U.S. patent application number 11/149226 was filed with the patent office on 2005-10-20 for liner for use in processing chamber.
Invention is credited to Donohoe, Kevin G..
Application Number | 20050230048 11/149226 |
Document ID | / |
Family ID | 23234545 |
Filed Date | 2005-10-20 |
United States Patent
Application |
20050230048 |
Kind Code |
A1 |
Donohoe, Kevin G. |
October 20, 2005 |
Liner for use in processing chamber
Abstract
A container for use in a processing chamber to lessen the amount
of contaminant particles found within the chamber after processing.
The container fits closely within the chamber and includes ports
for a gas conduit and a vacuum conduit. The container may be locked
to the chamber through a locking mechanism and a recess in the
container. The container may be guided into the chamber with a
plurality of chamfers. The container may be used in inductively
coupled plasma chambers, electron cyclotron resonance chambers, and
chambers capable of receiving microwaves.
Inventors: |
Donohoe, Kevin G.; (Boise,
ID) |
Correspondence
Address: |
DICKSTEIN SHAPIRO MORIN & OSHINSKY LLP
2101 L Street, NW
Washington
DC
20037
US
|
Family ID: |
23234545 |
Appl. No.: |
11/149226 |
Filed: |
June 10, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11149226 |
Jun 10, 2005 |
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10851076 |
May 24, 2004 |
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10851076 |
May 24, 2004 |
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10095441 |
Mar 13, 2002 |
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6739360 |
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10095441 |
Mar 13, 2002 |
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09765381 |
Jan 22, 2001 |
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6374871 |
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09765381 |
Jan 22, 2001 |
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09317629 |
May 25, 1999 |
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6234219 |
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Current U.S.
Class: |
156/345.48 ;
216/67 |
Current CPC
Class: |
H01L 21/6719 20130101;
H01J 37/32458 20130101; H01J 37/32477 20130101; H01J 37/32623
20130101; H01L 21/67069 20130101; H01J 37/321 20130101 |
Class at
Publication: |
156/345.48 ;
216/067 |
International
Class: |
C23F 001/00 |
Claims
What is claimed as new and desired to be protected by Letters
Patent of the United States is:
1-86. (canceled)
87. A system for processing a semiconductor workpiece, said system
comprising: an enclosed processing chamber having at least one
wall, an access door to an interior space, a vacuum port through
said wall and a gas port through said wall; and a locking mechanism
for locking a container within said interior space of said
processing chamber.
88. The system of claim 87, wherein said processing chamber has an
inner surface having a guiding mechanism for guiding insertion of
said container.
89. The system of claim 88, wherein said guiding mechanism
comprises a plurality of chamfers.
90. The system of claim 87, wherein said processing chamber is
adapted to conduct inductively coupled plasma reactions, said
processing chamber further comprising an electrode structure for
producing said plasma reactions.
91. The system of claim 90, wherein said electrode structure
comprises an inductive coil and a source of radio frequency
energy.
92. A system for plasma processing a semiconductor workpiece, said
system comprising: a processing chamber having at least one wall an
access door to an interior space of said processing chamber, an
interior surface, a vacuum port and a gas port through said chamber
wall; a guiding mechanism for guiding insertion of a container; a
vacuum conduit; and a gas conduit.
93. The system of claim 92, wherein said processing chamber has a
portion of a locking mechanism for locking said container to said
processing chamber.
94. The system of claim 92, wherein said processing chamber is
adapted to provide inductively coupled plasma reactions, said
processing chamber further comprising an electrode structure for
producing said coupled plasma reactions.
95. The system of claim 92, wherein said guiding mechanism
comprises a plurality of chambers.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the processing of work
pieces used in semiconductor fabrication. More particularly, the
present invention relates to a reusable container, or liner, for
use in a work piece plasma processing chamber.
BACKGROUND OF THE INVENTION
[0002] A plasma is a collection of electrically charged and neutral
particles. In a plasma, the density of negatively-charged particles
(electrons and negative ions) is equal to the density of
positively-charged particles (positive ions). Plasma generation may
be conducted by applying power to electrodes in a chamber of a
reactor. In diode or parallel plate reactors, power is applied to
one electrode to generate a plasma. In triode reactors, power is
typically applied to two of three electrodes to generate a
plasma.
[0003] In radio frequency (RF) plasma generation, for a diode
reactor, a sinusoidal signal is sent to an electrode of a pair of
electrodes. Conventionally, a chuck or susceptor is the powered
electrode. Examples of parallel plate reactors include the
5000MERIE from Applied Materials, Santa Clara, Calif.
[0004] A plasma source material, which typically includes one or
more gases, such as, for example, argon, silane (SiH.sub.4),
oxygen, TEOS, diethylsilane, and silicon tetrafluoride (SiF.sub.4),
is directed to an interelectrode gap between the pair of
electrodes. The amplitude of the RF signal must be sufficiently
high for a breakdown of plasma source material. In this manner,
electrons have sufficient energy to ionize the plasma source
material and to replenish the supply of electrons to sustain a
plasma. The ionization potential, the minimum energy needed to
remove an electron from an atom or molecule, varies with different
atoms or molecules.
[0005] In a typical triode reactor, three parallel plates or
electrodes are used. The middle or intermediate electrode is
conventionally located in between a top and bottom electrode, and
thus two interelectrode cavities or regions are defined (one
between top and middle electrode and one between middle and bottom
electrode). The middle electrode typically has holes in it.
Conventionally, both the top and bottom electrode are powered via
RF sources, and the middle electrode is grounded. Examples of
triode reactors are available from Lam Research, Fremont, Calif.,
and Tegal Corporation Ltd., San Diego, Calif.
[0006] Parallel plate and triode reactors generate capacitively
coupled plasmas. These are conventionally "low density" plasmas
(ion-electron density of less or equal to 10.sup.10 ions-electrons
per cm.sup.3) as compared with high-density (also known as "hi
density") plasmas which are generated by systems such as electron
cyclotron resonance (ECR) and inductively coupled plasma (ICP). For
ICP systems, an inductive coil (electrode) is conventionally driven
at a high frequency using an RF supply. The inductive coil and RF
supply provide a source power, or top power, for plasma generation.
In ECR systems, a microwave power source (for example, a magnetron)
is used to provide a top power. Both ICP and-ECR systems have a
separate power supply known as bias power or bottom power, which
may be employed for directing and accelerating ions from the plasma
to a substrate assembly or other target. In either case, voltage
that forms on a susceptor or chuck (also known as the direct
current (DC) bias), is affected by the bottom power (RF bias);
whereas, current is affected by the top power.
DESCRIPTION OF THE RELATED ART
[0007] It has been known that control of particulate contamination
is imperative for cost effective, high-yielding manufacture of VLSI
circuits. This control is by necessity increasing with increasingly
smaller lines, feature sizes and critical dimensions being designed
on such circuits. Contamination particles cause incomplete etching
of work pieces such as reticules or wafers in spaces between lines,
thus leading to an unwanted electrical bridge. Further,
contamination particles may induce ionization or trapping centers
in gate dielectrics or junctions or in reticule areas which will be
used in semiconductor fabrication, leading to electrical failure of
a fabricated part.
[0008] The major sources of contamination particles are personnel,
equipment, and chemicals. For example, people, by shedding of skin
flakes, create particles which are easily ionized and can cause
defects. It is estimated that particles sized from less than 0.01
micrometers to 200 micrometers and above should be of concern
during the processing of semiconductors. "Clean rooms" are
typically used for semiconductor manufacture, and through filtering
and other techniques, attempts are made to prevent entry of
particles with sizes of 0.03 micrometers and larger. It is
virtually impossible, however, to keep particles smaller than 0.03
micrometers out of a clean room.
[0009] To address the problem of semiconductor contamination, a
Standard Mechanical Interface (SMIF) system was devised. The SMIF
system provides a small volume of still, particle-free air, with no
internal source of particles, for transporting wafers. SMIF designs
are discussed in U.S. Pat. No. 5,752,796 (Muka) and U.S. Pat. No.
5,607,276 (Muka et al.).
[0010] While the SMIF system is useful for preventing particle
contamination during transport of the wafers, it is wholly
ineffective at preventing contamination during processing of the
wafers. The SMIF containers are used during the transport of the
wafers, but are removed when the wafers are placed in processing
chambers for wafer processing.
[0011] Particulate contamination builds up within work piece
processing chambers, such as a plasma processing chamber. This
build up of contaminants must be cleansed from the processing
chambers periodically. This entails considerable time and effort
and requires the removal of the processing chamber from a
production line. This, in turn, causes lost production time and
increases costs.
[0012] There is, thus, a need in the industry for a low cost and
effective method and apparatus for reducing the need to
periodically clean work piece processing chambers, such as a plasma
processing chamber.
SUMMARY OF THE INVENTION
[0013] The present invention provides a removable container which
is inserted into a processing chamber and in which the work piece
processing is carried out. The container has at least one side and
a base, as well as an ingress and egress for the work piece. The
container further includes one or more ports located in the side
which connect with ports of the processing chamber which provide
gasses or other materials used in processing. The container is made
of materials allowing the container to have an effective life at
least as long as the required processing, preferably allowing the
container to be reused a number of times. A locking mechanism may
be included to lock the container within the chamber.
[0014] The present invention also provides a system for processing
a semiconductor work piece. The system includes a processing
chamber and a removable container having the characteristics noted
in the preceding paragraph. In one aspect of the invention, the
processing chamber is a plasma processing chamber.
[0015] The present invention further provides a method of
processing a semiconductor work piece in which the work piece is
provided within a container, the container being removably inserted
in a work piece processing chamber, with the processing being
accomplished inside the container.
[0016] The invention may be used to process any work piece
associated with semiconductor fabrication including, but not
limited to, reticules, masks, leads, wafers, and packages.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is perspective view of a conventional plasma
processing chamber.
[0018] FIG. 2 is a top view of the processing chamber of FIG.
1.
[0019] FIG. 3 is a cross-sectional view taken along line 2-2 of
FIG. 2 of the chamber of FIG. 1 and a container constructed in
accordance with an embodiment of the present invention.
[0020] FIG. 4 is a perspective view showing the container of FIG. 3
and the chamber of FIG. 1.
[0021] FIG. 5 is a top view of the chamber of FIG. 1 showing the
interior of the chamber.
[0022] FIG. 6 is a partial cross-sectional view of a chamber and
container constructed in accordance with another embodiment of the
present invention.
[0023] FIG. 7 is a top view of a container constructed in
accordance with another embodiment of the present invention.
[0024] FIG. 8 is a partial cross-sectional view of a chamber and
container of FIG. 7.
[0025] FIG. 9 is a cross-sectional view of a chamber and of a
container constructed in accordance with another embodiment of the
present invention.
[0026] FIG. 10 is a close-up view of a locking mechanism taken
within circle XI of FIG. 3.
[0027] FIG. 11 is a cross-sectional view of a chamber and of a
container constructed in accordance with another embodiment of the
present invention.
[0028] FIG. 12 is a cross-sectional view of a chamber and of a
container constructed in accordance with another embodiment of the
present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] In the following description, the invention is described in
connection with a plasma processing chamber. However, this is
merely illustrative of one environment of use for the invention and
the invention is not to be considered as limited to that
environment. Also, the invention can be used with other work piece
processing chambers. In addition, the invention is described with
reference to a reticule, which is but one example of a work piece
which can be processed using the invention.
[0030] Referring now to the drawings, where like numerals designate
like elements, there is shown in FIG. 1 a reticule processing
chamber 10. The processing chamber 10, which is shown as being
generally cylindrical in shape, is an inductively coupled plasma
processing chamber and includes an inductive coil 16 as an
electrode wrapped around a side surface 14 thereof. The chamber 10
further includes a door 18 and an under surface 19. The door 18 is
conventionally made to allow ingress and egress of wafers, or other
semiconductor work pieces or integrated circuit packages, to be
processed within the chamber 10. A gas port 20 and a vacuum port 22
are provided in the door 18, as shown in FIG. 2. In addition, a
guiding mechanism, specifically a plurality of chamfers 15, FIG. 3,
are located on an inner surface of the side 14 of the chamber
10.
[0031] As noted above, in inductively coupled plasma systems, the
inductive coil, here coil 16, is driven at a high frequency using a
radio frequency (RF) supply 27. Together, the coil and the radio
frequency supply provide a source of power for the plasma
generation. As shown in FIGS. 1, 3, a wafer, or RF, chuck 26 is
provided through the under surface 19 of the chamber 10. The RF
supply 27, in electrical connection to the chuck 26, drives the
coil 16 at a high frequency, thereby providing the source of power
for the plasma generation within the chamber 10.
[0032] With further reference to FIG. 3, which is a cross-sectional
view that has been elongated for clarity of description of the
invention, a removable container, or liner, 30 is encased within
the processing chamber 10. The generally cylindrical container 30
has a base 32, an upper surface 34, and a side 36. The upper
surface 34 acts as a door for ingress and egress for a work piece,
which is illustrated as a reticule 50. It is, however, to be
understood that any type of semiconductor work piece may be used
with the container 30, such as wafers, lead frames, or integrated
circuit packages. The chuck 26 extends through the base 32, thereby
placing a top surface of the chuck 26 (upon which a work piece to
be processes will rest) within the chamber 30.
[0033] The container 30 may be formed of any suitable material
which is able to withstand the environment within the processing
chamber 30 for at least as long as the processing step. For
example, if a conductive material is necessary, the container 30
may be formed of a conductive material. Alternatively, the
container may be formed of a dielectric material, a partially
conducting material, an insulative material, or a combination of
these. Additionally, the container 30 may be formed of a material
which would allow it to be subjected to more than one processing of
a work piece, prior to being cleaned or discarded.
[0034] The upper surface 34 of the container 30 includes a gas port
38 and a vacuum port 40. The ports 38,40 align with the processing
chamber ports 20, 22 when the container 30 is positioned within the
processing chamber 10.
[0035] As shown in FIGS. 1-3, a gas conduit 60 extends from the
port 20 of the chamber 10. It is important that the gas ports 20
and 38 closely align. Port 20 is in sealing and fluid communication
with the port 38 of the container 30. Further, a vacuum conduit 70
extends from the port 22 of the chamber 10. It is somewhat less
important for the vacuum ports 22, 40 to closely align. While close
alignment of the vacuum ports 22, 40 may be preferable, exerting a
high speed vacuum in a closed system (the chamber 10) will pump the
gas out of the container 30 even if the ports 22, 40 are not
closely aligned. As shown in FIG. 3, the port 22 is closely aligned
to the port 40 of the container 30. Compliant sealing members 62
and 72 are placed between the container 30 and processing chamber
10 in a space 82 and around the ports 20, 38 and 22, 40,
respectively, to provide a seal preventing fluids which pass
through the ports from escaping into the space 82 between the
container 30 and the processing chamber 10. The conduits 60, 70 may
be pipes, hoses, or any other suitable member defining an interior
space.
[0036] Alternatively, with reference to FIG. 6, the gas conduit 60
and vacuum conduit 70 may only extend into the upper surface 34 of
the container 30. A mating gas conduit 60' is fit within the port
38 and is adapted to mate with the conduit 60. The sealing member
62 is placed in position to seal the junction between the conduits
60 and 60'. A mating vacuum conduit 70' is fit within the port 40
and is adapted to mate with the vacuum conduit 70. The sealing
member 72 is placed in position to seal the junction between the
conduits 70 and 70'. The compliant sealing members 62, 72 may be
any suitable seal, such as an O-ring or hose clamp. Further, the
sealing members 62, 72 may not be separate sealing devices, but
instead may be devices built into the hoses. For example, sealing
member 62 may be a push-fit seal positioned at an end of the
conduit 60 such that the conduits 60 and 60' may mate with and be
sealed together through pushing the conduit 60' into the sealing
member 62.
[0037] With reference to FIGS. 7, 8, the container 30 is shown with
another aspect of the invention. To more symmetrically pump the gas
and non-volatile reaction products, and thereby more efficiently
clean the interior of the container 30, a plurality of vacuum ports
40' are located on the upper surface 34 of the container 30. The
ports 40' spread out the vacuuming throughout the space 80 within
the container 30. Thus, a more even vacuuming of the space 80 may
be accomplished. The vacuum conduit 70 should be of sufficient size
to encircle all of the ports 40'. As illustrated, the vacuum
conduit 70 is not sealed to the upper surface 34 around the ports
40'. Alternatively, the vacuum conduit 70 may be sealed to the
upper surface 34.
[0038] It is required that gas pumping, or vacuuming, speeds must
be relatively high, and thus, it is necessary to provide a
sufficiently large opening through which to pump the gas.
Preferably, the conduit 70 should be between six and twenty inches
in diameter. The ports 40', as shown in FIGS. 7, should number
between ten to twenty ports, each being between 0.02 and 0.04
inches in diameter. Contrarily, the size of a single gas conduit 60
need not be as large as the vacuum conduit 70. Preferably, the
diameter of a single gas conduit 60 should be in the range of about
0.4 inches. The gas may be injected into the container 30 through a
single gas port 38, as shown in FIG. 3, or alternatively, the gas
may be injected through a multiple of smaller gas ports, much like
the multiple ports 40' shown in FIGS. 7. The multiple gas ports,
typically called a gas distribution system or a gas showerhead, may
be used to obtain greater uniformity of gas distribution within the
container 30.
[0039] The container 30 may be manually placed within the chamber
10. The chamfers 15, which have an increasing radial height in a
direction from the upper surface 34 to the under surface 36, assist
in aligning the container 30 properly within the chamber. Robotic
systems may be used to mechanically place the container 30 in the
chamber 10. Examples of suitable robotic systems include those
having robot arms which are pre-aligned during maintenance and
those having robot arms which are self-aligning. An important
aspect of the container 30 is that it protects the wafer or
reticule 50 from particles contamination caused during insertion of
the container 30 within the chamber 10, such as, for example, by
striking one of the chamfers 15.
[0040] Next will be described an alternative embodiment of the
chamber 10 and the container 30 whereby they are supported
horizontally. FIG. 9 shows a horizontal processing chamber 310 and
a container 330; specifically, lying on a chamber side 314 and a
container side 336 with a door 318, an under surface 319, an upper
surface 334 and a base 332 all in a vertically directed plane. The
wafer chuck 326 and the RF supply 27 are positioned under the side
314 of the chamber 310, and inductive coils 316 are positioned
above the chuck 326 on the top side of the side 314. The reticule
50 is positioned above the chuck 326 when the container 330 is
placed within the chamber 310.
[0041] A locking apparatus which releasably locks the container 330
to the chamber 310 is shown in FIGS. 9, 10. The locking mechanism
includes a hole 323 provided through the chamber side 314 and a
recess 342 provided in the container side 336. A biased locking pin
55 passes through the hole 323. The pin 55 is spring loaded and
biased upwardly toward the recess 342. Further, the pin 55 has a
rounded head 56 to facilitate locking. Alternatively, the pin 55
may have a tapered or angled head 56. As the container 330 is
placed in the chamber 310, the container side 336 slides along the
chamber side 314. Alternatively, this embodiment may include the
chamfers 15, in which case the container side 336 would slide along
the chamfers 15. When a portion of the container side 336 reaches
the pin 55, it presses the pin 55 downwardly against the biasing
force. When the recess 342 reaches the locking pin 55, the pressure
pushing the pin 55 downwardly is released, allowing the pin 55 to
move upwardly into the recess 342, thereby locking the container
330 into place within the chamber 310. The pin 55 may be pulled
down manually, or by other means, to later unlock and release the
container 330 from the chamber side 314. The recess 342 can be
formed of a sufficient length to ensure that the recess 342 meets
up with the pin 55.
[0042] Although the apparatus for locking the container 330 to the
chamber 310 is shown as a spring-loaded locking pin 55 and a recess
342, it is to be understood that the container 330 may be locked
into position within the chamber 310 in a variety of different
ways. Further, although the locking mechanism has been described in
terms of the FIG. 9 embodiment, it is to be understood that the
locking mechanism may be included in the embodiments shown in FIGS.
3,6,8, 11, and 12.
[0043] Next will be described the operation of the container 30
(FIG. 3) within the chamber 10. The reticule 50 is placed within
the container 30, the latter of which is guided into place within
the chamber 10 by the chamfers 15. The gas conduit 60 and the
vacuum conduit 70 each extend through the container 30 and are
sealed thereto with, respectively, the sealing members 62, 72.
Alternatively, the gas and vacuum conduits 60, 70 are mated with,
respectively, the conduits 60', 70', and sealed together with the
sealing members 62, 72. Gas is introduced to a space 80 within the
container 30 through the gas conduit 60. Pressure within the
container 30 may be equalized to the pressure in the space 82
through a plurality of pores 44 in a side 36 of the container 30.
The RF supply 27 then drives the inductive coil 16. The amplitude
of the RF signal from the RF supply 27 needs to be sufficiently
high to interact and breakdown the gas, which acts as the plasma
source material. Thus, the type of gas will have a bearing upon the
amplitude of the RF signal necessary from the RF supply 27. The
manner of creating a plasma, including the necessary gas
compositions and RF voltages needed for desired processing
conditions are well known in the art and are not described in
detail herein.
[0044] As the plasma generated species react in the space 80 with
the materials on the reticule 50, the vacuum introduced to the
container 30 through the vacuum conduit 70 pulls volatile reaction
products from the container 30. The build up of non-volatile
reaction products will occur on the interior walls of the container
30.
[0045] By utilizing the container 30, less defects are deposited on
the work piece during the processing. Further, the chamber 10 is
not exposed to as many contaminant particles during the processing.
Thus, the chamber 10 need not be wet cleaned as frequently, thus
eliminating many of the re-qualifications of the chamber 10. The
container 30 itself, provided it is in a good condition to be
utilized again after the processing, may be cleaned and/or
refurbished and used again. Otherwise, the container 30 may be
discarded.
[0046] FIG. 11 shows another preferred embodiment of the present
invention. A chamber 100 and a container 130 are shown in FIG. 11.
The chamber 100 is generally cylindrical and includes an upper
section 101 having a dome portion 102, and the generally
cylindrical container 130 likewise includes a dome portion 132
which fits within the dome portion 102. The upper section 101 of
the chamber 100 may be lowered onto and secured to a lower section
103 after the container 130 is placed inside the chamber 100. A
space 180 is located within the dome portion 132 and in the upper
reaches of the rectangular portion of the container 130. The space
180 denotes an area within the container, like space 80, within
which plasma products are formed through a reaction between the RF
signal from the RF supply 27, the inductive coil 16 and the gas,
which is introduced through the gas conduits 60. Vacuum conduits 70
are positioned at a lower position of the chamber 130. As with
previously discussed embodiments, the conduits 60, 70 may mate with
conduits 60', 70', respectively, and be sealed with sealing members
62, 72. The container 130 may be guided into the chamber 100
through a guiding mechanism, such as the previously described
chamfers 15, or any other suitable guiding mechanism. The chamber
100 and the container 130 may be supported horizontally or
vertically, and a releasable locking mechanism, such as the locking
pin 55, may be utilized to lock the container 130 into place within
the chamber 100.
[0047] Another preferred embodiment of the present invention is
shown in FIG. 12. Here, a dome-shaped processing chamber 200 is
shown encasing a dome-shaped removable container 230. The chamber
200 is a microwave-generated plasma chamber. Alternatively, it may
be an electron cyclotron resonance chamber. The chamber 200 is
grounded by a pair of grounding plates 90.
[0048] Unlike inductively coupled plasma chambers, such as chambers
10, 100, the chamber 200 does not utilize a coil in conjunction
with an RF supply to produce plasma. Instead, the microwaves 216,
from a microwave power source 218 shown schematically, provide
power to generate plasma within a space 280 within the container
230. The microwave power source 218 may be any suitable source,
such as, for example, a magnetron. In this embodiment, the
container 230 is preferably formed of a dielectric material. The
chamber 200 includes a top portion 201 which is detachable from and
securable to a bottom portion 203. The top portion 201 is removed,
allowing the container 230 to be placed within the chamber 200.
[0049] Modifications can be made to the invention and equivalents
substituted for described and illustrated structures without
departing from the spirit or scope of the invention. For example,
although the container 30 has been discussed in terms of diode
processing reactors, or chambers, it is to be understood that the
container 30 may be used with triode reactors or any other form of
chamber used to process semiconductor work pieces. Further, while
certain methods of plasma generation have been discussed herein,
such as inductively coupled plasma, electron cyclotron resonance,
and microwave, other methods of plasma generation may be utilized
in the invention, such as, for example, parallel plate etchers,
diodes, magnetically enhanced reactive ion etching (MERIE), and
surface wave plasma. Additionally, although two ports are shown for
processing a plasma, more or less ports may be used depending on
the type of processing which needs to be done. Further, although
conduits 60, 60', 70, and 70' have been described for pumping gas
in and out of the container 30, it is to be understood that other
apparatus may be used, such as, for example, a plate having a
plurality of openings positioned on a wall of the container 30
which is mated to a conduit. Accordingly, the scope of the present
invention is not to be considered as limited by the specifics of
the particular structure which have been described and illustrated,
but is only limited by the scope of the appended claims.
* * * * *