U.S. patent application number 10/740335 was filed with the patent office on 2004-07-08 for plasma treatment of processing gases.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Lazarovich, Stela Diamant, Rosenberg, Avner, Shiloh, Joseph, Statlender, Joseph, Wurzberg, Elhanan.
Application Number | 20040131513 10/740335 |
Document ID | / |
Family ID | 25392703 |
Filed Date | 2004-07-08 |
United States Patent
Application |
20040131513 |
Kind Code |
A1 |
Lazarovich, Stela Diamant ;
et al. |
July 8, 2004 |
Plasma treatment of processing gases
Abstract
The present invention provides a DBD cell (500) including ring
shaped electrodes (512 and 514) that are positioned side-by-side on
a dielectric tube (516). An AC power supply (518) is provided such
that the cell and the power supply form a DBD treatment device
(540) for abatement of noxious gases for example FCs that can be
discharged from semiconductor fabricating devices. Additionally,
one or more sensors (822) and/or one or more gas addition ports
(816) can be included in a DBD cell (800) of the present invention.
Several DBD cells (1030, 1036 and 1042) of the present invention
can be combined to form a DBD reactor (1010) of the present
invention. AC power supplies (1012, 1014 and 1016) are utilized to
energize the cells (1030, 1036 and 1042), forming a novel noxious
gas treatment device (1000) wherein plasmas are created when gas is
present inside the reactor. A DBD treatment device (1314) of the
present invention can be operably connected to the gas discharge
system of a semiconductor fabricating device (1310), forming a
novel semiconductor processing system. Furthermore, DBD devices of
the present invention (1714) can be utilized to form fluorine
species for use in chemical processing methods, techniques and
devices including wafer fabricating devices (1718). Additionally,
DBD treatment devices of the present invention (1540, 1542 and
1544) can be integrated with vacuum pump stages (1520, 1522, 1524,
1526 and 1528) to form a novel pump integrated DBD treatment
apparatus (1500).
Inventors: |
Lazarovich, Stela Diamant;
(Herzliya, IL) ; Rosenberg, Avner; (Beit Shearim,
IL) ; Shiloh, Joseph; (Haifa, IL) ;
Statlender, Joseph; (Haifa, IL) ; Wurzberg,
Elhanan; (Kiriat Motzkin, IL) |
Correspondence
Address: |
Patent Counsel
APPLIED MATERIALS, INC.
P. O. Box 450-A
Santa Clara
CA
95052
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
25392703 |
Appl. No.: |
10/740335 |
Filed: |
December 17, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10740335 |
Dec 17, 2003 |
|
|
|
09888191 |
Jun 22, 2001 |
|
|
|
6685803 |
|
|
|
|
Current U.S.
Class: |
422/186.04 ;
422/186.21 |
Current CPC
Class: |
H05H 1/2406 20130101;
H01J 37/32844 20130101; B01D 53/326 20130101; H01J 37/32348
20130101; H01J 37/32009 20130101; H05H 1/2465 20210501; Y02C 20/30
20130101 |
Class at
Publication: |
422/186.04 ;
422/186.21 |
International
Class: |
B01J 019/08; B01J
019/12 |
Claims
We claim:
1. A DBD cell comprising: a) a substantially cylindrical dielectric
tube having (1) a tube wall and (2) an outside surface; b) a first
electrically conductive electrode positioned on the outside surface
of the tube and encircling the tube; c) a second electrically
conductive electrode positioned on the outside surface of the tube
and encircling the tube, wherein (1) the second electrode is
positioned a distance D from the first electrode and (2) the first
and second electrodes are placed in a side-by-side position, and
wherein the cell is adapted for forming a plasma inside the tube
through dielectric barrier discharge such that high frequency
energy is capacitively discharged through the tube wall.
2. The cell of claim 1 wherein the first and second electrodes
comprise electrode segments.
3. The cell of claim 2 wherein the first and second electrodes each
include at least one fastener having a biasing element for urging
the segments of each cell together.
4. The cell of claim 1 wherein distance D ranges from about 10 mm
to about 30 mm.
5. The cell of claim 1 wherein the first and second electrodes
comprise shapes selected from the group consisting of rings and
cylindrical bands.
6. The cell of claim 1 wherein the first and second electrodes
include heat exchange elements.
7. The cell of claim 1 additionally comprising: a) a first
electrical contact formation included in the first electrode; and
b) a second electrical contact formation included in the second
electrode.
8. The cell of claim 1 additionally comprising: a) a first gap
between the first electrode and the tube's outside surface; and b)
a second gap between the second electrode and the tube's outside
surface.
9. The cell of claim 8 additionally comprising an electrically
insulating paste positioned in the first and second gaps.
10. The cell of claim 9 wherein the paste comprises one or more
materials selected from the group consisting of silicones,
polytetrafluoreoethylene- , and mixtures of perfluoropolyethers and
polytetrafluoroethylene.
11. The cell of claim 1 additionally comprising one or more ports
for introducing one or more gases.
12. The cell of claim 1 additionally comprising one or more
sensors.
13. The cell of claim 1 additionally comprising one or more optical
windows.
14. The cell of claim 1 wherein the tube comprises a material
selected from the group consisting of alumina, quartz and
sapphire.
15. The cell of claim 1 additionally adapted for treating a gas by
generating a plasma in the gas.
16. A DBD reactor comprising: a) a first DBD cell including: (1) a
substantially cylindrical dielectric tube having a tube wall and an
outside surface, (2) a first electrically conductive electrode
positioned on the outside surface of the tube and encircling the
tube, (3) a second electrically conductive electrode positioned on
the outside of the tube and encircling the tube, wherein (i) the
second electrode is positioned a first distance from the first
electrode, and (ii) the first and second electrodes are placed in a
side-by-side position, and (4) wherein the first cell is adapted
for forming a plasma inside the tube through dielectric barrier
discharge such that high frequency energy is capacitively
discharged through the tube wall; and c) at least a second DBD cell
including: (1) the tube, (2) a third electrically conductive
electrode positioned on the outside surface of the tube and
encircling the tube and (3) a fourth electrically conductive
electrode positioned on the outside of the tube and encircling the
tube, wherein (i) the fourth electrode is positioned a second
distance from the first electrode and (ii) the third and fourth
electrodes are placed in a side-by-side position, and (4) wherein
the second cell is adapted for forming a plasma inside the tube
through dielectric barrier discharge such that high frequency
energy is capacitively discharged through the tube wall.
17. A DBD treatment device comprising: a) a first DBD cell
including: (1) a substantially cylindrical dielectric tube having
an outside surface, (2) a first electrically conductive electrode
positioned on the outside surface of the tube and encircling the
tube and (3) a second electrically conductive electrode positioned
on the outside of the tube and encircling the tube, wherein (i) the
second electrode is positioned a distance D from the first
electrode and (ii) the first and second electrodes are placed in a
side-by-side position; and b) an AC power supply electrically
connected to the first and second electrodes, such that the power
supply is adapted for energizing the cell to form a plasma through
dielectric barrier discharge when a gas is present inside the
tube.
18. The device of claim 17 wherein the AC power supply comprises a
switched mode resonant high voltage power supply.
19. The device of claim 17 wherein the AC power supply comprises:
a) a DC power supply; b) a capacitor in parallel with the DC power
supply; and c) electrical components connected in series including:
(1) an inductor, (2) a primary winding of a transformer and (3) a
MOSFET switch having a snubber capacitor in parallel with the
switch and wherein the series is in parallel with the DC power
supply.
20. The device of claim 19 wherein the DC power supply comprises a
DC power supply providing a DC voltage input to the components
connected in series, wherein the input voltage ranges from 30 V to
48 V.
21. The device of claim 19 wherein the DC power supply is a
constant power DC power supply.
22. The device of claim 19 additionally comprising an electrical
circuit including a secondary winding of the transformer, wherein
the electrical circuit is adapted for energizing the cell by
applying an AC voltage.
23. The device of claim 22 wherein the AC voltage has a frequency
of about 900 kHz and a peak voltage of about 3 KV.
24. The device of claim 17 wherein the distance D ranges from about
10 mm to about 30 mm.
25. A DBD treatment device comprising: a) a DBD reactor including:
(1) a first DBD cell including: (i) a substantially cylindrical
dielectric tube having an outside surface, (ii) a first
electrically conductive electrode positioned on the outside surface
of the tube and encircling the tube and (iii) a second electrically
conductive electrode positioned on the outside of the tube and
encircling the tube, wherein the second electrode is positioned a
first distance from the first electrode and wherein the first and
second electrodes are placed in a side-by-side position, and (2) at
least a second DBD cell including: (i) the tube, (ii) a third
electrically conductive electrode positioned on the outside surface
of the tube and encircling the tube and (iii) a fourth electrically
conductive electrode positioned on the outside of the tube and
encircling the tube, wherein the fourth electrode is positioned a
second distance from the third electrode and wherein the third and
fourth electrodes are placed in a side-by-side position; b) a first
AC power supply electrically connected to the first and second
electrodes, such that the first power supply is adapted for
energizing the first cell to form a plasma through dielectric
barrier discharge when a gas is present in the tube; and c) a
second AC power supply electrically connected to the third and
fourth electrodes, such that the second power supply is adapted for
energizing the at least second cell to form a plasma through
dielectric barrier discharge when a gas is present in the tube.
26. The treatment device of claim 25 wherein the first and second
AC power supplies are adapted for being controlled independently of
each other.
27. The treatment device of claim 25 additionally comprising: a)
first DC power supply adapted for providing AC power to the first
AC power supply; b) and a second power supply adapted for providing
DC power to the second AC power supply, wherein the first and
second DC power supplies are adapted for being controlled
independently of each other.
28. A pump integrated DBD treatment apparatus comprising: a) n
vacuum pump stages; and b) n minus 2 DBD treatment devices
integrated with the n vacuum pump stages wherein each of the n
minus 2 DBD treatment devices comprises at least one DBD cell
including: (1) a substantially cylindrical dielectric tube having
an outside surface, (2) a first electrically conductive electrode
positioned on the outside surface of the tube and encircling the
tube and (3) a second electrically conductive electrode positioned
on the outside of the tube and encircling the tube, wherein (i) the
second electrode is positioned a first distance from the first
electrode and (ii) the first and second electrodes are placed in a
side-by-side position and (4) an AC power supply electrically
connected to the first and second electrodes, such that the power
supply is adapted for energizing the cell to form a plasma through
dielectric barrier discharge when a gas is present inside the
tube.
29. The apparatus of claim 28 wherein the n vacuum pump stages each
comprise a Roots vacuum pump stage.
30. The apparatus of claim 28 wherein the AC power supply comprises
a switched mode resonant high voltage power supply.
31. The apparatus of claim 28 wherein each of the n minus 2 DBD
devices is adapted for being energized by an AC power supply that
provides an AC frequency that is different from the AC frequencies
of the other AC power supplies of the apparatus.
32. A semiconductor processing system comprising: a) a
semiconductor fabricating device; b) at least one DBD cell
including: (1) a substantially cylindrical dielectric tube having a
tube wall and an outside surface, (2) a first electrically
conductive electrode positioned on the outside surface of the tube
and encircling the tube; (3) a second electrically conductive
electrode positioned on the outside of the tube and encircling the
tube, wherein (i) the second electrode is positioned a distance D
from the first electrode and (ii) the first and second electrodes
are placed in a side-by-side position, and (4) wherein the at least
one DBD cell is adapted for forming a plasma inside the tube
through dielectric barrier discharge such that high frequency
energy is capacitively discharged through the tube wall; and c) a
gas flow connection between the fabricating device and the
tube.
33. The system of claim 32 wherein the first and second electrodes
comprise shapes selected from the group consisting of rings and
cylindrical bands.
34. The system of claim 32, wherein the semiconductor fabricating
device comprises an etch chamber.
35. The system of claim 32 wherein the DBD cell is adapted for
treating one or more gaseous compounds that are discharged from the
fabricating device.
36. The system of claim 32 wherein the DBD cell is adapted for
generating fluorine species for use in the fabricating device.
37. A semiconductor processing system comprising: a) a
semiconductor fabricating device; b) a DBD treatment device
including: (I) a DBD reactor having (1) a first DBD cell including:
(i) a substantially cylindrical dielectric tube having an outside
surface, (ii) a first electrically conductive electrode positioned
on the outside surface of the tube and encircling the tube and
(iii) a second electrically conductive electrode positioned on the
outside of the tube and encircling the tube, wherein the second
electrode is positioned a first distance from the first electrode
and wherein the first and second electrodes are placed in a
side-by-side position, and (2) at least a second DBD cell
including: (i) the tube, (ii) a third electrically conductive
electrode positioned on the outside surface of the tube and
encircling the tube and (iii) a fourth electrically conductive
electrode positioned on the outside of the tube and encircling the
tube, wherein the fourth electrode is positioned a second distance
from the third electrode and wherein the third and fourth
electrodes are placed in a side-by-side position, (II) a first AC
power supply electrically connected to the first and second
electrodes such that the first power supply is adapted for
energizing the first cell to form a plasma through dielectric
barrier discharge, and (III) a second AC power supply electrically
connected to the third and fourth electrodes such that the second
power supply is adapted for energizing the second cell to form a
plasma through dielectric barrier discharge; and c) a gas flow
connection between the fabricating device and the tube.
38. The system of claim 37 additionally comprising: a) a
controller; and b) an interlock feature in connection with the
controller.
39. The system of claim 38 wherein the controller is adapted for
interacting with (1) the fabricating device and (2) the DBD
treatment device.
40. The system of claim 38 wherein the interlock feature is adapted
for interacting with the DBD treatment device.
41. The system of claim 40 wherein the interlock feature is adapted
for stopping the plasma treatment upon an occurrence of a
pre-defined processing condition.
42. A semiconductor processing system comprising: a) a
semiconductor fabricating device; b) a pump integrated DBD
treatment apparatus comprising: (1) n vacuum pump stages and (2) n
minus 2 DBD treatment devices integrated with the n vacuum pump
stages wherein each of the n minus 2 DBD treatment devices
comprises at least one DBD cell including: (i) a substantially
cylindrical dielectric tube having an outside surface, (ii) a first
electrically conductive electrode positioned on the outside surface
of the tube and encircling the tube and (iii) a second electrically
conductive electrode positioned on the outside of the tube and
encircling the tube, wherein the second electrode is positioned a
distance D from the first electrode and the first and second
electrodes are placed in a side-by-side position and (iv) an AC
power supply electrically connected to the first and second
electrodes, such that the power supply is adapted for energizing
the cell to form a plasma when a gas is present inside the tube;
and c) a gas flow connection between the fabricating device and the
pump integrated DBD treatment apparatus.
43. The system of claim 42 wherein the n vacuum pump stages each
comprise a Roots vacuum pump stage.
44. The system of claim 42 wherein the AC power supply comprises a
switched mode resonant high voltage power supply.
45. A chemical processing system comprising: a) a chemical
processing device; b) a DBD cell including: (1) a substantially
cylindrical dielectric tube having an outside surface, (2) a first
electrically conductive electrode positioned on the outside surface
of the tube and encircling the tube; and (3) a second electrically
conductive electrode positioned on the outside of the tube and
encircling the tube, wherein (i) the second electrode is positioned
a distance D from the first electrode and (ii) the first and second
electrodes are placed in a side-by-side position; and c) a gas flow
connection between the processing device and the tube.
46. A method of treating a first gas, the method comprising: a)
energizing a first DBD cell including: a substantially cylindrical
dielectric tube having (1) an inside, (2) an outside surface, (3) a
first electrically conductive electrode positioned on the outside
surface of the tube and encircling the tube, and (4) a second
electrically conductive electrode positioned on the outside surface
of the tube and encircling the tube, wherein (i) the second
electrode is positioned a distance D from the first electrode and
(ii) the first and second electrodes are placed in a side-by-side
position; b) flowing the first gas through the inside of the tube;
and c) generating a first plasma in the gas through dielectric
barrier discharge inside the tube, wherein a first treated gas is
formed.
47. The method of claim 46 wherein distance D ranges from about 10
mm to about 30 mm.
48. The method of claim 46 wherein the first and second electrodes
comprise shapes selected from the group consisting of rings and
cylindrical bands.
49. The method of claim 46 wherein the first and second electrodes
include heat exchange elements.
50. The method of claim 46 wherein the first gas comprises one or
more gases selected from the group of gases consisting of
fluorocarbon gas, NF.sub.3, mixtures of fluorocarbon gas and inert
gas, and mixtures of NF.sub.3 and inert gas.
51. The method of claim 46 wherein the first gas comprises one or
more gases that are discharged from a semiconductor fabricating
device.
52. The method of claim 46 wherein the first gas comprises one or
more gases that are discharged from a chemical processing
device.
53. The method of claim 46 additionally comprising adding a second
gas to the first gas, such that the first and second gas form a
gaseous mixture.
54. The method of claim 53 wherein the second gas comprises a gas
that is capable of reacting with the first gas, when the first
plasma is generated in the tube.
55. The method of claim 53 wherein the second gas is added before
the first gas flows through the first cell.
56. The method of claim 55 wherein the gaseous mixture is
pre-treated prior to flowing the gaseous mixture through the first
cell.
57. The method of claim 53 additionally comprising analyzing the
composition of the first treated gas.
58. The method of claim 53 wherein the second gas is added to the
first gas between the first electrode and the second electrode.
59. The method of claim 46 additionally comprising analyzing the
gas composition of the first treated gas.
60. The method of claim 46 wherein energizing the first cell
comprises activating a first AC power supply.
61. The method of claim 60 wherein activating the first power
supply comprises controlling the first power supply employing one
or more techniques selected from the group consisting of analyzing
the first treated gas, determining gas pressure inside the tube and
determining tube temperature.
62. The method of claim 59 wherein the first power supply comprises
a switched mode resonant high voltage power supply.
63. The method of claim 59 wherein the first power supply
comprises: a) a DC power supply; b) a capacitor in parallel with
the DC power supply; and c) electrical components connected in
series including: (1) an inductor, (2) a primary winding of a
transformer and (3) a MOSFET switch having a snubber capacitor in
parallel with the switch and wherein the series is in parallel with
the DC power supply.
64. The method of claim 46 additionally comprising: a) energizing a
second DBD cell including (1) the tube, (2) a third electrically
conductive electrode positioned on the outside surface of the tube
and encircling the tube and (3) a fourth electrically conductive
electrode positioned on the outside of the tube, wherein the third
and fourth electrodes are in a side-by-side position; b) flowing
the first treated gas through the inside of the tube positioned at
the second DBD cell; c) generating a second plasma in the first
treated gas through dielectric barrier discharge inside the second
cell, wherein a second treated gas is formed.
65. The method of claim 64 wherein energizing the second cell
comprises activating a second AC power supply.
66. The method of claim 65 wherein the first and second AC power
supplies are controlled independently.
67. The method of claim 64 wherein the first and second DBD cells
are energized independently of each other.
68. The method of claim 64 additionally comprising analyzing a
composition of the first treated gas prior to introducing the first
treated gas into the second DBD cell, thereby obtaining first
analytical results.
69. The method of claim 68 wherein generating the second plasma
comprises controlling the second plasma employing the analytical
results.
70. The method of claim 69, additionally comprising introducing a
third gas between the first and second cells.
71. The method of claim 46 additionally comprising: a) flowing the
first gas through a first vacuum pumping stage before flowing the
gas through the tube; and b) flowing the first treated gas through
a second vacuum pumping stage, wherein the first and second pumping
stages are integrated with the first cell.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to methods and devices for
dielectric barrier discharge plasma treatment of processing
gases.
BACKGROUND OF THE INVENTION
[0002] Semiconductor fabrication techniques employ a variety of
gases for such processes as thin film deposition, etching, surface
preparation and chamber cleaning. Additionally, gases can be formed
as by-products of these fabrication techniques. Many process and
by-product gases are toxic, corrosive or combustible. Consequently,
semiconductor fabrication techniques typically require treatment of
effluent gases to remove noxious substances. Conventional treatment
techniques include wet and dry scrubbing, and treatment in an
oxidizing or reducing environment usually followed by wet or dry
scrubbing. Fluorine-containing compounds are present in many
semiconductor processing effluent gases. Conventional abatement
techniques for fluorine gases include incineration of these gases
followed by wet or dry scrubbing. It is well known to those of
ordinary skill in the art that these incineration techniques are
inefficient and result in generating much waste heat.
[0003] Also, it is known to use thermal and non-thermal plasmas for
treating hazardous gases, such as fluorine-containing compounds, in
order to convert these gases to environmentally safe products, see
for example PCT International Application Publication WO 99/26726.
In this publication, Shiloh et al. disclose the use of DBD
(dielectric barrier discharge) non-thermal plasmas for pollution
abatement. DBD technology employs DBD cells each having two
electrodes, wherein one or both electrodes of each cell is provided
with an insulator. Each DBD cell is energized by means of a high
frequency alternating current electrical power supply. The high
frequency energy is discharged capacitatively through the
insulator, forming a plasma discharge between the electrodes.
Shiloh et al. disclose a variety of DBD cell configurations,
exemplified herein as FIGS. 1 through 5. As schematically
illustrated in FIG. 1, an illustrative DBD cell includes
electrically conductive electrodes 30 and 32. Insulator dielectric
layers 34 and 36 are provided to electrodes 30 and 32 respectively,
such that the dielectric layers are interposed between the
electrodes. Suitable dielectric materials include alumina and
quartz. A high frequency electrical power supply 38 is connected to
electrodes 30 and 32.
[0004] A gas stream is caused to flow between dielectric layers 34
and 36 of the DBD cell depicted in FIG. 1, entering for example at
gas inlet 39 and exiting at gas outlet 40. High frequency power
supply 38 is activated, forming a plasma discharge between
electrodes 30 and 32 wherein the energy is capacitatively
discharged through dielectric layers 34 and 36. The plasma
activates the gas molecules causing dissociation, ionization or
free radical formation which is utilized to for example convert
noxious gaseous compounds into environmentally friendly compounds
or into compounds which can be more easily removed through the use
of conventional scrubber technology. Also, a reactive gas such as
oxygen or hydrogen can be introduced into the cell, for example at
gas inlet 39, to react with compounds in the plasma environment.
Cells, such as the cell shown in FIG. 1, can be utilized in series
by causing the gas stream to flow through two or more consecutive
cells to provide a more effective gas treatment system.
[0005] Alternative DBD cell configurations are illustrated in FIGS.
2-5. The cell depicted in FIG. 2 includes electrically conductive
electrodes 42 and 44. A dielectric layer 46 is provided to
electrode 42 such that layer 46 is interposed between the
electrodes. FIG. 3 illustrates a cell having curved electrodes 50
and 52 that are positioned on opposite sides on the outside of a
dielectric tube 54. The cell shown in FIG. 4 includes a cylindrical
electrode 56 and a conductive wire electrode 58. A dielectric layer
60 is provided to the inside of cylindrical electrode 56. The cell
illustrated in FIG. 5 includes concentric cylinder-shaped
electrodes 62 and 64. Dielectric layers 66 and 68 are provided to
the inside of electrode 62 and to the outside of electrode 64
respectively. A plasma is generated by the electrodes of the cells
shown in FIGS. 2-5 employing a technology similar to that described
in connection with FIG. 1.
[0006] Within each of the prior art cells shown in FIGS. 1-5, the
electrodes are placed in opposing positions. At least one of the
electrodes of each cell is provided with a dielectric layer facing
the opposing electrode. The electrodes and the dielectric layer(s)
are positioned substantially parallel to the gas stream.
[0007] Shiloh et al. disclose high frequency power supplies for use
with cells such as those exemplified in FIGS. 1-5, and control
techniques wherein sensors indicating for example gas composition
or temperature can be employed to monitor or control the DBD
abatement process.
[0008] It is also known to use a RF (radio frequency) plasma source
for fluorocarbon abatement of semiconductor fabrication processes,
see for example Vartanian et al., Long-Term Evaluation of the
Litmas "Blue" Plasma Device for Point-of-Use (POU)
Perfluorocompound and Hydrofluorocarbon Abatement, Technology
Transfer # 99123865A-ENG, International SEMATECH, pp. 1-50, Jan. 7,
2000. The device disclosed by Vartanian et al. includes a
dielectric tube, such as alumina, surrounded by RF excitation
coils. A variable frequency power supply is employed for generating
a high density RF plasma that is contained inside the dielectric
tube.
[0009] Gas mixtures that are discharged from semiconductor
processing or fabricating devices or equipment, such as etch
chambers, can rapidly change in flow rate and pressure. For
example, pressure variations from 100 mTorr up to about 1500 mTorr
and gas flow rate variations from tens to hundreds sccm (standard
cubic centimeters per minute) can occur within seconds and can be
repeated every few minutes. Conventional abatement techniques have
generally tried to meet the need for responding to these rapid
changes by operating the abatement technique such that it will
provide satisfactory abatement under the anticipated highest levels
and amounts of noxious compounds, generally resulting in wasted
resources and development of waste heat due to unnecessary high
treatment levels when relatively low levels of noxious compounds
are present.
[0010] The abatement methods and devices disclosed by Shiloh et al.
in publication WO 99/26726 were found to be quite effective.
However, experience with these methods and devices showed the need
for improvements. The needed improvements include improved
efficiency, reduced heat development, improved gas flow through the
cell and reduced operating costs, as well as improved integration
with semiconductor fabricating devices or tools and pump
systems.
[0011] The abatement methods and devices disclosed by Vartanian et
al. utilize RF plasma technology. Compared with DBD technology, RF
technology generates more waste heat. Also, the higher operating
temperature of RF systems is more likely to introduce thermally
caused stresses in the dielectric tube than is likely to occur in
DBD systems.
SUMMARY OF THE INVENTION
[0012] The present invention provides novel devices, techniques and
processes for plasma treatment of processing gases that overcome
the prior art problems described above.
[0013] In one embodiment of the present invention a DBD cell is
provided wherein a pair of ring shaped electrodes are positioned
side-by-side on a dielectric tube.
[0014] In another embodiment of the present invention a DBD cell
having ring shaped electrodes that are positioned side-by-side on a
dielectric tube, is provided with one or more sensors for
determining temperature or chemical composition of a gas present in
the cell.
[0015] In another embodiment of the present invention a DBD reactor
including several DBD cells is provided. Each of the cells includes
a pair of ring shaped electrodes that are positioned side-by-side
on the same dielectric tube.
[0016] In another embodiment of the present invention a DBD
treatment device is provided including a DBD cell having ring
shaped electrodes that are positioned side-by-side on a dielectric
tube. Additionally, an AC power supply is provided for energizing
the DBD cell. Noxious gas abatement methods are also provided.
[0017] In another embodiment of the present invention a DBD
treatment device is provided including a DBD reactor having several
DBD cells. Each of the cells includes a pair of ring shaped
electrodes that are positioned side-by-side on the same dielectric
tube. Additionally, an AC power supply is provided for each of the
cells. Furthermore, at least one sensor and controller are provided
for measuring the composition or temperature inside the tube and
for automatically adjusting the power supply for meeting
pre-defined gas processing conditions. Gas abatement methods are
also provided.
[0018] In another embodiment of the present invention a
semiconductor processing system is provided including a DBD cell
having ring-shaped electrodes that are positioned side-by-side on a
dielectric tube. Additionally, an AC power supply is provided for
energizing the cell. The cell is operably connected to the gas
discharge system of a semiconductor fabricating device. Gas
abatement methods for treating gas discharged from the fabricating
system are also provided, including the use of controllers to
integrate operation of the cell with the operation of the
fabricating device.
[0019] In another embodiment of the present invention a pump
integrated DBD treatment apparatus is formed. The apparatus
includes novel DBD cells or DBD treatment devices each having at
least one pair of ring shaped electrodes that are positioned
side-by-side on the same dielectric tube. These DBD cells or
treatment devices are integrated with vacuum pump stages.
[0020] In another embodiment of the present invention DBD devices
having one or more DBD cells, each including a pair of ring shaped
electrodes that are positioned side-by-side on the same dielectric
tube, are utilized to form fluorine species for use in chemical
processing methods, techniques and devices including wafer
fabricating devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is a schematic axial cross section view illustrating
a prior art DBD cell.
[0022] FIG. 2 is a schematic axial cross section view illustrating
another prior art DBD cell.
[0023] FIG. 3 is a schematic cross section view illustrating yet
another prior art DBD cell.
[0024] FIG. 4 is a schematic cross section view illustrating still
another prior art DBD cell.
[0025] FIG. 5 is a schematic cross section view illustrating
another prior art DBD cell.
[0026] FIG. 6 is a schematic perspective view illustrating a DBD
cell of the present invention.
[0027] FIG. 7 is a schematic cross section view of one of the
electrodes of the DBD cell illustrated in FIG. 6.
[0028] FIG. 8 is a schematic axial cross section view showing the
DBD cell illustrated in FIG. 6.
[0029] FIG. 9 is a schematic perspective view illustrating another
DBD cell of the present invention.
[0030] FIG. 10 is a schematic cross sectional view showing one of
the electrodes of the cell illustrated in FIG. 9.
[0031] FIG. 11 is a schematic cross sectional view showing another
DBD cell of the present invention.
[0032] FIG. 12 is a schematic plan view of the cell illustrated in
FIG. 11.
[0033] FIG. 13 is a schematic exploded perspective view showing
another DBD electrode of the present invention.
[0034] FIG. 14 is a schematic view showing a DBD treatment device
of the present invention, including a schematic axial cross section
view showing a DBD cell of the present invention.
[0035] FIG. 15 is a schematic view showing another DBD treatment
device of the present invention.
[0036] FIG. 16 is a schematic view showing another DBD treatment
device of the present invention.
[0037] FIG. 17 is a schematic axial view showing another DBD cell
of the present invention.
[0038] FIG. 18 is a perspective view showing a DBD reactor of the
present invention.
[0039] FIG. 19 is a schematic view showing a DBD treatment device
of the present invention, including a schematic axial cross section
view showing a DBD reactor of the present invention.
[0040] FIG. 20 is a schematic view showing another DBD treatment
device of the present invention, including a schematic axial cross
section view showing a DBD reactor of the present invention.
[0041] FIG. 21 is a schematic view showing a controller for
controlling a high frequency power supply of a DBD treatment device
of the present invention.
[0042] FIG. 22 is a schematic view showing a wafer fabricating
system of the present invention.
[0043] FIG. 23 is a schematic view showing another wafer
fabricating system of the present invention.
[0044] FIG. 24 is a schematic view illustrating a pump integrated
DBD treatment apparatus of the present invention.
[0045] FIG. 25 is a flow chart illustrating a method of the present
invention for treating gases that are discharged from a
process.
[0046] FIG. 26 is a schematic view showing a system of the present
invention for generating active fluorine species.
DETAILED DESCRIPTION OF THE INVENTION
[0047] While describing the invention and its embodiments, certain
terminology will be utilized for the sake of clarity. It is
intended that such terminology include the recited embodiments as
well as all equivalents.
[0048] One embodiment of the invention, schematically illustrated
in FIGS. 6 and 8, shows a novel DBD (dielectric barrier discharge)
cell 100 including ring shaped electrodes 110 and 112, and a
substantially cylindrical dielectric tube 114. Electrodes 110 and
112 preferably include electrical contact formations 116 and 118
respectively for receiving an electrical connector. Examples of
suitable electrical contact formations includes female plugs, male
plugs, threaded connections and fasteners, clamping surfaces, and
solder, welding or brazing surfaces. A schematic cross section view
of electrode 110 and dielectric tube 114 is shown in FIG. 7.
[0049] Dielectric tube 114, shown in FIGS. 6-8, is made of a
dielectric material such as alumina, quartz or sapphire. An example
of a suitable dielectric material includes non porous vacuum tight
alumina having a density of about 3.85 g/ml. Electrodes 110 and 112
are made of an electrically conductive material including metals
such as aluminum, copper and stainless steel. These electrodes have
a ring or cylindrical band shape, see for example electrode 110
shown in FIG. 7. Electrodes of DBD cells of the present invention
encircle the dielectric tube on which they are mounted in a
side-by-side position. Preferably, the distance between electrodes
110 and 112 is the shortest distance D (see FIG. 8) which does not
result in arcing between these electrodes when the electrodes are
activated by a suitable power supply. Typically, distance D ranges
from about 10 mm to about 30 mm. A preferred distance D is about 15
mm. Distance D is defined as the distance between the opposing
surfaces of the electrodes of a DBD cell. Width W of electrode 110,
see FIG. 8, typically ranges from about 20 mm to about 40 mm. A
preferred width is 27 mm.
[0050] Typically, electrodes 110 and 112 are slidably fitted on
tube 114, preferably providing a slight gap 120 and 122, see FIGS.
7 and 8, between the outside of tube 114 and the inside of
electrodes 110 and 112 respectively. This gap allows for
differences in thermal expansion or contraction between the tube
and the electrodes. Preferably, the gap between the tube and
electrode is filled with a sealing paste to substantially exclude
air from the gap between the electrode and the tube since an air
gap can result in reduced plasma efficiency or sparking of the
electrode due to a coupling capacitance that is too low in the air
gap. The gap between the inside of the electrode and the outside of
the dielectric tube should be as narrow as possible while still
allowing for differences in thermal expansion or contraction
between the tube and the electrode. Preferably, the gap should be
narrower than 1 mm. Suitable gap sealing pastes include
electrically insulating silicone based and polytetrafluoroethylene
based pastes, such as FOMBLIN.RTM. grease RT-15 available from
Ausimont located in Morristown, N.J. Grease RT-15 includes a
mixture of perfluoropolyethers and polytetrafluoroethylene.
[0051] An alternative embodiment of the present invention is
schematically depicted in FIG. 9, showing a novel DBD cell 200
including a dielectric tube 210 and novel DBD electrodes 212 and
214 encircling tube 210. Electrodes 212 and 214 are positioned
side-by-side. Each of these cells includes two electrically
conductive segments, each having a half ring shape. Electrode 212
includes segments 216 and 218 as depicted in FIGS. 9 and 10.
Similarly, electrode 214 includes half ring segments 220 and 222.
The two segments of each electrode are removable fastened to each
other using fasteners, for example bolts, such as bolts 224 and 226
of electrode 212 shown in FIGS. 9 and 10. Bolt 224 extends through
a hole 228 in segment 218. This bolt is threadably fastened to
segment 216. Similarly bolt 226 is threadably fastened to segment
218. The two electrode segments, when fastened together, form a
ring or cylindrical band shaped single electrode encircling
dielectric tube 210. Preferably, at least one bolt of each pair of
bolts used in the assembly of each electrode, is made of metal in
order to form a high conductivity electrical connection between the
two segments of each electrode.
[0052] Electrodes 212 and 214 are preferably provided with
electrical contact formations 228 and 230 respectively (see FIG.
9), similar to the corresponding contact formations of DBD cell 100
depicted in FIG. 6. Preferably, a slight gap is provided between
the inside of electrodes 212 and 214, and the outside of dielectric
tube 210 of novel DBD cell 200. These gaps are similar to gaps 120
and 122 of electrodes 110 and 120 respectively of novel DBD cell
100, as shown in FIGS. 7 and 8.
[0053] Preferably, novel electrode segments such as those described
in connection with novel DBD cell 200, shown in FIGS. 9 and 10,
employ a biasing element, such as a spring, in conjunction with
each fastener in order to urge the electrode segments together in a
spring-like manner. For example, a biasing element, such as a
compression spring (not shown) or one or more washers (not shown)
including lock washers providing a compression spring bias, can be
employed in conjunction with bolts 224 and 226, (FIG. 10) in order
to urge electrode segments 216 and 218 together to form electrode
212, using techniques and devices that are well known to those of
ordinary skill in the art.
[0054] As depicted in FIGS. 9 and 10, electrodes can be formed by
attaching two electrode segments to each other by means of bolts.
However, it is also contemplated to employ other attachment means
such as exemplified in FIG. 11, showing a schematic cross sectional
view of novel DBD electrode 300 including electrode segments 310
and 312. Clamps 314 and 316 of electrode 300 are the fasteners for
attaching electrode segment 310 to segment 312. Clamp 314 provides
a clamping force to portions 320 and 322 of segments 310 and 312
respectively, see FIG. 12 depicting a plan view of electrode 300. A
similar clamping force is provided by clamp 316. Suitable clamps
include clamps commonly referred to as C-clamps, as well as clamps
providing a spring action in addition to a clamping force, such
that the spring action urges the electrode segments together. A
spring action clamp thus provides a biasing element as well as a
fastener. Preferably at least one of the clamps of each DBD
electrode is made of metal in order to form a high conductivity
electrical connection between the two segments of the
electrode.
[0055] Additionally, it is preferable to provide one or more heat
sinks to each DBD electrode, or to its DBD electrode segments as
schematically illustrated in connection with novel DBD electrode
400 shown in FIG. 13. Electrode segment 410 includes heat sink
elements 412, 414, 416 and 418 extending radially. Similarly,
electrode segment 420 includes heat sink elements 422 and 424, 426
and 428. Preferably, the heat sink elements are integral with the
segment. Alternatively, the heat sink elements can be separate
components that are attached to the electrode segment. Preferably,
the heat sinks are made from highly heat conductive materials, such
as metals. These heat sinks are utilized to dissipate heat from the
dielectric tube and the DBD electrode, typically by exposure to
cooling air. Holes 430 and 432 (FIG. 13) are provided to bolt (not
shown) the cell segments together, similar to the techniques
described in connection with novel DBD electrode 212 depicted in
FIGS. 9 and 10. The configuration of electrode 400 was empirically
found to be a preferred configuration for optimized abatement. The
improvements that are realized with configurations such as
exemplified in electrode 400 are believed to be due to what is
known as a "hollow cathode effect", wherein plasma density is
enhanced inside a hollow cathode. Heat sink element 416 of
electrode segment 410 preferably includes an electrical contact
formation 436 (FIG. 13) similar to formation 116 of electrode 110
(FIGS. 6 and 7). It will be understood that heat sink elements
shaped as rods or bars are also operable for providing heat
exchange surfaces for electrodes of the present invention.
[0056] The novel segmented DBD electrodes described in connection
with FIGS. 9-13 were found to be an improvement over the
cylindrical electrodes described in connection with FIGS. 7-8
because the segmented electrodes facilitate the removal or
replacement of the electrodes, or changing the distance between
electrodes. Also, the segmented electrodes are generally better
adapted for providing a predetermined fit or a gap with the outside
of the dielectric tube since the segmented electrodes do not need
to slide or move on the reactor tube in order to be positioned
properly. Preferably, a sealing paste is applied in the space or
gap between the inside surface of the electrode segments and the
outside surface of the dielectric tube in a manner similar to that
described in connection with gap 120 of electrode 110 depicted in
FIGS. 7 and 8.
[0057] Advantageously, novel segmented electrodes employing biasing
elements such as described in connection with electrodes 212 (FIG.
10) and 300 (FIG. 11) allow a closer fit between the inside of the
DBD electrode and the outside of the reactor tube, since the
biasing element can be adapted for urging the electrode segments
together such that the biasing element compensates for differences
in thermal expansion or contraction between the reactor tube and
the electrode. It will be understood that the fasteners and biasing
elements described in connection with the embodiments of the
present invention are merely illustrative and that other fasteners
and biasing elements can be employed, using such fasteners and
biasing elements as are well known to those of ordinary skill in
the art. Also, it will be understood that the segments forming an
electrode need a high electrical conductivity connection between
them and that it is necessary to provide such a connection if the
fasteners are non-conductors.
[0058] Embodiments of the present invention exemplified in FIGS. 6
through 13 utilize ring shaped electrodes encircling a dielectric
tube wherein the electrodes are constructed as rings or segmented
rings. Operable ring or cylindrical band shaped electrodes also
include conductive foil, such as metal foil, wrapped around the
tube such that a foil ring or cylindrical band is formed having a
thickness of one or more layers of foil. Operable ring or
cylindrical band shaped electrodes also include electrodes that are
applied as an electrically conductive layer on the outside of the
dielectric tube, forming a ring or cylindrical band, using for
example electrically conductive paint or paste compositions such as
are well known to those of ordinary skill in the art.
[0059] Another embodiment of the present invention illustrated in
FIG. 14, depicts a DBD cell 500 including electrodes 512 and 514,
and dielectric tube 516. Examples of suitable cells include
previously described cell 100 (FIGS. 6 and 8) and cell 200 (FIG. 9)
using electrodes such as electrodes 110 (FIG. 7), 212 (FIG. 10),
300 (FIGS. 11 and 12) and 400 (FIG. 13). Returning to FIG. 14,
electrodes 512 and 514 are electrically connected to a high
frequency AC (alternating current) power supply 518. Suitable
examples of power supply 518 will be described in more detail in
connection with power supplies 610 and 710 of DBD plasma treatment
devices 600 and 700 respectively, shown in FIGS. 15 and 16.
Electrical connectors 520 and 522 (FIG. 14), using for example
conductive wiring, connect power supply 518 to electrodes 512 and
514 respectively, employing for example electrical contact
formations (not shown) of each of the electrodes to provide the
electrically conductive connection. The combination of DBD cell
500, power supply 518 and connectors 520 and 522 forms a novel DBD
treatment device 540.
[0060] A gas stream requiring treatment, for example for removal of
noxious substances, flows through cell 500 (FIG. 14) in the
direction indicated by arrows 524 and 526. The gas stream enters
cell 500 at a gas inlet 528 and is discharged from the cell at a
gas outlet 530. A plasma is formed in the gas stream that flows
through cell 500 when the cell is energized by activating power
supply 518. It is believed that DBD cells of the present invention
induce a coupling effect and that the plasma is formed in the gas
within the region of the cathode electrode as well as in the region
of the anode. The high frequency AC applied to electrodes 512 and
514 causes each of these electrodes to alternate the anode and
cathode polarity, while maintaining a plasma in zones 532 and 534,
as schematically shown in FIG. 14. The plasma conditions formed in
novel cell 500 of novel DBD treatment device 540 are effective for
decomposing FCs (fluorocarbons) and for reacting FC with gases such
as O.sub.2 and H.sub.2O vapor, or mixtures of gases such as
CH.sub.2+O.sub.2 or H.sub.2+O.sub.2. Device 540 was found to be
effective for abatement of FCs typically present in gases that are
discharged from semiconductor processing devices, such as etch
chambers, including fluorine containing by-product gases formed in
semiconductor processing devices. These FCs can include CF.sub.4,
CHF.sub.3, CH.sub.2F.sub.2, C.sub.2F.sub.6, C.sub.4F.sub.8 and
C.sub.4F.sub.6. A controller (not shown) can be employed in
connection with power supply 518 of DBD treatment device 540,
similar to controllers discussed in connection with DBD treatment
device 1100 (FIG. 20). Optionally, one or more sensors (not shown)
or gas addition ports (not shown) can be provided for device 540
(FIG. 14), and these can be integrated with the power supply
controller as discussed in connection with DBD treatment device
1100.
[0061] Novel DBD treatment device 600, schematically illustrated in
FIG. 15, includes a high frequency AC power supply 610, and DBD
cell 612. Power supply 610 is similar to the switching mode
resonant power supply disclosed by Shiloh et al. in publication WO
99/26726. Cell 612 is similar to novel DBD cell 500 described in
connection with FIG. 14. Returning to FIG. 15, power supply 610
includes a DC power source 614 in series with a switch 616, a
variable inductance 618 and primary winding 620 of a transformer
621. A capacitor 622 is positioned in parallel with the DC power
source and in parallel with the series including the switch, the
variable inductance and the primary winding. Secondary winding 624
of the transformer provides the output AC current of power supply
610 to DBD cell 612.
[0062] As shown in FIG. 15, the plasma in DBD cell 612 is
schematically represented by an equivalent circuit including a
capacitance 626, in parallel with a resistance 628. Inductance 626
represents the plasma reactive impedance, while resistance 628
represents the part of the plasma impedance leading to power flow
into the plasma. The capacitance of the wall of the dielectric tube
is schematically shown as 630 and 632. Similarly, the sheath
capacitance of the plasma is depicted as 634 and 636. In operation,
switch 616 is opened and closed at a high frequency. A high AC
voltage is developed across the cell when the switching frequency
of switch 616 is equal to the resonant frequency of the cell
capacitance including the capacitances 630, 634, 632 and 636 with
the parasitic inductance of primary transformer winding 620
combined with variable inductance 618. Power supply 610 typically
operates at frequencies ranging from about 10 kilohertz to about 3
megahertz, utilizing for example a MOSFET (metal oxide
semiconductor field effect transistor) switch 616. Secondary
winding 624 typically supplies a peak voltage ranging from about
300 volts to about 100 kilovolts. DBD treatment device 600 provides
FC abatement similar to that described in connection with device
540 depicted in FIG. 14.
[0063] A preferred embodiment of a DBD treatment device 700 of the
present invention is illustrated in FIG. 16. This device includes a
novel switched mode, resonant high voltage power supply, SMPD
(self-matched plasma device) 710 and a DBD cell 712 similar to cell
612 of device 600 shown in FIG. 15. Returning to FIG. 16, SMPD 710
includes a DC power supply 714, providing a DC voltage input
preferably ranging from about 30V to about 48V. SMPD 710 further
includes a low ESR (equivalent series restriction) capacitor 716,
an inductance 718, a MOSFET switch 720 preferably 600 W/500V, a
snubber capacitor 722 and a transformer 724. Typically, transformer
724 includes a primary to secondary ratio of about 1 to about 20.
The drain to source voltage at MOSFET switch 720 typically rises up
to 300V at the opening phase. Preferably, the primary current
ranges from 20 A to about 30 A while the secondary current is about
1 A. The switching frequency is about 900 kHz. A preferred peak
voltage between the electrically floating electrodes of DBD cell
712 is about 3KV. As shown in FIG. 16, power supply 710 includes a
DC power supply section 730 and a high voltage AC power supply
section 732.
[0064] The energy of SMPD 710 (FIG. 16) resonates between the
capacitance load and the inductance of the driving circuit.
Operating MOSFET switch 720 in the proper frequency range pushes
the energy in the resonant mode. The load capacitance due to
operation of DBD cell 712 is a function of the electrode-to-plasma
capacitance, that is mainly the capacitance of the cell's
dielectric tube, in series with the plasma sheath capacitance,
typically a few tens pF. Some parasitic capacitance from the
electrode structure, SMPD wiring and the transformer is added in
parallel to the load capacitance. The voltage at the electrodes
rises resonantly until ignition of the plasma. Following plasma
ignition, the resonance broadens due to resistive loading of the
plasma. Consequently, specific tuning is generally not necessary.
SMPD 710 is capable of igniting a plasma and maintaining it at
various gas compositions and flow rates using the same frequency,
and operating at pressures ranging between 10 mTorr and 10
Torr.
[0065] Preferably, DC power supplies such as 614 (FIG. 15) and 714
(FIG. 16) include constant DC power supplies. Examples of suitable,
well known, constant DC power supplies include DC power supplies
delivering a constant voltage and DC power supplies delivering a
constant current.
[0066] It is highly desirable to deliver a constant power into the
plasma. However, the load impedance of the plasma is not constant
due to varying conditions of the gas. These load variations are
manifested at the input of the high voltage power supply as load
impedance variations for the DC power supply. The use of a constant
voltage or a constant current DC power supply therefore requires
stabilization of the power flow into the plasma to obtain a
substantially constant value through dynamic control of the pulse
width that drives the high voltage power supply. This dynamic
control was found to be complicated to achieve and not very
efficient for striking and maintaining an effective plasma in DBD
reactors of the present invention. In preferred embodiments of DBD
treatment devices of the present invention, such as device 600
(FIG. 15) and device 700 (FIG. 16) it was discovered that constant
power DC power supplies alleviated the technical problems
associated with the use of constant voltage and constant current D
power supplies. A constant power DC power supply (not shown) was
prepared by modifying a conventional voltage regulated power supply
(not shown) in the following manner. The voltage output V and
current output I were measured. An electronic multiplier was
utilized to produce a voltage proportional to V times I, which was
compared to a pre-set value. The output of the comparator was then
used to control the output of voltage of the power supply in order
to thereby obtain a constant power flow into the plasma.
[0067] FIG. 17, depicting DBD cell 800, illustrates another
embodiment of the present invention. Novel DBD cell 800 includes
electrodes 810 and 812, and dielectric tube 814. Examples of
suitable electrodes for electrodes 810 and 812 include electrodes
110 (FIG. 7), 212 (FIG. 10), 300 (FIGS. 11 and 12) and 400 (FIG.
13), while suitable tubes for dielectric tube 814 of novel DBD cell
800 include tube 114 of novel DBD cell 100 (FIGS. 6-8), tube 210 of
novel DBD cell 200 (FIG. 9) and tube 516 of novel DBD cell 500
(FIG. 14). Returning to FIG. 17, cell 800 is provided with a port
816 for adding gases to the gas stream flowing through the cell in
the direction shown by arrows 818 and 820. Additionally, cell 800
includes a sensor or probe 822 for determining gas pressure, or for
analyzing or determining the gas composition using for example
Langmuir probes, laser induced fluorescence, mass spectrometry,
FTIR spectroscopy, optical emission spectroscopy and such other
chemical and physical analytical or diagnostic procedures and
techniques as are well known to those of ordinary skill in the art.
It is also contemplated to utilize novel DBD cells (not shown)
having either a port for introducing gases or a sensor for
determining gas composition, or having several gas introduction
ports and/or several sensors. Additionally, it is contemplated to
provide one or more gas introduction ports positioned outside gas
inlet 824 of cell 800 and/or one or more sensors positioned outside
gas outlet 826, in place of or in addition to port 816 and sensor
822.
[0068] Optionally, cell 800, depicted in FIG. 17, can be provided
with a gas introduction port 817 that is positioned in tube 814
between electrodes 810 and 812. Ports and sensors that are
positioned outside cell 800 can be placed in a conduit (not shown)
that is operably connected to the cell. Optionally, an elbow shaped
conduit 830 can be operably connected to tube 814, causing the gas
stream to flow through this conduit. A window 832, for example made
of sapphire, can be mounted in the elbow section to provide, an
optical path into the interior of cell 800 in order to make optical
observations and measurement of a plasma (not shown) that is formed
in the cell. Optionally, a window (not shown) can be mounted in the
wall of tube 814 for optical observations and measurements.
Additionally, a contact probe such as a thermocouple (not shown)
can be positioned in thermally conductive contact with the outside
surface of tube 814 to measure tube temperature.
[0069] In another embodiment of the present invention depicted in
FIG. 18, a DBD reactor 900 is provided for abatement of noxious
gases. This reactor includes novel DBD cells 910, 912 and 914, and
dielectric reactor tube 916. DBD cells 910, 912 and 914 are similar
to novel DBD cell 200 shown in FIG. 9. DBD cell 910 includes
electrode segments 920 and 922 forming electrode 924, using one or
more fasteners 926, see FIG. 18. Electrode 924 preferably includes
an electrical contact formation 928. Similarly, electrode 928 of
DBD cell 910 includes electrode segments 930 and 932, fastener 934
and preferably contact formation 936. DBD cells 912 and 914 are
similar to cell 910, wherein cell 912 includes electrodes 938 and
940 while cell 914 includes electrodes 942 and 944.
[0070] The six electrodes of reactor 900 (FIG. 18) are placed in
side-by-side positions on reactor tube 916. Each of these cells
utilizes a different portion of tube 916 to provide the
dielectric's capacitance for forming a plasma upon activation of
the cells while a gas stream flows through tube 916. The
capacitance portion of reactor tube 916 with regard to each cell is
substantially the tube portion encircled by the electrodes and
additionally the tube portion between the electrodes of a cell.
Portions of reactor tube 916 that are located between adjacent DBD
cells are not components of the DBD cells of DBD reactor 900, thus
forming a series of individual cells that are connected by sections
of tube 916. Optionally, one or more ports (not shown) and/or one
or more sensors or probes can be provided to reactor 900. The one
or more ports can be provided in tube 916, similar to port 816 of
cell 800 (FIG. 17). Also, the one or more sensors can be positioned
in a similar manner as sensor 822 of cell 800. Additionally, it is
contemplated to place ports or sensors in one or more conduits (not
shown) that are operably connected to tube 916 of reactor 900 shown
in FIG. 18.
[0071] DBD treatment device 1000, depicted in FIG. 19, provides
another embodiment of the present invention. Device 1000, includes
a DBD reactor 1010, similar to DBD reactor 900 shown in FIG. 18,
and high frequency AC power supplies 1012, 1014 and 1016 as well as
electrical connectors 1018, 1020, 1022, 1024, 1026 and 1028 for
connecting the power supplies to the DBD cells of device 1000. The
electrical connectors can be connected to contact formations (not
shown) of the electrodes. Examples of suitable power supplies
include power supply 610 of DBD treatment device 600 (FIG. 15) and
power supply 710 of DBD treatment device 700 (FIG. 16). DBD reactor
1010 includes DBD cell 1030 having electrodes 1032 and 1034, DBD
cell 1036 having electrodes 1038 and 1040, DBD cell 1042 having
electrodes 1044 and 1046, and dielectric reactor tube 1047.
Typically, the inside diameter of dielectric tube 1047 ranges from
about 38 mm to about 51 mm. A preferred inside diameter is 51 mm.
The wall thickness of reactor tube 1047 should be as thin as
possible while providing sufficient mechanical strength for its
intended use. For example, an alumina tube wall thickness of about
4 mm to about 5 mm is generally suitable for many DBD reactor
applications. Plasmas similar to those formed in DBD treatment
device 540 (FIG. 14) are formed in device 1000 when cells 1030,
1036 and 1042 are activated by power supplies 1012, 1014 and 1016
respectively, when a gas is present in reactor tube 1047.
Preferably, DBD reactors of the present invention should be
operated in a closed environment wherein an air flow is employed to
provide effective cooling of the reactor.
[0072] Another embodiment of the present invention is illustrated
in FIG. 20, depicting DBD treatment device 1100 including novel DBD
reactor 1110. This reactor includes reactor tube 1111, novel DBD
cells 1112, 1114 and 1116, connected to high frequency AC power
supplies 1118, 1120 and 1122 respectively. Tube 1111, cells 1112,
1114 and 1116, and power supplies 1118, 1120 and 1122 are similar
to the corresponding components of DBD treatment device 1000 shown
in FIG. 19. One or more sensors or probes 1124 and 1126, similar to
sensor 822 of novel DBD cell 800 (FIG. 17) are positioned inside
reactor tube 1110 to measure for example gas pressure and/or gas
composition of the gas stream flowing through DBD reactor 1110 in
the direction indicated by arrows 1128 and 1130, as shown in FIG.
20. Additionally, a temperature measuring or indicating device 1131
such as a thermocouple can be positioned in thermally conductive
contact with the outside surface of tube 1110 using such methods,
techniques and devices as are know to those of ordinary skill in
the art, in order to measure the temperature of the dielectric
tube. Optionally, one or more ports (not shown) and/or one or more
additional sensors can be provided to DBD treatment device 1100 in
a similar manner as described in connection with reactor 900 (FIG.
18).
[0073] As illustrated schematically in FIG. 20, a controller 1132
is operably connected to sensor 1124 and to power supply 1118.
Similarly, a controller 1134 is operably connected to sensor 1126
and to power supply 1118. Additionally, a controller 1136 is
operably connected to sensor 1124 and to power supply 1120.
Examples of suitable controllers 1132, 1134 and 1136 include
conventional computers and computer systems including one or more
computers that are operably connected to other computers or to a
network of computers or date processing devices. Suitable computers
also include microprocessor based computers commonly known as
personal computers. While FIG. 20 shows three controllers, i.e.
1132, 1134 and 1136 it is also contemplated to use one computer
that provides the separate functions of controllers 1132, 1134 and
1136. Controller 1132 utilizes an output signal from sensor 1124 to
control power supply 1118. Similarly, controller 1134 adjusts,
controls or regulates power supply 1120 based on an output signal
from sensor 1126. Controller 1136 employs an output signal from
sensor 1124 to control power supply 1120.
[0074] Novel DBD treatment device 1000, shown in FIG. 19, and novel
DBD treatment device 1100, depicted in FIG. 20, each employ a
series of three DBD cells wherein each cell has a power supply.
Preferably, the three power supplies of each of these devices are
dedicated power supplies to provide individual control to each
cell, thus providing a reactor capability for individually
controlling the plasma conditions in each cell of the reactor. For
example, a gas stream containing noxious substances such as FCs
flowing through novel DBD reactor 1110 (FIG. 20) can be exposed to
plasmas (not shown) in cells 1112, 1114, 1116 operating such that
each plasma destroys, or reacts with, only a portion of the total
noxious gas content of the gas stream. However, the three plasmas
combined can provide a complete or nearly complete DRE (destruction
removal efficiency) while operating at a lower power level than a
single cell that achieves a similar DRE. The multi-cell reactor
typically operates at a lower temperature than a single cell,
thereby providing less thermal stress on the equipment and less
waste heat.
[0075] Advantageously, a multi-cell reactor of the present
invention employing individual power supplies provides a modular
reactor having the capability to selectively treat different gases
in the gas stream by one or more specific cells. This selective
treatment can include introducing a reactive gas in the reactor
itself or upstream of the reactor. For example, a reactive gas or
gas mixture can be introduced in a conduit (not shown) operably
attached to the gas inlet of the reactor tube such that the gas
introduction port is positioned at a distance of approximately 500
cm from the gas inlet of the reactor tube. Typically, the reactive
gas is effectively mixed with the gas that needs to be treated in
the reactor when the gases flow together over a distance of
approximately 500 cm. However, it is also contemplated to mix gases
prior to plasma treatment by utilizing static or dynamic mixing
elements such as are known to those of ordinary skill in the art.
Alternatively gas mixture can be pre-treated such as heated or
subjected to DBD plasma treatment prior to treatment in a DBD
reactor of the present invention.
[0076] The DRE can be monitored at different cells in a multi-cell
reactor using a variety of sensors such as sensors 1124 and 1126 of
novel DBD treatment device 1100, shown in FIG. 20. Output from a
sensor can be utilized to control the power supply of the relevant
cell. Preferably, sensor output is utilized to automatically
control the power supply of the relevant cell in order to provide
rapid noxious gas abatement responses when there are rapid changes
in the noxious gas stream. For example, DBD treatment device 1100,
depicted in FIG. 20, utilizes controller 1132 to control power
supply 1118 of DBD cell 1112. Controller 1132 is programmed to
receive the output signal from sensor 1124 and to compare this
signal with a pre-determined signal value range indicating a
desirable or design DRE. The controller then causes the necessary
adjustments to be made in the operation of power supply 1118 if the
output signal is not in the pre-determined value range. Similarly,
controller 1136 can be utilized to control power supply 1120 of DBD
cell 1114 in order to affect the abatement efficiency of cell 1114
as a function of the gas stream properties/composition as analyzed
by sensor 1124. A similar control loop (not shown) can be provided
between a sensor and a gas flow rate controller (not shown) that
controls the flow of an additive gas, such as for example O.sub.2
or CH.sub.4+O.sub.2. Control of the independently controlled power
supplies of the cells of treatment device 1100 can thus be achieved
through the techniques for gas analysis or gas pressure measurement
at various points in the reactor tube and also by determining the
temperature of the outside surface of the reaction tube. These
analytical techniques and the pressure and temperature
determinations can thus be utilized to control the operation of
each independently controlled DBD cell of the present invention.
Similarly, the addition of reactive gases to treatment device 1100
can be controlled through these analytical, pressure and
temperature measuring techniques.
[0077] While DBD reactors 900 (FIG. 18), 1010 (FIG. 19) and 1110
(FIG. 20) of the present invention each include three DBD cells, it
will be understood that reactors including three DBD cells are
merely illustrative of the invention and that the present invention
is also operative for DBD reactors having two cells, or having more
than three DBD cells. For example, novel DBD reactors having six,
seven or eight cells, were found to be particularly effective for
abatement of fluorine compounds that are discharged from
semiconductor fabricating equipment, such as etch chambers.
[0078] FIG. 21 illustrates a technique for utilizing a controller,
such as controller 1132 of novel DBD treatment device 1100 (FIG.
20), to control an AC power supply 1214 such as power supply 1118
of device 1100. Returning to FIG. 21, sensor output 1210 is entered
into controller 1212. Controller 1212 compares the sensor output
with a pre-determined range of acceptable or design values. If the
sensor output is outside the pre-determined range, the controller
can cause high frequency AC power supply 1214 to be adjusted. For
example, an adjustment 1216 can be made in the DC power of DC power
supply section 1218 of high frequency AC power supply 1214.
Alternatively, controller 1212 can be utilized to make an
adjustment 1220 in either the frequency or the pulse width of AC
power supply section 1222 of high frequency AC power supply 1214.
These adjustments are then employed to adjust and control the
plasma (not shown) that is generated in DBD cell 1224 of the
present invention. Examples of suitable high frequency AC power
supplies for use with controller 1212 include power supply 610 of
novel DBD treatment device 600 (FIG. 15) and power supply 710 of
novel DBD treatment device 700 (FIG. 16).
[0079] Semiconductor or wafer processing system 1300, schematically
illustrated in FIG. 22, provides another embodiment of the present
invention. System 1300 includes a wafer or semiconductor
fabricating device or tool 1310, such as a wafer fabricating
chamber for example an etch chamber, a conventional first vacuum
pump 1312 such as a turbomolecular pump or a mechanical pump such
as a roughing/backing pump, a DBD treatment device of the present
invention 1314, a conventional second vacuum pump 1316 and a
conventional wet or dry scrubber 1318. These components are
operably connected as schematically depicted in FIG. 22. System
1300 can employ additional conventional components (not shown) such
as isolation valves, throttle valves, pressure gauges, temperature
gauges and one or more forelines for process control. Suitable
examples of DBD treatment device 1314 of the present invention
include device 540 (FIG. 14), 600 (FIG. 15), 700 (FIG. 16), 1000
(FIG. 19) and 1100 (FIG. 20). Alternatively, a semiconductor or
wafer processing system of the present invention can include a
semiconductor or wafer fabricating device, a DBD treatment device
of the present invention and a gas flow connection positioned
between the fabricating device and the dielectric tube of the DBD
device. Examples of suitable flow connections include a foreline,
one or more conduits, one or more pumps and one or more gas control
valves.
[0080] Returning to FIG. 22, pump 1312 is utilized to pump
processing gases from fabricating device 1310 to DBD treatment
device 1314 for PET (plasma exhaust treatment) to react or remove
gases such as FCs. The gases that are discharged from DBD treatment
device 1314 are pumped to scrubber 1318 by means of pump 1316.
Also, the invention is equally operable without first pump 1312
(FIG. 22), providing the gas flow conditions in DBD treatment
device 1314 are suitable for forming a plasma for treating the gas
that is discharged from fabricating device 1310.
[0081] Semiconductor or wafer processing system 1400, as
schematically illustrated in FIG. 23, provides another embodiment
of the present invention. System 1400 includes a semiconductor
fabricating device 1410, a first vacuum pump 1412, a DBD treatment
device of the present invention 1414, a second vacuum pump 1416 and
a scrubber 1418. These components are similar to the corresponding
components described in connection with semiconductor or wafer
processing system 1300, depicted in FIG. 22. Returning to FIG. 23,
processing system 1400 additionally includes a gas panel 1420 for
providing one or more gases for use in conjunction with DBD
treatment device 1414, using for example a conduit 1421, for
introducing one or more gases in the DBD treatment device.
Alternatively, one or more gases can be introduced through a
conduit 1423 to conduit 1425 positioned between vacuum pump 1412
and DBD treatment device 1414. This system also includes a
controller 1422, such as a computer, for controlling and
interacting with fabricating device 1410, DBD treatment device 1414
and gas panel 1420. Additionally, system 1400 includes an interlock
feature 1424 in connection with controller 1422 for interacting
with the DBD treatment device of system 1400, as shown in FIG. 23.
The interlock feature can for example be utilized to stop or
interrupt the plasma treatment if the gas pressure is below a
predetermined pressure, or if the temperature inside the dielectric
tube or the tube wall exceeds a pre-defined limit, or upon the
occurrence of any other pre-defined processing condition.
[0082] Controller 1422, shown in FIG. 23, receives status
information 1426 from fabricating device 1410 and information
concerning gas flow rates 1428 and gas composition of gases that
are discharged from device 1410. Additionally, controller 1422
receives status information 1430 from DBD treatment device 1414,
for example whether device 1414 is on or off. Also, controller 1422
receives information concerning gas flow rates 1432 of gases
flowing from gas panel 1420 to DBD device 1414. Controller 1422
processes the information described above and then in accordance
with programmed instructions, controller 1422 reports status
information 1434 regarding the abatement process to fabricating
device 1410. The controller also provides gas flow rate
instructions 1435 to the gas panel and provides shut down
instructions 1436 to DBD device 1414. Interlock feature 1424
provides shut down instructions 1438 to the DBD device upon the
occurrence of pre-determined processing events as determined by the
controller. Interlock feature 1424 can provide instructions 1439 to
one or more gas valves (not shown) of gas panel 1420 to close, for
example, the valve(s) upon the occurrence of pre-determined
processing events as determined by controller 1422. When starting a
processing run or cycle with DBD device 1428, controller 1422 can
be programmed to cause DBD device 1414 to be activated following a
pre-determined delay time interval 1440 that is initiated by the
computer program for starting discharge of processing gas from
fabricating device 1410. It will be understood that interlock
feature 1424 can be provided as a unit that is separate from
controller 1422, as illustrated in FIG. 23, as well as an interlock
feature that is a function of a controller, and is integral with
the controller (not shown).
[0083] DBD cells and reactors of the present invention provide
plasma treatment over a wide range of gas pressures inside the cell
or reactor tube, generally ranging from about 100 mTorr to about 10
Torr. A typical gas pressure inside the tube ranges from about 100
mTorr to about 1200 mTorr. Higher pressures, such as 10 Torr,
typically require a smaller tube diameter and/or a lower cell AC
frequency than very low pressures, in order to obtain effective
plasma coupling.
[0084] Preferably, DBD cells and DBD reactors of the present
invention, such as cells 100 (FIG. 6), 500 (FIG. 14), 800 (FIG.
17), and reactors 900 (FIG. 18), 1010 (FIG. 19) and 1110 (FIG. 20)
are provided with a cooling feature (not shown) to cause the
reactor tube and the electrodes to be cooled. A suitable cooling
feature includes a housing substantially enclosing the DBD cell or
reactor therein, and providing an air flow for contacting the tube
of the cell or reactor and the electrodes. This cooling feature can
be enhanced by cooling the air prior to entering into the enclosure
or by providing a heat exchanger inside the housing, using a
coolant such as water. Additionally, the cooling feature can be
adapted to provide an interlock (not shown) for switching the DBD
cell or reactor or the DBD treatment device off when, for example,
the temperature inside the housing exceeds a pre-defined
temperature, or when coolant is leaking from the heat
exchanger.
[0085] As described in connection with FIGS. 22 and 23, one or more
conventional vacuum pumps are typically used in conjunction with
DBD treatment devices of the present invention. In an alternative
wafer processing system (not shown), the novel DBD treatment device
can be positioned in a foreline between the wafer fabricating
device and the vacuum pump. An example of a pump suitable for
processing systems such as systems 1300 (FIG. 22) and 1400 (FIG.
23) includes an IPUP (integrated point of use pump). An IPUP (not
shown) typically includes a series of pump stages that is
integrated to form one vacuum pump. Integration of pump stages can
include (1) placement of the stages on a common support base, (2) a
common drive mechanism such as a single motor causing pumping
action in each of the stages and (3) common utilities such as
electrical power and coolant. An example of an IPUP is an ADP pump
available from ALCATEL, located in Annecy Cedex, France. The ADP
includes five Roots type vacuum pumping stages that are placed in
series on a common support base and sharing a common drive and
common utilities such as electrical power and cooling water.
[0086] In another embodiment of the present invention, novel DBD
treatment devices are integrated with the pumping stages of an ADP
pump, as depicted in FIG. 24, to form a novel pump integrated DBD
treatment apparatus 1500. As illustrated in FIG. 24, pump
integrated DBD treatment apparatus 1500 of the present invention
includes an inlet 1510, an outlet 1512, five Roots pumping stages
1520, 1522, 1524, 1526 and 1528, and three DBD treatment devices of
the present invention 1540, 1542 and 1544. Each of the Roots pump
stages includes two conventional lobe shaped rotors that rotate
without touching each other, such as rotors 530 and 532. Each stage
further includes conventional power and cooling sub-systems.
Optionally, integrated apparatus 1500 includes sensors 1550, 1552
and 1554, similar to sensors such as sensors 1124 and 1126 that are
described in connection with FIG. 20. Returning to FIG. 24, sensors
540, 542 and 544 can be positioned in the conduit between a DBD
treatment device and the adjacent Roots stage or in a DBD treatment
device itself (not shown). Inlet 1510 can communicate with a wafer
or semiconductor fabricating device or tool (not shown), such as
fabricating device 1310, shown in FIG. 22, for example through a
conventional foreline (not shown). Outlet 1512 (FIG. 23) can
discharge gases from apparatus 1500 to for example an additional
conventional vacuum pump (not shown) or to a conventional scrubber
(not shown). Pump stages 1520, 1522, 1524, 1526 and 1528 are
integrated through a common, or shared, support base, a common
drive mechanism and common utilities including electrical power and
cooling water.
[0087] When a gas is pumped at vacuum pressure through apparatus
1500 (FIG. 24), the pressure at DBD device 1544, is lower than the
pressure between stages 1526 and 1528. Similarly, the pressure at
DBD device 1542 is lower than at DBD device 1544, while the
pressure at DBD device 1540 is lower than the pressure at DBD
device 1542. Thus, each of the three DBD treatment devices of novel
pump integrated DBD treatment apparatus 1500 operates at a vacuum
pressure that is different from the other DBD devices of the same
pump integrated DBD treatment apparatus. In order to optimize the
plasma coupling of each of the three DBD treatment devices it is
highly desirable to operate the devices at different frequencies
such that a higher frequency is used at lower pressure. Also, for
the purpose of maximizing DBD plasma coupling it is highly
desirable to select a different reactor tube diameter for DBD
reactors in the three DBD devices such that a larger diameter tube
is used at lower pressure. For example, the frequency for the
plasma in DBD device 1540 should be higher than the frequency for
the plasma in DBD device 1542, while the reactor tube in DBD device
1540 should have a larger inside diameter than the reactor tube in
DBD device 1542. Sensors such as sensors 1550, 1552 and 1554 can be
employed to determine the vacuum pressure at each of the three DBD
devices, and to use the results of these pressure determinations
for optimizing the configuration, such as tube diameter, and/or the
operating parameters such as frequency. Alternatively, experimental
pressure determinations can be made without the use of permanently
installed sensors, in order to determine the optimal configuration
and/or operating parameters.
[0088] In other embodiments of the present invention it is also
contemplated to provide a pump integrated DBD treatment apparatus,
such as illustrated in FIG. 24, having four pumping stages in
series that are integrated with two DBD treatment devices as well
as a pump integrated DBD treatment apparatus having n pumping
stages in series that are integrated with n minus 2 DBD treatment
devices. In this context, n denotes the number of pumping stages
and n minus 2 denotes the number of DBD treatment devices. A pump
integrated DBD treatment apparatus of the present invention can be
employed for the treatment of noxious gases including
fluorocarbons.
[0089] It is also contemplated to employ five separate vacuum pumps
in series and to position a DBD treatment device of the present
invention between adjacent pump without integrating (not shown) the
five pumps with the three DBD treatment devices.
[0090] A flow chart illustrating another embodiment of the present
invention is shown in FIG. 25. A gas discharging process 1610 such
a wafer fabrication tool, for example an etch reactor, is adapted
for discharging one or more process gases or by-product gases to a
DBD treatment device of the present invention, such as DBD
treatment devices 1000 and 1100 illustrated in FIGS. 19 and 20
respectively. Returning to FIG. 25, the DBD device is in a standby
mode 1612 such that it is not activated to strike a plasma in the
DBD reactor of the DBD treatment device. A process determination
1614 is made to determine if processing gas is flowing from process
1610. Where there is no gas flow, the DBD reactor standby status is
continued. If a gas flow is indicated, an automated process inquiry
1616 is made to determine if one or more interlocks are activated
causing the power to the DBD device to be turned off 1618 or
alternatively (not shown) causing the DBD device to be in a standby
mode. Suitable interlocking techniques are exemplified by interlock
feature 1424 described in connection with FIG. 23. If the DBD
device is not switched off as a result of an interlock feature, a
next process determination 1620 is made to determine if the gas
flowing to/or through the DBD device is within pre-defined
processing limits such as pressure and/or temperature. Examples of
suitable processing limits for the treatment of FCs in the novel
DBD device include a pressure greater than about 100 mT and a
temperature lower than about 100.degree. C. The DBD device remains
in the standby mode 1612 if the gas flow is not within the
pre-defined limits.
[0091] Where the gas flow is found to within the pre-defined
limits, a subsequent process query 1622, see FIG. 25, is made to
determine whether or not the novel process illustrated in FIG. 25
employs a delay time period before activating the DBD device. Such
a delay period can include the time that is required for a gas to
flow from gas discharging process 1610 to the DBD treatment device.
The delay time is activated 1624 if such a delay is required. Upon
completion 1626 of the delay time period, or when the process does
not require a delay time period, a process inquiry 1628 is made to
automatically determine if addition of a reactive gas, such as an
oxidizing gas, is needed. The need for a reactive gas can be
indicated for example through the processing gases/conditions that
are used in process 1610, such as through information that is
provided by a gas panel system for process 1610. If required, one
or more reactive gases can be selected and introduced 1630 between
process 1610 and the DBD treatment device, or directly into the
reactor tube of the novel DBD device. For example if processing
history or real time processing data show the presence of FCs, an
appropriate computer program can provide instructions 1630 to
select a reactive gas in a specific ratio to the gases that are to
be treated in the DBD treatment device. If 02 is the required gas,
the gas flow preferred ratio of O.sub.2 to FCs includes the
following:
O.sub.2/CF.sub.4=1.2/1, O.sub.2/CHF.sub.3=1.2/1,
O.sub.2/CH.sub.2F.sub.2=1- .2, O.sub.2/C.sub.2F.sub.6=2.4,
O.sub.2/C.sub.4F.sub.6=4.8 and O.sub.2/C.sub.4F.sub.8=4.8.
[0092] If the selected gas has been introduced 1630 at the required
flow rate, or if the treatment does not require the addition of a
reactive gas, an optional status check 1632 is made to determine if
the status of the DBD treatment device is acceptable for starting
the DBD process. If the status is not acceptable, the DBD device
remains in, or is returned to, the standby mode 1612. If the status
is deemed to be acceptable, the DBD device is activated to strike a
plasma 1634 in the gas that is to processed. Preferably, the
performance of the DBD treatment device and the composition of the
gases that are discharged from the DBD device is monitored in step
1636. These gases can then be discharged 1638 to an additional gas
treatment facility, such as a scrubber, for removal of noxious
substances. It will be understood that some processing steps that
are indicated in the flow chart shown in FIG. 25 can be executed in
a sequence that is different from the sequence which is shown.
Also, it will be understood that the invention is equally operable
when the DBD treatment device is switched off rather than standby
mode 1612, providing the device is fully activated upon the
occurrence of the stated processing condition. As shown in FIG. 25,
the DBD treatment device of the present invention operates on
demand, based on processing conditions and interactions.
Alternatively, it is contemplated to inject N.sub.2 gas between gas
discharging process 1610 and the DBD reactor in order to maintain
the DBD plasma during interruptions of the gas flow from the gas
discharging process. These interruptions can for example result
from processing steps wherein a product such a wafer is moved into
or out of a processing chamber.
[0093] Experiments were conducted wherein gas mixtures of CH.sub.4
and O.sub.2 were treated in a DBD treatment device of the present
invention, using 7 cells, each having a nominal power of 350 W. In
these experiments the DRE % was determined as shown in Table A, at
different CF.sub.4 and O.sub.2 flow rates and at pressures ranging
from 600 mT to 900 mT, and using methodologies for DRE
determinations such as are well known to those of ordinary skill in
the art.
1 TABLE A CF.sub.4 Flow O.sub.2 Flow Pressure DRE (sccm) (sccm)
(mT) (%) 50 60 750 98.1 50 180 750 98.4 150 60 750 68.3 150 180 750
88.6 100 60 600 89.2 100 60 900 88.4 100 180 600 96.0 100 180 900
94.6 50 120 600 98.3 150 120 600 86.2 50 120 900 98.3 150 120 900
84.9 100 120 750 95.7 100 120 750 95.5 100 120 750 95.6
[0094] The results of Table A show that the DBD treatment device of
the present invention is capable of achieving a high DRE percentage
through optimization of the variables that are shown in this
table.
[0095] In another series of experiments, novel DBD treatment
devices having 6, 7 and 8 cells were evaluated at power levels
ranging from 282 W to 367 W output. The resulting DRE percentages
are shown in Table B, using CF.sub.4 at a flow rate of 100 sccm
(standard cubic centimeter per minute) and O.sub.2 at a flow rate
of 150 sccm.
2 TABLE B Number Power of cells Per cell (W) DRE % 6 282 87.0 6 297
88.6 6 338 89.2 6 367 92.0 7 282.5 90.7 7 311 93.2 7 339 94.8 7 367
96.0 8 282 94.0 8 311 96.0 8 339 97.3 8 367 98.0
[0096] The results in Table B indicate that for a given flow rate,
an increase in the number of cells results in a more significant
DRE improvement than an increase in the power per cell.
[0097] Experimental results were obtained with a DBD treatment
device having 7 cells, each cell having a nominal output of 350 W.
Each cell was powered with a dedicated constant power DC power
supply, providing AC power to the electrodes of the cells. A via
etch of a semiconductor wafer was performed in a parallel plate
plasma etch reactor using the parameters shown in Table C.
3 TABLE C C.sub.4F.sub.6 Flow (sccm) 30 CHF.sub.3 Flow (sccm) 80
O.sub.2 Flow (sccm) 50 Ar Flow (sccm) 600 Bias Power (W) 3000
Pressure (mT) 80
[0098] Etching was continued during 3 minutes. Gases discharged
from the etch reactor were pumped to the DBD treatment device,
while introducing O.sub.2 at a flow rate of 250 sccm. The
composition of gases exiting from the DBD device was determined
under the following three processing conditions: (1) etch reactor
plasma and DBD plasma off, (2) etch reactor plasma on without
striking a plasma in the DBD device and (3) etch reactor plasma on
and DBD plasma on. The composition of the mixture of gases
discharged from the DBD treatment device is shown in Table D,
wherein the composition is expressed as total mg of mass for a
duration of 3 minutes.
4TABLE D Etch & DBD off, Etch on, DBD off Etch & DBD on
Mass (mg) Mass (mg) Mass (mg) C.sub.4F.sub.6 0.55 0.052 0.0001
CF.sub.4 0.28 0.015 CHF.sub.3 0.518 0.4 9E-04 C.sub.2F.sub.6 0.168
0.001 F.sub.2 0.004 0.44 COF.sub.2 0.071 0.353 HF 0.021 0.062
SiF.sub.4 0.026 0.049 CO.sub.2 0.000 0.032 CO 0.106 0.025
[0099] In Table D, C.sub.4F.sub.6 and CHF.sub.3 are etch chemistry
gases while the other gases listed in this table are formed as
by-products of the etch reaction, or as reaction products of plasma
treatment in the DBD treatment device. This experiment resulted in
98.52% DRE.
[0100] In another embodiment of the present invention,
schematically illustrated in FIG. 26, a novel technique for
generating fluorine species for use in chemical processes is
illustrated. A gas supply 1710 contains one or more gaseous
fluorine compounds, such as NF.sub.3, or a mixture of gases
including one or more fluorine compounds. Gas from gas supply 1710
is introduced into a gas inlet 1712 of DBD device 1714 of the
present invention. While flowing through the DBD device, the gas is
subjected to plasma treatment, forming fluorine species such as
fluorine atoms, ions and/or radicals. These species are discharged
from DBD device 1714 through gas outlet 1716. The fluorine species
thus generated can be used in a chemical processing method,
technique or device 1718. Examples of processing device 1718
include wafer fabricating devices, such as etch chambers and vapor
deposition chambers wherein the fluorine can be utilized to etch
semiconductor devices or to clean the fabricating chambers. DBD
device 1714 includes for example novel DBD cells 100, 200, 500 and
800, novel DBD reactors 900, 1010 and 1110 and novel DBD treatment
devices 540, 1000 and 1100 as described in connection with FIGS. 6,
9, 14, 17, 18, 19 and 20 respectively. A suitable gas supply 1710
includes equipment such as gas supply containers, for example
pressurized containers, and/or a gas control panel. The combination
of novel DBD device 1714 and a chemical processing device 1718
forms a chemical processing system of the present invention. A
semiconductor processing system of the present system is formed by
the combination of novel DBD device 1714 and chemical processing
equipment 1718 comprising a semiconductor or wafer manufacturing
device.
[0101] The invention has been described in terms of the preferred
embodiment. One skilled in the art will recognize that it would be
possible to construct the elements of the present invention from a
variety of means and to modify the placement of components in a
variety of ways. While the embodiments of the invention have been
described in detail and shown in the accompanying drawings, it will
be evident that various additional modifications are possible
without departing from the scope of the invention as set forth in
the following claims.
* * * * *