of the
processing vessel, and a cylindrical conductor between the matching
unit and the processing vessel connected to a ground potential may
be configured to surround the high frequency feeding conductor.
[0012] Furthermore, the high frequency feeding conductor may be
preferably configured to include a first bar-type conductor whose
one end is fixed to a rear surface of the first electrode; a second
bar-type conductor whose one end is fixed to the output terminal of
the matching unit; and a first connecting part for attachably and
detachably connecting the other ends of the first and the second
bar-type conductor with each other. The cylindrical conductor may
also be preferably configured to include a first cylindrical
conductor portion whose one end is coupled to the processing
vessel; a second cylindrical conductor portion whose one end is
coupled to the matching unit; and a second connecting part for
attachably and detachably connecting the other ends of the first
and the second cylindrical conductor portion with each other at a
position corresponding to the first connecting part, wherein a
probe of a DC potential measurement portion is attachably and
detachably installed in the second connecting part. As configured
above, the probe of the DC potential measurement portion is
installed in the second connecting part detachably disposed
adjacent to the high frequency feeding conductor, so that the
measurement portion is simply adjusted and maintained, and this
configuration is easily employed in a conventional processing
apparatus.
[0013] In accordance with the present invention, by the
configurations and operations as described above, the DC potential
of the member for propagating or receiving a high frequency from
the high frequency power supply can be measured safely and
accurately in the plasma processing apparatus.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 provides a longitudinal sectional view showing a
configuration of a plasma processing apparatus in accordance with a
first preferred embodiment of the present invention;
[0015] FIG. 2 is a longitudinal sectional view showing a
configuration around a surface potential system in the plasma
processing apparatus of the preferred embodiment;
[0016] FIG. 3 describes an exploded perspective view illustrating a
configuration around the surface potential system in the plasma
processing apparatus;
[0017] FIG. 4 sets forth a plan view showing a configuration of a
cylindrical joint portion in the plasma processing apparatus;
[0018] FIG. 5 is a view showing a configuration of the surface
potential system in the plasma processing apparatus;
[0019] FIG. 6 is a longitudinal sectional view showing a
configuration of the plasma processing apparatus in accordance with
the first preferred embodiment of the present invention;
[0020] FIG. 7A is a perspective view illustrating an outline of an
electrical joint member in the first preferred embodiment of the
present invention;
[0021] FIG. 7B is a cross sectional view showing a cross section
structure of the electrical joint member;
[0022] FIG. 8 is an exploded perspective view showing an example of
a state of using the electrical joint member;
[0023] FIG. 9 is a cross sectional view showing an example of a
state of using the electrical joint member;
[0024] FIG. 10 is a cross sectional view showing another example of
a state of using the electrical joint member;
[0025] FIG. 11 is a general view showing an electrical joint member
in accordance with another preferred embodiment;
[0026] FIG. 12 is a general view showing an electrical joint member
in accordance with a still another preferred embodiment;
[0027] FIG. 13A is a perspective view showing an electrical joint
member in accordance with still another preferred embodiment;
[0028] FIG. 13B is a cross sectional view illustrating an inner
structure of the electrical joint member in FIG. 13A.
[0029] FIG. 14A is a perspective view showing a joint between
conductive members by being fastened with bolts and in-plane
pressures of a joint surface as an image;
[0030] FIG. 14B shows a cross sectional view showing the joint
between the conductive members by being fastened with the bolts and
the existing in-plane pressure of joint surfaces as an image;
[0031] FIG. 15 describes a characteristic view showing a
relationship between a compressed value and a stress in the
electrical joint member of the present invention and an electrical
joint member of a comparative example;
[0032] FIG. 16 illustrates a characteristic view showing a
relationship between the compressed value and a contact resistance
in the electrical joint member of the present invention and the
electrical joint member of the comparative example;
[0033] FIG. 17 provides a characteristic view showing a
relationship between the stress and the contact resistance in the
electrical joint member of the present invention and the electrical
joint member of the comparative example;
[0034] FIG. 18 offers a cross sectional view showing an
experimental mechanism used for investigating a state of heat
generation by a high frequency;
[0035] FIG. 19 is an explanatory view showing temperature-measured
positions in the experimental mechanism;
[0036] FIG. 20 is a characteristic view showing the temperatures of
the regions of respective conductive paths when a high frequency is
applied thereto by using the experimental mechanism; and
[0037] FIG. 21 is a characteristic view showing the temperatures of
the regions of the respective conductive paths when a high
frequency is applied thereto by using the experimental
mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] Preferred embodiments of the present invention will now be
described with reference to the accompanying drawings.
[0039] FIG. 1 shows a configuration of a plasma processing
apparatus in accordance with a first preferred embodiment of the
present invention. The plasma processing apparatus is configured as
an RIE type plasma etching apparatus and has a cylindrical chamber
(a processing vessel) 10 made of a metal such as aluminum,
stainless steel or the like. The chamber 10 is frame grounded.
[0040] Installed in the chamber 10 is a disk-shaped lower electrode
or susceptor 12 for mounting thereon, e.g., a semiconductor wafer W
as a substrate to be processed. The susceptor 12 made of, e.g.,
aluminum is supported by a cylindrical supporting portion 16
extended vertically upward from the bottom of the chamber 10
through an insulating cylindrical maintaining portion 14. Disposed
on the top surface of the cylindrical maintaining portion 14 is a
focus ring 18 made of, e.g., quartz, surrounding annularly the top
surface of the susceptor 12.
[0041] Formed between a sidewall of the chamber 10 and the
cylindrical supporting portion 16 is an annular gas exhaust line
20, and disposed in the entrance or the middle of the gas exhaust
line 20 is an annular baffle plate 22 while a gas exhaust port 24
is disposed in the bottom portion thereof. Coupled to the gas
exhaust port 24 is a gas exhaust unit 28 via a gas exhaust pipe 26.
The gas exhaust unit 28 having a vacuum pump can depressurize a
processing space in the chamber 10 to a predetermined vacuum level.
Installed in the sidewall of the chamber 10 is a gate valve 30 for
opening/closing a loading/unloading port of the semiconductor wafer
W.
[0042] Electrically coupled to the susceptor 12 is a high frequency
power supply 32 for generating a plasma and an RIE via a matching
unit 34 and a power feed rod 36. The high frequency power supply 32
supplies a high frequency voltage of a predetermined high
frequency, e.g., 60 MHz to the lower electrode, that is, the
susceptor 12. Installed in a ceiling portion of the chamber 10 is a
shower head 38 to be described later as an upper electrode of a
ground potential. Accordingly, the high frequency voltage from the
high frequency power supply 32 is applied between the susceptor 12
and the shower head 38.
[0043] Disposed in the top surface of the susceptor 12 is an
electrostatic chuck 40 for supporting the semiconductor wafer W by
an electrostatic adsorptive force. The electrostatic chuck 40
includes an electrode 40a made of a conductive film embedded
between a pair of insulating films 40b and 40c, and electrically
connected to the electrode 40a is a DC power supply 42. A Coulombic
force generated by a DC voltage from the DC power supply 42 can
adsorb and hold the semiconductor wafer W on the chuck.
[0044] Installed in the susceptor 12 is an annular coolant
passageway 44 extended in., e.g., a circumferential direction.
Circulated through the coolant passageway 44 is a coolant of a
predetermined temperature such as cooling water from a chiller unit
46 through lines 48 and 50. The processing temperature of the
semiconductor wafer W on the electrostatic chuck 40 can be
controlled by the temperature of the coolant. Further, a thermally
conductive gas from a thermally conductive gas supply unit 52 such
as He gas is supplied between the top surface of the electrostatic
chuck 40 and the back side of the semiconductor wafer W through a
gas supply line 54.
[0045] The shower head 38 on the ceiling portion includes an
electrode plate 56 having a plurality of gas vent-holes 56a in the
bottom surface and an electrode supporting member 58 supporting the
electrode plate 56 detachably. Provided in the electrode supporting
member 58 is a buffer chamber 60, and coupled to a gas inlet
opening 60a of the buffer chamber 60 is a gas supply line 64 from a
processing gas supply unit 62.
[0046] Disposed around the chamber 10 is a magnet 66 extended in an
annular shape or a concentric shape. Formed in the gap between the
shower head 38 and the susceptor 12 in the chamber 10 is an RF
electric field of a vertical direction by the high frequency power
supply 32. By discharging a high frequency, a high density plasma
can be generated around the surface of the susceptor 12.
[0047] A controller 68 controls an operation of each unit in the
plasma etching apparatus such as the gas exhaust unit 28, the high
frequency power supply 32, the chiller unit 46, the thermally
conductive gas supply unit 52, the processing gas supply unit 62.
While performing a signal processing or an operation processing for
obtaining the measurement value of the DC potential V.sub.dc on the
basis of a surface potential measurement value (signal) from a
surface potential measurement unit 70 to be described later. In
addition, the controller 68 is also connected to an outer apparatus
(not shown) such as a host computer.
[0048] To carry out an etching in the plasma etching apparatus, the
gate valve 30 is opened first, and then the semiconductor wafer W
serving as an object to be processed is loaded into the chamber 10
to be mounted on the electrostatic chuck 40. Thereafter, an etching
gas (generally a gaseous mixture) from the processing gas supply
unit 62 is introduced into the chamber 10 at a predetermined flow
rate and flow rate ratio, and the pressure in the chamber 10 is
maintained to be a set value by the gas exhaust unit 28. Moreover,
the high frequency power from the high frequency power supply 32 is
supplied to the susceptor 12 with a predetermined power. Further,
the DC voltage from the DC power supply 42 is applied to the
electrode 40a of the electrostatic chuck 40, thereby holding the
semiconductor wafer W on the electrostatic chuck 40. The etching
gas injected from the shower head 38 is converted to a plasma
between both electrodes 12 and 38 by a high frequency discharge,
and a main surface of the semiconductor wafer W is etched by
radicals or ions generated by the plasma.
[0049] In the plasma etching apparatus, while the high frequency
from the high frequency power supply 32 is applied to the susceptor
12, a capacitor included in the matching unit 34 operates as a
blocking capacitor, thereby forming a DC component or a DC
potential V.sub.dc in the power feed rod 36 and the susceptor 12
coupled to the output side of the matching unit 34. Such a DC
potential V.sub.dc as a so-called self-bias voltage makes a
reactive ion etching (RIE) possible and can be served as a
parameter indicating a variation of etching conditions or a
maintenance parameter indicating a replacement timing of a related
component or a member.
[0050] Next, there will be described in detail a DC potential
measurement unit in the plasma etching apparatus. As shown in FIG.
1, the matching unit 34 is disposed under the chamber 10 as a
matching box. The power feed rod 36 is electromagnetically shielded
between the matching unit 34 and the bottom plate 10a of the
chamber 10 by a coaxial cylindrical conductor 72. The cylindrical
conductor 72 is coupled to the ground potential through the chamber
10 or an earth line (not shown). Installed at the cylindrical
conductor 72 is a surface potential system 70 with an appropriate
gap (for example, several cm) in a radial direction from the power
feed rod 36. The surface potential system 70 non-contactly measures
the electrostatic surface potential of the power feed rod 36
through an electrostatic capacitance and provides the controller 68
with a surface potential detection signal including a measurement
value information of the surface potential.
[0051] In FIGS. 2 to 4, there is illustrated a detailed
configuration around the surface potential system 70. The power
feed rod 36 is composed of an upper columnar conductor 36a whose
upper potion is coupled to the bottom surface or the rear surface
(FIG. 1) of the susceptor 12; a lower columnar conductor 36b whose
lower portion is coupled to the output terminal (not shown) of the
matching unit 34: and a bar-type connecting part 36c for detachably
connecting the lower end portion of the upper columnar conductor
36a with the upper end portion of the lower columnar conductor 36b.
As shown in FIG. 3, one side surface of the lower end portion of
the upper columnar conductor 36a and the upper end portion of the
lower columnar conductor 36b is cut off to be a planar surface, and
respective planar surfaces positioned to be co-planar as one
surface are contacted with each other in the axial direction. Then,
the bar-type connecting part 36c having a nearly semicircular cross
section for supplementing the cutoff portion of both columnar
conductors 36a and 36b is placed therein, thereby being linked as
one unit detachably with a bolt 76 and forming the circumferential
power feed rod 36.
[0052] The cylindrical conductor 72 surrounding the power feed rod
36 is made up of an upper cylindrical conductor 78 whose upper end
potion is coupled to the bottom plate portion of the chamber 10; a
lower cylindrical conductor 80 whose lower end portion is coupled
to the housing of the matching unit 34; and a cylindrical
connecting portion 82 interposed between the upper cylindrical
conductor 78 and the lower cylindrical conductor 80 at a position
of a height corresponding to the bar-type connecting part 36c, for
connecting both detachably. The cylindrical connecting portion 82
is composed of putting a pair of semi-cylindrical connecting parts
82a and 82b on either side into contact with each other to be
linked as one unit by a bolt 83 (FIG. 4) while extending the one
side semi-cylindrical connecting portion 82b toward the outside of
the radial direction. Disposed in a space provided in the inner
side of the semi-cylindrical connecting portion 82b having a large
radius is a probe 70a of the surface potential system 70.
[0053] The surface potential system 70 is made up of the probe 70a
installed inside the cylindrical connecting portion 82 as described
above; a potential detection unit 70b disposed outside thereof; and
a cable 70c electrically coupling the two of the probe 70a and the
potential detection unit 70b. As shown in FIG. 5, installed in the
probe 70a is a sensor electrode 84 of a tuning-fork type made of,
e.g., Se. Disposed in the potential detection unit 70b are an
oscillator 86 for oscillating the corresponding sensor electrode
84, a measurement circuit 88 including an amplifier for signal
processing a sensor output signal from the sensor electrode 84 and
so on.
[0054] An electrostatic capacitance C is generated between an
object to be measured, i.e., the power feed rod 36, and the sensor
electrode 84 in the probe 70a. If the sensor electrode 84 is
vibrated by applying thereto an AC driving signal from the
oscillator 86 in the potential detection unit 70b, the value of the
electrostatic capacitance C is changed with an AC component,
thereby obtaining an AC-modulated sensor output signal of the
surface potential of the power feed rod 36 from the sensor
electrode 84. The sensor output signal from the sensor electrode 84
is amplified and detected in the measurement circuit 88 in the
potential detection unit 70b, thereby obtaining a surface potential
detection signal including information such as a magnitude or a
polarity of the surface potential of the power feed rod 36.
[0055] Thus, on the basis of the surface potential detection signal
obtained from the surface potential system 70, the measurement
value of the surface potential of the power feed. rod 36 is
obtained by carrying out required signal processing and operation
processing at the controller 68 (FIG. 1). Generally, the
measurement value of the surface potential may be the measurement
value of the DC potential V.sub.dc and it may be amended if
necessary. Further, the measurement value of the DC potential
V.sub.dc is displayed through the host computer or the like, or it
is used as a maintenance value or a parameter for monitoring, e.g.,
a system state. Furthermore, employed as the surface potential
system 70 in accordance with the preferred embodiment may be, e.g.,
a surface potential system made by Trek, Inc. in the US.
[0056] As described above, in this preferred embodiment, the DC
potential V.sub.dc on the power feed rod 36 to which the high
frequency from the high frequency power supply 32 for use in a
plasma generation and an RIE is propagated is measured by employing
the surface potential system 70 of a non-contact manner. Therefore,
the high frequency is not leaked or discharged in a measurement
portion, that is, the surface potential system 70 though the high
frequency power is made to be high, and the measurement value of
the DC potential V.sub.dc can be obtained safely and accurately
without affecting a high frequency discharge or a plasma generation
between the lower electrode (susceptor) 12 and the upper electrode
(shower head) 38.
[0057] In addition, in this preferred embodiment, a
semi-cylindrical connecting portion 82b of one side of the
cylindrical connecting portion 82 detachably installed in the
vicinity of a joint place between the upper columnar conductor 36a
at the side of the chamber 10 and the lower columnar conductor 36b
at the side of the matching unit 34 is altered to install the probe
70a of the surface potential system 70 therein. Accordingly, this
configuration can be easily applied to a conventional plasma
etching apparatus.
[0058] Furthermore, since the DC potential V.sub.dc on the power
feed rod 36 is nearly same or constant throughout the whole power
feed rod 36, the DC potential V.sub.dc can be measured in any
region of the power feed rod 36 by the non-contact measurement
method of the preferred embodiment. Moreover, by the non-contact
measurement method of the preferred embodiment, the DC potential
V.sub.dc on the susceptor 12 also can be measured. In an actual
application, since the DC potential V.sub.dc of the susceptor 12 is
not significantly different from that of the power feed rod 36, the
DC potential V.sub.dc on the susceptor 12 can be approximated based
on the measurement value of the DC potential V.sub.dc obtained from
the power feed rod 36.
[0059] The plasma etching apparatus in the preferred embodiment is
of a type to apply the high frequency power for generating a plasma
to the susceptor 12. However, though not shown, the present
invention can be applied to a plasma etching apparatus of a type to
apply a high frequency power for generating a plasma to the upper
electrode 38 and in the case, a measurement value of a DC potential
V.sub.dc in the upper electrode 38 or the power feed rod (not
shown) directly connected thereto can be obtained safely and
accurately by the same non-contact measurement method as that of
the preferred embodiment.
[0060] In the following, there will be described an electrical
joint member in accordance with another aspect of the present
invention. Generally, a vacuum chamber and peripheral elements
thereof employed in a plasma processing apparatus are configured by
combining multiple members capable of being disassembled, and a
good airtightness or an electrical contact between joint members
are needed. In order to establish the electrical contact and joint,
an effective method is such that a conductive cushion member
serving as an electrical joint member is inserted between
conductive members joined with each other.
[0061] In accordance with the present invention, as will be
described later, there is provided an electrical joint member for
effectively reducing an electrical resistance between conductive
members joined with each other in a processing apparatus and
further, there is no concern over metal contamination in the
processing apparatus.
[0062] In FIG. 6, there is illustrated a configuration of the
plasma etching apparatus in which the electrical joint member in
accordance with the first embodiment of the present invention is
employed. In the drawing, parts having the substantially same
configuration or function as those of the plasma etching apparatus
in FIG. 1 are assigned the identical numeral.
[0063] The chamber 10 in the plasma etching apparatus is formed by
detachably linking as one unit the chamber main body member 10a
whose top surface is opened and the upper chamber member 10b
blocking the top surface opening of the chamber main body member
10a. Installed as one unit in the upper chamber member 10b is the
shower head 38 also serving as the upper electrode.
[0064] Disposed in the sidewall of the chamber main body member 10a
is a protruding port 100 having a loading/unloading port of the
semiconductor wafer W at a position of a height corresponding to
the gate valve (not shown), and installed in the inner side of the
main body member 10a is a cylindrical deposition shield 102 coating
the inner wall through, e.g., a spacer (not shown). The chamber
main body member 10a, the upper chamber member 10b and the
deposition shield 102 are all conductive members made of, e.g.,
aluminum.
[0065] The upper circumference of the deposition shield 102 is bent
at a right angle to the outside of a diametrical direction, and an
annular flange portion 102a, which is a peripheral region of the
bent, is inserted and attached between the top surface of the
chamber main body member 10a and the peripheral portion of the
upper chamber member 10b. Then, inserted between the top surface of
the flange portion 102a of the deposition shield 102 and the bottom
surface of the peripheral portion of the upper chamber member 10b
is an electrical joint member 104 in accordance with the first
embodiment.
[0066] Referring to FIGS. 7A and 7B, there are illustrated a
configuration of the electrical joint member 104. The electrical
joint member 104 is configured by forming a surface metal layer 108
made of aluminum, having a thickness of, e.g., 30 82 m on a surface
of a spiral 106 formed by using a strip-shaped body made of
stainless steel, which has a thickness of, e.g., 80 .mu.m and a
width W of, e.g., 2 mm or so. As for the manufacture of the
electrical joint member 104, it is possible, for example, to form
the first surface metal layer 108 made of aluminum on one surface
of a strip-shaped body made of stainless steel by evaporation or
CVD (Chemical Vapor Deposition) and then wind in a coil shape the
strip-shaped body with its surface on which the surface metal layer
108 is formed is made to be the outer surface or the exterior
surface, thereby producing the electrical joint member 104 having a
spiral shape and an outer diameter d of, e.g., about 2.4 mm, as
shown in FIG. 7B.
[0067] In this example, the spiral 106 forms an elastic body. If
stainless steel as a material of the elastic body is called a first
metal material, aluminum as a material of the surface metal layer
108 is a second metal material having a lower relative resistance
value than that of the first metal material and having no negative
effect on manufacturing a semiconductor device.
[0068] In FIG. 6, the joint portion between the flange portion 102a
of the deposition shield 102 and the upper chamber member 10b
accommodates the electrical joint member 104 in a recess portion
103 provided at a side of the flange portion 102a (FIG. 8) and
secures an electrical contact by pressing and fastening both by
bolts 110 (FIG. 9). Though the bolts 110 are not shown in FIG. 6,
the bolts 110 with the electrical joint member 104 are disposed at
multiple sites at regular intervals in a circumferential direction
of the chamber 10. In FIGS. 8 and 9, the depth of the groove
portion 103 is set to be smaller than the outer diameter d of the
electrical joint member 104. Thus, when the facing surfaces of the
conductive members 10b and 102a are joined by being fastened with
the bolts 110, the electrical joint member 104 gets compressed by a
predetermined amount, thereby determining the contact resistances
between the electrical joint member 104 and the conductive members
10b and between the electrical joint member 104 and the conductive
member 102a corresponding to the compressed value. As a modified
example, for example, as shown in FIG. 10, the electrical joint
member 104 may be interposed between the flat surfaces of the
conductive members 10b and 102a.
[0069] In FIG. 6, the deposition shield 102 having an electric
heater (not shown) has a function of improving a processing
efficiency by preventing a heat loss in the processing chamber 10
and extending a maintenance cycle by preventing an adhesion of a
reaction product. The lower portion of the deposition shield 102 is
bent inwardly, and joined on the top surface of the bent peripheral
region 102b is a bottom surface of an upper peripheral portion 112a
of a flow rectifying member 112 formed in a mortar shape through
the electrical joint member 104. Installed in the flow rectifying
member 112 are holes 112c through which a gas flows from the side
of the plasma processing space to the side of the gas exhaust line
20. The bottom surface of a lower peripheral portion 112b of the
flow rectifying member 112 is joined to the top surface of a
supporting ring 114 forming the bottom surface of the chamber 10
through the electrical joint member 104. The supporting ring 114 is
connected to the ground potential, and joined to the inner
peripheral surface thereof is the cylindrical conductor 72
surrounding the power feed rod 36. As in the plasma etching
apparatus of FIG. 1, the surface potential system 70 may be
installed in the cylindrical conductor 72. Further, both the flow
rectifying member 112 and the supporting ring 114 are made up of
conductive members made of, e.g., aluminum. The electrical joint
member 104 can also be used in the joint portion between the
supporting ring 114 and the cylindrical conductor 72.
[0070] Next, there will be described an operation of the plasma
etching apparatus. First, by a transfer arm (not shown), the
semiconductor wafer W as a substrate to be processed is loaded into
the chamber 10 through the loading/unloading port in the protruding
port 100 from a neighboring load-lock chamber (not shown) to be
mounted on the susceptor 12. Thereafter, by closing the gate valve
(not shown), the chamber 10 is made to be in an airtight state.
Then, the inside of the chamber 10 is evacuated through the gas
exhaust pipe 26, and a processing gas is introduced thereinto at a
predetermined flow rate through the shower head 38, thereby
maintaining the inside of the chamber 10 at a vacuum level of,
e.g., several tens of mTorr.
[0071] Meanwhile, a high frequency having a predetermined frequency
(for example, 100 MHz) from the high frequency power supply 32 is
applied to the susceptor (lower electrode) 12 with a predetermined
power (for example, 1500 W). Accordingly, the processing gas
between the susceptor 12 and the shower head 38 forming the upper
electrode is converted into a plasma, thereby performing an
etching, i.e., a plasma processing on the wafer W by the plasma.
Further, in addition to the high frequency for the plasma
generation, a high frequency having a predetermined frequency for
bias (for example, 3.2 MHz) from another high frequency power
supply (not shown) may be applied to the susceptor 12 in a
predetermined power (for example, 5800 W) in order to effectively
induce ions in the plasma onto the semiconductor wafer W. The high
frequency discharged from the susceptor 12 in the chamber 10 flows
to a side of the upper chamber member 10b through the plasma and,
further, flows to the earth (ground potential) through the
deposition shield 102, the flow rectifying member 112 and the
supporting ring 114.
[0072] In the conductive members 10b, 102, 112 and 114 which face
the plasma processing space of the plasma etching apparatus on
whose surfaces the high frequency flows, the contact resistance of
the electrical joint member 104 inserted in the joint surface
between the respective members is small, so that the electrical
resistance of the joint portion can be reduced effectively, thereby
making the potentials of the surface portions of the conductive
members uniform.
[0073] Here, the first metal material forming the spiral 106 in the
electrical joint member 104 of the present invention is not limited
to stainless steel. For example, it may be titanium or a copper
alloy made of, e.g., copper and beryllium (Be). Since the copper
alloy has the same elasticity as that of stainless steel as known
from an experimental example to be described later, it is effective
as an elastic body. Further, the second metal material forming the
surface metal layer 108 is not limited to aluminum. It can be any
material which has a lower resistivity than that of the first metal
material and has no negative effects on manufacturing a
semiconductor device. For example, excepting transition metals, an
alkali metals and alkaline-earth metals, any kind of metals, other
than aluminum, or an alloy of such metals may be used. The metal
material having the negative effects on manufacturing or processing
the semiconductor device implies the one which deteriorates the
characteristic thereof when added into the semiconductor device as
an impurity in a trace amount of, e.g., 1.times.10.sup.10
atoms/cm.sup.2; and one such example is copper. Moreover, it is
preferable that the resistivity of the second metal material is
lower than that of aluminum.
[0074] As described above, the surface metal layer 108 made of the
second metal material is formed on the surface of the first metal
material 106 forming the elastic body, thereby forming the elastic
body by selecting an elastic metal material without considering the
resistivity thereof. While, for the metal material of the surface
metal layer 108, the metal which has a low resistivity and no bad
influence on manufacturing the semiconductor device can be selected
without considering elasticity, so that the electrical joint member
104 having elasticity and a lower contact resistance between the
conductive members can be manufactured.
[0075] In addition, the elastic body forming the electrical joint
member 104 is not limited to the spiral if it is configured to have
elasticity but it may be another elastic structure body. Further,
it is not limited to that made up of the metal material. In the
electrical joint member 104 configured as shown in FIG. 11, formed
on the surface of a cylindrical elastic body 116 made of resin
which is an elastic organic compound is the surface metal layer 108
made of aluminum. In this example, formed on the surface of the
surface metal layer 108 is a protrusion 118 for further ensuring an
electrical contact.
[0076] Moreover, the surface metal layer 108 is not limited to that
is coated on the whole periphery of the elastic body. For example,
as shown in FIG. 12, formed on the surface of the spiral 120 made
of stainless steel which is the elastic body is the surface metal
layer 108 identical to that in FIG. 11, and a part of the surface
of the spiral 120 may be configured to expose. However, in case the
elastic body 116 or the spiral 120 includes the metal material such
as copper (Cu) which has an obvious negative effect on
manufacturing the semiconductor device, it is necessary to coat the
whole periphery thereof. The surface metal layer 108 illustrated in
FIGS. 11 and 12 may be joined to the surface of the elastic body
116 made of resin or the spiral 120 by using, e.g., an aluminum
foil.
[0077] Furthermore, as shown in FIGS. 13A and 13B, the electrical
joint member 104 may be configured that while a conductive joint
member 124, which is formed to bend both end portions of a
strip-shaped body made of, e.g., aluminum in a key shape in an
opposite direction, is inserted into the rectangular parallelepiped
shape elastic body 122 made of resin which is an organic compound,
the corresponding both end portions of the conductive joint member
124 is respectively exposed from the both surfaces of an elastic
body 122. This is an effective structure in that, though aluminum
does not possess elasticity, when both surfaces of resin serving as
the elastic body 122 are inserted between the conductive-members,
the conductive joint member 124 made of aluminum can have a
reaction force by a restoration force of the resin and, therefore,
a lower contact resistance can be obtained by a small stress. The
resin can be used in a range of an elastic margin if it is
compressed in an amount of, e.g., 30% of the length L of the
elastic body 122. In case of using the resin to be compressed in an
amount of, e.g., 20% of the length L when the corresponding
electrical joint member 104 is interposed between the conductive
members, the compressed amount thereof becomes 0.03 mm when the
length L is 0.15 mm and the compressed amount thereof becomes 0.3
mm when the length L is 1.5 mm. In this case, the material of the
conductive joint member 124 is not limited to aluminum. For
example, a metal material, which has a lower resistivity than that
of aluminum and has no influence on manufacturing a semiconductor
device, may be used.
[0078] As described above, in accordance with the present
invention, there is provided the electrical joint member produced
by forming the surface metal layer made of aluminum on the surface
of the elastic body. The electrical joint member is a composite
material constituted by an aluminum material having a low
resistivity but without resilience, and has elasticity in its
entirety and a low resistivity. By disposing such an electrical
joint member between the conductive members or the joint surfaces
joined together in the processing apparatus, the electrical
resistance between the conductive members can be effectively
reduced without causing metal contamination in the processing
apparatus, so that proper care can be taken on the processing
apparatus and a power loss can be reduced.
Embodiments
[0079] Next, there will be described an experiment carried out in
order to confirm the effect of the present invention.
[0080] (Making of an Electrical Joint Member)
A. Embodiment 1
[0081] An electrical joint member was obtained by forming the
surface metal layer made of aluminum having a thickness of 100
.mu.m on the surface of the spiral formed by using a strip-shaped
body made of stainless steel having a thickness of 80 .mu.m and a
width of 2 mm. This electrical joint member is referred to as an
embodiment 1.
B. Embodiment 2
[0082] An electrical joint member was obtained identically with the
preferred embodiment 1 except employing a BeCu spiral instead of
the spiral made of stainless steel as the elastic body. This
electrical joint member is referred to as an embodiment 2.
C. Embodiment 3
[0083] Only 1 cm was cut from a ring body made of resin called an
O-ring generally used as a vacuum sealing material. This was
employed as the elastic body and the outer surface thereof was
coated with an aluminum foil, thereby making an electrical joint
member. This is referred to as an embodiment 3.
D. COMPARATIVE EXAMPLE 1
[0084] An electrical joint member was obtained identically with the
preferred embodiment 1 except that the surface metal layer made of
aluminum is not formed. This electrical joint member is made up of
the spiral made of stainless steel and this is referred to as a
comparative example 1.
[0085] (Preliminary Test)
[0086] Tests were conducted to identify the degree of the in-plane
pressure of various parts in case of fastening with bolts the gap
between the conductive members employed in the plasma processing
apparatus by using the electrical joint member. The joint structure
of the conductive members and an image of the in-plane pressure are
illustrated in FIGS. 14A and 14B from a motif of the joint of the
deposition shield. The reference numeral 130 in FIGS. 14A and 14B
is referred to an electrical joint member, and the reference
numerals 132 and 134 are a conductive member at one side and
another conductive member at the other side, respectively. The
reference numeral 136 is a bolt hole and the reference numeral 138
is a bolt. The in-plane pressure was investigated at the
bolt-fastened place E1, the place E2 positioned 30 mm apart from
the bolt-fastened place and the place E3 where the electrical joint
member 130 was installed. The outer diameter of the conductive
member was 595 mm, and the conductive members were tightly fastened
with eight bolts disposed at identical intervals in a torque of 50
kgf cm. However, the in-plane pressure cannot be measured in an
actual apparatus. Therefore, by employing aluminum plates as test
pieces, the in-plane pressures corresponding to the respective
places E1 to E3 were obtained as the in-plane pressures per contact
surface of 10 mm by using a push pull gauge or a load cell
respectively depending on the magnitude of in-plane pressure.
[0087] As an image of the in-plane pressure is shown in FIG. 14B,
though the in-plane pressure in the bolt-fastened E1 is equal to or
more than 50 kgf, the in-plane pressure in the neighboring E2 is
equal to or less than 10 kgf. Further, since the in-plane pressure
of the place E3 in which the electrical joint member 130 is
installed cannot be directly measured, it is estimated to be over
at least 3 kgf from the result of interposing and squashing the
O-ring as the resin sealing. Moreover, the contact resistance of a
DC level was measured in a state where each in-plane pressure was
applied thereto to obtain that the contact resistance in the
bolt-fastened E1 was 1 to 6 m.OMEGA. and that in the neighboring E2
was equal to or more than 30 my. Further, the contact resistance
was measured in a state where a conventional spiral made of
stainless steel as the electrical joint member was interposed
between the test pieces and the in-plane pressure of 3 to 9 kgf was
applied thereto. As a result, the contact resistance was 37 to 49
m.OMEGA.. Accordingly, a large in-plane pressure cannot be obtained
in the other places except the bolt-fastened place even in a
bolt-fastened state and, therefore, a sufficiently low contact
resistance cannot be obtained in case the conventional spiral made
of stainless steel is employed as the electrical joint member.
[0088] (Estimation of the Contact Resistance)
[0089] The contact resistance of the DC level was measured under
the condition that the respective electrical joint members were
interposed between a pair of test pieces made of aluminum and the
in-plane pressure (the in-plane pressure per the length of 10 mm)
between the test pieces was set to be of a value by which a
compressed amount was 0.6 mm, thereby obtaining the following
result.
1 in-plane pressure contact resistance embodiment 1 3.7 kgf 4.6
m.OMEGA. embodiment 2 3.4 kgf 4.3 m.OMEGA. embodiment 3 9.6 kgf 4.2
m.OMEGA. comparative 2.4 kgf 41.7 m.OMEGA. example 1
[0090] The values of the embodiment 1 and the comparative example 1
are selected from the result values of the following experiments
and the each value of the embodiments 2 and 3 is data of only one
position. The in-plane pressures of the embodiments 1 and 2 are
nearly identical with those of the comparative example 1 and the
contact resistances of the embodiments 1 and 2 are lower by about
one order of magnitude than that of the comparative example 1. In
the embodiment 3, though the in-plane pressure is set to be large,
the contact resistance is nearly identical with those of the
embodiments 1 and 2.
[0091] In addition, by using a test apparatus associating a stage
moving unit employing a micrometer with a push pull gauge, the
stress applied to the electrical joint member, the compressed value
and the contact resistance of the DC level (the contact resistance
between a pair of test pieces) were investigated in case of the
embodiment 1 and the comparative example 1. The result is shown in
FIGS. 15 to 17. Further, the stress was calculated as the in-plane
pressure per the length of contact surface of 10 mm.
[0092] As known from FIG. 15, the compressed value of the
embodiment 1 is smaller than that of the comparative example 1 when
the same stress is applied thereto. Further, referring to FIG. 16,
the both contact resistances tend to become smaller little by
little according as the both crushed values become larger when the
compressed value is in the range of 0.6 to 2.4 mm. However, within
the range, the contact resistance of the embodiment 1 becomes
smaller by about one order of magnitude compared to that of the
comparative example 1 at the same compressed value. FIG. 17 shows
the result of deducing a relationship between the stress and the
contact resistance from FIGS. 15 and 16. The contact resistance of
the embodiment 1 becomes smaller by about one order of magnitude
compared to that of the comparative example 1 at the same stress.
Further, as known from FIG. 17, though the stress is made to be
larger over 8 kgf, the contact resistance of the comparative
example 1 is larger than that of the embodiment 1 to which the
stress of about 2 kgf is applied. Therefore, by coating a stainless
spiral with aluminum, a low contact resistance can be obtained by a
small stress.
[0093] (Conduction Test)
[0094] Tests were carried out to investigate the temperature rising
degree of a high frequency conduction path when the electrical
joint member was interposed in the conduction path. The contact
resistance between the electrical joint member and the conductive
path members against the high frequency was estimated according to
the temperature rising degree thereof. FIG. 18 shows the test
apparatus. The reference numeral 140 is a pipe constituting the
conductive path member divided into two portions 140a and 140b in
an axial direction. One end portion and the other end portion
thereof are connected to a high frequency power supply 146 and a
dummy load 148 through an incident power monitor 142 and an output
power monitor 144, respectively. Interposed between the two divided
pipe portions 140a and 140b is an electrical joint body 150 and the
pipe portions 140a and 140b are electrically contacted with each
other only through the electrical joint body 150. Further, the pipe
140 and a conductive bar 141 constituting the conductive path
member form a coaxial line having a characteristic impedance of 50
.OMEGA..
[0095] The surface temperature of the pipe 140 was measured by
thermocouples when a high frequency was applied to conduct through
the pipe 140 employing the above-described test apparatus for 80
minutes. The measurement points are as illustrated in FIG. 19.
Employed electrical joint bodies 150 were prepared in accordance
with the embodiment 1 and the comparative example 1. Each of the
prepared electrical joint bodies 150 was 30 mm in length. The
prepared electrical joint bodies 150 were disposed at two places
facing each other in a diametrical direction of the pipe 140. The
results for the cases where the high frequency was 100 MHz, 2 kW
are shown in FIG. 20, and the results for the cases where the high
frequency power was 2 MHz, 5 kW are represented in FIG. 21. The
vertical axes of FIGS. 20 and 21 represent the difference value
between an ambient temperature and a temperature measurement value
at each position and corresponds to an amount of temperature rising
due to conduction of a high frequency. Further, the results
obtained when carrying out the identical tests by employing a
single body type pipe without using the electrical joint body 150
in these tests are represented as "X" in the respective
drawings.
[0096] In case a high frequency power is 100 MHz and 2 kW, the
temperatures of the respective positions become stable after
increasing by 8 to 10.degree. C., and the temperature when the
embodiment 1 is employed is about 2.degree. C. lower than that when
the comparative example 1 is employed. Moreover, in case the high
frequency power is 2 MHz and 5 kW, the temperatures of the
respective positions are stable after increasing by 5 to 10.degree.
C., and the temperature when the embodiment 1 is employed is about
4.degree. C. lower than that when the comparative example 1 is
employed. Accordingly, by forming the surface metal layer made of
aluminum on the stainless spiral, the loss of the high frequency
can be decreased. Further, the fact that the temperature level
thereof is similar to that in case of using the single body type
pipe (though the temperature level in case of employing the single
body type pipe becomes slightly higher than that in case of using
the embodiment 1) proves that it is very effective to form the
surface metal layer made of aluminum.
[0097] In addition, the plasma etching apparatus in accordance with
the present invention is not limited to that of a parallel plate
type. For example, it may be an apparatus generating a plasma by
introducing a microwave into a chamber through an antenna or an
apparatus generating a plasma by employing an electron cyclotron
resonance. Further, the present invention can also be applied to
another apparatuses for plasma processing such as a plasma CVD, a
plasma oxidation, a plasma nitride, sputtering and so on. Moreover,
the electrical joint member in accordance with the present
invention can be applied to any type of processing apparatuses
having a vacuum chamber, not limited to the plasma processing
apparatus. The substrate to be processed in accordance with the
present invention is not limited to a semiconductor wafer, but it
may be various substrates for a flat panel display, a photomask, a
CD substrate, a print substrate and so forth.
[0098] 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 modifications may
be made without departing from the spirit and scope of the
invention as defined in the following claims.
* * * * *