U.S. patent application number 10/990433 was filed with the patent office on 2005-07-07 for plasma processing apparatus.
Invention is credited to Suzuki, Masaki.
Application Number | 20050145341 10/990433 |
Document ID | / |
Family ID | 34708645 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050145341 |
Kind Code |
A1 |
Suzuki, Masaki |
July 7, 2005 |
Plasma processing apparatus
Abstract
A plasma processing apparatus has a liquid storage vessel which
is formed outside of a dielectric window and in which a
plasma-exciting coil or electrode is placed inside and moreover in
which an electrically insulative liquid is stored in the inside of
the liquid storage vessel, as well as a cooling unit and a heating
unit for the liquid. Temperature of the liquid stored in the liquid
storage portion is adjusted, by which temperature of the
plasma-exciting coil or electrode and the dielectric window is
controlled via the liquid.
Inventors: |
Suzuki, Masaki;
(Hirakata-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
34708645 |
Appl. No.: |
10/990433 |
Filed: |
November 18, 2004 |
Current U.S.
Class: |
156/345.49 ;
257/E21.218 |
Current CPC
Class: |
H01J 37/32522 20130101;
H01L 21/3065 20130101; H01J 37/321 20130101 |
Class at
Publication: |
156/345.49 |
International
Class: |
C23F 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2003 |
JP |
2003-389251 |
Claims
1. A plasma processing apparatus for imparting an electromagnetic
field to reactant gas introduced into a evacuated processing
chamber to excite plasma and performing plasma processing on a
substrate set in the processing chamber, comprising: a vacuum
vessel which defines the processing chamber in which the substrate
is held and the plasma processing for the substrate is performed,
and which includes a dielectric window forms a part of the vacuum
vessel, for hermetically closing the vacuum chamber, and a gas
supply portion for supplying the reactant gas into the processing
chamber; a plasma-exciting coil which is placed so as to confront
the processing chamber via the dielectric window, for imparting an
electromagnetic field to interior of the processing chamber via the
dielectric window with RF power applied; an evacuation unit for
evacuating the interior of the processing chamber to draw a vacuum
so that pressure in the processing chamber is kept generally
constant; an RF power supply for applying the RF power to the
plasma-exciting coil; and a liquid storage vessel which includes
the dielectric window as a part thereof and which defines in
interior thereof a liquid chamber for storing therein an
electrically insulative liquid so that an opposite surface to a
processing chamber-side surface of the dielectric window is
immersed in the liquid and in which the plasma-exciting coil is
placed.
2. The plasma processing apparatus as claimed in claim 1, further
comprising a liquid temperature adjusting unit which has a cooling
unit and/or a heating unit for the electrically insulative liquid
and for adjusting temperature of the liquid stored in the liquid
storage vessel to control temperature of the plasma-exciting coil
and the dielectric window via the liquid.
3. The plasma processing apparatus as claimed in claim 2, wherein
the liquid storage vessel except for the dielectric window is
formed of an electrical conductor.
4. The plasma processing apparatus as claimed in claim 2, wherein
the liquid storage vessel is integrated with the dielectric window
whereby an integrated dielectric window is formed, and the
integrated dielectric window has a liquid flow passage for the
electrically insulative liquid inside thereof as the liquid chamber
in which the plasma-exciting coil is placed.
5. The plasma processing apparatus as claimed in claim 2, wherein
the liquid temperature adjusting unit is placed outside the liquid
storage vessel, the plasma processing apparatus further comprising:
a liquid circulating unit for circulating the electrically
insulative liquid into the liquid chamber through a liquid flow
passage communicated with the liquid chamber so that the liquid is
circulatable therealong.
6. The plasma processing apparatus as claimed in claim 2, wherein
the liquid temperature adjusting unit has a heat exchange portion
which is provided on a wall portion of the liquid storage vessel
and which serves for heat exchange with the electrically insulative
liquid stored in the liquid storage vessel, and a fluid stored in
the heat exchange portion so as to be separable from the
electrically insulative liquid is temperature-controlled by the
cooling unit or the heating unit, whereby temperature of the
electrically insulative liquid in the liquid storage portion is
adjusted.
7. The plasma processing apparatus as claimed in claim 2, wherein
the cooling unit is an air cooling unit for air cooling an outer
wall surface of the liquid storage vessel, and the heating unit is
a heater placed inside or outside the liquid storage vessel.
8. The plasma processing apparatus as claimed in claim 2, wherein
the liquid temperature adjusting unit comprises: a supply portion
of the electrically insulative liquid to the liquid chamber; and a
discharge portion for discharge of liquid vapor generated by
vaporization of the electrically insulative liquid from the liquid
chamber, and wherein the electrically insulative liquid is a liquid
which has a boiling point at or near an adjustment temperature of
the dielectric window and the plasma-exciting coil or a temperature
therearound.
9. The plasma processing apparatus as claimed in claim 1, wherein
in the liquid storage vessel, the electrically insulative liquid is
stored so that the plasma-exciting coil is further immersed in the
electrically insulative liquid.
10. The plasma processing apparatus as claimed in claim 1, wherein
the plasma-exciting coil is brought into close contact with the
liquid chamber-side surface of the dielectric window with a
pressure of the electrically insulative liquid supplied into the
liquid storage vessel.
11. The plasma processing apparatus as claimed in claim 10, further
comprising: a liquid chamber dividing member for dividing the
liquid storage vessel into a first chamber to which the
electrically insulative liquid is supplied, and a second chamber
which is communicated with the first chamber so that the liquid
supplied to the first chamber can be supplied to inside of the
second chamber and in which the liquid chamber-side surface of the
dielectric window and the plasma-exciting coil are placed inside;
and a support guide member for, in the liquid chamber, supporting
the liquid chamber dividing member while guiding a dividing
position between the first chamber and the second chamber along a
variable direction, wherein the plasma-exciting coil is pressed
against and brought into close contact with the surface of the
dielectric window by a pressure difference between the liquid
stored in the first chamber and the liquid stored in the second
chamber.
12. The plasma processing apparatus as claimed in claim 11, wherein
in the second chamber of the liquid storage vessel is formed a
generally spiral-shaped liquid flow passage in which gaps of the
generally spirally turned plasma-exciting coil are surrounded by
the liquid chamber dividing member and the dielectric window.
13. The plasma processing apparatus as claimed in claim 12, wherein
a supply position of the electrically insulative liquid from the
first chamber to the second chamber is set on a center side of the
liquid flow passage so that the liquid is circulatable from center
side toward outer peripheral side of the generally spiral-shaped
liquid flow passage formed between the spiral-shaped
plasma-exciting coil in the second chamber of the liquid storage
vessel.
14. The plasma processing apparatus as claimed in claim 2, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
15. The plasma processing apparatus as claimed in claim 2, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
16. The plasma processing apparatus as claimed in claim 3, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
17. The plasma processing apparatus as claimed in claim 4, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
18. The plasma processing apparatus as claimed in claim 5, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
19. The plasma processing apparatus as claimed in claim 6, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
20. The plasma processing apparatus as claimed in claim 7, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
21. The plasma processing apparatus as claimed in claim 8, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
22. The plasma processing apparatus as claimed in claim 9, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
23. The plasma processing apparatus as claimed in claim 10, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
24. The plasma processing apparatus as claimed in claim 11, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
25. The plasma processing apparatus as claimed in claim 12, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
26. The plasma processing apparatus as claimed in claim 13, wherein
the electrically insulative liquid is pure water having a
resistivity of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
27. The plasma processing apparatus as claimed in claim 3, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
28. The plasma processing apparatus as claimed in claim 4, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
29. The plasma processing apparatus as claimed in claim 5, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
30. The plasma processing apparatus as claimed in claim 6, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
31. The plasma processing apparatus as claimed in claim 7, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
32. The plasma processing apparatus as claimed in claim 8, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
33. The plasma processing apparatus as claimed in claim 9, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
34. The plasma processing apparatus as claimed in claim 10, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
35. The plasma processing apparatus as claimed in claim 11, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
36. The plasma processing apparatus as claimed in claim 12, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
37. The plasma processing apparatus as claimed in claim 13, wherein
the electrically insulative liquid is a fluorine inert oil, a
silicone oil, or organic oils and fats.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to plasma processing
apparatuses such as dry etching apparatuses and plasma CVD
apparatuses to be used for the manufacture of semiconductor or
other thin-film circuits and electronic components or boards on
which those electronic circuits and others are to be mounted.
[0002] Conventionally, as one of the plasma processing apparatuses
to be used for the manufacture of semiconductor or other thin-film
circuits, electronic components, or boards, there has been a plasma
processing apparatus of the RF (Radio Frequency) plasma excitation
method in which RF power is applied to a plasma-exciting coil or
electrode positioned outside a vacuum vessel to excite a plasma in
the vacuum vessel, and plasma processing is performed on a
substrate (work piece) set within the vacuum vessel with the
excited plasma. The plasma processing apparatus of this method is
so designed with an RF magnetic field generated outside of the
vacuum vessel, the RF magnetic field is transferred into the vacuum
vessel via a dielectric window so that electrons are accelerated by
this electromagnetic field to excite a plasma, by which the
processing is carried out.
[0003] As an example of such a conventional plasma processing
apparatus, a schematic sectional view of a plasma processing
apparatus 500 is shown in FIG. 10 (see, e.g., Japanese unexamined
patent publication No. 2003-59904, Specification of U.S. Pat. No.
5,540,824, Japanese unexamined patent publication No.
H09-74089).
[0004] As shown in FIG. 10, the plasma processing apparatus 500 is
equipped with a vacuum vessel 501 which has an opening at the top
thereof and generally cylindrical shaped (only part of the vacuum
vessel 501 is shown in FIG. 10), and a bell jar (dielectric window)
502 which is formed of a generally hemispherical-shell shaped
dielectric material (e.g., quartz) and which is provided so as to
cover the opening at the top of the vacuum vessel 501, where a
processing chamber 503 is formed which is a space closed by the
vacuum vessel 501 and the bell jar 502 and a space where plasma
processing is performed. Further, the plasma processing apparatus
500 has a reactant gas supply portion 504 which is provided at an
upper portion of a side face of the vacuum vessel 501 and which
serves for introducing a specified reactant gas into the vacuum
vessel 501, and a vacuum pump (not shown) which is an evacuator for
discharging air or gas present in the vacuum vessel 501 (in the
processing chamber 503). Also, near the top of the bell jar 502 are
placed a plasma-exciting coil 505 formed of a wire conductor in a
spiral shape, as well as a coil-use RF power supply 506 for
applying RF power to the plasma-exciting coil 505. Further, a
substrate electrode 507 is provided near a generally center in the
vacuum vessel 501, and a substrate-electrode use RF power supply
508 for applying RF power to the substrate electrode 507 is
provided. A substrate 509 which is to be subjected to plasma
processing is held on the substrate electrode 507 within the vacuum
vessel 501.
[0005] As shown in FIG. 10, in order that the electromagnetic field
generated from the coil 505 to which RF power is applied is
prevented from escaping to outside of the apparatus, the coil 505
and the bell jar 502 are covered with a ground shield 510 formed of
a conductor member. In this ground shield 510, a vent hole 511 is
provided at a left end in the figure, and a cooling fan 512 is
provided at a right end in the figure, so that air in the ground
shield 510 can be discharged to outside of the apparatus by the
cooling fan 512, and that air outside the apparatus can be
introduced into the ground shield 510 through the vent hole
511.
[0006] In the conventional plasma processing apparatus 500 of such
a construction, air is discharged from interior of the vacuum
vessel 501 (i.e., interior of the processing chamber 503) by the
vacuum pump, while a specified gas is introduced thereinto from the
reactant gas supply portion 504, so that the interior of the
processing chamber 503 is kept at a specified pressure. In such a
state, RF power is applied to the coil 505 by the coil-use RF power
supply 506 so that an electromagnetic field is imparted to the
reactant gas within the processing chamber 503 from the coil 505
via the bell jar 502, thereby exciting a plasma. Use of this
excited plasma makes it possible to perform plasma processing such
as etching, deposition or surface reforming on the substrate 509
held to the substrate electrode 507. In do this, applying RF power
also to the substrate electrode 507 by the substrate-electrode use
RF power supply 508 makes it possible to control ion energy which
reaches the substrate 509.
[0007] In such a plasma processing, also, although temperature of
the bell jar 502 or the coil 505 increases along with the
application time of the RF power, yet the atmosphere in the
internal space of the ground shield 510 is mechanically ventilated
by the cooling fan 512 and the vent hole 511, so that the
temperature increase can be reduced more or less.
[0008] Further, a schematic sectional view of a plasma processing
apparatus 600 according to another prior art example is shown in
FIG. 11 (see, e.g., Japanese unexamined patent publication No.
2000-21858, and Japanese unexamined patent publication No.
H03-79025). As shown in FIG. 11, the plasma processing apparatus
600 differs in construction from the foregoing plasma processing
apparatus 500 in terms of having a generally plate-shaped
dielectric window 602 instead of the generally hemispherical-shell
shaped bell jar 502. More specifically, the plasma processing
apparatus 600 has generally cylindrical-shaped vacuum vessel 601
which has an opening, a dielectric window 602, a reactant gas
supply portion 604, a flat spiral coil (planar spiral-shaped coil)
605, a coil-use RF power supply 606, a substrate electrode 607 on
which a substrate 609 can be placed and held, a substrate-electrode
use RF power supply 608, a ground shield 610, and a vacuum pump
613. The opening at the top of the vacuum vessel 601 is closed and
sealed by the dielectric window 602, where a closed internal space
serves as the plasma processing chamber 603. Further, a matching
box 606a is provided between the coil-use RF power supply 606 and
the coil 605, and a matching box 608a is also provided between the
substrate-electrode use RF power supply 608 and the substrate
electrode 607.
[0009] As shown in FIG. 11, a vent hole 611 is formed at a side
face of the ground shield 610, a cooling fan 612 is provided at an
upper portion of the matching box 606a, and a large opening is
formed at a center portion of the ground shield 610 coupled to the
matching box 606a. By the cooling fan 612 and the vent hole 611
being provided as shown above, the dielectric window 602 and the
coil 605, which would increase in temperature during plasma
processing, can be cooled by outside air, allowing their
temperature increase to be suppressed to some extent.
[0010] Further, inside the substrate electrode 607 is formed an
internal liquid passage 614 which allows a cooling/heating medium
liquid to be circulated therealong, and this liquid passage 614 is
communicated through a cooling/heating medium liquid circulation
passage 616 with a chiller unit 615 installed outside the
apparatus. It is noted that the cooling/heating medium liquid as
shown above is given by the use of, for example, water, ethylene
glycol, fluorine oil or the like. Further, the chiller unit 615 is
provided with a pump for circulating the cooling/heating medium
liquid, a refrigerator, a heater, a water cooling (air cooling)
unit for the refrigerator, and the like. By such a chiller unit
615, the substrate electrode 607, which would increase in
temperature during plasma processing, can be cooled to suppress the
temperature increase. It is also possible to heat the substrate
electrode 607 in advance for the preparation of plasma
processing.
SUMMARY OF THE INVENTION
[0011] However, in the conventional plasma processing apparatus
500, since the bell jar 502 and the like that would increase in
temperature are cooled by mechanically ventilating the internal
space of the ground shield 510, which covers the bell jar 502 and
the coil 505, by means of the small-diameter cooling fan 512 and
the vent hole 511, there are some cases where the bell jar 502 may
increase in temperature to, for example, about 200.degree. C. along
with an elapse of discharge time of the electromagnetic field due
to a lack of cooling power. Discharge time of 3 minutes or longer
makes this tendency to be more noticeable. Like this, in cases
where the bell jar 502 is increased in temperature, there may occur
emission of gas components from a deposited film deposited on an
inner wall of the bell jar 502, causing the atmosphere of a plasma
processing region R within the processing chamber 503 to be
changed.
[0012] Also, in a halt of plasma processing or standby state of the
plasma processing apparatus 500, the temperature of the bell jar
502 is also decreased to room temperature. In such a case, the low
temperature of the dielectric window accelerates film deposition to
the dielectric window during the next-time plasma processing, and
moreover residual gas components within the plasma processing
region R is adsorbed by the deposited film to make a degassing
source in the next-time temperature increase. Repeated execution
and halt of plasma processing shown above causes the atmosphere
within the plasma processing region R to be unstable (unsteady),
and increasing a thickness of the deposited film with increasing
number of times of processing leads to change of the atmosphere.
This gives rise to an issue that plasma processing of high
repeatability cannot be implemented.
[0013] Further, repeating such plasma processing and plasma halt
causes the quartz of the bell jar 502 and the deposited film to
repetitively increase and decrease in temperature, so that peeling
of the deposited film occurs due to a difference in coefficient of
thermal expansion between the two members. As a result, dust
adheres onto the substrate 509 placed on the substrate electrode
507, giving rise to an issue of device failures on the substrate to
be processed.
[0014] Furthermore, in the plasma processing, ozone is generated by
corona discharge around the coil 505 and ultraviolet rays in plasma
emission, and the generated ozone may be diffused outside the
plasma processing apparatus 500 by the cooling air. In such a case,
there arise issues of a health problem of the operator as well as
acceleration of deterioration of the apparatus component parts.
[0015] Such respective issues can occur also to the plasma
processing apparatus 600 similarly. However, the plasma processing
apparatus 600, which employs a not generally hemispherical-shell
shaped but plate-shaped dielectric window 602, inevitably has to be
large in its thicknesses so as to withstand the vacuum of the
processing chamber 603 (i.e., to withstand the atmospheric
pressure). Besides, the dielectric window 602 is formed of quartz
or the like, which has a low heat transfer coefficient, thus giving
rise to another issue that the dielectric window 602 becomes harder
to cool.
[0016] Accordingly, an object of the present invention is to solve
these and other issues and provide a plasma processing apparatus
which is capable of performing stable plasma processing with
enhanced repeatability, and which is smaller in dust generation
within the processing chamber even with repetitive execution of
plasma processing,
[0017] In order to achieve the aforementioned object, the present
invention is constructed as follows.
[0018] According to a first aspect of the present invention, there
is provided a plasma processing apparatus for imparting an
electromagnetic field to reactant gas introduced into a evacuated
processing chamber to excite plasma and performing plasma
processing on a substrate set in the processing chamber,
comprising:
[0019] a vacuum vessel which defines the processing chamber in
which the substrate is held and the plasma processing for the
substrate is performed, and which includes a dielectric window
forms a part of the vacuum vessel, for hermetically closing the
vacuum chamber, and a gas supply portion for supplying the reactant
gas into the processing chamber;
[0020] a plasma-exciting coil which is placed so as to confront the
processing chamber via the dielectric window, for imparting an
electromagnetic field to interior of the processing chamber via the
dielectric window with RF power applied;
[0021] an evacuation unit for evacuating the interior of the
processing chamber to draw a vacuum so that pressure in the
processing chamber is kept generally constant;
[0022] an RF power supply for applying the RF power to the
plasma-exciting coil; and
[0023] a liquid storage vessel which includes the dielectric window
as a part thereof and which defines in interior thereof a liquid
chamber for storing therein an electrically insulative liquid so
that an opposite surface to a processing chamber-side surface of
the dielectric window is immersed in the liquid and in which the
plasma-exciting coil is placed.
[0024] According to a second aspect of the present invention, there
is provided a plasma processing apparatus as defined in the first
aspect, further comprising a liquid temperature adjusting unit
which has a cooling unit and/or a heating unit for the electrically
insulative liquid and for adjusting temperature of the liquid
stored in the liquid storage vessel to control temperature of the
plasma-exciting coil and the dielectric window via the liquid.
[0025] According to a third aspect of the present invention, there
is provided a plasma processing apparatus as defined in the second
aspect, wherein the liquid storage vessel except for the dielectric
window is formed of an electrical conductor.
[0026] According to a fourth aspect of the present invention, there
is provided a plasma processing apparatus as defined in the second
aspect, wherein
[0027] the liquid storage vessel is integrated with the dielectric
window whereby an integrated dielectric window is formed, and the
integrated dielectric window has a liquid flow passage for the
electrically insulative liquid inside thereof as the liquid chamber
in which the plasma-exciting coil is placed.
[0028] According to a fifth aspect of the present invention, there
is provided a plasma processing apparatus as defined in the second
aspect, wherein the liquid temperature adjusting unit is placed
outside the liquid storage vessel, the plasma processing apparatus
further comprising:
[0029] a liquid circulating unit for circulating the electrically
insulative liquid into the liquid chamber through a liquid flow
passage communicated with the liquid chamber so that the liquid is
circulatable therealong.
[0030] According to a sixth aspect of the present invention, there
is provided a plasma processing apparatus as defined in the second
aspect, wherein the liquid temperature adjusting unit has a heat
exchange portion which is provided on a wall portion of the liquid
storage vessel and which serves for heat exchange with the
electrically insulative liquid stored in the liquid storage vessel,
and
[0031] a fluid stored in the heat exchange portion so as to be
separable from the electrically insulative liquid is
temperature-controlled by the cooling unit or the heating unit,
whereby temperature of the electrically insulative liquid in the
liquid storage portion is adjusted.
[0032] According to a seventh aspect of the present invention,
there is provided a plasma processing apparatus as defined in the
second aspect, wherein the cooling unit is an air cooling unit for
air cooling an outer wall surface of the liquid storage vessel,
and
[0033] the heating unit is a heater placed inside or outside the
liquid storage vessel.
[0034] According to an eighth aspect of the present invention,
there is provided a plasma processing apparatus as defined in the
second aspect, wherein the liquid temperature adjusting unit
comprises:
[0035] a supply portion of the electrically insulative liquid to
the liquid chamber; and
[0036] a discharge portion for discharge of liquid vapor generated
by vaporization of the electrically insulative liquid from the
liquid chamber, and wherein
[0037] the electrically insulative liquid is a liquid which has a
boiling point at or near an adjustment temperature of the
dielectric window and the plasma-exciting coil or a temperature
therearound.
[0038] According to a ninth aspect of the present invention, there
is provided a plasma processing apparatus as defined in the first
aspect, wherein in the liquid storage vessel, the electrically
insulative liquid is stored so that the plasma-exciting coil is
further immersed in the electrically insulative liquid.
[0039] According to a tenth aspect of the present invention, there
is provided a plasma processing apparatus as defined in the first
aspect, wherein the plasma-exciting coil is brought into close
contact with the liquid chamber-side surface of the dielectric
window with a pressure of the electrically insulative liquid
supplied into the liquid storage vessel.
[0040] According to an eleventh aspect of the present invention,
there is provided a plasma processing apparatus as defined in the
tenth aspect, further comprising:
[0041] a liquid chamber dividing member for dividing the liquid
storage vessel into a first chamber to which the electrically
insulative liquid is supplied, and a second chamber which is
communicated with the first chamber so that the liquid supplied to
the first chamber can be supplied to inside of the second chamber
and in which the liquid chamber-side surface of the dielectric
window and the plasma-exciting coil are placed inside; and
[0042] a support guide member for, in the liquid chamber,
supporting the liquid chamber dividing member while guiding a
dividing position between the first chamber and the second chamber
along a variable direction, wherein
[0043] the plasma-exciting coil is pressed against and brought into
close contact with the surface of the dielectric window by a
pressure difference between the liquid stored in the first chamber
and the liquid stored in the second chamber.
[0044] According to a twelfth aspect of the present invention,
there is provided a plasma processing apparatus as defined in the
eleventh aspect, wherein in the second chamber of the liquid
storage vessel is formed a generally spiral-shaped liquid flow
passage in which gaps of the generally spirally turned
plasma-exciting coil are surrounded by the liquid chamber dividing
member and the dielectric window.
[0045] According to a thirteenth aspect of the present invention,
there is provided a plasma processing apparatus as defined in the
twelfth aspect, wherein a supply position of the electrically
insulative liquid from the first chamber to the second chamber is
set on a center side of the liquid flow passage so that the liquid
is circulatable from center side toward outer peripheral side of
the generally spiral-shaped liquid flow passage in the second
chamber of the liquid storage vessel.
[0046] According to a fourteenth aspect of the present invention,
there is provided a plasma processing apparatus as defined in any
one of the second aspect through the thirteenth aspect, wherein the
electrically insulative liquid is pure water having a resistivity
of 1.times.10.sup.5 .OMEGA..multidot.cm or more.
[0047] According to a fifteenth aspect of the present invention,
there is provided a plasma processing apparatus as defined in any
one of the second aspect through the thirteenth aspect, wherein the
electrically insulative liquid is a fluorine inert oil, a silicone
oil, or organic oils and fats.
[0048] According to the first aspect or second aspect of the
present invention, since the plasma processing apparatus includes a
liquid storage vessel which is placed so as to confront the vacuum
vessel and which is hermetically closed by the dielectric window to
define in its interior a liquid storage vessel for storing therein
an electrically insulative liquid, a cooling unit for the liquid
and/or a heating unit, and a liquid temperature adjusting unit for
adjusting temperature of the liquid stored in the liquid storage
portion, the temperature of the dielectric window can be adjusted
to a desired temperature by cooling or heating the plasma-exciting
coil or electrode via the electrically insulative liquid.
[0049] For example, during the plasma processing on the held
substrate, although the dielectric window is increased in
temperature, cooling the electrically insulative liquid with the
cooling unit allows the amount of heat due to the temperature
increase to be eliminated from the surface of the dielectric window
that is kept in contact with the electrically insulative liquid, by
which temperature increase of the dielectric window can be
suppressed. Such suppression of temperature increase makes it
possible to suppress discharge of gas components into the
processing chamber from the formed deposited film on the inner
surface (i.e., a surface on the processing chamber side) of the
dielectric window.
[0050] On the other hand, in the plasma non-processing state (e.g.,
in a standby state of the plasma processing or after completion of
the plasma processing), the heating is applied to the
temperature-decreased dielectric window by the heating unit, so
that the temperature decrease of the dielectric window is
suppressed, allowing the dielectric window to be maintained within
the specified temperature range. Thus, film deposition onto the
dielectric window during plasma processing is suppressed, so that
adsorption of gas components in the processing chamber by the
deposited film can be suppressed. Accordingly, discharge and
adsorption of gas components caused by repetition of plasma
processing and non-processing can be suppressed, thereby
stabilizing the atmosphere in the plasma processing, so that a
plasma processing of high repeatability can be achieved.
[0051] Also, since the plasma-exciting coil is placed in the liquid
storage vessel in which the electrically insulative liquid shown
above is to be stored, where, for example, the coil is immersed in
the electrically insulative liquid, surface temperature of the coil
can also be adjusted concurrently with the temperature control of
the dielectric window. For instance, during the plasma processing,
cooling the coil, which is increased in temperature with the
application of the RF power, via the electrically insulative liquid
allows the temperature increase to be suppressed. Actively lowering
the surface temperature of the coil by such cooling can act to
suppress increases of the substrate temperature due to infrared
heating caused by excessive temperature increases of the coil so
that deterioration due to thermal oxidation of the coil itself can
also be prevented. The temperature adjustment for the dielectric
window and the plasma-exciting coil as shown above exerts a
sufficient effect even if the plasma processing time runs for 3
minutes to several hours, so that temperature changes are
minimized.
[0052] Also, since such temperature control of the dielectric
window and the plasma-exciting coil is performed not by
conventional air ventilation but by heat transfer between the
electrically insulative liquid and the dielectric window as well as
the coil with the use of the electrically insulative liquid that is
brought into contact with the dielectric window and the coil, it
becomes implementable to improve efficiency and controllability of
this temperature control depending on the improvement of heat
transferability as well as on the temperature stability by the heat
capacity of a high volume of the liquid against the intermittent
plasma heating.
[0053] Further, in the plasma processing apparatus of the first
aspect or second aspect, not that the cooling of the coil and the
dielectric window is performed not by mechanically ventilating air
around the coil (taking in fresh air from apparatus outside and
discharging the ambient air to apparatus outside), as in the
conventional plasma processing apparatus, but that the cooling or
the like of the coil or the like is performed by adjusting the
temperature of the electrically insulative liquid stored in the
liquid storage vessel in which the coil is placed inside thereof.
Accordingly, there occurs neither separation nor combination of
oxygen molecules in the air due to corona discharge or ultraviolet
rays in the air, and therefore there does not occur generation of
ozone. Consequently, the health problem of the operator can be
improved, and acceleration of deterioration of the apparatus and
the component parts of peripheral units due to the diffusion of
ozone can be prevented reliably.
[0054] According to the third aspect of the invention, the liquid
storage vessel is formed as a space surrounded by an inner wall of
the electrical conductor of ground potential and an outer surface
of the dielectric window, and the plasma-exciting coil is housed in
the liquid storage vessel. Accordingly, the liquid storage vessel
can be formed as one which is completely hermetically closed with a
simple construction and which serves also for ground shielding.
Thus, there can be provided a plasma processing apparatus which is
small in size and free from leakage of electromagnetic waves.
[0055] According to the fourth aspect of the invention, the liquid
storage vessel is formed of a dielectric material, and a continued
liquid flow passage formed by the liquid storage vessel and the
dielectric window is provided as the liquid storage vessel. Thus,
there can be provided a state that the liquid flow passage is
formed inside one integrated dielectric window in which the liquid
storage vessel and the dielectric window are integrated together.
Even when the dielectric window has a large-aperture planar shape
and has enough thickness to withstand atmospheric pressure, the
distance between one surface of the dielectric window on the plasma
processing chamber side and the liquid flow passage can be made
smaller, thus making it possible to provide a plasma processing
apparatus of high cooling and heating performance.
[0056] Also, since the plasma-exciting coil or the electrode is
placed within the flow passage formed inside the dielectric window
as shown above, the coil can be made closer to the inside of the
processing chamber, as compared with the case where the coil is
placed outer than the outer surface of the dielectric window, so
that high-density plasma excitation can be fulfilled.
[0057] According to the other aspect of the invention, since the
electrically insulative liquid is pure water having a large
specific heat and electrical insulation property, there can be
provided a plasma processing apparatus which has all of the
electrical insulation property necessary for contact with the
induction coil, an availability, successful handlability and safety
and which is successful in handlability as a whole of the apparatus
and high in practicability. Further, a dielectric constant of the
pure water as large as about 70, although causing a somewhat large
dielectric loss, acts to increase the electrostatic field effect
for plasma excitation, thus providing a plasma processing apparatus
of good ignitability.
[0058] Further, since the electrically insulative liquid is a
fluorine inert oil, or a silicone oil having not only electrical
insulation property but also properties of nonflammability,
chemical inertness and a wide temperature range of usability, using
the electrically insulative liquid in a closed circuit makes its
applicability to the plasma processing apparatus more
successful.
[0059] Further, since the liquid temperature adjusting unit is
placed outside the liquid storage portion and since the plasma
processing apparatus further comprises a liquid flow passage
communicated with the liquid storage portion and a liquid
circulating unit for circulating the electrically insulative liquid
through the liquid flow passage, the degree of freedom for the
installation of the liquid temperature adjusting unit can be
enhanced, so that the cooling or heating performance can be
enhanced. As such a liquid temperature adjusting unit shown above,
applicable are commercially available articles called chiller,
circulator or thermostat, producing an advantage of high
availability.
[0060] Further, the liquid storage portion has a generally closed
small capacity so that the storage volume of the electrically
insulative liquid (e.g., electrically insulative fluorine inert oil
or organic oils) to be stored in the liquid storage portion is made
small, thus allowing the cost therefor to be reduced. Also, such a
small capacity of the liquid storage portion makes it unlikely to
occur that the stored electrically insulative liquid may leak.
Further, in the heat exchange unit, the fluid to be stored so as to
be separable from the electrically insulative liquid may be a fluid
having no electrically insulation property, e.g. water (one other
than pure water), instead of the electrically insulative liquid,
allowing the cost required for the electrically insulative liquid
to be reduced also from such a viewpoint.
[0061] Further, since there is no need for providing the liquid
temperature adjusting unit of separate installation outside the
liquid storage portion, the liquid temperature adjusting unit can
be integrated compactly with the liquid storage portion. Thus,
there can be provided a plasma processing apparatus which is small
in size, small in the cost for the electrically insulative liquid
and less liable to leakage or other troubles.
[0062] Further, since the electrically insulative liquid is a
liquid which has a boiling point at a desired temperature, i.e., a
temperature generally coincident with an adjustment temperature of
the dielectric window and the plasma-exciting coil or the
electrode, the need for providing any special cooling mechanism in
the liquid temperature adjusting unit is eliminated, and latent
heat of vaporization of the liquid itself is used. Thus, there can
be provided a plasma processing apparatus which is capable of high
cooling power and has a small-size, simple construction.
[0063] Further, the liquid is stored in such a fashion that not
only the dielectric window is improved in the liquid but also the
plasma-exciting coil as well is immersed therein, occurrence of
ozone or the like that would be caused by the application of RF
power with the plasma-exciting coil placed in the atmospheric air
as in the prior art can reliably be prevented.
[0064] Further, since the plasma-exciting coil can be brought into
close contact with the surface of the dielectric window with a
pressure of the liquid supplied to the liquid storage portion,
applying RF power to the coil in the close contact state makes it
possible to induce a high voltage to a processing-chamber side
surface of the dielectric window. Thus, it becomes easier to start
or maintain discharge even with low pressure in the processing
chamber.
[0065] Furthermore, the cooling or heating of the coil can be
executed reliably and stably, and moreover the cooling or heating
of the dielectric window can be executed uniformly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0066] These and other aspects and features of the present
invention will become clear from the following description taken in
conjunction with the preferred embodiments thereof with reference
to the accompanying drawings, in which:
[0067] FIG. 1 is a schematic sectional view of a plasma processing
apparatus according to a first embodiment of the present
invention;
[0068] FIG. 2 is a schematic sectional view of a plasma processing
apparatus according to a second embodiment of the present
invention;
[0069] FIG. 3 is a schematic sectional view of a plasma processing
apparatus according to a modification example of the second
embodiment of the present invention;
[0070] FIG. 4 is a sectional view taken along the line A-A in the
plasma processing apparatus of FIG. 3;
[0071] FIG. 5 is a schematic sectional view of a plasma processing
apparatus according to a third embodiment of the present
invention;
[0072] FIG. 6 is a schematic sectional view of a plasma processing
apparatus according to a fourth embodiment of the present
invention;
[0073] FIG. 7 is a schematic sectional view of a plasma processing
apparatus according to a fifth embodiment of the present
invention;
[0074] FIG. 8 is a schematic sectional view of a plasma processing
apparatus according to a sixth embodiment of the present
invention;
[0075] FIG. 9 is a schematic sectional view of a plasma processing
apparatus showing a state in which part of coil is exposed from a
liquid level of the cooling/heating medium liquid stored in a
liquid chamber in the plasma processing apparatus of the sixth
embodiment;
[0076] FIG. 10 is a schematic sectional view (partial view) of a
plasma processing apparatus according to a prior art example;
and
[0077] FIG. 11 is a schematic sectional view of a plasma processing
apparatus according to another prior art example.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0078] Before the description of the present invention proceeds, it
is to be noted that like parts are designated by like reference
numerals throughout the accompanying drawings.
[0079] Hereinbelow, embodiments of the present invention are
described in detail with reference to the accompanying
drawings.
First Embodiment
[0080] A schematic sectional view of a plasma processing apparatus
800 which is an example of a plasma processing apparatus according
to a first embodiment of the present invention is shown in FIG.
1.
[0081] As shown in FIG. 1, the plasma processing apparatus 800 is
equipped with a vacuum vessel 801 which has an opening at the top
thereof and generally cylindrical shaped, and a dielectric window
(quartz plate) 802 which is formed of a generally disc-shaped
dielectric material (e.g., quartz) and which is provided so as to
close the opening at the top of the vacuum vessel 801, where a
processing chamber 803 is formed which is a space closed by the
vacuum vessel 801 and the dielectric window 802 and a space where
plasma processing is performed.
[0082] Further, as shown in FIG. 1, the vacuum vessel 801 is
divided into a lower vacuum vessel 801b, which is a lower part of
the generally cylindrical-shaped bottomed member, and an upper
vacuum vessel 801a, which is its upper portion and annular shaped,
where the vacuum vessel 801 is constructed by coupling the upper
vacuum vessel 801a and the lower vacuum vessel 801b to each other.
In addition, a seal member, for example, an O-ring 828 is placed at
the mutual coupling portion of the upper vacuum vessel 801a and the
lower vacuum vessel 801b, so that airtightness at the coupling
portion is ensured.
[0083] Also, the plasma processing apparatus 800 has a plurality of
reactant gas supply holes 4, an example of the reactant gas supply
portion, which are provided in upper portion of the inner side face
of the upper vacuum vessel 801a of the vacuum vessel 801 and which
serve for introducing a specified reactant gas into the vacuum
vessel 801, and a vacuum pump 13, an example of the evacuator,
which is connected to a gas outlet 13a provided at an inner side
face of the lower vacuum vessel 801b of the vacuum vessel 801 by
means of a discharge passage 13b and which serves for discharging
air or gas present in the vacuum vessel 801 (i.e., in the
processing chamber 803). Further, near the top of the dielectric
window 802, a coil 805 (or plasma-exciting coil 805), which is an
example of the plasma-exciting coil formed in spiral shape (helical
shape) of a flat-shaped conductor having a rectangular cross
section are arranged along the outer side face of the dielectric
window 802 (i.e., a surface of the dielectric window 802 opposite
to its surface confronting the processing chamber 803 so that the
coil is placed so as to confront the processing chamber 803 via the
dielectric window 802), and a coil-use RF power supply 806 for
applying RF power to the coil 805 via a matching box 818 is
provided outside the vacuum vessel 801. Further, a lower electrode
7 which is an example of the substrate electrode is provided near a
generally center in the vacuum vessel 801, and a lower-electrode
use RF power supply 8 for applying RF power to the lower electrode
7 via a matching box 19 is provided outside the vacuum vessel 801.
Besides, a substrate 9 which is to be subjected to plasma
processing by the plasma processing apparatus 800 is held on the
lower electrode 7 within the vacuum vessel 801.
[0084] Also, as shown in FIG. 1, a ground shield vessel 810 (or an
upper electrode casing 810) formed of an electrical conductor (a
conductive material such as aluminum alloy) of ground potential is
fixedly provided at an upper portion of the upper vacuum vessel
801a of the vacuum vessel 801 so as to cover the entire coil 805
placed near the outer surface of the dielectric window 802.
Further, near a generally center of this ground shield vessel 810,
a center electrode 814 connected to the coil-use RF power supply
806 via the matching box 818 is fitted via an insulating bushing
815 so as not to make electrical contact with the ground shield
vessel 810. This center electrode 814 is connected to a center-end
of the spiral-shaped coil 805 via an application terminal 816.
Also, an outer-end of the coil 805 is connected to the ground
shield vessel 810 via a grounding terminal 817, and the ground
shield vessel 810 is connected to a ground pole of the coil-use RF
power supply 806. Thus, it is implementable to apply RF power to
the coil 805 from the coil-use RF power supply 806 through the
center electrode 814 and the application terminal 816. In addition,
the coil 805, the center electrode 814, the application terminal
816 and the grounding terminal 817 are each plated with, for
example, gold. A casing 819 for placing the matching box 818 inside
thereof is fitted at an outer upper portion of the ground shield
vessel 810 to eliminate the amount of heat generated from the
matching box 818, and a cooling fan 860 for mechanically
ventilating air inside the casing 819 is set in the casing 819.
[0085] Further, as shown in FIG. 1, in the state that the
dielectric window 802 is placed so as to cover the opening portion
at the top of the vacuum vessel 801, fixing the ground shield
vessel 810 to the top of the vacuum vessel 801 allows the
dielectric window 802 of the above placement to be fixed in that
placement. Besides, with the dielectric window 802 fixed as shown
above, the inside space of the ground shield vessel 810 is closed
by the outer side surface of the dielectric window 802 (i.e., a
surface of the dielectric window 802 opposite to its surface
confronting the processing chamber), and a space in which the coil
805 is placed inside is formed. This space allows a cooling/heating
medium liquid, which is an example of electrically insulating
liquid, to be stored therein as will be described later, where the
space serves as a liquid chamber 820, which is an example of the
liquid storage portion, and further this ground shield vessel 810
closed by the dielectric window 802 is an example of the liquid
storage vessel. Also, a lower-side surface of the dielectric window
802, as viewed in the figure, is a processing chamber-side surface
(gas-seal-side surface) while its outside side surface is a liquid
chamber closure-side surface (liquid-seal-side surface).
[0086] Further, as shown in FIG. 1, inside of this liquid chamber
820 is placed a disc-shaped coil holding plate 850 in which in its
lower surface are formed recess portions 850a to be engaged with
upper portions of the spiral-shaped coil 805, as viewed in the
figure, which is to be placed on the outer surface of the
dielectric window 802. That is, the coil 805 is placed on the outer
surface of the dielectric window 802 in the liquid chamber 820 in a
state that the coil 805 is held to the lower surface of the coil
holding plate 850, as viewed in the figure, so that its spiral
shape is defined. Further, the coil holding plate 850, which is so
formed that its disc-shaped external shape is generally equal in
size to the shape of the inner side face of the ground shield
vessel 810, is placed slidably along the side wall (peripheral
face) of the liquid chamber 820. By guide bolts 851, which are
examples of support guide members fixed to an inner top plate of
the ground shield vessel 810, the coil holding plate 850 is
supported so as to be guidable for its vertical move (i.e., sliding
as described above) as viewed in the figure, where the coil holding
plate 850 is prevented by this support from rotating and loosening
off inside the ground shield vessel 810. Further, each of bias
springs 852 is attached to each of the guide bolts 851, and the
bias springs 852 have a function of normally biasing the coil
holding plate 850 toward the dielectric window 802 along the guide
bolts 851 placed in the vertical direction as viewed in the
figure.
[0087] By the coil holding plate 850 and the coil 805 being placed
in the liquid chamber 820 as shown above, the liquid chamber 820 is
divided by the coil holding plate 850 into two chambers, an upper
chamber 820a, which is an example of a first chamber, and a lower
chamber 820b, which is an example of a second chamber. That is, in
this first embodiment, the coil holding plate 850 is an example of
a liquid chamber dividing member which divides the liquid chamber
820 into the two chambers. Also, by the coil holding plate 850
being made variable in its support position, the dividing position
of the two chambers is made variable with, for example, external
force imparted.
[0088] The upper chamber 820a and the lower chamber 820b are
communicated with each other by through hole 850a formed at a
generally center of the coil holding plate 850. Further, in the
lower chamber 820b, since a lower surface of the coil 805 held to
the coil holding plate 850 is kept in contact with the outer
surface of the dielectric window 802, a space (spiral-shaped gap)
of the spiral-shaped coil 805 is surrounded by the lower surface of
the coil holding plate 850 and the outer surface of the dielectric
window 802, as viewed in the figure, by which a spiral-shaped
liquid flow passage 854 for the cooling/heating medium liquid is
formed. That is, in the liquid chamber 820, the upper chamber 820a
is communicated through the through hole 850a with center portion
of the spiral-shaped liquid flow passage 854 formed in the lower
chamber 820b.
[0089] Moreover, in the ground shield vessel 810, a cooling/heating
medium liquid supply hole 810b to the upper chamber 820a as well as
a cooling/heating medium liquid discharge hole 810a which is
communicated with outer-peripheral end portions of the
spiral-shaped passage 854 in the lower chamber 820b and which is
derived from the passage 854 are formed so as to extend through a
side wall of the ground shield vessel 810. Thus, by virtue of the
formation of the supply hole 810b and the discharge hole 810a for
the cooling/heating medium liquid, a continued flow passage for the
cooling/heating medium liquid is formed in the liquid chamber 820
so that the cooling/heating medium liquid supplied from the supply
hole 810b into the upper chamber 820a flows into the lower chamber
820b through the through holes 850a, the cooling/heating medium
liquid then being made to flow from the center toward the outer
peripheral end portion of the spiral liquid flow passage 854, by
which the cooling/heating medium liquid can be discharged through
the discharge hole 810a at the outer peripheral end portion. By
virtue of the formation of such a continued liquid flow passage,
temperature of the dielectric window 802, and the coil 805 can be
adjusted by adjusting the temperature of the cooling/heating medium
liquid to be put into flow.
[0090] Also, as shown in FIG. 1, a liquid flow passage 823 which
allows the cooling/heating medium liquid to flow therethrough is
formed inside the lower electrode 7, so that the lower electrode 7
can be maintained at a desired temperature by making the
cooling/heating medium liquid, which has been adjusted to a desired
temperature, flow from a supply hole 823b, which is one end of the
liquid flow passage 823, to a discharge hole 823a, which is the
other end.
[0091] Further, a cooling/heating medium liquid flow passage 853
formed in, for example, an annular shape is formed also in the
upper vacuum vessel 801a of the vacuum vessel 801, and a supply
hole 853b and a discharge hole 853a for the cooling/heating medium
liquid are formed in the liquid flow passage 853. The
cooling/heating medium liquid that has been adjusted to a desired
temperature is circulated so as to be supplied into the liquid flow
passage 853 through the supply hole 853b and discharged from the
liquid flow passage 853 through the discharge hole 853a, thus
allowing the temperature in the processing chamber 803 to be
adjusted through the inner side face of the upper vacuum vessel
801a.
[0092] Further, a liquid flow passage 822, which is an example of
the liquid flow passage that makes these supply holes 810b, 853b
and 823b communicated with the discharge holes 853a, 823a, and the
liquid flow passage 822, and also makes discharge hole 810a
communicated with liquid flow passage 822 is provided so as to be
connected to a chiller unit 821. The chiller unit 821 includes: a
refrigerator (an example of the cooling unit) for cooling the
cooling/heating medium liquid; a heater (an example of the heating
unit) for heating the cooling/heating medium liquid; a
cooling/heating medium liquid tank for storing therein the
cooling/heating medium liquid; a pump which is an example of the
liquid circulating unit for supplying (circulating) the
cooling/heating medium liquid; a water/air cooling unit for
eliminating heat generated by cooling operation of the
refrigerator; a temperature control unit 821a for controlling
temperature of the cooling/heating medium liquid to a desired
temperature by controlling operations of the above individual
constituent sections; and a temperature sensor 821b for detecting a
temperature of the cooling/heating medium liquid and outputting the
detected temperature to the temperature control unit 821a. The
chiller unit 821 constructed as shown above has both a function of
adjusting (controlling) the temperature of the cooling/heating
medium liquid to a desired temperature by cooling or heating the
cooling/heating medium liquid, and a function of supplying the
temperature-controlled cooling/heating medium liquid into the
liquid chamber 820 or the like through the liquid flow passage 822
and moreover circulating and collecting the cooling/heating medium
liquid, which has been stored in the liquid chamber 820 or the
like, through the liquid flow passage 822.
[0093] More specifically, as shown in FIG. 1, a continued
circulatory flow passage by the liquid flow passage 822 is formed
so that the cooling/heating medium liquid fed out from the chiller
unit 821 through the liquid flow passage 822 is supplied to the
liquid flow passage 823 within the lower electrode 7, the
cooling/heating medium liquid discharged from the liquid flow
passage 823 is supplied into the liquid flow passage 853 in the
upper vacuum vessel 801a through the liquid flow passage 822, and
that the cooling/heating medium liquid discharged from the liquid
flow passage 853 is supplied into the liquid chamber 820 through
the liquid flow passage 822, and the cooling/heating medium liquid
discharged from the liquid chamber 820 is returned again to the
chiller unit 821 through the liquid flow passage 822.
[0094] In FIG. 1, although the above description has been made on a
case where the temperature sensor 821b is placed near the outlet of
the cooling/heating medium liquid in the chiller unit 821, yet the
placement of the temperature sensor 821b is not limited only to
such a case. For example, the case may be that the temperature
sensor 821b is placed in the inner tank for the cooling/heating
medium liquid or the like in the chiller unit 821, or that the
temperature sensor 821b is placed within the liquid chamber 820 so
that the temperature of the cooling/heating medium liquid in the
liquid chamber 820 can be detected.
[0095] The cooling/heating medium liquid as shown above may be
selected from among, for example, fluorine inert oil typified by
Fluorinert or Galden (both trade name or trademark), silicone oil,
pure water, or insulating oils such as organic oils and fats. These
liquids, having electrical insulation property, have a feature that
there never occur short-circuits or current leakages even if they
make contact with the coil 805 which is formed of a conductive
material and to which RF power is applied. Further, those liquids,
because of each being also a dielectric, are enabled to enhance an
electrostatic field generated inside the processing chamber 803 via
the dielectric window 802. In addition, as the pure water mentioned
above, one having a resistivity of 1.times.10.sup.5
.OMEGA..multidot.cm or more is used to ensure its electrical
insulation property.
[0096] Also, in the plasma processing apparatus 800, at a junction
portion between the dielectric window 802 and the vacuum vessel
801, a junction portion between the vacuum vessel 801 and the
ground shield vessel 810, and a junction portion between the
aforementioned upper vacuum vessel 801a and the lower vacuum vessel
801b, O-rings 826, 827 and 828 are provided, respectively, so that
airtightness of the processing chamber 803 and the liquid chamber
820 is ensured.
[0097] Further, the plasma processing apparatus 800 is provided
with a control unit 90 for performing integrated control by
associating one with another of individual operation controls for
an RF power application operation by the coil-use RF power supply
806, an RF power application operation by the substrate-electrode
use RF power supply 8, and an evacuation operation by the vacuum
pump 13. By the integrated control performed by such a control unit
90, it is made implementable to perform plasma processing on the
substrate 9 placed on the lower electrode 7. In addition,
temperature adjustment operation for the cooling/heating medium
liquid by the chiller unit 821 (i.e., temperature control operation
by the temperature control unit 821a) is autonomously performed in
the chiller unit normally.
[0098] Now a method for performing plasma processing on the
substrate 9 by the plasma processing apparatus 800 having a
construction described above is explained. It is noted that
individual operations shown below are performed while associated
with one another as integrated control by the control unit 90.
[0099] Referring first to FIG. 1, the substrate 9 which is a
processing object to be plasma-processed is placed on the lower
electrode 7 in the vacuum vessel 801. Next, with the processing
chamber 803 closed, air or gas in the processing chamber 803 is
discharged through the gas outlet 13a and the gas discharge passage
13b by the vacuum pump 13, and subsequently a specified reactant
gas is supplied from an unshown reactant gas supply unit through
respective reactant gas supply holes 4 while interior of the
processing chamber 803 is maintained at a specified pressure by
adjusting the discharge flow rate with a discharge flow regulating
valve (not shown) provided on the way of the gas discharge passage
13b or other means.
[0100] Along with this, the cooling/heating medium liquid is
circulated through the liquid flow passage 822 so that the
cooling/heating medium liquid controlled to a specified temperature
by the chiller unit 821 is supplied sequentially to the liquid flow
passage 823 within the lower electrode 7, the liquid flow passage
853 within the upper vacuum vessel 801a, and the liquid chamber 820
and moreover the supply cooling/heating medium liquid is collected
to the chiller unit 821 through the liquid flow passage 822. By
this circulation of the cooling/heating medium liquid, in the
liquid chamber 820, the cooling/heating medium liquid is supplied
from the liquid flow passage 822 through the supply hole 810b into
the upper chamber 820a, this supplied cooling/heating medium liquid
then flowing through the through hole 850a into the lower chamber
820b and further circulated from the central side toward the
peripheral end portion side in the spiral liquid flow passage 854,
thus discharged through the discharge hole 810a to the liquid flow
passage 822. By the cooling/heating medium liquid being circulated
in the liquid chamber 820 as shown above, the coil holding plate
850 is biased toward the dielectric window 802 by the pressure
difference of the cooling/heating medium liquid supplied into the
upper chamber 820a and the lower chamber 820b.
[0101] The coil holding plate 850, while supported by the guide
bolts 851, is normally biased at its support position toward the
dielectric window 802 by the bias springs 852 so that the coil 805
is normally biased to the surface of the dielectric window 802.
However, there are some cases where the coil 805 is not completely
brought into contact with the surface of the dielectric window 802
due to manufacture precision or the like of the dielectric window
802 or the coil 805 or the coil holding plate 850. Yet, in such a
case, slightly moving the support position of the coil holding
plate 850 toward the dielectric window 802 side by biasing the coil
holding plate 851 with the liquid pressure of the cooling/heating
medium liquid having a force larger than the biasing force by the
bias spring 852 allows the coil 805 held to the lower face of the
coil holding plate 850 as viewed in the figure to be pressed
against the outer surface of the dielectric window 802 so as to be
brought into close contact therewith. Also, the pressing force of
the coil 805 against the dielectric window 802 can be made
generally uniform over the spiral-shaped contact surface by the
coil 805 being pressed via the coil holding plate 850 with the
pressure difference of the cooling/heating medium liquid supplied
to the upper chamber 820a and the lower chamber 820b. From such a
point of view, desirably, size and configuration of the through
hole 850a, the circulation flow rate of the cooling/heating medium
liquid and the like are determined so as to generate a pressure
difference that allows a necessary sufficient biasing force to be
generated.
[0102] While this state is maintained, a specified RF power is
applied from the coil-use RF power supply 806 to the coil 805 via
the matching box 818, the center electrode 814 and the application
terminal 816. As a result of this, an electromagnetic field is
imparted from the coil 805 via the dielectric window 802 to the
reactant gas in the processing chamber 803, so that electrons in
the reactant gas molecules are accelerated and a plasma is excited
to a plasma processing region R1 in the processing chamber 803.
When this occurs, RF power is applied simultaneously also to the
lower electrode 7 from the lower-electrode use RF power supply 8
via the matching box 19, thus' making it possible to control ion
energy that reaches the substrate 9. With the plasma excited in
this way, plasma processing such as etching, deposition or surface
reforming can be carried out on the substrate 9 placed on the lower
electrode 7.
[0103] Also, since the cooling/heating medium liquid adjusted to a
specified temperature by the chiller unit 821 is circulated through
the liquid flow passage 822, the dielectric window 802 and the coil
805 that are increased in temperature by the plasma processing can
be cooled and their respective temperatures can be maintained
within a specified temperature range while the plasma processing is
carried out.
[0104] It is noted here that the term "specified temperature range"
refers to such a temperature range that during plasma processing,
formation of a deposited film, which is a deposit, can be
suppressed and moreover the deposited film is prevented from coming
off (peeling off) due to keep the dielectric window 802 in high
temperature by reducing the amount of deposition of a thin film
formed by deposition of reaction products onto the inner surface of
the dielectric window 802.
[0105] Similarly, by the circulation of the cooling/heating medium
liquid, the temperature of the lower electrode 7 can be maintained
within a specified temperature range so that the substrate 9 to be
processed, which would be increased in temperature by the plasma
processing, is maintained at a suitable temperature during the
plasma processing. Further, by the circulation of the
cooling/heating medium liquid to the liquid flow passage 853 within
the upper vacuum vessel 801a, the temperature of the inner surface
of the processing chamber 803 can be maintained within a specified
temperature range so that plasma processing can be carried out
while the formation of the deposited film is suppressed.
[0106] Even in a plasma non-processing state, by the
cooling/heating medium liquid, which has been controlled to a
desired temperature by the chiller unit 821, to the liquid chamber
820, the temperature of the dielectric window 802 can be maintained
within the specified temperature range. In such a case, even in the
plasma non-processing state, the temperature of the dielectric
window 802 can be maintained within the specified temperature
range, so that temperature changes due to repetition of plasma
processing and plasma non-processing, i.e., the deposited film
formed on the dielectric window 802 can be prevented from
application of the heat cycle, so that the deposited film can be
prevented from peeling off due to the heat cycle.
[0107] According to the first embodiment, various working effects
as shown below can be obtained.
[0108] First, since the cooling/heating medium liquid controlled to
a desired temperature can be circulated in the liquid chamber 820
formed so as to be surrounded by the outer surface of the
dielectric window 802 and the inner surface of the ground shield
vessel 810, the outer surface of the dielectric window 802 with
which the cooling/heating medium liquid is put into contact can be
cooled or heated through the cooling/heating medium liquid. More
specifically, during the plasma processing, performing the cooling
for the dielectric window 802 that is increased in temperature
allows the temperature increase of the dielectric window 802 to be
suppressed. Such suppression of temperature increase makes it
possible to suppress discharge of gas components from the formed
deposited film into the processing chamber 803. Further, in the
plasma non-processing state, execution of heating on the dielectric
window 802, which is decreased in temperature, makes it possible to
suppress the temperature decrease of the dielectric window 802, so
that the dielectric window 802 can be maintained within the
specified temperature range. As a result of this, it becomes
possible to prevent the deposited film from absorbing gas
components in the processing chamber 803 or to prevent occurrence
of film deposition on the inner surface of the dielectric window
802 at starting of the next-time plasma processing.
[0109] Accordingly, discharge and adsorption of gas components
caused by repetition of plasma processing and non-processing can be
suppressed, thereby stabilizing the atmosphere of the plasma
processing region R1, so that a plasma processing of high
repeatability can be achieved. Also, it becomes possible to prevent
the deposited film stuck to the inner surface of the dielectric
window 802 from peeling off due to the heat cycle, which would lead
to failures of the processing-object substrate due to attaching
dust or particles.
[0110] Further, since the coil 805 is placed within the lower
chamber 820b of the liquid chamber 820 through which the
cooling/heating medium liquid is circulated and immersed in the
cooling/heating medium liquid as shown above, surface temperature
of the coil 805 as well as the dielectric window 802 can be
controlled concurrently. More specifically, during the plasma
processing, cooling the coil 805, which is increased in temperature
with application of RF power, via the cooling/heating medium liquid
allows the temperature increase to be suppressed. Actively lowering
the surface temperature of the coil 805 by such cooling can prevent
the processing-object substrate from being heated by infrared rays
radiated by the increased surface temperature of the coil 805.
Effects of the temperature adjustment for the dielectric window 802
and the coil 805 as shown above will never be impaired even if the
plasma processing time runs for 3 minutes to several hours, so that
temperature changes can be suppressed to the least.
[0111] Also, since the liquid chamber 820 is divided into the upper
chamber 820a and the lower chamber 820b by the coil holding plate
850, which holds the coil 805, and since the cooling/heating medium
liquid flow passage is so made up that the cooling/heating medium
liquid supplied to the upper chamber 820a is let to flow into the
lower chamber 820b, the coil holding plate 850 can be biased toward
the lower chamber 820b with the pressure difference of the
cooling/heating medium liquid supplied to the upper chamber 820a
and the lower chamber 820b so that the spiral coil 805 can be
pressed against the surface of the dielectric window 802 with a
uniform force so as to be brought into contact with the surface.
Thus, by bringing the coil 805 into close contact with the surface
of the dielectric window 802 like this, an RF high voltage applied
to the coil 805 can be dielectrically led to one surface of the
dielectric window 802 on the processing chamber 803 side, making it
easier to start or maintain discharge even with low pressure.
Accordingly, a strong electromagnetic field inducing effect by the
coil 805 can be produced in the processing chamber 803, making it
possible to provide a plasma processing apparatus which is capable
of implementing discharge with low pressure, obtaining high plasma
density and enhancing the etching rate.
[0112] Further, in the lower chamber 820b of the liquid chamber
820, the liquid flow passage 854 is formed between the
spiral-shaped coil 805 and so arranged that the cooling/heating
medium liquid is circulated from the center side toward the outer
peripheral end portion of the liquid flow passage 854. Thus, the
dielectric window 802 and the coil 805 can be cooled or heated
generally uniformly, allowing temperature control to be fulfilled
with high temperature controllability.
[0113] Further, in the case where, for example, fluorine inert oil
is used as the cooling/heating medium liquid described above, by
virtue of its having high electrical insulating property, there
occurs no current leakage or the like even if the coil 805 is
immersed directly in the fluorine inert oil, so that its safety is
ensured. Moreover, such fluorine inert oil, having a feature of a
wide temperature range for usability, can be said to be suitable
for temperature control of the dielectric window 802 or the like
from a temperature below the freezing point until a temperature
around 200.degree. C. Still, since the fluorine oil is also a
dielectric, a strong electrostatic field can be imparted into the
processing chamber 803 through the fluorine inert oil and the
dielectric window 802 with application of the RF power of the
immersed coil 805, so that a successful ignitability of plasma can
be obtained.
[0114] Further, since the spiral coil 805, the application terminal
816, the grounding terminal 817 and the center electrode 814 are
plated at their surfaces with gold, and not with silver that has
conventionally been used, corrosion and electrolytic corrosion can
be prevented from occurring to the surface of the coil 805 or the
like due to the application of the RF voltage and moisture contents
or the like of the cooling/heating medium liquid.
[0115] In the conventional plasma processing apparatus 500, 600,
cooling would be performed by mechanically ventilating air around
the coil 505, 605 (taking in fresh air from apparatus outside and
discharging the ambient air to apparatus outside). Instead, in the
plasma processing apparatus 800 of the first embodiment, the
cooling or the like of the coil 805 or the like is performed by
using the closed-system circulatory path which is formed so as to
be surrounded by the outer surface of the dielectric window 802 and
the ground shield vessel 810 and which is made up of the liquid
chamber 820 with the coil 805 placed inside, the liquid flow
passage 822 and the chiller unit 821. Accordingly, there never
occurs generation of ozone or the like or diffusion of the ozone to
the apparatus outside due to the cooling. Consequently, the health
problem of the operator can be improved, and acceleration of
deterioration of the apparatus and the component parts of
peripheral units due to the diffusion of ozone can be prevented
reliably.
Second Embodiment
[0116] It is noted here that the present invention is not limited
to the foregoing embodiment, and may be carried out in other
various aspects. For instance, FIG. 2 shows a schematic sectional
view of a plasma processing apparatus 100 which is an example of a
plasma processing apparatus according to the second embodiment of
the present invention. As shown in FIG. 2, the plasma processing
apparatus 100 is different in construction from the plasma
processing apparatus 800 of the first embodiment structurally in
terms of having not the disc-shaped dielectric window 802 but a
generally hemispherical-shell shaped dielectric window 2, but
generally similar in construction to the plasma processing
apparatus 800 in terms of the other structural components unrelated
to the form of the dielectric window 2. The following description
is given about this different construction. In addition, for an
easier understanding of the description, constituent parts similar
to those of the plasma processing apparatus 800 of the first
embodiment are designated by like reference numerals in the plasma
processing apparatus 100, and their description is omitted.
[0117] As shown in FIG. 2, the plasma processing apparatus 100 is
equipped with a vacuum vessel 1, and bell jar (an example of the
dielectric window) 2 formed of a generally hemispherical-shell
shaped (or dome-shaped) dielectric material (e.g., quartz) provided
so as to close an opening portion at the top of the vacuum vessel
1, where a processing chamber 3 is formed which is a space closed
by the vacuum vessel 1 and the bell jar 2 and a space where plasma
processing is performed.
[0118] Further, the plasma processing apparatus 100 has a plurality
of reactant gas supply holes 4 provided at upper portions of a side
face of the vacuum vessel 1, and a vacuum pump 13 which is
connected to a gas outlet 13a of the vacuum vessel 1 by means of a
discharge passage 13b and which serves for discharging air or gas
present in the vacuum vessel 1 (i.e., in the processing chamber 3).
Also, near the top of the bell jar 2, a coil 5 which is an example
of the plasma-exciting coil formed of a wire conductor in a spiral
shape is placed along an outer surface of the bell jar 2, and a
coil-use RF power supply 6 for applying RF power to the coil 5 via
a matching box 18 is provided outside the vacuum vessel 1. Further,
a lower electrode 7 is provided near a generally center in the
vacuum vessel 1, and a lower-electrode use RF power supply 8 for
applying RF power to the lower electrode 7 via a matching box 19 is
provided outside the vacuum vessel 1. A substrate 9 which is to be
subjected to plasma processing by the plasma processing apparatus
100 is held on the lower electrode 7 within the vacuum vessel
1.
[0119] Also, as shown in FIG. 2, a ground shield vessel 10 (an
example of the liquid storage vessel) formed of an electrical
conductor (a conductive material) of ground potential is fixedly
provided at an upper portion of the vacuum vessel 1 so as to cover
the entire coil 5 placed near the outer surface of the bell jar 2.
Further, near a generally center of this ground shield vessel 10, a
center electrode 14 connected to the coil-use RF power supply 6 via
the matching box 18 is fitted via an insulating bushing 15 so as
not to make electrical contact with the ground shield vessel 10.
This center electrode 14 is connected to an end portion of the
center portion of the spiral-shaped coil 5 via an application
terminal 16. Also, an end portion of the coil 5 on the outer
peripheral side is connected to the ground shield vessel 10 via a
grounding terminal 17, and the ground shield vessel 10 is connected
to a ground pole of the coil-use RF power supply 6. Thus, it is
implementable to apply RF power to the coil 5 from the coil-use RF
power supply 6 through the center electrode 14 and the application
terminal 16.
[0120] Further, as shown in FIG. 2, a space which is surrounded by
the inner side of the ground shield vessel 10, the outer surface
that is part of the bell jar 2 and the upper portion of the vacuum
vessel 1 and in which the coil 5 is placed inside is defined as a
liquid chamber 20, which allows a cooling/heating medium liquid to
be stored therein. Besides, a discharge hole 10a for the
cooling/heating medium liquid derived from the inside of the liquid
chamber 20 is formed near the upper portion of the ground shield
vessel 10, and a supply hole 10b of the cooling/heating medium
liquid to the inside of the liquid chamber 20 is formed near a
lower portion of the ground shield vessel 10.
[0121] These supply hole 10b and discharge hole 10a are connected
to an upper-portion side chiller unit 21 through a passage 22,
which is an example of the liquid flow passage, so that the
cooling/heating medium liquid is circulatable therethrough. The
upper-portion side chiller unit 21 is equipped with a cooling unit,
heating unit, a pump, a temperature control unit 21a for
controlling temperature of the cooling/heating medium liquid to a
desired temperature, and a temperature sensor 21b for detecting a
temperature of the cooling/heating medium liquid and outputting the
detected temperature to the temperature control unit 21a. The
upper-portion side chiller unit 21 constructed as shown above is
enabled to cool or heat the coil 5 and the bell jar 2 via the
cooling/heating medium liquid to maintain them at a desired
temperature, thus the upper-portion side chiller unit 21 being an
example of the liquid temperature adjusting unit for the
cooling/heating medium liquid.
[0122] Also, as shown in FIG. 2, a liquid flow passage 23 which
allows the cooling/heating medium liquid to pass therethrough is
formed inside the lower electrode 7, and a lower-portion side
chiller unit 25 is connected to the liquid flow passage 23 via a
passage 24. This lower-portion side chiller unit 25, which is
similar in construction to the upper-portion side chiller unit 21,
has a temperature control unit 25a, a temperature sensor 25b and
the like, and is enabled to maintain the lower electrode 7 at a
desired temperature by circulating within the liquid flow passage
23 the cooling/heating medium liquid that has been controlled to a
desired temperature through the cooling/heating medium liquid
passage 24.
[0123] Also, in the plasma processing apparatus 100, at a junction
portion between the bell jar 2 and the vacuum vessel 1 and a
junction portion between the vacuum vessel 1 and the ground shield
vessel 10, O-rings 26, 27 are provided, respectively, so that
airtightness of the processing chamber 3 and the liquid chamber 20
is ensured.
[0124] Further, the plasma processing apparatus 100 is provided
with a control unit 90 for performing integrated control by
associating one with another of individual operation controls for
the aforementioned respective constituent sections to thereby
control the plasma processing operation.
[0125] Here is described a working example showing various
conditions in such a plasma processing. For example, in a case
where via holes are etched to a depth of 100 .mu.m in an InP
(Indium-Phosphorus) substrate employed as the substrate, HI gas and
Ar gas as reactant gases are supplied into the processing chamber 3
at a supply flow rate of 100 sccm (100 cc/min. in a normal state),
and while the vacuum pressure is held at 1 Pa, an RF power of a
13.56 MHz frequency and a 1000 W output power is applied to the
coil 5 by the coil-use RF power supply 6, and an RF power of a
13.56 MHz frequency and a 100 W output power is applied to the
lower electrode 7 by the lower-electrode use RF power supply 8, by
which the plasma processing is performed on the substrate 9 held on
the lower electrode 7. In this case, with Galden used as the
cooling/heating medium liquid, this Galden is circulated at 2
l/min. into the liquid chamber 20 so that the temperature of the
bell jar 2 is held at about 100.degree. C., and likewise the lower
electrode 7 is held at about 50.degree. C. Under such conditions,
etching process on the substrate 9 can be carried out in a required
time of about 100 minutes.
[0126] In the plasma processing apparatus 100 of such a
construction, the coil 5 is placed in the liquid chamber 20 defined
by the bell jar 2 and the ground shield vessel 10, and the
cooling/heating medium liquid adjusted to a specified temperature
is circulated into the liquid chamber 20 during the plasma
processing. Thus, the temperature of the bell jar 2 and the coil 5
can be held within a specified temperature range, and working
effects similar to those by temperature adjustment of the
cooling/heating medium liquid in the first embodiment can be
obtained.
[0127] Indeed the method of the second embodiment as shown FIG. 2
is applicable to the plate-shaped dielectric window and the flat
spiral coil shown in the first embodiment of FIG. 1, but in
particular, a hemispherical bell jar 2 allows the bell jar to be as
small in thickness as possible even with a dielectric window made
of a dielectric material having a low heat conductivity (e.g.,
quartz), thus advantageous for cooling of the dielectric window.
Accordingly, from such a point of view, there is an advantage in
the method for controlling the temperature of the bell jar 2 by
forming the liquid chamber 20 by using the outside surface of the
bell jar 2.
[0128] The above description has been made on a case where the coil
5 is placed in the liquid chamber 20 surrounded by the generally
hemispherical-shell shaped bell jar 2 and the ground shield vessel
10, and where the cooling/heating medium liquid is circulated in
the liquid chamber 20. However, the construction of the plasma
processing apparatus 100 of this second embodiment is not limited
to such a one. For example, in a plasma processing apparatus having
a construction in which such a generally hemispherical-shell shaped
bell jar 2 is used, the construction that the coil is brought into
contact with the surface of the dielectric window is also
applicable as in the plasma processing apparatus of the first
embodiment. FIG. 3 is a schematic constructional view showing the
construction of a plasma processing apparatus 900 according to a
modification example of this second embodiment to which such a
construction as described above is applied. Also, FIG. 4 is a
sectional view taken along the line A-A in the plasma processing
apparatus 900 shown in FIG. 3. It is noted that like parts similar
in construction to those of the plasma processing apparatus 100
shown in FIG. 2 are designated by like reference numerals in the
plasma processing apparatus 900 shown in FIGS. 3 and 4, and their
description is omitted.
[0129] As shown in FIG. 3, in the plasma processing apparatus 900,
a cone-shaped spiral coil 905 having a rectangular cross section is
placed above the bell jar 2 within the liquid chamber 20, as viewed
in the figure. Also, as shown in FIGS. 3 and 4, the coil 905 is
held at a lower face of a coil holding member 950 having a planarly
generally X-like shape. Such holding is, for example, implemented
by an upper portion of the coil 905 being partly engaged with a
plurality of recess portions 950a formed at the lower face of the
coil holding member 950.
[0130] Further, the coil holding member 950 is supported to inside
of the ground shield vessel 10 via a plurality of guide bolts 951
at respective end portions of the X-like shape. The individual
guide bolts 951 are placed along the vertical direction in the
figure, and the coil holding member 950 is supported so as to be
movable along the respective guide bolts 951. Furthermore, a bias
spring 952 is attached to each of the guide bolts 951, and these
bias springs 952 have a function of biasing the coil holding member
950 toward the upper face side, as viewed in the figure, of the
bell jar 2 along the individual guide bolts 951. With such a
construction, the coil 905 held to the lower face of the coil
holding member 950 is normally pressed against the upper-side
surface of the bell jar 2, as viewed in the figure, so that the
coil 905 is maintained in close contact with the surface of the
bell jar 2.
[0131] In the plasma processing apparatus 900, since the
spiral-shaped coil 905 placed in the liquid chamber 20 is kept
normally in close contact with the upper-side surface of the bell
jar 2, as viewed in the figure, effecting the application of RF
power to the coil 905 in the plasma processing makes it possible to
generate a strong electromagnetic field inducing effect to a
processing chamber 3 side surface of the bell jar 2, so that the
working effect of allowing an easier start or holding of discharge
even with low pressure, similar to a working effect of the first
embodiment, can be obtained.
[0132] Although the configuration or placement of the grounding
terminal 17 and the application terminal 16 in FIG. 3 differs from
that of the plasma processing apparatus 100 of FIG. 2, yet such
configuration and placement are determined depending on the
configuration and placement of the coil 905, and there are no
substantial differences in function or the like. Besides, as shown
in FIG. 4, taking advantage of the coil member not being placed at
a center portion of the spiral-shaped coil 905, a through hole 950b
is formed at a center portion of the coil holding member 950, while
a through hole 10a and an observation-use window portion 10b
(formed of, for example, quartz glass material) are provided at a
position corresponding to the through hole 950b in the ground
shield vessel 10. Thus, the space within the processing chamber 3
can be made visually observable from the observation-use window
portion 10b through the through holes 10a, 950b and the bell jar
2.
Third Embodiment
[0133] Next, FIG. 5 is a schematic sectional view of a plasma
processing apparatus 200 according to a third embodiment of the
present invention. As shown in FIG. 5, the plasma processing
apparatus 200 is different in construction from the plasma
processing apparatus 100 of the second embodiment structurally in
terms of having not the generally hemispherical-shell shaped
dielectric window 2 but a generally plate-shaped dielectric window
202, but similar in construction to the plasma processing apparatus
100 in terms of the other structural components unrelated to the
form of the dielectric window 202. Further, as shown in FIG. 5, the
plasma processing apparatus 200 is similar in construction to the
plasma processing apparatus 800 in terms of having the generally
disc-shaped window 202, but different in terms of placing a liquid
flow passage 220 and a coil 205 in the inside of the dielectric
window 202. This different construction only is explained below. In
addition, for an easier understanding of the description,
constituent parts similar to those of the plasma processing
apparatus 100 of the second embodiment are designated by like
reference numerals in the plasma processing apparatus 200, and
their description is omitted. Besides, although the plasma
processing apparatus 200 is equipped with a control unit
(corresponding to the control unit 90) for performing integrated
control as in the plasma processing apparatus 100 of the second
embodiment, it is similar in construction and therefore its
representation is omitted in FIG. 5.
[0134] As shown in FIG. 5, the plasma processing apparatus 200 is
equipped with a generally disc-shaped dielectric window 202 which
is placed so as to close an opening portion at the top of the
vacuum vessel 1 and which is formed of a dielectric material, where
a processing chamber 203 is formed which is a space closed by the
dielectric window 202 and a space where plasma processing is
performed.
[0135] The dielectric window 202 is formed by mutual junction of an
upper-portion side dielectric plate 202a and a lower-portion side
dielectric plate 202b which are two generally disc-shaped
dielectric plates formed of the dielectric material. Further, at
the mutual junction surface of the upper-portion side dielectric
plate 202a and the lower-portion side dielectric plate 202b is
formed a continued recess portion having a generally concave-shaped
cross section so that their formation placement coincide with each
other. Then, by the upper-portion side dielectric plate 202a and
the lower-portion side dielectric plate 202b being joined to each
other, there is formed a continued liquid flow passage 220 for the
liquid which is enclosed by respective concave-shaped inner walls
and which allows the cooling/heating medium liquid to be circulated
therethrough. Such a liquid flow passage 220 is formed, for
example, so as to be spiraled from a generally center of the
dielectric window 202 about the center. Also, a supply hole 220a
for the cooling/heating medium liquid is formed at a center-side
end portion of the liquid flow passage 220 so as to extend through
the upper-portion side dielectric plate 202a, and a discharge hole
220b for the cooling/heating medium liquid is formed at an
spiral-periphery side end portion of the liquid flow passage 220 so
as to extend through the upper-portion side dielectric plate 202a.
It is noted that the liquid flow passage 220 is also an example of
the liquid chamber which is so formed that the inner wall of the
recess portion formed inside the dielectric window 202 serves as a
chamber wall and which is capable of storing the cooling/heating
medium liquid therein. Further, in the plasma processing apparatus
200 of this third embodiment, the lower-portion side dielectric
plate 202b is an example of the dielectric window while the
upper-portion side dielectric plate 202a is an example of the
liquid storage vessel, and moreover by the liquid storage vessel
being formed of a dielectric material, it can be said that one
dielectric window 202 in which the dielectric window and the liquid
storage vessel are integrated together is formed.
[0136] Also, the supply hole 220a and the discharge hole 220b of
the liquid flow passage 220 are communicated with the upper-portion
side chiller unit 21 through a passage 222, which is an example of
the liquid flow passage. Thus, the cooling/heating medium liquid
can be circulated so that the cooling/heating medium liquid
controlled to a desired temperature by the upper-portion side
chiller unit 21 is supplied into the liquid flow passage 220
through the passage 222 and the supply hole 220a, and moreover that
the cooling/heating medium liquid within the liquid flow passage
220 is collected to the upper-portion side chiller unit 21 through
the discharge hole 220b and the passage 222.
[0137] Also, inside the liquid flow passage 220 formed into the
generally spiral shape is formed the coil 205 which is an example
of a plasma-exciting coil formed of a conductor wire continuously
so as to generally coincide with the generally spiral-shaped
configuration. A generally spiral-center side end portion of the
coil 205 is connected via a matching box 218 to a coil-use RF power
supply 206 placed outside the apparatus, and a generally
spiral-periphery side end portion of the coil 205 is connected to
the grounding terminal outside the apparatus.
[0138] At a junction portion between the dielectric window 202 and
the vacuum vessel 1, an O-ring 226 is provided to ensure the
airtightness inside the processing chamber 203. Further, in order
to securely fix (releasably fix) the dielectric window 202 to the
vacuum vessel 1, the dielectric window 202 is fixed at its end
portion to the top of the vacuum vessel 1 with a presser metal
fitting 228, which is a fixing member. Besides, a ground shield 210
formed of a conductive material is attached to the top of the
vacuum vessel 1 so as to cover the outer surface of the dielectric
window 202 as well as the space near the surface.
[0139] In the plasma processing apparatus 200 of such a
construction, operation for performing plasma processing on the
substrate 9 placed on the lower electrode 7 is similar to those of
the plasma processing apparatus 800 of the first embodiment and the
plasma processing apparatus 100 of the second embodiment. More
specifically, the dielectric window 202 and the coil 205 can be
controlled to a desired temperature by circulating the
cooling/heating medium liquid so that the cooling/heating medium
liquid controlled to a desired temperature is supplied from the
supply hole 220a via the passage 222 to the liquid flow passage 220
formed inside the dielectric window 202 and that the
cooling/heating medium liquid supplied to the liquid flow passage
220 is discharged from the discharge hole 220b to the passage
222.
[0140] Also, the dielectric window 202 having such a liquid flow
passage 220 inside thereof can be joined together by bonding the
upper-portion side dielectric plate 202a, in which the
concave-shaped recess portion is formed, and the lower-portion side
dielectric plate 202b to each other by means of adhesive or the
like so that their mutual recess portions coincide with each other.
Such adhesive may be given, preferably, by rubber-based adhesives
capable of maintaining their elasticity after setting, for example,
thermosetting silicone rubber based adhesives. Instead of joining
with the use of adhesive as shown above, the upper-portion side
dielectric plate 202a and the lower-portion side dielectric plate
202b can be joined together by providing a high-precision plane on
the mutual junction surfaces of the upper-portion side dielectric
plate 202a and the lower-portion side dielectric plate 202b by then
evacuating the interior of the liquid flow passage 220 with their
junction surfaces bonded together, or by pressing each other, and
further by heating to high temperature those respective junction
surfaces which are kept in secure close contact with each other, by
which the upper-portion side dielectric plate 202a and the
lower-portion side dielectric plate 202b are joined together by
high-temperature interatomic junction.
[0141] According to the third embodiment, in a case where the
dielectric window 202 is generally plate shaped, the liquid flow
passage 220 is formed in the dielectric window 202, and the coil
205 is placed within this liquid flow passage 220. Thus, the
surfaces of the dielectric window 202 and the coil 205 can be
controlled to a desired temperature by circulating the
cooling/heating medium liquid controlled to a desired temperature
into the liquid flow passage 220, so that working effects similar
to those of the second embodiment can be obtained.
[0142] As shown above, the coil 205 is placed in the liquid flow
passage 220 formed inside the dielectric window 202. As a result of
this, the distance between the coil 205 and the lower surface of
the dielectric window 202 (the upper surface of the processing
chamber 203) can be reduced, and therefore reliable temperature
control of the dielectric window 202 and the coil 205 can be
achieved while a higher plasma-exciting power is obtained.
[0143] Also, even in the case where the dielectric window 202 is
made generally plate-shaped and formed large in thickness in order
to obtain enough strength to withstand the atmospheric pressure as
shown above, the liquid flow passage (liquid chamber) 220 and the
coil 205 can be placed at a position close to the
processing-chamber side surface of the dielectric window 202, so
that reliable cooling of the dielectric surface can be
achieved.
[0144] Further, in the plasma processing apparatus 200 of the third
embodiment, since the liquid flow passage 220 is formed in a
generally spiral shape inside the dielectric window 202, there is
an advantage that the surface area for heat conduction can be made
relatively large and the temperature controllability can be made
successful. Furthermore, the amount of the cooling/heating medium
liquid can be reduced, so that it is possible to come into being
reducing in cost, downsizing, and saving power for temperature
control for the apparatus.
Fourth Embodiment
[0145] Next, FIG. 6 is a schematic sectional view of a plasma
processing apparatus 300 according to a fourth embodiment of the
invention. In the following description, component parts similar in
construction to those of the plasma processing apparatus 100 of the
second embodiment are designated by like reference numerals, and
their description is omitted.
[0146] As shown in FIG. 6, the plasma processing apparatus 300 is
similar in construction to the plasma processing apparatus 100 of
the second embodiment in that a liquid chamber 320 formed so as to
be surrounded by the outer surface of a bell jar 2 and the inner
surface of a ground shield vessel 310 is provided above the
generally hemispherical-shell shaped or generally dome-shaped bell
jar 2, but differs from the second embodiment in that the
cooling/heating medium liquid stored in the liquid chamber 320 is
not circulated through the chiller unit 325. This different
construction only is explained below.
[0147] As shown in FIG. 6, the liquid chamber 320 is communicated
with apparatus outside (i.e., atmospheric air) via a reserve tank
330 formed upward of the liquid chamber 320, and a cooling/heating
medium liquid is stored inside the liquid chamber 320. It is noted
that this reserve tank 330 has a role for absorbing and adjusting
volumetric changes (or a little evaporation) due to temperature
changes of the cooling/heating medium liquid stored inside the
liquid chamber 320.
[0148] Further, on the perimeter of the liquid chamber 320, i.e.,
on the outer peripheral portion of the ground shield vessel 310, an
outer-peripheral side cooling/heating medium liquid flow passage
331 is formed so as to surround the liquid chamber 320. This
outer-peripheral side cooling/heating medium liquid flow passage
331 is enabled to cool or heat the cooling/heating medium liquid
stored in the neighbored liquid chamber 320 by a
temperature-controlled secondary cooling/heating medium liquid (an
example of fluid stored so as to be separable from the
cooling/heating medium liquid) being circulated inside the
outer-peripheral side cooling/heating medium liquid flow passage
331, thus being an example of a heat exchanger section. Also, in
this outer-peripheral side cooling/heating medium liquid flow
passage 331 are formed a supply hole 331a for supplying the
secondary cooling/heating medium liquid as well as a discharge hole
331b for discharging the same. The supply hole 331a is communicated
with the liquid flow passage 23 of the lower electrode 7 via a
cooling/heating medium liquid passage 322, and the liquid flow
passage 23 is communicated with a chiller unit 325 via a
cooling/heating medium liquid passage 24. On the other hand, the
discharge hole 331b is communicated with the chiller unit 325 via a
cooling/heating medium liquid passage 332.
[0149] With such a construction, it is made implementable to
control the temperature of the lower electrode 7 by circulating the
secondary cooling/heating medium liquid, which is controlled to a
desired temperature by the chiller unit 325, along the liquid flow
passage 23 of the lower electrode 7 through the cooling/heating
medium liquid passage 24. Further, the cooling/heating medium
liquid stored in the liquid chamber 320 can be controlled to a
desired temperature by supplying the secondary cooling/heating
medium liquid from the liquid flow passage 23 of the lower
electrode 7 through the cooling/heating medium liquid passage 322
and the supply hole 331a into the outer-peripheral side
cooling/heating medium liquid flow passage 331, and by circulating
the supplied secondary cooling/heating medium liquid through the
discharge hole 331b and the cooling/heating medium liquid passage
332 to the chiller unit 325.
[0150] Besides, the ground shield vessel 310 is equipped with a
stirrer 333 for stirring the cooling/heating medium liquid stored
in the liquid chamber 320, thus making it possible to uniformize
the temperature of the cooling/heating medium liquid stored in the
liquid chamber 320. Therefore, with the use of the cooling/heating
medium liquid that is uniformized and temperature-controlled, it is
made possible to control the surface temperature of the bell jar 2
and the coil 5.
[0151] The cooling/heating medium liquid to be stored in the liquid
chamber 320 is given by using fluorine oil or silicone oil having
electrical insulation property as in the first embodiment in view
of being brought into direct contact with the coil 5. On the other
hand, the secondary cooling/heating medium liquid to be circulated
to the outer-peripheral side cooling/heating medium liquid flow
passage 331 may be given by using a liquid which is commonly used
as a cooling/heating medium such as tap water or ethylene glycol
because of not being brought into contact with the coil 5 and
therefore not being required to have electrical insulation
property.
[0152] In this fourth embodiment, the chiller unit 325, which is
equipped with a refrigerator (cooling unit) and a heater (heating
unit), which is an example of the liquid temperature adjusting
unit, is enabled to indirectly adjust the temperature of the
cooling/heating medium liquid stored in the liquid chamber 320 with
the use of the secondary cooling/heating medium liquid.
[0153] According to the fourth embodiment, in addition to the
working effects of the second embodiment, it is further made
possible to perform temperature control of the cooling/heating
medium liquid stored in the liquid chamber 320 with the use of the
secondary cooling/heating medium liquid indirectly
temperature-controlled by the chiller unit 325 to thereby perform
the temperature control of the bell jar 2 and the coil 5.
Therefore, it is made possible to employ a common-use relatively
low-price chiller unit 325 for water or ethylene glycol without
using a relatively high-price chiller unit for fluorine oils and
silicone oil, so that the plasma processing apparatus 300 can be
reduced in cost.
[0154] Besides, by the provision of the stirrer 333 in the liquid
chamber 320, it is made possible to accelerate the heat exchange
with the secondary cooling/heating medium liquid present in the
flow passage 331 and to uniformize the temperature of the
cooling/heating medium liquid present in the liquid chamber 320, so
that the temperature controllability of the bell jar 2 and the coil
5 can be improved.
Fifth Embodiment
[0155] Next, FIG. 7 is a schematic sectional view of a plasma
processing apparatus 400 according to a fifth embodiment of the
invention. As shown in FIG. 7, the plasma processing apparatus 400
is similar in construction to the plasma processing apparatus 300
of the fourth embodiment except for a construction for heating or
cooling the cooling/heating medium liquid stored in a liquid
chamber 420 formed so as to be surrounded by the bell jar 2 and a
ground shield vessel 410. This different construction only is
explained below.
[0156] As shown in FIG. 7, a multiplicity of cooling fins 410a are
formed on a generally cylindrical-shaped outer peripheral side wall
of the ground shield vessel 410 in the plasma processing apparatus
400. Also, a cooling fan 440 for blowing air to the cooling fins
410a is provided outside the ground shield vessel 410. It is noted
that in this fourth embodiment, the cooling fins 410a and the
cooling fan 440 are an example of the air cooling unit.
[0157] Further, a heater 441 for heating the cooling/heating medium
liquid stored in the liquid chamber 420 as well as a stirrer 333
are provided inside the ground shield vessel 410, i.e., in the
liquid chamber 420.
[0158] As shown above, for the cooling/heating medium liquid stored
in the liquid chamber 420, the cooling fins 410a and the cooling
fan 440 are provided as a cooling unit, the heater 441 is provided
as a heating unit, and the stirrer 333 for uniformization of
temperature of the internal liquid is provided. Thus, it is made
possible to control the temperature of the cooling/heating medium
liquid with the use of the cooling unit and the heating unit under
their control. That is, in this fourth embodiment, the cooling fins
410a, the cooling fan 440, the heater 441 and the stirrer 333 serve
as an example of the liquid temperature adjusting unit.
[0159] According to the fifth embodiment, temperature control of
the cooling/heating medium liquid stored in the liquid chamber 420
can be achieved without using any chiller unit but with the
constructional provision of the cooling fins 410a, the cooling fan
440, the heater 441 and the stirrer 333. This contributes to a
downsizing of the apparatus as well as a simplification of the
construction, so that manufacturing cost for the apparatus can be
reduced and downsizing of the apparatus can be fulfilled.
Sixth Embodiment
[0160] Next, FIG. 8 is a schematic sectional view showing a
schematic construction of a plasma processing apparatus 700
according to a sixth embodiment of the invention. As shown in FIG.
8, the plasma processing apparatus 700 is similar in construction
to the plasma processing apparatus 400 of the fifth embodiment
except that there is provided no externally cooling mechanism for
the cooling/heating medium liquid stored in a liquid chamber 720
formed so as to be surrounded by the bell jar 2 and a ground shield
vessel 710 and that there is a difference in the construction of
supply and discharge holes for the liquid. This different
construction only is explained below.
[0161] As shown in FIG. 8, the plasma processing apparatus 700 is
provided with a liquid chamber 720 formed so as to be surrounded by
the bell jar 2 and the ground shield vessel 710, and the
cooling/heating medium liquid is stored in the liquid chamber 720.
Also, a vapor discharge hole 710a (an example of the discharge
portion for liquid vapor) for discharging the vapor of the
cooling/heating medium liquid vaporized within the liquid chamber
720 is formed at an upper portion of the ground shield vessel 710,
and the vapor discharge hole 710a is connected to open air or an
evacuator (not shown) through the vapor discharge hole 710a. The
ground shield vessel 710 is provided with a cooling/heating medium
liquid supply pipe 740 (an example of the supply portion) for
supplying the cooling/heating medium liquid into the liquid chamber
720, and it is made possible to supply the cooling/heating medium
liquid from the cooling/heating medium liquid supply pipe 740 so
that the cooling/heating medium liquid stored in the liquid chamber
720 can be maintained at a specified liquid level. Within the
liquid chamber 720, the heater 441 and the stirrer 333 are provided
as in the plasma processing apparatus 400.
[0162] The cooling/heating medium liquid in the liquid chamber 720
is selected as one which is safe in electrical insulation property
and which has a boiling point around a desired temperature
(adjustment temperature) at which the bell jar 2 and the coil 5 to
be maintained (adjusted). For example, when the desired temperature
is around 100.degree. C., pure water may be used appropriately.
When the desired temperature is a cryogenic temperature, liquid
nitrogen or liquefied carbonic acid gas may be used. For
temperatures around normal temperature, chlorofluorocarbon based
ones may be used.
[0163] By such a construction of the plasma processing apparatus
700, the amount of heat derived from the bell jar 2 and the coil 5
is imparted to (or lost from) the cooling/heating medium liquid in
contact therewith, causing the cooling/heating medium liquid to be
vaporized as vapor foams 750 with the amount of heat as latent heat
of vaporization, by which the surfaces of the bell jar 2 and the
coil 5 can be cooled. The vapor of the cooling/heating medium
liquid is discharged from the vapor discharge hole 710a outside the
liquid chamber 720. Also, the amount of storage of the
cooling/heating medium liquid decreased by this vapor discharge is
compensated by supply from the cooling/heating medium liquid supply
pipe 740. Also, for such supply of the cooling/heating medium
liquid, the liquid chamber 720 is equipped with a sensor or the
like (not shown) for detecting the liquid level of the
cooling/heating medium liquid.
[0164] In addition, instead of using the heater 441 as the heating
unit for the cooling/heating medium liquid as shown above, the
heating of the bell jar 2 can be fulfilled via the cooling/heating
medium liquid by heating the cooling/heating medium liquid stored
in the liquid chamber 720 to a desired temperature with slight RF
power applied to the coil 5. Further, for heating the bell jar 2
preparatorily to a desired temperature, the heater 441 and the
stirrer 333 can be used as in the fifth embodiment.
[0165] According to the sixth embodiment, there can be provided an
apparatus which has a sufficient cooling function, and which is
simplified in the construction of the plasma processing apparatus
700 and further which is low in cost.
[0166] Although the plasma processing apparatuses of the foregoing
individual embodiments have been described on a case where the coil
to be placed in the liquid chamber is entirely immersed in the
cooling/heating medium liquid supplied into the liquid chamber, the
present invention is not limited only to such a case. Instead of
such a case, the case may be that only part of the coil is immersed
in the cooling/heating medium liquid.
[0167] Taking the plasma processing apparatus 700 of the sixth
embodiment as an example, even in the case where, for example as
shown in FIG. 9, the storage amount of the cooling/heating medium
liquid is less than that of the state shown in FIG. 8 and part of
the coil 5 is exposed from the liquid level of the stored
cooling/heating medium liquid in the liquid chamber 720, the
temperature control for the bell jar 2, which is of higher
necessity, can reliably be fulfilled if the entire upper-face side
surface of the bell jar 2, as viewed in the figure, is immersed in
the cooling/heating medium liquid, so that the working effects by
the sixth embodiment can be obtained. However, it is desirable that
the entirety of the coil 5 is immersed in the cooling/heating
medium liquid from the viewpoint of reliably fulfilling the
temperature control of the coil 5 in addition to the bell jar
2.
[0168] Also, Although the foregoing individual embodiments have
been described on a case where the dielectric window and the coil
is cooled and heated by the cooling/heating medium liquid, the
present invention is not limited only to such a case only. Even
when only the cooling of the dielectric window by the
cooling/heating medium liquid is performed during plasma
processing, the present invention can be applied to obtain the
working effects.
[0169] Furthermore, although the foregoing embodiments have been
described on the assumption that so-called ICP (Inductively Coupled
Plasma) excitation coil (or antenna) is shown in the drawings as
the plasma-exciting coil or electrode, yet similar working effects
can be obtained even with a CCP (capacitively coupled plasma)
excitation electrode installed in the liquid chamber instead.
[0170] It is to be noted that, by properly combining the arbitrary
embodiments of the aforementioned various embodiments, the effects
possessed by them can be produced.
[0171] Although the present invention has been fully described in
connection with the preferred embodiments thereof with reference to
the accompanying drawings, it is to be noted that various changes
and modifications are apparent to those skilled in the art. Such
changes and modifications are to be understood as included within
the scope of the present invention as defined by the appended
claims unless they depart therefrom.
[0172] The disclosure of Japanese Patent Application No.
2003-389251 filed on Nov. 19, 2003, including specification,
drawings and claims are incorporated herein by reference in its
entirety.
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