U.S. patent application number 12/055664 was filed with the patent office on 2008-07-31 for plasma processing apparatus and control method thereof.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Tsutomu Higashiura, Hideo Kato, Ryuji Ohtani, Naoto SAGAE, Hiroshi Tsuchiya.
Application Number | 20080179005 12/055664 |
Document ID | / |
Family ID | 34984938 |
Filed Date | 2008-07-31 |
United States Patent
Application |
20080179005 |
Kind Code |
A1 |
SAGAE; Naoto ; et
al. |
July 31, 2008 |
PLASMA PROCESSING APPARATUS AND CONTROL METHOD THEREOF
Abstract
There is provided a plasma processing apparatus includes a lower
electrode in a processing chamber on which a object to be processed
is mounted; an upper electrode confronting the lower electrode; a
first and a second high-frequency power supply for applying
high-frequency powers respectively to the upper and the lower
electrode; and an output controller for raising each of outputs
from the high-frequency power supplies at least three times in a
stepwise manner up to each of set levels for processing the object
to be processed. The output controller adjusts each of rising times
of the outputs from the high-frequency power supplies so that an
output of the second high-frequency power supply is raised earlier
than an output of the first high-frequency power supply while the
outputs from the high-frequency power supplies are raised up to the
set levels in a stepwise manner.
Inventors: |
SAGAE; Naoto; (Miyagi-gun,
JP) ; Tsuchiya; Hiroshi; (Nirasaki-shi, JP) ;
Higashiura; Tsutomu; (Nirasaki-shi, JP) ; Kato;
Hideo; (Nirasaki-shi, JP) ; Ohtani; Ryuji;
(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: |
34984938 |
Appl. No.: |
12/055664 |
Filed: |
March 26, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11060547 |
Feb 18, 2005 |
|
|
|
12055664 |
|
|
|
|
Current U.S.
Class: |
156/345.28 ;
257/E21.528; 438/9 |
Current CPC
Class: |
H01J 37/32935 20130101;
H01J 37/32082 20130101 |
Class at
Publication: |
156/345.28 ;
438/9; 257/E21.528 |
International
Class: |
C23F 1/00 20060101
C23F001/00; H01L 21/66 20060101 H01L021/66 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 20, 2004 |
JP |
2004-045172 |
Claims
1-24. (canceled)
25. A plasma processing apparatus, comprising: a lower electrode
disposed in a processing chamber, capable of mounting an object to
be processed thereon; an upper electrode disposed in the chamber to
face the lower electrode; a first high-frequency power supply and a
second high-frequency power supply for applying high-frequency
powers to at least one of the upper and the lower electrode; and an
output controller for raising respective outputs of the first and
the second high-frequency power supply up to respective set levels
for processing the object to be processed, wherein the output
controller controls the respective outputs of the high-frequency
power supplies to be raised continuously, to be raised stepwise, or
to be raised stepwise during a certain interval and continuously
during the rest, and wherein the output controller regulates raise
timings of the outputs of the respective high-frequency power
supplies such that one of the high-frequency powers, whose
frequency is lower than that of the other of the high-frequency
powers, is raised earlier than the other of the high-frequency
powers, while the outputs of the high-frequency power supplies are
raised up to the respective set levels.
26. The plasma processing apparatus of claim 25, wherein the output
controller controls the respective outputs of the high-frequency
power supplies such that the high frequency powers are raised
stepwise in at least three steps, and one of the high-frequency
powers reaches a level of a first step after the other of the
high-frequency powers reaches a level of a first step but before
the other of the high-frequency powers reaches a level of a second
step, and wherein an output of the first high-frequency power
supply has a frequency higher than that of an output of the second
high-frequency power supply.
27. The plasma processing apparatus of claim 26, wherein the output
of the first high-frequency power supply is supplied to the upper
electrode, and the output of the second high-frequency power supply
is supplied to the lower electrode.
28. The plasma processing apparatus of claim 27, wherein the output
controller regulates the outputs of the respective high-frequency
power supplies so that the outputs right before reaching the
respective set levels are within 25% and 50% of the set levels.
29. The plasma processing apparatus of claim 28, wherein the output
controller regulates the outputs of the respective high-frequency
power supplies so that first outputs are equal to or above levels
at which plasma can be ignited and not more than 25% of the
respective set levels.
30. The plasma processing apparatus of claim 27, wherein the output
controller regulates the outputs of the respective high-frequency
power supplies so that, while keeping the output of one
high-frequency power supply constant, the output of the other
high-frequency power supply is raised.
31. The plasma processing apparatus of claim 27, wherein the output
controller regulates the outputs of the respective high-frequency
power supplies so that differences between the respective outputs
fall within a certain range.
32. The plasma processing apparatus of claim 25, wherein one of the
high-frequency powers is applied to the lower electrode whereas the
other of the high-frequency powers is applied to the upper
electrode, and wherein the output controller controls the
high-frequency powers such that one of the high-frequency powers
applied to the lower electrode reaches a set level earlier than the
other of the high-frequency powers applied to the upper
electrode.
33. A method for controlling a plasma processing apparatus
including a lower electrode in a processing chamber on which an
object to be processed is mounted, an upper electrode disposed in
the chamber to face the lower electrode, and a first high-frequency
power supply and a second high-frequency power supply for applying
high-frequency powers to at least one of the upper and the lower
electrode, the method comprising the step of: raising respective
outputs of the high-frequency power supplies to reach respective
set levels for processing the object to be processed, wherein the
respective outputs of the high-frequency power supplies are
controlled to be raised continuously, to be raised stepwise, or to
be raised stepwise during a certain interval and continuously
during the rest, and wherein respective raise timings of the
outputs of the high-frequency power supplies are controlled such
that one of the high-frequency powers, whose frequency is lower
than that of the other of the high-frequency powers, is raised
earlier than the other of the high-frequency powers, while the
respective outputs of the high-frequency power supplies are raised
to the respective set levels.
34. The method of claim 33, wherein the respective outputs of the
high-frequency power supplies are controlled such that the
high-frequency powers are raised stepwise in at least three steps,
and one of the high-frequency powers reaches a level of a first
step after the other of the high-frequency powers reaches a level
of a first step but before the other of the high-frequency powers
reaches a level of a second step, and wherein an output of the
first high-frequency power supply has a frequency higher than that
of an output of the second high-frequency power supply.
35. The method of claim 34, wherein the output of the first
high-frequency power supply is supplied to the upper electrode, and
the output of the second high-frequency power supply is supplied to
the lower electrode.
36. The method of claim 35, wherein the respective outputs of the
high-frequency power supplies are regulated so that the outputs
right before reaching the respective set levels are within 25% and
50% of the set levels.
37. The method of claim 36, wherein the outputs of the respective
high-frequency power supplies are regulated so that first outputs
are equal to or above levels at which plasma can be ignited and not
more than 25% of the respective set levels.
38. The method of claim 35, wherein the outputs of the respective
high-frequency power supplies are regulated so that, while keeping
the output of one high-frequency power supply constant, the output
of the other high-frequency power supply is raised.
39. The method of claim 35, wherein the outputs of the respective
high-frequency power supplies are regulated so that differences
between the respective outputs fall within a certain range.
40. The method of claim 33, wherein one of the high-frequency
powers is applied to the lower electrode whereas the other of the
high-frequency powers is applied to the upper electrode, and
wherein the high-frequency powers are controlled such that one of
the high-frequency powers applied to the lower electrode reaches a
set level earlier than the other of the high-frequency powers
applied to the upper electrode.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a plasma processing
apparatus and a control method thereof.
BACKGROUND OF THE INVENTION
[0002] Conventionally, a plasma processing apparatus which employs
high-frequency glow discharge of a reactive gas introduced into a
processing chamber has been widely used for a semiconductor
fabrication process in order to perform a microprocessing on an
object to be processed such as a semiconductor wafer. A plasma
processing apparatus which employs high-frequency glow discharge,
otherwise known as a parallel plate type plasma processing
apparatus, includes an upper electrode and lower electrode and
performs a plasma processing on an object to be processed mounted
on the lower electrode by applying a high-frequency power only to
the upper electrode.
[0003] However, such a plasma processing apparatus has
disadvantages in that it is difficult to control plasma voltage
between the two electrodes, and some of electrical discharges will
be lost through the wall surface in the processing chamber which is
grounded, thereby making plasma non-uniform and unstable.
Consequently, the apparatus tend to be unsuitable for
microprecessing on a quarter-micron to half-micron scale as
demanded in the industry recently.
[0004] Therefore, attempts are underway to control the density of
plasma generated in a processing chamber by applying high-frequency
powers to an upper and lower electrode for microprocessing. FIG. 8
illustrates an example of such a plasma processing apparatus. A
processing chamber 100 includes a lower electrode 102 to be mounted
thereon an object to be processed W in a processing chamber 101,
and an upper electrode 103 facing the lower electrode 102, wherein
a first high-frequency power supply 106 applies a first
high-frequency power to the upper electrode 103 via a first
matching unit 107, and a second high-frequency power supply 108
applies a second high-frequency power to the lower electrode 102
via a second matching unit 109, thereby controlling the density of
plasma generated in the processing chamber 101. Thus, a glow
discharge is formed between the lower electrode 102 (grounded)and
the upper electrode 103 to give rise to a plasma of reactive gas
species. Desired etching is performed by making ions in the plasma
hit the surface of an object to be processed mounted on the lower
electrode 102 through the use of a potential difference between the
two electrodes.
[0005] With respect to managing the problems of microprocessing,
attempts are underway to achieve a high selectivity and high
etching-rate without charge-up damages by setting the process
condition at low pressure, e.g., 100 mTorr or less, or otherwise
using certain gases. [0006] (Reference 1) Japanese Patent Laid-open
Application No. H8-162293 [0007] (Reference 2) U.S. Pat. No.
5,716,534
[0008] However, when using a conventional plasma processing
apparatus such as in FIG. 8, it is difficult to control the process
as desired during the plasma generation stage because of
interferences between high-frequency power signals from the two
high-frequency power supplies, or distortions in waveform thereof.
At times, an object to be processed is subject to charge-up
damages.
[0009] Further, depending on the manner in which two high-frequency
power supplies provide high-frequency powers, the high frequency
power or the matching unit can be overloaded or some plasma can be
lost by an activation of a safety circuit therein. This can be
caused by, for example, generation of reflected waves from an
abrupt impedance change in the plasma processing apparatus.
[0010] To solve the above problems, the present inventor developed
the methods disclosed in References 1 and 2 in order to reduce
damages in an object to be processed. With these methods, a plasma
for etching is generated by forming a plasma through applying a
high-frequency power to one electrode first, then, a high-frequency
power is applied to the other electrode. As a result, the
dissociation rate increases and the plasma density becomes high,
thereby reducing charge-up damages in the object to be
processed.
[0011] However, as demands for microprocessing on a smaller scale
and for extending useful life of a plasma processing apparatus have
been growing, it has become necessary to further minimize damages
on an object to be processed and to reduce loads on a
high-frequency power supply, matching unit, and the like.
SUMMARY OF THE INVENTION
[0012] The present invention has been developed to solve the above
problems of the conventional plasma processing apparatus by
providing a new or improved plasma processing apparatus or a
control method thereof, capable of efficient plasma generation,
reducing damages on an object to be processed and reducing the
loads on a high-frequency power supply, matching unit or so
forth.
[0013] To solve the above problems, in accordance with one aspect
of the present invention, there is provided a plasma processing
apparatus, comprising: a lower electrode disposed in a processing
chamber, capable of mounting an object to be processed thereon; an
upper electrode disposed in the chamber to face the lower
electrode; a first high-frequency power supply for applying
high-frequency power to the upper electrode; a second
high-frequency power supply for applying high-frequency power to
the lower electrode; an output controller for raising stepwise,
respective outputs of the high-frequency power supplies up to
respective set levels for processing the object to be processed in
at least three steps, wherein the output controller regulates raise
timings of the outputs of the respective high-frequency power
supplies so that raising the output of the second high-frequency
power supply is followed by raising the output of the first
high-frequency power supply, while the outputs of the
high-frequency power supplies are raised stepwise up to the
respective set levels.
[0014] In order to solve the aforementioned problems, in accordance
with another aspect of the present invention, there is provided a
plasma processing apparatus, comprising: a lower electrode disposed
in a processing chamber, capable of mounting an object to be
processed thereon; an upper electrode disposed in the chamber to
face the lower electrode; a first and a second high-frequency power
supply for applying high-frequency power to the lower electrode; an
output controller for raising stepwise, respective outputs of the
high-frequency power supplies up to respective set levels for
processing the object to be processed in at least three steps,
wherein the output controller regulates raise timings of the
outputs of the respective high-frequency power supplies so that
raising the output of the second high-frequency power supply is
followed by raising the output of the first high-frequency power
supply, while the outputs of the high-frequency power supplies are
raised stepwise up to the respective set levels.
[0015] In order to solve the aforementioned problems, in accordance
with still another aspect of the present invention, there is
provided a method for controlling a plasma processing apparatus
including a lower electrode in a processing chamber on which an
object to be processed is mounted, an upper electrode disposed in
the chamber to face the lower electrode, a first high-frequency
power supply for applying a high-frequency power to the upper
electrode and a second high-frequency power supply for applying a
high-frequency power to the lower electrode, comprising the steps
of: raising respective outputs of the high-frequency power supplies
at least three times stepwise to reach respective set levels for
processing the object to be processed; and controlling respective
raise timings of the outputs of the high-frequency power supplies
so that raising the output of the second high-frequency power
supply is followed by raising the output of the first
high-frequency power supply while the respective outputs of the
high-frequency power supplies are raised to the respective set
levels.
[0016] In order to solve the aforementioned problems, in accordance
with still another aspect of the present invention, there is
provided a method for controlling a plasma processing apparatus
including a lower electrode in a processing chamber on which an
object to be processed is mounted, an upper electrode disposed to
face the lower electrode and a first and a second high-frequency
power supply for applying high-frequency powers to the lower
electrode, comprising the steps of: raising respective outputs of
the high-frequency power supplies at least three times stepwise to
reach respective set levels for processing the object to be
processed; and controlling respective raise timings of the outputs
of the high-frequency power supplies so that raising the output of
the second high-frequency power supply is followed by raising the
output of the first high-frequency power supply while the
respective outputs of the high-frequency power supplies are raised
to the respective set levels.
[0017] Further, in the apparatuses and the methods, the output
controller regulates the outputs of the respective high-frequency
power supplies so that the outputs right before reaching the
respective set levels are within 25% and 50% of the set levels. In
this case, it is preferable that the output controller regulates
the outputs of the respective high-frequency power supplies so that
first outputs are equal to or above levels at which plasma can be
ignited and not more than 25% of the respective set levels.
[0018] Still further, in the apparatuses and the methods, the
output controller regulates the outputs of the respective
high-frequency power supplies so that, while keeping the output of
one high-frequency power supply constant, the output of the other
high-frequency power supply is raised. Otherwise, the output
controller regulates the outputs of the respective high-frequency
power supplies so that differences between the respective outputs
fall within a certain range.
[0019] In order to solve the aforementioned problems, in accordance
with another aspect of the present invention, there is provided A
plasma processing apparatus, comprising: a lower electrode disposed
in a processing chamber, capable of mounting an object to be
processed thereon; an upper electrode disposed in the chamber to
face the lower electrode; a first and a second high-frequency power
supply for applying high-frequency power to the electrodes; an
output controller for continuously raising respective outputs of
the high-frequency power supplies to respective set levels for
processing the object to be processed or for raising the respective
outputs of the high-frequency power supplies to the respective set
levels stepwise during a certain interval and continuously during
the rest.
[0020] In order to solve the aforementioned problems, in accordance
with still another aspect of the present invention, there is
provided a method for controlling a plasma processing apparatus
including a lower electrode in a processing chamber on which a
object to be processed is mounted, an upper electrode disposed in
the chamber to face the lower electrode and a first and a second
high-frequency power supply for applying high-frequency powers to
the electrodes, comprising the steps of continuously raising
respective outputs of the high-frequency power supplies to
respective set levels for processing the object to be processed or
for raising the respective outputs of the high-frequency power
supplies to the respective set levels stepwise during a certain
interval and continuously during the rest.
[0021] Further, in the apparatus and the method, the output
controller regulates the outputs of the respective high-frequency
power supplies so that ratios between the respective outputs remain
constant or so that slopes of the outputs of the respective power
supplies are identical as they go up. Still further, the output
controller regulates the respective outputs of the high-frequency
power supplies so that the respective outputs are raised to the
respective set levels stepwise during a certain interval and
continuously during the rest. In this case, it is preferable that
the part during which the outputs go up stepwise is the initial
period when plasma is ignited.
[0022] Still further, in the apparatus and the method, the output
controller regulates the outputs of the respective high-frequency
power supplies so that the output of one high-frequency power
supply goes up stepwise while the other output goes up
continuously. In this case, it is preferable that the output of the
first high-frequency power supply is applied to the upper electrode
and the output of the second high-frequency power supply is applied
to the lower electrode, the output controller regulating the
respective outputs so that the output of the first high-frequency
power supply goes up stepwise and the output of the second
high-frequency power supply goes up continuously.
[0023] In accordance with the present invention, a plasma can be
generated efficiently; damages on an object to be processed can be
further reduced; and the loads on a high-frequency power supply,
matching unit and so forth can be further reduced.
Brief Description of the Drawings
[0024] 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:
[0025] FIG. 1 shows a cross sectional view illustrating a schematic
configuration of a plasma etching apparatus in accordance with a
preferred embodiment of the present invention;
[0026] FIG. 2 describes a specific example of raise timings of
high-frequency powers applied to two electrodes in the plasma
etching apparatus in accordance with the preferred embodiment of
the present invention, wherein the respective high-frequency powers
are raised to set levels stepwise continuously a certain amount at
a time;
[0027] FIG. 3 provides a specific example of raise timings of
high-frequency powers applied to two electrodes in the plasma
etching apparatus in accordance with the preferred embodiment of
the present invention, wherein the respective high-frequency powers
are raised stepwise repeatedly a certain amount at a time in the
initial stage and then raised directly to the set levels at once
right before reaching the set levels;
[0028] FIG. 4 presents a more specific example of raise timings
shown in FIG. 3;
[0029] FIG. 5 offers another example of raise timings of
high-frequency powers applied to two electrodes in the plasma
etching apparatus in accordance with the preferred embodiment of
the present invention, wherein the respective high-frequency powers
are raised to set levels continuously;
[0030] FIG. 6 represents another example of raise timings of
high-frequency powers applied to two electrodes in the plasma
etching apparatus in accordance with the preferred embodiment of
the present invention, wherein the respective high-frequency powers
are raised stepwise in the initial stage and then continuously
thereafter;
[0031] FIG. 7 presents another example of raise timings of
high-frequency powers applied to two electrodes in the plasma
etching apparatus in accordance with the preferred embodiment of
the present invention, wherein the high-frequency power to one of
the electrodes is raised stepwise while that to the other electrode
is raised continuously; and
[0032] FIG. 8 provides a cross sectional view illustrating a
schematic configuration of a conventional plasma etching apparatus
with two electrodes.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] Hereinafter, a preferred embodiment of the present invention
will be described in detail with reference to the accompanying
drawings. Further, in this specification and the accompanying
drawings, components having substantially identical functions and
configurations are assigned an identical reference numeral to
simplify their description.
[0034] A plasma etching apparatus 1 shown in FIG. 1 includes a
processing chamber 2 formed in a cylindrical or rectangular shape
made of conductive material, e.g., aluminum, and the processing
chamber 2 houses therein a mounting table 4 of an approximately
cylindrical shape for supporting an object to be processed, e.g., a
wafer W, the mounting table 4 having a vertically movable structure
by means of an elevation mechanism 3 such as a motor. It is
possible to construct the mounting table 4 by securing a plurality
of members formed of, e.g., aluminum by, e.g., bolts. Installed in
the mounting table 4 is a heat source unit such as a heat transfer
medium circulation unit 5, which is designed such that it can
adjust temperature on the processing surface of the object to be
processed to a desirable temperature.
[0035] A heat transfer medium of which temperature has been
adjusted to an appropriate temperature by means of a temperature
control unit (not shown in the drawings) can be introduced into the
heat transfer medium circulation unit 5 via a heat transfer medium
inlet line 6. The introduced heat transfer medium circulates in the
heat transfer medium circulation unit 5 so that heat or cooling is
transmitted into the semiconductor wafer W via the mounting table 4
during the circulation, thereby making it possible to adjust the
temperature of the processing surface on the semiconductor wafer W
to a desirable temperature. After the heat transfer process, the
heat transfer medium is driven out of the chamber via the heat
transfer medium discharge line 7. Further, although the illustrated
example has such configuration in which the heat transfer medium of
which temperature has been adjusted to an appropriate temperature
by means of a temperature control not shown in the drawings is made
to circulate, it is also possible to adopt a configuration in which
a cooling jacket and a heater installed in the mounting table 4
heat or cool the mounting table 4 so that temperature of the wafer
W can be controlled.
[0036] A central portion of an upper surface on the mounting table
4 has a shape of a projecting circular plate. A chuck portion for
supporting a object to be processed such as an electrostatic chuck
8 is installed at the central portion of the upper surface on the
mounting table 4, wherein a diameter of the electrostatic chuck 8
is approximately identical to, or slightly longer or shorter than,
that of the semiconductor wafer W as a object to be processed. The
electrostatic chuck 8, which supports the wafer W, is constituted
by an electrostatic chuck sheet having a conductive film 8c of,
e.g., copper foil inserted between two films 8a and 8b made of high
molecular insulating material such as polyimide resin or the like.
The conductive film 8c is connected to a variable DC voltage supply
11 via a voltage supply lead 9 and a filter 10 for cutting off a
high-frequency signal, such as a coil. Thus, by applying a high
power to the conductive film 8c, it is possible to adsorb the wafer
W onto an upper surface on an upper film 8a in the electrostatic
chuck by a Coulomb force. Besides, it has been described as to a
case where the apparatus shown in FIG. 1 employs an electrostatic
chuck 8 as a chuck unit for adsorbing a object to be processed, the
present invention should not be construed to be limited thereto.
For example, it is also possible to adopt a mechanical chuck unit
for mechanically holding a object to be processed by means of an
annular clamp member capable of a vertical movement. However, it is
more preferable to adopt the electrostatic chuck 8 in that it can
reduce damages on the wafer W.
[0037] In addition, the electrostatic chuck sheet 8 has a thermally
conductive gas supply opening 12 formed in concentric circles.
Connected to the thermally conductive gas supply opening 12 is a
thermally conductive gas feed pipe 13 for supplying a thermally
conductive gas such as helium from a gas source not shown in the
drawings to a small space formed between a back side of the object
to be processed W and the chuck surface on the electrostatic chuck
8, thereby enhancing the efficiency of thermal conduction from the
mounting table 4 to the object to be processed W.
[0038] Moreover, on the mounting table 4, an annular focus ring 14
is set to enclose a periphery of the wafer W on the electrostatic
chuck 8. The focus ring 14, made of insulating or conductive
material that does not attract reactive ions, functions to make,
for example, the reactive ions effectively projected only onto the
semiconductor wafer W inside the focus ring. Placed between the
mounting table 4 and an inner wall of the processing chamber 2 is a
gas exhaust ring 15 having a plurality of baffle holes such that
the gas exhaust ring 15 encloses the mounting table 4 and contacts
an outer peripheral portion of the focus ring 14. The gas exhaust
ring 15 renders exhaust streams arranged properly so that, for
example, a processing gas is uniformly discharged from the inside
of the processing chamber.
[0039] Further, the mounting table 4 is connected to a power feed
rod made of conductive material and formed hollow, which is coupled
to a second high-frequency power supply 18 via a matching unit 17
having, e.g., a blocking capacitor. During the process, a
high-frequency power of, e.g., 2 MHz can be supplied to the
mounting table 4 via the power fed rod 16. Additionally, a detector
19 is inserted between the matching unit 17 and the mounting table
4. Information on an output of the second high-frequency power
supply 18 is detected by the detector 19 and then sent back to a
controller 20 to be used during a control on the process. In
addition, as will be described later, the controller 20 includes an
output controller for controlling a high-frequency power output
applied to an upper electrode 21 and the mounting table 4. As can
be seen above, the mounting table 4 functions as a lower electrode
so that, as will be explained later, glow discharge takes place
between the mounting table 4 and the upper electrode 21 positioned
to face the object to be processed W, thereby rendering the
processing gas introduced into the processing chamber into a plasma
state to enable an etching process on the object to be processed by
using the plasma.
[0040] The upper electrode 21 is placed on a mounting surface of
the mounting table 4 constituting a lower electrode (hereinafter,
the mounting table will be also called "the lower electrode") in a
manner that there is a certain distance, for example, that of about
5 to 150 mm, between the upper electrode 21 and the lower electrode
4. Moreover, the distance between the upper electrode 21 and the
lower electrode 4 can be adjusted by elevating the lower electrode
4 by the elevation mechanism 3. In addition, it is possible to
control plasma uniformity during a process by adjusting the
above-mentioned distance pursuant to a film quality of a object to
be processed.
[0041] Furthermore, similarly to the lower electrode 4, the upper
electrode 21 is connected to a first high-frequency power supply 29
via a matching unit 28 having, e.g., a blocking capacitor. During
the process, a high-frequency power of, e.g., 60 MHz can be
supplied to the upper electrode 21. Additionally, a detector 30 is
inserted between the matching unit 28 and the upper electrode 21.
Information on an output of the first high-frequency power supply
29 is detected by the detector 19 and then sent back to the
controller 20 to be used during process controls such as plasma
ignition and stopping.
[0042] In addition, the upper electrode 21 is formed hollow and a
processing feed pipe gas 22 is connected to a hollow portion of the
upper electrode 21 so that a processing gas including, for example,
at least either hydrogen bromide (HBr) or chlorine (Cl.sub.2) can
be introduced from a processing gas source 23 via a mass flow
controller (MFC) 24. Further, placed about the middle of the hollow
portion is a baffle plate 25 with a plurality of tiny holes for
promoting a uniform diffusion of the processing gas, and, below the
baffle plate 25 is installed a processing gas inlet 27 constituted
by a plate member having a plurality of small holes 26 for
injecting the processing gas. Still further, below the processing
chamber 2 is provided a gas exhaust port 31 for communicating with
a gas exhaust unit including, e.g., a vacuum pump, thereby making
it possible to vacuum pump in the processing chamber down to a set
vacuum level, e.g., to a depressurized atmosphere below 100
mTorr.
[0043] Moreover, below one side of the processing chamber 2 is set
a load-lock chamber 33 via a gate valve 32. The load-lock chamber
33 houses a transfer mechanism 24 having a transfer arm 34 (or
handling arm). The mounting table is moved down by the elevation
mechanism 3 when loading or unloading the wafer W, because, as
shown in FIG. 1, the gate valve 32 has an opening below the
processing chamber 2. On the contrary, when processing the wafer,
the elevation mechanism 3 elevates the mounting table 4 up to a
certain height where the distance between the upper electrode 21
and the lower electrode 4 is optimal.
[0044] With the above-described configuration of the plasma etching
apparatus, the handling arm 34 loads the wafer W as an object to be
processed from the load-lock chamber 33 into the processing chamber
2 via the gate valve 32. At this time, the mounting table 4 has
been moved down to a loading position by the elevation mechanism 3.
The handling arm 34 mounts the wafer W on an adsorption surface of
the electrostatic chuck 8 on the mounting table 4, and then, a high
voltage is applied to the conductive film 8c in the electrostatic
chuck 8 by the DC voltage supply 11 for high voltage so that the
wafer W is adsorbed onto the chuck surface by a Coulomb force.
Subsequently, the elevation mechanism raises the mounting table 4
up to a processing position. Thereafter, a pressure in the
processing chamber is lowered down to a predetermined depressurized
atmosphere, e.g., 100 mTorr and the gas source 23 introduces a
gaseous mixture of Cl.sub.2 and HBr without carbon as a processing
gas via the upper electrode 21.
[0045] Afterwards, pursuant to the control of the controller 20, a
predetermined high-frequency power is applied to the upper
electrode 21 by the first high-frequency power supply 29 and
another predetermined high-frequency power is applied to the
mounting table 4 by the second high-frequency power supply 18.
Thus, plasma is generated from the processing gas so that a plasma
processing is performed on the wafer W. Later, the controls as to
how the high-frequency powers are applied to the two electrodes
will be described.
[0046] By using the plasma generated as above, an etching process
is carried out on the wafer W. During this, the high-frequency
powers applied to the two electrodes are monitored by the detectors
19 and 30 so that signals thereof are sent to the controller 20,
thereby maintaining an optimal processing condition. After the
plasma processing on the wafer W has been finished, the supply of
the processing gas is stopped, the inside of the processing chamber
is purged, the mounting table 4 is moved down to an unloading
position and then the handling arm 34 unloads the wafer W
completely processed from the processing chamber 2 to the load-lock
chamber 33, thereby finishing the whole process.
[0047] Hereinafter, a description will be given as to a method for
controlling the application of high-frequency powers to the
electrodes (which are the upper electrode 21 and the lower
electrode 4 in case of the plasma processing apparatus in
accordance with the preferred embodiment shown in FIG. 1) with
reference to FIGS. 2 to 4. FIGS. 2 to 4 show specific examples of
raise timings of the high-frequency powers applied to the two
electrodes. FIGS. 2 to 4 describe embodiments where the two
high-frequency powers are raised in a stepwise manner.
[0048] In accordance with these embodiments, the outputs of the two
high-frequency power supplies 18 and 29 are raised up to a set
level (a recipe level) for the plasma processing on the wafer W by
being raised at least three times in a stepwise manner. While the
high-frequency power are raised up to the set level in a stepwise
manner as described above, the controller 20 controls the raise
timings of the outputs of the two high-frequency power supplies 18
and 29 such that the output of the second high-frequency power
supply 18 applied to the lower electrode 4 is raised earlier than
the output of the first high-frequency power supply 29.
[0049] More particularly, for example, a certain level of
high-frequency power is firstly applied to the lower electrode 4
while the high-frequency power applied to the upper electrode 21
remains 0W, as shown in FIG. 2. Subsequently, after a certain
period of time, a certain amount of high-frequency power is applied
to the upper electrode 21 while the high-frequency power applied to
the lower electrode 4 remains substantially the same. By doing
this, a plasma is ignited. Thereafter, high-frequency powers are
alternately applied stepwise to the lower electrode 4 and to the
upper electrode 21 respectively, thereby reaching the set levels
P.sub.1W and P.sub.2W eventually.
[0050] Thus, plasma can be generated efficiently, thereby further
reducing damages on an object to be processed and further reducing
the loads on the high-frequency power supply, matching unit or so
forth.
[0051] Further, as shown in FIG. 2, the output of one of the
high-frequency power supplies 18 and 29 is controlled to be raised
while the output of the other high-frequency power supply is kept
constant. Thus, it is possible to control the output of one of the
high-frequency power supplies to change while the output of the
other high-frequency power supply is made stable by a matching
operation of the matching unit, thereby efficiently reducing the
loads on the high-frequency power supply or the matching unit. It
is preferable that the period between raising the high-frequency
power to the upper electrode and then raising the high-frequency
power to the lower electrode is either equal to or longer than the
period between raising the high-frequency power to the lower
electrode and then raising the high-frequency power to the upper
electrode. It is more preferable that the two periods are the
same.
[0052] In addition, a high-frequency power difference, i.e., the
difference between the two outputs of the two high-frequency power
supplies 18 and 29 is controlled to remain below a certain value.
Thus, the high-frequency power applied to the lower electrode 4 can
be restrained not to become too high compared to the high-frequency
power applied to the upper electrode 21, thereby further reducing a
load on the power supply or the matching unit.
[0053] Furthermore, in FIG. 2, P.sub.1W is the set level of the
high-frequency power applied to the upper electrode 21 and P.sub.2W
is the set level of the high-frequency power applied to the lower
electrode 4 (the same is applied for FIGS. 3, 5 and 6 as will be
described later). P.sub.1W and P.sub.2W can be set to appropriate
values pursuant to the type of a plasma processing, processing
condition and the like. For example, P.sub.1W applied to the upper
electrode 21 is 3300 W and P.sub.2W applied to the lower electrode
4 is 3800 W.
[0054] It is preferable that the time unit (the time interval a
illustrated in FIG. 2) by which each of the high-frequency powers
controlled is raised, for example, is between 0.1 and 0.5 second
inclusive. As shown in FIG. 2, the high-frequency powers can be
controlled to be raised every time when the time interval "a"
elapses (for example, every 0.1 second). The time interval "a" is
set to be an appropriate span based on magnitudes of the set levels
of the high-frequency powers or required periods of time for the
high-frequency powers to reach the set levels.
[0055] Preferably, a period of time for each high-frequency power
to reach its set level is 2 to 5 seconds. In case shown in FIG. 2,
the high-frequency power applied to the lower electrode 4 reaches
its set level P.sub.2W earlier than that applied to the upper
electrode 21. A period of time from an application of the
high-frequency power to the lower electrode 4 until the
high-frequency power applied to the upper electrode 21 reaches the
set level P.sub.1W is, for example, 2.5 seconds.
[0056] A raised level of each high-frequency power at each step may
vary among raise times. However, it is more preferable that the
raised level of each high-frequency power stays constant. For
example, the raised level may increase slowly at each rising stage.
It is also possible to control the output of each high-frequency
power supply such that it ranges inclusively between 25% and 50% of
each set level until right before it reaches the set level and then
goes up to the set level at once, as shown in FIG. 3. In this case,
it is preferable that the output of each high-frequency power
supply be not less than an output level where plasma can be ignited
(for example, not less than 200W) and not more than 25% of each set
level. More particularly, as shown in FIG. 4, a high-frequency
power of 400W is initially applied to the lower electrode 4 at time
0. Thereafter, high-frequency powers are alternately applied to the
lower electrode 4 and the upper electrode 21 every 0.4 second in an
increasing manner. Right before the high-frequency powers reach
their set levels (in this case, 3300W and 3800W), they are set to
range inclusively between 25% and 50% of their set levels, e.g.,
1200W. Then, the high-frequency powers are controlled to go up to
the set level at once.
[0057] In this way, the high-frequency power applied to each
electrode is raised up to an amount sufficient for igniting a
plasma at the initial stage, and then raised slowly to range
inclusively between 25% and 50% of its set level right before
reaching the set level, and then raised up to the set level at
once, thereby ensuring that a plasma is ignited, reducing damages
on the object to be processed, or reducing loads on the power
supplies or matching units, and shortening the required periods of
time to reach the set levels.
[0058] Hereinafter, other examples of the method for controlling
application of the high-frequency power to each electrode will be
described with reference to FIGS. 5 to 7. FIGS. 5 to 7 illustrate
other examples of raise timings of high-frequency powers applied to
the electrodes. FIGS. 5 to 7 depict other examples where the
high-frequency powers applied to each electrode is raised in a
continuous manner up to the set level or raised in a stepwise
manner during a certain part of time and in a continuous manner
during the other part of time.
[0059] As shown in FIG. 5, it is allowable that, after the
high-frequency powers begin to be simultaneously applied to the
upper electrode 21 and the lower electrode 4, the high-frequency
power applied to each electrode are raised in a continuous manner
until it reaches its set level P.sub.1W or P.sub.2W. In this way,
since each high-frequency power is raised slowly, damages on the
object to be processed can be further reduced and loads on the
high-frequency power supplies or matching units can be further
alleviated.
[0060] In this case, it is preferable that the output (the
high-frequency powers) ratios between the high-frequency power
supplies 18 and 29 are kept constant or their slopes of the outputs
(the high-frequency powers) of the high-frequency power supplies 18
and 29 as they go up are kept identical to each other. Thus, the
high-frequency power applied to the lower electrode 4 can be
controlled to be not too high relative to the high-frequency power
applied to the upper electrode 21. In this way, loads on the power
supplies or the matching units can be further reduced. Further, in
case the output ratios (the high-frequency powers) between the
high-frequency power supplies 18 and 29 are controlled to be
constant or their output (the high-frequency powers) slopes of the
high-frequency power supplies 18 and 29 as they go up are
controlled to be identical to each other, the overall period for
the high-frequency power applied to each electrode to reach the set
level P.sub.1W or P.sub.2W is set based on the set level P.sub.1W
or P.sub.2W. Therefore, the periods of time for the high-frequency
powers applied to the electrodes to reach the set levels P.sub.1W
and P.sub.2W may be identical to or different from each other.
[0061] As described above, it is preferable that the outputs of the
high-frequency power supplies 18 and 29 may be raised in a stepwise
manner during a certain part of time and in a continuous manner
during the other part of time. In this case, it is preferable that
the part of time during which the outputs are raised in a stepwise
manner be an initial period during which plasma is ignited, as
shown in FIG. 6. Thus, the ignition of the plasma can be performed
efficiently at the initial stage during which the high-frequency
powers begin to be applied.
[0062] In addition, as shown in FIG. 7, it is also preferable that
the high-frequency power applied to one of the electrodes is raised
in a stepwise manner and the high-frequency power applied to the
other electrode is raised in a continuous manner. In this case, the
output of the first high-frequency power supply 29 applied to the
upper electrode 21 may be raised in a stepwise manner and the
second high-frequency power supply 18 applied to the lower
electrode 4 may be raised in a continuous manner.
[0063] 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.
[0064] For example, although the preferred embodiments were
described as to the case where the high-frequency powers are
applied from the electrodes 18 and 29 to the upper electrode 21 and
the lower electrode 4, the invention is not limited thereto but
includes the case where two high-frequency powers (for example, a
high-frequency power for generating plasma and another
high-frequency power for attracting charged particles such as ions)
are applied to the lower electrode 4. For example, the first
high-frequency power supply 29 may be used for generating plasma
and the second high-frequency power supply 18 may be used for
attracting charged particles such as ions. In this case, a
frequency of the first high-frequency power supply 29 is set, for
example, between 60 and 100 MHz inclusive and a frequency of the
second high-frequency power supply 18 is set, for example, between
2 and 3.2 MHz inclusive.
[0065] Further, although the preferred embodiments were described
as to a plasma etching apparatus, the invention can also be applied
to any apparatuses that introduce a processing gas into a
processing chamber and include an upper electrode, lower electrode,
first and second high-frequency power supply for applying a
high-frequency power to each of the electrodes to perform a plasma
processing, for example, a plasma CVD apparatus, an ashing
apparatus and so forth.
[0066] Furthermore, although the preferred embodiments were
described as to an etching process on polysilicon, the invention
can also be applied to an etching process on an oxide film,
photoresist or refractory metals such as tungsten silicide,
molybdenum silicide, titan silicide and the like.
[0067] The present invention can be applied to a plasma processing
apparatus and a control method thereof.
* * * * *