U.S. patent application number 14/852127 was filed with the patent office on 2016-07-28 for plasma processing apparatus.
This patent application is currently assigned to HITACHI HIGH-TECHNOLOGIES CORPORATION. The applicant listed for this patent is Hitachi High-Technologies Corporation. Invention is credited to Shintarou NAKATANI, Tsunehiko TSUBONE.
Application Number | 20160217980 14/852127 |
Document ID | / |
Family ID | 56434154 |
Filed Date | 2016-07-28 |
United States Patent
Application |
20160217980 |
Kind Code |
A1 |
NAKATANI; Shintarou ; et
al. |
July 28, 2016 |
PLASMA PROCESSING APPARATUS
Abstract
Provided is a plasma processing apparatus including a processing
chamber which is disposed in a vacuum vessel and able to be
decompressed, a sample stage on a top surface of which a wafer to
be processed is mounted, an opening which is configured to supply a
heat-transfer gas to a gap between the wafer and the top surface of
the sample stage, a regulator which regulates a flow rate of the
heat-transfer gas, and a controller which regulates an operation of
the regulator based on a pressure of the gap detected using an
amount of the heat-transfer gas leaking from the regulator to the
processing chamber through the gap while the wafer is mounted on
the sample stage and an amount of the heat-transfer gas supplied
from the opening to the processing chamber while the wafer is not
mounted on the sample stage.
Inventors: |
NAKATANI; Shintarou; (Tokyo,
JP) ; TSUBONE; Tsunehiko; (Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi High-Technologies Corporation |
Tokyo |
|
JP |
|
|
Assignee: |
HITACHI HIGH-TECHNOLOGIES
CORPORATION
|
Family ID: |
56434154 |
Appl. No.: |
14/852127 |
Filed: |
September 11, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/32816 20130101;
H01J 37/32449 20130101; H01L 21/67109 20130101; H01L 21/67253
20130101; H01J 37/32724 20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32; H01L 21/67 20060101 H01L021/67 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 23, 2015 |
JP |
2015-010810 |
Claims
1. A plasma processing apparatus comprising: a processing chamber
which is disposed in a vacuum vessel and able to be decompressed; a
sample stage which is disposed in the processing chamber and on a
top surface of which a wafer to be processed is mounted; an opening
which is arranged on the top surface of the sample stage and
configured to supply a heat-transfer gas to a gap between the wafer
and the top surface of the sample stage while the wafer is mounted
on the top surface of the sample stage; a supply path which is
communicated with the opening and through which the heat-transfer
gas flows; a regulator which is disposed on the supply path and
regulates a flow rate of the heat-transfer gas; and a controller
which regulates an operation of the regulator based on a pressure
of the gap detected using an amount of the heat-transfer gas
leaking from the regulator to the processing chamber at an outer
circumference of the sample stage through the gap while the wafer
is mounted on the sample stage and an amount of the heat-transfer
gas supplied from the opening to the processing chamber while the
wafer is not mounted on the sample stage, wherein the plasma
processing apparatus processes the wafer using plasma formed in the
processing chamber while the heat-transfer gas is supplied to the
gap.
2. The plasma processing apparatus according to claim 1, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap using a result obtained by redetecting,
after a predetermined number of wafers are processed, the amount of
the heat-transfer gas leaking from the regulator to the processing
chamber at the outer circumference of the sample stage through the
gap while the wafer is mounted on the sample stage.
3. The plasma processing apparatus according to claim 1, further
comprising: a dielectric film which forms the top surface of the
sample stage and comprises an electrode attracting the wafer
mounted on the sample stage by static electricity, wherein the
opening is disposed on a top surface of the dielectric film.
4. The plasma processing apparatus according to claim 2, further
comprising: a dielectric film which forms the top surface of the
sample stage and comprises an electrode attracting the wafer
mounted on the sample stage by static electricity, wherein the
opening is disposed on a top surface of the dielectric film.
5. The plasma processing apparatus according to claim 1, wherein
the amount of the heat-transfer gas leaking from the regulator to
the processing chamber at the outer circumference of the sample
stage through the gap while the wafer is mounted on the sample
stage is detected using a sum of a volume in the supply path from
the regulator to the opening and a volume between the dielectric
film and a back surface of the wafer where the wafer is
mounted.
6. The plasma processing apparatus according to claim 2, wherein
the amount of the heat-transfer gas leaking from the regulator to
the processing chamber at the outer circumference of the sample
stage through the gap while the wafer is mounted on the sample
stage is detected using a sum of a volume in the supply path from
the regulator to the opening and a volume between the dielectric
film and a back surface of the wafer where the wafer is
mounted.
7. The plasma processing apparatus according to claim 3, wherein
the amount of the heat-transfer gas leaking from the regulator to
the processing chamber at the outer circumference of the sample
stage through the gap while the wafer is mounted on the sample
stage is detected using a sum of a volume in the supply path from
the regulator to the opening and a volume between the dielectric
film and a back surface of the wafer where the wafer is
mounted.
8. The plasma processing apparatus according to claim 4, wherein
the amount of the heat-transfer gas leaking from the regulator to
the processing chamber at the outer circumference of the sample
stage through the gap while the wafer is mounted on the sample
stage is detected using a sum of a volume in the supply path from
the regulator to the opening and a volume between the dielectric
film and a back surface of the wafer where the wafer is
mounted.
9. The plasma processing apparatus according to claim 1, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
10. The plasma processing apparatus according to claim 2, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
11. The plasma processing apparatus according to claim 3, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
12. The plasma processing apparatus according to claim 4, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
13. The plasma processing apparatus according to claim 5, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
14. The plasma processing apparatus according to claim 6, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
15. The plasma processing apparatus according to claim 7, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
16. The plasma processing apparatus according to claim 8, wherein
the controller regulates the operation of the regulator based on
the pressure of the gap detected using a pressure value in the
processing chamber during evacuation of the processing chamber
executed before processing of the wafer begins.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a plasma processing
apparatus and, more particularly, to a plasma processing apparatus
that regulates a temperature of a sample stage, onto which a sample
is mounted, to adjust a temperature of the sample to a suitable
temperature for processing and processes the sample.
[0002] A plasma etching processing apparatus such as a
semiconductor wafer processing apparatus supplies a process gas to
the inside of a processing vessel (hereinafter, referred to as a
vacuum vessel) decompressed down to a vacuum state to generate
plasma, mounts a wafer, which is an object to be processed, on a
sample stage for mounting a wafer (hereinafter, referred to as a
sample stage), and performs processings on a sample on the wafer.
The sample stage mainly has a function of adsorbing and holding the
wafer by electrostatic force, a function of controlling a
temperature of the wafer, and a function of applying a
radio-frequency bias voltage to the wafer to assist etching by
attracting ions in the plasma.
[0003] With regard to the wafer temperature control function by the
sample stage, technology for disposing a film-like heater in a film
arranged on a top surface of the sample stage and formed of a
dielectric material, disposing a coolant groove through which a
coolant circulates to remove heat from the heater of the top
surface of the sample stage, and implementing a desired temperature
distribution of the wafer with the heater to perform etching
processing of the sample on the wafer is considered as technology
for realizing sufficient speed responsiveness and temperature
precision. In the technology using the heater disposed at a
position adjacent to the sample, it is advantageous that the
temperature of the sample and its distribution can be changed
rapidly and a sufficient temperature change can be obtained even
when heat input from the plasma is small.
[0004] The in-plane temperature of the top surface of the sample
stage needs to be almost uniform in precision in a circumferential
direction; however, because the sample stage has a structure in
which a dielectric film, the heater, and a coolant flow channel are
combined, shapes and manufacturing methods of the individual
elements need to be devised
[0005] As such technology, one disclosed in JP-A-2009-218242 has
been known. In this document of the related technology, it is
disclosed that a heater is formed on a sample stage, and a
resistance value of the heater is regulated based on results of
detection of the distribution of the temperature when power is
supplied to the heater, so that a distribution of a temperature
becomes a predetermined one.
[0006] Also, in JP-A-2010-272873, technology for decreasing the
coolant flow rate to suppress increase of the heat transfer
coefficient of the coolant by adapting a coolant flow channel
cross-section of the coolant groove in the sample stage to be
different from other places in a region of a degree of dryness at
which a heat transfer coefficient increases, so that the heat
transfer coefficient of the coolant becomes uniform in a plane of
base material, is disclosed.
SUMMARY OF THE INVENTION
[0007] In the above related technologies, the following aspects are
not sufficiently considered and problems have arisen.
[0008] Namely, heat-transfer gas is often caused to flow in between
the dielectric layer of the sample stage and the wafer to
complement contact heat transfer between a back surface of the
wafer and a wafer adsorption surface of the sample stage and
further transmit a temperature of a surface other than the wafer
adsorption surface of the sample stage to the wafer. It is
considered that the methods disclosed in JP-A-2009-218242 and
JP-A-2010-272873 are effective in making the wafer surface
temperature uniform with respect to the heater and the coolant flow
channel forming the sample stage; however, a heat transfer effect
to the wafer by the heat-transfer gas needs to function so that the
temperature distribution becomes constant all the time of an
operation of the sample stage.
[0009] Particularly, in the wafer adsorption surface of the sample
stage, a wafer adsorption area may be decreased to minimize change
with time caused by plasma exposure or to reduce contamination on
the back surface of the wafer and in such the case, because a
heat-transfer gas distribution region becomes broad, an influence
of the heat transfer effect by the heat-transfer gas becomes
notable.
[0010] The heat transfer effect of the heat-transfer gas changes
depending on parameters such as a physical property, a flow rate, a
pressure, and a temperature of the heat-transfer gas and a
temperature and a surface property of the heat-transfer gas flow
channel. Among those, as for a surface of the heat-transfer gas
flow channel of the sample stage, minute errors in dimensions and a
surface roughness may be produced for each individual of
manufactured sample stages, so that a wafer surface temperature
distribution may be different for each individual.
[0011] Also, in the surface of the heat-transfer gas flow channel
of the sample stage, because change with time of the surface
property due to long-term plasma exposure is unavoidable, a problem
arises that the wafer surface temperature distribution would change
as a plurality of wafers are processed. For this reason, there has
been a possibility that desired processing results of the wafers
during processing can't be obtained and a yield is lowered. In the
above related technologies, these problems are not sufficiently
considered.
[0012] An object of the present invention is to provide a plasma
processing apparatus in which a yield is improved.
[0013] The above-described object is achieved by a plasma
processing apparatus that includes a processing chamber which is
disposed in a vacuum vessel and able to be decompressed; a sample
stage which is disposed in the processing chamber and on a top
surface of which a wafer to be processed is mounted, an opening
which is arranged on the top surface of the sample stage and
configured to supply a heat-transfer gas to a gap between the wafer
and the top surface of the sample stage while the wafer is mounted
on the top surface of the sample stage; a supply path which is
communicated with the opening and through which the heat-transfer
gas flows; a regulator which is disposed on the supply path and
regulates a flow rate of the heat-transfer gas; and a controller
which regulates an operation of the regulator based on a pressure
of the gap detected using an amount of the heat-transfer gas
leaking from the regulator to the processing chamber at an outer
circumference of the sample stage through the gap while the wafer
is mounted on the sample stage and an amount of the heat-transfer
gas supplied from the opening to the processing chamber while the
wafer is not mounted on the sample stage, wherein the plasma
processing apparatus processes the wafer using plasma formed in the
processing chamber while the heat-transfer gas is supplied to the
gap.
[0014] According to the present invention, when a processing
chamber is needed to be started up to get ready for processing of a
sample on a wafer and/or periodically after processing of samples
on wafers have been performed over a plurality of wafers, by
measuring a leak flow rate of a heat-transfer gas flow channel and
updating coefficients of a pressure control expression, a
heat-transfer gas pressure of the back side of the wafer can be
controlled constant at any target value and a heat transfer
coefficient by the heat-transfer gas can be made constant. From
above, a wafer surface temperature distribution can be maintained
constant without depending on an individual difference of a surface
property of a heat-transfer gas flow channel of each sample stage
or change with time of the surface property of the heat-transfer
gas flow channel after a plurality of wafers are processed.
[0015] 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 DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a longitudinal cross-section illustrating a
schematic configuration of a plasma processing apparatus according
to an embodiment of the present invention;
[0017] FIG. 2 is a longitudinal cross-section illustrating an
enlarged schematic configuration of a sample stage of the plasma
processing apparatus according to the embodiment illustrated in
FIG. 1;
[0018] FIG. 3 is a longitudinal cross-section illustrating an
enlarged schematic configuration of the vicinity of a dielectric
film of the sample stage of the plasma processing apparatus
according to the embodiment illustrated in FIG. 2;
[0019] FIG. 4 is a flowchart illustrating a flow of an operation of
the plasma processing apparatus according to the embodiment
illustrated in FIG. 1;
[0020] FIG. 5 is a longitudinal cross-section illustrating an
enlarged schematic configuration of the vicinity of the dielectric
film in a state in which a wafer is not mounted on the sample stage
of the plasma processing apparatus according to the embodiment
illustrated in FIG. 2;
[0021] FIG. 6 is a longitudinal cross-section illustrating an
enlarged schematic configuration of the vicinity of the dielectric
film in a state in which a wafer is mounted on the sample stage of
the plasma processing apparatus according to the embodiment
illustrated in FIG. 2; and
[0022] FIG. 7 is a flowchart illustrating a flow of an operation of
a plasma processing apparatus according to a modification of the
embodiment of the present invention.
DESCRIPTION OF THE EMBODIMENTS
[0023] Hereinafter, embodiments of the present invention are
described using the drawings.
[0024] An embodiment of the present invention is described using
the drawings.
[0025] FIG. 1 is a longitudinal cross-section illustrating a
schematic configuration of a plasma processing apparatus according
to an embodiment of the present invention. The apparatus includes a
vacuum vessel 100, an electromagnetic field supplying mechanism
that is circumferentially disposed over the vacuum vessel 100 and
supplies an electric field and a magnetic field to an inside of the
vacuum vessel 100, and an exhaust mechanism that is disposed below
the vacuum vessel 100 and evacuates the inside of the vacuum vessel
100.
[0026] A processing chamber 101 is disposed in the vacuum vessel
100, an RF power supply 110 which supplies a radio frequency wave
to an inside of the processing chamber 101 and a solenoid coil 109
which supplies an electromagnetic wave to the inside of the
processing chamber 101 are provided in the upper part of the vacuum
vessel 100; in the lower part of the vacuum vessel 100, a sample
stage 111 on a top surface of which a substrate-like sample of an
object to be processed such as a wafer is mounted and an exhaust
device including a turbo molecular pump 118 are provided.
[0027] The electromagnetic field supplying mechanism includes the
solenoid coil 109 that is disposed in the upper part the vacuum
vessel 100 and the RF power supply 110 that is disposed over the
vacuum vessel 100 and supplies an electromagnetic wave. The
electromagnetic wave supplied from the RF power supply 110
propagates through a waveguide 107 via an isolator not illustrated
in the drawings and a matching box 108 and, after passing through a
resonance space 106, is introduced into the processing chamber 101
through a quartz plate 105 and a shower plate 102.
[0028] The processing chamber 101 has an approximately cylindrical
shape and is a space where plasma is formed when plasma processing
is executed on a sample of a processing object.
[0029] A ceiling member of a cylindrical shape hermetically sealing
the processing chamber 101 is provided above the processing chamber
101; the ceiling member includes the quartz plate 105 formed of a
dielectric such as a quartz and the shower plate 102, and a fine
gap 103 is formed between the quartz plate 105 and the shower plate
102. The fine gap 103 is a space of a cylindrical shape and the
shower plate 102 is disposed below the space. In the shower plate
102, many small holes are provided as being arranged in a shape of
a plurality of concentric circles. A gas ring 104 is disposed on
the outer circumferential side of the shower plate 102 and the
quartz plate 105. A gas passage to supply a process gas to the fine
gap 103 is provided in the gas ring 104; the process gas is
supplied from a process gas supply 119 to the fine gap 103 through
a process gas supply piping 120 and the gas passage of the gas ring
104 and, thereafter, is dispersed equally to be supplied in the
processing chamber 101 through the multiple small holes provided in
the shower plate 102.
[0030] The sample stage 111 disposed below the processing chamber
101 has a cylindrical shape and a top surface of the sample stage
111 is covered with a dielectric film. In the sample stage 111, a
flow channel not illustrated in the drawings is disposed in a
concentric circle shape or a spiral shape, and a coolant a
temperature and/or a flow rate (flow speed) of which are regulated
by a temperature control unit 114 is introduced into the flow
channel. In addition, a heater not illustrated in the drawings is
disposed inside the dielectric film and the heater is supplied with
power by a heater power supply 117 to be heated.
[0031] A heat-transfer gas flow channel 112 is provided between the
dielectric film of the top surface of the sample stage 111 and a
back surface of a wafer 121 and a gas having good heat transfer
capability such as Lie is supplied from a heat-transfer gas supply
115 via a heat-transfer gas supply piping 122. A pressure value of
the heat-transfer gas is monitored at a disposition location of a
pressure control element 123.
[0032] In addition, on the top surface of the sample stage 111, a
dielectric film including a film-like electrode for electrostatic
chuck to adsorb the wafer 121 onto the sample stage 111 using
electrostatic force is disposed and the electrode for the
electrostatic chuck is electrically connected to a DC power supply
113 to apply a DC voltage thereto. Moreover, a metal electrode of a
disk shape to which RF power is supplied in order to form a bias
potential above a surface of the wafer 121 on the sample stage 111
during processing is disposed in the sample stage 111 and the
electrode is electrically connected to an RF bias power supply 116
which supplies the RF power.
[0033] With such the plasma etching processing apparatus, the wafer
121 on which a prescribed processing is executed is mounted on a
robot arm in a vacuum transfer chamber that is a different vacuum
vessel (not illustrated in the drawing) coupled to a sidewall of
the vacuum vessel 100 and includes a transfer mechanism such as the
robot arm disposed in a decompressed internal space, transferred to
the processing chamber 101, delivered to the sample stage 111 to be
mounted on a mounting surface of the top surface thereof, adsorbed
and held thereafter on the dielectric film by the electrostatic
force formed by the DC voltage supplied from the DC power supply
113.
[0034] Next, the process gas is introduced from the process gas
supply 119 to the fine gap 103 via the process gas supply piping
120 and is supplied into the processing chamber 101 through the
multiple small holes formed in the shower plate 102. The process
gas is turned into plasma by an interaction of an electromagnetic
wave passing through the resonance space 106 and introduced into
the processing chamber 101 via the quartz plate 105 and the shower
plate 102 and a magnetic field by the solenoid coil 109 and the
plasma is formed over the wafer 121. Furthermore, the RF power is
applied to the sample stage 111 by the RF bias power supply 116,
ions in the plasma are attracted onto the wafer 121 by a potential
difference between the bias potential by the RE bias formed over
the top surface of the wafer 121 and the plasma potential, and
processing starts while an etching reaction is assisted.
[0035] After completion of an etching processing, the plasma and
the RF bias are stopped, supply of the DC voltage from the DC power
supply 113 is stopped, and the electrostatic force becomes weak and
is removed.
[0036] Next, a detailed structure of the sample stage 111 is
described with reference to FIG. 2.
[0037] FIG. 2 is a longitudinal cross-section illustrating an
enlarged schematic configuration of the sample stage of the plasma
processing apparatus according to the embodiment illustrated in
FIG. 1. The sample stage 111 has a cylindrical shape or a disk
shape, and includes a base portion 201 that is formed of a metal
such as Ti, aluminum containing ceramic, molybdenum, and tungsten,
a first dielectric film portion 202 that is disposed as being
bonded to a top surface of the base portion 201 and is formed with
a dielectric such as Al.sub.2O.sub.3 including therein a heater
204, and a second dielectric film portion 206 that is disposed on
the first dielectric film 202 and is formed with a dielectric such
as Al.sub.2O.sub.3 including therein an electrode 205 for
electrostatic chuck formed of a metal such as tungsten. A through
hole 208 which a pin 210 for wafer lift penetrates is provided in
the sample stage 111.
[0038] The pin 210 is provided toward the lower part of the sample
stage 111, moves up and down relative to the sample stage 1 1 1
through the through hole 208, and delivers a wafer. The heater 204
is electrically connected to the heater power supply 117 through a
feeder structure not illustrated in the drawings. The electrode 205
for the electrostatic chuck is electrically connected to the DC
power supply 113 for the electrostatic chuck through the feeder
structure not illustrated in the drawings.
[0039] Inside the base portion 201, coolant grooves 203, which are
coolant passages through which a coolant circulates, and a
temperature sensor 207 which measures a temperature of a top
surface of the base are disposed.
[0040] As for the coolant grooves 203, an inlet part into which the
coolant is introduced and an outlet part from which it is
discharged are connected to the temperature control unit 114
outside the vacuum vessel 100 by a pipeline. The temperature
control unit 114 regulates a flow rate (flow speed) and/or a
temperature of the coolant passing through the coolant grooves 203
and circulating according to a command signal from a controller
211. The coolant flows through the coolant grooves 203 and cools
the base portion 201. The base portion 201 is cooled, so that the
wafer 121 held on the sample stage 111 is cooled.
[0041] For the temperature sensor 207, a thermocouple, a platinum
resistance thermometer, or the like is used. The temperature sensor
207 is disposed inside a hole 209. The temperature sensor 207 is
electrically connected to the controller 211.
[0042] The heat-transfer gas supply piping 122 is coupled to the
heat-transfer gas supply 115 and introduces the heat-transfer gas
above the sample stage 111. Below the heat-transfer gas supply
piping 122, the pressure control element 123 is disposed. The
pressure control element 123 is electrically connected to the
controller 211.
[0043] The wafer 121 is mounted on atop surface of the second
dielectric film portion 206 by an operation of a transfer mechanism
not illustrated in the drawings, the pin 210, or the like. Then,
power is supplied from the DC power supply 113 for the
electrostatic chuck to the electrode 205 for the electrostatic
chuck and the electrostatic force is formed. Thereby, the wafer is
adsorbed and held on the second dielectric film portion 206.
[0044] After the wafer 121 is adsorbed and held on the second
dielectric film portion 206, the bias potential is applied to the
wafer 121. When the wafer 121 is processed using the plasma, heat
input to the wafer 121 is accompanied. A rise of the temperature of
the wafer 121 according to this heat input greatly affects an
etching profile. For this reason, it is necessary to cool the wafer
121.
[0045] However, because the processing chamber 101 is decompressed,
heat transfer is insufficient only by mounting the wafer on the
sample stage 111. Therefore, the heat-transfer gas is introduced
between the second dielectric film portion 206 and the wafer 121
mounted on protrusions formed on the surface of the second
dielectric film portion 206 from the heat-transfer gas supply 115
through the heat-transfer gas supply piping 122. Thereby, a heat
transfer rate necessary between the wafer and the second dielectric
film portion 206 is secured and a temperature increase of the wafer
is suppressed.
[0046] Incidentally, in this embodiment, the heat-transfer gas is
regulated by the controller 211, such that its pressure value is
detected by the pressure control element 123, a command calculated
at the controller 211, which receives an output thereof, according
to the pressure value is sent, and a valve aperture is regulated to
render a pressure become a value within a target allowable range.
In addition, the controller 211 sends a command signal to a flow
rate control element disposed in a heat-transfer gas supply not
illustrated in the drawings and, as a result, an operation thereof
is regulated such that a flow rate of the heat-transfer gas
supplied becomes one in a prescribed allowable range.
[0047] In this embodiment, a method of controlling a pressure of
the heat-transfer gas is to regulate using a flow rate control
element not illustrated in the drawings, such that the pressure
value is made to be in the prescribed allowable range in the
pressure control element 123, or to calculate a pressure of a back
surface of the wafer 121 with a pressure relation expression
predetermined such that a value of the pressure of the back surface
of the wafer 121 is made to be in the prescribed allowable range
and to control the pressure by the pressure control element 123, or
to regulate by a combination thereof. First, in this embodiment, a
configuration to regulate the pressure of the heat-transfer gas
between the wafer 121 and the second dielectric film portion 206 is
described.
[0048] The temperature of the top surface of the base portion is
detected by the temperature sensor 207. The temperature detected by
the temperature sensor 207 is received by the controller 211. The
controller 211 can estimate based on the detected temperature of
the base portion 201 the temperature of the top surface of the
second dielectric film portion 206, which is a mounting surface, or
a temperature of the wafer 121 mounted thereon or its distribution
using an operation device in the controller 211 or using a program
stored in the controller 211 or an external storage medium such as
a hard disk connected such that communication is enabled.
[0049] The controller 211 operates and detects a power value to be
output by the heater power supply 117 according to a detection
result of the temperature of the second dielectric film portion 206
or the wafer 121 using a program stored previously in a storage
device. By sending a command to the heater power supply 117 to
output the power value, a calorific value of the heater 204 can be
controlled. As such, the detected temperature of the sample stage
111 is fed back to the controller 211, which is a control unit.
Thereby, the calorific value of the heater 204 is regulated and the
temperature of the wafer or its distribution optimal for processing
is realized.
[0050] FIG. 3 is a longitudinal cross-section illustrating an
enlarged schematic configuration of the vicinity of the dielectric
film of the sample stage of the plasma processing apparatus
according to the embodiment illustrated in FIG. 2. In particular,
it shows an enlarged view of a radial portion of the sample stage
111 illustrated in FIG. 2 in the vicinity of the wafer 121 and the
second dielectric film portion 206.
[0051] On the surface of the second dielectric film portion 206, an
adsorption surface 301 to mount the wafer 121 and the heat-transfer
gas flow channel 112 to circulate the heat-transfer gas are
provided. A flattening processing is normally executed on the
adsorption surface 301; however, because unevenness having a
surface roughness Ra of about 0.1 .mu.m is generated, circulation
of the heat-transfer gas occurs in the adsorption surface 301. As a
result, as illustrated in FIG. 3, a flow 302 of the heat-transfer
gas in a radial direction of the sample stage is generated and the
heat-transfer gas flows out from an outer circumferential edge of
the second dielectric film portion 206 to the processing chamber
101 side and is exhausted by the turbo molecular pump 118.
[0052] FIG. 4 illustrates a sequence flowchart according to the
embodiment of the present invention and a sequence is described in
detail below. FIGS. 5 and 6 are explanatory diagrams in the
flowchart of FIG. 4.
[0053] FIG. 4 is a flowchart illustrating a flow of an operation of
the plasma processing apparatus according to the embodiment
illustrated in FIG. 1. FIG. 5 is a longitudinal cross-section
illustrating an enlarged schematic configuration of the vicinity of
the dielectric film in a state in which the wafer is not mounted on
the sample stage of the plasma processing apparatus according to
the embodiment illustrated in FIG. 2. FIG. 6 is a longitudinal
cross-section illustrating an enlarged schematic configuration of
the vicinity of the dielectric film in a state in which a wafer is
mounted on the sample stage of the plasma processing apparatus
according to the embodiment illustrated in FIG. 2.
[0054] First, a sequence according to the embodiment of the present
invention in the case in which it is started up to get ready for
processing a wafer 121 after performing maintenance on the inside
of the processing chamber 101 is described. As illustrated in FIG.
4, first, at Block 401, while a processing of a wafer 121 has not
started and a wafer 121 is not mounted on the sample stage 111, the
inside of the processing chamber 101 is evacuated until the inner
portion of the processing chamber 101 has a pressure value of the
order of 10.sup.-5 Pa (a value of a pressure equivalent to or lower
than a pressure during the processing). In this state, at least
part of particles such as products formed in the processing chamber
101 during formerly performed processing of any wafers 121 and
adhered to an inner surface and a process gas, which exist inside
the processing chamber 101, are discharged to the outside of the
processing chamber 101 and the degree of cleanness of the
processing chamber 101 is improved.
[0055] Next, whereas a wafer 121 is not mounted on the sample stage
111, at Block 403, the heat-transfer gas is supplied from the
heat-transfer gas supply 115 into the heat-transfer gas flow
channel 112 of the sample stage 111. The above state is illustrated
in FIG. 5.
[0056] In FIG. 5, let a pressure detection point of the pressure
control element 123 be Point (A) and a place on an external surface
of the second dielectric film portion 206 on the mounting side of a
wafer 121 after passing through the heat-transfer gas flow channel
112 be Point (B). The heat-transfer gas passing through Point (B)
is discharged into the processing chamber 101 and is exhausted by
the turbo molecular pump 118. In the above state, after the
heat-transfer gas is supplied at a constant pressure monitored by
the pressure control element 123, the supply is stopped and a
variation amount AP of the pressure value of Point (A) until an
arbitrary time and an elapsed time .DELTA.t are measured. In
addition, a volume V.sub.0 of the heat-transfer gas flow channel
112 from Point (A) to Point (B) is obtained in advance and a leak
flow rate Q.sub.0 of the heat-transfer gas discharged from Point
(B) is calculated by the following expression (1) from the time
variation of the measured pressure value of Point (A) and the
volume V.sub.0 from Point (A) to Point (B).
Q 0 = .DELTA. P V 0 .DELTA. t . ( 1 ) ##EQU00001##
[0057] From the calculated leak flow rate Q.sub.0 above, any
pressure value P.sub.1 of Point (A), and a pressure value P.sub.3
of the processing chamber 101 in the above state, assuming
P.sub.3=P.sub.2 since P.sub.3 is almost equal to a pressure P.sub.2
of Point (B), a conductance C.sub.0 between Point (A) and Point (B)
is calculated by the following expression (2).
C 0 = Q 0 P 1 - P 2 . ( 2 ) ##EQU00002##
[0058] In addition, once the expression (2) is arranged for
P.sub.2, the following expression (3) is obtained.
P 2 = P 1 - Q 0 C 0 . ( 3 ) ##EQU00003##
[0059] If it is considered that the conductance C.sub.0 from Point
(A) to Point (B) is rarely affected by change with time due to
plasma exposure, P.sub.2 becomes smaller than P.sub.1 by a fixed
value Q.sub.0/C.sub.0 once Q.sub.0 and C.sub.0 are measured.
[0060] Next, at Block 404, a wafer 121 is transferred to the inside
of the processing chamber 101 and mounted on the sample stage 111.
Then, by applying a DC voltage to the electrode 205 for the
electrostatic chuck, the wafer 121 is electrostatically adsorbed
onto the second dielectric film portion 206. Here, a front surface
property of the wafer 121 electrostatically adsorbed onto the
second dielectric film portion 206 may not be the same as that of a
product wafer; however, the back surface properties need to be
equivalent to each other.
[0061] In the above state, at Block 405, the heat-transfer gas is
supplied from the heat-transfer gas supply 115 to the heat-transfer
gas flow channel 112 of the sample stage 111. The above state is
illustrated in FIG. 6.
[0062] In FIG. 6, let the pressure detection point of the pressure
control element 123 be Point (A), the place on the external surface
of the second dielectric film portion 206 on the mounting side of
the wafer 121 after passing through the heat-transfer gas flow
channel 112 be Point (B), and a place where the heat-transfer gas
flows in a direction illustrated in 302 and reaches an outer
circumferential edge of the second dielectric film portion 206 be
Point (C). The heat-transfer gas passing through Point (C) is
discharged into the processing chamber 101 and is exhausted by the
turbo molecular pump 118.
[0063] In the above state, after the heat-transfer gas is supplied
at the constant pressure monitored by the pressure control element
123, the supply is stopped and a variation amount AP of the
pressure value of Point (A) until an arbitrary time and an elapsed
time At are measured. In addition, a volume V.sub.1 of the
heat-transfer gas flow channel 112 from Point (A) to Point (C) is
obtained in advance and a leak flow rate Q.sub.1 of the
heat-transfer gas discharged from Point (C) is calculated by the
following expression (4) from the time variation of the measured
pressure value of Point (A) and the volume V.sub.1 from Point (A)
to Point (C)
Q 1 = .DELTA. P V 1 .DELTA. t . ( 4 ) ##EQU00004##
[0064] From the calculated leak flow rate Q.sub.1 above, any
pressure value P.sub.1 of Point (A), any pressure value P.sub.2 of
Point (B), and the pressure value P.sub.3 of the processing chamber
101 in the above state, a conductance C.sub.1 between Point (B) and
Point (C) is calculated by the following expression (5)
C 1 = Q 1 P 2 - P 3 . ( 5 ) ##EQU00005##
[0065] Next, a process at Block 406 is described below. From the
obtained conductance C.sub.0 and C.sub.1, a total conductance C
from Point (A) to Point (C) is as represented by the following
expression (6)
C = C 0 C 1 C 0 + C 1 = Q 0 Q 1 ( P 2 - P 3 ) Q 0 + ( P 1 - P 2 ) Q
1 . ( 6 ) ##EQU00006##
[0066] Here, letting a flow rate from Point (A) to Point (C) be Q,
a relation of the following expression (7) holds
Q=C(P.sub.1-P.sub.3) (7)
[0067] When the expression (6) is substituted into the expression
(7) and a expression is arranged for P.sub.2, the following
expression (8) is obtained.
P 2 = ( Q 0 - Q ) Q 1 ( Q 0 - Q 1 ) Q P 1 + ( Q - Q 1 ) Q 0 ( Q 0 -
Q 1 ) Q P 3 . ( 8 ) ##EQU00007##
[0068] In the expression (8), because Q.sub.0 and Q.sub.1 are
known, it yields a relational expression of the variables P.sub.2,
P.sub.1, P.sub.3, and Q. Here, if P.sub.3 is assumed to be a fixed
value at a pressure value at the time of high vacuum exhaust at
Block 401 and Q is also assumed to be any fixed value, it becomes a
relational expression of the variables P.sub.1 and P.sub.2 and
P.sub.2 can be controlled by monitoring and adjusting P.sub.1.
[0069] Next, a sequence according to the embodiment of the present
invention in a state in which the surface property of the second
dielectric film portion 206 of the sample stage 111 is exposed to
the plasma and is changed after a plurality of wafers 121 are
processed in the processing chamber 101 is described.
[0070] At Block 407, when the number of processed wafers 121
reaches a prescribed number, the leak flow rate Q.sub.1 in FIG. 6
is measured again The prescribed number is the number in which the
change with time of the surface property of the second dielectric
film portion 206 does not affect an unallowable change of the
temperature distribution of the wafer 121 or the number when the
change with time of the surface property of the second dielectric
film portion 206 starts to affect the unallowable change of the
temperature distribution of the wafer 121; the specific number to
be processed is different depending on outcomes of the surface of
the second dielectric film portion 206 and the back surface of the
wafer 121, a plasma density, gas species, and gas flow rates of the
processing chamber 101, and the like.
[0071] At Block 408, when the processing of wafers 121 is continued
in the processing chamber 101, in order to measure the leak flow
rate Q.sub.1 again after processing of the wafers of the defined
number described at Block 407, the sequence from Block 401 to Block
406 is executed. However, as seen in Block 402, because the leak
flow rate Q.sub.0 in a state in which a wafer 121 does not exist is
already measured, the measurement is omitted.
[0072] From above, even when the surface property of the second
dielectric film portion 206 changes with time, by re-measuring the
leak flow rate Q.sub.1 and updating coefficient values of the above
expression (8), consistency between the expression (8) and the
surface property of the second dielectric film portion 206 is
secured and P.sub.2 can be controlled.
[0073] In the embodiment described above, the leak flow rate
Q.sub.0 is measured only once when the apparatus is started up such
that it becomes ready to process a wafer 121 after the inside of
the processing chamber 101 is maintained; however, let's consider
the case in which the surface property of the inner wall of the
heat-transfer gas flow channel 112 changes due to exposure to the
plasma for a reason such as a diameter of the heat-transfer gas
flow channel 112 being large. In the above case, it is necessary to
re-measure Q.sub.0 when the leak flow rate Q.sub.1 is measured
again and a modification of the embodiment is described below.
[0074] FIG. 7 shows a sequence flowchart according to a
modification of the embodiment. FIG. 7 is a flowchart illustrating
a flow of an operation of a plasma processing apparatus according
to the modification of the embodiment of the present invention.
[0075] In the figure, first, a sequence according to the
modification of the embodiment of the present invention is
described in the case in which the apparatus is started up to get
ready for processing a wafer 121 after the inside of the processing
chamber 101 is maintained.
[0076] First, at Block 701, while a wafer 121 is not mounted on the
sample stage 111 evacuation is performed until a pressure in the
processing chamber 101 becomes to the order of 10.sup.-5 Pa. Next,
while a wafer 121 is not mounted on the sample stage 111, at Block
702, the heat-transfer gas is supplied from the heat-transfer gas
supply 115 to the heat-transfer gas flow channel 112 of the sample
stage 111.
[0077] In FIG. 5, let a pressure detection point of the pressure
control element 123 be Point (A) and a place on an external surface
of the second dielectric film portion 206 on the mounting side of a
wafer 121 after passing through the heat-transfer gas flow channel
112 be Point (B). The heat-transfer gas passing through Point (B)
is discharged into the processing chamber 101 and is exhausted by
the turbo molecular pump 118. In the above state, after the
heat-transfer gas is supplied at a constant pressure monitored by
the pressure control element 123, the supply is stopped and a
variation amount .DELTA.P of the pressure value of Point (A) until
an arbitrary time and an elapsed time At are measured. In addition,
a volume V.sub.0 of the heat-transfer gas flow channel 112 from
Point (A) to Point (B) is obtained in advance and a leak flow rate
Q.sub.0 of the heat-transfer gas discharged from Point (B) is
calculated by the following expression (9) from the time variation
of the measured pressure value of Point (A) and the volume V.sub.0
from Point (A) to Point (B).
Q 0 = .DELTA. P V 0 .DELTA. t . ( 9 ) ##EQU00008##
[0078] From the calculated leak flow rate Q.sub.0 above, any
pressure value P.sub.1 of Point (A), and a pressure value P.sub.3
of the processing chamber 101 in the above state, assuming
P.sub.1=P.sub.2 since P.sub.3 is almost equal to a pressure P.sub.2
of Point (B), a conductance C.sub.0 between Point (A) and Point (B)
is calculated by the following expression (10)
C 0 = Q 0 P 1 - P 2 . ( 10 ) ##EQU00009##
[0079] In addition, once the expression (10) is arranged for
P.sub.2, the following expression (11) is obtained.
P 2 = P 1 - Q 0 C 0 . ( 11 ) ##EQU00010##
[0080] Next, at Block 703, a wafer 121 is transferred to the inside
of the processing chamber 101 and mounted on the sample stage 111.
Then, by applying a DC voltage to the electrode 205 for the
electrostatic chuck, the wafer 121 is electrostatically adsorbed
onto the second dielectric film portion 206. Here, a front surface
property of the wafer 121 electrostatically adsorbed onto the
second dielectric film portion 206 may not be the same as that of a
product wafer; however, the back surface properties need to be
equivalent to each other.
[0081] In the above state, at Block 704, the heat-transfer gas is
supplied from the heat-transfer gas supply 115 to the heat-transfer
gas flow channel 112 of the sample stage 111. In FIG. 6, let the
pressure detection point of the pressure control element 123 be
Point (A), the place on the external surface of the second
dielectric film portion 206 on the mounting side of the wafer 121
after passing through the heat-transfer gas flow channel 112 be
Point (B), and a place where the heat-transfer gas flows in a
direction illustrated in 302 and reaches an outer circumferential
edge of the second dielectric film portion 206 be Point (C). The
heat-transfer gas passing through Point (C) is discharged into the
processing chamber 101 and is exhausted by the turbo molecular pump
118. In the above state, after the heat-transfer gas is supplied at
the constant pressure monitored by the pressure control element
123, the supply is stopped and a variation amount .DELTA.P of the
pressure value of Point (A) until an arbitrary time and an elapsed
time .DELTA.t are measured. In addition, a volume V.sub.1 of the
heat-transfer gas flow channel 112 from Point (A) to Point (C) is
obtained in advance and a leak flow rate Q.sub.1 of the
heat-transfer gas discharged from Point (C) is calculated by the
following expression (12) from the time variation of the measured
pressure value of Point (A) and the volume V.sub.1 from Point (A)
to Point (C).
Q 1 = .DELTA. P V 1 .DELTA. t . ( 12 ) ##EQU00011##
[0082] From the calculated leak flow rate Q.sub.1 above, any
pressure value P.sub.1 of Point (A), any pressure value P.sub.2 of
Point (B), and the pressure value P.sub.3 of the processing chamber
101 in the above state, a conductance C.sub.1 between Point (B) and
Point (C) is calculated by the following expression (13).
C 1 = Q 1 P 2 - P 3 . ( 13 ) ##EQU00012##
[0083] Next, a process at Block 705 is described below From the
obtained conductance C.sub.0 and C.sub.1, a total conductance C
from Point (A) to Point (C) is as represented by the following
expression (14).
C = C 0 C 1 C 0 + C 1 = Q 0 Q 1 ( P 2 - P 3 ) Q 0 + ( P 1 - P 2 ) Q
1 . ( 14 ) ##EQU00013##
[0084] Here, letting a flow rate from Point (A) to Point (C) be Q,
a relation of the following expression (15) holds.
Q=C(P.sub.1-P.sub.3) (15).
[0085] When the expression (14) is substituted into the expression
(15) and a expression is arranged for P.sub.2, the following
expression (16) is obtained.
P 2 = ( Q 0 - Q ) Q 1 ( Q 0 - Q 1 ) Q P 1 + ( Q - Q 1 ) Q 0 ( Q 0 -
Q 1 ) Q P 3 . ( 16 ) ##EQU00014##
[0086] In the expression (16), because Q.sub.0 and Q.sub.1 are
known, it yields a relational expression of the variables P.sub.2,
P.sub.1, P.sub.3, and Q. Here, if P.sub.3 is assumed to be a fixed
value at a pressure value at the time of high vacuum exhaust at
Block 701 and Q is also assumed to be any fixed value, it becomes a
relational expression of the variables P.sup.1 and P.sub.2 and
P.sub.2 can be controlled by monitoring and adjusting P.sub.1.
[0087] Next, a sequence according to the modification of the
embodiment of the present invention in a state in which the surface
property of the second dielectric film portion 206 of the sample
stage 111 is exposed to the plasma and is changed after a plurality
of wafers 121 are processed in the processing chamber 101 is
described.
[0088] At Block 706, when the number of processed wafers 121
reaches a prescribed number, the leak flow rate Q.sub.0 in FIG. 5
and the leak flow rate Q.sub.1 in FIG. 6 are measured again. The
prescribed number is the number in which the change with time of
the surface properties of the heat-transfer gas flow channel 112
and/or the second dielectric film portion 206 do not affect an
unallowable change of the temperature distribution of the wafer 121
or the number when the change with time of the surface properties
of the heat-transfer gas flow channel 112 and/or the second
dielectric film portion 206 start to affect the unallowable change
of the temperature distribution of the wafer 121; the specific
number to be processed is different depending on outcomes of the
surface of the second dielectric film portion 206 and the back
surface of the wafer 121, a plasma density, gas species, and gas
flow rates of the processing chamber 101, and the like.
[0089] At Block 707, when the processing of wafers 121 is continued
in the processing chamber 101, in order to measure the leak flow
rates Q.sub.0 and Q.sub.1 again after processing of the wafers of
the defined number described at Block 706, the sequence from Block
701 to Block 705 is executed.
[0090] From above, even when the surface property of the second
dielectric film portion 206 changes with time, by re-measuring the
leak flow rates Q.sub.0 and Q.sub.1 and updating coefficient values
of the above expression (16), consistency between the expression
(16) and the surface properties of the heat-transfer gas flow
channel 112 and the second dielectric film portion 206 is secured
and P.sub.2 can be controlled.
[0091] The present invention is not limited to the plasma etching
processing apparatus described above and can be applied to general
plasma processing apparatuses including a plasma CVD apparatus
suitable for ion implantation or sputtering processing.
[0092] 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.
* * * * *