U.S. patent application number 13/171990 was filed with the patent office on 2012-01-05 for plasma treatment apparatus and plasma treatment method.
This patent application is currently assigned to KABUSHIKI KAISHA TOSHIBA. Invention is credited to Hideo Eto, Nobuyasu Nishiyama, Makoto Saito, Keiji Suzuki.
Application Number | 20120000887 13/171990 |
Document ID | / |
Family ID | 45398906 |
Filed Date | 2012-01-05 |
United States Patent
Application |
20120000887 |
Kind Code |
A1 |
Eto; Hideo ; et al. |
January 5, 2012 |
PLASMA TREATMENT APPARATUS AND PLASMA TREATMENT METHOD
Abstract
According to one embodiment, there is provided a plasma
treatment apparatus including an electrode, a first power supply
circuit, a plasma generating unit, a second power supply circuit, a
sensing unit, and a control unit. The electrode is arranged inside
a treatment chamber. On the electrode, a substrate to be treated is
placed. The first power supply circuit supplies power to the
electrode. The plasma generating unit generates plasma in a space
separated from the electrode inside the treatment chamber. The
second power supply circuit supplies power to the plasma generating
unit. The sensing unit senses a parameter output from the first
power supply circuit. The control unit controls power supplied from
the second power supply circuit so that the parameter sensed by the
sensing unit becomes close to or substantially equal to a target
value.
Inventors: |
Eto; Hideo; (Mie, JP)
; Saito; Makoto; (Mie, JP) ; Suzuki; Keiji;
(Kanagawa, JP) ; Nishiyama; Nobuyasu; (Mie,
JP) |
Assignee: |
KABUSHIKI KAISHA TOSHIBA
Tokyo
JP
|
Family ID: |
45398906 |
Appl. No.: |
13/171990 |
Filed: |
June 29, 2011 |
Current U.S.
Class: |
216/61 ;
156/345.28 |
Current CPC
Class: |
H01J 37/32183 20130101;
H01J 37/321 20130101; H01J 37/32935 20130101 |
Class at
Publication: |
216/61 ;
156/345.28 |
International
Class: |
C23F 1/00 20060101
C23F001/00; C23F 1/08 20060101 C23F001/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2010 |
JP |
2010-150094 |
Aug 20, 2010 |
JP |
2010-185134 |
Claims
1. A plasma treatment apparatus comprising: an electrode which is
arranged inside a treatment chamber and on which a substrate to be
treated is placed; a first power supply circuit which supplies
power to the electrode; a plasma generating unit which generates
plasma in a space separated from the electrode inside the treatment
chamber; a second power supply circuit which supplies power to the
plasma generating unit; a sensing unit which senses a parameter
output from the first power supply circuit; and a control unit
which controls power supplied from the second power supply circuit
so that the parameter sensed by the sensing unit becomes close to
or substantially equal to a target value.
2. The plasma treatment apparatus according to claim 1, wherein the
parameter sensed by the sensing unit includes a voltage.
3. The plasma treatment apparatus according to claim 2, wherein the
control unit increases power supplied from the second power supply
circuit when the voltage sensed by the sensing unit is higher than
the target value and decreases power supplied from the second power
supply circuit when the voltage sensed by the sensing unit is lower
than the target value.
4. The plasma treatment apparatus according to claim 1, wherein the
parameter sensed by the sensing unit includes a current.
5. The plasma treatment apparatus according to claim 4, wherein the
control unit decreases power supplied from the second power supply
circuit when the current sensed by the sensing unit is greater than
the target value and increases power supplied from the second power
supply circuit when the current sensed by the sensing unit is
smaller than the target value.
6. The plasma treatment apparatus according to claim 1, wherein the
first power supply circuit includes a generating unit which
generates power, a second sensing unit which senses power generated
by the generating unit, and a second control unit which controls
power generated by the generating unit in accordance with the
sensing result of the second sensing unit, a control operation of
the control unit and a control operation of the second control unit
being performed in parallel in a mutually independent form.
7. A plasma treatment method in a plasma treatment apparatus that
includes an electrode, a first power supply circuit, a plasma
generating unit, and a second power supply circuit, the electrode
being arranged inside a treatment chamber and on the electrode a
substrate to be treated being placed, the first power supply
circuit supplying power to the electrode, the plasma generating
unit generating plasma in a space separated from the electrode
inside the treatment chamber, the second power supply circuit
supplying power to the plasma generating unit, the plasma treatment
method comprising: sensing a parameter output from the first power
supply circuit; and controlling power supplied from the second
power supply circuit so that the sensed parameter becomes close to
or substantially equal to a target value.
8. The plasma treatment method according to claim 7, wherein, in
the sensing of the parameter, a voltage output from the first power
supply circuit is sensed, and in the controlling of power, when the
sensed voltage is higher than the target value, power supplied from
the second power supply circuit increases, and when the sensed
voltage is lower than the target value, power supplied from the
second power supply circuit decreases.
9. The plasma treatment method according to claim 7, wherein, in
the sensing of the parameter, a current output from the first power
supply circuit is sensed, and in the controlling of power, when the
sensed current is greater than the target value, power supplied
from the second power supply circuit decreases, and when the sensed
current is smaller than the target value, power supplied from the
second power supply circuit increases.
10. A plasma treatment apparatus comprising: an electrode which is
arranged inside a treatment chamber and on which a substrate to be
treated is placed; a power supply circuit which supplies power to
the electrode; a plasma generating unit which generates plasma in a
space separated from the electrode inside the treatment chamber;
and a detecting unit which detects a bias voltage that is a
difference between a potential of the plasma generated by the
plasma generating unit and a potential of the electrode to which
power is supplied from the power supply circuit, wherein the power
supply circuit includes a main unit which generates power to be
supplied to the electrode, and a correcting unit which corrects a
capacitance value of the power supply circuit so that the bias
voltage detected by the detecting unit becomes close to or
substantially equal to a target value.
11. The plasma treatment apparatus according to claim 10, wherein
the detecting unit includes a first detection terminal which
extends to the space separated from the electrode inside the
treatment chamber, and a second detection terminal which is
electrically connected to the electrode, and wherein the detecting
unit obtains a difference between a voltage detected by the first
detection terminal and a voltage detected by the second detection
terminal to detect the bias voltage.
12. The plasma treatment apparatus according to claim 10, wherein
the correcting unit includes a first variable-capacitance element
which is connected in series with the main unit with respect to the
electrode, a second variable-capacitance element which is connected
in parallel with the main unit with respect to the electrode, and a
changing unit which changes at least one of a capacitance value of
the first variable-capacitance element and a capacitance value of
the second variable-capacitance element so that the bias voltage
detected by the detecting unit becomes close to or substantially
equal to the target value.
13. The plasma treatment apparatus according to claim 12, wherein
the changing unit performs at least an operation to increase the
capacitance value of the second variable-capacitance element when
the bias voltage detected by the detecting unit is higher than the
target value and performs at least an operation to increase the
capacitance value of the first variable-capacitance element when
the bias voltage detected by the detecting unit is lower than the
target value.
14. The plasma treatment apparatus according to claim 10, wherein
the correcting unit includes a storage unit which stores a
plurality of different target values, and a determining unit which
determines a target value corresponding to a processing condition
of plasma treatment from among the plurality of different target
values stored in the storage unit, the capacitance value of the
power supply circuit being corrected so that the bias voltage
detected by the detecting unit becomes close to or substantially
equal to the target value determined by the determining unit.
15. The plasma treatment apparatus according to claim 10, wherein
the correcting unit includes a storage unit which stores a
plurality of different target values, and a determining unit which
determines a target value corresponding to an elapsed time of
plasma treatment from among the plurality of different target
values stored in the storage unit, the capacitance value of the
power supply circuit being corrected so that the bias voltage
detected by the detecting unit becomes close to or substantially
equal to the target value determined by the determining unit.
16. The plasma treatment apparatus according to claim 10, further
comprising: a storage unit which stores correlation information
regarding a correlation between the bias voltage and a processing
shift amount; and a controller which predicts the processing shift
amount on the basis of the bias voltage detected by the detecting
unit and the correlation information stored in the storage unit,
and adjusts a processing condition so that the processing shift
amount falls within a range of a threshold value.
17. A plasma treatment method in a plasma treatment apparatus that
includes an electrode and a power supply circuit, the electrode
being arranged inside a treatment chamber, and on the electrode a
substrate to be treated being placed, the power supply circuit
supplying power to the electrode, the plasma treatment method
comprising: supplying power from the power supply circuit to the
electrode and generating plasma in a space separated from the
electrode inside the treatment chamber; detecting a bias voltage
that is a difference between the potential of the generated plasma
and the potential of the electrode to which power is supplied;
correcting a capacitance value of the power supply circuit so that
the detected bias voltage becomes close to or substantially equal
to a target value; and processing the substrate to be treated using
the plasma treatment apparatus after the correcting is
performed.
18. The plasma treatment method according to claim 17, wherein the
power supply circuit includes a main unit which generates power to
be supplied to the electrode, and a correcting unit which
compensates for a capacitance value of the main unit to correct the
capacitance value of the power supply circuit so that the detected
bias voltage becomes close to or substantially equal to the target
value, wherein the correcting unit includes a first
variable-capacitance element which is connected in series with the
main unit with respect to the electrode, and a second
variable-capacitance element which is connected in parallel with
the main unit with respect to the electrode, and wherein, in the
correcting of the capacitance value of the power supply circuit, at
least one of a capacitance value of the first variable-capacitance
element and a capacitance value of the second variable-capacitance
element is changed so that the detected bias voltage becomes close
to or substantially equal to the target value.
19. The plasma treatment method according to claim 17, further
comprising: determining a target value corresponding to a
processing condition of plasma treatment from among a plurality of
different target values, and comparing the detected bias voltage
with the determined target value before the correcting of the
capacitance value of the power supply circuit, wherein the
capacitance value of the power supply circuit is corrected in
accordance with the comparison result so that the detected bias
voltage becomes close to or substantially equal to the determined
target value.
20. The plasma treatment method according to claim 17, further
comprising: determining a target value corresponding to an elapsed
time of plasma treatment from among a plurality of different target
values, and comparing the detected bias voltage with the determined
target value before the correcting of the capacitance value of the
power supply circuit, wherein the capacitance value of the power
supply circuit is corrected in accordance with the comparison
result so that the detected bias voltage becomes close to or
substantially equal to the determined target value.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from the prior Japanese Patent Application No.
2010-150094, filed on Jun. 30, 2010; and the prior Japanese Patent
Application No. 2010-185134, filed on Aug. 20, 2010; the entire
contents of which are incorporated herein by reference.
FIELD
[0002] Embodiments described herein relate generally to a plasma
treatment apparatus and a plasma treatment method.
BACKGROUND
[0003] In recent years, with the progress in miniaturization of
semiconductor devices, there is a demand for improvement of
processing precision in a processing technique of semiconductor
devices. In particular, in an etching technique using a plasma
treatment apparatus, such as a reactive ion etching (RIE)
apparatus, a variation in processing dimension or etching amount
between (a plurality of) different plasma treatment apparatuses of
the same model becomes important so as not to be negligible in
light of necessary processing precision even under the same
processing condition.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a diagram showing the configuration of a plasma
treatment apparatus according to a first embodiment;
[0005] FIG. 2 is a flowchart showing an operation of a control
device in the first embodiment;
[0006] FIG. 3 is a flowchart showing an operation of a control
device in a second embodiment;
[0007] FIG. 4 is a diagram showing the configuration of a plasma
treatment apparatus according to a modification of the first
embodiment and the second embodiment;
[0008] FIGS. 5A and 5B are diagrams showing an operation of a
plasma treatment apparatus according to a comparative example;
[0009] FIG. 6 is a diagram showing an operation of a plasma
treatment apparatus according to a comparative example;
[0010] FIG. 7 is a diagram showing the configuration of a plasma
treatment apparatus according to a third embodiment;
[0011] FIG. 8 is a diagram showing the configuration of a
correcting unit in the third embodiment;
[0012] FIG. 9 is a flowchart showing a method of manufacturing a
semiconductor device using the plasma treatment apparatus according
to the third embodiment;
[0013] FIG. 10 is a diagram showing the configuration of a plasma
treatment apparatus according to a fourth embodiment;
[0014] FIG. 11 is a diagram showing the configuration of a
correcting unit in the fourth embodiment;
[0015] FIG. 12 is a diagram showing the data structure of a storage
unit in the fourth embodiment;
[0016] FIG. 13 is a flowchart showing a method of manufacturing a
semiconductor device using the plasma treatment apparatus according
to the fourth embodiment;
[0017] FIG. 14 is a diagram showing the configuration of a
correcting unit in a fifth embodiment;
[0018] FIG. 15 is a diagram showing the data structure of a storage
unit in the fifth embodiment;
[0019] FIG. 16 is a flowchart showing a method of manufacturing a
semiconductor device using a plasma treatment apparatus according
to the fifth embodiment;
[0020] FIG. 17 is a diagram showing the configuration of a plasma
treatment apparatus according to a sixth embodiment;
[0021] FIG. 18 is a diagram showing the data structure of a storage
unit in the sixth embodiment;
[0022] FIG. 19 is a flowchart showing a method of manufacturing a
semiconductor device using the plasma treatment apparatus according
to the sixth embodiment; and
[0023] FIG. 20 is a diagram showing an operation of a plasma
treatment apparatus according to a comparative example.
DETAILED DESCRIPTION
[0024] In general, according to one embodiment, there is provided a
plasma treatment apparatus including an electrode, a first power
supply circuit, a plasma generating unit, a second power supply
circuit, a sensing unit, and a control unit. The electrode is
arranged inside a treatment chamber. On the electrode, a substrate
to be treated is placed. The first power supply circuit supplies
power to the electrode. The plasma generating unit generates plasma
in a space separated from the electrode inside the treatment
chamber. The second power supply circuit supplies power to the
plasma generating unit. The sensing unit senses a parameter output
from the first power supply circuit. The control unit controls
power supplied from the second power supply circuit so that the
parameter sensed by the sensing unit becomes close to or
substantially equal to a target value.
[0025] Exemplary embodiments of a plasma treatment apparatus will
be explained below in detail with reference to the accompanying
drawings. The present invention is not limited to the following
embodiments.
First Embodiment
[0026] A plasma treatment apparatus 1 according to a first
embodiment will be described with reference to FIG. 1. FIG. 1 is a
diagram showing the schematic configuration of the plasma treatment
apparatus 1 according to the first embodiment.
[0027] The plasma treatment apparatus 1 includes a treatment
chamber 50, an electrode 10, a power supply circuit (first power
supply circuit) 20, a plasma generating unit 30, a power supply
circuit (second power supply circuit) 40, and a control device
60.
[0028] The treatment chamber 50 is a chamber which is used to
generate plasma PL therein, and is formed of a treatment container
2. The treatment container 2 is configured such that a treatment
gas can be supplied from a supply source (not shown) to the
treatment chamber 50 and the treatment gas after treatment process
can be exhausted from the treatment chamber 50 to an exhaust device
(not shown).
[0029] The electrode 10 is arranged on the bottom surface of the
treatment chamber 50 so as to be insulated from the treatment
container 2 through an insulating material (not shown). A substrate
WF to be treated (for example, a semiconductor substrate) is placed
on the electrode 10. The electrode 10 is formed of, for example,
metal.
[0030] The power supply circuit 20 generates radio-frequency power
and supplies the radio-frequency power to the electrode 10. The
radio-frequency power is power which is used to accelerate ions
(for example, F.sup.+, CF3.sup.+, or the like), which are generated
from the treatment gas along with radicals when the plasma PL is
generated in the treatment chamber 50, toward the electrode 10
(toward the substrate WF to be treated). The frequency of the
radio-frequency power is, for example, 13.56 MHz.
[0031] The power supply circuit 20 has a radio-frequency power
supply 22 and a matching circuit 21.
[0032] The radio-frequency power supply 22 has a generating unit
22a, a sensing unit 22b, and a feedback control unit 22c. The
generating unit 22a generates radio-frequency power. The sensing
unit 22b senses power (radio-frequency power) Pb generated by the
generating unit 22a. The feedback control unit 22c controls power
generated by the generating unit 22a in accordance with the sensing
result of the sensing unit 22b so that the power Pb sensed by the
sensing unit 22b is substantially identical to set power
[0033] Pbset. The details of the sensing unit 22b and the feedback
control unit 22c will be described below.
[0034] The matching circuit 21 has, for example, a variable
capacitor and a variable coil. The matching circuit 21 performs
impedance adjustment (impedance matching) using the variable
capacitor and the variable coil so that impedance on the
radio-frequency power supply 22 side with respect to the matching
circuit 21 matches with impedance on the electrode 10 side with
respect to the matching circuit 21.
[0035] The plasma generating unit 30 generates the plasma PL in a
space 51 separated from the electrode 10 inside the treatment
chamber 50. Specifically, the plasma generating unit 30 has an
antenna coil 31 and a dielectric wall 32. The antenna coil 31
generates electromagnetic waves (high-frequency magnetic field)
using the radio-frequency power supplied from the power supply
circuit 40. The electromagnetic waves generated by the antenna coil
31 pass through the dielectric wall 32 and are introduced into the
space 51 of the treatment chamber 50. In the space 51 of the
treatment chamber 50, the treatment gas is discharged to generate
the plasma PL, which includes ions (for example, F.sup.+,
CF3.sup.+, or the like) and radicals (for example, F*, O*, or the
like). The dielectric wall 32 also serves as the upper wall of the
treatment container 2.
[0036] The power supply circuit 40 generates radio-frequency power
and supplies the radio-frequency power to the plasma generating
unit 30. The radio-frequency power is power which is used when the
plasma generating unit 30 generates plasma PL in the treatment
chamber 50. The frequency of the radio-frequency power is, for
example, 13.56 MHz.
[0037] The power supply circuit 40 has a matching circuit 41 and a
radio-frequency power supply 42. The radio-frequency power supply
42 generates radio-frequency power and supplies the radio-frequency
power to the antenna coil 31. The matching circuit 41 has, for
example, a variable capacitor and a variable coil. The matching
circuit 41 performs impedance adjustment (impedance matching) using
the variable capacitor and the variable coil so that impedance on
the radio-frequency power supply 42 side with respect to the
matching circuit 41 matches with impedance on the antenna coil 31
side with respect to the matching circuit 41.
[0038] The control device 60 controls the plasma treatment
apparatus 1. Specifically, the control device 60 has an input unit
65, a probe (sensing unit) 63, and a feedback control circuit
(control unit) 64.
[0039] The set power Pbset and a set voltage Vbset are input from a
user to the input unit 65 in the control device 60. Alternatively,
the input unit 65 receives the set power Pbset and the set voltage
Vbset from a host computer or another plasma treatment apparatus
through a communication line. The set voltage Vbset and the set
power Vbset are respectively determined in advance as a common
value between different plasma treatment apparatuses. The input
unit 65 supplies the value of the set power Pbset to the feedback
control unit 22c in the radio-frequency power supply 22, and
supplies the value of the set voltage Vbset to the feedback control
circuit 64.
[0040] The sensing unit 22b in the radio-frequency power supply 22
senses the power (radio-frequency power) Pb generated by the
generating unit 22a. The sensing unit 22b supplies the value of the
sensed power Pb to the feedback control unit 22c.
[0041] The feedback control unit 22c in the radio-frequency power
supply 22 receives the value of the set power Pbset from the input
unit 65 and holds the value of the set power Pbset as a target
value. If the value of the sensed power Pb is received from the
sensing unit 22b, the feedback control unit 22c compares the power
Pb with the set power Pbset, and controls power generated by the
generating unit 22a so that the power Pb sensed by the sensing unit
22b is substantially identical to the set power Pbset.
Specifically, when the sensed power Pb is higher than the set power
Pbset, the feedback control unit 22c controls the generating unit
22a to decrease power to be generated. When the sensed power Pb is
lower than the set power Pbset, the feedback control unit 22c
controls the generating unit 22a to increase power to be
generated.
[0042] The probe 63 in the control device 60 senses a voltage
(parameter) Vb output from the power supply circuit 20. For
example, the probe 63 senses the voltage on a node N1 between the
electrode 10 and the power supply circuit 20 as the voltage Vb
output from the power supply circuit 20. The probe 63 supplies the
value of the sensed voltage Vb to the feedback control circuit
64.
[0043] The feedback control circuit 64 in the control device 60
receives the value of a set voltage Vbset from the input unit 65
and holds the value of the set voltage Vbset as a target value. If
the value of the sensed voltage Vb is received from the probe 63,
the feedback control circuit 64 compares the voltage Vb with the
set voltage Vbset, and controls power supplied from the power
supply circuit 40 so that the voltage Vb sensed by the probe 63
becomes close to or substantially equal to the set voltage Vbset.
Specifically, when the sensed voltage Vb is higher than the set
voltage Vbset, the feedback control circuit 64 controls the
radio-frequency power supply 42 in the power supply circuit 40 to
increase power to be generated. When the sensed voltage Vb is lower
than the set voltage Vbset, the feedback control circuit 64
controls the radio-frequency power supply 42 in the power supply
circuit 40 to decrease power to be generated.
[0044] For example, when power output from the power supply circuit
20 is substantially identical to the set power Pbset, if the
voltage Vb sensed by the probe 63 is higher than the set voltage
Vbset, this equivalently means that an ion current formed by ions
accelerated inside the treatment chamber 50 is smaller than a
target value corresponding to the set voltage Vbset. Thus, when the
sensed voltage Vb is higher than the set voltage Vbset, if power
supplied from the power supply circuit 40 to the plasma generating
unit 30 increases, and the density of plasma generated inside the
treatment chamber 50 increases, the ion current (the density of
ions to be accelerated) can become close to or substantially equal
to the target value.
[0045] Alternatively, for example, when power output from the power
supply circuit 20 is substantially identical to the set power
Pbset, if the voltage Vb sensed by the probe 63 is lower than the
set voltage Vbset, this equivalently means that an ion current
formed by ions accelerated inside the treatment chamber 50 is
greater than a target value corresponding to the set voltage Vbset.
Thus, when the sensed voltage Vb is lower than the set voltage
Vbset, if power supplied from the power supply circuit 40 to the
plasma generating unit 30 decreases, and the density of plasma
generated inside the treatment chamber 50 decreases, the ion
current (the density of ions to be accelerated) can become close to
or substantially equal to the target value.
[0046] Next, the operation of the control device 60 will be
described with reference to FIG. 2. FIG. 2 is a flowchart showing
the operation of the control device 60.
[0047] In Step S1, the substrate WF to be treated (for example, a
semiconductor substrate) is placed on the electrode 10 inside the
treatment chamber 50. The power supply circuit 20 generates
radio-frequency power and supplies the radio-frequency power to the
electrode 10. Along with this, the power supply circuit 40
generates radio-frequency power and supplies the radio-frequency
power to the plasma generating unit 30. The plasma generating unit
30 generates the plasma PL in the space 51 separated from the
electrode 10 inside the treatment chamber 50. Specifically, the
radio-frequency power supply 42 generates radio-frequency power and
supplies the radio-frequency power to the antenna coil 31. The
antenna coil 31 generates electromagnetic waves (high-frequency
magnetic field) using the supplied radio-frequency power. The
electromagnetic waves generated by the antenna coil 31 pass through
the dielectric wall 32 and are introduced into the space 51 of the
treatment chamber 50. In the space 51 of the treatment chamber 50,
a treatment gas is discharged to generate the plasma PL, which
includes ions (for example, F.sup.+, CF3.sup.+, or the like) and
radicals (for example, F*, O*, or the like).
[0048] In Step S2, the probe 63 senses the voltage Vb output from
the power supply circuit 20. For example, the probe 63 senses the
voltage on the node N1 between the electrode 10 and the power
supply circuit 20 as the voltage Vb output from the power supply
circuit 20. The probe 63 supplies the value of the sensed voltage
(bias-side voltage) Vb to the feedback control circuit 64.
[0049] In Step S3, the feedback control circuit 64 receives the
value of the set voltage Vbset from the input unit 65 and holds the
value of the set voltage Vbset as a target value. If the value of
the sensed voltage Vb is received from the probe 63, the feedback
control circuit 64 compares the voltage (bias-side voltage) Vb with
the set voltage (target value) Vbset. When the sensed voltage Vb is
lower than the set voltage Vbset, the feedback control circuit 64
progresses the process to Step S4. When the sensed voltage Vb is
higher than the set voltage Vbset, the feedback control circuit 64
progresses the process to Step S5. When the sensed voltage Vb is
substantially identical to the set voltage Vbset, the process
ends.
[0050] In Step S4, the feedback control circuit 64 controls the
radio-frequency power supply 42 in the power supply circuit 40 to
decrease power to be generated.
[0051] In Step S5, the feedback control circuit 64 controls the
radio-frequency power supply 42 in the power supply circuit 40 to
increase power to be generated.
[0052] In this way, the processing of Steps S2 to S5 (the operation
of the probe 63 to sense the voltage Vb output from the power
supply circuit 20 and the control operation of the feedback control
circuit 64) is repeatedly performed until the bias-side voltage Vb
is substantially identical to the set voltage (target value) Vbset.
Though not shown, the operation of the sensing unit 22b to sense
the power Pb generated by the generating unit 22a in the power
supply circuit 20 and the control operation of the feedback control
unit 22c are performed in parallel with the processing of Steps S2
to S5.
[0053] A case, as a comparative example, where the control device
60 has no feedback control circuit 64 is taken into consideration.
In this case, the control operation of the feedback control circuit
64 in the control device 60 is not performed, and the operation of
the sensing unit 22b to sense the power Pb generated by the
generating unit 22a in the power supply circuit 20 and the control
operation of the feedback control unit 22c are performed. Thus,
even when power (bias-side power) output from the power supply
circuit 20 can be substantially equalized between a plurality of
different plasma treatment apparatuses of the same model, the
voltage (bias-side voltage) output from the power supply circuit 20
tends to vary between a plurality of different plasma treatment
apparatuses of the same model. For example, as shown in FIG. 5A,
although the bias-side power is equalized as 500 W between a
plurality of different plasma treatment apparatuses A1 to A3 of the
same model, the bias-side voltage varies to 300 V, 350 V, and 250
V. Accordingly, since processing is performed with an etching rate
deviated from a user's request, the processing precision of each
plasma treatment apparatus tends to be degraded. Simultaneously, a
variation in the processing dimension or etching amount between (a
plurality of) different plasma treatment apparatuses of the same
model tends to be not negligible with respect to necessary
processing precision even under the same processing condition.
[0054] Alternatively, there is taken into consideration a case, as
a comparative example, where the power supply circuit 20 has no
sensing unit 22b and feedback control unit 22c, and the feedback
control circuit 64 controls power supplied from the power supply
circuit 20 (power generated by the generating unit 22a of the
radio-frequency power supply 22) so that the voltage Vb sensed by
the probe 63 is identical to the set voltage Vbset. In this case,
in the control device 60, the operation of the probe 63 to sense
the voltage Vb output from the power supply circuit 20 and the
operation of the feedback control circuit 64 to control the power
supply circuit 20 are performed. Thus, even when the voltage
(bias-side voltage) output from the power supply circuit 20 can be
substantially equalized between a plurality of different plasma
treatment apparatuses of the same model, power (bias-side power)
output from the power supply circuit 20 tends to vary between a
plurality of different plasma treatment apparatuses of the same
model. For example, as shown in FIG. 5B, although the bias-side
voltage is substantially equalized as 300 V between a plurality of
different plasma treatment apparatuses A4 to A6 of the same model,
the bias-side power varies to 500 W, 430 W, and 570 W. Accordingly,
since processing is performed with an etching rate deviated from a
user's request, the processing precision of each plasma treatment
apparatus tends to be degraded. Simultaneously, a variation in the
processing dimension or etching amount between (a plurality of)
different plasma treatment apparatuses of the same model tends to
be not negligible with respect to necessary processing precision
even under the same processing condition.
[0055] For example, FIG. 6 shows the evaluation result of an
etching rate of plasma treatment for a plurality of plasma
treatment apparatuses in which the bias-side power Pb varies in a
state where the bias-side voltage is constant. From FIG. 6, it can
be understood that the etching rate significantly varies between
the plasma treatment apparatuses in which the bias-side power Pb is
different.
[0056] In contrast, in the first embodiment, the control device 60
has the feedback control circuit 64, and the control operation of
the feedback control unit 22c in the power supply circuit 20 and
the control operation of the feedback control circuit 64 in the
control device 60 are performed in parallel in a mutually
independent form. That is, the feedback control unit 22c controls
power generated by the generating unit 22a so that the power Pb
sensed by the sensing unit 22b is substantially identical to the
set power Pbset. Thus, power (bias-side power) output from the
power supply circuit 20 can be substantially identical to the set
power Pbset determined in advance as a common value between
different plasma treatment apparatuses. The feedback control
circuit 64 controls power supplied from the power supply circuit 40
so that the voltage (parameter) Vb sensed by the probe 63 is
substantially identical to the set voltage (target value) Vbset.
Thus, the voltage (bias-side voltage) output from the power supply
circuit 20 can be substantially identical to the set voltage Vbset
determined in advance as a common value between different plasma
treatment apparatuses. As a result, processing can be performed
with an etching rate based on a user's request, that is, with an
etching rate corresponding to the set power Pbset and the set
voltage (target value) Vbset, thereby improving the processing
precision of each plasma treatment apparatus. Simultaneously, both
the bias-side voltage and the bias-side power can be substantially
equalized between different plasma treatment apparatuses, thereby
reducing a variation in the processing dimension or etching amount
between different plasma treatment apparatuses.
[0057] Alternatively, a case, as a comparative example, where the
probe 63 senses power (for example, power on a node N2) output from
the power supply circuit 40, not the voltage output from the power
supply circuit 20, is taken into consideration. In this case, the
feedback control circuit 64 controls power supplied from the power
supply circuit 40 so that power (power for plasma generation)
sensed by the probe 63 is substantially identical to a
predetermined target value. At this time, the assembling state or
characteristic of a part (the antenna coil 31, the dielectric wall
32, or the like) in the plasma generating unit 30 varies between
different plasma treatment apparatuses. For this reason, even when
power (power for plasma generation) output from the power supply
circuit 40 can be substantially equalized between a plurality of
different plasma treatment apparatuses of the same model, the
density of plasma generated inside the treatment chamber 50 tends
to vary between a plurality of different plasma treatment
apparatuses of the same model. Accordingly, since processing is
performed with an etching rate deviated from a user's request, the
processing precision of each plasma treatment apparatus tends to be
degraded. Simultaneously, it becomes difficult to reduce a
variation in the processing dimension or etching amount between
different plasma treatment apparatuses.
[0058] In contrast, in the first embodiment, the probe 63 senses
the voltage output from the power supply circuit 20. Thus, the
feedback control circuit 64 can control power supplied from the
power supply circuit 40 so that the voltage Vb sensed by the probe
63 is substantially identical to the set voltage Vbset. As a
result, processing can be performed with an etching rate based on a
user's request, thereby improving the processing precision of each
plasma treatment apparatus. Simultaneously, it is possible to
reduce a variation in the processing dimension or etching amount
between different plasma treatment apparatuses.
[0059] In the first embodiment, when the voltage Vb sensed by the
probe 63 is higher than the set voltage Vbset, the feedback control
circuit 64 controls the radio-frequency power supply 42 in the
power supply circuit 40 to increase power to be generated. Thus,
(as a result of the control operation of the feedback control unit
22c), if power output from the power supply circuit 20 is
substantially identical to the set power Pbset, power supplied from
the power supply circuit 40 to the plasma generating unit 30
increases so as to increase the density of plasma to be generated
inside the treatment chamber 50 and to put the ion current (the
density of ions to be accelerated) close to or substantially equal
to a target value. Alternatively, when the voltage Vb sensed by the
probe 63 is lower than the set voltage Vbset, the feedback control
circuit 64 controls the radio-frequency power supply 42 in the
power supply circuit 40 to decrease power to be generated. Thus,
(as a result of the control operation of the feedback control unit
22c), if power output from the power supply circuit 20 is
substantially identical to the set power Pbset, power supplied from
the power supply circuit 40 to the plasma generating unit 30
decreases so as to decrease the density of plasma to be generated
inside the treatment chamber 50 and to put the ion current (the
density of ions to be accelerated) close to or substantially equal
to a target value. That is, while a voltage for accelerating ions
inside the treatment chamber 50 is substantially identical to a
target value, the density of ions to be accelerated inside the
treatment chamber 50 can be substantially identical to a target
value.
[0060] It should be noted that the control operation of the
feedback control unit 22c or the control operation of the feedback
control circuit 64 may be performed at the time of initial setting
before processing (etching) is performed, may be performed during
processing (etching) in addition to the initial setting, may be
continuously performed for a time from the initial setting, or may
be constantly performed from the initial setting. In this case, it
is possible to reduce a time-dependent variation in the processing
dimension or etching amount between different plasma treatment
apparatuses occurred according to time from the initial
setting.
[0061] The radio-frequency power supply 22 may further have an
input unit 22d. At this time, the set power Pbset may be input to
the input unit 22d in the radio-frequency power supply 22, not the
input unit 65 in the control device 60. In this case, the input
unit 22d in the radio-frequency power supply 22 supplies the value
of the set power Pbset to the feedback control unit 22c, and the
feedback control unit 22c receives the value of the set power Pbset
from the input unit 22d and holds the value of the set power Pbset
as a target value.
[0062] The control operation of the feedback control unit 22c or
the control operation of the feedback control circuit 64 may be at
least partially realized by software, instead of being realized by
hardware (circuit).
Second Embodiment
[0063] Next, a plasma treatment apparatus 1 according to a second
embodiment will be described. Hereinafter, description will be
provided focusing on differences from the first embodiment.
[0064] In the control device 60 of the plasma treatment apparatus 1
according to the second embodiment, a user inputs set power Pbset
and a set current Ibset to the input unit 65. Alternatively, the
input unit 65 receives the set power Pbset and the set current
Ibset from a host computer or another plasma treatment apparatus
through a communication line. The set power Pbset and the set
current Ibset are respectively determined in advance as a common
value between different plasma treatment apparatuses.
[0065] The input unit 65 supplies the value of the set power Pbset
to the feedback control unit 22c in the power supply circuit 20,
and supplies the value of the set current Ibset to the feedback
control circuit 64.
[0066] The sensing unit 22b in the power supply circuit 20 senses
power Pb generated by the generating unit 22a. The sensing unit 22b
supplies the value of the sensed power Pb to the feedback control
unit 22c.
[0067] The feedback control unit 22c receives the value of the set
power Pbset from the input unit 65 and holds the value of the set
power Pbset as a target value. If the value of the sensed power Pb
is received from the sensing unit 22b, the feedback control unit
22c compares the power Pb with the set power Pbset, and controls
power generated by the generating unit 22a so that the power Pb
sensed by the sensing unit 22b is substantially identical to the
set power Pbset.
[0068] The probe 63 senses a current (parameter) Ib output from the
power supply circuit 20. For example, the probe 63 senses a current
flowing in the node N1 between the electrode 10 and the power
supply circuit 20 (for example, a current in which the direction
from the power supply circuit 20 to the electrode 10 is positive)
as the current Ib output from the power supply circuit 20. The
probe 63 supplies the value of the sensed current Ib to the
feedback control circuit 64.
[0069] The feedback control circuit 64 receives the value of the
set current Ibset from the input unit 65 and holds the value of the
set current Ibset as a target value. If the value of the sensed
current Ib is received from the probe 63, the feedback control
circuit 64 compares the current Ib with the set current Ibset, and
controls power supplied from the power supply circuit 40 so that
the current Ib sensed by the probe 63 becomes close to or
substantially equal to the set current Ibset. Specifically, when
the sensed current Ib is greater than the set current Ibset, the
feedback control circuit 64 controls the radio-frequency power
supply 42 in the power supply circuit 40 to decrease power to be
generated. When the sensed current Ib is smaller than the set
current Ibset, the feedback control circuit 64 controls the
radio-frequency power supply 42 in the power supply circuit 40 to
increase power to be generated.
[0070] In the plasma treatment apparatus 1 according to the second
embodiment, as shown in FIG. 3, the operation of the control device
60 is different from the first embodiment.
[0071] In Step S22, the probe 63 senses the current (parameter) Ib
output from the power supply circuit 20. For example, the probe 63
senses the current flowing in the node N1 between the electrode 10
and the power supply circuit 20 as the current Ib output from the
power supply circuit 20. The probe 63 supplies the value of the
sensed current (bias-side current) Ib to the feedback control
circuit 64.
[0072] In Step S23, the feedback control circuit 64 receives the
value of the set current Ibset from the input unit 65 and holds the
value of the set current Ibset as a target value. If the value of
the sensed current Ib is received from the probe 63, the feedback
control circuit 64 compares the current (bias-side current) Ib with
the set current (target value) Ibset. When the sensed current Ib is
smaller than the set current Ibset, the feedback control circuit 64
progresses the process to Step S24. When the sensed current Ib is
greater than the set current Ibset, the process progresses to Step
S25. When the sensed current Ib is substantially identical to the
set current Ibset, the process ends.
[0073] In Step S24, the feedback control circuit 64 controls the
radio-frequency power supply 42 in the power supply circuit 40 to
increase power to be generated.
[0074] In Step S25, the feedback control circuit 64 controls the
radio-frequency power supply 42 in the power supply circuit 40 to
decrease power to be generated.
[0075] In this way, the processing of Steps S22 to S25 (the
operation of the probe 63 to sense the current Ib output from the
power supply circuit 20 and the control operation of the feedback
control circuit 64) is repeatedly performed until the bias-side
current Ib is substantially identical to the set current (target
value) Ibset. Though not shown, the operation of the sensing unit
22b to sense the power Pb generated by the generating unit 22a in
the power supply circuit 20 and the control operation of the
feedback control unit 22c are performed in parallel with the
processing of Steps S22 to S25.
[0076] As described above, in the second embodiment, when the
current Ib sensed by the probe 63 is greater than the set current
Ibset, the feedback control circuit 64 controls the radio-frequency
power supply 42 in the power supply circuit 40 to decrease power to
be generated. Thus, power supplied from the power supply circuit 40
to the plasma generating unit 30 decreases so as to decrease the
density of plasma to be generated inside the treatment chamber 50
and to put the ion current (the density of ions to be accelerated)
close to or substantially equal to a target value. Alternatively,
when the current Ib sensed by the probe 63 is smaller than the set
current Ibset, the feedback control circuit 64 controls the
radio-frequency power supply 42 in the power supply circuit 40 to
increase power to be generated. Thus, power supplied from the power
supply circuit 40 to the plasma generating unit 30 increases so as
to increase the density of plasma to be generated inside the
treatment chamber 50 and to put the ion current (the density of
ions to be accelerated) close to or substantially equal to a target
value. That is, in the second embodiment, while power for
accelerating ions inside the treatment chamber 50 is substantially
identical to a target value, the density of ions to be accelerated
inside the treatment chamber 50 can be substantially identical to a
target value.
[0077] It should be noted that, although in the first and second
embodiments, a case has been described where a plasma treatment
apparatus is an inductive coupling plasma (ICP) RIE apparatus, a
plasma treatment apparatus is not limited to the ICP RIE apparatus.
For example, a plasma treatment apparatus may be an electron
cycrotron resonance (ECR) RIE apparatus or a two-frequency parallel
flat plate (capacitive coupling) RIE apparatus. When the plasma
treatment apparatus 100 is a two-frequency parallel flat plate
(capacitive coupling) RIE apparatus, as shown in FIG. 4, a plasma
generating unit 130 has an upper electrode 131 which is arranged to
face the electrode 10 inside the treatment chamber 50, instead of
the antenna coil 31 and the dielectric wall 32.
[0078] Alternatively, a plasma treatment apparatus may be an
apparatus which has a three or more-frequency power supply (a
radio-frequency power supply having three or more different
frequencies). In this case, a parameter output from a
low-frequency-side power supply circuit may be sensed, and power
supplied from a power supply circuit having a higher frequency than
the low-frequency-side power supply circuit in the three or
more-frequency power supply may be controlled so that the sensed
parameter is substantially identical to a predetermined target
value.
Third Embodiment
[0079] A plasma treatment apparatus 200 according to a third
embodiment will be described with reference to FIG. 7. FIG. 7 is a
diagram showing the schematic configuration of the plasma treatment
apparatus 200 according to the third embodiment. Hereinafter,
description will be provided focusing on differences from the first
embodiment.
[0080] The plasma treatment apparatus 200 includes a power supply
circuit 220, a plasma generating unit 280, and a detecting unit
290.
[0081] The power supply circuit 220 generates radio-frequency power
and supplies the radio-frequency power to the electrode 10. The
radio-frequency power is power which is used to accelerate ions
(for example, F.sup.+, CF3.sup.+, or the like) generated from a
treatment gas along with radicals when plasma PL is generated
inside the treatment chamber 50 toward the electrode 10 (the
substrate WF to be treated). The frequency of the radio-frequency
power is, for example, 13.56 MHz. The internal configuration of the
power supply circuit 220 will be described below.
[0082] The plasma generating unit 280 generates the plasma PL in
the space 51 separated from the electrode 10 inside the treatment
chamber 50. Specifically, the plasma generating unit 280 has a
radio-frequency power supply 281, a matching box 284, an antenna
coil 282, and a dielectric wall 283. The radio-frequency power
supply 281 generates radio-frequency power and supplies the
radio-frequency power to the antenna coil 282. The matching box 284
has, for example, a variable capacitor and a variable coil. The
matching box 284 performs impedance adjustment (impedance matching)
using the variable capacitor and the variable coil so that
impedance on the radio-frequency power supply 281 side with respect
to the matching box 284 matches with impedance on the antenna coil
282 side with respect to the matching box 284. The antenna coil 282
generates electromagnetic waves (high-frequency magnetic field)
using the supplied radio-frequency power in a state where impedance
matching is performed. The electromagnetic waves generated by the
antenna coil 282 pass through the dielectric wall 283 and are
introduced into the space 51 of the treatment chamber 50. In the
space 51 of the treatment chamber 50, the treatment gas is
discharged to generate the plasma PL, and ions (for example,
F.sup.+, CF3.sup.+, or the like) are generated from the treatment
gas along with radicals. The dielectric wall 283 also serves as the
upper wall of the treatment container.
[0083] The detecting unit 290 detects a bias voltage Vb as a
difference between a potential Vp1 of the plasma PL generated by
the plasma generating unit 280 and a potential Ve of the electrode
10, to which power is supplied from the power supply circuit
220.
[0084] Specifically, the detecting unit 290 has a detection
terminal 291 which extends to the space 51 of the treatment chamber
50, and a detection terminal 292 which is electrically connected to
the electrode 10. The detecting unit 290 detects the potential Vp1
of the plasma PL through the detection terminal 291, and detects
the potential Ve of the electrode 10 through the detection terminal
292. The detecting unit 290 obtains the bias voltage Vb, for
example, by the following expression.
Vb=Vp1-Ve
[0085] The detecting unit 290 supplies the bias voltage Vb detected
in the above-described manner to the power supply circuit 220.
[0086] Next, the internal configuration of the power supply circuit
220 will be described with reference to FIG. 7.
[0087] The power supply circuit 220 has a main unit 240 and a
correcting unit 230. The main unit 240 generates power to be
supplied to the electrode 10. Specifically, the main unit 240 has a
radio-frequency power supply 243, a matching box 242, and a
blocking capacitor 241. The radio-frequency power supply 243
generates radio-frequency power. The matching box 242 has, for
example, a variable capacitor and a variable coil. The matching box
242 performs impedance adjustment (impedance matching) using the
variable capacitor and the variable coil so that impedance on the
radio-frequency power supply 243 side with respect to the matching
box 242 matches with impedance on the blocking capacitor 241 side
with respect to the matching box 242.
[0088] The blocking capacitor 241 supplies a high-frequency
component of the radio-frequency power supplied from the
radio-frequency power supply 243 to the electrode 10 in a state
where impedance matching is performed. Thus, the electrode 10 is
negatively charged in a state where the plasma PL is positively
charged, and ions (for example, F.sup.+, CF3.sup.+, or the like)
are accelerated toward the electrode 10 (toward the substrate WF to
be treated) by the potential difference of both of them, that is,
the bias voltage Vb.
[0089] The correcting unit 230 receives a signal representing the
bias voltage Vb detected by the detecting unit 290 from the
detecting unit 290. The correcting unit 230 compensates for the
capacitance of the main unit 240 to correct the capacitance value
of the power supply circuit 220 so that the bias voltage Vb
represented by the signal becomes close to or substantially equal
to a target value Vt. The target value Vt is a value which is set
in advance in accordance with a predetermined processing condition
(gas type, gas pressure, or the like) for an object to be treated
and is a common value between plasma treatment apparatuses. A
feedback operation which includes the operation of the detecting
unit 290 to detect the bias voltage Vb and the operation of the
correcting unit 230 to correct the capacitance value of the power
supply circuit 220 is repeatedly performed, so that the bias
voltage Vb is adjusted to be substantially identical to the target
value Vt. Thus, the plasma treatment apparatus 200 processes (for
example, etches) the substrate WF to be treated in a state where
the bias voltage Vb detected by the detecting unit 290 is
substantially identical to the target value Vt.
[0090] Next, the internal configuration of the correcting unit 230
will be described with reference to FIG. 8. FIG. 8 is a diagram
showing the internal configuration of the correcting unit 230.
[0091] The correcting unit 230 has a variable-capacitance unit 235,
a comparing unit 233, and a changing unit 234.
[0092] The variable-capacitance unit 235 is configured to change
the capacitance value thereof in accordance with a received control
signal. The comparing unit 233 receives a signal representing the
bias voltage Vb detected by the detecting unit 290 from the
detecting unit 290. In the comparing unit 233, the target value Vt
is set in advance. The comparing unit 233 compares the bias voltage
Vb represented by the signal received from the detecting unit 290
with the target value Vt, and supplies the comparison result to the
changing unit 234. The changing unit 234 changes the capacitance
value of the variable-capacitance unit 235 in accordance with the
supplied comparison result.
[0093] Specifically, the variable-capacitance unit 235 has a
variable-capacitance element (first variable-capacitance element)
231 and a variable-capacitance element (second variable-capacitance
element) 232. The variable-capacitance element 231 is connected in
series between the electrode 10 and the main unit 240. For example,
the variable-capacitance element 231 is configured such that an
electrode 231a thereof is electrically connected to the electrode
10, and an electrode 231b thereof is electrically connected to the
main unit 240. The variable-capacitance element 232 is connected in
parallel with the variable-capacitance element 231 between the main
unit 240 and the electrode 10. For example, the
variable-capacitance element 232 is configured such that an
electrode 232a thereof is electrically connected to the electrode
10 and the electrode 231a, and an electrode 232b thereof is
connected to the ground voltage. Since one end of the main unit 240
is connected to the ground voltage, the variable-capacitance
element 232 is equivalently connected in parallel with the main
unit 240 with respect to the electrode 10.
[0094] When the comparison result of the comparing unit 233 shows
that the bias voltage Vb represented by the signal is higher than
the target value Vt, the changing unit 234 performs at least an
operation to increase the capacitance value of the
variable-capacitance element 232. Thus, since the capacitance value
of the variable-capacitance element 232 connected in parallel with
the main unit 240 increases, the bias voltage Vb decreases. That
is, the capacitance value of the power supply circuit 220 is
corrected so that the bias voltage Vb becomes close to or
substantially equal to the target value Vt. The changing unit 234
may further perform an operation to decrease the capacitance value
of the variable-capacitance element 231.
[0095] When the comparison result of the comparing unit 233 shows
that the bias voltage Vb represented by the signal is lower than
the target value Vt, the changing unit 234 performs at least an
operation to increase the capacitance value of the
variable-capacitance element 231. Thus, since the capacitance value
of the variable-capacitance element 231 connected in series with
the main unit 240 increases, the bias voltage Vb increases. That
is, the capacitance value of the power supply circuit 220 is
corrected so that the bias voltage Vb becomes close to or
substantially equal to the target value Vt. The changing unit 234
may further perform an operation to decrease the capacitance value
of the variable-capacitance element 232.
[0096] In this way, the changing unit 234 changes at least one of
the capacitance value of the variable-capacitance element 231 and
the capacitance value of the variable-capacitance element 232 in
accordance with the comparison result of the comparing unit 233 so
that the bias voltage Vb detected by the detecting unit 290 becomes
close to or substantially equal to the target value Vt.
[0097] Next, a method of manufacturing a semiconductor device using
the plasma treatment apparatus 200 according to the third
embodiment will be described with reference to FIG. 9. FIG. 9 is a
flowchart showing a method of manufacturing a semiconductor device
using the plasma treatment apparatus 200.
[0098] In Step S31, the substrate WF to be treated (for example, a
semiconductor substrate) is placed on the electrode 10 inside the
treatment chamber 50.
[0099] In Step S32, the power supply circuit 220 generates
radio-frequency power and supplies the radio-frequency power to the
electrode 10. Along with this, the plasma generating unit 280
generates the plasma PL in the space 51 separated from the
electrode 10 inside the treatment chamber 50. Specifically, the
radio-frequency power supply 281 generates radio-frequency power
and supplies the radio-frequency power to the antenna coil 282. The
antenna coil 282 generates electromagnetic waves (high-frequency
magnetic field) using the supplied radio-frequency power. The
electromagnetic waves generated by the antenna coil 282 pass
through the dielectric wall 283 and are introduced into the space
51 of the treatment chamber 50. In the space 51 of the treatment
chamber 50, the treatment gas is discharged to generate the plasma
PL, and ions (for example, F.sup.+, CF3.sup.+, or the like) are
generated from the treatment gas along with radicals.
[0100] In Step S33, the detecting unit 290 detects the bias voltage
Vb as the difference between the potential Vp1 of the plasma PL
generated by the plasma generating unit 280 and the potential Ve of
the electrode 10, to which power is supplied from the power supply
circuit 220.
[0101] Specifically, the detecting unit 290 detects the potential
Vp1 of plasma PL through the detection terminal 291, and detects
the potential Ve of the electrode 10 through the detection terminal
292. The detecting unit 290 obtains the bias voltage Vb, for
example, by the following expression.
Vb=Vp1-Ve
[0102] The detecting unit 290 supplies the bias voltage Vb detected
in the above-described manner to the power supply circuit 220.
[0103] In Step S34, the comparing unit 233 of the power supply
circuit 220 receives the signal representing the bias voltage Vb
detected by the detecting unit 290 from the detecting unit 290. In
the comparing unit 233, the target value Vt is set in advance. The
comparing unit 233 compares the bias voltage Vb represented by the
signal received from the detecting unit 290 with the target value
Vt, and supplies the comparison result to the changing unit 234.
The changing unit 234 determines whether or not the bias voltage Vb
detected by the detecting unit 290 is substantially identical to
the target value Vt in accordance with the supplied comparison
result. For example, if a difference between the bias voltage Vb
and the target value Vt is out of a predetermined allowable range,
the changing unit 234 determines that the bias voltage Vb is not
substantially identical to the target value Vt. If the difference
between the bias voltage Vb and the target value Vt falls within a
predetermined allowable range, the changing unit 234 determines
that the bias voltage Vb is substantially identical to the target
value Vt. When the bias voltage Vb is not substantially identical
to the target value Vt (`No` in Step S34), the changing unit 234
progresses the process to Step S35. When the bias voltage Vb is
substantially identical to the target value Vt (`Yes` in Step S34),
the process progresses to Step S36.
[0104] In Step S35, the changing unit 234 of the power supply
circuit 220 changes at least one of the capacitance value of the
variable-capacitance element 231 and the capacitance value of the
variable-capacitance element 232 in accordance with the supplied
comparison result so that the bias voltage Vb detected by the
detecting unit 290 becomes close to or substantially equal to the
target value Vt.
[0105] That is, when the comparison result of the comparing unit
233 shows that the bias voltage Vb represented by the signal is
higher than the target value Vt, the changing unit 234 performs at
least an operation to increase the capacitance value of the
variable-capacitance element 232. Thus, since the capacitance value
of the variable-capacitance element 232 connected in parallel with
the main unit 240 increases, the bias voltage Vb decreases. That
is, the capacitance value of the power supply circuit 220 is
corrected so that the bias voltage Vb becomes close to or
substantially equal to the target value Vt. The changing unit 234
may further perform an operation to decrease the capacitance value
of the variable-capacitance element 231.
[0106] When the comparison result of the comparing unit 233 shows
that the bias voltage Vb represented by the signal is lower than
the target value Vt, the changing unit 234 performs at least an
operation to increase the capacitance value of the
variable-capacitance element 231. Thus, since the capacitance value
of the variable-capacitance element 231 connected in series with
the main unit 240 increases, the bias voltage Vb increases. That
is, the capacitance value of the power supply circuit 220 is
corrected so that the bias voltage Vb becomes close to or
substantially equal to the target value Vt. The changing unit 234
may further perform an operation to decrease the capacitance value
of the variable-capacitance element 232.
[0107] In this way, the processing of Steps S33 to S35 is
repeatedly performed until the bias voltage Vb is substantially
identical to the target value Vt. The impedance matching by the
matching box 242 may be performed each time the correction
processing of Step S35 is performed.
[0108] In Step S36, the changing unit 234 supplies a signal
representing the bias voltage Vb being substantially identical to
the target value Vt to a controller (not shown). Accordingly, the
controller is switched from the condition for a correction
operation to the condition for a processing operation and controls
the plasma generating unit 280. Therefore, the plasma treatment
apparatus 200 processes (for example, etches) the substrate WF to
be treated in a state where the bias voltage Vb detected by the
detecting unit 290 is substantially identical to the target value
Vt.
[0109] Herein, there is taken into consideration a case, as a
comparative example, where Steps S33 to S35 in the method of
manufacturing a semiconductor device using the plasma treatment
apparatus 200 are not performed. In this case, parasitic
capacitance in the power supply circuit 220 varies between a
plurality of different plasma treatment apparatuses of the same
model. For this reason, the bias voltage Vb as the difference
between the potential Vp1 of the plasma PL generated by the plasma
generating unit 280 and the potential Ve of the electrode 10, to
which power is supplied from the power supply circuit 220, tends to
vary between different plasma treatment apparatuses. For example,
FIG. 20 shows the evaluation result of the bias voltage Vb for a
plurality of different plasma treatment apparatuses in a state
where the processing of Steps S33 to S35 is not performed after
Steps S31 and S32 are performed. From FIG. 20, it can be understood
that the bias voltage Vb significantly varies between different
plasma treatment apparatuses.
[0110] In contrast, in the third embodiment, Steps S33 to S35 are
repeatedly performed after Steps S31 and S32 are performed. That
is, the processing is repeatedly performed for detecting the bias
voltage Vb (Step S33), and when the detected bias voltage Vb is not
substantially identical to the target value Vt (`No` in Step S34),
for correcting the capacitance value of the power supply circuit
220 so that the detected bias voltage Vb is substantially identical
to the target value Vt (Step S35). Thus, when the detected bias
voltage Vb is substantially identical to the target value Vt (`Yes`
in Step S34), the plasma treatment apparatus 200 processes the
substrate WF to be treated in a state where the bias voltage Vb
detected by the detecting unit 290 is substantially identical to
the target value Vt (a common value between different plasma
treatment apparatuses) (Step S36). As a result, processing can be
performed in a state where the bias voltage Vb is substantially
equalized to the target value Vt which is common to different
plasma treatment apparatuses, thereby reducing a variation in the
processing dimension between different plasma treatment
apparatuses.
[0111] In particular, the correcting unit 230 of the power supply
circuit 220 has the variable-capacitance element 231 which is
connected in series with the main unit 240 with respect to the
electrode 10, and the variable-capacitance element 232 which is
connected in parallel with the main unit 240 with respect to the
electrode 10. Thus, in Step S35, when the bias voltage Vb is higher
or lower than the target value Vt, the capacitance value of the
power supply circuit 220 can be corrected so that the bias voltage
Vb becomes close to or substantially equal to the target value
[0112] Vt.
[0113] Alternatively, a case, as a comparative example, where the
power supply circuit 220 has no correcting unit 230 is taken into
consideration. In this case, as described above, parasitic
capacitance in the power supply circuit 220 varies between
different plasma treatment apparatuses. For this reason, the bias
voltage Vb tends to vary between different plasma treatment
apparatuses.
[0114] In contrast, in the third embodiment, the power supply
circuit 220 has the correcting unit 230. The correcting unit 230
compensates for the capacitance value of the main unit 240 to
correct the capacitance value of the power supply circuit 220 so
that the bias voltage Vb detected by the detecting unit 290 is
substantially identical to the target value Vt (the common value
between different plasma treatment apparatuses). Therefore, the
plasma treatment apparatus 200 can perform processing in a state
where the bias voltage Vb is substantially identical to the target
value Vt, thereby reducing a variation in the processing dimension
between different plasma treatment apparatuses.
[0115] Alternatively, a case, as a comparative example, where the
plasma treatment apparatus 200 has no detecting unit 290 is taken
into consideration. In this case, the correcting unit 230 cannot
recognize the value of the bias voltage Vb, making it difficult to
perform correction so that the bias voltage Vb is substantially
identical to the target value Vt. Accordingly, it becomes difficult
to reduce a variation in the processing dimension between different
plasma treatment apparatuses.
[0116] Alternatively, a case, as a comparative example, where the
plasma treatment apparatus 200 has no detecting unit 290, and has a
second detecting unit which detects the capacitance value of the
main unit 240 is taken into consideration. In this case, in the
plasma treatment apparatus 200, since there are many parameters
which should be controlled, the correlation between the capacitance
value of the main unit 240 and the bias voltage Vb tends to vary
between different plasma treatment apparatuses. For this reason,
even when the capacitance value of the main unit 240 detected by
the second detecting unit is received, the correcting unit 230
cannot recognize the value of the bias voltage Vb, making it
difficult to perform correction so that the bias voltage Vb is
substantially identical to the target value Vt. Accordingly, it
becomes difficult to reduce a variation in the processing dimension
between different plasma treatment apparatuses.
[0117] Alternatively, a case, as a comparative example, where the
plasma treatment apparatus 200 has no detecting unit 290, and has a
third detecting unit which detects the reactance value of the
correcting unit 230 is taken into consideration. In this case, in
the plasma treatment apparatus 200, since there are many parameters
which should be controlled, the correlation between the reactance
value of the correcting unit 230 and the bias voltage Vb tends to
vary between different plasma treatment apparatuses. For this
reason, even when the reactance value of the correcting unit 230
detected by the third detecting unit is received, the correcting
unit 230 cannot recognize the value of the bias voltage Vb, making
it difficult to perform correction so that the bias voltage Vb is
substantially identical to the target value Vt. Accordingly, it
becomes difficult to reduce a variation in the processing dimension
between different plasma treatment apparatuses.
[0118] In contrast, in the third embodiment, the plasma treatment
apparatus 200 includes the detecting unit 290. The detecting unit
290 detects the bias voltage Vb. Thus, the correcting unit 230 can
recognize the value of the bias voltage Vb, making it possible to
perform correction so that the bias voltage Vb is substantially
identical to the target value Vt. As a result, it is possible to
reduce a variation in the processing dimension between different
plasma treatment apparatuses.
[0119] In particular, the detecting unit 290 has the detection
terminal 291 which extends to the space 51 of the treatment chamber
50, and the detection terminal 292 which is electrically connected
to the electrode 10. Thus, the detecting unit 290 obtains the
difference between the voltage detected by the detection terminal
291 and the voltage detected by the detection terminal 292, thereby
detecting the bias voltage Vb between the potential of the plasma
PL generated in the space 51 by the plasma generating unit 280 and
the potential of the electrode 10, to which power is supplied, with
satisfactory precision.
[0120] Alternatively, a case, as a comparative example, is
considered where the plasma treatment apparatus 200 has no
detecting unit 290, and a predetermined measurement tool is
attached to the plasma treatment apparatus 200 at the time of
maintenance to detect the bias voltage Vb. In this case, if the
manufacturing of a semiconductor device using the plasma treatment
apparatus 200 is not temporarily interrupted, the correcting unit
230 cannot perform correction so that the bias voltage Vb is
substantially identical to the target value Vt. Accordingly,
throughput in the method of manufacturing a semiconductor device
tends to be degraded.
[0121] In contrast, in the third embodiment, the plasma treatment
apparatus 200 includes the detecting unit 290. The detecting unit
290 detects the bias voltage Vb. Thus, the correcting unit 230 can
perform correction so that the bias voltage Vb is substantially
identical to the target value Vt, without interrupting the
manufacturing a semiconductor device using the plasma treatment
apparatus 200 (as inline processing). As a result, it is possible
to suppress degradation in throughput in the method of
manufacturing a semiconductor device.
[0122] It should be noted that, although in the third embodiment, a
case has been described where the plasma treatment apparatus 200 is
an inductive coupling plasma (ICP) RIE apparatus, the plasma
treatment apparatus 200 is not limited to the ICP RIE apparatus.
For example, the plasma treatment apparatus 200 may be an electron
cycrotron resonance (ECR) RIE apparatus or a parallel flat plate
RIE apparatus. When the plasma treatment apparatus 200 is a
parallel flat plate RIE apparatus, the plasma generating unit 280
has an upper electrode which is arranged to face the electrode 10
inside the treatment chamber 50, instead of the antenna coil 282
and the dielectric wall 283.
Fourth Embodiment
[0123] Next, a plasma treatment apparatus 300 according to a fourth
embodiment will be described with reference to FIGS. 10 and 11.
FIG. 10 is a diagram showing the schematic configuration of the
plasma treatment apparatus 300 according to the fourth embodiment.
FIG. 11 is a diagram showing the internal configuration of a
correcting unit 330.
[0124] Hereinafter, description will be provided focusing on
differences from the third embodiment.
[0125] The plasma treatment apparatus 300 includes a power supply
circuit 320, a plasma generating unit 280, a detecting unit 290,
and a controller 360. The controller 360 manages a processing
condition which is used in controlling the plasma generating unit
280. The power supply circuit 320 has the correcting unit 330. The
correcting unit 330 receives a signal representing the processing
condition from the controller 360.
[0126] Specifically, as shown in FIG. 11, the correcting unit 330
has a variable-capacitance unit 235, a storage unit 336, a
determining unit 337, a comparing unit 333, and a changing unit
234.
[0127] The storage unit 336 stores a plurality of target values
associated with the processing condition. The processing condition
includes, for example, the type of a treatment gas which should be
supplied to the treatment chamber 50 by the plasma generating unit
280. The storage unit 336 stores, for example, target value
information shown in FIG. 12. The target value information includes
a treatment gas column 3361 and a target value column 3362. The
treatment gas column 3361 stores information regarding the type of
a treatment gas, for example, "treatment gas A," "treatment gas B,"
. . . . The target value column 3362 stores information regarding a
target value, for example, "Vta," "Vtb," . . . . By referring to
the target value information, a target value corresponding to the
type of a treatment gas can be specified. For example, by referring
to the target value information, the target value corresponding to
"treatment gas A" can be specified as "Vta," and the target value
corresponding to "treatment gas B" can be specified as "Vtb." When
a plurality of plasma treatment apparatuses 300 are activated under
the same processing condition, the target value information stored
in the storage unit 336 can be commonly used, and the storage unit
336 itself can be shared between the apparatuses.
[0128] The determining unit 337 receives a signal representing a
processing condition from the controller 360. When the signal
representing the processing condition is received, the determining
unit 337 determines a target value corresponding to the processing
condition represented by the signal by referring to the target
value information stored in the storage unit 336. The determining
unit 337 supplies the determined target value to the comparing unit
333.
[0129] The comparing unit 333 preferentially uses the target value
supplied from the determining unit 337 over the target value Vt set
in advance. That is, the comparing unit 333 compares the bias
voltage Vb detected by the detecting unit 290 and the target value
determined by the determining unit 337.
[0130] As shown in FIG. 13, a method of manufacturing a
semiconductor device using the plasma treatment apparatus 300 is
different from the third embodiment in the following respect.
[0131] In Step S41, the determining unit 337 determines whether or
not the processing condition by the plasma treatment apparatus 300
is changed. For example, the determining unit 337 holds the signal
representing the processing condition received from the controller
360, and when a signal representing a different processing
condition is received, determines that the processing condition is
changed. When a signal representing the same processing condition
is received or when a signal representing a processing condition is
not received, it is determined that the processing condition is not
changed. When the processing condition is changed (`Yes` in Step
S41), the determining unit 337 progresses the process to Step S42.
When the processing condition is not changed (`No` in Step S41),
the process ends.
[0132] In Step (determining step) S42, the determining unit 337
determines a target value corresponding to the processing condition
represented by the signal by referring to the target value
information stored in the storage unit 336. The determining unit
337 supplies the determined target value to the comparing unit 333.
The comparing unit 333 changes the target value, which is used for
comparison, to the target value supplied from the determining unit
337.
[0133] Then, in Step S35, at least one of the capacitance value of
the variable-capacitance element 231 and the capacitance value of
the variable-capacitance element 232 is changed in accordance with
the comparison result in Step S34 so that the bias voltage Vb
detected in Step S33 is substantially identical to the target value
determined in Step S42. In Step S36, the controller 360 controls
the plasma generating unit 280 under the processing condition being
managed.
[0134] In this way, in the fourth embodiment, a target value is
changed for each processing condition (for example, the type of a
treatment gas). For this reason, the correcting unit 330 can
perform correction so that the bias voltage Vb is substantially
identical to a target value adjusted to the processing condition.
As a result, it is possible to reduce a variation in the processing
dimension between different plasma treatment apparatus under each
processing condition.
Fifth Embodiment
[0135] Next, a plasma treatment apparatus 400 according to a fifth
embodiment will be described with reference to FIG. 14. FIG. 14 is
a diagram showing the internal configuration of a correcting unit
430 in the plasma treatment apparatus 400. Hereinafter, description
will be provided focusing on differences from the third
embodiment.
[0136] In the plasma treatment apparatus 400, the correcting unit
430 of a power supply circuit 420 further has a storage unit 436, a
determining unit 437, and a timer 438.
[0137] The storage unit 436 stores a plurality of target values
associated with intervals to which the elapsed time of plasma
treatment belongs. The elapsed time refers to, for example, an
elapsed time after a cleaning process inside the treatment chamber
50 is performed immediately before. The storage unit 436 stores,
for example, target value information shown in FIG. 15. The target
value information includes an elapsed time column 4361 and a target
value column 4362. The elapsed time column 4361 stores information
regarding an interval to which an elapsed time belongs, for
example, "0 to T1," "T1 to T2," . . . . The target value column
4362 stores information regarding a target value, for example,
"Vt1," "Vt2," . . .. By referring to the target value information,
a target value corresponding to an interval to which the elapsed
time belongs can be specified. For example, by referring to the
target value information, the target value corresponding to "0 to
T1" can be specified as "Vt1," and the target value corresponding
to "T1 to T2" can be specified as "Vt2."
[0138] The determining unit 437 receives a signal representing
cleaning inside the treatment chamber 50 being completed from the
controller 360. When the signal representing the cleaning inside
the treatment chamber 50 being completed is received, the
determining unit 437 activates the timer 438. Thus, the timer 438
starts to count the elapsed time.
[0139] The determining unit 437 accesses the timer 438 to acquire
information of the elapsed time from the timer 438. The determining
unit 437 determines a target value corresponding to an interval to
which the elapsed time belongs by referring to the target value
information stored in the storage unit 436. The determining unit
437 supplies the determined target value to the comparing unit
333.
[0140] As shown in FIG. 16, a method of manufacturing a
semiconductor device using the plasma treatment apparatus 400 is
different from the third embodiment in the following respect.
[0141] In Step S51, the determining unit 437 determines whether or
not the interval to which the elapsed time belongs is changed. For
example, the determining unit 337 accesses the timer 438 to acquire
information of the elapsed time from the timer 438. The determining
unit 437 holds the signal representing the interval of the elapsed
time corresponding to the target value used immediately before.
When the elapsed time acquired from the timer 438 does not belong
to the interval of the held elapsed time, the determining unit 437
determines that the interval to which the elapsed time belongs is
changed. When the elapsed time acquired from the timer 438 belongs
to the interval of the held elapsed time, it is determined that the
interval to which the elapsed time belongs is not changed. When the
interval to which the elapsed time belongs is changed (`Yes` in
Step S51), the determining unit 437 progresses the process to Step
S52. When the interval to which the elapsed time belongs is not
changed (`No` in Step S51), the process progresses to Step S32.
[0142] In Step S52, the determining unit 437 determines a target
value corresponding to the interval to which the elapsed time
belongs by referring to the target value information stored in the
storage unit 436. The determining unit 437 supplies the determined
target value to the comparing unit 333. The comparing unit 333
changes the target value, which is used for comparison, to the
target value supplied from the determining unit 437.
[0143] Then, in Step S35, at least one of the capacitance value of
the variable-capacitance element 231 and the capacitance value of
the variable-capacitance element 232 is changed in accordance with
the comparison result in Step S34 so that the bias voltage Vb
detected in Step S33 is substantially identical to the target value
determined in Step S52.
[0144] In this way, in the fifth embodiment, the target value is
changed for each interval to which the elapsed time belongs. For
this reason, the correcting unit 430 can perform correction so that
the bias voltage Vb is substantially identical to a target value
adjusted to the interval to which the elapsed time belongs. As a
result, it is possible to reduce a variation in the processing
dimension between different plasma treatment apparatuses while
taking into consideration a time-dependent state change inside the
treatment chamber 50.
Sixth Embodiment
[0145] Next, a plasma treatment apparatus 500 according to a sixth
embodiment will be described with reference to FIG. 17. FIG. 17 is
a diagram showing the schematic configuration of the plasma
treatment apparatus 500 according to the sixth embodiment.
Hereinafter, description will be provided focusing on differences
from the third embodiment.
[0146] The plasma treatment apparatus 500 further includes a
storage unit 570 and a controller 560.
[0147] The storage unit 570 stores correlation information
regarding a correlation between a bias voltage and a processing
shift amount. The processing shift amount is, for example, a shift
amount in the actual processing dimension from an etching mask
pattern. The storage unit 570 stores, for example, correlation
information such as shown in FIG. 18. FIG. 18 shows the actual
evaluation result of a correlation between a bias voltage and a
processing shift amount, and it can be understood that the bias
voltage and a processing shift amount has approximately a
correlation along a straight line indicated by a one-dot-chain
line. By referring to this correlation information, a processing
shift amount corresponding to a current bias voltage can be
predicted. For example, by referring to the correlation
information, it can be estimated that a processing shift amount
corresponding to a bias voltage Vb11 is L11.
[0148] The controller 560 receives the bias voltage Vb detected by
the detecting unit 290 from the detecting unit 290. The controller
560 predicts a processing shift amount corresponding to the bias
voltage Vb detected by the detecting unit 290 by referring to the
correlation information stored in the storage unit 570. The
controller 560 adjusts the processing condition on the basis of the
predicted processing shift amount so that the processing shift
amount falls within the range of a predetermined threshold value.
The processing condition which should be adjusted includes, for
example, a processing time. When the predicted processing shift
amount exceeds the range of the predetermined threshold value, the
controller 560 changes the processing time so that the processing
shift amount falls within the range of the predetermined threshold
value.
[0149] As shown in FIG. 19, a method of manufacturing a
semiconductor device using the plasma treatment apparatus 500 is
different from the third embodiment in the following respect.
[0150] In Step S61, the comparing unit 233 of the power supply
circuit 220 compares the bias voltage Vb represented by the signal
received from the detecting unit 290 with the target value Vt, and
supplies the comparison result to the changing unit 234. The
changing unit 234 determines whether or not the bias voltage Vb
detected by the detecting unit 290 is substantially identical to
the target value Vt in accordance with the supplied comparison
result. When the bias voltage Vb is not substantially identical to
the target value Vt (`No` in Step S61), the changing unit 234
progresses the process to Step S62. When the bias voltage Vb is
substantially identical to the target value Vt (`Yes` in Step S61),
the process progresses to Step S36.
[0151] In Step S62, the changing unit 234 of the power supply
circuit 220 determines whether or not the number of times in which
the bias voltage Vb is not substantially identical to the target
value Vt is equal to or greater than a predetermined number of
times. Specifically, the changing unit 234 holds the count value of
the number of times in which the bias voltage Vb is not
substantially identical to the target value Vt, and counts up the
count value of the number of times. The changing unit 234 compares
the count value after counting up with the predetermined number of
times, and when the count value is equal to or greater than the
predetermined number of times (`Yes` in Step S62), progresses the
process to Step S63. When the count value is smaller than the
predetermined number of times (`No` in Step S62), the process
progresses to Step S35.
[0152] In Step S63, the changing unit 234 of the power supply
circuit 220 supplies a signal representing the number of times, in
which the bias voltage Vb is not substantially identical to the
target value Vt, being equal to or greater than the predetermined
number of times to the controller 560. When the signal is received,
the controller 560 receives the bias voltage Vb detected by the
detecting unit 290 from the detecting unit 290. The controller 560
predicts a processing shift amount corresponding to the bias
voltage Vb detected by the detecting unit 290 by referring to the
correlation information stored in the storage unit 570.
[0153] In Step S64, the controller 560 adjusts the processing
condition on the basis of the predicted processing shift amount so
that the processing shift amount falls within the range of a
predetermined threshold value. The processing condition which
should be adjusted includes, for example, a processing time. When
the predicted processing shift amount exceeds the range of the
predetermined threshold value, the controller 560 changes the
processing time so that the processing shift amount falls within
the range of the predetermined threshold value.
[0154] In this way, in the sixth embodiment, a feedback operation
which includes the operation of the detecting unit 290 to detect
the bias voltage Vb and the operation of the correcting unit 230 to
correct the capacitance value of the power supply circuit 220 is
performed a predetermined number of times or more, if the bias
voltage Vb is not substantially identical to the target value Vt, a
processing shift amount corresponding to the detected bias voltage
Vb is predicted, and the processing condition is adjusted on the
basis of the predicted processing shift amount so that the
processing shift amount falls within a predetermined allowable
range. Therefore, even when the bias voltage Vb is not
substantially identical to the target value Vt, it is possible to
reduce a variation in the processing dimension between different
plasma treatment apparatuses.
[0155] While certain embodiments have been described, these
embodiments have been presented by way of example only, and are not
intended to limit the scope of the inventions. Indeed, the novel
embodiments described herein may be embodied in a variety of other
forms; furthermore, various omissions, substitutions and changes in
the form of the embodiments described herein may be made without
departing from the spirit of the inventions. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
inventions.
* * * * *