U.S. patent application number 11/769854 was filed with the patent office on 2007-12-13 for plasma processing apparatus and cleaning method thereof.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Yoshimitsu Kon, Hideaki TANAKA.
Application Number | 20070284043 11/769854 |
Document ID | / |
Family ID | 35512687 |
Filed Date | 2007-12-13 |
United States Patent
Application |
20070284043 |
Kind Code |
A1 |
TANAKA; Hideaki ; et
al. |
December 13, 2007 |
PLASMA PROCESSING APPARATUS AND CLEANING METHOD THEREOF
Abstract
A plasma processing apparatus includes a mounting table for
mounting thereon an object to be processed, an electrode connected
to a high frequency power supply, an electrical state setting unit
for setting an electrical state of the mounting table to a
conducting state or a floating state, and a controller for
controlling the high frequency power supply to apply a high
frequency power to the electrode and controlling the electrical
state setting unit to set an electrical state of the mounting table
to a floating state. Further, a radical produced from a cleaning
gas by the applied high frequency power is made to have a contact
with the mounting table.
Inventors: |
TANAKA; Hideaki;
(Nirasaki-shi, JP) ; Kon; Yoshimitsu;
(Nirasaki-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
35512687 |
Appl. No.: |
11/769854 |
Filed: |
June 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11171186 |
Jul 1, 2005 |
|
|
|
11769854 |
Jun 28, 2007 |
|
|
|
60598424 |
Aug 4, 2004 |
|
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Current U.S.
Class: |
156/345.28 ;
118/723R |
Current CPC
Class: |
H01J 37/32522 20130101;
B08B 7/0035 20130101; H01J 37/32862 20130101; H01J 37/32082
20130101 |
Class at
Publication: |
156/345.28 ;
118/723.00R |
International
Class: |
C23F 1/04 20060101
C23F001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 5, 2004 |
JP |
2004-197948 |
Claims
1. A plasma processing apparatus, comprising: a mounting table for
mounting thereon an object to be processed; an electrode connected
to a high frequency power supply; an electrical state setting unit
for setting an electrical state of the mounting table to a
conducting state or a floating state; and a controller for
controlling the high frequency power supply to apply a high
frequency power to the electrode and controlling the electrical
state setting unit to set an electrical state of the mounting table
to a floating state, wherein a radical produced from a cleaning gas
by the applied high frequency power is made to have a contact with
the mounting table
2. The plasma processing apparatus of claim 1, wherein the plasma
processing apparatus includes an accommodation chamber for
accommodating therein the mounting table and the electrode; the
electrode and the mounting table are respectively disposed in an
upper portion and a lower portion of the accommodation chamber; and
the mounting table is connected to another high frequency power
supply.
3. The plasma processing apparatus of claim 1, wherein the object
is a circular plate having a diameter of 300 mm, and a distance
between the mounting table and the electrode is approximately 35
mm.
4. The plasma processing apparatus of claim 1, wherein the object
is a circular plate having a diameter of 200 mm, and a distance
between the mounting table and the electrode is approximately 70
mm.
5. The plasma processing apparatus of claim 2, wherein the object
is a circular plate having a diameter of 300 mm, and a distance
between the mounting table and the electrode is approximately 35
mm.
6. The plasma processing apparatus of claim 2, wherein the object
is a circular plate having a diameter of 200 mm, and a distance
between the mounting table and the electrode is approximately 70
mm.
7-9. (canceled)
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This document claims priority to Japanese Patent Application
Number 2004-197948, filed Jul. 5, 2004 and U.S. Provisional
Application No. 60/598,424, filed Aug. 4, 2004, the entire content
of which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a plasma processing
apparatus and a cleaning method thereof; and, more particularly, to
a plasma processing apparatus including a mounting table for
mounting thereon an object to be processed and a cleaning method
thereof.
BACKGROUND OF THE INVENTION
[0003] Conventionally, a parallel plate type plasma processing
apparatus 40 shown in FIG. 4 is used as one of apparatuses for
performing a plasma processing such as a film forming process or an
etching process on a wafer W serving as an object to be processed.
The plasma processing apparatus 40 includes an upper electrode 42
and a susceptor 43, which are disposed in parallel to face each
other, having a specified distance D between electrodes in a
chamber 41, and a vacuum exhaust port 44 for maintaining a fixed
pressure in the chamber 41.
[0004] In the plasma processing apparatus 40, the upper electrode
42 is connected to a high frequency power supply 45, and the
susceptor 43 is connected to a high frequency power supply 46,
thereby serving as a lower electrode. Further, the upper electrode
42 has a plurality of gas ventholes 47 on its surface facing the
susceptor 43. The susceptor 43 has thermally conductive gas supply
holes 48 and a thermally conductive gas supply groove (not shown)
on its surface facing the upper electrode 42, i.e., the surface for
mounting the wafer W thereon.
[0005] In the plasma processing apparatus 40, a processing gas is
introduced into the chamber 41 and high frequency powers are
respectively applied to the upper electrode 42 and the susceptor 43
to generate a plasma from the processing gas, whereby a desired
plasma processing is performed on the wafer W. Here, for example,
an oxide film or the like is deposited on the susceptor 43 as well
as the wafer W in a film forming process, and reaction products are
deposited on the susceptor 43 in an etching process. Such reaction
products deposited on the susceptor 43 will be attached to the
wafer W as foreign substances, which should be regularly removed
from the susceptor 43.
[0006] A physical etching (sputtering) method has been known as a
cleaning method for removing the deposited reaction products from
the susceptor 43. In the physical etching method, the wafer W is
unloaded from the susceptor 43 and, then, a cleaning gas is ionized
to generate ions between the upper electrode 42 and the susceptor
43. At the same time, the susceptor 43 becomes self-biased by
applying a high frequency power thereto, whereby the ions collide
with the susceptor 43. Accordingly, the deposited reaction products
are removed from the susceptor 43 by impact forces of the colliding
ions, and the removed reaction products (hereinafter, referred to
as "dust") are discharged through a vacuum exhaust port 44.
[0007] Since the dust left in the chamber 41 will be attached to
the wafer W, it is necessary to reduce dust generation. As a method
for rapidly cleaning the susceptor 43 and reducing the dust
generation, there is used a method of setting a distance D between
the electrodes in two ways: in a first step when the distance D
between the electrodes is set to be small, a high frequency power
is applied only to the upper electrode 42 to perform an etching
(narrow gap etching), and in a second step when the distance D
between the electrodes is set to be large, high frequency powers
are applied to both the upper electrode 42 and the susceptor 43 to
perform the etching (wide gap etching) (e.g., see Reference 1).
Even in the method of setting a distance D between the electrodes
in two ways, the deposited reaction products are removed from the
susceptor 43 by the impact forces of the colliding ions.
[0008] [Reference 1] Japanese Patent Laid-open Publication No.
H8-176828
[0009] However, when the deposited reaction products are removed
from the susceptor 43 by the impact forces of the colliding ions,
the ions also erode the susceptor 43. Accordingly, surface
roughness becomes worsened on the susceptor 43's surface facing the
upper electrode 42, i.e., the surface for mounting the wafer W
thereon, and it becomes difficult to seal a thermally conductive
gas supplied through the thermally conductive gas supply holes 48
and the thermally conductive gas supply groove, thereby resulting
in an increase in a leak rate of a thermally conductive gas between
the wafer W and the susceptor 43. If the leak rate of the thermally
conductive gas is increased, while a plasma processing is performed
on the wafer W, temperature nonuniformity will be developed on the
surface of the wafer W, so that the plasma processing cannot be
performed uniformly on the wafer W.
SUMMARY OF THE INVENTION
[0010] It is, therefore, an object of the present invention to
provide a plasma processing apparatus and a cleaning method thereof
capable of removing reaction products deposited on a mounting table
therefrom without increasing a leak rate of a thermally conductive
gas.
[0011] In accordance with a first aspect of the present invention,
there is provided a plasma processing apparatus, including a
mounting table for mounting thereon an object to be processed; an
electrode connected to a high frequency power supply; an electrical
state setting unit for setting an electrical state of the mounting
table to either a conducting state or a floating state; and a
controller for controlling the high frequency power supply to apply
a high frequency power to the electrode and controlling the
electrical state setting unit to set an electrical state of the
mounting table to the floating state, wherein a radical produced
from a cleaning gas by the applied high frequency power is made to
have a contact with the mounting table. Here, since the electrical
state of the mounting table is set to the floating state, a
self-bias is not induced in the mounting table. Accordingly, a
kinetic energy of an ion colliding with the mounting table is
small, whereby erosion of the mounting table does not happen. On
the other hand, a radical making a contact with the mounting table
reacts chemically with the deposited reaction product to thereby
remove it from the top surface of mounting table. Therefore, the
reaction products deposited on mounting table can be removed
without an increase in a leak rate of a thermally conductive
gas.
[0012] Preferably, the plasma processing apparatus includes an
accommodation chamber for accommodating therein the mounting table
and the electrode, the electrode and the mounting table are
respectively disposed in an upper portion and a lower portion of
the accommodation chamber, and the mounting table is connected to
another high frequency power supply. Accordingly, a desired plasma
processing can be performed on the object and, at the same time,
the mounting table can be properly cleaned.
[0013] Preferably, in the plasma processing apparatus, the object
is a circular plate having a diameter of 300 mm, and a distance
between the mounting table and the electrode is approximately 35
mm. When a distance between the mounting table and the electrode is
set to approximately 35 mm in a plasma processing apparatus for
performing a plasma processing on an object which is shaped as a
circular plate having a diameter of 300 mm, surface roughness is
not getting worsened on an object mounting surface of the mounting
table by ions' collision. Therefore, it can definitely prevent an
increase in the leak rate of the thermally conductive gas.
[0014] Preferably, in the plasma processing apparatus, the object
is a circular plate having a diameter of 200 mm, and a distance
between the mounting table and the electrode is approximately 70
mm. When a distance between the mounting table and the electrode is
set to approximately 70 mm in a plasma processing apparatus for
performing a plasma processing on an object which is shaped as a
circular plate having a diameter of 200 mm, the surface roughness
is not getting worsened on an object mounting surface of the
mounting table by ions' collision. Therefore, it can definitely
prevent an increase in the leak rate of the thermally conductive
gas.
[0015] In accordance with a second aspect of the present invention,
there is provided a cleaning method including the steps of applying
a high frequency power to an electrode; setting an electrical state
of a mounting table to a floating state; and making a radical
produced from a cleaning gas by the applied high frequency power
have a contact with the mounting table. When a high frequency power
is applied to the electrode, ions and radicals are produced from
the cleaning gas near the electrode. Here, if the electrical state
of the mounting table is set to a floating state, a self-bias is
not induced in the mounting table. Accordingly, the energy of an
ion colliding with the mounting table is small, whereby erosion of
the mounting table does not happen. On the other hand, a radical
made to have a contact with the mounting table reacts chemically
with a deposited reaction product to thereby remove it from the top
surface of mounting table. Therefore, the reaction products
deposited on the mounting table can be removed without an increase
in the leak rate of the thermally conductive gas.
[0016] In the cleaning method of the plasma processing apparatus,
preferably, the object is a circular plate having a diameter of 300
mm, and a distance between the mounting table and the electrode is
approximately 35 mm. When a distance between the mounting table and
the electrode is set to approximately 35 mm in a plasma processing
apparatus for performing a plasma processing on an object which is
shaped as a circular plate having a diameter of 300 mm, the surface
roughness is not getting worsened on an object mounting surface of
the mounting table by ions, collision. Therefore, it can definitely
prevent an increase in the leak rate of the thermally conductive
gas.
[0017] In the cleaning method of the plasma processing apparatus,
preferably, the object is a circular plate having a diameter of 200
mm, and a distance between the mounting table and the electrode is
approximately 70 mm. When a distance between the mounting table and
the electrode is set to approximately 70 mm in a plasma processing
apparatus for performing a plasma processing on an object which is
shaped as a circular plate having a diameter of 200 mm, the surface
roughness is not getting worsened on an object mounting surface of
the mounting table by ions' collision. Therefore, it can definitely
prevent an increase in the leak rate of the thermally conductive
gas.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The above and other objects and features of the present
invention will become apparent from the following description of
preferred embodiments, given in conjunction with the accompanying
drawings, in which:
[0019] FIG. 1 is a vertical section showing a schematic
configuration of a plasma processing apparatus in accordance with a
preferred embodiment of the present invention;
[0020] FIG. 2 is a flow chart of cleaning processing of a plasma
processing apparatus, that is performed in the plasma processing
apparatus of FIG. 1;
[0021] FIG. 3 is a graph showing a relationship between the total
application time of a high frequency power and the leak rate of He
gas in an etching process performed after performing the cleaning
processing of FIG. 2; and
[0022] FIG. 4 shows a schematic configuration of a conventional
parallel plate type plasma processing apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] A preferred embodiment of the present invention will now be
described with reference to the accompanying drawings.
[0024] Hereinafter, there will be a plasma processing apparatus in
accordance with the preferred embodiment of the present
invention.
[0025] FIG. 1 is a vertical section showing a schematic
configuration of the plasma processing apparatus in accordance with
the preferred embodiment of the present invention.
[0026] A plasma processing apparatus 1 shown in FIG. 1, which is
used as an etching processing apparatus for performing an etching
process on a wafer (object to be processed) W, includes a
cylindrical chamber (accommodation chamber) 10 made of metal such
as aluminum or stainless steel, and a cylindrical susceptor
(mounting table) 11 serving as a stage for mounting thereon the
wafer W having a diameter of, e.g., 300 mm in the chamber 10.
[0027] Formed between the sidewall of the chamber 10 and the
susceptor 11 is a gas exhaust path 12, which functions as a channel
for discharging gas existing above the susceptor 11 to outside of
the chamber 10. An annular baffle plate 13 is disposed in the
middle of the gas exhaust path 12, and a lower portion of the gas
exhaust path 12, which is under the baffle plate 13, is coupled to
an automatic pressure control valve 14 (hereinafter, referred to as
an "APC") that is a variable butterfly valve. The APC 14 is
connected to a turbo molecular pump 15 (hereinafter, referred to as
a "TMP"), which is a gas exhaust pump for vacuum exhaust. Further,
the APC 14 is connected to a dry pump 16 (hereinafter, referred to
as a "DP") serving as a gas exhaust pump via the TMP 15. A gas
exhaust channel including the APC 14, TMP 15, and DP 16 is
hereinafter referred to as a "main pumping line", wherein the APC
14 controls pressure in the chamber 10 and, additionally, the TMP
15 and DP 16 depressurize the chamber 10 almost to vacuum.
[0028] Further, the lower portion of the gas exhaust path 12, which
is under the baffle plate 13, is coupled to another gas exhaust
channel (hereinafter, referred to as a "rough pumping line"), which
is separate from the main pumping line. The rough pumping line
includes a gas exhaust pipe 17, having a diameter of, e.g., 25 mm,
for connecting the lower portion to the DP 16; and a valve V2
installed in the middle of the gas exhaust pipe 17. The valve V2
can isolate the lower portion from the DP 16. A gas in the chamber
10 is discharged out by the DP 16 in the rough pumping line.
[0029] The susceptor 11 is connected to a high frequency power
supply 18 via a conducting wire 50, and the high frequency power
supply 18 applies a predetermined high frequency power to the
susceptor 11, whereby the susceptor 11 functions as a lower
electrode. Further, a matching unit 19 and a switch (electrical
state setting unit) 51 are installed in the middle of the
conducting wire 50, wherein the matching unit 19 reduces a
reflection of the high frequency power from the susceptor 11 to
thereby optimize an incidence efficiency of the high frequency
power to the susceptor 11, and the switch 51 facilitates a
changeover between ON and OFF state of the high frequency power
supply 18 in the conducting wire 50. Since the switch 51 is
inserted between the susceptor 11 and the high frequency power
supply 18, the susceptor 11 can be set to one of floating and
conducting electrical states. In particular, when the wafer W is
not mounted on the top surface of the susceptor 11, the susceptor
11 is set to the floating electrical state.
[0030] A circular electrode plate 20, formed of a conductive film,
for electrostatically attracting and holding the wafer W is
disposed inside an upper portion of the susceptor 11. A DC power
supply 22 is electrically connected to the electrode plate 20. The
wafer W is attracted and held on the top surface of the susceptor
11 by Coulomb force or Johnsen-Rahbek force produced by a DC
voltage applied to the electrode plate 20 from the DC power supply
22. While the wafer W need not be attracted on the top surface, the
electrode plate 20 is cut off from the DC power supply 22 to be in
a floating state. Further, an annular focus ring 24 formed of
silicon (Si) and the like converges plasma produced above the
susceptor 11 toward the wafer W.
[0031] A coolant chamber 25 of, e.g., a ring shape is provided
inside the susceptor 11. A coolant, e.g., cooling water, kept at a
specific temperature is supplied to the coolant chamber 25 from a
chiller unit (not shown) via a pipe 26 to be circulated therein,
whereby the wafer W on the susceptor 11 is controlled to be
maintained at a specific process temperature by the coolant.
[0032] In the top surface of susceptor 11, thermally conductive gas
supply holes 27 and a thermally conductive gas supply groove (not
shown) are disposed in a portion which the wafer is attracted to
(hereinafter, referred to as an "attracting surface"). Those
thermally conductive gas supply holes 27 and the like are connected
to a thermally conductive gas feed pipe 29 equipped with a valve V3
via a thermally conductive gas supply line 28 arranged in the
susceptor 11. A thermally conductive gas, e.g., He gas, from a
thermally conductive gas supply unit (not shown) coupled to the
thermally conductive gas feed pipe 29 is supplied into a gap
between the attracting surface and the bottom surface of the wafer
W though the thermally conductive gas supply holes 27 and the like.
Accordingly, heat transfer is improved between the wafer W and the
susceptor 11. Further, the valve V3 can isolate the thermally
conductive gas supply holes 27 and the like from the thermally
conductive gas supply unit.
[0033] Further, disposed on the attracting surface is a plurality
of pusher pins 30, i.e., lift pins, which can be freely moved up
and down from the top surface of the susceptor 11. A rotational
movement of a motor (not shown) is converted into a linear movement
by ball screws and the like, whereby the pusher pins 30 can be
moved vertically. While the wafer W is attracted and held on the
attracting surface, an etching process is performed thereon and the
pusher pins 30 are accommodated in the susceptor 11, whereas when
the wafer W is unloaded from the chamber 10 after the plasma
processing completed, the pusher pins 30 are protruded from the top
surface of the susceptor 11 such that the wafer W is separated to
be lifted from the susceptor 11.
[0034] A shower head (upper electrode) 33 is disposed in a ceiling
portion of the chamber 10. The shower head 33 is connected to a
high frequency power supply 52, which applies a predetermined high
frequency power to the shower head 33. Accordingly, the shower head
33 functions as an upper electrode.
[0035] The shower head 33 includes an electrode plate 35 having a
plurality of gas ventholes 34 on its bottom surface, and an
electrode supporting member 36 for attachably or detachably
supporting the electrode plate 35. Further, a buffer chamber 37 is
provided in the electrode supporting member 36, wherein the buffer
chamber 37 is connected to a processing gas inlet pipe 38 extended
from a processing gas supply unit (not shown). A valve V1 is
installed in the middle of the processing gas inlet pipe 38. The
valve V1 can isolate the buffer chamber 37 from the processing gas
supply unit. Here, a distance D between the susceptor 11 and the
shower head 33 is set to be equal to or larger than, e.g., 35.+-.1
mm.
[0036] A gate valve 32 for opening or closing a loading/unloading
port 31 of the wafer W is installed on the sidewall of the chamber
10. In the chamber 10 of the plasma processing apparatus 1, as
describe above, a high frequency power is applied to the shower
head 33, whereby a high-density plasma is generated from the
processing gas in a space S and ions or radicals are produced.
[0037] Further, the plasma processing apparatus 1 is provided with
CPU (controller) 53 inside or outside the apparatus. The CPU 53 is
connected to valves V1, V2 and V3, APC 14, TMP 15, DP 16, high
frequency power supplies 18 and 52, DC power supply 22 and switch
51, thereby controlling operations of every component in accordance
with user's command or a predetermined processing method.
[0038] For performing an etching process in the plasma processing
apparatus 1, first, after the gate valve 32 is opened, the wafer W
serving as an object to be processed is loaded into the chamber 10
and mounted on the susceptor 11. Then, a processing gas having a
specified flow rate ratio (e.g., gaseous mixture formed of
C.sub.4F.sub.8 gas, O.sub.2 gas and Ar gas having a specified flow
rate ratio) is introduced into the chamber 10 at a predetermined
flow rate, and a fixed pressure level is maintained in the chamber
10 by the APC 14 and the like. Further, a high frequency power is
applied to the susceptor 11 from the high frequency power supply 18
and, at the same time, a high frequency power is applied to the
shower head 33 from the high frequency power supply 52. Further, a
DC voltage is applied to the electrode plate 20 from the DC power
supply 22, whereby the wafer W is attracted and held on the
susceptor 11. Then, the processing gas discharged through the
shower head 33 is converted into a plasma as described above.
Radicals or ions produced by the plasma are converged on the wafer
W by the focus ring 24, thereby physically or chemically etching
the surface of the wafer W. At this time, reaction products
generated by chemical etching are deposited on the top surface of
the susceptor 11. The reaction products deposited on the top
surface should be removed because they are attached as foreign
substances to the bottom surface of the wafer W when the wafer W is
mounted on the attracting surface.
[0039] As a measure devised to deal with the above problem, in the
plasma processing apparatus 1, the top surface of the susceptor 11
is exposed to a space S after the wafer W is unloaded therefrom,
and a cleaning gas is supplied into the space S from the shower
head 33. Further, the CPU 53 controls the high frequency power
supply 52 to apply a high frequency power to the shower head 33. At
this time, as mentioned above, the electrical state of the
susceptor 11 is set to a floating state by the switch 51. Further,
the electrode plate 20 is cut off from the DC power supply 22 to be
in a floating state. Accordingly, the radicals produced from the
cleaning gas are made to have a contact with the top surface of the
susceptor 11, whereby the reaction products deposited on the top
surface of the susceptor 11 can be removed therefrom.
[0040] Hereinafter, there will be described a cleaning method of a
plasma processing apparatus, for removing the reaction products
deposited on the top surface of the susceptor 11 in the plasma
processing apparatus 1.
[0041] FIG. 2 is a flow chart of cleaning processing of a plasma
processing apparatus, wherein the cleaning processing is performed
in the plasma processing apparatus shown in FIG. 1 after the
etching processing is performed on the wafer W.
[0042] In the cleaning processing shown in FIG. 2, first, after the
etching processing performed on the last wafer W in, e.g., 1 lot is
finished, the pusher pins 30 are protruded from the top surface of
the susceptor 11 to lift up the wafer W. Then, the gate valve 32 is
opened, and a transfer arm (not shown) is brought into the chamber
10 through the loading/unloading port 31. Thereafter, the transfer
arm unloads the wafer W which is raised by the pusher pins 30 to
outside of the chamber 10 through the loading/unloading port 31
(step S21). Accordingly, the top surface of the susceptor 11 is
exposed to the space S. By this time, the switch 51 has already
converted the electrical state of the susceptor 11 into a floating
state (floating state setting step). Further, the electrode plate
20 has also been cut off from the DC power supply 22 to be in a
floating state.
[0043] Subsequently, after the gate valve 32 is closed, the CPU 53
controls the APC 14, TMP 15 and DP 16, so that the chamber 10 is
depressurized via the main pumping line or the rough pumping line
(step S22) until pressure in the chamber 10 is equal to or lower
than a specified value, e.g., 2.67 Pa (20 mTorr). Then, a cleaning
gas, e.g., O.sub.2 gas, is supplied into the space S at a specified
flow rate, e.g., 600 SCCM (cm.sup.3/min, at 1 atm, at 0.degree.
C.), through the shower head 33 (step S23).
[0044] Thereafter, the CPU 53 controls the high frequency power
supply 52 to apply a predetermined high frequency power, e.g., 2000
W, to the shower head 33 (high frequency power applying step, step
S24). At this time, a plasma is generated from the cleaning gas
near the shower head 33, thereby producing ions or radicals.
[0045] Here, since the electrical state of the susceptor 11 is set
to a floating state, a large self-bias is not induced in the
susceptor 11, and ions are not strongly attracted to the susceptor
11. Accordingly, the kinetic energy of an ion is small when it
collides with the top surface of the susceptor 11. As a result, an
ion does not remove the deposited reaction products from the top
surface of the susceptor 11 by its impact force and, further, does
not erode the susceptor 11.
[0046] On the other hand, a radical, which reaches the top surface
of the susceptor 11 together with an ion, makes a contact with a
reaction product deposited on the top surface of the susceptor 11
to chemically react therewith (radical contacting step, step S25),
thereby generating another volatile reaction product. The volatile
reaction products are easily separated (volatilized) from the top
surface of the susceptor 11 to be discharged outside the chamber 10
via the main pumping line or the rough pumping line. Consequently,
the reaction products deposited on the top surface of the susceptor
11 can be removed.
[0047] Subsequently, when a specific time, e.g., 20 seconds, is
elapsed after applying the predetermined high frequency power to
the shower head 33, the CPU 53 controls the APC 14, TMP 15 and DP
16 to stop operations of the main pumping line or the rough pumping
line and controls the high frequency power supply 52 to stop
applying the predetermined high frequency power to the shower head
33 (step S26). Further, the CPU 53 controls the switch 51 to
convert the electrical state of the susceptor 11 into a conducting
state (step S27), thereby finishing the processing.
[0048] In accordance with the processing shown in FIG. 2, a
predetermined high frequency power is applied to the shower head
33, and the electrical state of the susceptor 11 is set to the
floating state. When a high frequency power is applied to the
shower head 33, ions and radicals are generated from the cleaning
gas near the shower head 33. At this time, since the electrical
state of the susceptor 11 is set to the floating state, a large
self-bias is not induced in the susceptor 11. Accordingly, the
kinetic energy of the ion colliding with the top surface of the
susceptor 11 is small, whereby erosion of the susceptor 11 does not
happen. On the other hand, a radical getting in contact with the
susceptor 11 reacts chemically with the deposited reaction products
on the top surface of the susceptor 11 to thereby remove same
therefrom. As a result, the surface roughness will not be worsened
on the attracting surface of the susceptor 11. Therefore, the
reaction products deposited on the susceptor 11 can be removed
without an increase in the leak rate of the thermally conductive
gas between the wafer W and the susceptor 11 in plasma processing
after cleaning processing.
[0049] Further, the plasma processing apparatus 1 includes the
chamber 10 for accommodating the susceptor 11 and the shower head
33, wherein the shower head 33 and the susceptor 11 are
respectively disposed in an upper portion and a lower portion of
the chamber 10 and the susceptor 11 is connected to the high
frequency power supply 52. Thus, an etching process can be easily
performed on the wafer W in accordance with a desired processing
method and, further, so can another plasma processing such as a
film forming process. Further, since the susceptor 11 is
accommodated in the chamber 10, other reaction products produced in
a chemical reaction of radicals can be removed by depressurizing
the chamber 10, and the susceptor 11 can be properly cleaned.
[0050] The plasma processing apparatus and the cleaning method
thereof in accordance with the preferred embodiments of the present
invention have been described, but the present invention is not
limited thereto.
[0051] For instance, the above-mentioned plasma processing
apparatus 1 is a parallel plate type plasma processing apparatus
including electrodes respectively in an upper portion and a lower
portion of the chamber 10, but the present invention can be applied
to any plasma processing apparatus as long as it includes a
mounting table for mounting thereon the wafer W and an electrode
which is connected to a high frequency power supply, for example, a
remote plasma processing apparatus such as an electron cyclotron
resonance (ECR) plasma processing apparatus or a slot plane antenna
(SPA) plasma processing apparatus.
[0052] Further, although it is the mounting table that is cleaned
in the above plasma processing apparatus 1, an object to be cleaned
is not limited thereto, and any component having an electrical
state that can be set to a floating state can be cleaned. For
example, if an inner wall of the chamber or an upper electrode can
be set to have a floating electrical state, the present invention
can be applied to them to thereby clean them.
[0053] Hereinafter, the preferred embodiments of the present
invention will be described in detail.
EMBODIMENT 1
[0054] In the plasma processing apparatus 1, the cleaning
processing shown in FIG. 2 was performed under the following
conditions.
[0055] Pressure in the chamber 10: 2.67 Pa
[0056] Kind of cleaning gas : O.sub.2 gas
[0057] Supply flow rate of the cleaning gas: 600 SCCM
[0058] High frequency power applied to the shower head 33: 2000
W
[0059] Subsequently, after seasoning, pressure of He gas supplied
through the thermally conductive gas supply holes 27 was set to
0.667 kPa, and an etching process was performed on the wafer W. The
leak rate of He gas from a gap between the attracting surface and
the bottom surface of the wafer W was measured against the total
application time (hereinafter, referred to as "total RF time") of
the high frequency power applied to the susceptor 11 and the shower
head 33. Then, measurement results are represented by a solid line
on a graph of FIG. 3. Further, average surface roughness on the
attracting surface was measured at total RF times of 0 hour, 1300
hours and 3231 hours, respectively.
EMBODIMENT 2
[0060] In the plasma processing apparatus 1, the cleaning
processing shown in FIG. 2 was performed under the same conditions
as Embodiment 1.
[0061] Subsequently, after seasoning, pressure of He gas supplied
through the thermally conductive gas supply holes 27 was set to
3.33 kPa, and an etching process was performed on the wafer W. The
leak rate of He gas from a gap between the attracting surface and
the bottom surface of the wafer W was measured against the total RF
time of the high frequency power applied to the susceptor 11 and
the shower head 33. Then, measurement results are represented by a
dashed dotted line on the graph of FIG. 3. Further, the average
surface roughness on the attracting surface was measured at total
RF times of 0 hour, 1300 hours and 3231 hours, respectively.
EMBODIMENT 3
[0062] In the plasma processing apparatus 1, the cleaning
processing shown in FIG. 2 was performed under the same conditions
as Embodiment 1.
[0063] Subsequently, after seasoning, the pressure of He gas
supplied through the thermally conductive gas supply holes 27 was
set to 6.67 kPa, and an etching process was performed on the wafer
W. The leak rate of He gas from a gap between the attracting
surface and the bottom surface of the wafer W was measured against
the total RF time of the high frequency power applied to the
susceptor 11 and the shower head 33. Then, measurement results are
represented by a dashed double-dotted line on the graph of FIG. 3.
Further, average surface roughness on the attracting surface was
measured at total RF times of 0 hour, 1300 hours and 3231 hours,
respectively.
[0064] In each embodiment, after the cleaning processing shown in
FIG. 2 was performed, it was observed by the naked eye that the
reaction products deposited on the top surface (attracting surface)
of the susceptor 11 were removed therefrom.
[0065] Further, as illustrated in FIG. 3, in an etching process
performed after the cleaning processing of FIG. 2 in each
embodiment, leak rates of He gas are very small and, specifically,
even at a total RF time of 600 hours (not shown), an allowable leak
rate of He gas is equal to or less than 2 SCCM.
[0066] In the above embodiments 1 to 3, the surface roughness of
the attracting surface was 0.13 .mu.m at a total RF time of 0 hour;
0.19 .mu.m at a total RF time of 1300 hours; and 0.27 .mu.m at a
total RF time of 3231 hours, which rarely changed. Accordingly, it
is found that ions do not erode the susceptor 11.
[0067] In accordance with the plasma processing apparatus shown in
FIG. 1 and the cleaning processing shown in FIG. 2, as described
above, the reaction products deposited on the top surface of the
susceptor 11 can be removed without increasing a leak rate of He
gas.
[0068] Further, the diameter of the wafer W is 300 mm and the
distance D between the electrodes, i.e., the susceptor 11 and the
shower head 33, was set to 35.+-.1 mm in the plasma processing
apparatus 1 of the embodiments 1 to 3, but the same results as in
the plasma processing apparatus 1 were obtained in another plasma
processing apparatus, wherein the diameter of the wafer W was 200
mm and the distance D between the electrodes was set to 70.+-.1
mm.
[0069] While the invention has been shown and described with
respect to the preferred embodiments, it will be understood by
those skilled in the art that various changes and modifications may
be without departing from the spirit and scope of the invention as
defined in the following claims.
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