U.S. patent application number 11/296209 was filed with the patent office on 2006-06-15 for gas supply unit, substrate processing apparatus, and supply gas setting method.
This patent application is currently assigned to Tokyo Electron Limited. Invention is credited to Keiki Ito, Masahide Itoh, Kenetsu Mizusawa.
Application Number | 20060124169 11/296209 |
Document ID | / |
Family ID | 36582387 |
Filed Date | 2006-06-15 |
United States Patent
Application |
20060124169 |
Kind Code |
A1 |
Mizusawa; Kenetsu ; et
al. |
June 15, 2006 |
Gas supply unit, substrate processing apparatus, and supply gas
setting method
Abstract
A gas supply unit, for supplying a gas into a processing chamber
in which a substrate is processed, includes a plurality of gas
supply sources, a mixing line for mixing a plurality of gases
supplied from the gas supply sources to make a gaseous mixture, a
multiplicity of branch lines for branching the gaseous mixture to
be supplied to a multiplicity of places in the processing chamber,
and an additional gas supply unit for supplying a specified
additional gas to a gaseous mixture flowing in at least one branch
line. The gas supply unit also includes pressure gauges and valves
for adjusting gas flow rates in the branch lines, respectively, and
a pressure ratio controller for controlling that gaseous mixtures
branched into the branch lines to have a specified pressure ratio
by adjusting opening degrees of the valves based on measurement
results obtained by using the pressure gauges.
Inventors: |
Mizusawa; Kenetsu;
(Nirasaki-shi, JP) ; Ito; Keiki; (Nirasaki-shi,
JP) ; Itoh; Masahide; (Nirasaki-shi, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
Tokyo Electron Limited
Tokyo
JP
|
Family ID: |
36582387 |
Appl. No.: |
11/296209 |
Filed: |
December 8, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60639795 |
Dec 29, 2004 |
|
|
|
Current U.S.
Class: |
137/7 ;
137/87.01 |
Current CPC
Class: |
H01J 37/32449 20130101;
F17D 1/04 20130101; H01J 37/3244 20130101; Y10T 137/0352 20150401;
H01L 21/67253 20130101; G05D 11/132 20130101; C23C 16/45561
20130101; C23C 16/52 20130101; Y10T 137/2496 20150401; Y10T
137/87346 20150401; Y10T 137/0329 20150401; Y10T 137/0335 20150401;
H01L 21/67069 20130101; C23C 16/45512 20130101 |
Class at
Publication: |
137/007 ;
137/087.01 |
International
Class: |
E03B 1/00 20060101
E03B001/00; G05D 11/00 20060101 G05D011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 9, 2004 |
JP |
2004-357292 |
Claims
1. A gas supply unit for supplying a gas into a processing chamber
in which a substrate is processed, the gas supply unit comprising:
a plurality of gas supply sources; a mixing line for mixing a
plurality of gases supplied from the gas supply sources to make a
gaseous mixture; a multiplicity of branch lines for branching the
gaseous mixture to be supplied to a multiplicity of places in the
processing chamber; and an additional gas supply unit for supplying
a specified additional gas to a gaseous mixture flowing in at least
one branch line.
2. The gas supply unit of claim 1, further comprising pressure
gauges and valves for adjusting gas flow rates in the branch lines,
respectively, and a pressure ratio controller for controlling that
gaseous mixtures branched into the branch lines to have a specified
pressure ratio by adjusting opening degrees of the valves based on
measurement results obtained by using the pressure gauges.
3. The gas supply unit of claim 2, wherein the additional gas
supply unit includes an additional gas supply line which
communicates with said at least one branch line, and the additional
gas supply line is connected to a downstream side of the pressure
gauges and the valves.
4. The gas supply unit of claim 3, wherein the pressure ratio
controller controls that a pressure ratio of the gaseous mixtures
branched into the branch lines becomes a specified pressure ratio
by adjusting the valves under a condition in which the additional
gas is not supplied to said at least one branch line from the
additional gas supply unit, and opening degrees of the valves are
fixed to values obtained under the condition.
5. The gas supply unit of claim 4, further comprising a controller
for supplying the additional gas to said at least one branch line
from the additional gas supply unit after the gaseous mixtures
branched into the branch lines are controlled to have a specified
pressure ratio by the pressure ratio controller.
6. A substrate processing apparatus, comprising: a processing
chamber accommodating therein a substrate; a plurality of gas
supply sources; a mixing line for mixing a plurality of gases
supplied from the gas supply sources to make a gaseous mixture; a
multiplicity of branch lines for branching the gaseous mixture to
be supplied to a multiplicity of places in the processing chamber;
and an additional gas supply unit for supplying a specified
additional gas to a gaseous mixture flowing in at least one branch
line.
7. The substrate processing apparatus of claim 6, further
comprising pressure gauges and valves for adjusting gas flow rates
in the branch lines, respectively, and a pressure ratio controller
for controlling that gaseous mixtures branched into the branch
lines to have a specified pressure ratio by adjusting opening
degrees of the valves based on measurement results obtained by
using the pressure gauges.
8. The substrate processing apparatus of claim 7, wherein the
additional gas supply unit includes an additional gas supply line
which communicates with said at least one branch line, and the
additional gas supply line is connected to a downstream side of the
pressure gauges and the valves.
9. The substrate processing apparatus of claim 8, wherein the
pressure ratio controller controls that a pressure ratio of the
gaseous mixtures branched into the branch lines becomes a specified
pressure ratio by adjusting the valves under a condition in which
the additional gas is not supplied to said at least one branch line
from the additional gas supply unit, and opening degrees of the
valves are fixed to values obtained under the condition.
10. The substrate processing apparatus of claim 9, further
comprising a controller for supplying the additional gas to said at
least one branch line from the additional gas supply unit after the
gaseous mixtures branched into the branch lines are controlled to
have a specified pressure ratio by the pressure ratio
controller.
11. The substrate processing apparatus of claim 6, further
comprising a shower head, disposed in the processing chamber, for
discharging the gaseous mixture into a processing space in the
processing chamber, wherein the branch lines are connected to the
shower head.
12. The substrate processing apparatus of claim 11, wherein the
number of the branch lines is two and the two branch lines are
respectively connected to a first and a second buffer space which
are concentrically defined in the shower head.
13. The substrate processing apparatus of claim 12, wherein the
first and the second buffer space are respectively disposed at an
inner portion and an outer portion in the shower head, and said at
least one branch line connected to the additional gas supply unit
is connected to the second buffer space.
14. A supply gas setting method using the gas supply unit which
includes: a plurality of gas supply sources; a mixing line for
mixing a plurality of gases supplied from the gas supply sources to
make a gaseous mixture; a multiplicity of branch lines for
branching the gaseous mixture to be supplied to a multiplicity of
places in the processing chamber; an additional gas supply unit for
supplying a specified additional gas to a gaseous mixture flowing
in at least one branch line; and valves and pressure gauges for
adjusting gas flow rates in the branch lines, respectively, the
method comprising the following sequential steps of: controlling a
pressure ratio of the gaseous mixtures branched into the branch
lines to be a specified pressure ratio by adjusting the valves
under a condition in which the additional gas is not supplied to
said at least one branch line from the additional gas supply unit
and, then, fixing opening degrees of the valves of the branch lines
to values obtained under the condition; and supplying an additional
gas of a specified flow rate to said at least one branch line from
the additional gas supply unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS:
[0001] This document claims priority to Japanese Patent Application
Number 2004-357292, filed Dec. 9, 2004 and U.S. Provisional
Application No. 60/639,795, filed Dec. 29, 2004, the entire content
of which are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a gas supply unit for
supplying a gas to a processing chamber, a substrate processing
apparatus connected to the gas supply unit and a supply gas setting
method.
BACKGROUND OF THE INVENTION
[0003] In a manufacturing process of an electric device such as a
semiconductor device or a liquid crystal display device, there are
performed a film forming process for forming a conductive film or
an insulating film on the surface of a substrate, an etching
process for etching a film formed on the substrate and the
like.
[0004] For example, a plasma etching apparatus is widely employed
in the etching process, wherein the plasma etching apparatus
includes a processing chamber for accommodating therein a
substrate. In the processing chamber, there are installed a lower
electrode for mounting the substrate thereon and a shower head,
also serving as an upper electrode, for injecting a gas onto the
substrate mounted on the lower electrode. In the etching process,
while a specified gaseous mixture is injected through the shower
head, a radio frequency power is applied between the electrodes.
Accordingly, a plasma is generated in the processing chamber and a
film formed on the substrate is etched by the plasma.
[0005] However, etching characteristics such as an etching rate and
an etching selectivity are influenced by a concentration of a gas
supplied onto the substrate. Further, conventionally, it has been a
major challenge to improve a uniformity of etching in the surface
of the substrate by making the etching characteristics uniform on
the surface of the substrate. Thus, there is proposed a technique
of dividing an inner space of the shower head into a plurality of
gas chambers, wherein each gas chamber is independently connected
to an individual gas introduction line such that a gaseous mixture
containing gases whose kinds and flow rates are optionally chosen
based on the necessity can be supplied to each portion in the
surface of the substrate (see, e.g., Reference 1). Consequently, a
partial gas concentration on a small part in the surface of the
substrate can be locally controlled to thereby improve an etching
uniformity on the surface of the substrate.
[0006] However, the gaseous mixture for use in the etching process
contains various gases, for example, an etching gas, a gas for
controlling deposits of reaction products, a carrier gas such as an
inert gas, that are chosen depending on a material to be etched,
process conditions and the like. Accordingly, for example, when an
inner space of the shower head is divided into a plurality of gas
chambers and a gas introduction line is independently connected to
each of the gas chambers, as shown in FIG. 1 of Reference 2, each
gas introduction line is connected to lines communicating with
multiple gas supply sources and, further, a mass flow controller is
provided in each line. Thus, a piping structure of a gas supply
system becomes complicated and a control of gas flow rate is also
complicated in each line. Therefore, for example, a large piping
space is required, which in turn increases the expense of an
apparatus control system.
[0007] [Reference 1] Japanese Patent Laid-open Application No.
8-158072
[0008] [Reference 2] Japanese Patent Laid-open Application No.
9-45624
SUMMARY OF THE INVENTION
[0009] The present invention has been conceived from the above
drawbacks; and it is, therefore, an object of the present invention
to provide a gas supply unit capable of realizing a simple piping
configuration when supplying optional gaseous mixtures to a
plurality of places in a processing chamber in a substrate
processing apparatus such as an etching apparatus, a substrate
processing apparatus including a processing chamber connected to
the gas supply unit and a supply gas setting method employing the
gas supply unit.
[0010] To achieve the object, in accordance with one aspect of the
present invention, there is provided a gas supply unit for
supplying a gas into a processing chamber in which a substrate is
processed, the gas supply unit including a plurality of gas supply
sources; a mixing line for mixing a plurality of gases supplied
from the gas supply sources to make a gaseous mixture; a
multiplicity of branch lines for branching the gaseous mixture to
be supplied to a multiplicity of places in the processing chamber;
and an additional gas supply unit for supplying a specified
additional gas to a gaseous mixture flowing in at least one branch
line.
[0011] In accordance with the present invention, gases from a
plurality of the gas supply sources are mixed in the mixing line to
be branched into a multiplicity of the branch lines. Further, a
specified additional gas is added to a specific branch line to
adjust components or their flow rates in the gaseous mixture. In a
branch line without being supplied with the additional gas, the
gaseous mixture from the mixing line is supplied to the processing
chamber as it is. In this case, a gaseous mixture containing common
components is produced in, e.g., the mixing line and components and
their flow rates in the gaseous mixture are adjusted in each branch
line when necessary. Thus, the number of lines needed is minimized.
As a result, optional gaseous mixtures are supplied to a plurality
of places in the processing chamber by a simple piping
configuration.
[0012] The gas supply unit may include pressure gauges and valves
for adjusting gas flow rates in the branch lines, respectively, and
a pressure ratio controller for controlling that gaseous mixtures
branched into the branch lines to have a specified pressure ratio
by adjusting opening degrees of the valves based on measurement
results obtained by using the pressure gauges. In this case, since
the flow rate in the branch line is controlled on the basis of a
pressure ratio (partial pressure ratio), for example, even though a
pressure in the branch line is low, the flow rate in the branch
line can be adequately controlled.
[0013] In accordance with another aspect of the present invention,
there is provided a substrate processing apparatus, including a
processing chamber accommodating therein a substrate; a plurality
of gas supply sources; a mixing line for mixing a plurality of
gases supplied from the gas supply sources to make a gaseous
mixture; a multiplicity of branch lines for branching the gaseous
mixture to be supplied to a multiplicity of places in the
processing chamber; and an additional gas supply unit for supplying
a specified additional gas to a gaseous mixture flowing in at least
one branch line.
[0014] In accordance with still another aspect of the present
invention, there is provided a supply gas setting method using the
gas supply unit which includes a plurality of gas supply sources; a
mixing line for mixing a plurality of gases supplied from the gas
supply sources to make a gaseous mixture; a multiplicity of branch
lines for branching the gaseous mixture to be supplied to a
multiplicity of places in the processing chamber; an additional gas
supply unit for supplying a specified additional gas to a gaseous
mixture flowing in at least one branch line; and valves and
pressure gauges for adjusting gas flow rates in the branch lines,
respectively, the method including the following sequential steps
of controlling a pressure ratio of the gaseous mixtures branched
into the branch lines to be a specified pressure ratio by adjusting
the valves under a condition in which the additional gas is not
supplied to said at least one branch line from the additional gas
supply unit and, then, fixing opening degrees of the valves of the
branch lines to values obtained under the condition; and supplying
an additional gas of a specified flow rate to said at least one
branch line from the additional gas supply unit.
[0015] In accordance with the present invention, a piping space and
a cost of controlling flow rates can be reduced by a simple piping
configuration.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The above and other objects and features of the present
invention will become apparent from the following description of
preferred embodiments given in conjunction with the accompanying
drawings, in which:
[0017] FIG. 1 is a longitudinal sectional view showing a schematic
configuration of a plasma etching apparatus;
[0018] FIG. 2 shows a cross sectional view of an inner upper
electrode;
[0019] FIG. 3 explains a schematic configuration of a gas supply
unit;
[0020] FIG. 4 is a flowchart for setting a supply gas;
[0021] FIG. 5 shows a schematic configuration of a gas supply unit
for supplying gaseous mixtures to three places in a processing
chamber; and
[0022] FIG. 6 shows a schematic configuration of a gas supply unit
for supplying a gaseous mixture from a side surface portion of a
processing chamber.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] Hereinafter, a preferred embodiment of the present invention
will be described. FIG. 1 is a longitudinal sectional view showing
a schematic configuration of a plasma etching apparatus 1 serving
as a substrate processing apparatus including a gas supply unit in
accordance with the preferred embodiment of the present
invention.
[0024] The plasma etching apparatus 1 is a capacitively coupled
plasma etching apparatus having a parallel plate type electrode
structure. The plasma etching apparatus 1 includes an approximately
cylindrical processing chamber 10 that is grounded. The processing
chamber 10 is formed of, e.g., aluminum alloy and the inner wall
surface thereof is covered by an alumina film or an yttrium oxide
film.
[0025] A cylindrical susceptor supporting table 14 is disposed in a
central bottom portion of the processing chamber 10 via an
insulating plate 12. A susceptor 16, serving as a mounting table,
for mounting thereon a wafer W, i.e., a substrate, is disposed on
the susceptor supporting table 14. Further, the susceptor 16 also
serves as a lower electrode of the parallel plate type electrode
structure and is formed of, e.g., aluminum alloy.
[0026] An electrostatic chuck 18 for holding the wafer. W is
disposed on the susceptor 16, and the electrostatic chuck 18 has an
electrode 20 therein. A DC power supply 22 is electrically
connected to the electrode 20. The wafer W can be adsorbed on the
top surface of the susceptor 16 by Coulomb force generated by a DC
voltage applied to the electrode 20 from the DC power supply
22.
[0027] A focus ring 24 is disposed on the susceptor 16 to surround
the electrostatic chuck 18. A cylindrical inner wall member 26
formed of, e.g., quartz is attached to an outer peripheral surface
of the susceptor 16 and the susceptor supporting table 14.
[0028] An annular coolant chamber 28 is formed inside the susceptor
supporting table 14. The coolant chamber 28 communicates with a
chiller unit (not shown) installed outside the processing chamber
10 via lines 30a and 30b. A coolant or cooling water is supplied
into the coolant chamber 28 through the lines 30a and 30b to be
circulated therein, thereby controlling the temperature of the
wafer W on the susceptor 16. A gas supply line 32 passing through
the susceptor 16 and the susceptor supporting table 14 reaches a
top surface of the electrostatic chuck 18, whereby a thermally
conductive gas such as He gas can be supplied between the wafer W
and the electrostatic chuck 18.
[0029] An upper electrode 34 is disposed above the susceptor 16 to
face it in parallel. A plasma generation space PS is formed between
the susceptor 16 and the upper electrode 34.
[0030] The upper electrode 34 includes an annular outer upper
electrode 36 and an inner upper electrode 38 of a circular plate
that is disposed inwardly from the outer upper electrode 36. An
annular dielectric material 42 is interposed between the outer
upper electrode 36 and the inner upper electrode 38. An annular
insulating shield member 44 formed of, e.g., alumina is airtightly
interposed between the outer upper electrode 36 and an inner
peripheral wall of the processing chamber 10.
[0031] A first radio frequency power supply 54 is electrically
connected to the outer upper electrode 36 via a matching unit 46,
an upper power supply rod 48, a connector 50 and a power supply
case 52. The first radio frequency power supply 54 can output a
radio frequency voltage having a frequency equal to or larger than
40 MHz, e.g., a frequency of 60 MHz.
[0032] The power supply case 52 is shaped like, for example, a
cylinder with its bottom surface removed. A lower end portion of
the power supply case 52 is connected to the outer upper electrode
36. A central portion of the top surface of the power supply case
52 is electrically connected to a lower end portion of the upper
power supply rod 48 via the connector 50. An upper end portion of
the upper power supply rod 48 is connected to an output side of the
matching unit 46. The matching unit 46 is connected to the first
radio frequency power supply 54, thereby matching an inner
impedance of the first radio frequency power supply 54 with a load
impedance. The power supply case 52 is surrounded by a cylindrical
ground conductor 10a whose sidewall has a same diameter as a
sidewall of the processing chamber 10. A lower end portion of the
ground conductor 10a is connected to an upper portion of the
sidewall of the processing chamber 10. The upper power supply rod
48 passes through a central portion of the top surface of the
ground conductor 10a, and an insulation member 56 is interposed in
a portion where the upper power supply rod 48 is in contact with
the ground conductor 10a.
[0033] The inner upper electrode 38 functions as a shower head for
injecting a specified gaseous mixture toward the wafer W mounted on
the susceptor 16. The inner upper electrode 38 includes a circular
electrode plate 60 having a plurality of gas injection openings 60a
and an electrode supporting member 62 capable of supporting the
electrode plate 60 by being attached to or detached from the top
surface of the electrode plate 60. The electrode supporting member
62 is shaped as a disc having a same diameter as the electrode
plate 60, and a circular buffer space 63 is formed inside the
electrode supporting member 62. In the buffer space 63, for
example, as shown in FIG. 2, an annular partition member 64 formed
of an O-ring is disposed, whereby the buffer space 63 is divided
into a first buffer space 63a of a central side and a second buffer
space 63b of an outer peripheral side. The first and the second
buffer space 63a and 63b face a central portion and an outer
peripheral portion of the wafer W loaded on the susceptor 16,
respectively. The gas injection openings 60a are formed in the
bottom surfaces of the buffer spaces 63a and 63b to communicate
with the plasma generation space, whereby specified gaseous
mixtures can be injected through the first and second buffer spaces
63a and 63b toward the central portion and the outer peripheral
portion of the wafer W, respectively. Further, a gas supply unit
100 for supplying a specified gaseous mixture to each chamber in
the buffer space 63 will be described later.
[0034] As depicted in FIG. 1, a lower power supply case 70 coupled
to the upper power supply rod 48 is electrically connected to the
top surface of the electrode supporting member 62. A variable
condenser 72 is installed in the lower power supply case 70. The
variable condenser 72 can adjust a relative ratio between an
intensity of an electric field formed right under the outer upper
electrode 36 and that formed right under the inner upper electrode
38, which are generated by a radio frequency voltage from the first
radio frequency power supply 54.
[0035] A gas exhaust port 74 is formed in a bottom portion of the
processing chamber 10. The gas exhaust port 74 is connected to the
gas exhaust unit 78 including a vacuum pump and the like via a gas
exhaust pipe 76. The processing chamber 10 can be depressurized to
a desired vacuum level by using the gas exhaust unit 78.
[0036] A second radio frequency power supply 82 is electrically
connected to the susceptor 16 via a matching unit 80. The second
radio frequency power supply 82 can output a radio frequency
voltage having a frequency ranging from, e.g., 2 MHz to 20 MHz, for
example, a frequency of 20 MHz.
[0037] Electrically connected to the inner upper electrode 38 is a
low pass filter 84 for passing a radio frequency wave generated
from the second radio frequency power supply 82 to ground by
shielding a radio frequency wave generated from the first radio
frequency power supply 54. Electrically connected to the susceptor
16 is a high pass filter 86 for passing a radio frequency wave
generated from the first radio frequency power supply 54 to
ground.
[0038] The plasma etching apparatus 1 includes an apparatus
controller 90 for controlling operations of various components such
as the DC power supply 22, the first radio frequency power supply
54 and the second radio frequency power supply 82 to perform an
etching.
[0039] Hereinafter, a gas supply unit 100 for supplying gaseous
mixtures to the inner upper electrode 38 in the plasma etching
apparatus 1 will be described.
[0040] The gas supply unit 100, as shown in FIG. 3, includes a
first gas box 111 accommodating plural, e.g., three, gas supply
sources 110a, 110b and 110c and a second gas box 113 accommodating
plural, e.g., two, additional gas supply sources 112a and 112b. In
this embodiment, for instance, the gas supply source 110a is sealed
to contain therein fluorocarbon-based fluorine compound serving as
an etching gas such as C.sub.xF.sub.y gas (e.g., CF.sub.4,
C.sub.4F.sub.6, C.sub.4F.sub.8 and C.sub.5F.sub.8); the gas supply
source 110b is sealed to contain therein a gas for controlling
deposits of CF-based reaction products, e.g., O.sub.2 gas; and the
gas supply source 110c is sealed to contain therein a rare gas
serving as a carrier gas, e.g., an Ar gas. Further, the additional
gas supply source 112a is sealed to contain therein, e.g.,
C.sub.xF.sub.y gas capable of accelerating an etching, and the
additional gas supply source 112b is sealed to contain therein,
e.g., O.sub.2 gas capable of controlling deposits of CF-based
reaction products.
[0041] A mixing line 120 in which various gases from the gas supply
sources 110a, 110b and 110c are combined to be mixed is connected
to each of the gas supply sources 110a, 110b and 110c of the first
gas box 111. In the mixing line 120, mass flow controllers 121 are
installed for the gas supply sources 110a to 110c, respectively, to
control flow rates of gases supplied from the gas supply sources
110a to 110c. The mixing line 120 is coupled to a first branch line
122 and a second branch line 123 for branching a gaseous mixture
that is mixed in the mixing line 120. The first branch line 122 is
connected to the first buffer space 63a in the inner upper
electrode 38 of the processing chamber 10. The second branch line
123 is connected to the second buffer space 63b in the inner upper
electrode 38.
[0042] A pressure control unit 124 is installed in the first branch
line 122. In the same manner, a pressure control unit 125 is
installed in the second branch line 123. The pressure control unit
124 is provided with a pressure gauge 124a and a valve 124b.
Similarly, the pressure control unit 125 is provided with a
pressure gauge 125a and a valve 125b. Measurement results
respectively obtained by the pressure gauges 124a and 125a of the
pressure control units 124 and 125 can be outputted to a pressure
ratio controller 126. The pressure ratio controller 126 can control
a pressure ratio, i.e., a flow rate ratio of gaseous mixtures
branched into the first branch line 122 and the second branch line
123 by adjusting respective opening degrees of the valves 124b and
125b based on the measurement results obtained by using the
pressure gauges 124a and 125a. Further, when setting a supply gas,
while an additional gas is not supplied to the second branch line
123 from a second gas box 113 which will be described later, the
pressure ratio controller 126 controls a pressure ratio of the
gaseous mixtures flowing in the first branch line 122 and the
second branch line 123 to be a target pressure ratio and fixes
respective opening degrees of the valves 124b and 125b to values
obtained under this condition.
[0043] An additional gas supply line 130 communicating with, e.g.,
the second branch line 123 is connected to each of additional gas
supply sources 112a and 112b of the second gas box 113. For
example, respective lines of the additional gas supply line 130
connected to the additional gas supply sources 112a and 112b are
combined in the middle thereof and then connected to the second
branch line 123. The additional gas supply line 130 is connected to
a downstream side of the pressure control unit 125. In the
additional gas supply line 130, mass flow controllers 131 are
installed for the additional gas supply sources 112a and 112b,
respectively, to control flow rates of additional gases supplied
from the additional gas supply sources 112a and 112b. In this
configuration, an additional gas that is chosen among gases from
the second gas box 113 or obtained by mixing the gases can be
supplied to the second branch line 123. Further, in this
embodiment, an additional gas supply unit includes the second gas
box 113, the additional gas supply sources 112a and 112b, the
additional gas supply line 130 and the mass flow controller
131.
[0044] The operations of the mass flow controllers 121 in the first
gas box 111 and the mass flow controllers 131 in the second gas box
113 are controlled by, e.g., the apparatus controller 90 of the
plasma etching apparatus 1. Thus, various gases from the first gas
box 111 and the second gas box 113 can be started or stopped to be
supplied under the control of the apparatus controller 90 which
also controls respective flow rates thereof.
[0045] Hereinafter, operations of the gas supply unit 100 having
the above-mentioned configuration will be described. FIG. 4 is a
flowchart for setting components or their flow rates in gaseous
mixtures to be supplied into the processing chamber 10. First, a
preset gas in the first gas box 111 flows at a specified flow rate
in the mixing line 120 based on instruction signals of the
apparatus controller 90 (step S1 in FIG. 4). For example, the
C.sub.xF.sub.y gas, O.sub.2 gas and Ar gas, which are supplied at
specified flow rates from the gas supply sources 110a to 110c,
respectively, are mixed in the mixing line 120, thereby producing a
gaseous mixture containing C.sub.xF.sub.y gas, O.sub.2 gas and Ar
gas having a specified mixing ratio. Subsequently, the pressure
ratio controller 126 controls opening degrees of the valves 124b
and 125b based on the measurement results obtained by the pressure
gauges 124a and 125a, whereby a pressure ratio of gaseous mixtures
respectively flowing in the first branch line 122 and the second
branch line 123 is adjusted to be a target pressure ratio (step S2
in FIG. 4). Accordingly, the components (mixing ratio) and their
flow rates in the gaseous mixture supplied into the first buffer
space 63a through the first branch line 122 are set. Further, at
this time, at least, the same gas as the gaseous mixture supplied
to the first buffer space 63a, i.e., a gaseous mixture for etching,
is supplied into the second buffer space 63b through the second
branch line 123.
[0046] Then, when the gaseous mixtures respectively flowing in the
first branch line 122 and the second branch line 123 are controlled
to have the target pressure ratio to be stable, the opening degrees
of the valves 124b and 125b of the pressure control units 124 and
125 are fixed by the pressure ratio controller 126 (step S3 in FIG.
4). By an instruction signal from the apparatus controller 90 after
respective opening degrees of the valves 124b and 125b being fixed,
a preset additional gas in the second gas box 113 flows at a
specified flow rate in the additional gas supply line 130 (step S4
in FIG. 4). An instruction signal for starting the supply of the
additional gas from the second gas box 113 is sent after a setting
time that is set in advance in the apparatus controller 90 elapses.
The C.sub.xF.sub.y gas, e.g., CF.sub.4 gas, capable of accelerating
an etching is supplied at a specified flow rate from, e.g., the
additional gas supply source 112a to flow through the additional
gas supply line 130 which is combined with the second branch line
123. Accordingly, the second buffer space 63b communicating with
the second branch line 123 is supplied with a gaseous mixture
containing a larger amount of CF.sub.4 gas than the gaseous mixture
supplied to the first buffer space 63a. In this manner, the
components and their flow rates in the gaseous mixture supplied
into the second buffer space 63b are set. Further, although the
pressure ratio between the pressure in the first branch line 122
and that in the second branch line 123 is changed by supplying the
additional gas into the second branch line 123, a gaseous mixture
having an original flow rate is supplied into the first buffer
space 63a because the valves 124b and 125b are fixed.
[0047] Further, in the plasma etching apparatus 1 having therein a
depressurized atmosphere, the gaseous mixture from the first buffer
space 63a is supplied to the central portion of the wafer W on the
susceptor 16 and the gaseous mixture containing plenty of CF.sub.4
gas from the second buffer space 63b is supplied to the outer
peripheral portion of the wafer W. Accordingly, the etching
characteristics of the outer peripheral portion of the wafer W are
adjusted relatively to those of the central portion of the wafer W,
thereby achieving uniform etching characteristics on the surface of
the wafer W.
[0048] In accordance with the preferred embodiment, plural kinds of
gases from the first gas box are mixed to make a gaseous mixture in
the mixing line 120 and, then, the gaseous mixture are branched
into the first branch line 122 and the second branch line 123,
which are supplied into the first and the second buffer space 63a
and 63b of the processing chamber 10, respectively. The additional
gas for adjusting the etching characteristics is supplied to the
second branch line 123, and the second buffer space 63b is supplied
with a gaseous mixture having components and flow rates different
from those in the first buffer space 63a. Therefore, components and
their flow rates in gaseous mixtures supplied into the first and
the second buffer space 63a and 63b can be optionally adjusted by a
simple piping configuration.
[0049] Further, since flow rates in the first and the second branch
line 122 and 123 are respectively adjusted by the pressure control
units 124 and 125, even if the pressure of the gas supply source is
very low as in the plasma etching apparatus 1, gas flow rates in
supply lines can be adequately adjusted.
[0050] In the preferred embodiment, CF.sub.4 gas is supplied into
the second branch line 123 to accelerate an etching. However, for
example, when a deposit amount of CF-based reaction products is
large and an etching rate is slow in the outer peripheral portion
of the wafer W compared to that of the central portion thereof,
O.sub.2 gas may be supplied to the second branch line 123 to remove
CF-based reaction products. Further, it is possible to feed a
gaseous mixture containing CF.sub.4 gas and O.sub.2 gas having a
specified mixing ratio into the second branch line 123.
[0051] A timing of supplying the additional gas from the second gas
box 113 to the second branch line 123 is preset based on the
setting time of the apparatus controller 90 in the preferred
embodiment. However, it is also possible to start supplying the
additional gas in the manner that the apparatus controller 90
monitors the measurement results obtained by the pressure gauges
124a and 125a via the pressure ratio controller 126 and sends an
instruction signal to the second gas box 113 when a stable, desired
target pressure ratio is achieved.
[0052] Further, the additional gas supply sources 112a and 112b of
the second gas box 113 may be connected to the first branch line
122 via the additional gas supply line 130. By doing this,
components or flow rates in the gaseous mixture supplied to the
first buffer space 63 can be minutely controlled when
necessary.
[0053] Although the additional gas supply sources for supplying
CF.sub.4 gas and O.sub.2 gas are installed in the second gas box
113 in the preferred embodiment, additional gas supply sources may
supply other additional gases capable of accelerating or
suppressing an etching, e.g., C.sub.xH.sub.yF.sub.z gas such as
CHF.sub.3, CH.sub.2F.sub.2, CH.sub.3F for accelerating an etching,
N.sub.2 gas or CO gas for controlling CF-based reaction products,
Xe gas or He gas for a dilution gas and the like. Besides, the
number or kinds of gases accommodated in the first and the second
gas box 111 and 113 can be optionally chosen depending on a
material to be etched, process conditions and the like.
[0054] The gas supply unit 100 supplies gaseous mixtures to two
places, i.e., the first and the second buffer space 63a and 63b, in
the processing chamber 10 in the preferred embodiment, but gaseous
mixtures may be supplied to three places or more in the processing
chamber 10. FIG. 5 shows such an example, wherein the inner upper
electrode 38 includes a buffer space 63 having three buffer spaces
concentrically disposed. That is, an annular third buffer space 63c
is formed further outside the second buffer space 63b of the inner
upper electrode 38. In this case, the mixing line 120 is branched
into the first and the second branch line 122 and 123 and, further,
a third branch line 150. The third branch line 150 is connected to
the third buffer space 63c. Similarly to the branch lines 122 and
123, the third branch lime 150 is provided with a pressure control
unit 151, a pressure gauge 151a and a valve 151b. Further, the gas
supply unit 100 in this example is provided with a third gas box
152 for supplying a specified additional gas to the third branch
line 150. For example, the third gas box 152 has a same
configuration as the second gas box 113 and includes an additional
gas supply source 153a of CF.sub.4 gas and an additional gas supply
source 153b of O.sub.2 gas. Both of the additional gas supply
sources 153a and 153b are connected to the third branch line 150
via an additional gas supply line 154. Provided in the additional
gas supply line 154 are mass flow controllers 155 for the
additional gas supply sources 153a and 153b, respectively. Further,
the other configuration is same as in the above-mentioned preferred
embodiment and, thus, the description thereof will be omitted.
[0055] Further, when gaseous mixtures are respectively supplied
into the buffer spaces 63a to 63c, gases from, e.g., the gas supply
sources 110a to 110c of the first gas box 111 are supplied into the
mixing line 120 to be mixed therein, thereby producing a gaseous
mixture. The gaseous mixture is branched into three branch lines
122, 123 and 150. The gas pressure ratio of the branch lines 122,
123 and 150 is adjusted to be a specified target pressure ratio by
the pressure ratio controller 126 and, then, opening degrees of the
valves 124b, 125b and 151b are fixed. Accordingly, components and
their flow rates in the gaseous mixture to be supplied to the first
buffer space 63a communicating with the first branch line 122 are
set. Thereafter, an additional gas of a specified kind is supplied
at a specified flow rate into the second branch line 123 from the
second gas box 113 via the additional gas supply line 130. Further,
an additional gas of a specified kind is supplied at a specified
flow rate into the third branch line 150 from the third gas box 152
via the additional gas supply line 154. Accordingly, the components
and flow rates in the gaseous mixtures supplied into the second and
the third buffer space 63b and 63c are set. Also in this case,
optional gaseous mixtures can be supplied into three places in the
processing chamber 10 by a simple piping configuration.
[0056] In the preferred embodiment, the gaseous mixtures supplied
from the gas supply unit 100 are injected toward the wafer W
through an upper portion of the processing chamber 10. However, the
gaseous mixtures may be injected through another portion of the
processing chamber 10, e.g., a side surface portion of the plasma
generation space PS in the processing chamber 10. In such a case,
for example, as shown in FIG. 6, the third branch line 150 is
connected to both side surfaces of the processing chamber 10 and
the gaseous mixtures are injected into the plasma generation space
PS from nozzles connected to the both side surfaces of the
processing chamber 10. In this case, specified gaseous mixtures can
be supplied through an upper portion and a side portion of the
plasma generation space PS, respectively. Therefore, a gas
concentration in the plasma generation space PS can be adjusted,
whereby an in-surface uniformity of an etching characteristic can
be further improved on the wafer.
[0057] Although a flow rate of the branch line is adjusted by a
pressure control unit in the preferred embodiment, it is possible
to employ a mass flow controller. Further, although the gas supply
unit 100 described in the preferred embodiment is for supplying the
gaseous mixture to the plasma etching apparatus 1, the present
invention can be applied to another substrate processing apparatus
into which a gaseous mixture is supplied, e.g., a film forming
apparatus such as a plasma CVD apparatus, a sputtering device and a
thermal oxidation apparatus. Further, the present invention can be
also applied to an apparatus for processing a substrate other than
a wafer, e.g., FPD (flat panel display) and a mask reticle for
photomask, and MEMS (Micro Electro Mechanical System) manufacturing
apparatus and the like.
[0058] While the invention has been shown and described with
respect to the preferred embodiment, it will be understood by those
skilled in the art that various changes and modifications may be
made without departing from the spirit and scope of the invention
as defined in the following claims.
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