U.S. patent application number 13/928645 was filed with the patent office on 2014-01-02 for plasma processing apparatus and plasma processing method.
The applicant listed for this patent is Hitachi High-Technologies Corporation. Invention is credited to Masaru IZAWA, Go MIYA, Takumi TANDOU.
Application Number | 20140004706 13/928645 |
Document ID | / |
Family ID | 49778562 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140004706 |
Kind Code |
A1 |
MIYA; Go ; et al. |
January 2, 2014 |
PLASMA PROCESSING APPARATUS AND PLASMA PROCESSING METHOD
Abstract
Provided is a plasma processing apparatus which includes a
plurality of upstream-side expansion valves and a plurality of
downstream-side expansion valves connected to respective
refrigerant inlets and respective refrigerant outlets to adjust a
flow rate or a pressure of a refrigerant flowing into the
respective refrigerant inlets and a flow rate or a pressure of a
refrigerant flowing out from the respective refrigerant outlets.
Openings of the upstream-side expansion valves and openings of the
downstream-side expansion valves are adjusted so that no change in
flow rate of the refrigerant occurs in a plurality of refrigerant
channels between the plurality of upstream-side expansion valves
and the plurality of downstream-side expansion valves via the
plurality of refrigerant channels in a refrigeration cycle allowing
the refrigerant to flow therein.
Inventors: |
MIYA; Go; (Hachioji, JP)
; IZAWA; Masaru; (Hino, JP) ; TANDOU; Takumi;
(Hikari, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi High-Technologies Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
49778562 |
Appl. No.: |
13/928645 |
Filed: |
June 27, 2013 |
Current U.S.
Class: |
438/710 ;
156/345.27; 156/345.37 |
Current CPC
Class: |
H01J 37/32825 20130101;
H01J 2237/2001 20130101; H01L 21/3065 20130101; H01J 2237/334
20130101; H01J 37/32724 20130101; H01L 21/67069 20130101; H01L
21/67017 20130101; H01L 21/67109 20130101 |
Class at
Publication: |
438/710 ;
156/345.37; 156/345.27 |
International
Class: |
H01L 21/3065 20060101
H01L021/3065; H01L 21/67 20060101 H01L021/67 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 28, 2012 |
JP |
2012-144898 |
Claims
1. A plasma processing apparatus including a processing chamber
that is arranged in a vacuum container and allows plasma to be
formed therein, a sample stage on which a sample, which is an
object to be processed by the plasma, is mounted, the sample stage
including a plurality of refrigerant channels that are
concentrically arranged and allow a refrigerant to flow inside and
functioning as a first evaporator, a refrigerant inlet and a
refrigerant outlet arranged in each of the plurality of refrigerant
channels, and an exhaust unit that exhausts an inside of the
processing chamber for pressure reduction, the apparatus
comprising: a plurality of upstream-side expansion valves and a
plurality of downstream-side expansion valves that are connected to
the respective refrigerant inlets and the respective refrigerant
outlets and adjust a flow rate or a pressure of a refrigerant
flowing into the respective refrigerant inlets and a flow rate or a
pressure of a refrigerant flowing out from the respective
refrigerant outlets; and a refrigeration cycle including a
compressor, a condenser, the plurality of upstream-side expansion
valves, the plurality of refrigerant channels, the plurality of
downstream-side expansion valves and a second evaporator connected
in this order via a refrigerant duct, and allowing the refrigerant
to flow in the order, wherein openings of the plurality of
upstream-side expansion valves and openings of the plurality of
downstream-side expansion valves are adjusted so that no change in
flow rate of the refrigerant occurs in a plurality of refrigerant
paths between the plurality of upstream-side expansion valves and
the plurality of downstream-side expansion valves via the plurality
of refrigerant channels.
2. The plasma processing apparatus according to claim 1, wherein
the openings of the plurality of upstream-side expansion valves and
the openings of the plurality of downstream-side expansion valves
are adjusted so that no change in flow rate of the refrigerant
occurs in the plurality of refrigerant paths, the flow rate being
detected based on a result of detection by each of detectors that
are arranged on a plurality of refrigerant ducts between the
plurality of upstream-side expansion valves and the respective
refrigerant inlets of the plurality of refrigerant channels and
detect respective temperatures of the refrigerants flowing in the
respective refrigerant ducts.
3. The plasma processing apparatus according to claim 1, wherein
the plurality of refrigerant channels include a center-side
refrigerant channel arranged on a center side of the sample stage
and an outer periphery-side refrigerant channel arranged on an
outer periphery side of the sample stage, and the openings of the
plurality of upstream-side expansion valves and the openings of the
plurality of downstream-side expansion valves are adjusted so that
a sum of reciprocals of respective refrigerant conductances of the
upstream-side expansion valve and the downstream-side expansion
valves connected to the center-side refrigerant channel is equal to
a sum of reciprocals of respective refrigerant conductances of the
upstream-side expansion valve and the downstream-side expansion
valve connected to the outer periphery-side refrigerant
channel.
4. The plasma processing apparatus according to claim 1, wherein
the plurality of refrigerant channels include a center-side
refrigerant channel arranged on a center side of the sample stage
and an outer periphery-side refrigerant channel arranged on an
outer periphery side of the sample stage, the plurality of
upstream-side expansion valves and the plurality of downstream-side
expansion valves include a common configuration, and the openings
of the plurality of upstream-side expansion valves and the openings
of the plurality of downstream-side expansion valves are adjusted
so that a sum of reciprocals of the openings of the upstream-side
expansion valve and the downstream-side expansion valve connected
to the center-side refrigerant channel is equal to a sum of
reciprocals of the openings of the upstream-side expansion valve
and the downstream-side expansion valve connected to the outer
periphery-side refrigerant channel.
5. The plasma processing apparatus according to claim 4, wherein
the openings of the plurality of upstream-side expansion valves and
the openings of the plurality of downstream-side expansion valves
are adjusted so that a sum of the opening of the downstream-side
expansion valve connected to the center-side refrigerant channel
and the opening of the upstream-side expansion valve connected to
the outer periphery-side refrigerant channel is equal to a sum of
the opening of the upstream-side expansion valve connected to the
center-side refrigerant channel and the opening of the
downstream-side expansion valve connected to the outer
periphery-side refrigerant channel.
6. The plasma processing apparatus according to claim 1, further
comprising a main line and a bypass line that is arranged in
parallel to the main line and includes a capillary with a small
conductance, the main line and the bypass line allowing the
refrigerant to flow therethrough, a valve that is provided on an
upstream side of each of the main line and the bypass line to
open/close the respective line, and a thermometer provided on a
downstream side of the main line and the bypass line, between the
condenser and the plurality of upstream-side expansion valves.
7. A plasma processing method for processing a sample that is an
object to be processed by plasma, by mounting the sample on an
upper surface of a sample stage arranged in a processing chamber
inside a vacuum container and forming the plasma in the processing
chamber, the sample stage including a refrigerant inlet and a
refrigerant outlet arranged in each of a plurality of refrigerant
channels that are concentrically arranged inside the sample stage
and allow a refrigerant to flow inside, and functioning as a first
evaporator, the sample stage is included in a refrigeration cycle
including a plurality of upstream-side expansion valves and a
plurality of downstream-side expansion valves connected to the
respective refrigerant inlets and the respective refrigerant
outlets to adjust a flow rate or a pressure of a refrigerant
flowing into the respective refrigerant inlets and a flow rate or a
pressure of a refrigerant flowing out from the respective
refrigerant outlets, in which a compressor, a condenser, the
plurality of upstream-side expansion valves, the plurality of
refrigerant channels, the plurality of downstream-side expansion
valves and a second evaporator are connected in this order via a
refrigerant duct to allow the refrigerant to flow therethrough in
the order, the method comprising: adjusting openings of the
plurality of upstream-side expansion valves and openings of the
plurality of downstream-side expansion valves so that no change in
flow rate of the refrigerant occurs in a plurality of refrigerant
paths between the plurality of upstream-side expansion valves and
the plurality of downstream-side expansion valves via the plurality
of refrigerant channels.
8. The plasma processing method according to claim 7, wherein the
openings of the plurality of upstream-side expansion valves and the
openings of the plurality of downstream-side expansion valves are
adjusted so that no change in flow rate of the refrigerant occurs
in the plurality of refrigerant paths, the flow rate being detected
based on a result of detection by each of detectors that are
arranged on a plurality of refrigerant ducts between the plurality
of upstream-side expansion valves and the respective refrigerant
inlets of the plurality of refrigerant channels and detect
respective temperatures of the refrigerants flowing in the
respective refrigerant ducts.
9. The plasma processing method according to claim 7, wherein the
plurality of refrigerant channels include a center-side refrigerant
channel arranged on a center side of the sample stage and an outer
periphery-side refrigerant channel arranged on an outer periphery
side of the sample stage; and wherein the openings of the plurality
of upstream-side expansion valves and the openings of the plurality
of downstream-side expansion valves are adjusted so that a sum of
reciprocals of refrigerant conductances of the upstream-side
expansion valve and the downstream-side expansion valve connected
to the center-side refrigerant channel is equal to a sum of
reciprocals of refrigerant conductances of the upstream-side
expansion valve and the downstream-side expansion valve connected
to the outer periphery-side refrigerant channel.
10. The plasma processing apparatus according to claim 7, wherein
the plurality of refrigerant channels includes a center-side
refrigerant channel arranged on a center side of the sample stage
and an outer periphery-side refrigerant channel arranged on an
outer periphery side of the sample stage, and the plurality of
upstream-side expansion valves and the plurality of downstream-side
expansion valves include a common configuration; and wherein the
openings of the plurality of upstream-side expansion valves and the
opening of the plurality of downstream-side expansion valves are
adjusted so that a sum of reciprocals of the openings of the
upstream-side expansion valve and the downstream-side expansion
valve connected to the center-side refrigerant channel is equal to
a sum of reciprocals of the openings of the upstream-side expansion
valve and the downstream-side expansion valve connected to the
outer periphery-side refrigerant channel.
11. The plasma processing method according to claim 10, wherein the
openings of the plurality of upstream-side expansion valves and the
openings of the plurality of downstream-side expansion valves are
adjusted so that a sum of the opening of the downstream-side
expansion valve connected to the center-side refrigerant channel
and the opening of the upstream-side expansion valve connected to
the outer periphery-side refrigerant channel is equal to a sum of
the opening of the upstream-side expansion valve connected to the
center-side refrigerant channel and the opening of the
downstream-side expansion valve connected to the outer
periphery-side refrigerant channel.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a plasma processing
apparatus and a processing method for performing processing such as
etching using plasma formed in a processing chamber inside a vacuum
container by mounting a sample, which is a substrate such as a
semiconductor wafer, on an upper surface of a sample stage arranged
in the processing chamber, and relates to a plasma processing
apparatus and a plasma processing method for performing the
processing while making a refrigerant flow through refrigerant
channels inside the sample stage included in a refrigeration cycle
to adjust a temperature of the sample stage.
[0002] Conventionally, in semiconductor device manufacturing
processes, plasma processing is performed on a sample such as a
semiconductor wafer by means of a plasma etching apparatus or a
plasma CVD apparatus. In these types of plasma processing, the
temperature of the sample largely affects the result of the
processing. More specifically, in plasma etching, the temperature
of the sample affects the resulting dimensions and/or shape of a
pattern formed at a surface of the sample by etching, and in plasma
CVD processing, the temperature of the sample affects the quality
and/or film formation rate of a film formed on a surface of the
sample. Therefore, in these types of plasma processing, in order to
enhance the quality of processing performed on a surface of the
sample substrate, it is very important to manage the temperature of
the sample.
[0003] In these types of plasma processing, in order to control the
temperature of a sample, techniques in which the temperature inside
a sample stage that holds a sample and the temperature of a sample
holding surface are adjusted by means of a temperature adjustment
unit arranged inside the sample stage have been employed. For
example, an apparatus system in which refrigerant channels are
formed inside a sample stage and a liquid refrigerant is made to
flow in the channels to adjust the temperature of the sample stage
by means of heat transfer, whereby the sample is adjusted to a
desired temperature, is used. In such case, a refrigerant
temperature adjustment section (for example, a chiller unit) is
connected to the sample stage via pipings, a refrigerant adjusted
to a predetermined temperature by a cooling apparatus or a heating
apparatus inside the refrigerant temperature adjustment section is
supplied into the channels inside the sample stage, and absorbs
heat input from plasma and then is returned to the refrigerant
temperature adjustment section.
[0004] Such refrigerant temperature adjustment section is
configured so as to temporarily store the liquid refrigerant in a
refrigerant storage tank and adjust the temperature of the
refrigerant and then supplies the refrigerant to the sample stage.
In this configuration, since a large quantity of refrigerant is
used for temperature adjustment, the heat capacity of the
refrigerant is large, and thus, the configuration is advantageous
in maintaining the temperature of the sample constant even if the
amount of heat input to the sample and the sample stage is changed.
However, an attempt to largely and promptly change the temperatures
of the sample and the sample stage in an active manner causes the
problem of difficulty in prompt temperature change because of the
large heat capacity of the refrigerant. Furthermore, heat exchange
between the liquid refrigerant and the channels is performed only
by means of heat transfer and thus, a small quantity of heat
transfer is also one of causes that hinder prompt change in
temperature of the sample stage and the sample.
[0005] Meanwhile, along with an increase in diameter of
semiconductor wafers, which are samples, in the aforementioned
plasma processing in semiconductor device manufacturing, power
applied to the samples during the processing has been increasing,
and as a result, the amount of heat input to the sample and the
sample stage has become larger than ever. Therefore, there is a
demand for a technique that stably adjusts the temperature of a
semiconductor substrate at high speed and with high accuracy even
upon input of a large amount of heat. Furthermore, because of the
growing complexity of semiconductor device structures as well as
provision of multiple layers on semiconductor substrate surface, it
is desired to promptly and properly adjust the temperature of a
sample according to each of processing steps that process
respective films.
[0006] For responding to the above issues, direct expansion-type
refrigerant temperature adjustment techniques have been proposed.
In the expansion-type refrigerant temperature adjustment
techniques, a path in which a refrigerant for adjusting a
temperature of a sample stage is circulated is configured as a heat
cycle including a compressor, a condenser, an expansion valve and
an evaporator, and the refrigerant is brought to boiling and
evaporated in refrigerant channels in the sample stage, whereby the
sample stage acts as an evaporator in the heat cycle. As an example
of such techniques, that disclosed in JP-A-2008-34409
(corresponding to U.S. Pat. No. 7,838,792) is known.
SUMMARY OF THE INVENTION
[0007] In a configuration of the heat cycle described in
JP-A-2008-34409, for example, hydrochlorofluorocarbon R410a is used
as a refrigerant and is introduced into refrigerant channels inside
a sample stage to use evaporative latent heat of the refrigerant in
a gas-liquid two-phase flow state for heat exchange between the
refrigerant and walls of the channels, in order to respond to a
large amount of heat input to a sample and the sample stage.
Furthermore, adjusting an opening of an expansion valve to quickly
adjust a pressure of the refrigerant in the channels, enabling a
temperature of the refrigerant to be quickly changed, and as a
result, the temperatures of the sample stage and the sample can
quickly be changed.
[0008] Furthermore, JP-A-2008-34409 discloses a configuration in
which refrigerant channels are concentrically arranged on the inner
and outer sides of an inner portion of the sample stage and the
refrigerant is made to flow in the respective channels, achieving
temperature distribution in a radial direction of the sample stage.
In other words, a flow valve is provided on the upstream side of
each channel and openings of the valves are adjusted, enabling
pressures of the refrigerant in the respective routes to be
independently controlled, and as a result, the refrigerant
temperatures in the respective routes can be controlled.
Consequently, the temperature distributions in the sample stage and
the sample can be controlled.
[0009] Also, where a refrigerant flowing in refrigerant channels
inside a sample stage is in a gas-liquid two-phase flow state, even
if the refrigerant absorbs heat input from plasma, the temperature
of the refrigerant does not increase beyond a boiling point
thereof, and thus, the refrigerant temperature during the
refrigerant circulating in the refrigerant channels is maintained
constant.
[0010] Therefore, a temperature distribution in a circumferential
direction of a circular sample stage becomes closer to a uniform
distribution, and as a result, a temperature distribution in a
circumferential direction of a semiconductor wafer, which is a body
to be processed, can be made to be closer to a uniform
distribution.
[0011] However, the aforementioned related technique has problems
because of insufficiency in consideration of the following points.
In other words, JP-A-2008-34409 has the problem that a refrigerant
merging point is provided downstream of an outlet of each channel,
making it possible to provide a large pressure difference between
the respective channels, resulting in difficulty in providing a
large difference in condition, for example, temperature or
evaporation temperature, of a refrigerant between the respective
channels. Therefore, it has been difficult to efficiently provide a
distribution with a large temperature difference in a surface of a
sample in a short period of time.
[0012] Still furthermore, in ordinary plasma processing, a
refrigerant introduced into a sample stage is set to a
predetermined temperature or an evaporation temperature, and
adjustment is made so that the sample stage and a sample have
desired temperatures suitable for the processing. However,
JP-A-2008-34409 mentioned above discloses no specific method for
adjusting a refrigerant to a target temperature.
[0013] Furthermore, employment of independent refrigerant
temperature adjustment units, for example, refrigeration cycles,
are connected to respective channels inside a sample stage requires
a number of refrigeration cycles, the number being equal to the
number of paths, resulting in an increase in size and cost of the
semiconductor manufacturing apparatus.
[0014] The present invention is intended to provide a plasma
processing apparatus and a plasma processing method that
efficiently achieve a temperature or a temperature distribution in
a sample stage on which a sample is mounted in a plasma processing
apparatus in which refrigerant channels in the sample stage are
connected to a refrigeration cycle as a part thereof to adjust the
temperature of the sample stage.
[0015] In order to provide such a plasma processing apparatus, the
plasma processing apparatus is configured to include a processing
chamber that is arranged in a vacuum container and allows plasma to
be formed therein, a sample stage on which a sample, which is an
object to be processed by the plasma, is mounted, the sample stage
including a plurality of refrigerant channels that are
concentrically arranged and allow a refrigerant to flow inside and
functioning as a first evaporator, a refrigerant inlet and a
refrigerant outlet arranged in each of the plurality of refrigerant
channels, and an exhaust unit that exhausts an inside of the
processing chamber for pressure reduction, the apparatus
including:
[0016] a plurality of upstream-side expansion valves and a
plurality of downstream-side expansion valves that are connected to
the respective refrigerant inlets and the respective refrigerant
outlets and adjust a flow rate or a pressure of a refrigerant
flowing into the respective refrigerant inlets and a flow rate or a
pressure of a refrigerant flowing out from the respective
refrigerant outlets; and a refrigeration cycle including a
compressor, a condenser, the plurality of upstream-side expansion
valves, the plurality of refrigerant channels, the plurality of
downstream-side expansion valves and a second evaporator connected
in this order via a refrigerant duct, and allowing the refrigerant
to flow in the order, wherein openings of the plurality of
upstream-side expansion valves and openings of the plurality of
downstream-side expansion valves are adjusted so that no change in
flow rate of the refrigerant occurs in a plurality of refrigerant
paths between the plurality of upstream-side expansion valves and
the plurality of downstream-side expansion valves via the plurality
of refrigerant channels.
[0017] In order to provide such a plasma processing method, the
plasma processing method for processing a sample that is an object
to be processed by plasma, by mounting the sample on an upper
surface of a sample stage arranged in a processing chamber inside a
vacuum container and forming the plasma in the processing
chamber,
[0018] the sample stage including a refrigerant inlet and a
refrigerant outlet arranged in each of a plurality of refrigerant
channels that are concentrically arranged inside the sample stage
and allow a refrigerant to flow inside, and functioning as a first
evaporator,
[0019] the sample stage is included in a refrigeration cycle
including a plurality of upstream-side expansion valves and a
plurality of downstream-side expansion valves connected to the
respective refrigerant inlets and the respective refrigerant
outlets to adjust a flow rate or a pressure of a refrigerant
flowing into the respective refrigerant inlets and a flow rate or a
pressure of a refrigerant flowing out from the respective
refrigerant outlets, in which a compressor, a condenser, the
plurality of upstream-side expansion valves, the plurality of
refrigerant channels, the plurality of downstream-side expansion
valves and a second evaporator are connected in this order via a
refrigerant duct to allow the refrigerant to flow therethrough in
the order, the method including the step of
[0020] adjusting openings of the plurality of upstream-side
expansion valves and openings of the plurality of downstream-side
expansion valves so that no change in flow rate of the refrigerant
occurs in a plurality of refrigerant paths between the plurality of
upstream-side expansion valves and the plurality of downstream-side
expansion valves via the plurality of refrigerant channels.
[0021] According to the present invention, dry-out of a
temperature-adjusted fluid to be introduced into a sample stage can
be prevented and a temperature of the temperature-adjusted fluid
can efficiently be controlled.
[0022] Other objects, features and advantages of the invention will
become apparent from the following description of the embodiments
of the invention taken in conjunction with the accompanying
drawings.
BRIEF EXPLANATION OF DRAWINGS
[0023] FIG. 1 is a vertical cross-sectional diagram illustrating an
overview of a configuration of a plasma processing apparatus
according to an embodiment of the present invention;
[0024] FIG. 2 is a cross-sectional diagram schematically
illustrating a configuration of a sample stage in the embodiment
illustrated in FIG. 1;
[0025] FIG. 3 is a diagram schematically illustrating a
configuration that performs temperature control of the sample stage
in the embodiment illustrated in FIG. 1;
[0026] FIG. 4 is a flowchart illustrating the flow of operation for
controlling temperatures of the sample stage in the embodiment
illustrated in FIG. 1;
[0027] FIG. 5 includes time charts of openings of expansion valves
and refrigerant temperatures when the plasma processing apparatus
according the embodiment illustrated in FIG. 1 performs the
operation illustrated in FIG. 4;
[0028] FIG. 6 is a diagram indicating a flowchart of operation for
adjusting openings of the expansion valves according to the
embodiment illustrated in FIG. 1;
[0029] FIG. 7 includes time charts indicating change in openings of
expansion valves and change in refrigerant temperatures according
to a variation of the embodiment illustrated in FIG. 1; and
[0030] FIG. 8 is a vertical cross-sectional diagram schematically
illustrating a configuration of a refrigerant temperature
adjustment section according to another variation of the embodiment
illustrated in FIG. 1.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0031] An embodiment of the present invention will be described
below with reference to the drawings.
[0032] JP-A-2008-34409 described above discloses a technique in
which two channels are concentrically arranged on the inner side
and the outer side of a sample stage connected to a refrigeration
cycle as refrigerant channels inside the sample stage, and a
refrigerant is made to flow in each of the channels after passage
through a compressor and a condenser included in one refrigeration
cycle to form a temperature distribution in the sample stage. In
this technique, a flow valve is provided on the upstream side of
each of the channels, enabling pressures of refrigerants in the
respective channels to be independently controlled by adjusting
openings of the flow valves, and as a result, temperature
distributions of the sample stage and a sample can be controlled by
adjusting temperatures of the respective refrigerants. However,
because a refrigerant merging point exists downstream of outlets of
the respective channels, a difference in pressure between the
respective routes cannot be expanded, resulting in difficulty in
increasing a difference in temperature between the refrigerants in
the respective channels. Therefore, there is the problem of
difficulty in responding to a case where it is desired to expand a
temperature difference within a plane of a sample.
[0033] Still furthermore, in normal plasma processing, a
refrigerant introduced to a sample stage is set to a certain target
temperature and the sample stage and a sample are adjusted to
respective desired temperatures to perform the processing. However,
JP-A-2008-34409 discloses no specific method for adjusting a
refrigerant to a target temperature.
[0034] Still furthermore, pipings bifurcated from the refrigerant
path in the refrigeration cycle are arranged in parallel and
connected to respective inlets of the two refrigerant channels, and
two pipings arranged in parallel are connected to outlets of the
channels, a valve is provided on each of the pipings, and the two
pipings are merged on the downstream side and connected to the
compressor. In this configuration, for example, if an opening of
the valve connected to the outer-side channel is increased to
change a temperature of a refrigerant on the outer side with an
opening of the valve connected to the inner-side channel unchanged
in order to maintain a temperature of a refrigerant in the
inner-side refrigerant channel, a flow rate of the refrigerant
flowing to the outer-side channel is increased while a flow rate of
the refrigerant flowing into the inner-side channel is
decreased.
[0035] As a result, despite of the opening of the valve for the
inner-side channel being unchanged, the temperature of the
refrigerant in the inner-side channel is decreased. In other words,
the problem that adjustment of an opening of a valve for one
channel affects a temperature of a refrigerant in the other channel
occurs. In such situation, what is called hunting occurs, e.g.,
change in the temperature of the refrigerant in the inner-side
channel resulting in change in the temperature of the refrigerant
in the outer-side channel, or conversely, correction of the
temperature on the outer periphery side resulting in change in the
temperature on the inner side, causing the problem of difficulty in
adjustment of the temperature of the refrigerant and thus
adjustment of the temperatures and temperature distributions of the
sample stage and the sample.
[0036] Furthermore, for example, if the opening of the valve for
one channel is made to be extremely small, the flow rate of a
refrigerant in the channel becoming extremely small, increasing the
risk of occurrence of what is called dry-out, i.e., the refrigerant
including one in a liquid state being completely evaporated while
the refrigerant flows in the channel. If dry-out of a refrigerant
occurs in a channel, the temperature of the refrigerant in the
channel sharply rises, a temperature distribution in the sample
stage in a direction in which the refrigerant flows in the channel
in the sample stage substantially changes, resulting in the problem
of a temperature distribution in a circumferential direction of the
sample such as a semiconductor wafer departing from a desired
distribution.
[0037] As a solution to these problems, employment of a technique
of connecting independent refrigerant temperature adjustment units
such as refrigeration cycles to the respective channels requires a
number of refrigerant temperature adjustment units, the number
being equal to the number of channels, resulting in an increase in
size and cost of the semiconductor manufacturing apparatus, which
cannot be considered as an effective solution.
[0038] The present embodiment is intended to solve the
aforementioned problems, and provide a plasma processing apparatus
employing a direct expansion-type temperature adjustment unit for
adjustment of a temperature distribution in a sample and
efficiently enabling adjustment of temperatures of refrigerants
flowing and circulating in a plurality of refrigerant channels in a
sample stage and thus achievement of temperatures and temperature
distributions of the sample stage and the sample.
Embodiment
[0039] An embodiment of the present invention will be described
below with reference to FIGS. 1 to 6. FIG. 1 is a vertical
cross-sectional diagram schematically illustrating an overview of a
configuration of a plasma processing apparatus according to an
embodiment of the present invention.
[0040] In the Figure, in the plasma processing apparatus, an
electric field and magnetic field forming unit for forming plasma
is arranged above a cylindrical vacuum container 1 and an exhaust
unit that exhausts an inside of the vacuum container 1 is connected
to a lower portion of the cylindrical vacuum container 1. A
processing chamber 3, which is a space arranged inside the vacuum
container 1, is a space whose pressure is reduced and in which a
sample 5 to be processed, which is in the form of a substrate such
as a semiconductor wafer, is arranged and processed.
[0041] At an upper portion of the vacuum container 1, a lid 2,
which is a circular plate of a dielectric material such as quartz
and provides a lid positioned above the processing chamber 3 and
defining the inside of the vacuum container 1 and the processing
chamber 3 in an air-tight manner, is arranged. At a lower portion
of the processing chamber 3, a cylindrical sample stage 4 is
arranged, and the sample 5 is held and transferred by an arm of a
non-illustrated transfer robot arm to/from an upper surface of the
sample stage 4, which is a mounting surface having a circular shape
so as to conform to a shape of the sample 5, in the processing
chamber 3.
[0042] A gas introduction tube 6 is connected to an upper portion
of the processing chamber 3, and a process gas 7 that flows in the
gas introduction tube 6 is introduced to the processing chamber 3
for performing etching via at least one (desirably a plurality of)
introduction port(s) connected to the gas introduction tube 6. At a
lower portion of the processing chamber 3 below the sample stage 4,
an exhaust port 8 is arranged, and the process gas 7 introduced
into the processing chamber 3 and/or a reaction product generated
as a result of etching pass through the exhaust port 8 and are
discharged to the outside of the processing chamber 3. The exhaust
port 8 is connected to a vacuum pump such as a turbo-molecular pump
12 with a pressure adjustment valve 9 interposed therebetween, and
an opening of the pressure adjustment valve 9 is adjusted, whereby
an exhaust gas flow rate of the vacuum pump is adjusted and the
pressure of the processing chamber 3 is adjusted to a pressure with
a predetermined degree of vacuum (no more than 4 Pa in the present
embodiment) according to a balance between the flow rate of the
vacuum pump and a flow rate of the introduced process gas 7.
[0043] Above the processing chamber 3, an electric field or
magnetic field generation device is arranged. In the present
embodiment, for an electric field, microwave 10 emitted from a
microwave emitter 14 such as a magnetron is used. Microwave 10
generated by the microwave emitter 14 arranged at an end portion of
the waveguide 16 propagates horizontally and then downward in a
vertical direction in the waveguide 16 and forms an electric field
in a predetermined mode in a resonance section, which is a
cylindrical space with the lid 2 at the upper portion of the
processing chamber 3 as a bottom surface thereof, and the electric
field penetrates the lid 2 and is introduced into the processing
chamber 3 from above.
[0044] Furthermore, above the lid 2 and in an outer periphery of
sidewalls of a cylindrical portion that forms the processing
chamber 3 of the vacuum container 1, solenoidal coils 18 for
forming a magnetic field upon supply of direct power are arranged.
Magnetic fields generated by the solenoidal coils 18 are introduced
into the processing chamber 3, and interact with the microwave 10
introduced into the processing chamber 3, thereby making atoms and
molecules of the process gas 7 form plasma 11 in the processing
chamber 3.
[0045] Using the plasma 11, etching is performed on a film
structure that is formed on an upper surface of the sample 5 in
advance and includes a plurality of film layers. The film structure
in the present embodiment includes a mask layer of, e.g., a resin
photoresist at an upper portion thereof and at least one gate,
metal or insulating film layer, which is an object to be processed,
arranged below the photoresist.
[0046] Also, in the present embodiment, in order to adjust a
temperature of the sample 5 so as to fall within a range of values
suitable for the processing, channels for a refrigerant, which is a
medium for heat exchange, are arranged inside the sample stage 4.
Inside each refrigerant channel 20, hydrochlorofluorocarbon R410a
circulates as a refrigerant in such a manner that the refrigerant
enters from an inlet of the refrigerant channel 20, is evaporated
as a result of heat exchange with a member of the sample stage 4
inside the refrigerant channel 20 in the sample stage 4 and flows
from an outlet of the refrigerant channel 20 to the outside of the
sample stage 4, and then, as described later, flows through a
refrigeration cycle in which the refrigerant condenses and
devolatilized again and flows into the sample stage 4 via the inlet
of the refrigerant channel 20 again.
[0047] A configuration of the refrigerant channels will be
described in more detail below with reference to FIG. 2. FIG. 2 is
a cross-sectional diagram schematically illustrating a
configuration of the sample stage in the embodiment illustrated in
FIG. 1.
[0048] As illustrated in the Figure, the refrigerant channels 20
include multiple channels that are concentrically arranged and
overlap in a radial direction inside the sample stage 4 having a
cylindrical shape or a circular plate shape in transverse cross
section, and each includes an inlet and an outlet for a
refrigerant. More specifically, the refrigerant channels 20 include
a plurality of concentric channels including a center-side
refrigerant channel 20-1 and an outer periphery-side refrigerant
channel 20-2 on the center side and the outer periphery side of the
sample stage 4 and the sample 5.
[0049] These two channels each include an inlet and an outlet for a
refrigerant, and refrigerants in different conditions are supplied
to, and circulate in, the channels. For example, if a temperature
at which a refrigerant circulating in the center-side refrigerant
channel 20-1 evaporates is made to higher than an evaporation
temperature of the refrigerant circulating in the outer
periphery-side refrigerant channel 20-2, a temperature distribution
in a surface of the sample stage 4 and in the radial direction of
the sample 5 exhibit high temperatures at the center-side portion,
and if the temperature values are plotted on a graph, the graph
exhibits a convex distribution in which exhibits high values in a
center part and low values in outer peripheral parts. Conversely,
if the evaporation temperature of the refrigerant circulating in
the center-side refrigerant channel 20-1 is made to be lower than
the evaporation temperature of the refrigerant circulating in the
outer periphery-side refrigerant channel 20-2, a temperature
distribution in the surface of the sample stage 4 and in the radial
direction of the sample 5 exhibit a concave distribution.
[0050] As illustrated in FIG. 1, the refrigerant channels 20 in the
sample stage 4 form a part of the refrigeration cycle, the part
being connected to components such as a compressor 22 and expansion
valves 24-1, 24-2, 24-3 and 24-4 arranged outside the sample stage
4 via refrigerant ducts in which a refrigerant flows. In such
configuration, a refrigerant draws latent heat as a result of
evaporation by means of heat exchange in the refrigerant channels
20 in the sample stage 4, condenses outside the sample stage 4,
releases the latent heat, and devolatilizes again.
[0051] The center-side refrigerant channel 20-1 includes a
center-side refrigerant inlet 30-1 and a center-side refrigerant
outlet 32-1 inside, and a refrigerant is introduced into the
center-side refrigerant channel 20-1 from the center-side
refrigerant inlet 30-1 via expansion valve 24-1. In the present
embodiment, the refrigerant introduced into the center-side
refrigerant inlet 30-1 is split into two sides, i.e., in clockwise
and counterclockwise directions, along a circumference of the
refrigerant channel arranged in the form of a circular arc, and the
split refrigerants flow through the center-side refrigerant channel
20-1 and merge at the outer periphery-side refrigerant outlet 32-1
arranged in an outer periphery-side part of the center-side
refrigerant channel 20-1 in which the center-side refrigerant inlet
30-1 is arranged, and the merged refrigerant flows out from the
center-side refrigerant channel 20-1 and flows toward the
compressor 22 via the expansion valve 24-3.
[0052] Likewise, the refrigerant is introduced into the outer
periphery-side refrigerant channel 20-2 through an outer
periphery-side refrigerant inlet 30-2 via the expansion valve 24-2,
and is split into two sides and the split refrigerants flow through
the outer periphery-side refrigerant channel 20-2 and merge at an
outer periphery-side refrigerant outlet 32-2 arranged in a
center-side part of the outer periphery-side refrigerant channel
20-2 in which the outer periphery-side refrigerant inlet 30-2 is
arranged and the merged refrigerant flows toward the compressor 22
via the expansion valve 24-4.
[0053] In the present embodiment, a flow rate or a pressure of the
refrigerant flowing out from the center-side refrigerant channel
20-1 and a flow rate or a pressure of the refrigerant flowing out
from the outer periphery-side refrigerant channel 20-2 are adjusted
at the respective expansion valves 24-3 and 24-4 arranged on the
respective refrigerant ducts connected to the center-side
refrigerant outlet 32-1 and the outer periphery-side refrigerant
outlet 32-2. The expansion valves 24-3 and 24-4 each include a
valve for variably adjusting a cross-sectional area of a
refrigerant passage arranged inside, and the flow rate of the
refrigerant is changed by increasing or decreasing the opening of
the valve. Also, in the present embodiment, each of the expansion
valves 24-3 and 24-4 may be one including a configuration that
rapidly reduces an internal pressure in an internal passage to
gasify the refrigerant to adjust the pressure of the
refrigerant.
[0054] In the present embodiment, the refrigerant ducts connected
to the expansion valves 24-3 and 24-4 are connected to the
compressor on the refrigerant downstream side, and thus, the
pressures of the refrigerants passing through the expansion valves
24-3 and 24-4 can also be decreased and adjusted by means of
adjustment of the flow rates made by increasing/decreasing the
openings. The refrigerants whose pressures have been adjusted
through the expansion valves 24-3 and 24-4 subsequently merge in a
merging section 52 in which the two refrigerant ducts merge, and
the merged refrigerant is introduced into a refrigerant temperature
adjustment section 21 in which a temperature of the refrigerant
with latent heat absorbed is adjusted. The refrigerant temperature
adjustment section 21, which is included in the refrigeration cycle
including the refrigerant channels 20 in the sample stage 4 and is
a part that makes the refrigerant perform heat exchange to release
internal latent heat again to devolatilize, and includes an
evaporator 26, the compressor 22 and a condenser 23, which are
connected in this order via refrigerant ducts.
[0055] The refrigerant introduced into the refrigerant temperature
adjustment section 21 is first introduced into the evaporator 26.
The evaporator 26 includes a channel arranged at a position and
with a configuration that enable heat exchange with the refrigerant
duct in which the introduced refrigerant flows inside, in parallel
to the refrigerant duct, the channel allowing water 25-1, which is
a heat exchange medium for heat exchange with the refrigerant, to
flow inside. In the present embodiment, the refrigerant flowing in
the refrigerant duct has a decreased pressure after the passage
through the expansion valves 24-3 and 24-4, and the refrigerant
whose temperature has thus been decreased perform heat exchange
with the water 25-1 flowing and circulating in the heat exchange
medium channel in the evaporator 26 and thereby evaporates, and is
gasified until a dryness or quality of substantially 1 is
achieved.
[0056] The sample stage 4 including the refrigerant channels 20 in
the present embodiment can also function as an evaporator, and the
evaporator 26 also serves as a second evaporator. Also, as
described later, the sample stage 4 has a configuration that can
also operate as a condenser (heater for a sample) by variably
adjusting pressures or evaporating pressures of the refrigerants in
the refrigerant channels 20 inside the sample stage 4 by a balance
among the openings of the expansion valves 24-1 to 24-4 provided by
operations of the expansion valves 24-1 to 24-4.
[0057] The gasified refrigerant is introduced into an inlet of the
compressor 22 and compressed inside the compressor 22, whereby the
pressure of the refrigerant is increased. The high-pressure flowing
out from an outlet of the compressor 22 is introduced into the
condenser 23 and condenses. In the condenser 23, as with the
evaporator 26, a channel in which water 25-2, which is a heat
exchange medium, flows inside is arranged so as to exchange heat
with the refrigerant duct, and the refrigerant introduced into the
condenser 23 performs heat exchange with the water 25-2 flowing in
the heat exchange medium channel and is thereby cooled, and
condenses until a dryness or quality of substantially 0 is
achieved. Although in the present embodiment, the water 25-1 and
the water 25-2 are used as heat exchange mediums, other fluids may
be used.
[0058] The refrigerant flowing out from the condenser 23 flows in
the refrigerant duct toward the sample stage 4, and is split into
two paths at a bifurcation section 50 arranged on the refrigerant
duct. One of the two paths is a path with the expansion valve 24-1
arranged thereon, the path being connected to the center-side
refrigerant channel 20-1 in the sample stage 4, and the other is a
path with the expansion valve 24-2 arranged thereon, the path being
connected to the outer periphery-side refrigerant channel 20-2. The
expansion valves 24-1 and 24-2 have respective configurations that
are the same as those of the expansion valves 24-3 and 24-4, the
configurations variably increasing/decreasing a cross-sectional
area of the passage of the refrigerant that passes inside the
respective valve to adjust the flow rate of the refrigerant. Also,
the valves may have a configuration that rapidly decreases a
pressure inside the passage to gasify the refrigerant. Furthermore,
since the compressor 22 is connected to the expansion valves 24-1
and 24-2 on the downstream side of the refrigeration cycle via the
refrigerant ducts and the refrigerant channels 20 in the sample
stage 4, only adjustment of the flow rate of the refrigerant by the
expansion valves 24-1 and 24-2 enables adjustment of the pressure
on the downstream side of the refrigerant.
[0059] Subsequently, the refrigerants flowing these paths are
introduced into the inner peripheral-side refrigerant channel 20-1
and the outer periphery-side refrigerant channel 20-2 again,
respectively, and perform heat exchange with the members included
in the respective refrigerant channels in the sample stage 4 to
boil and gasify and flow out from the sample stage 4, and flow
toward the compressor 22 again via the expansion valves 24-3 and
24-4 to circulate. In the present embodiment, the openings of the
expansion valves 24-1 to 24-4 are adjusted by a non-illustrated
control section, whereby conditions such as evaporation
temperatures of the refrigerants introduced into the center-side
refrigerant channel 20-1 and the outer periphery-side refrigerant
channel 20-2 are adjusted so as to fall within a desired value
range.
[0060] For example, for the refrigerant introduced into the
center-side refrigerant channel 20-1, if the opening of the
expansion valve 24-1 connected to the inlet of the center-side
refrigerant channel 20-1 is decreased and/or if the opening of the
expansion valve 24-3 connected to the outlet of the center-side
refrigerant channel 20-1 is increased, the pressure of the
refrigerant flowing inside the center-side refrigerant channel
20-1, which is a refrigerant channel between these valves, is
decreased, resulting in a decrease in a temperature (evaporation
temperature) at which the refrigerant evaporates inside the channel
Conversely, if the opening of the expansion valve 24-1 is increased
and/or if the opening of the expansion valve 24-3 is decreased, the
pressure of the refrigerant circulating in the center-side
refrigerant channel 20-1 is increased, resulting in an increase in
evaporation temperature of the refrigerant.
[0061] Likewise, for the refrigerant introduced into the outer
periphery-side refrigerant channel 20-2, if the opening of the
expansion valve 24-2 is decreased and/or the opening of the
expansion valve 24-4 is increased, the pressure of the refrigerant
is decreased, resulting in a decrease in temperature of the
refrigerant circulating in the outer periphery-side refrigerant
channel 20-2. Conversely if the opening of the expansion valve 24-2
is increased and/or the opening of the expansion valve 24-4 is
decreased, the pressure of the refrigerant is increased, resulting
in an increase in temperature of the refrigerant circulating in the
outer periphery-side refrigerant channel 20-2. The temperatures and
the evaporation temperatures of the refrigerants flowing in the
inner peripheral-side refrigerant channel 20-1 and the outer
periphery-side refrigerant channel 20-2 are variably adjusted by
increasing/decreasing the openings of the respective expansion
valves 24-1 to 24-4, and the channels perform an operation as
either of an evaporator (cooler for a sample) and a condenser
(heater for a sample), which are switchable from each other.
[0062] In these cases, the temperatures of the refrigerants
introduced into the center-side refrigerant channel 20-1 and the
outer periphery-side refrigerant channel 20-2 are detected by a
thermometer 40-1 and a thermometer 40-2, respectively, arranged on
the respective refrigerant ducts downstream of the expansion valve
24-1 and the expansion valve 24-2 arranged on the refrigerant ducts
connected to the respective inlets, between the respective valves
and the center-side refrigerant inlet 30-1 and the outer
periphery-side refrigerant inlet 30-2. Hereinafter, the
temperatures of the refrigerants detected by the thermometer 40-1
and the thermometer 40-2 are referred to as T1 and T2,
respectively.
[0063] In the present embodiment, the temperatures or evaporation
temperatures of the refrigerants in the plurality of refrigerant
channels, i.e., the center-side refrigerant channel 20-1 and the
outer periphery-side refrigerant channel 20-2, which are branched
and supplied from the refrigerant temperature adjustment section 21
including one direct expansion-type heat cycle, are made to fall
within respective proper ranges by variable adjusting the openings
of the expansion valves 24-1 to 24-4. In the present specification,
one direct expansion-type heat cycle means a direct expansion-type
heat cycle including one compressor.
[0064] A configuration for control of the openings of the expansion
valves 24-1 to 24-4 will be described with reference to FIG. 3.
FIG. 3 is a diagram schematically illustrating a configuration that
performs temperature control of the sample stage in the embodiment
illustrated in FIG. 1. In the Figure, flows of signals are
indicated by dashed lines.
[0065] Respective signals indicating results of detection by the
thermometer 40-1 and the thermometer 40-2 are transmitted via any
of wire and wireless communications to an analysis section 35. The
analysis section 35 detects respective refrigerant temperatures T1
and T2 based on the respective signals, and detects temperature
values suitable for processing the sample 5 and necessary
temperatures or evaporation temperatures of the refrigerants
according to a distribution in the radial direction of the
temperature values, and calculates proper openings of the expansion
valves 24-1 to 24-4 according to the temperatures and the actual
refrigerant temperatures T1 and T2 detected from the signals.
Signals of the results of calculation are transmitted to a control
section 37 via communications, and the control section 37 transmits
instruction signals for achieving the calculated openings of the
expansion valves 24-1 to 24-4 to the expansion valves 24-1 to 24-4
or drive devices therefor to adjust the openings of the expansion
valves.
[0066] Although in the present embodiment, the analysis section 35
and the control section 37 are described as different members, the
analysis section 35 and the control section 37 may be included in
one integrated circuit, and thus may be included in a configuration
in which a plurality of circuits arranged on one substrate can
communicate with each other via wire or wireless communication
circuits. Also, the analysis section 35 is a circuit that includes
a memory, a computer and a communication interface inside, and the
computer including, e.g., a microprocessor or a microcomputer reads
an algorithm recorded in advance as software in a memory such as
DRAM or ROM as the memory or in an external storage apparatus such
as a hard disk drive or a CD-ROM drive, and based on the algorithm,
calculates the temperatures or the openings, or the instruction
signals, using signals received via the communication interface.
The computer, the memory and the communication interface may be
ones that have both functions of the analysis section 35 and the
control section 37.
[0067] Next, a configuration in which the refrigerant temperatures
of the center-side refrigerant channel 20-1 and the outer
periphery-side refrigerant channel 20-2 are adjusted by control of
the openings of the expansion valves 24-1 to 24-4 in the present
embodiment will be described in more detail.
[0068] In the present embodiment, control of the temperatures of
the respective refrigerants introduced to the center-side
refrigerant channel 20-1 and the outer periphery-side refrigerant
channel 20-2 is performed by adjusting the openings of the
expansion valves 24-1 to 24-4. In other words, the openings of the
expansion valves 24-1 to 24-4 are adjusted so that a conductance of
a refrigerant path including the expansion valve 24-1, the
center-side refrigerant channel 20-1 and the expansion valve 24-3,
and the refrigerant ducts connecting them as components thereof is
equal to a conductance of a refrigerant path including the
expansion valve 24-2, the outer periphery-side refrigerant channel
20-2 and the expansion valve 24-4, and the refrigerant ducts
connecting them as components thereof.
[0069] For example, for the refrigerant introduced into the
center-side refrigerant channel 20-1, adjustment is made so that
the opening of expansion valve 24-1 is decreased and the opening of
the expansion valve 24-3 is increased. As a result of such
operation, the pressure of the refrigerant in the refrigerant path
between the expansion valve 24-1 and the expansion valve 24-3
decreases, resulting in a decrease in temperature or evaporation
temperature of the refrigerant flowing in the center-side
refrigerant channel 20-1. Conversely, adjustment is made so that
the opening of the expansion valve 24-1 is increased and the
opening of the expansion valve 24-3 is decreased. As a result of
such operation, the pressure of the refrigerant flowing in the
center-side refrigerant channel 20-1 increases, whereby the
temperature or the evaporation temperature of the refrigerant is
increased.
[0070] Likewise, for the refrigerant flowing in the outer
periphery-side refrigerant channel 20-2, the opening of the
expansion valve 24-2 is decreased and the opening of the expansion
valve 24-4 is increased. Consequently, the pressure of the
refrigerant decreases, resulting in a decrease in temperature or
evaporation temperature of the refrigerant flowing in the outer
periphery-side refrigerant channel 20-2. Conversely, the opening of
the expansion valve 24-2 is increased and the opening of the
expansion valve 24-4 is decreased. Consequently, the pressure of
the refrigerant increases, and as a result, the temperature or the
evaporation temperature of the refrigerant flowing in the outer
periphery-side refrigerant channel 20-2 increases.
[0071] For performing the above-described operations of the
expansion valves 24-1 and 24-3 and the expansion valves 24-2 and
24-4, the openings of the expansion valves are adjusted according
to instructions from the analysis section 35 or the control section
37 so that the conductances of the refrigerant paths including the
refrigerant channels 20 in the sample stage 4 between the
respective valves are equal to each other. In other words, in the
present embodiment, where the conductances of the expansion valves
24-1 to 24-4 are C1 to C4, respectively, the openings of the
expansion valves are adjusted so as to satisfy expression 1
below.
1/C1+1/C3=1/C2+1/C4 (1)
[0072] Consequently, the refrigerant conductance of the refrigerant
path between the expansion valve 24-1 and the expansion valve 24-3
via the center-side refrigerant channel 20-1 and the conductance of
the refrigerant path between the expansion valve 24-2 and the
expansion valve 24-4 via the outer periphery-side refrigerant
channel 20-2 are made to have values that are equal to each other
or values that are approximate to each other enough to regard the
values as being substantially equal to each other, and even under
different processing conditions, the conductances are maintained
equal to each other, whereby the flow rates of the respective
refrigerants flowing in these paths are substantially equal to each
other. Therefore, even when the openings of the expansion valves in
one of the paths are changed in order to adjust the temperature of
the refrigerant, the flow rate of the refrigerant in the other path
is not affected by that change and can be maintained constant, and
thus, the temperature of the refrigerant can be maintained constant
if the openings of the expansion valves are not changed.
[0073] To be precise, the conductance of the center-side
refrigerant channel 20-1 is included in the path between the
expansion valve 24-1 and the expansion valve 24-3, and the
conductance of the outer periphery-side refrigerant channel 20-2 is
included in the path between the expansion valve 24-2 and the
expansion valve 24-4; however, the present inventors have confirmed
that since the conductances of the channels are large compared to
the conductances of the expansion valves 24-1 to 24-4, adjustment
of the openings of the expansion valves 24-1 to 24-4 that satisfies
the expression 1 causes no failure.
[0074] Also, in the present embodiment, the expansion valves 24-1
to 24-4 have a same configuration, and same performance can be
delivered even if any one of the expansion valves is replaced with
another. More specifically, for these expansion valves 24-1 and
24-4, same units and same parts are employed, and even if an
operation of any one of the expansion valves is performed by any
other one of the expansion valves, same results of refrigerant flow
rates or pressures are obtained. For adjustment of the openings of
the expansion valves 24-1 to 24-4, the openings in a range in which
conductances of refrigerants flowing in the respective expansion
valves are proportional to the openings of the respective expansion
valves. In such case, where V1 to V4 are the openings of the
expansion valves 24-1 to 24-4, the openings of the respective
expansion valves 24-1 to 24-4 are adjusted so as to satisfy the
following expression 2.
1/V1+1/V3=1/V2+1/V4 (2)
[0075] A flowchart for adjustment of the openings of the expansion
valves 24-1 to 24-4 where the above-described configuration is
employed in plasma etching using three different refrigerant
temperature conditions, that is, including three steps is
illustrated in FIG. 4, and time charts indicating change in
openings of the expansion valves 24-1 and 24-4 and change in
refrigerant temperatures are illustrated in FIG. 5. FIG. 4 is a
flowchart illustrating the flow of operation for adjusting
temperatures of the sample stage in the embodiment illustrated in
FIG. 1. FIG. 5 is a diagram illustrating time charts of the
openings of the expansion valves and adjusted fluid temperatures
when the plasma processing apparatus according to the embodiment
illustrated in FIG. 1 performs the operation indicated in FIG.
4.
[0076] Here, (a) in FIG. 5 is a time chart relating to refrigerant
temperatures T1 and T2, (b) in FIG. 5 is a time chart relating to
the opening V1 of the expansion valve 24-1 and the opening V3 of
the expansion valve 24-3, and (c) in FIG. 5 is a time chart
relating to the opening V2 of the expansion valve 24-2 and the
opening V4 of the expansion valve 24-4. Hereinafter, an operation
for adjustment of the openings of the expansion valves 24-1 and
24-4 will be described with reference to these Figures.
[0077] First, in step 1 (S1) of plasma etching, if set temperatures
for T1 and T2 are 20.degree. C., the respective openings of the
expansion valves 24-1 to 24-4 are set to 50% from the refrigerant
temperatures and a rotation speed of the compressor 22 (for
example, 3000 rpm), based on database in the control section
37.
[0078] Next, when the processing transitions from step 1 (S1) to
step 2 (S2) in which the set values for T1 and T2 are 25.degree. C.
and 20.degree. C., respectively, as illustrated in FIG. 5, in
transition step 12 (S12) between step 1 and step 2, it is necessary
to change T1 from 20.degree. C. to 25.degree. C. without changing
T2. In such case, V1 is increased while V3 is decreased: V3 is
adjusted according to the change of V1 so as to satisfy the
expression 2. Here, the refrigerant temperatures T1 and T2, which
are measured by the thermometer 40-1 and the thermometer 40-2, are
consistently measured, and adjustment of V1 and V3 is made until it
is determined that T1 has reached the set value. Also, in
transition step 12 (S12), there is no need to change T2, and thus
V2 and V4 are maintained at 50%.
[0079] In transition step 12 (S12), if it is determined that T1 has
reached the set value (25.degree. C. in this case), it is
determined that transition step S12 has been completed, and step 2
(S2) starts.
[0080] Next, if after an end of step 2 (S2), the processing
transitions to step 3 (S3) in which the set values for T1 and T2
are 30.degree. C. and 15.degree. C., respectively, in a first half
of transition step 23 (S23) between these steps, first, T2 is
changed from 20.degree. C. to 15.degree. C. without changing T1. In
such case, V2 is decreased while V4 is increased: V4 is adjusted
according to the change of V2 so as to satisfy the expression 2.
The adjustment of V2 and V4 are made until it is determined that T2
has reached the set value. Also, during that time period, V1 and V3
are maintained to make T1 constant.
[0081] In the first half of transition step 23 (S23), if it is
determined that T2 has reached the set value (15.degree. C. in this
case), next, in a second half of transition step 23 (S23),
adjustment for changing T1 to the set value (30.degree. C. in this
case) is made without changing T2. In that case, V1 is increased
while V3 is decreased: V3 is adjusted according to change of the
opening V1 so as to satisfy the expression 2. The adjustment of V1
and V3 is made until it is determined that T1 has reached the set
value. Also, during that time period, V2 and V4 are maintained to
make T2 constant.
[0082] In the second half of transition step 23 (S23), if it is
determined that T1 has reached the set value, it is determined that
transition step 23 (S23) has been completed, and step 3 (S3)
starts, and if the step ends, the etching ends.
[0083] Although the openings of the expansion valves 24-1 and 24-4
described above are adjusted so as to satisfy the expression 2,
while a set value for refrigerant temperature and T1 or T2 are
compared with each other, the method for the adjustment is not
limited to this method. For example, database is stored in advance
in the control section 37, initial set values for V1 to V4 are
estimated from set refrigerant temperatures, and first, V1 to V4
are set to the estimated values, and subsequently, fine adjustment
of V1 to V4 is made so that T1 and T2 reach the set values.
[0084] An excerpt of a flowchart for a case where an operation for
such adjustment is employed in transition step 12 (S12) is
illustrated in FIG. 6. FIG. 6 is a diagram illustrating a flowchart
of an operation for adjusting the openings of the expansion valves
according to the embodiment illustrated in FIG. 1.
[0085] If the processing transition from step 1 (S1) to step 2 (S2)
in which T1 and T2 are 25.degree. C. and 20.degree. C.,
respectively, first, initial set values for the openings V1 to V4
are estimated based on the database stored in the control section
37, and the openings are adjusted to those values. The initial set
values satisfy the expression 2 (S12-1).
[0086] Next, whether or not T1 and T2 have the set values in step 2
(S2) is determined. In this case, the determination is made only
for T1 because T2 remains unchanged. If T1 is higher than the set
value (25.degree. C. in this case), V1 is decreased so as to
decrease T1, and V3 is increased so as to satisfy the expression 2.
If T1 is lower than the set value, V1 is increased to increase T1,
and V3 is decreased to satisfy the expression 2. In this case, V2
and V4 are maintained because T2 remains unchanged. If it is
determined as a result of such adjustment that T1 has reached the
set value, it is determined that transition step S12 has been
completed, and step 2 (S2) starts.
[0087] As a result of such adjustment being made, T1 and T2 can be
adjusted to set values by first adjusting V1 to V4 to initial set
values and subsequently making fine adjustment of V1 to V4. Also,
if the processing transitions to step 3 (S3) after completion of
step 2 (S2), T1 and T2 can be adjusted to set values by adjusting
V1 to V4 in transition step 23 (S23) between these steps in a
manner similar to the above.
[0088] As a result of the above-described adjustment of the
openings of the expansion valves 24-1 to 24-4, in a configuration
in which temperatures of refrigerants in a plurality of routes,
which are introduced into the sample stage 4, are adjusted by the
refrigerant temperature adjustment section 21 including one direct
expansion-type heat cycle, even if the temperature of the
refrigerant in one route is changed, an effect of such change on
the temperature of the refrigerant in the other route can be made
to be small. Consequently, occurrence of hunting in adjustment of
temperatures of the refrigerant in the respective refrigerant
channels is suppressed, enabling efficient adjustment of the
temperatures or the evaporation temperatures of the refrigerants.
Also, even if such adjustment is made, the temperatures of the
refrigerants are adjusted while the refrigerant flow rates in both
routes are made to be equal to each other, decreasing the risk of
dry-out, which easily occurs when a refrigerant flow rate is
extremely reduced. Consequently, a distribution of temperatures in
a circumferential direction of the sample stage 4 and the sample 5
is reduced.
Variation 1
[0089] In the above-described embodiment of the present invention,
when temperatures of refrigerants in a plurality of routes are
adjusted, the refrigerant temperature in one route is changed while
the refrigerant temperature in the other route is maintained
constant. However, enhancement in throughput of semiconductor
manufacturing apparatuses demands quick adjustment of the
refrigerant temperatures, and therefore, there may be cases where
temperature adjustment quicker than the temperature adjustment
method indicated in the embodiment is needed. Still furthermore,
there may be cases where adjustment for quickly increasing or
decreasing a difference between the refrigerant temperatures in the
plurality of routes is needed. A variation for meeting such needs
will be described in below.
[0090] In the variation, a configuration for refrigerant
temperature adjustment in a plasma processing apparatus is similar
to that indicated in the embodiment. Then, when the openings of
expansion valves 24-1 to 24-4 are adjusted, openings V1 to V4 of
the expansion valves 24-1 to 24-4 are adjusted so as to satisfy the
following expression 3 below. In the present variation, the
expansion valves 24-1 to 24-4 have a configuration that is the same
as that of the embodiment.
V1=V4 and V2=V3 (3)
[0091] If the expression 3 is satisfied, both the expression 1 and
the expression 2 are satisfied. Thus, flow rates of refrigerants
introduced into a center-side refrigerant channel 20-1 and an outer
periphery-side refrigerant channel 20-2 are equal to each other,
and also are maintained equal to each other even under different
processing conditions. This point is the same as the embodiment;
however, if the openings of the expansion valves 24-1 to 24-4 are
adjusted so as to satisfy the expression 3, a temperature of a
refrigerant in one route is decreased when a temperature of a
refrigerant in the other route is increased, that is, the
temperatures in both routes are simultaneously changed in manners
opposite to each other.
[0092] A flowchart indicating change in opening of the expansion
valves 24-1 to 24-4 and change in refrigerant temperatures when the
above-described adjustment operation is employed in plasma etching
using three different refrigerant temperatures, that is, including
three steps is illustrated in FIG. 7. FIG. 7 includes time charts
indicating change in openings of the expansion valves and change in
refrigerant temperatures according to the variation of the
embodiment illustrated in FIG. 1. Here, (a) in FIG. 7 is a time
chart relating to refrigerant temperatures T1 and T2, (b) in FIG. 7
is a time chart relating to the opening V1 of the expansion valve
24-1 and the opening V3 of the expansion valve 24-3, and (c) in
FIG. 7 is a time chart relating to the opening V2 of the expansion
valve 24-2 and the opening V4 of the expansion valve 24-4.
[0093] In the Figure, first, in step 1 (S1) of the plasma etching,
if set temperatures for T1 and T2 are both 20.degree. C., each of
the openings of the expansion valves 24-1 to 24-4 is set to 50%
from the refrigerant temperatures and a rotation speed of a
compressor 22, based on the database in a control section 37.
[0094] Next, when the processing transitions from step 1 (S1) to
step 2 (S2) in which T1 and T2 are 25.degree. C. and 15.degree. C.,
respectively, in transition step 12 (S12) between these steps, V1
is increased while V3 is decreased in order to increase T1, and as
with the change in V1 and V3, V4 is increased while V2 is decreased
so as to satisfy the expression 3 in order to decrease T2.
Consequently, T1 is increased while T2 is decreased, and T1 and T2
are adjusted to the respective set temperatures in step 2 (S2).
[0095] In transition step 12 (S12), if it is determined that T1 and
T2 have reached the respective target temperatures (25.degree. C.
and 15.degree. C., respectively, in this case), it is determined
that transition step 12 (S12) has been completed, and step 2 (S2)
starts.
[0096] Next, when the processing transitions to step 3 (S3) in
which the set values for T1 and T2 are both 20.degree. C. after
completion of step 2 (S2), in transition step 23 (S23) between
these steps, V3 is increased while V1 is decreased, and as with the
change in V1 and V3, V4 is decreased while V2 is increased so as to
satisfy the expression 3. Consequently, T1 is decreased while T2 is
increased, whereby T1 and T2 are adjusted to the respective set
temperatures in step 3 (S3). In transition step 23 (S23), if it is
determined that T1 and T2 have reached target temperatures (both
20.degree. C. in this case), it is determined that transition step
23 (S23) has been completed, and step 3(S3) starts, and when the
step ends, the etching ends.
[0097] As a result of the above-described adjustment of the
openings of the expansion valves 24-1 to 24-4 being made, in a
configuration in which temperatures of refrigerants in a plurality
of routes, which are introduced into a sample stage 4, are adjusted
by a refrigerant temperature adjustment section 21 including one
direct expansion-type heat cycle, a difference between the
temperatures of the refrigerants in the plurality of routes can be
expanded or reduced in a shorter period of time. Also, even if the
temperature of the refrigerant in one route is changed, an effect
of such change on the temperature of the refrigerant in the other
route can be made to be small. Consequently, occurrence of hunting
in adjustment of the temperatures of the refrigerants in the
respective refrigerant channels is suppressed, enabling efficient
adjustment of the temperatures or evaporation temperatures of the
refrigerants. Also, when such adjustment is made, also, the
refrigerant temperature adjustment is made while the flow rates of
the refrigerants in both routes are made to be equal to each other,
decreasing the risk of dry-out, which easily occurs when a
refrigerant flow rate is extremely reduced. Consequently a
distribution of temperatures in a circumferential direction of a
sample stage 4 and a sample 5 is reduced.
Variation 2
[0098] In the above-described embodiment and variation, the
temperatures of the refrigerants introduced to the center-side
refrigerant channel 20-1 and the outer periphery-side refrigerant
channel 20-2 inside the sample stage 4 are adjusted only by
adjustment of the openings of the expansion valves 24-1 to 24-4.
However, in such case, a range of temperatures that can be provided
by adjustment may be small. For example, there is the problem that
the above-described embodiment and variation cannot respond to a
case where a refrigerant temperature that is lower than
temperatures provided only by adjustment of the openings of the
expansion valves 24-1 to 24-4 is needed.
[0099] Also, although in the adjustment of the expansion valves
24-1 to 24-4 indicated in the variation, it is possible to quickly
expand or reduce a difference between temperatures of the
refrigerants in the plurality of routes, there are temperature
conditions that cannot be met. For example, it is possible to
adjust T1 and T2 in both routes from 20.degree. C. in step 1 (S1)
to 25.degree. C. and 15.degree., respectively, as indicated in the
variation; however, it is difficult to adjust T1 and T2 to
25.degree. C. and 10.degree. C., respectively, only by the method
indicated in the variation.
[0100] Variation 2 of the embodiment of the present invention
responds to these problems. A configuration of an apparatus
according to variation 2 of the present invention will be described
with reference to FIG. 8. FIG. 8 is a vertical cross-sectional
diagram schematically illustrating a configuration of a refrigerant
temperature adjustment section according to another variation of
the embodiment illustrated in FIG. 1. The apparatus is one obtained
by addition of a main line 44, a bypass line 46 and a thermometer
40-3 between the condenser 23 and the bifurcation section 50 in the
configuration illustrated in FIG. 1. In the present variation,
also, expansion valves 24-1 to 24-4 have a configuration that is
the same as those in the embodiment. A refrigerant condensed in the
condenser 23 is introduced to the main line 44 or the bypass line
46. A valve 48-1 and a valve 48-2 are connected to the main line 44
and the bypass line 46, respectively, and flow rates of
refrigerants flowing in the lines are adjusted by opening/closing,
or increasing/decreasing openings of, the respective valves.
[0101] If the opening of the valve 48-1 is large and the opening of
the valve 48-2 is small, a majority of the refrigerant flows
through the main line 44. Meanwhile, if the opening of the valve
48-1 is small and the opening of the valve 48-2 is large, a
majority of the refrigerant flows through the bypass line 46. In
this case, the refrigerant flows through a capillary 42 provided
downstream of the valve 48-2. The capillary 42 is formed by a
narrow tube with a low conductance, and when the refrigerant flows
through the capillary 42, a pressure of the refrigerant is
decreased. In other words, where a majority of the refrigerant
flows through the bypass line 46, the pressure of the refrigerant
is decreased compared to a case where a majority of the refrigerant
flows through the main line 44, and as a result, a temperature of
the refrigerant is decreased.
[0102] A temperature of the refrigerant that has flowed through the
main line 44 and the bypass line 46 is measured by the thermometer
40-3. The temperature (also referred to as T3) measured by the
thermometer 40-3 subsequently serves as a base temperature for
temperatures T1 and T2 of the refrigerant finally determined by
adjustment of the expansion valves 24-1 to 24-4. The openings of
the valve 48-1 and the valve 48-2 are adjusted by an analysis
section 35 and a control section 37. As a result, flow rates of the
refrigerants flowing in the main line 44 and the bypass line 46 are
adjusted, and consequently, T3 is adjusted.
[0103] Where adjustment of the openings of the expansion valves
24-1 to 24-4 described in the above-described embodiment is
employed in the configuration illustrated in FIG. 8, in a
configuration in which temperatures of refrigerants in a plurality
of routes, which are introduced into a sample stage 4, are adjusted
by a refrigerant temperature adjustment section 21 including one
heat cycle, even if the temperature of the refrigerant in one route
is changed, an effect of such change on the temperature of the
refrigerant in the other route can be eliminated, and a refrigerant
temperature range can be widened by adjustment of the thermometer
40-3. For example, if it is desired to decrease set values for T1
and T2, it is only necessary to decrease the opening of the valve
48-1 and increase the opening of the valve 48-2. For such
adjustment, the valve 48-1 and the valve 48-2 are adjusted by the
analysis section 35 and the control section 37 to adjust T3, and
subsequently, T1 and T2 are finally adjusted by the expansion
valves 24-1 to 24-4.
[0104] Also, when adjustment of the openings of the expansion
valves 24-1 and 24-4 described in variation 1 is employed in the
configuration illustrated in FIG. 8 and it is desired to make set
temperatures for T1 and T2 be 25.degree. C. and 10.degree. C.,
respectively, such set temperatures can be provided by decreasing
the opening of the valve 48-1 and increasing the opening of the
valve 48-2 to decrease T3 and making V1 and V4 be larger and making
V2 and V3 be smaller compared to the conditions indicated in FIG. 7
to expand a temperature difference between T1 and T2.
[0105] As described above, even if the refrigerant temperature
adjustment method indicated in the above-described embodiment or
variation 1, the temperature range can be widened to the
low-temperature side.
[0106] As a result of any of the embodiment and the variations
described above, when a temperature adjustment section including
one direct expansion-type heat cycle is employed in a plasma
processing apparatus to adjust temperatures of respective
refrigerants in a plurality of routes, occurrence of hunting and/or
dry-out in refrigerant temperature adjustment can be
suppressed.
[0107] It should be further understood by those skilled in the art
that although the foregoing description has been made on
embodiments of the invention, the invention is not limited thereto
and various changes and modifications may be made without departing
from the spirit of the invention and the scope of the appended
claims.
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