U.S. patent application number 16/002196 was filed with the patent office on 2018-10-25 for plasma processing apparatus and plasma processing method.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. The applicant listed for this patent is TOKYO ELECTRON LIMITED. Invention is credited to Kazuki DENPOH, Chishio KOSHIMIZU, Masashi SAITO, Jun YAMAWAKU, Yohei YAMAZAWA.
Application Number | 20180308662 16/002196 |
Document ID | / |
Family ID | 43897513 |
Filed Date | 2018-10-25 |
United States Patent
Application |
20180308662 |
Kind Code |
A1 |
YAMAZAWA; Yohei ; et
al. |
October 25, 2018 |
PLASMA PROCESSING APPARATUS AND PLASMA PROCESSING METHOD
Abstract
A plasma processing apparatus includes: an evacuable processing
chamber including a dielectric window; a substrate supporting unit,
provided in the processing chamber, for mounting thereon a target
substrate; a processing gas supply unit for supplying a desired
processing gas to the processing chamber to perform a plasma
process on the target substrate; a first RF antenna, provided on
the dielectric window, for generating a plasma by an inductive
coupling in the processing chamber; and a first RF power supply
unit for supplying an RF power to the first RF antenna. The first
RF antenna includes a primary coil provided on or above the
dielectric window and electrically connected to the first RF power
supply unit; and a secondary coil provided such that the coils are
coupled with each other by an electromagnetic induction
therebetween while being arranged closer to a bottom surface of the
dielectric window than the primary coil.
Inventors: |
YAMAZAWA; Yohei; (Yamanashi,
JP) ; SAITO; Masashi; (Yamanashi, JP) ;
DENPOH; Kazuki; (Yamanashi, JP) ; KOSHIMIZU;
Chishio; (Yamanashi, JP) ; YAMAWAKU; Jun;
(Yamanashi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TOKYO ELECTRON LIMITED |
Tokyo |
|
JP |
|
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
43897513 |
Appl. No.: |
16/002196 |
Filed: |
June 7, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15008064 |
Jan 27, 2016 |
9997332 |
|
|
16002196 |
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12913183 |
Oct 27, 2010 |
9253867 |
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15008064 |
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61265518 |
Dec 1, 2009 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/3211 20130101;
H01L 21/6831 20130101; H01J 2237/334 20130101; H01J 37/32174
20130101; H01J 37/321 20130101; H01J 37/3244 20130101; H05H 1/46
20130101; H01L 21/67069 20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32; H05H 1/46 20060101 H05H001/46; H01L 21/683 20060101
H01L021/683; H01L 21/67 20060101 H01L021/67 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 27, 2009 |
JP |
2009-245990 |
Claims
1. An apparatus comprising: a chamber configured to perform a
plasma process on a substrate; a process gas supply unit configured
to supply a process gas into the chamber; and an RF antenna
configured to generate an inductively coupled plasma from the
process gas supplied into the chamber; wherein the RF antenna
comprises: a primary coil connected to an RF power supply unit, a
secondary coil arranged without connecting to the primary coil as
well as the RF power supply unit, the secondary coil including an
endless coil and a variable capacitor provided in a loop of the
endless coil.
2. The apparatus of claim 1, wherein the secondary coil is arranged
between the chamber and the primary coil.
3. The apparatus of claim 2, wherein the secondary coil is arranged
to be concentric with the primary coil.
4. The apparatus of claim 3, wherein the chamber includes a
dielectric window, and wherein the primary coil and the secondary
coil are horizontally arranged above the dielectric window.
5. The apparatus of claim 1, wherein the secondary coil is coupled
with the primary coil by an electromagnetic induction
therebetween.
6. The apparatus of claim 5, wherein the secondary coil is
electrically floated from the primary coil.
7. The apparatus of claim 1, further comprising a control unit
configured to control an azimuthal plasma density distribution of
the inductively coupled plasma by adjusting a capacitance of the
variable capacitor.
8. The apparatus of claim 7, wherein the plasma process includes
multiple process steps, and wherein the control unit is configured
to set the capacitance of the variable capacitor with respect to
each process step.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of and based upon and
claims the benefit of priority to co-pending U.S. application Ser.
No. 15/008,064, filed Jan. 27, 2016, which is a divisional
application of U.S. application Ser. No. 12/913,183, filed Oct. 27,
2010, which is now U.S. Pat. No. 9,253,867, issued Feb. 2, 2016,
and U.S. Provisional Application No. 61/265,518, filed Dec. 1,
2009. The present application is further based upon and claims
priority to Japanese Patent Application No. 2009-245990, filed on
Oct. 27, 2009. The benefit of priority is claimed to each of the
foregoing, and the entire contents of each of the foregoing are
incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a technique for performing
a plasma process on a target substrate to be processed; and, more
particularly, to an inductively coupled plasma processing apparatus
and a plasma processing method therefor.
BACKGROUND OF THE INVENTION
[0003] In the manufacturing process of a semiconductor device or a
flat panel display (FPD), a plasma is widely used in a process such
as etching, deposit, oxidation, sputtering or the like since it has
a good reactivity with a processing gas at a relatively low
temperature. In such plasma process, the plasma is mostly generated
by a radio frequency (RF) discharge in the megahertz range.
Specifically, the plasma generated by the RF discharge is
classified into a capacitively coupled plasma and an inductively
coupled plasma.
[0004] Typically, an inductively coupled plasma processing
apparatus includes a processing chamber, at least a portion (e.g.,
a ceiling portion) of which is formed of a dielectric window; and a
coil-shaped RF antenna provided outside the dielectric window, and
an RF power is supplied to the RF antenna. The processing chamber
serves as a vacuum chamber capable of being depressurized, and a
target substrate (e.g., a semiconductor wafer, a glass substrate or
the like) to be processed is provided at a central portion of the
chamber. Further, a processing gas is introduced into a processing
space between the dielectric window and the substrate.
[0005] As an RF current flows though the RF antenna, an RF magnetic
field is generated around the RF antenna, wherein the magnetic
force lines of the RF magnetic field travel through the dielectric
window and the processing space. The temporal alteration of the
generated RF magnetic field causes an electric field to be induced
azimuthally. Moreover, electrons azimuthally accelerated by the
induced electric field collide with molecules and/or atoms of the
processing gas, to thereby ionize the processing gas and generate a
plasma in a doughnut shape.
[0006] By increasing the size of the processing space in the
chamber, the plasma is efficiently diffused in all directions
(especially, in the radical direction), thereby making the density
of the plasma on the substrate uniform. However, the uniformity of
the plasma density on the substrate that is obtained by merely
using a typical RF antenna is generally insufficient for the plasma
process.
[0007] Accordingly, even as for the inductively coupled plasma
processing apparatus, it becomes one of the most important factors
to improve the uniformity of the plasma density on the substrate,
since it determines the uniformity and the reproducibility of the
plasma process itself and, furthermore, the manufacturing
production yield.
[0008] Typically, in the plasma processing apparatus, the plasma
density may be made uniform in two, i.e., azimuthal and radial
directions.
[0009] As for the uniformity in the azimuthal direction, since the
RF antenna includes an RF input-output terminal connected through
an RF power supply line to an RF power supply in a loop thereof, it
is inevitable to employ a nonaxisymmetric antenna configuration.
This serves as a main factor that makes the plasma density
nonuniform in the azimuthal direction. Accordingly, the uniformity
in the azimuthal direction can conventionally be improved by
increasing the number of nonaxisymmetric or singularity locations
of the RF antenna at a regular interval in the same direction (see,
e.g., U.S. Pat. No. 5,800,619). Alternatively, by using two-layered
series-connected coils as the RF antenna, wherein the RF power
supply wire-connected locations (input-output terminals) provided
in the upper coil are hidden behind the lower coil, the locations
may not be electromagnetically seen from the plasma (see, e.g.,
Japanese Patent Application Publication No. 2003-517197).
[0010] Moreover, as for the radial direction, the plasma density
distribution characteristics (profile) of the plasma generated in
the doughnut shape around the dielectric window in the chamber are
important and, thus, the profile of the core plasma density
distribution determines the uniformity of the plasma density
distribution that can be obtained on the substrate after the
diffusion. In this regard, the conventional method for dividing the
RF antenna into a plurality of segments in the radial direction is
mostly employed. Further, such RF antenna dividing method includes
a first method for individually supplying RF powers to the
respective antenna segments (see, e.g., U.S. Pat. No. 5,401,350);
and a second method for controlling the division ratio of the RF
power that is divided from one RF power supply to all the antenna
segments by changing each impedance of the antenna segments in an
additional circuit such as a capacitor or the like (see, e.g., U.S.
Pat. No. 5,907,221).
[0011] However, such conventional methods for improving the
uniformity of the plasma density distribution is disadvantageous in
that it is difficult to manufacture any type of RF antenna for
improving the uniformity in the azimuthal or radial direction due
to its complex configuration; or the loads of the RF power supply
system (RF power supply and matcher) are increased.
[0012] Especially, the conventional method for improving the
uniformity in the azimuthal direction of the plasma density
distribution has the restriction in the accuracy and improvement of
the uniformity since an antenna portion (e.g., the lower antenna)
attributable to the generation of inductive coupling plasma does
not have an exactly axisymmetric shape.
SUMMARY OF THE INVENTION
[0013] In view of the above, the present invention provides an
inductively coupled plasma processing apparatus and a plasma
processing method therefor, capable of improving the uniformity and
controllability of a plasma density distribution, with a simple
configuration of its RF antenna that can easily be manufactured
since loads of its RF power supply system become small.
[0014] In accordance with an aspect of the present invention, there
is provided a plasma processing apparatus. The apparatus includes:
a processing chamber including a dielectric window; a substrate
supporting unit, provided in the processing chamber, for mounting
thereon a target substrate to be processed; a processing gas supply
unit for supplying a desired processing gas to the processing
chamber to perform a desired plasma process on the target
substrate; a first RF antenna, provided on the dielectric window,
for generating a plasma from the processing gas by an inductive
coupling in the processing chamber; and a first RF power supply
unit for supplying an RF power to the first RF antenna, the RF
power having an appropriate frequency for RF discharge of the
processing gas. The first RF antenna includes a primary coil
provided on or above the dielectric window and electrically
connected to the first RF power supply unit through an RF power
supply line; and a secondary coil provided at a portion such that
the coils are coupled with each other by an electromagnetic
induction therebetween, the secondary coil arranged closer to a
bottom surface of the dielectric window than the primary coil.
[0015] In accordance with another aspect of the present invention,
there is provided a plasma processing method. The method includes:
arranging a target substrate to be processed at a predetermined
portion below a dielectric window in a processing chamber including
the dielectric window; supplying a desired processing gas to the
processing chamber from a processing gas supply unit; maintaining a
depressurized state of the processing chamber at a predetermined
pressure level; supplying an RF power having a preset frequency
from an RF power source to a primary coil arranged on or above the
dielectric window to allow an RF current to flow through the
primary coil; inducing a current through the RF current by an
electromagnetic induction to allow the induced current to flow
through a secondary coil arranged closer to a bottom surface of the
dielectric window than the primary coil; generating a plasma from
the processing gas close to the dielectric window in the processing
chamber by an induced electric field and an RF power magnetic field
generated by the induced current flowing through the secondary
coil; diffusing the generated plasma in the processing chamber; and
performing a desired plasma process on the target substrate by
using the plasma.
[0016] In the present invention, once an RF power for RF discharge
is supplied to the primary coil and, thus, the RF current flows
through the primary coil, an RF energy is transferred from the
primary coil to the secondary coil by the inductive coupling and,
thus, the inductive coupling plasma is generated by the
electromagnetic energy that is transferred from the secondary coil
to the processing chamber through the dielectric window. In other
words, by coupling by the electromagnetic induction the primary
coil with the secondary coil and the secondary coil with the plasma
in the processing chamber, the RF power is supplied to the load,
i.e., the plasma in the processing chamber through the primary coil
and the secondary coil. The secondary coil for mostly supplying the
electromagnetic energy to the processing gas in the processing
chamber can be formed of one or more completely axisymmetric
endless coils having no space-like singularity (power-supply
point).
[0017] Accordingly, it is possible to make the plasma density of
the plasma generated in the doughnut shape in the processing space
of the processing chamber uniform in the azimuthal direction and,
furthermore, the density distribution of the plasma around the
substrate supporting unit (i.e., on the semiconductor wafer W)
uniform in the azimuthal direction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The objects and features of the present invention will
become apparent from the following description of embodiments,
given in conjunction with the accompanying drawings, in which:
[0019] FIG. 1 is a longitudinal cross sectional view showing a
configuration of an inductively coupled plasma etching apparatus in
accordance with an embodiment of the present invention;
[0020] FIG. 2 is a perspective view showing main elements of a
plasma generation unit in the inductively coupled plasma etching
apparatus shown in FIG. 1;
[0021] FIG. 3A is a perspective view showing a concentric coil;
[0022] FIG. 3B is a perspective view showing a spiral coil;
[0023] FIG. 4A is a schematic cross sectional view showing a first
modification of the layout configuration of an RF antenna in
accordance with the present embodiment;
[0024] FIG. 4B is a schematic cross sectional view showing a second
modification of the layout configuration of the RF antenna in
accordance with the present embodiment;
[0025] FIG. 4C is a schematic cross sectional view showing a third
modification of the layout configuration of the RF antenna in
accordance with the present embodiment;
[0026] FIG. 4D is a schematic cross sectional view showing a fourth
modification of the layout configuration of the RF antenna in
accordance with the present embodiment;
[0027] FIG. 4E is a schematic cross sectional view showing a fifth
modification of the layout configuration of the RF antenna in
accordance with the present embodiment;
[0028] FIG. 5 shows a modification of an RF power supply layout of
the RF antenna in accordance with the present embodiment;
[0029] FIG. 6 shows another modification of the RF power supply
layout of the RF antenna in accordance with the present
embodiment;
[0030] FIG. 7A a perspective view schematically showing an example
of an antenna layout configuration in the case of including a
plurality of RF antennas;
[0031] FIG. 7B is a schematic cross sectional view showing the
antenna layout configuration;
[0032] FIG. 8A is a perspective view showing how capacitors are
respectively provided in loops of the RF antennas in accordance
with the present embodiment;
[0033] FIG. 8B is a top view showing how the capacitors are
respectively provided in the loops of the RF antennas in accordance
with the present embodiment;
[0034] FIG. 9A is a contour plot diagram showing a distribution of
an induced current that is excited in a plasma in a test example
and a comparison example;
[0035] FIG. 9B is a circling plot diagram showing the distribution
of the induced current that is excited in the plasma in the test
example and the comparison example;
[0036] FIG. 10 is a bar graph showing a ratio of an induced
(secondary) current flowing through an endless coil provided at
each radial position of a secondary coil to an RF (primary) current
flowing through a primary coil in the test example;
[0037] FIG. 11 is a graph showing a radial distribution of the
density of a current that is excited in the plasma when an RF
current of 1 A is supplied to the primary coil in the test example
and the comparison example;
[0038] FIG. 12A is a bar graph showing a ratio of an induced
(secondary) current flowing through an endless coil provided at
each radial position of the secondary coil to an RF (primary)
current flowing through the primary coil in a first capacitance
adjusting example of the test example;
[0039] FIG. 12B is a graph showing a radial distribution of the
density of a current that is excited in the plasma when an RF
current of 1 A is supplied to the primary coil in the first
capacitance adjusting example of the test example;
[0040] FIG. 13A is a bar graph showing a ratio of an induced
(secondary) current flowing through an endless coil provided at
each radial position of the secondary coil to an RF (primary)
current flowing through the primary coil in a second capacitance
adjusting example of the test example;
[0041] FIG. 13B is a graph showing a radial distribution of the
density of a current that is excited in the plasma when an RF
current of 1 A is supplied to the primary coil in the second
capacitance adjusting example of the test example;
[0042] FIG. 14A is a bar graph showing a ratio of an induced
(secondary) current flowing through an endless coil provided at
each radial position of the secondary coil to an RF (primary)
current flowing through the primary coil in a third capacitance
adjusting example of the test example;
[0043] FIG. 14B is a graph showing a radial distribution of the
density of a current that is excited in the plasma when an RF
current of 1 A is supplied to the primary coil in the third
capacitance adjusting example of the test example;
[0044] FIG. 15A is a bar graph showing a ratio of an induced
(secondary) current flowing through an endless coil provided at
each radial position of the secondary coil to an RF (primary)
current flowing through a primary coil in a fourth capacitance
adjusting example of the test example;
[0045] FIG. 15B is a graph showing a radial distribution of the
density of a current that is excited in the plasma when an RF
current of 1 A is supplied to the primary coil in the fourth
capacitance adjusting example of the test example;
[0046] FIG. 16A is a bar graph showing a ratio of an induced
(secondary) current flowing through an endless coil provided at
each radial position of the secondary coil to an RF (primary)
current flowing through the primary coil in a fifth capacitance
adjusting example of the test example;
[0047] FIG. 16B is a graph showing a radial distribution of the
density of a current that is excited in the plasma when an RF
current of 1 A is supplied to the primary coil in the fifth
capacitance adjusting example of the test example;
[0048] FIGS. 17A to 17D stepwisely show a process of a multilayer
resist method;
[0049] FIG. 18 is a perspective view showing a test example where
the secondary coil is rotated in the inductively coupled plasma
etching apparatus in accordance with the present embodiment;
and
[0050] FIG. 19 is a top view showing a modification of a coil
configuration of the secondary coil in accordance with the present
embodiment.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0051] An embodiment of the present invention will now be described
with reference to the accompanying drawings which form a part
hereof.
[0052] FIG. 1 shows a configuration of an inductively coupled
plasma etching apparatus in accordance with an embodiment of the
present invention. The inductively coupled plasma etching apparatus
is of a type using a planar coil type RF antenna, and includes a
cylindrical vacuum chamber (processing chamber) 10 made of a metal,
e.g., aluminum, stainless steel or the like. The chamber 10 is
frame-grounded.
[0053] In the inductively coupled plasma etching apparatus, various
units having no involvement in plasma generation will be described
first.
[0054] At a lower central portion of the chamber 10, a circular
plate-shaped susceptor 12 for mounting thereon a target substrate,
e.g., a semiconductor wafer W as a substrate supporting table is
horizontally arranged. The susceptor 12 also serves as an RF
electrode. The susceptor 12, which is made of, e.g., aluminum, is
supported by an insulating tubular support 14 uprightly extending
from a bottom portion of the chamber 10.
[0055] A conductive tubular support part 16 is provided uprightly
extending from the bottom portion of the chamber 10 along the
periphery of the insulating tubular support 14, and an annular
exhaust path 18 is defined between the support part 16 and an inner
wall of the chamber 10. Moreover, an annular baffle plate 20 is
attached to an entrance or a top portion of the exhaust path 18,
and an exhaust port 22 is provided at a bottom portion thereof.
[0056] To allow a gas to uniformly flow in the chamber 10
axisymmetrically with regard to the semiconductor wafer W on the
susceptor 12, it is preferable to provide a plural number of
exhaust ports 22 at a regular interval circumferentially. The
exhaust ports 22 are connected to an exhaust device 26 via
respective exhaust pipes 24. The exhaust device 26 includes a
vacuum pump such as a turbo molecular pump to evacuate a
plasma-processing space in the chamber 10 to a predetermined vacuum
level. Attached to the sidewall of the chamber 10 is a gate valve
28 for opening and closing a loading/unloading port 27.
[0057] An RF power supply 30 for an RF bias is electrically
connected to the susceptor 12 via a matcher 32 and a power supply
rod 34. The RF power supply 30 outputs a variable RF power RF.sub.L
of an appropriate frequency (e.g., 13.56 MHz or less) to control
the energy for attracting ions toward the semiconductor wafer W.
The matcher 32 includes a variable-reactance matching circuit for
performing the matching between the impedances of the RF power
supply 30 and the load (mainly, susceptor, plasma and chamber), and
the matching circuit includes a blocking capacitor for generating a
self-bias.
[0058] An electrostatic chuck 36 is provided on an upper surface of
the susceptor 12 to hold the semiconductor wafer W by an
electrostatic attraction force, and a focus ring 38 is provided
around the electrostatic chuck 36 to annularly surround the
periphery of the semiconductor wafer W. The electrostatic chuck 36
includes an electrode 36a made of a conductive film and a pair of
dielectric films 36b and 36c. A high voltage DC power supply 40 is
electrically connected to the electrode 36a via a switch 42 by
using a coated line 43. By applying a high DC voltage from the DC
power supply 40 to the electrode 36a, the semiconductor wafer W can
be attracted to and held on the electrostatic chuck 36 by the
electrostatic force.
[0059] A coolant path 44, which extends in, e.g., a circumferential
direction, is provided inside the susceptor 12. A coolant, e.g., a
cooling water, of a predetermined temperature is supplied from a
chiller unit (not shown) to the coolant path 44 to be circulated
through pipelines 46 and 48. By adjusting the temperature of the
coolant, it is possible to control a process temperature of the
semiconductor wafer W held on the electrostatic chuck 36.
[0060] Moreover, a heat transfer gas, e.g., He gas, is supplied
from a heat transfer gas supply unit (not shown) to a space between
a top surface of the electrostatic chuck 36 and a bottom surface of
the semiconductor wafer W through a gas supply line 50. Further, an
elevating mechanism (not shown) including lift pins capable of
being moved up and down while vertically extending through the
susceptor 12 and the like is provided to load and unload the
semiconductor wafer W.
[0061] Next, various units having involvement in the plasma
generation in the inductively coupled plasma etching apparatus will
be described. FIG. 2 shows main elements of a plasma generation
unit in the inductively coupled plasma etching apparatus.
[0062] A ceiling of the chamber 10 is separated from the susceptor
12 at a relatively large distance, and a circular dielectric window
52 formed of, e.g., a quartz plate is airtightly provided in the
ceiling. As a single unit with the chamber 10, an antenna chamber
56 for accommodating an RF antenna 54 while electronically
shielding it from the outside is provided on the dielectric window
52. The RF antenna 54 is used to generate an inductively coupled
plasma in the chamber 10.
[0063] In the present embodiment, the RF antenna 54 includes a
primary coil 62 arranged above and separated from the dielectric
window 52 and connected to an RF power supply line 60 of an RF
power supply unit 58; and a secondary coil 64 arranged at a portion
such that the coils 62 and 64 can be coupled with each other by the
electromagnetic induction therebetween while being electrically
floated from the primary coil 62 closer to a bottom surface (i.e.,
a surface facing the processing space) of the dielectric window 52
than the primary coil 62.
[0064] In FIG. 2, the secondary coil 64 is horizontally mounted on
the top surface of dielectric window 52, and the primary coil 62 is
horizontally mounted on a support plate 66 formed of an insulator,
provided above and separated from the secondary coil 64 at an
appropriate distance. Typically, the coils 62 and 64 are arranged
to be concentric with each other horizontally and, furthermore,
with the chamber 10 and the susceptor 12 horizontally.
[0065] Preferably, the primary coil 62 formed of, e.g., a
multi-wound coil has a concentric shape with regular radiuses as
shown in FIGS. 2 and 3A. Alternatively, the primary coil 62 may
have another shape, e.g., a spiral shape shown in FIG. 3B.
Typically, a central end portion of the primary coil 62 is
connected to the RF power supply line of the RF power supply unit
58, and a peripheral end portion is electrically connected to a
ground potential through a ground line 68. The primary coil 62 is
preferably made of, e.g., a copper-based metal having a high
conductivity.
[0066] Preferably, as shown in FIG. 2A, the secondary coil 64 is,
e.g., a combination coil including a plurality of, e.g., three,
endless coils 64(1) to 64(3) having different diameters that are
concentrically arranged. Each of the endless coils 64(1) to 64(3)
is preferably made of, e.g., a copper-based metal having a high
conductivity. Alternatively, the endless coils 64(1) to 64(3) may
be made of, e.g., a semiconductor such as Si or SiC.
[0067] In FIG. 2, the primary coil is formed of the concentric coil
that is wound three times. An inner wound portion 62(1), an
intermediate wound portion 62(2) and an outer wound portion 62(3)
of the primary coil 62 are respectively arranged to vertically
opposite to the inner endless coil 64(1), the intermediate endless
coil 64(2) and the outer endless coil 64(3) of the secondary coil
64.
[0068] The RF power supply unit 58 includes an RF power supply 70
and a matcher 72 and outputs a variable RF power RF.sub.H of an
appropriate frequency (e.g., 13.56 MHz or more) for plasma
generation by RF discharge. The matcher 72 includes a
variable-reactance matching circuit for performing the matching
between the impedances of the RF power supply 70 and the load
(mainly, RF antenna, plasma and correction coil).
[0069] A processing gas supply unit for supplying a processing gas
to the chamber 10 includes an annular manifold or buffer unit 74
provided inside (or outside) the sidewall of the chamber 10 to be
located at a place slightly lower than the dielectric window 52; a
plurality of sidewall gas injection holes 76 circumferentially
formed on the sidewall at a regular interval and opened to the
plasma-generation space from the buffer unit 74; and a gas supply
line 80 extended from a processing gas supply source 78 to the
buffer unit 74. The processing gas supply source 78 includes a mass
flow controller and an on-off valve, which are not shown.
[0070] A main control unit 82 includes, e.g., a microcomputer and
controls the overall operation (sequence) of the plasma etching
apparatus and individual operations of various units, e.g., the
exhaust device 26, the RF power supplies 30 and 70, the matchers 32
and 72, the switch 42 of the electrostatic chuck, the processing
gas supply source 78, the chiller unit (not shown), the
heat-transfer gas supply unit (not shown) and the like.
[0071] When the inductively coupled plasma etching apparatus
performs an etching process, the gate valve 28 is first opened to
load a target substrate, i.e., a semiconductor wafer W, into the
chamber 10 and mount it onto the electrostatic chuck 36. Then, the
gate valve 28 is closed, and an etching gas (typically, a gaseous
mixture) is introduced from the processing gas supply source 78,
via the buffer unit 74, into the chamber 10 at a preset flow rate
and flow rate ratio through the sidewall gas injection holes 76 by
using the gas supply line 80. Thereafter, the RF power supply 70 of
the RF power supply unit 58 is turned on to output a
plasma-generating RF power RF.sub.H at a predetermined RF level, so
that a current of the RF power RF.sub.H is supplied to the primary
coil 62 of the RF antenna 54 through the RF power supply line 60
via the matcher 72. In addition, the RF power supply 30 is turned
on to output an ion-attracting control RF power RF.sub.L at a
predetermined RF level, so that the RF power RF.sub.L is supplied
to the susceptor 12 through the power supply rod 34 via the matcher
32.
[0072] Further, a heat-transfer gas (i.e., He gas) is supplied from
the heat-transfer gas supply unit to a contact interface between
the electrostatic chuck 36 and the semiconductor wafer W, and the
switch is turned on, so that the heat-transfer gas is confined in
the contact interface by the electrostatic attraction force of the
electrostatic chuck 36.
[0073] The etching gas injected through the sidewall gas injection
holes 76 is uniformly diffused in the processing space below the
dielectric window 52. At this time, magnetic force lines (magnetic
flux) generated around the primary coil 62 by the current of the RF
power RF.sub.H flowing through the primary coil 62 of the RF
antenna 54 are interlinked with the secondary coil 64, so that an
electromotive force is induced in the secondary coil by the
temporal alteration of the generated magnetic flux, thereby
allowing a current (i.e., an induced current) to flow in the
loop.
[0074] Magnetic force lines are generated by the induced current
flowing through the secondary coil 64, and the generated magnetic
force lines travel through dielectric window 52 and across the
processing space (plasma generation space) of the chamber 10, to
thereby induce an electric field azimuthally in the processing
space. Electrons azimuthally accelerated by the induced electric
field collide with molecules and/or atoms in the etching gas, to
thereby ionize the etching gas and generate a plasma in a doughnut
shape. As such, the plasma is dominantly generated by the electric
field caused by the secondary coil 64, while it is hardly affected
by the primary coil 62.
[0075] Here, the expression "plasma in a doughnut shape" indicates
not only a state where the plasma is generated only at the radially
outer portion in the chamber 10 without being generated at the
radially inner portion (at the central portion) therein but also a
state where the volume or density of the plasma generated at the
radially outer portion becomes larger than that at the radially
inner portion. Moreover, if the kind of the processing gas, the
pressure inside the chamber 10 and/or the like are changed, the
plasma may be generated in another shape instead of the doughnut
shape.
[0076] In the wide processing space, radicals and ions of the
plasma generated in the doughnut shape are diffused in all
directions, so that the radicals isotropically pour down and the
ions are attracted by the DC bias onto a top surface (target
surface) of the semiconductor wafer W. Accordingly, plasma active
species cause chemical and physical reactions on the target surface
of the semiconductor wafer W, thereby etching a target film into a
predetermined pattern. In the present embodiment, as will be
described later, it is possible to significantly improve the radial
uniformities in the plasma process properties in the azimuthal
direction as well as in the radial direction, i.e., etching
properties (etching rate, selectivity, etching shape and the like),
of the semiconductor wafer W.
[0077] As such, in the inductively coupled plasma etching apparatus
of the present embodiment, the RF antenna 54 provided above a
ceiling window (in the antenna chamber 56) of the chamber 10
includes the primary coil 62 and the secondary coil 64 arranged one
above the other and completely separated from each other.
Accordingly, once an RF power RF.sub.H for the RF discharge is
supplied from the RF power supply unit 58 to the primary coil 62,
the energy is transferred by the inductive coupling between the
coils 62 and 64 and, thus, an inductively coupled plasma is
generated by the electromagnetic energy that is discharged from the
secondary coil 64 into the processing gas in the chamber 10 by
traveling through dielectric window 52.
[0078] In other words, by coupling by the electromagnetic induction
the coils 62 and 64 with each other and the secondary coil 64 with
the plasma in the chamber 10, the RF power RF.sub.H is supplied to
the load, i.e., the plasma in the chamber 10 through the coils 62
and 64.
[0079] With such method for supplying an RF power to a plasma
through the inductive coupling between a plurality of coils, it is
possible to provide the final stage coil, i.e., the secondary coil
64 for supplying the electromagnetic energy to the processing gas
in the chamber 10 through the dielectric window 52, serving as a
completely axisymmetric endless coil having no space-like
singularity (power-supply point). Accordingly, it is possible to
make the plasma density of the plasma generated in the doughnut
shape in the processing space of the chamber 10 uniform in the
azimuthal direction and, furthermore, the density distribution of
the plasma around the susceptor 12 (i.e., on the semiconductor
wafer W) uniform in the azimuthal direction.
[0080] Further, since each of the coils 62 and 64 has a simple
configuration, it is possible to easily manufacture the coils 62
and 64. No significant load is applied to the RF power supply unit
58.
[0081] Besides, since the primary coil 62 includes an input-output
terminal for RF power supply and is not an axisymmetric coil, the
magnetic flux interlinked with the secondary coil 64, i.e., a
magnetic field generated around the primary coil 62 by the RF power
RF.sub.H flowing through the primary coil 62, is not uniform in the
azimuthal direction. However, the induced current flowing through
the secondary coil 64 is the same at any portion of the loop, and
the secondary coil 64 is an axisymmetric circular endless coil.
Accordingly, a magnetic field generated around the secondary coil
64 (specifically, in the chamber 10) by the induced current flowing
therethrough becomes uniform over one period in the azimuthal
direction.
[0082] In the RF antenna 54 of the present embodiment, the planar
primary coil 62 is horizontally arranged above the dielectric
window 52, and the planar secondary coil 64 is horizontally mounted
on the top surface of the dielectric window 52. However, in the
present invention, such layout configuration of the RF antenna 54
is merely an example, and various modifications may be made
instead.
[0083] As described above, the secondary coil 64 is formed of one
or more endless coils 64(1) to 64(3), and the line connection to
the outside is unnecessary. Accordingly, as shown in FIG. 4A, the
secondary coil 64 (endless coils 64(1) to 64(3)) may be buried in
the dielectric window 52. In this case, as the layout configuration
shown in FIG. 4B, it is preferable to provide each of the endless
coils 64(1) to 64(3) at independent height positions.
Alternatively, one part of the secondary coil 64 (endless coils
64(1) to 64(3)) may be provided in the dielectric window 52, and
the other part thereof may be provided on the dielectric window
52.
[0084] Similarly, the primary coil 62 is not limited to the planar
type. For example, as shown in FIG. 4B, the height positions of the
wound portions 62(1) to 62(3) may preferably be changed depending
on those of the corresponding endless coils 64(1) to 64(3) in such
a way that the overall valance and the efficiency of the inductive
coupling between the wound portions 62(1) to 62(3) and the
corresponding endless coils 64(1) to 64(3) can be optimized.
[0085] Further alternatively, as shown in FIG. 4C, one part, e.g.,
the outer endless coil 64(3) of the endless coils 64(1) to 64(3) of
the secondary coil 64 may be arranged immediately below the
dielectric window 52, i.e., a plasma-generation area in the chamber
10. However, in case that the endless coil 64(3) is made of, e.g.,
a metal such as copper, it is preferable to cover the endless coil
64(3) with an anti-contamination hollow ring cover 84 made of,
e.g., quartz.
[0086] Further, in case that the secondary coil 64 is provided in
the dielectric window 52 or the chamber 10, the primary coil 62 may
be arranged closest to the dielectric window 52. For example, as
shown in FIG. 4C, the primary coil 62 may be arranged on the top
surface of the dielectric window 52.
[0087] As another layout configuration shown in FIGS. 4D and 4E, in
case that each of the endless coils 64(1) to 64(3) of the secondary
coil 64 is made of, e.g., Si or SiC, the endless coils 64(1) to
64(3) may be exposed without being covered with in the hollow ring
cover and arranged on the bottom surface of the dielectric window
52 or in the plasma-generation area.
[0088] In the present embodiment, there may be various
modifications of the supplying method for supplying the RF power
RF.sub.H to the primary coil 62 of the RF antenna 54.
[0089] In the RF antenna 54 shown in FIG. 2, the wound portions
62(1) to 62(3) of the primary coil 62 are connected in series to
the single RF power supply unit 58.
[0090] However, as shown in FIG. 5, the wound portions 62(1) to
62(3) may be connected in parallel to the single RF power supply
unit 58. In this case, the current of the RF power RF.sub.H
supplied from the RF power supply unit 58 is branched into the
wound portions 62(1) to 62(3). Relatively large current is supplied
to the wound portion having a relatively low impedance (typically,
the internal wound portion 62(1)), and relatively small current is
supplied to the wound portion having a relatively high impedance
(typically, the outer wound portion 62(3)).
[0091] Alternatively, as shown in FIG. 6, the wound portions 62(1)
to 62(3) may respectively be connected to a plurality of the RF
power supply units 58(1) to 58(3). In this case, RF currents or RF
current powers may respectively be supplied from the RF power
supply units 58(1) to 58(3) to the wound portions 62(1) to 62(3)
regardless of their relative impedances.
[0092] Further alternatively, as shown in FIGS. 7A and 7B, an
additional RF antenna 86 that is independent of the RF antenna 54
may be arranged around the dielectric window 52. In FIGS. 7A and
7B, the RF antennas 54 and 86 are respectively arranged at the
radially inner portion (central portion) and the radially outer
portion (peripheral portion) of the dielectric window 52. The RF
antenna 86 may be a single-wound (or multi-wound) concentric coil
as shown above or a spiral coil. Preferably, dedicated RF power
supply units 58(1) and 58(2) are respectively provided to supply RF
currents of different levels to both of the RF antennas 54 and 86.
However, the RF current supplied from the single RF power supply
unit 58 may be divided into two RF currents to be supplied to the
RF antennas 54 and 86.
[0093] Meanwhile, a capacitor may preferably be provided in the
loop of the secondary coil 64 of the RF antenna 54. In case that
the secondary coil 64 is formed of the endless coils 64(1) to
64(3), the capacitor may be provided in the loop of one (e.g., the
endless coil 64(3)) or the loops of all the endless coils 64(1) to
64(3). Specifically, a cutout having a gap width of, e.g., 5 mm may
be formed at a circumferential location of each coil conductor of
the endless coil 64(1) to 64(3), and a capacitor may be provided at
each of the cutouts. FIGS. 8A and 8B show an example where
capacitors 90(1) to 90(3) are respectively provided in the loops of
the endless coils 64(1) to 64(3).
[0094] Following electromagnetic field simulations were performed
by the present inventors for the inductively coupled plasma etching
apparatus of the present embodiment.
[0095] In other words, as a result of obtaining the distribution of
an induced current that was excited in a plasma in the inductively
coupled plasma etching apparatus shown in FIG. 1 where capacitors
were inserted into the secondary coil 64, the characteristics shown
in FIG. 9A (contour plot diagram) and FIG. 9B (circling plot
diagram) were obtained. In FIGS. 9A and 9B, the distributions of
the induced currents excited in the plasma were shown in the cases
that no secondary coil 64 was provided and the primary coil 62 was
provided on the top surface of the dielectric window 52 as a
comparison example; and the coils 62 and 64 and the capacitors
90(1) to 90(4) were provided as a test example, in the inductively
coupled plasma etching apparatus shown in FIG. 1.
[0096] In the electromagnetic field simulations, the primary coil
62 was formed of a concentric coil that was wound four times, where
a first, a second, a third and a fourth wound portion had radials
of about 70, 120, 170 and 220 mm, respectively. Conforming to the
coil configuration of the primary coil 62, the secondary coil 64
included four concentrically arranged endless coils 64(1) to 64(4)
having radials of about 70, 120, 170 and 220 mm, respectively.
[0097] In addition, in the electromagnetic field simulations, the
secondary coil 64 was arranged on the top surface of the dielectric
window 52, and the primary coil 62 was arranged above and at a
distance of about 5 mm from the secondary coil 64. The capacitors
90(1) to 90(4) respectively had the capacitances of about 1547,
650, 400 and 250 pF. As the plasma generated in the doughnut by the
inductive coupling in the processing space, a disk-shaped
resistance was simulated, where its radius, resistivity and skin
thickness were set to be about 250 mm, 100 .OMEGA.cm and 10 mm,
respectively. The plasma-generating RF power RF.sub.H had a
frequency of about 13.56 MHz.
[0098] As shown in FIGS. 9A and 9B, in the comparison example, it
was seen that there was a bias in the induced current in the plasma
approximately in the 9 o'clock direction (the 180.degree. direction
based on the forward direction of the X-axis in the circling
direction) corresponding to a portion of an RF power supply
input/output terminal of the primary coil 62. On the other hand, in
the test example, it was seen that there was no bias in the
circling direction. Further, it has been known that the induced
current in the plasma which is nonuniform in the radial direction
results in a uniform plasma density in the diametrical direction
after the diffusion.
[0099] Additionally, in the test example of the electromagnetic
field simulations, as the result of obtaining the induced
(secondary) current flowing through each of the endless coils 64(1)
to 64(4) of the secondary coil 64 when an RF (primary) current of 1
A was supplied to the primary coil 62 in the RF antenna 54, the
graph shown in FIG. 10 showing the ratio of the induced (secondary)
current of each radial position to the RF (primary) current was
obtained. FIG. 10 indicates that the induced (secondary) current
increased about one to five times as much as the RF (primary)
current flowed at each radial position.
[0100] Moreover, in the test example and the comparison example,
the characteristics shown in FIG. 11 were obtained as the result of
analysis on a radial distribution of the density (corresponding to
the plasma density) of a current excited in the plasma. FIG. 11
indicates that there was the difference by about five times at the
maximum in the current density in the plasma depending on whether
or not the secondary coil 64 existed and, resultantly, a large
current could be generated in the plasma by the current
multiplication effect.
[0101] Typically, in the inductive coupling method, it is required
to increase the winding density of an antenna or a coil in order to
increase a current excited in the plasma. This, however, inevitably
extends the length of the coil, causing the wavelength effect. On
the other hand, in the present embodiment, it is possible to
increase the current excited in the plasma without increasing the
winding density. Further, since it is sufficient to supply a small
current from the matcher 72 of the RF power supply unit 58 to the
primary coil 62, it is possible to easily perform the matching
while preventing a power loss in the matcher 72.
[0102] In the present embodiment, it is preferable to employ
variable capacitors as the capacitors provided in the loop of the
secondary coil 64. In the electromagnetic field simulations,
variable capacitors were employed for the capacitors 90(1) to 90(4)
respectively provided in the loops of the endless coils 64(1) to
64(4), and the induced (secondary) current flowing through each
radial position of the endless coils 64(1) to 64(4) was obtained by
variously changing the each capacitance of the capacitors 90(1) to
90(4) with a plurality of combinations. Resultantly, the
characteristics shown in FIGS. 12A to 16B were obtained as the
radial distribution of the densities of currents generated in the
plasma and the ratios of the induced (secondary) currents of
respective radial positions to the RF (primary) currents of the
primary coil 62.
[0103] (First Capacitance Adjusting Example)
[0104] In case that the capacitances of the capacitors 90(1) to
90(4) were respectively set to be 1547, 650, 400 and 250 pF, the
results shown in FIGS. 12A and 12B were respectively obtained as
the ratios of the induced (secondary) currents to the RF (primary)
currents and the radial distribution of the density of currents
generated in the plasma.
[0105] Specifically, as shown in FIG. 12A, the largest current
flowed through the endless coil 64(3) (r=170 mm), and the smallest
current flowed through the endless coil 64(1) (r=70 mm).
Intermediate currents respectively flowed through the endless coils
64(2) (r=120) and 64(3) (r=220). Moreover, as shown in FIG. 12B,
the radial distribution of the density of currents generated in the
plasma showed a profile of the relative magnitude relationship of
the induced currents of the four respective radial positions. That
is, the density of currents generated in the plasma showed a
mountain-shaped profile in which it had a significantly great value
around a portion r=170 mm.
[0106] (Second Capacitance Adjusting Example)
[0107] In case that the capacitances of the capacitors 90(1) to
90(4) were respectively set to be 3000, 300, 300 and 380 pF, the
results shown in FIGS. 13A and 13B were respectively obtained as
the ratios of the induced (secondary) currents to the RF (primary)
currents and the radial distribution of the density of currents
generated in the plasma.
[0108] Specifically, as shown in FIG. 13A, the largest current
flowed through the endless coil 64(4) (r=220 mm), and currents of
magnitudes of about 1/3 of that of the largest current respectively
flowed through the other endless coils 64(1) to 64(3) (r=70, 120
and 170). Moreover, as shown in FIG. 13B, the radial distribution
of the density of currents generated in the plasma showed a profile
of the relative magnitude relationship of the induced currents of
the four respective radial positions. That is, the density of
currents generated in the plasma showed a profile in which the
current density of a portion (r=70 mm) closer to the center in the
radial direction tended to become lower than that of an
intermediate portion (r=120 to 170) in the radial direction.
[0109] (Third Capacitance Adjusting Example)
[0110] In case that the capacitances of the capacitors 90(1) to
90(4) were respectively set to be 1547, 650, 300 and 380 pF, the
results shown in FIGS. 14A and 14B were respectively obtained as
the ratios of the induced (secondary) currents to the RF (primary)
currents and the radial distribution of the density of currents
generated in the plasma.
[0111] Specifically, as shown in FIG. 14A, the induced currents
were divided into two groups. That is, larger currents flowed
respectively through the endless coils 64(2) and 64(4) (r=120 and
220 mm), and smaller currents respectively flowed through the
endless coils 64(1) to 64(3) (r=70 and 170). Moreover, as shown in
FIG. 14B, the radial distribution of the density of currents
generated in the plasma showed a profile of the relative magnitude
relationship of the induced currents of the four respective radial
positions. That is, the density of currents generated in the plasma
showed a profile in which it had local maximum values around two
intermediate portions (r=120 and 170 mm, respectively) in the
radial direction.
[0112] (Fourth Capacitance Adjusting Example)
[0113] In case that the capacitances of the capacitors 90(1) to
90(4) were respectively set to be 1400, 500, 586 and 380 pF, the
results shown in FIGS. 15A and 15B were respectively obtained as
the ratios of the induced (secondary) currents to the RF (primary)
currents and the radial distribution of the density of currents
generated in the plasma.
[0114] Specifically, as shown in FIG. 15A, the largest current
flowed through the endless coil 64(1) (r=70 mm), and currents of
magnitudes of about 3/5 of that of the largest current respectively
flowed through the other endless coils 64(2) to 64(4) (r=120, 170
and 220). Moreover, as shown in FIG. 15B, the radial distribution
of the density of currents generated in the plasma showed a profile
of the relative magnitude relationship of the induced currents of
the four respective radial positions. The density of currents
generated in the plasma was significantly decreased around an
intermediate portion (r=120 to 170 mm) in the radial direction.
[0115] (Fifth Capacitance Adjusting Example)
[0116] In case that the capacitances of the capacitors 90(1) to
90(4) were respectively set to be 1547, 300, 300 and 380 pF, the
results shown in FIGS. 16A and 16B were respectively obtained as
the ratios of the induced (secondary) currents to the RF (primary)
currents and the radial distribution of the density of currents
generated in the plasma.
[0117] Specifically, as shown in FIG. 16A, the largest current
flowed through the endless coil 64(4) (r=220 mm), and a current of
magnitude of about 2/3 of that of the largest current flowed
through the endless coil 64(1) (r=70 mm). Currents of magnitudes of
about 1/3 of that of the largest current respectively flowed
through the endless coils 64(2) and 64(3) (r=120 and 170).
Moreover, as shown in FIG. 16B, the radial distribution of the
density of currents generated in the plasma showed a profile of the
relative magnitude relationship of the induced currents of the four
respective radial positions.
[0118] As described above, in the inductively coupled plasma
etching apparatus of the present embodiment, by providing variable
capacitors in the loops of the secondary coil 64 in the RF antenna
54 and changing the capacitances of the variable capacitors, it is
possible to control the radial distribution of the density of the
current excited in the plasma (i.e., the plasma density in the
plasma generated in the doughnut shape) and, furthermore, to
arbitrarily or multifariously control the radial distribution of
the plasma density at a portion close to the susceptor 12 (on the
semiconductor wafer W). Accordingly, it is possible to improve the
uniformity of the plasma density and, furthermore, the uniformity
of the plasma process even in the radial direction.
[0119] The inductively coupled plasma etching apparatus of the
present embodiment may be appropriately applied to the application
in which a multilayered film on the surface of a target substrate
is continuously etched at a plurality of steps.
[0120] Hereinafter, a multilayer resist method shown in FIGS. 17A
to 17D in accordance with another embodiment of the present
invention will be described.
[0121] As shown in FIGS. 17A to 17D, in a main surface of the
semiconductor wafer W serving as a target substrate to be
processed, an SiN layer 102 serving as a lowermost layer (final
mask) is formed on an original target film (e.g., a gate Si film)
to be processed. An organic film (e.g., carbon film) 104 serving as
an intermediate layer is formed on the SiN layer 102. A photoresist
108 serving as an uppermost layer is formed on the organic film 104
via a Si-containing bottom anti-reflective coating (BARC) film 106.
The SiN layer 102, the organic film 104 and the BARC film 106 are
formed by using the chemical vapor deposition (CVD) or the spin-on
coating method. The photoresist 108 is patterned by the
photolithography.
[0122] First, in a first etching process step, as shown in FIG.
17A, the Si-containing BARC film 106 is etched by using the
patterned photoresist 108 as a mask. In this case, a gaseous
mixture of CF.sub.4 and O.sub.2 is employed as an etching gas, and
the pressure inside the chamber 10 is set to be relatively low,
e.g., 10 mTorr.
[0123] Next, in a second etching process step, as shown in FIG.
17B, the organic film 104 is etched by using as a mask the
photoresist 108 and the BARC film. In this case, a single O.sub.2
gas is employed as an etching gas, and the pressure inside the
chamber 10 is set to be relatively lower, e.g., 5 mTorr.
[0124] Finally, in a third etching process step, as shown in FIGS.
17C and 17D, the SiN 102 is etched by using as a mask the patterned
BARC 106 and the organic film 104. In this case, a gaseous mixture
of CHF.sub.3, CF.sub.4, Ar and O.sub.2 is employed as an etching
gas, and the pressure inside the chamber 10 is set to be relatively
high, e.g., 50 mTorr.
[0125] In such multiple etching process steps, the process
conditions are entirely or partially (especially, the pressure in
the chamber 10) changed and, thus, the plasma generated in the
doughnut shape is diffused in another form in the processing space.
Here, in case that no secondary coil 64 is provided, the electron
density (plasma density) around the susceptor 12 in the first and
the second step (pressure of 10 mTorr or less) show a precipitous
mountain-shaped profile in which it has a relatively significantly
high value at the central portion. The electron density in the
third step (pressure of 50 mTorr) has a gentle mountain-shaped
profile in which it has a slightly high value at the central
portion.
[0126] In accordance with the present embodiment, in, e.g., a
process recipe, the capacitances of the capacitors 90(1) to 90(n)
(e.g., n=4) are set as one of the process parameters or recipe
information in order to add the capacitances into the typical
process conditions (the magnitude of the RF power, pressure, gas
type, gas flow rate and the like). Then, when the multiple etching
process steps are performed, the main control unit 74 reads out
data corresponding to the capacitances of the capacitors 90(1) to
90(n) from a memory and, at each step, sets the capacitances of the
capacitors 90(1) to 90(n) to preset (target) values.
[0127] Accordingly, in the etching process steps of the multilayer
resist method, the first step (10 mTorr), the second step (5 mTorr)
and the third step (50 mTorr) are respectively converted into the
first, the second and the third capacitance adjusting example.
[0128] As such, it is possible to variously control the
capacitances of the capacitors 90(1) to 90(n) depending on the
adjustment, the conversion and the change of the process conditions
during the single plasma process or the multiple plasma processes
of one semiconductor wafer W. Accordingly, it is possible to
improve the uniformity of the plasma process by multifariously or
optimally the radial distribution of a plasma density around the
susceptor 12 (on the semiconductor wafer W) through the entire
processing time or the entire steps of the single-wafer plasma
process.
[0129] FIG. 18 schematically shows a test example where the
secondary coil 64 of the RF antenna 54 is rotated in the
inductively coupled plasma etching apparatus of the present
embodiment. As described above, in case that the capacitors are
provided in the loops of the secondary coil 64, the asymmetric
property of the secondary coil 64 may become lost at the portions
where the capacitors are provided, and a bias may be generated in
the plasma density distribution in the circling direction.
[0130] In this case, by rotating the secondary coil 64 about its
central axis, it is possible to temporally make uniform the
electric variations generated in the loops of the secondary coil
64, to thereby improve the uniformity of the plasma density
distribution in the circling (azimuthal) direction. As described
above, since the secondary coil is formed of completely closed
loops without requiring the line connection to the outside, it is
possible to rotate the secondary coil 64 only or the secondary coil
64 and a supporting unit 110 only.
[0131] In FIG. 18, a rotating mechanism includes the supporting
unit 110 formed of a dielectric circular plate body; a rotation
ring 114 coupled to the supporting unit 110; a pulley or pinion
116; and a rotational driving unit 118 having a motor for rotating
the rotation ring 114 via the pinion 116.
[0132] The layout configuration of the secondary coil 64 is not
limited to the above-mentioned case where one or more endless coils
64(1), 64((2) . . . are concentrically arranged. For example, the
secondary coil 64 may have a series-connected single-wound or
multi-wound concentric coil, or a capacitor 120 provided in the
loop of the entire coil as shown in FIG. 19. Alternatively, the
secondary coil 64 may have a spiral shape, which is not shown.
[0133] Further, in case that the capacitor is provided in the loop
of the secondary coil 64, the series resonance may be easily
generated in the loop and, thus, a small Q value causes the series
resonance rapidly changed. This makes it difficult to control the
secondary coil 64 or causes discrepancy in each coil. Accordingly,
in order to prevent such disadvantage, it is preferable to use a
relatively high-resistivity metal or semiconductor (e.g., silicon
crystal doped with N or P to have conductivity, or the like) as a
material of the secondary coil 64. Alternatively, in addition to
the capacitor, a resistor may be provided. In the meanwhile, it is
known that the resistivity of the resistor inserted into the loop
of the secondary coil 64 from the outside or the resistivity of the
coil body is increased as the temperature is increased. In case
that the regular RF power RF.sub.H is supplied to the RF antenna
54, the amount of the RF power RF.sub.H consumed is increased as
the resistivity of the secondary coil 64 is increased. Resultantly,
it is expected that the amount of the current flowing to the
primary coil 62 is decreased. Accordingly, it is possible to
prevent a significantly large current from flowing to one coil.
Further, it can be expected that the current flowing in the RF
antenna 54 is automatically made uniform.
[0134] Besides, it is preferable to cool the RF antenna 54,
especially the secondary coil 64, by using an air-cooling method or
a water-cooling method. As such, in the case of cooling the coil
64(62), by changing the cooling temperature, it is possible to
adjust the resistivity of the coil 64(62), to thereby control the
current flowing in the coil 64(62).
[0135] Meanwhile, the shape of the loops of the primary coil 62 and
the secondary coil 64 included in the RF antenna 54 is not limited
to the circular shape. The loops thereof may have a quadrangular
shape, a hexagonal shape or the like. The cross sectional shapes of
the primary coil 62 and the secondary coil 64 are also not limited
to the rectangle. The cross sectional shapes may have a circular
shape, an elliptical shape or the like. Further, instead of the
single wire, the twisted wire may be employed.
[0136] In the aforementioned embodiments of the present invention,
the configuration of the inductively coupled plasma etching
apparatus is merely an example. Various modifications of the units
of the plasma-generation mechanism and units having no direct
involvement in the plasma generation may be made.
[0137] For example, the RF antenna 54 may have various outer shapes
such as a domical shape instead of the planar outer shape.
Moreover, a processing gas may be supplied through the ceiling of
the chamber 10 from the processing gas supply unit, and no DC bias
controlling RF power RF.sub.L may be supplied to the susceptor
12.
[0138] In the above embodiments, the inductively coupled plasma
processing apparatus or the plasma processing method therefor is
not limited to the technical field of the plasma etching, but is
applicable to other plasma processes such as a plasma CVD process,
a plasma oxidizing process, a plasma nitriding process and the
like. In the embodiments, the target substrate to be processed is
not limited to the semiconductor wafer. For example, the target
substrate may be one of various kinds of substrates, which can be
used in a flat panel display (FPD), a photomask, a CD substrate, a
print substrate or the like.
[0139] In accordance with the present invention, it is possible to
provide an inductively coupled plasma processing apparatus and a
plasma processing method therefor, capable of improving the
uniformity and controllability of plasma density distribution, with
a simple configuration of its RF antenna that can easily be
manufactured, since loads of its RF power supply system become
small by the above-mentioned configurations and operations.
[0140] While the invention has been shown and described with
respect to the embodiments, it will be understood by those skilled
in the art that various changes and modifications may be made
without departing from the scope of the invention as defined in the
following claims.
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