U.S. patent application number 11/091416 was filed with the patent office on 2005-12-08 for plasma processing apparatus and method.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Moriya, Tsuyoshi, Nakayama, Hiroyuki.
Application Number | 20050272227 11/091416 |
Document ID | / |
Family ID | 35050042 |
Filed Date | 2005-12-08 |
United States Patent
Application |
20050272227 |
Kind Code |
A1 |
Moriya, Tsuyoshi ; et
al. |
December 8, 2005 |
Plasma processing apparatus and method
Abstract
There is provided a plasma processing apparatus including a
plasma generating unit for generating a plasma in a processing
chamber in which a set processing is performed on a substrate
serving as an object to be processed. The plasma processing
apparatus further includes a particle moving unit for
electrostatically driving particles in a region above the substrate
to be removed out of the region above the substrate in the
processing chamber while the processing on the substrate is
performed by using the plasma. In addition, there is provided a
plasma processing method of a plasma processing apparatus including
the steps of generating plasma in a processing chamber in which a
set processing is performed on a substrate serving as an object to
be processed; and performing the processing on the substrate by the
plasma.
Inventors: |
Moriya, Tsuyoshi;
(Nirasaki-shi, JP) ; Nakayama, Hiroyuki;
(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: |
35050042 |
Appl. No.: |
11/091416 |
Filed: |
March 29, 2005 |
Current U.S.
Class: |
438/474 ;
118/722; 438/798 |
Current CPC
Class: |
H01J 37/32431 20130101;
H01J 2237/022 20130101 |
Class at
Publication: |
438/474 ;
438/798; 118/722 |
International
Class: |
H01L 021/42 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2004 |
JP |
2004-096455 |
Claims
What is claimed is:
1. A plasma processing apparatus comprising a plasma generating
unit for generating a plasma in a processing chamber in which a set
processing is performed on a substrate serving as an object to be
processed, the plasma processing apparatus further comprising a
particle moving unit for electrostatically driving particles in a
region above the substrate to be removed out of the region above
the substrate in the processing chamber while the processing on the
substrate is performed by using the plasma.
2. The plasma processing apparatus of claim 1, wherein the particle
moving unit includes: a mounting table for mounting the substrate;
a first electrode for electrostatically adsorbing the substrate
onto the mounting table; a ring-shaped member installed to enclose
a periphery of the substrate; a second electrode for
electrostatically adsorbing the ring-shaped member onto the
mounting table; a first power supply, connected to the first
electrode, for supplying an electric power with a first electric
potential; and a second power supply, connected to the second
electrode, for supplying an electric power with a second electric
potential different from the first electric potential, wherein the
mounting table, the first electrode, the ring-shaped member, and
the second electrode are installed in the processing chamber.
3. The plasma processing apparatus of claim 2, wherein the particle
moving unit includes a voltage controller for controlling at least
an electric potential of the second electrode to remove the
particles from the region above the substrate to a region above the
second electrode.
4. The plasma processing apparatus of claim 2, wherein the second
electric potential is higher than the first electric potential when
the particles are negatively charged during the plasma
processing.
5. The plasma processing apparatus of claim 2, wherein the first
electric potential is of negative polarity and the second electric
potential is of positive polarity.
6. The plasma processing apparatus of claim 2, wherein the first
electric potential is of negative polarity and the second electric
potential is of negative polarity.
7. The plasma processing apparatus of claim 2, wherein the second
electric potential is higher than an electric potential formed near
a surface of the substrate in the region above the substrate in
response to the first electric potential or a self-bias potential
formed by the generation of the plasma.
8. The plasma processing apparatus of claim 1, further comprising a
particle removing unit for removing the particles in the processing
chamber.
9. The plasma processing apparatus of claim 8, further comprising
an exhausting unit for exhausting the processing chamber.
10. A plasma processing method of a plasma processing apparatus,
comprising the steps of generating a plasma in a processing chamber
in which a set processing is performed on a substrate serving as an
object to be processed; and performing the processing on the
substrate by the plasma, the plasma processing method further
comprising the step of electrostatically driving particles in a
region above the substrate to be removed out of the region above
the substrate in the processing chamber during the processing on
the substrate.
11. The plasma processing method of claim 10, wherein the plasma
processing apparatus includes a mounting table for mounting the
substrate; a first electrode for electrostatically adsorbing the
substrate onto the mounting table; a ring-shaped member installed
to enclose a periphery of the substrate; a second electrode for
electrostatically adsorbing the ring-shaped member onto the
mounting table; a first power supply, connected to the first
electrode, for supplying an electric power with a first electric
potential; and a second power supply, connected to the second
electrode, for supplying an electric power with a second electric
potential different from the first electric potential, wherein the
mounting table, the first electrode, the ring-shaped member, and
the second electrode are installed in the processing chamber, and
wherein the step of driving particles includes the substep of
supplying the electric power with a second electric potential
different from the first electric potential to the second electrode
by the second power supply.
12. The plasma processing method of claim 11, wherein the step of
driving particles further includes the substep of controlling at
least an electric potential of the second electrode to remove the
particles from the region above the substrate to a region above the
second electrode.
13. The plasma processing method of claim 11, wherein the second
electric potential is higher than the first electric potential when
the particles are negatively charged during the plasma
processing.
14. The plasma processing method of claim 11, wherein the first
electric potential is of negative polarity and the second electric
potential is of positive polarity.
15. The plasma processing method of claim 11, wherein the first
electric potential is of negative polarity and the second electric
potential is of negative polarity.
16. The plasma processing method of claim 11, wherein the second
electric potential is higher than an electric potential formed near
a surface of the substrate in the region above the substrate in
response to the first electric potential or a self-bias potential
formed by the generation of the plasma.
17. The plasma processing method of claim 10, further comprising
the step of removing the particles in the processing chamber.
18. The plasma processing method of claim 17, further comprising
the step of exhausting the processing chamber.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a plasma processing
apparatus and method; and, more particularly, a plasma processing
apparatus and method using a processing chamber for performing a
plasma processing on a substrate.
BACKGROUND OF THE INVENTION
[0002] Recently, a treatment using a plasma (hereinafter, referred
to as "plasma processing") such as an etching, sputtering and CVD
(chemical vapor deposition) has been employed to be performed on an
object to be processed such as a semiconductor wafer (hereinafter,
referred to as "wafer") in a manufacturing process of a
semiconductor apparatus.
[0003] An apparatus for carrying out such process (shown in FIG. 8)
has a processing chamber 800, which is a cylindrical container, for
performing a plasma processing on a wafer. The processing chamber
800 includes a chamber sidewall 810, an upper electrode 811
installed at the top of the chamber 800, a lower electrode 812
installed in a lower portion of the processing chamber 800, an ESC
(electrostatic chuck) stage 820 and a focus ring 821 mounted on an
upper side of the lower electrode 812, and a baffle plate 830
interposed between the chamber sidewall 810 and the lower electrode
812.
[0004] The upper electrode 811, which has a plurality of through
holes not shown in the drawing, serves as a shower head for
introducing a process gas for the plasma processing into the
processing chamber 800 through the through holes. The lower
electrode 812 is connected to a high frequency power supply 813.
The focus ring 821 is made of a ring-shaped member formed to
enclose a wafer mounted on the upper side of the ESC stage 820.
[0005] The ESC stage 820 includes an ESC electrode 820a embedded in
the ESC stage 820 to electrostatically adsorb the mounted wafer
onto the ESC stage 820. The ESC electrode 820a is connected to a
variable power supply 822 for providing electric power required to
adsorb the wafer onto the ESC electrode 820a.
[0006] In the plasma processing apparatus shown in FIG. 8 is formed
a plasma region of the plasma generated by a high frequency
electric field formed in a space between the upper electrode 811
and the lower electrode 812 as shown in the figure. The plasma
processing apparatus performs an etching on, for example, an oxide
film already formed on an upper side of the wafer by the generated
plasma. The particles detached from an inner wall of the chamber
sidewall 810 by the etching float around inside the processing
chamber 800. After the etching is completed, the particles are
removed by exhausting the processing chamber 800 through a small
through hole (not shown) located in the baffle plate 830 by using a
pump which is not shown.
[0007] Such particles are negatively charged by the electrons in
the plasma to float around the plasma region above the wafer during
the etching process, and will be attached onto the upper side of
the wafer to thereby contaminate the wafer after the plasma
production is stopped by completing the etching process.
[0008] There are disclosed techniques that can be employed to
prevent the particles from being attached onto the upper side of
the wafer as described above, wherein the charged particles are
actively removed by using another electrode installed in the
processing chamber 800 before the plasma generation or after the
plasma extinction (for example, References 1 and 2).
[0009] (Reference 1) Japanese Patent Laid-open Application No.
H10-284471
[0010] (Reference 2) European Patent Publication No. 1119030
[0011] However, although the particles can be driven from the
region above the wafer towards the other electrode before the
plasma being generated or after the plasma being extinguished by
the techniques described in References 1 and 2, it is not practical
to remove the particles while the plasma is being produced because
the other electrode causes to generate an abnormal discharge or to
produce particles during the plasma generation.
[0012] Further, since the particles in the region above the wafer
effectively mask the parts to be processed on the wafer to thereby
reduce the yield, it is required that these particles have to be
purged out of the region above the wafer especially while the
plasma is being generated. In addition, by suppressing the yield
reduction, the productivity is expected to improve.
SUMMARY OF THE INVENTION
[0013] It is a first object of the present invention to provide a
plasma processing apparatus and method for inhibiting the
attachment of the particles to prevent the contamination of the
wafer.
[0014] It is a second object of the present invention to provide a
plasma processing apparatus and method for removing the particles
from the region above the wafer during the plasma generation to
enhance the productivity.
[0015] In accordance with one aspect of the present invention,
there is provided a plasma processing apparatus comprising a plasma
generating unit for generating a plasma in a processing chamber in
which a set processing is performed on a substrate serving as an
object to be processed, the plasma processing apparatus further
comprising a particle moving unit for electrostatically driving
particles in a region above the substrate to thereby be removed out
of the region above the substrate in the processing chamber while
the processing on the substrate is performed by using the
plasma.
[0016] Preferably, the particle moving unit includes: a mounting
table for mounting the substrate; a first electrode for
electrostatically adsorbing the substrate onto the mounting table;
a ring-shaped member installed to enclose a periphery of the
substrate; a second electrode for electrostatically adsorbing the
ring-shaped member onto the mounting table; a first power supply,
connected to the first electrode, for supplying an electric power
with a first electric potential; and a second power supply,
connected to the second electrode, for supplying an electric power
with a second electric potential different from the first electric
potential, wherein the mounting table, the first electrode, the
ring-shaped member, and the second electrode are installed in the
processing chamber.
[0017] Preferably, the particle moving unit includes a voltage
controller for controlling at least a potential of the second
electrode to remove the particles from the region above the
substrate to a region above the second electrode.
[0018] Preferably, the second electric potential is higher than the
first electric potential when the particles are negatively charged
during the plasma processing.
[0019] Preferably, the first electric potential is of negative
polarity and the second electric potential is of positive or
negative polarity.
[0020] Preferably, the second electric potential is higher than an
electric potential formed near a surface of the substrate in the
region above the substrate in response to the first electric
potential or a self-bias potential formed by the generation of the
plasma.
[0021] Preferably, the plasma processing apparatus further
comprises a particle removing unit for removing the particles in
the processing chamber.
[0022] Preferably, the plasma processing apparatus further
comprises an exhausting unit for exhausting the processing
chamber.
[0023] In accordance with another aspect of the present invention,
there is provided a plasma processing method of a plasma processing
apparatus, comprising the steps of generating a plasma in a
processing chamber in which a set processing is performed on a
substrate serving as an object to be processed; and performing the
processing on the substrate by the plasma, the plasma processing
method further comprising the step of electrostatically driving
particles in a region above the substrate to thereby be removed out
of the region above the substrate in the processing chamber during
the processing on the substrate.
[0024] Preferably, the plasma processing apparatus includes a
mounting table for mounting the substrate; a first electrode for
electrostatically adsorbing the substrate onto the mounting table;
a ring-shaped member installed to enclose a periphery of the
substrate; a second electrode for electrostatically adsorbing the
ring-shaped member onto the mounting table; a first power supply,
connected to the first electrode, for supplying an electric power
with a first electric potential; and a second power supply,
connected to the second electrode, for supplying an electric power
with a second electric potential different from the first electric
potential, wherein the mounting table, the first electrode, the
ring-shaped member, and the second electrode are installed in the
processing chamber, and wherein the step of driving particles
includes the substep of supplying the electric power with a second
electric potential different from the first electric potential to
the second electrode by the second power supply.
[0025] Preferably, the step of driving particles further includes
the substep of controlling at least a potential of the second
electrode to remove the particles from the region above the
substrate to a region above the second electrode.
[0026] Preferably, the second electric potential is higher than the
first electric potential when the particles are negatively charged
during the plasma processing.
[0027] Preferably, the first electric potential is of negative
polarity and the second electric potential is of positive
polarity.
[0028] Preferably, the first electric potential is of negative
polarity and the second electric potential is of negative
polarity.
[0029] Preferably, the second electric potential is higher than an
electric potential formed near a surface of the substrate in the
region above the substrate in response to the first electric
potential or a self-bias potential formed by the generation of the
plasma.
[0030] Preferably, the plasma processing method further comprises
the step of removing the particles in the processing chamber.
[0031] Preferably, the plasma processing method further comprises
the step of exhausting the processing chamber.
[0032] In accordance with the present invention, since the
particles in the region above the substrate are electrostatically
driven out of the region above the substrate in the processing
chamber during the processing on the substrate by the plasma, the
attachment of the particles can be inhibited, thereby preventing
the contamination of the wafer. Further, the particles are removed
from the region above the substrate during the plasma generation,
thereby enhancing the productivity.
[0033] Still further, the second power supply supplies the electric
power with a second electric potential different from the first
electric potential to the second electrode for electrostatically
adsorbing the ring-shaped member installed at the periphery of the
substrate onto the mounting table, thereby efficiently inhibiting
the attachment of the particles.
[0034] Still further, at least a potential of the second electrode
is controlled to remove the particles from the region above the
substrate to a region above the second electrode, thereby
efficiently inhibiting the attachment of the particles.
[0035] Still further, the second electric potential is higher than
the first electric potential when the particles are negatively
charged during the plasma processing, thereby efficiently
inhibiting the attachment of the particles.
[0036] Still further, the first electric potential is of negative
polarity and the second electric potential is of positive polarity,
thereby efficiently inhibiting the attachment of the particles.
[0037] Still further, the second electric potential is higher than
an electric potential formed near a surface of the substrate in the
region above the substrate in response to the first electric
potential or a self-bias potential formed by the generation of the
plasma, thereby efficiently inhibiting the attachment of the
particles.
[0038] Still further, the particles are removed in the processing
chamber, thereby efficiently inhibiting the attachment of the
particles.
[0039] Still further, the processing chamber is exhausted, thereby
efficiently inhibiting the attachment of the particles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] 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:
[0041] FIG. 1 shows a cross sectional view schematically
illustrating a configuration of a plasma processing apparatus in
accordance with a preferred embodiment of the present
invention;
[0042] FIG. 2 provides a graph representing a relation between an
electric power for generating a plasma and the number of
particles;
[0043] FIG. 3 describes an electric potential distribution formed
in the processing chamber 100 shown in FIG. 1;
[0044] FIG. 4 exemplarily illustrates particle trajectories in a
plasma region under a potential distribution represented by
equipotential lines in FIG. 3;
[0045] FIG. 5A exemplarily depicts particle trajectories observed
from an observation system shown in FIG. 7; and FIG. 5B is a
partial enlarged view of FIG. 5A;
[0046] FIG. 6 presents a graph showing a relation between the
number of the particles observed as in FIGS. 5A and 5B and a
voltage applied to an ESC electrode 122a for FR adsorption;
[0047] FIG. 7 schematically shows a configuration of the
observation system for observing the particles to obtain the
experimental results described in FIGS. 5A, 5B and 6; and
[0048] FIG. 8 schematically illustrates a configuration of the
conventional plasma processing apparatus.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0049] Hereinafter, a preferred embodiment of the present invention
will be described with reference to the drawings.
[0050] FIG. 1 shows a cross sectional view schematically
illustrating a configuration of a plasma processing apparatus in
accordance with a preferred embodiment of the present
invention.
[0051] A plasma processing apparatus shown in FIG. 1 includes a
processing chamber 100 which is a cylindrical container for a
prearranged plasma-using processing (hereinafter, referred to as
"plasma processing"), e.g., an etching, a sputtering or a CVD
(chemical vapor deposition), to be performed on a semiconductor
wafer (hereinafter, referred to as "wafer") functioning as an
object to be processed; and is configured as, for example, a
parallel-plate type CCP (capacitively coupled plasma) processing
apparatus.
[0052] The processing chamber 100 includes a chamber sidewall 110,
an upper electrode 111 installed at the top of the chamber, a lower
electrode 112 installed in a lower portion of the processing
chamber 100, an ESC (electrostatic chuck) stage 120 (mounting
table) mounted on an upper side of the lower electrode 112, and an
annular shaped baffle plate 130 interposed between the chamber
sidewall 110 and the lower electrode 112.
[0053] In addition, to the outside of the processing chamber 100 is
connected a gas exhaust line made of a tube-shaped member, and
pumps such as a turbo molecular pump TMP and a dry pump DP are
installed in the gas exhaust line. The pumps evacuate the
processing chamber 100 via the baffle plate 130, exhausting gas
containing particles by using a waste gas scrubber. Further, these
pumps can be installed in the chamber sidewall 110 not via the
baffle plate 130 but via a valve that can be freely opened and
closed.
[0054] The upper electrode 111, which has a plurality of through
holes not shown in the drawing, serves as a shower head for
introducing a process gas for the plasma processing into the
processing chamber 100 through the through holes. The lower
electrode 112 is connected to a high frequency power supply 113 for
providing a high frequency (RF: radio frequency) power.
[0055] The ESC stage 120 includes a focus ring (FR) 121 mounted on
an upper side thereof; a wafer-adsorbing ESC electrode 120a (first
electrode) embedded in the ESC stage 120 for electrostatically
adsorbing the mounted wafer onto the ESC stage 120; and an
FR-adsorbing ESC electrode 122a (second electrode) embedded in the
ESC stage 120 for electrostatically adsorbing the focus ring 121
onto the ESC stage 120. The focus ring 121 is made of a ring-shaped
member formed to enclose the wafer mounted on the upper side of the
ESC stage 120.
[0056] The FR-adsorbing ESC electrode 122a is connected via an LPF
(low pass filter) to an FR-adsorbing variable power supply 122
(second power supply) for providing a power required to adsorb the
focus ring 121 onto the FR-adsorbing ESC electrode 122a. The
wafer-adsorbing ESC electrode 120a is connected via an LPF (low
pass filter) to a variable power supply 125 (first power supply)
for providing a power required to adsorb the wafer onto the
FR-adsorbing ESC electrode 122a. These LPFs are necessary because
the ESC electrodes 120a and 122a are provided with an RF power
generated by a capacitive coupling between the RF power supplied to
the lower electrode 112 and the RF power supplied to the ESC
electrode 120a and 122a through an insulted region in the ESC stage
120. The variable power supplies 122 and 125 are connected to a
voltage control unit, which will be described later.
[0057] The plasma processing apparatus performs a plasma processing
such as an etching on an oxide film already formed on an upper side
of the wafer by using, for example, a plasma generated under an
intermediate vacuum level. To generate the plasma, a high frequency
(RF) electric field is generated in a space between the upper
electrode 111 and the lower electrode 112 by providing an RF power
to the lower electrode 112. (A plasma generating unit.) The plasma
thus generated forms a plasma region in the processing chamber 100
as shown in FIG. 1.
[0058] The particles detached from places such as an inner wall on
the chamber sidewall and the like float around in the processing
chamber 100, especially in the plasma region thereof. The
particles, floating in the plasma region, attract electrons
contained in the plasma to thereby become negatively charged.
[0059] As shown in FIG. 1, a bulk plasma region, which is a central
portion of the plasma region, has a positive polarity relative to a
reference voltage 0 V of the upper electrode 111 and a
substantially constant high electric potential (voltage). On the
contrary, an ion sheath region (Ion Sheath, Dark Space), which is
formed near the wafer surface in a region above the wafer, forms a
large potential gradient due to the influence of an electrostatic
force of the lower electrode 112 and the electric potential of the
bulk plasma region. Thus, the electric potential of the ion sheath
region is lower than the bulk plasma region, and the polarity
thereof is negative. Further, a potential gradient is formed in a
plasma periphery region, i.e., the plasma region excluding the bulk
plasma region.
[0060] Therefore, the particles negatively charged by attracting
the electrons in the plasma tend to float around in an upper part
of the ion sheath region (the region above the wafer) within the
plasma periphery region, because of a balance between the gravity
pulling down the particles vertically and the upwardly repelling
force generated by a potential gradient formed over a range from
the negatively polarized ion sheath region to the positively
polarized plasma periphery region, i.e., a potential difference
between the surface of the lower electrode 112 and the bulk plasma
region as well as an attractive force toward the positively
polarized bulk plasma region.
[0061] FIG. 2 provides a graph representing a relation between a
plasma power for generating plasma and the number of particles.
[0062] In FIG. 2, "plasma power" of the horizontal axis represents
power consumption [W] calculated from the voltage and current
applied to the high frequency power supply 113 for generating the
plasma; and "number of particles" of the vertical axis represents
the number of the particles observed in the processing chamber 100
when different voltages are applied to the high frequency power
supply 113, i.e., the number of the particles detached from the
chamber sidewall 110.
[0063] As shown in FIG. 2, the number of the particles decreases as
the plasma power increases. This is because the electrostatic force
of the generated plasma gets stronger as the plasma power gets
higher so that the particles are efficiently exhausted from the
region above the wafer. Therefore, it is preferable that the
voltage applied to the high frequency power supply 113 for
generating the plasma is high and the plasma power ranges from 100
W to 4000 W.
[0064] FIG. 3 describes an electric potential distribution formed
in the processing chamber 100 shown in FIG. 1.
[0065] As shown in FIG. 3, in the plasma processing apparatus, an
electric potential distribution represented by the electric force
lines, i.e., dotted lines and the equipotential lines, i.e., solid
lines is formed in the processing chamber 100 when electric powers
of different voltages are applied to the ESC electrodes 120a and
122a, respectively. Further, the electric force lines represent the
case where the electric potential of the power applied to the
wafer-adsorbing ESC electrode 120a (first potential) is lower than
that applied to the focus ring 121 (second potential).
[0066] Further, the turn-on and turn-off of the power is controlled
by the voltage control unit (sequential control unit) shown in FIG.
1 as follows.
[0067] In case of turning on the power, the voltage control unit
turns on the power to the wafer-adsorbing ESC electrode 120a after
the RF power for generating the plasma is turned on, e.g., after 1
second therefrom; and then, turns on the power to the FR-adsorbing
ESC electrode 122a after a predetermined time within a range of,
for example, 0 to 100 msec. (The voltage control unit.) Further, in
case of turning off the power, the voltage control unit turns off
the power to the FR-adsorbing ESC electrode 122a; subsequently
turns off the power to the wafer-adsorbing ESC electrode 120a after
a predetermined time within a range of, for example, 0 to 100 msec;
and then, turns off the RF power after, e.g., 1 second therefrom.
Thus, the potential distribution shown in FIG. 3 can be formed in
the processing chamber 100 while the atmosphere in the processing
chamber 100 is electrostatically stable, but not while the
atmosphere in the processing chamber 100 is electrostatically
unstable, namely, right after the plasma is generated or the plasma
is extinguished.
[0068] The voltage control unit has been described to control the
turn-on and turn-off of the power application to the
wafer-adsorbing ESC electrode 120a. However, the voltage control
unit may well be able to control the voltage of the power to be
applied to the FR-adsorbing ESC electrode 122a while it monitors
the power application to the wafer-adsorbing ESC electrode
120a.
[0069] As shown in the equipotential lines described above, during
the plasma processing, the focus ring 121 and the wafer is
electrostatically adsorbed respectively onto high-voltage parts and
low-voltage parts of the ESC stage 120. Further, the particles
negatively charged by attracting the electrons contained in the
plasma are also attracted under the influence of the electrostatic
force towards high-voltage regions.
[0070] FIG. 4 exemplarily illustrates particle trajectories in a
plasma region in case of such potential distribution represented by
equipotential lines shown in FIG. 3. Further, FIG. 5A exemplarily
depicts particle trajectories observed from an observation system
that will be described in FIG. 7, and FIG. 5B is a partial enlarged
view thereof.
[0071] As depicted by the particle trajectories in the plasma
region (the region above the wafer) in FIGS. 4, 5A and 5B, when the
potential distribution represented by the equipotential lines as
shown in FIG. 3 is formed, the particles floating in the plasma
region are driven out of the region above the wafer to somewhere
above the focus ring 121 under the influence of the electrostatic
force to be attracted towards the high-voltage region. (A particle
moving unit.) To remove the particles efficiently, the potential of
the FR-adsorbing ESC electrode 122a is preferably higher than the
potential of the wafer-adsorbing ESC electrode 120a; and more
preferably, higher than the potential formed in response thereto
near the upper side of the wafer or the self-bias potential formed
by the plasma generation.
[0072] Further, as shown in FIGS. 5A and 5B, the particle
trajectories near the wafer are closely spaced in the horizontal
direction, and those above the focus ring 121 are spread widely in
the horizontal direction. This shows that the particles are
accelerated from a place above the wafer to another place above the
focus ring. This is because the particles get accelerated by being
repelled by the potential difference between the self-bias
potential of the ion sheath region and the potential of the plasma
periphery region, i.e., the region between the surface of the lower
electrode 112 and the bulk plasma region and, at the same time,
attracted by a high potential of the FR-adsorbing ESC electrode
122a.
[0073] Furthermore, preferably, the potential of the FR-adsorbing
ESC electrode 122a is of polarity opposite to that of the self-bias
potential in case of setting the ground as a reference voltage 0 V
or the potential formed near the upper side of the wafer in
response to the potential of the wafer-adsorbing ESC electrode 120a
in case of setting the ground as a reference voltage 0 V; in other
words, of positive polarity. Thus, the potential of the
FR-adsorbing ESC electrode 122a can easily be made higher than the
self-bias potential or the potential formed near the upper side of
the wafer in response to the potential of the wafer-adsorbing ESC
electrode 120a, thereby a force attracting the particles onto
somewhere above the focus ring 121 can be ensured to be
generated.
[0074] FIG. 6 presents a graph showing a relation between the
number of the particles observed as in FIGS. 5A and 5B and a
voltage applied to an ESC electrode 122a for FR adsorption.
Further, FIG. 6 exemplifies a measurement result of the number of
the particles observed by the observation system 600 shown in FIG.
7, which will be described later.
[0075] In FIG. 6, "voltage applied to focus ring" of the horizontal
axis represents the voltage applied to the FR-adsorbing ESC
electrode 122a in case where the voltage applied to the
wafer-adsorbing ESC electrode 120a (hereinafter, referred to as
"voltage applied to the wafer") is constant at 0 V that is the
reference voltage of the ground. Therefore, the voltage applied to
the focus ring also represents a relative potential difference with
respect to the voltage applied to the wafer (hereinafter, referred
to as "relative potential difference").
[0076] As shown in FIG. 6, if the voltage applied to the focus ring
is higher than the voltage applied to the wafer (for example, the
voltage applied to the focus ring is +200 V, i.e., the relative
potential difference is +200 V), the number of the particles over
the wafer is small but the number of the particles over the focus
ring 121 is large. On the contrary, if the voltage applied to the
focus ring is not higher than the voltage applied to the wafer (for
example, the voltage applied to the focus ring is 0 V, -120V, or
-150 V, i.e., the relative potential difference is 0 V, -120V, or
-150 V), the number of the particles over the wafer is large but
the number of the particles over the focus ring 121 is small.
[0077] Further, as shown in FIG. 6, the number of the particles
over the wafer decreases and that over the focus ring 121 increases
as the relative potential difference increases. Preferably, if the
relative potential difference is +150 V or higher, the number of
the particles over the wafer can certainly be made smaller than
that over the focus ring 121.
[0078] Referring to FIGS. 3 to 6, by setting the potential of the
power supplied to the wafer-adsorbing ESC electrode 120a lower than
the potential of the power supplied to the FR-adsorbing ESC
electrode 122a, the number of the particles in the region above the
wafer during the plasma processing, especially the number of the
particles in the plasma periphery region and the ion sheath region,
i.e., the particles in somewhere between the bulk plasma region and
the wafer surface, is reduced, thereby the attachment of the
particles can be suppressed to thereby prevent the wafer
contamination.
[0079] Further, since the particles in the region above the wafer
during the plasma processing are driven out of the region above the
wafer, the effect described hereinafter can be achieved.
[0080] By reducing the particles effectively masking the portion to
be processed on the wafer, the plasma processing can be carried out
without being obstructed by the particles, thereby the yield can be
increased and thus the productivity can be enhanced.
[0081] Since the number of particles over the wafer can be reduced
during the plasma processing, a cleaning operation of the
processing chamber performed before the plasma processing can be
facilitated; and, more specifically, the cleaning cycle can be
extended, the seasoning time after a wet cleaning can be shortened,
and, further, the start-up time of the plasma processing apparatus
can be shortened. As a result, the operation time of the plasma
processing apparatus can be increased, thereby significantly
enhancing the productivity.
[0082] FIG. 7 schematically shows a configuration of the
observation system for observing the particles to obtain the
experimental results described in FIGS. 5A, 5B and 6.
[0083] In FIG. 7, the observation system 600 includes a laser light
source 610, which is of SHG-YAG laser, for applying a laser beam
with a wavelength of 532 nm onto the particles in the processing
chamber 100, and an image-enhancement type CCD camera 620 for
imaging the inside of the processing chamber 100. Furthermore, in
the observation system 600, a half-wave plate 611, lenses 612 and
613, slits 614 and 615, and a light extinction device 616 are
arranged in this order along the light path from the laser light
source 610 to apply laser light scattering method. Between the
slits 614 and 615 is inserted the processing chamber 100 (see FIG.
4). A beam of light, scattered by the particles in the processing
chamber 100, enters the CCD camera 620 via an interference filter
621 used for the light with a wavelength of 532 nm.
[0084] In the plasma processing apparatus shown in FIG. 1, if the
plasma is extinguished by stopping the power application to the ESC
electrodes 120a and 122a after completing the plasma processing,
the particles in the processing chamber 100 are removed because the
plasma chamber 100 is exhausted via the baffle plate 130 by the
exhaust pumps. (A particle removing unit, an exhausting unit.)
Further, the exhausting process can be carried out during the
plasma processing.
[0085] Since the exhaust pumps evacuate via the baffle plate 130 in
the lower portion of the processing chamber 100, the exhausting
efficiency is generally low in the region near the wafer surface.
However, as described with reference to FIGS. 3 to 6, the particle
removing efficiency of the exhaust pumps can be enhanced because
the particles are moved to a region where the exhausting efficiency
of the pump is high, i.e., towards a region above the focus ring
121 near the baffle plate 130, during the plasma processing.
Therefore, we can make it sure that the particles are prevented
from being attached onto the upper surface of the wafer after the
plasma extinction.
[0086] In the plasma processing apparatus in accordance with the
preferred embodiment, the plasma to be generated was exemplified as
a CCP generated by an RF power. However, other kinds of plasma such
as an ICP (inductive coupled plasma) generated by an RF power or a
UHF (ultrahigh frequency plasma) generated by a microwave can also
be used therein.
[0087] The plasma processing apparatus in accordance with the
preferred embodiment of the present invention can be applied to
plasma-used processes such as an etching process, a sputtering
process, and a CVD process.
[0088] While the invention has been shown and described with
respect to the preferred embodiments, it will be understood by
those skilled in the art that various changes and modifications may
be made without departing from the spirit and scope of the
invention as defined in the following claims.
* * * * *