U.S. patent application number 12/206021 was filed with the patent office on 2009-12-31 for plasma processing apparatus and plasma processing method.
Invention is credited to Hiroho Kitada, Yutaka Kouzuma, Yutaka Omoto, Yosuke Sakai, Tsunehiko Tsubone, Mamoru Yakushiji, Ken Yoshioka.
Application Number | 20090321017 12/206021 |
Document ID | / |
Family ID | 41445990 |
Filed Date | 2009-12-31 |
United States Patent
Application |
20090321017 |
Kind Code |
A1 |
Tsubone; Tsunehiko ; et
al. |
December 31, 2009 |
Plasma Processing Apparatus and Plasma Processing Method
Abstract
There is disclosed a plasma processing apparatus wherein a
sample placed on the top surface of the sample table located within
the processing chamber contained in a vacuum vessel is processed
with plasma formed in the processing chamber, comprising a set of
ducts cut within the sample table through which cooling medium
flows; a film-shaped heater whose heating elements are
concentrically embedded in the dielectric film serving as the top
surface of the sample table; plural temperature controllers which
set up the temperature of the cooling medium flowing through the
ducts at different values, respectively; and a control unit which
switches over the circulations through the ducts of the cooling
medium supplied from the plural temperature controllers.
Inventors: |
Tsubone; Tsunehiko; (Hikari,
JP) ; Kitada; Hiroho; (Kudamatsu, JP) ; Sakai;
Yosuke; (Kudamatsu, JP) ; Yoshioka; Ken;
(Hikari, JP) ; Omoto; Yutaka; (Hikari, JP)
; Yakushiji; Mamoru; (Shunan, JP) ; Kouzuma;
Yutaka; (Kudamatsu, JP) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET, SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
41445990 |
Appl. No.: |
12/206021 |
Filed: |
September 8, 2008 |
Current U.S.
Class: |
156/345.27 |
Current CPC
Class: |
H01J 2237/2001 20130101;
H01L 21/67248 20130101; H01L 21/6719 20130101; H01L 21/67109
20130101; H01L 21/6831 20130101 |
Class at
Publication: |
156/345.27 |
International
Class: |
C23F 1/00 20060101
C23F001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 27, 2008 |
JP |
2008-168048 |
Claims
1. A plasma processing apparatus wherein a sample placed on the top
surface of the sample table located within the processing chamber
contained in a vacuum vessel is processed with plasma formed in the
processing chamber, comprising a set of ducts cut within the sample
table through which cooling medium flows; a film-shaped heater
whose heating elements are concentrically embedded in the
dielectric film serving as the top surface of the sample table;
plural temperature controllers which set up the temperature of the
cooling medium flowing through the ducts at different values,
respectively; and a control unit for switching over from the
circulation through the ducts of the cooling medium fed out of one
of the plural temperature controllers to the circulation through
the ducts of the cooling medium fed out of another temperature
controller.
2. A plasma processing apparatus as claimed in claim 1, wherein the
switchover of the circulations takes place in each interval between
the two successive processes for treating films of different
types.
3. A plasma processing apparatus as claimed in claim 1, wherein the
film-shaped heater embedded in the dielectric film is made up with
plural heater elements which can be independently controlled in
heating.
4. A plasma processing apparatus as claimed in claim 1, wherein the
sample table is provided with plural independent sets of concentric
ducts and the circulations of cooling medium are switched over
between the plural temperature controllers and the plural
independent sets of concentric ducts.
5. A plasma processing method wherein the film in the top surface
of a sample placed on the sample table located within the
processing chamber contained in a vacuum vessel and provided with a
film-shaped heater whose heating elements are concentrically
embedded in the dielectric film serving as the top surface of the
sample table, is processed with plasma formed in the processing
chamber, and wherein the circulations through the concentric ducts,
cut within the sample table, of the cooling medium fed out of the
plural temperature controllers which can set up the temperature of
the cooling medium fed through the concentric ducts at different
values, are switched over while the wafer is being heated by the
film-shaped heater.
6. A plasma processing method as claimed in claim 5, wherein the
circulations are switched over in each interval between the two
successive processes for treating films of different types.
7. A plasma processing apparatus as claimed in claim 5, wherein the
sample is processed while the temperature distribution in the wafer
is controlled by operating the film-shaped heater made up with
plural heater elements laid out concentrically in the dielectric
film.
8. A plasma processing apparatus as claimed in claim 5, wherein
plural independent sets of concentric ducts are cut within the
sample table, and the circulations of cooling medium fed out of the
plural temperature controllers are switched over between the plural
independent sets of concentric ducts and the plural temperature
controllers.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to a plasma processing apparatus and
a plasma processing method, for etching a disc-shaped sample such
as a semiconductor wafer in a processing chamber with plasma formed
in the processing chamber contained in a vacuum vessel, and more
particularly to a plasma processing apparatus and a plasma
processing method, that can continuously process the film, which is
the object of treatment, deposited on the top surface of the sample
under different conditions while the temperature of the sample
supported fixedly on the top surface of the sample table is being
controlled.
[0002] Recently, further reduction in the sizes of circuit patterns
formed on a semiconductor wafer has become an everlasting
requirement with the demand of increasing the scale of integration
of semiconductor elements. Accordingly, more and more strict
precision has been required in fabricating such fine circuit
patterns. Under these circumstances, it is very important to manage
the temperature of the wafer (semiconductor wafer) under etching
process.
[0003] In etching a wafer with plasma, for example, it is customary
to apply a bias voltage to the wafer so that anisotropic patterns
may be formed by bombarding the wafer with ions accelerated by the
electric field resulted from the application of the bias voltage.
During this etching process, the wafer absorbs heat and its
temperature rises.
[0004] The temperature rise in the wafer influences the effect of
etching. For example, in the etching of poly-silicon that serves as
electrodes for semiconductor devices, the final line width obtained
is largely affected by the re-adhesion of reactive products and/or
the deposition of adhesive radicals, on the side walls of the
etched patterns during etching process, and the degree of adhesion
of these substances varies with the wafer temperature.
Consequently, without the proper management of temperature in a
wafer during etching process, etching will not be uniform within
the treated surface of the wafer and also the reproducibility of
uniform wafers will be poor. Further, since there is a tendency
that the density of distributed reactive products is lower near the
periphery of the wafer than around the center of the wafer, it is
necessary to positively control the temperature distribution in the
wafer in order to obtain uniform line width (CD) within the treated
surface of the wafer.
[0005] In order to provide such control of temperature distribution
as described above, it is required to control the distribution of
the temperature in the wafer supporting surface of the sample table
for supporting the semiconductor wafer as a sample thereon, in such
a manner that the temperature distribution over the wafer surface
may be as desired. To meet this requirement, techniques have been
proposed for controlling the temperature of and its distribution
in, the material with which the internal and the sample supporting
surface, of the sample table for supporting the semiconductor wafer
thereon are formed. Such techniques are disclosed in, for example,
JP-A-2006-140455, JP-A-2007-067036, and JP-A-2007-300119.
[0006] JP-A-2006-140455 and JP-A-2007-067036 disclose a plasma
processing apparatus wherein a sheet-like member of dielectric
material for directly supporting the sample thereon is placed on
the sample table; the sheet-like member has a heater for heating
the wafer and an electrode for attracting the wafer to the
sheet-like member by electrostatic force, embedded therein; and a
disc-like metal member forming the internal of the sample table has
concentric ducts through which heat exchange medium flows cut
therein so that the temperature of the sample table may be
controlled as desired through the heat exchange between the
disc-like metal member and the heat exchange medium flowing through
the ducts cut in the disc-like metal member. According to the
conventional art, the temperature of and its distribution in, the
sample table or the wafer placed thereon are controlled as desired
by suitably controlling the extent to which the heater generates
heat and the heat exchange medium is cooled. On the other hand,
JP-A-2007-300119 discloses a plasma processing apparatus having a
sample table in the form of a disc, in which cooling fluid ducts
and a heater are provided so that the temperature of and its
distribution in, the sample is controlled as in JP-A-2006-140455
and JP-A-2007-067036.
SUMMARY OF THE INVENTION
[0007] The related art described above came to suffer a problem
since there was insufficient consideration regarding the following
points. With the demands for the microscopic patterning of
circuits, an increasing number of materials came to be used as
films on the wafer in the surface of which fine circuit patterns
are formed, and processing must be performed continuously on plural
types of films or under plural working conditions. Therefore, the
range of temperatures at which the wafer must be maintained came to
be broadened and the high precision in temperature control must
also be attained.
[0008] In the adjustment of temperature of the disc-like member by
the cooling medium flowing through the disc-like member provided in
the sample table, since the heat capacities of the cooling medium
and the disc-like member are much larger than that of the wafer,
the temperature of or its distribution in, the wafer can be
stabilized. However, if the heater is located nearer to the wafer
than to the cooling medium ducts, response in heat transfer is
indeed high enough, but temperature distribution in the wafer
supporting surface or the wafer seems to become uneven to a great
extent due to the unevenness in the local generation of heat (i.e.
heat generation distribution) by the heater. Because of this
tendency, if the range of attainable temperatures is expanded by
increasing the heat generated by the heater, the temperature value
of and the unevenness of temperature distribution in, the wafer
become greater with the elevation of temperature resulting from the
increase in heating amount. This is a problem to be overcome.
[0009] On the other hand, if the range of change in the temperature
of the cooling medium flowing within the sample table is expanded,
the unevenness of temperature distribution in the wafer can indeed
be reduced but the operational response will be much slower, as
compared with the case where heaters are used. In the case of a
multi-step process where the wafer, once transferred into the
processing chamber and placed fixedly on the sample table, is
subjected to successive processing steps under different processing
conditions without being transferred out of the processing chamber,
the time required for the change in the processing condition
prolongs with the increase in the number of the processing steps.
This causes a low throughput leading to an impairment of
manufacturing efficiency, resulting in a problem.
[0010] The conventional related art mentioned above has not taken
this problem into consideration, and it has been difficult with the
conventional related art to perform processing with high precision
and high productivity.
[0011] The object of this invention is to provide a plasma
processing apparatus and a plasma processing method, that can
provide a high productivity.
[0012] The object of this invention can be attained with, for
example, a plasma processing apparatus wherein a sample placed on
the top surface of the sample table located within the processing
chamber contained in a vacuum vessel is processed with plasma
formed in the processing chamber, comprising a set of ducts cut
within the sample table through which cooling medium flows; a
film-shaped heater whose heating elements are concentrically
embedded in the dielectric film serving as the top surface of the
sample table; plural temperature controllers for setting up the
temperature of the cooling medium flowing through the ducts at
different values, respectively; and a control unit for switching
over from the circulation through the ducts of the cooling medium
fed out of one of the plural temperature controllers to the
circulation through the ducts of the cooling medium fed out of
another temperature controller.
[0013] The object of this invention can also be attained by, for
example, switching the above mentioned circulations in each
interval between the two successive processes for treating films of
different types. The object of this invention can further be
attained by, for example, making up the film-shaped heater with
plural heater elements which can be independently controlled in
heating. The object of this invention can still further be attained
by, for example, providing the sample table with plural independent
sets of concentric ducts and switching the circulations of cooling
media fed out of plural temperature controllers through the plural
independent sets of concentric ducts.
[0014] The object of this invention can be attained by using a
plasma processing method, for example, wherein the film in the top
surface of a sample placed on the sample table located within the
processing chamber contained in a vacuum vessel and having a
film-shaped heater whose heating elements are concentrically
embedded in the dielectric film serving as the top surface of the
sample table, is processed with plasma formed in the processing
chamber, and wherein the circulations through the concentric ducts,
cut within the sample table, of the cooling medium fed out of the
plural temperature controllers which can set up at different values
the temperatures of the cooling media fed through the concentric
ducts, are switched over while the wafer is being heated by the
film-shaped heater.
[0015] The object of this invention can also be attained by using a
plasma processing method, for example, wherein the above mentioned
circulations are switched over in each interval between the two
successive processes for treating films of different types. The
object of this invention can further be attained by using a plasma
processing method, for example, wherein the sample is processed
while the temperature distribution in the wafer is controlled by
operating the film-shaped heater made up with plural heater
elements laid out concentrically in the dielectric film. The object
of this invention can still further be attained by using a plasma
processing method, for example, wherein the sample table is
furnished with plural independent sets of concentric ducts, and the
circulations of cooling media fed out of plural temperature
controllers are switched over between the plural independent sets
of concentric ducts and the plural temperature controllers.
[0016] 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
[0017] FIG. 1 schematically shows in plan view the structure of a
vacuum processing apparatus provided with a plasma processing
apparatus as an embodiment of this invention;
[0018] FIG. 2 shows in vertical cross section the structure of the
processing unit shown in FIG. 1;
[0019] FIG. 3 schematically shows in vertical cross section the
structure of the sample table used in the processing unit shown in
FIG. 2;
[0020] FIG. 4 graphically shows an example of how the plasma
processing performed with the apparatus shown in FIG. 2 proceeds
with time; and
[0021] FIG. 5 graphically shows another example of how the plasma
processing performed with the apparatus shown in FIG. 2 proceeds
with time.
DETAILED DESCRIPTION OF THE EMBODIMENT
[0022] An embodiment of this invention will be described in detail
below in reference to the attached drawings.
Embodiment 1
[0023] The embodiment of this invention will be described in
reference to FIGS. 1 through 5.
[0024] FIG. 1 schematically shows in plan view the structure of a
vacuum processing apparatus provided with a plasma processing
apparatus as an embodiment of this invention. In FIG. 1, the vacuum
processing apparatus 100 can be split into two blocks, front block
and rear block. The front block shown as the lower part of the
vacuum processing apparatus 100 shown in FIG. 1 is the atmospheric
pressure block 101 in which a wafer as a sample to be processed is
introduced and conveyed under the atmospheric pressure.
[0025] The rear block shown as the upper part of the vacuum
processing apparatus 100 shown in FIG. 1 is the processing block
102. The processing block 102 comprises processing units 103, 103',
104 and 104', each of which has a processing chamber wherein a
wafer conveyed from the atmospheric pressure block 101 is brought
in and processed in a vacuum environment; a vacuum transfer vessel
112 whose internal is maintained in a vacuum condition and via
which the wafer is transferred into the processing chamber; and
plural lock chambers 113, 113' for communicating between the vacuum
transfer vessel 112 and the atmospheric pressure block 101. These
units can be maintained at reduced pressures or in a high vacuum
condition and therefore the processing block 102 may be called a
vacuum block.
[0026] On the other hand, the atmospheric pressure block 101
includes a roughly parallelepiped casing 108 with a transfer robot
(not shown) installed therein. The casing 108 has plural cassette
tables (only three of them are shown) 109 attached to the front
wall of the casing 108, onto which wafer cassettes conveyed through
the openings cut in the front wall of the casing 108 are placed,
each wafer cassette containing a wafer to be processed or to be
cleaned. On the rightmost one of the cassette tables 109 is placed
a dummy cassette 110 for a dummy wafer used to clean the internal
of processing unit 103, 103', 104 or 104'.
[0027] The transfer robot in the casing 108 functions to carry in
or out wafers between the wafer cassettes and the lock chambers
113, 113'. The atmospheric pressure block 101 also has a position
registration section 118 which is communicated with the casing 108,
and the transfer robot takes the wafer out of the wafer cassette
and then transfers it into the position registration section 118.
The transferred wafer is subjected to positioning in the position
registration section 118 in such a manner that the positioned state
remains the same as when the wafer is placed on the sample table in
the lock chamber 113 or 113'. The lock chamber 113 connects between
the atmospheric pressure block 101 and the transfer chamber in the
vacuum transfer vessel 112 serving as a transfer unit. The pressure
within the lock chamber 113 can be increased or decreased with a
wafer contained therein, and the lock chamber 113 is connected with
a gas exhaust unit and a gas supply unit, both for controlling the
pressure within the lock chamber 113.
[0028] For proper operation, the lock chamber 113 is provided in
front or rear with gate valves to hermetically close the lock
chamber 113. The lock chamber 113 further includes a wafer
supporting table within and the wafer supporting table is provided
with a means for immobilizing the wafer while the pressure in the
lock chamber 113 is being increased or decreased. Namely, the lock
chamber 113 is so designed as to be provided with a sealing means
which withstands the difference between the pressures inside and
outside the chamber while the wafer is being placed within the
chamber.
[0029] In this embodiment, the processing units 103, 103' of the
processing block 102 are etching process units having etching
chambers in which wafers transferred from wafer cassettes to the
processing block 102 are etched, whereas the processing units 104,
104' of the processing block 102 are ashing process units for
ashing the wafers. Further, these processing units are detachably
connected with the side walls of the vacuum transfer vessel 112
serving as the transfer unit and having a shape of roughly regular
polygon (hexagon in this case shown) in plan. The vacuum transfer
vessel 112 includes a transfer chamber whose internal can be kept
at high vacuum. These processing units 103, 103', 104, 104' are
disposed in right-left symmetry with respect to a plane
perpendicular to the sheet of the drawing (FIG. 1), intersecting
the sheet of the drawing in the vertical direction, and passing
through the center of the vacuum transfer vessel 112. Hereafter, it
is to be understood that the description regarding the processing
units 103, 104 is applicable to the processing units 103', 104'
unless otherwise indicated.
[0030] Moreover, the processing block 102 includes a control unit
107 located between the processing units 103 and 104 and especially
adjacent to the side wall of the vacuum chamber, the control unit
107 including mass flow controllers for controlling the supply of
processing gas or liquid necessary for processing in the units or
processing chambers within the units. The mass flow controllers
included in the control unit 107 are provided for the adjacent
processing units 103 and 104, respectively. One mass flow
controller is disposed upon the other so that the supply paths for
processing gas or liquid fed to the respective processing units may
be shortened and that the resistance of the processing fluid
through its conducting path may be lessened.
[0031] The transfer unit has in its transfer chamber the robot arm
(not shown) which transfers a wafer between the lock chambers 113,
113' and the processing chambers in the processing units 103 and
104, whose internals are kept at a reduced pressure. In this
embodiment, as described above, regarding the processing units 103
and 104, two etching process units and two ashing process units are
disposed around and in contact with the side walls of the polygonal
vacuum transfer vessel 112. The two etching process units 103 are
connected with the two rearmost side walls of the vacuum transfer
vessel 112 whereas the two ashing process units 104 are connected
with those side walls of the vacuum transfer vessel 112 which are
adjacent to the side walls to which the two etching process units
103 are connected. The lock chambers 113 are connected with the
remaining side walls of the vacuum transfer vessel 112. Namely,
this embodiment involves two etching process chambers and two
ashing process chambers.
[0032] Under the processing block 102 are located rectangular beds
106, 106', 106'', 106''', corresponding to the respective
processing units, which accommodate therein various utility units
such as reservoirs for gases necessary for different processes,
reservoirs for cooling medium, exhaust mechanisms, and power supply
sources. Each of the processing units 103 and 104 is divided into
two sections vertically, i.e. the upper section including the
processing chamber therein and the lower section including the
utilities for the processing chamber. Also, the processing units
103 and 104 include the processing chamber sections and the beds
106 and 106'' serving as the upper sections, and they, each as a
single unit, are detachably connected with the vacuum transfer
vessel 112 or the transfer unit.
[0033] The beds 106, 106'' for the processing units 103, 104 are in
the form of a rough parallelepiped which incorporates therein
utilities, controllers, heat exchanges that are all necessary parts
in the upper process chamber sections. The utilities include, for
example, an evacuation pump for evacuating the processing chambers,
a power source for supplying electric power, a reservoir of gas fed
into the processing chamber incorporating therein a sample table
for fixedly supporting a wafer as a sample thereon, a reservoir of
cooling medium for cooling the sample table, and a heat exchange
for refrigerating cycle wherein the cooling medium is circulated
and subjected to heat exchange. The beds 106, 106'' contain these
utilities, and the bottom surfaces of the beds are connected with
the upper flat surfaces of supporting pillars.
[0034] The process chamber sections of the processing units 103,
104 are connected with the vacuum transfer vessel 112 through its
side walls via dedicated gate valves. A supporting frame (not
shown) is located beneath the vacuum transfer vessel 112 to support
the vessel at a predetermined height. The utilities within the beds
106, 106'' corresponding to these process chamber sections are
connected with pipes for gas or fluid, or wiring conductors for a
power source or controllers in the spaces beneath the vacuum
transfer vessel 112. Interface sections necessary for driving the
utilities contained in the beds 106, 106'' are provided on the side
surfaces of the beds 106, 106''. The side surfaces of the beds 106,
106'' are located in the space between the bottom surface of the
frame or the vacuum transfer vessel 112 and the floor.
[0035] As described above, according to this embodiment, the
processing units 103, 104 constitute a single combined unit
consisting mainly of the corresponding beds 106, 106'' and the
superposed process chamber sections (including evacuating
apparatuses for evacuating the processing chambers). This single
combined unit is connected detachably with the vacuum processing
apparatus 100 or the vacuum transfer vessel 112.
[0036] The lock chambers 113, 113' are located in rear of the
atmospheric pressure block 101 and between the block 101 and the
processing block 102, and spaced apart from the beds. In rear of
the casing 108 in the atmospheric pressure block 101 are located
supply conduits for the piping for the gas and cooling medium fed
to the processing block 102, wiring conductors from the power
sources and so on, and other piping. In general, the vacuum
processing apparatus 100 is usually placed in a clean room, i.e. a
room in which air is purified. Further, if plural processing
apparatuses are installed in a clean room, the reservoirs for
various gases and cooling medium fed into the plural processing
apparatuses and the power sources for energizing the plural
processing apparatuses are usually placed together, from the
standpoint of improving the efficiency of layout, on a floor
different from that of the clean room, and connected with the
plural processing apparatuses via pipes and cables for circulation
and supply.
[0037] According to this embodiment, a connection interface 116 for
the supply lines such as gas and coolant pipes coming from a
different floor and the power cables from power sources, is formed
in integration with and along the rear surface of, the casing 108.
Also, those supply lines which are connected with other supply
lines in the connection interface 116 and which serve as the supply
lines for utilities supplied to the processing block 102, include
gas and coolant pipes and power cables from the connection
interface 116. Those supply lines are laid out beneath the lock
chambers 113, 113' and beneath the central part of the bottom
surface of the vacuum transfer vessel 112, and connected with the
respective beds via the connection interface 116 provided for the
bed 106.
[0038] Namely, in integration with and along the rear surface of
the casing 108 are provided a detecting unit for detecting the
working conditions of the supply lines connected with the
processing block 102 at the connection interface 116, and a display
section 117 having a display unit for displaying the output of the
detecting unit so as to enable a user to monitor the working
conditions of various devices. Further, an adjusting unit may be
provided for adjusting the supply through the supply lines or for
receiving such instructions as to adjust the supply.
[0039] Moreover, a gap or space is provided between the rear
surface of the casing 108 and the processing units 104, 104' in the
processing block 102. The gap is so provided as to enable the user
to step in it and work on the processing units 104, 104', the
vacuum transfer vessel 112, or the lock chambers 113, 113', or also
to enable the user to check, adjust and service the connection
interface 116 and the display section 117 on the rear surface of
the casing 108. Furthermore, units for displaying the information
on the operating conditions of the devices connected to the supply
lines and adjusting the devices, are laid out in a concentrated
manner so that the pre-start work for the operation of the plasma
processing apparatus is facilitated with the result that the net
working rate of the apparatus can be improved.
[0040] Also, according to this embodiment, the supply lines for
utilities necessary for the respective units in the processing
block 102 are located together. Since the supply lines such as
fluid supply pipes and electric cables coming from another location
such as a floor below the floor on which the vacuum processing
apparatus 100 is placed, are collected together on the rear surface
of the casing 108 in the atmospheric pressure block 101, the work
of mounting, connecting and dismounting the supply lines can be
facilitated in installing the vacuum processing apparatus 100 on a
floor, servicing the same and replacing the parts thereof.
Accordingly, working efficiency can be improved.
[0041] Further, pipes and cables are placed in the space beneath
the vacuum transfer vessel 112 and the lock chamber 113 and between
the beds corresponding to the respective processing units. Thus,
the space in which a serviceman mounts, connects or dismounts the
pipes and the cables is secured, whereby the work of mounting,
connecting and dismounting the supply lines can be facilitated and
the operating efficiency of the apparatus can also be improved.
Still further, since the connections of supply lines for utilities
are made in the space inside the apparatus, i.e. beneath the vacuum
transfer vessel 112 and between the beds, the volume of the space
for working within can be saved so that the footprint of the
apparatus can be saved as compared with the case where the fluid
supply pipes, electric cables and their coupling sections are
provided around the apparatus. This makes it possible to install a
greater number of apparatuses in a predetermined floor area.
[0042] The top portions of the beds have flat surfaces, on which a
user or a serviceman can access or service various units such as
the process chamber section, the vacuum transfer vessel 112, etc.,
or replace parts easily. Namely, the space over the beds is used as
maintenance space and this also contributes to the reduction of the
floor area required for the installation of a vacuum processing
apparatus as a whole and further to the improvement in the
efficiency of servicing the apparatus.
[0043] The processing chambers in the processing units 103, 104
contain supporting tables on which wafers transferred into the
chambers are placed and the supporting tables are provided with
mechanisms for controlling the temperatures of the tables. For
example, a sample table 103a of roughly cylindrical shape is
disposed in the processing chamber in the processing unit 103 and
concentric ducts through which heat exchange medium composed mainly
of water flows are cut within the sample table 103a.
[0044] The concentric ducts are connected with circulation ducts
119 for heat exchange medium to flow through. The heat exchange
medium is fed into the concentric ducts in the sample table via the
circulation duct 119 after its temperature has been adjusted by a
temperature controller 105a or 105b to a suitable value at which
processing is performed. The heat exchange medium flowing out of
the sample table 103a returns to the temperature controllers 105a,
105b via the circulation duct 119 to complete a circulation. A
circulation duct selector 120 is located between the temperature
controllers 105a, 105b, and the circulation duct selector 120 sets
up the flow paths between the temperature controllers 105a, 105b
and between the circulation duct 119 and the temperature controller
105a or 105b. The circulation duct selector 120 changes over the
flow of the heat exchange medium toward the sample table 103a via
the circulation duct 119 between the temperature controller 105a
and the temperature controller 105b.
[0045] In this embodiment, the two temperature controllers 105a or
105b and the circulation duct selector 120 are contained in a
housing 115 of roughly parallelepiped shape disposed adjacent to
the rear side (upper position in FIG. 1) wall of the bed 106 having
a roughly parallelepiped shape, corresponding to the processing
unit 103. The housing 115 is disposed on the floor on which the
vacuum processing apparatus is disposed, but it may also be
disposed beneath the floor, i.e. in the ceiling of the room located
beneath the floor.
[0046] FIG. 2 shows in vertical cross section the structure of the
processing unit shown in FIG. 1. In FIG. 2, the processing unit 103
as the vacuum processing apparatus 100 according to the embodiment
of this invention is conceptually divided into two blocks, i.e.
upper and lower blocks. The upper block includes the process
chamber section in which the sample to be processed is placed for
processing and the bed 106 containing a power source for supplying
necessary power for the process chamber section and the reservoir
for cooling medium. For example, the upper block is provided with a
processing chamber 201 which serves as the space within a vacuum
vessel whose internal pressure is to be reduced by evacuation, the
vacuum vessel being made of electrically conductive material such
as aluminum selected depending on the associated process
specification, and the sample table 103a of roughly cylindrical
shape disposed in the processing chamber 201.
[0047] In the processing unit 103, concentric ducts 203 for
temperature-controlled cooling fluid as heat exchange medium to
flow through, are cut within the disc-shaped base member 202
serving as the sample table 103a so as to control the temperature
of the sample table 103a; the circulation ducts 119 serving as pipe
lines for the cooling medium are connected with the concentric
ducts; and the two temperature controllers 105a, 105b connected
with the circulation ducts 119 to control the temperature of the
cooling medium and the circulation duct selector 120 connected with
the circulation ducts 119 via cooling medium pipe lines, are
contained in the housing 115. The concentric ducts 203 serves as a
means for controlling the temperature of the sample table 103a, and
the temperature of the sample table 103a can be properly controlled
by enabling such a temperature control means.
[0048] In the processing chamber 201 is provided a gas supply unit
for supplying process gas containing chlorine into the upper region
of the processing chamber 201 from the position opposite to the
wafer supporting surface (i.e. upper surface) of the sample table
103a, on which a disc-shaped wafer 205 to be processed as a sample
is placed. The process gas is poured from the gas supply unit
toward the wafer 205 placed on the sample table 103a.
[0049] In the process chamber section are provided the processing
chamber 201; an electric field supply unit for supplying electric
field in the form of electromagnetic waves and a magnetic field
supply unit for supplying magnetic field, into the processing
chamber 201; the gas supply unit for supplying process gas into the
processing chamber 201; an upper and a lower vessel walls 212, 218
for constituting a vacuum vessel that hermetically encloses the
processing chamber 201; and an evacuating unit disposed under the
lower vessel wall 218 for discharging the particles of the gas or
plasma out of the processing chamber 201 and for reducing the
internal pressure of the processing chamber 201 and maintaining the
internal at a predetermined level of vacuum. The evacuating unit is
communicated with an exhaust opening 219 which is an opening cut in
the bottom center of the lower vessel wall 218 enclosing a vacuum
chamber 214 that defines the space beneath the sample table 103a.
The evacuating unit discharges process gas, plasma and reactive
products in the processing chamber 201 into the external thereof
via the gap around the circumference of the sample table 103a, the
vacuum chamber 214 and the exhaust opening 219.
[0050] Above the process chamber section are provided a magnetron
207 serving as the electric field supply unit for supplying
electric field into the processing chamber 201; an upper waveguide
208a serving as a channel for guiding microwaves generated by the
magnetron in the horizontal direction (as indicated by a horizontal
arrow); and a lower waveguide 208b communicated with the upper
waveguide 208a. The microwaves propagating through the upper
waveguide 208a in the direction indicated by the horizontal arrow
enter the lower waveguide 208b, proceed through it in the direction
indicated by a vertical arrow, and reach the processing chamber 201
below. Namely, the lower waveguide 208b serves as a coupling member
that couples the waveguide 208a having an electromagnetic wave
source with the processing chamber 201 below.
[0051] The microwaves entering the lower waveguide 208b develop an
intense electric field in the approximately horizontal direction in
the space occupying the upper region of the processing chamber 201
and the lower region of the lower waveguide 208b, by means of a
slot antenna. The lower part of the lower waveguide 208b is
provided with a disc-shaped dielectric window pane 209 made of
insulating material such as, for example, quartz. The
electromagnetic waves that develop the high-intensity electric
field are propagated through the dielectric window pane 209 into
the cylindrical processing chamber 201 below.
[0052] In this embodiment, gas intake ports 210 are provided which
are communicated with a space beneath the dielectric window pane
209, and process gas is supplied into the space via the gas intake
ports 210 after its flow rate has been controlled by the mass flow
controller (MFC) disposed in the control unit 107 shown in FIG. 1.
The process gas entering the space is then diffused into the
processing chamber 201 through the plural perforations of a gas
diffusing plate 211 located below. The gas diffusing plate 211,
just like the dielectric window pane 209, may be made of dielectric
material such as, for example, quartz or semiconductor material
such as, for example, silicon, but the material must be the one
through which the electromagnetic waves traveling via the
waveguides 208a, 208b can pass into the processing chamber 201.
[0053] As described above, the dielectric window pane 209 and the
gas diffusing plate 211 constitute the upper wall (ceiling) of the
processing chamber 201, and the gas diffusing plate 211 serves as
the inner wall of the processing chamber 201 which is exposed to
the plasma formed in the processing chamber 201. The processing
chamber 201 is communicated with the evacuating unit such as, for
example, a vacuum pump (not shown), and the pressure in the
processing chamber 201 is reduced to develop a predetermined level
of vacuum while the reactive products are being produced by the
plasma generated from the supplied process gas. A solenoid coil 213
is provided around the upper vessel wall 212 of the processing
chamber 201 to develop magnetic field in the processing chamber
201. The process gas fed into the processing chamber 201 is turned
into plasma due to its interaction with the combined effect of the
electric field created in the process chamber due to the
electromagnetic waves travelling through the dielectric window pane
209 and the gas diffusing plate 211 into the chamber 201 and the
magnetic field created in the processing chamber 201 by the
solenoid coil 213. Thus, plasma is formed in the space above the
sample table 103a in the processing chamber 201 inside the upper
vessel wall 212.
[0054] The sample table 103a is located under the gas diffusing
plate 211 serving as the ceiling of the processing chamber 201,
and, as a result, a wafer 205 supported on the sample table 103a
and the gas diffusing plate 211 face each other. The disc-shaped
base member 202 of electrically conductive material is included in
the sample table 103a and connected electrically with a
high-frequency power source 215. The electric power supplied from
the high-frequency power source 215 creates a high-frequency bias
voltage in and near the surface of the wafer 205 placed on the base
member 202 or a dielectric film 217 disposed on the upper circular
surface of the base member 202. At least one electrostatic
attracting electrode is provided on the inner side of the
dielectric film 217 and connected electrically with a variable
direct current source 216.
[0055] The wafer 205 is attracted onto and supported fixedly on the
sample table 103a (dielectric film 217) due to the electrostatic
force developed between the dielectric film 217 (or electrode) and
the electric charges accumulated on the surface of the wafer 205 as
a result of interaction among the electrostatic attracting
electrode, the dielectric film 217, the wafer 205 and the plasma.
The electrostatic attracting electrode may be the same as the
electrode to which power from the high-frequency power source 215
is supplied.
[0056] Ions contained in the plasma generated above the sample
table 103a are accelerated by the bias voltage developed by the
high-frequency power supplied to the base member 202 and bombard
the surface of the wafer 205. Accordingly, radicals are formed in
the wafer surface, the formed radicals react on the substance of
the wafer surface, and, as a result, the wafer is processed (etched
in this embodiment). The reaction between the substance in the
wafer surface and the plasma give rise to reaction products above
the wafer 205 in the processing chamber 201.
[0057] The thus generated reaction products, the plasma and the gas
unused for processing are moved down through the gap around the
periphery of the sample table 103a into the vacuum chamber 214 and
discharged out of the processing chamber 201 through the exhaust
opening 219 cut in the bottom center of the lower vessel wall 218
by the suction force developed by means of an exhaust unit such as,
for example, a vacuum pump (not shown).
[0058] In this embodiment, the exhaust opening 219 is provided with
a shutter valve which opens or closes the exhaust opening 219
through rotating operation. The shutter valve can vary the aperture
of the exhaust opening 219 depending on the degree of rotation, so
as to control the exhaust rate. The upper and lower vessel walls
212, 218 constituting the processing chamber 201 and the vacuum
chamber 214 are both grounded through any suitable means.
[0059] In this embodiment, a sample table ring 204 of dielectric
material is provided surrounding the upper and outer periphery of
the sample table 103a so that when the wafer 205 is placed on the
sample table, the outer periphery of the wafer 205 is surrounded by
the sample table ring 204. The dielectric sample table ring 204
serves to prevent current from flowing from the direct current
source for the electrostatic attracting electrode to the plasma in
the processing chamber 201. The sample table ring 204 may be made
of insulating material for this purpose.
[0060] The sample table ring 204 may also be provided with any
means for protecting the sample table 103a or the base member 202
serving as an electrode from the bombardment of ions in the
generated plasma. For example, the sample table ring 204 may be
covered with any protective material which hardly affects the
processing of the wafer 205, or made of ceramic such as, for
example, alumina which is hardly etched by the bombarding ions and
also free from adverse effect on the processing.
[0061] Since the wafer 205 is processed by the bombarding ions in
the plasma, the temperature of the wafer 205 is elevated during the
processing. Therefore, the cooling medium whose temperature is
controlled by the temperature controller 105a or 105b is passed
through the concentric ducts 203 cut within the sample table 103a.
The cooling medium leaving the concentric ducts 203 is circulated
back to one of the temperature controllers 105a, 105b so that the
temperature of the upper surface of the sample table 103a or the
wafer 205 may be adjusted to a desired value during the
processing.
[0062] In order to improve the efficiency of heat transfer between
the wafer 205 and the sample table 103a or the base member 202 and
to thereby adjust the temperature of and its distribution in, the
wafer 205 as desired, heat transfer gas (e.g. He) is supplied from
a heat transfer gas source 222 into the gap between the bottom
surface of the wafer 205 and the upper surface of the dielectric
film 217 serving as the sample supporting surface. Accordingly, the
temperature of and its distribution in, the wafer 205 having heat
capacity much smaller than heat capacity of sample table 103a can
approach the temperature of and its distribution in, the sample
table 103a.
[0063] The cooling medium is supplied from one of the temperature
controllers 105a, 105b via the circulation duct 119 into the
concentric ducts laid out as described above within the base member
202 of the sample table 103a, exchanges heat with the base member
202 while flowing through the concentric ducts 203, and leaves the
base member 202 to return to one of the temperature controllers
105a, 105b. The cooling medium whose temperature has been
controlled again in the temperature controller 105a or 105b, flows
again through the circulation duct 119 to restart its circulation.
Thus, the temperature of and its distribution in, the base member
202 can be controlled as desired.
[0064] The temperature controllers 105a, 105b are disposed in rear
of the bed 106 placed on the floor on which the vacuum processing
apparatus 100 is placed. Namely, in this embodiment, they are
disposed within the housing 115 having a roughly parallelepiped
shape and serving also as a platform for a user to use in climbing
up on the bed 106. This layout of parts not only facilitates the
use's work such as maintenance but also improves the efficiency of
parts layout, so that the footprint of the vacuum processing
apparatus 100 can be saved and, in addition, that the efficiency of
operating the vacuum processing apparatus 100 can be improved. The
housing 115 used for climbing up on the base 106 is reinforced by
lining its internal surfaces with planks or the like. The housing
115 may be formed as a bed section 103b. Thus, the platform serving
also as the housing 115 can be attached to or detached from the bed
section 103b or the vacuum processing apparatus 100, and when the
housing is the bed section 103b, it can be attached to and detached
from the apparatus proper.
[0065] In the processing of the wafer 205 in the processing unit
103, the internal of the processing chamber 201 is depressurized to
a preset pressure of, for example, 0.0133 Pa. Now, the wafer 205 is
placed on the dielectric film 217, serving as the sample supporting
surface, disposed on the sample table 103a, and attracted onto the
sample supporting surface for immovable support by means of an
electrostatic attracting means. Then, the temperature control means
including the concentric ducts 203 for guiding cooling medium
within the sample table 103a is driven, and heat transfer gas such
as, for example, He, whose flow rate is controlled, is supplied
into the gap between the wafer 205 and the dielectric film 217.
Accordingly, the wafer 205 can be maintained at the temperature
close to a desired temperature value. With the wafer 205 fixedly
supported on the dielectric film 217, process gas such as, for
example, chlorine is poured toward the wafer 205 by means of a
process gas supply means. Plasma is formed in the processing
chamber 201 by ionizing the process gas by the electromagnetic
waves supplied into the processing chamber 201. The processing
(i.e. etching in this embodiment) of the wafer 205 is started by
using the plasma. When a predetermined process has been completed,
the wafer 205 is carried out of the processing chamber 201 and a
series of processing steps performed in the processing unit 103 are
completed.
[0066] According to this embodiment, the sample table 103a consists
of the base member 202 made of titanium having a roughly circular
disc-shape, in which the concentric ducts 203 for guiding cooling
medium within the sample table 103a is provided, and the dielectric
film 217 which is formed over the surface of the disc-shaped base
member 202 by the thermal spray of alumina or yttria. The
concentric ducts 203 are coupled via the circulation ducts 110 to
the temperature controllers 105a, 105b, which respectively cool
down the cooling medium to different temperatures. Accordingly, by
selecting a desired path of cooling medium, i.e. one of the
circulation ducts 119, by the circulation duct selector 120
provided in association with the temperature controllers 105a,
105b, the temperature of and its distribution in the base member
202 and therefore the temperature of and its distribution in the
wafer 205 fixedly supported on the base member 202 can be
controlled. The temperature values at which the temperature
controllers 105a, 105b set the cooling medium are controlled by the
signal outputted from a control device (not shown) that controls
the vacuum processing apparatus 100.
[0067] The structure of the sample table 103a as the embodiment of
this invention will now be described in detail in reference to FIG.
3. FIG. 3 schematically shows in vertical cross section the
structure of the sample table 103a shown in FIG. 2. In FIG. 3 is
omitted the sample table ring 204 provided around the outer
periphery of the disc-shaped dielectric film 217 disposed on the
base member 202.
[0068] In FIG. 3, the dielectric film 217 in its principal portion
is in the laminated structure consisting of at least more than one
film layer. In this embodiment, the dielectric film 217 comprises
two dielectric films of alumina or yttria, i.e. lower film 217a and
upper film 217b adjacent to each other. Three film-like heaters
whose operations are independently controlled, i.e. an inner heater
322, an intermediate heater 320 and an outer heater 321, are
embedded in the lower dielectric film 217a. They are laid out
concentrically; the inner heater 322 is circular and the
intermediate and outer heaters are of ring shape. The top plane
surfaces of these three heaters are even with one another.
[0069] Two electrostatic attracting electrodes, i.e. a circular one
in the center and a ring-shaped one surrounding the circular one,
can be embedded in the upper dielectric film 217b. In this
embodiment, as shown in FIG. 3, the two electrostatic attracting
electrodes are an inner electrode 341 located in the center and an
outer electrode 342 surrounding the inner electrode 341. The inner
electrode 341 and the outer electrode 342 are connected
respectively with variable direct current sources 216a, 216b for
power supply. In this embodiment, the inner electrode 341 and the
outer electrode 342 are kept at positive and negative potentials,
respectively. Therefore, the sample table 103a according to this
embodiment functions as an electrostatic chuck of dipole type so
that the wafer can be freely put on or taken off the sample table
irrespective of whether or not there exists plasma around the
sample table.
[0070] The inner, intermediate and outer heaters 322, 321 and 320
are connected via respective filters with separate power sources,
which energize the heaters to perform heating operations. In FIG.
3, connection with power source is shown only for the outer heater
320. Namely, a power source 328 is connected via a coil 327 serving
as a filter with the outer heater 320 by means of a connector 323
inserted in a tube 324 of insulating material penetrating the outer
peripheral portion of the base member 202.
[0071] The base member 202 is electrically connected with a
high-frequency power source 215 for applying a bias voltage to the
wafer 205. The bias voltage causes ions in the plasma to bombard
the top surface of the wafer 205 to perform anisotropic etching.
During the etching process, the wafer 205 is heated and the heat
causes the elevation of the wafer temperature, which adversely
affects etching precision to a large extent. To avoid the elevation
of the wafer temperature, therefore, the wafer 205 must be cooled
down. For this purpose, a through-hole 330 is bored in the sample
table 103a at the center, and heat transfer gas such as, for
example, He is fed through the through-hole 330 so that the heat
transfer between the wafer 295 and the dielectric film 217b can be
secured to avoid unwanted elevation of the wafer temperature. It
should here be noted that grooves (not shown nor described in
detail) for spreading He gas through them are cut in the upper
surface of the dielectric film 217b and that the layout pattern of
the grooves is optimized such that the He gas introduced via the
upper opening of the through-hole 330 into the grooves may reach
the periphery of the wafer 205 with minimum pressure loss
possible.
[0072] In this embodiment, the temperature of the wafer 205 during
etching process is detected by using the output of the sensor that
detects the temperature of the base member 202, the distribution of
which is previously known to have a close correlation to that of
the temperature in the wafer 205. To be concrete, holes 334 are
bored in the base member 202 at positions apart by certain radial
distances from the center of the base member 202, the bottoms of
the holes 334 not reaching the undersurfaces of the inner heater
323, the intermediate heater 321 and the outer heater 320, and
sheathed thermocouples 333 are placed fixedly in the holes 334 by
means of springs 335 and fixing means 336 attached to the
undersurface of the base member 202. In FIG. 3 is shown only the
sheathed thermocouple 333 located under the intermediate heater
321. When such a sheathed thermocouple is used as a temperature
sensor, the quality of contact of the tip of the thermocouple with
the base member 202 largely affects the result of temperature
detection. In this embodiment, however, the urging force of the
spring 335 can provide secure contact between the thermocouple 333
and the base member 202 so that the result of the temperature
detection can be highly reliable.
[0073] The result of the temperature detection is outputted to a
control unit 337, which detects the temperature of and its
distribution in the base member 202 on the basis of the inputted
result. Consequently, on the basis of this result are controlled
the operations, i.e. degree and duration of heating, of the inner
heater 322, the intermediate heater 321 and the outer heater 320
which are connected with the control unit 337 in a communicable
manner. It is to be noted that the sheathed thermocouple may be
replaced by a platinum resistor, a fluorescent thermometer, a
radiation thermometer, etc. Further, if foreign material deposition
on the rear surface of the base member 202 is negligible, the tip
of the temperature sensor can be in direct contact with the rear
surface of the base member 202.
[0074] Although only one power supply unit for heating is shown in
FIG. 3, it will be needless to say that two such units are actually
necessary. In this embodiment, power supply for the heater may be
from an AC or a DC source.
[0075] The patterns of the inner heater 322, the intermediate
heater 321 and the outer heater 320 are laid out in the region of
the sample table corresponding to that region of the wafer 205 in
which the temperature of and its distribution in the wafer 205 in
the circumferential or radial direction are to be controlled. In
fabricating such heater patterns, the thermal spray technique can
be used to advantage. Namely, in order to fabricate heater patterns
by thermal spray, pattern masks have only to be prepared.
Therefore, no specific limitation is imposed on the pattern to be
employed. For example, the power supply terminals of the heaters
can be located at any desired positions. On the other hand, if
sheathed heaters are used, embedded in the base member 202, the
rigidity of the sheath prevents itself from being bent in a very
small curvature, making it unrealistic to design a complicated
heater pattern. The change in the heater pattern causes the change
in the overall length of the heater and therefore the change in the
heater resistance. In case of fabricating the heater by thermal
spray, the heater resistance can be easily optimized by controlling
the thickness and the resistivity of heater material.
[0076] In this embodiment, multiple heaters 329 of concentric
layout may be disposed on top of the base member 202 in addition to
the concentric film heaters embedded in the dielectric film 217b.
The heaters 329 are disposed between the concentric ducts 203 cut
in the base member 202 and the top surface of the base member 202.
The temperature of and its distribution in the base member 202 and
the temperature response can be improved by the combined effects of
the heating by the heaters 329 and the cooling with the cooling
medium flowing through the ducts 203.
[0077] As shown in FIG. 2, the concentric ducts 203 of the base
member 202 is coupled to the circulation ducts 119a, 119b which are
coupled to the temperature controllers 105a and 105b via the
circulation duct selector 120, respectively. In this embodiment,
the temperature controller 105a adjusts the temperature of the
cooling medium to a low value and the temperature controller 105
adjusts the temperature of the cooling medium to a high value, and
the circulation duct 119a acts as a duct on the return side and the
circulation duct 119b acts as a duct on the supply side.
[0078] The circulation duct selector 120 is provided with control
valves 345, 346, 347 and 348 each acting as a mass flow controller
which are provided on the respective paths of the cooling medium
disposed therein. These control valves are operated based on
instruction signals 337a from the control unit 337 to thereby
close/open the respective paths of the control valves or adjust
flow rates of the cooling medium of the respective paths of the
control valves, whereby the supply of the cooling medium to the
duct 203 from the temperature controllers 105a, 105b can be changed
therebetween. FIG. 3 shows an example where the cooling medium
passing through the temperature controller 105b circulates through
the ducts of the base member 202.
[0079] With respect to the cooling medium which temperature is
adjusted by the temperature controller 105a, each of the control
valve 345 on the supply side and the control valve 347 on the
return side is made off (closed). Ducts 338, 339 for respectively
coupling the temperature controller 105a with the control valves
345, 347 are coupled to each other via a bypass valve 342. Thus,
the cooling medium, which temperature is adjusted by the
temperature controller 105a, also flows through the ducts
circulating via the bypass valve 342 and so is always set to a set
temperature accurately.
[0080] As to the cooling medium, which temperature is adjusted by
the temperature controller 105b, since each of the control valve
346 on the supply side and the control valve 348 on the return side
is made on (opened) or is adjusted its flow rate, the cooling
medium can circulate so as to return to the temperature controller
105b via the ducts 203 and 119a from the duct 119b. Further, like
the temperature controller 105a, ducts 340, 341 for respectively
coupling the temperature controller 105b with the control valves
346, 348 are coupled to each other via a bypass valve 343. Thus,
the cooling medium, which temperature is adjusted by the
temperature controller 105b, also flows through the ducts
circulating via the bypass valve 343 and so is always set to a set
temperature accurately.
[0081] In this manner, the control unit 337 controls the
opening/closing or adjusts the flow rate of each of a pair of the
control valves 345, 347 and a pair of the control valves 346, 348
to thereby switch the circulation path of the cooling medium to the
duct 203 between the path via the temperature controller 105a and
the path via the temperature controller 105. As a result, the
temperature of the base member 202, that is, the temperature of the
sample table 103a and also the temperature of the wafer 205 placed
thereon can be adjusted. In this embodiment, a coupling duct 344 is
provided between the temperature controllers 105a and 105b so that
the cooling medium can be communicated therebetween. In the figure,
numerals 349a, 349b depict coupling portions of the circulation
ducts 119a, 119b, respectively.
[0082] Even if there arises a difference in a returning amount of
the cooling medium between the temperature controllers 105a and
105b depending on the switching timings of the respective control
valves 345, 346, 347 and 348, the excessive returning amount of the
cooling medium at one of the temperature controllers 105a and 105b
flows into the other temperature controller through the duct 344.
Thus, such an unbalance of the returning amount of the cooling
medium can be eliminated in a short time and so the amount of the
cooling medium in each of the temperature controllers 105a and 105b
is restored quickly. Further, since each of the respective control
valves 345, 346, 347 and 348 is controllable so as to be able to
adjust the flow rates on the discharge side and return side, such a
phenomenon as water hammering can be prevented from occurring.
Furthermore, since the temperature changing speed can be controlled
based on the flow rate of the cooling medium, the temperature
increasing speed can be enhanced to thereby shorten the processing
time.
[0083] The flow of the process associated with the vacuum
processing apparatus according to this embodiment will be described
in reference to FIGS. 4 and 5. FIG. 4 graphically shows the flow of
the plasma processing according to the embodiment of this invention
shown in FIG. 2. In FIG. 4 are shown how the temperature of the
wafer 205 (or the sample supporting surface) and the temperature of
the surface of the change with time in the case where the films of
different types or different compositions formed on top of the
wafer 205 are continuously processed in the processing unit 103
without bringing the wafer 205 out of the processing chamber. In a
typical example of this type of process, the films 1 and 2 shown in
FIG. 4 are those which are used as a gate and a wiring line
(metal), respectively.
[0084] In this embodiment, the temperature controllers 105a, 105b
can adjust the temperature of the cooling medium passing through
them to different temperature values. For example, the temperature
controller 105a adjusts the temperature of the cooling medium to
20.degree. C. while the temperature controller 105b adjusts the
temperature of the cooling medium to 80.degree. C. The temperature
difference of 60.degree. C. is selected such that it is greater
than the maximum value .DELTA.Th of the temperature difference
attainable in the top surface of the dielectric film 217 by means
of the outer heater 320, the intermediate heater 321 and the inner
heater 322 embedded in the dielectric film 217 of the sample table
103a.
[0085] In this embodiment, the maximum value .DELTA.Ts of the
temperature difference actually developed in the dielectric film
217 by these heaters is set smaller by a preset value than
.DELTA.Th. Accordingly, when the cooling medium whose temperature
has been adjusted by the temperature controller 105a is fed into
the sample table, the range of temperatures Ts1 attainable in the
top surface of the dielectric film 217 or the wafer 205 will be
between the first temperature value greater by a preset value
.delta. than the temperature Tc1 of the cooling medium immediately
out of the temperature controller 105a and the second temperature
value greater by .DELTA.Ts than the first temperature value, since
the temperature at the top surface of the base member 202 becomes
approximately equal to that of the cooling medium flowing through
the base member 202 as the heat capacity of the base member 202 is
much smaller than that of the cooling medium. When the cooling
medium whose temperature has been adjusted by the temperature
controller 105b is fed into the sample table, the range of
temperatures Ts2 will be between the third temperature value
greater by the preset value .delta. than the temperature Tc2 of the
cooling medium immediately out of the temperature controller 105b
and the fourth temperature value greater by .DELTA.Ts than the
third temperature value.
[0086] According to this embodiment, the temperature of and its
distribution in the top surface of the dielectric film 217 or the
wafer 205 are controlled as desired by controlling the operations
of the outer heater 320, the intermediate heater 321 and the inner
heater 322 through the use of the result obtained by the
temperature sensors such as, for example, sheathed thermocouples
333, on the basis of the temperature of and its distribution in the
sample table 103a that are controlled by the cooling medium whose
temperature is controlled by the temperature controllers 105a, 105b
(or the concentric film heater 329) and which flows through the
concentric ducts 203 cut within the base member 202 of the sample
table 103a. In FIG. 4, in the "film 1 processing" that is the
etching process for the first film, the temperature Ts1 of and its
distribution in each of plural different dielectric films 217 are
set up by energizing the heaters while the temperature in the
surface of the base member 202 is kept at Tc1 by feeding cooling
medium from the temperature controller 105a into the base member
202.
[0087] After the "film 1 processing" has been completed, the "film
2 processing" that is the etching process for the second film of
different type or composition is performed. At this time, if the
required lowest temperature of the wafer 205 is higher than the
highest value Ts1, Tc1 must be replaced with Tc2 by switching the
cooling medium out of the temperature controller 105a over to the
cooling medium out of the temperature controller 105b. Namely, the
circulation duct selector 120 changes the flow path of the cooling
medium on the supply side in a manner that the flow path on the
discharge (return) side is maintained so as to return the cooling
medium discharged out of the concentric ducts 203 of the base
member 202 to the temperature controller 105a via the discharge
(return) side circulation duct 119a, and thereafter changes over
the circulation ducts 119 on the supply side in such a manner that
the cooling medium supplied at 80.degree. C. from the temperature
controller 105b is fed through the concentric ducts 203 cut within
the base member 202 via the supply side circulation duct 119b. At
this time, when the control unit makes decision that the cooling
medium filling the cooling medium channel from the supply side exit
up to the return side entrance, of the circulation duct selector
120 is the cooling medium all supplied from the temperature
controller 105b, the circulation duct selector 120 operates the
pair of the control valves 345, 347 and the pair of the control
valves 346, 348 based on the control signal from the control unit
337 to change over the circulation ducts 119 in such a manner that
the cooling medium discharged out of the concentric ducts 203
returns via the circulation duct 119 to the temperature controller
105b. Thus, the cooling medium is circulated between the
temperature controller 105b and the concentric ducts 203 cut in the
base member 202.
[0088] Such duct changeover operations by the circulation duct
selector 120 are performed according to the instructions
transmitted from the control unit 337 on the basis of the process
conditions such as types and compositions of films formed on the
wafer 205 obtained through communication apparatuses prior to
processing and the data obtained by sensors (including the sheathed
thermocouple 333) located at various points in the vacuum
processing apparatus 100 or the processing units 103, for detecting
various operating conditions at the points. In order to improve the
effect of such duct changeover operations, a reservoir for storing
a preselected quantity of cooling medium may be provided between
the temperature controllers 105a and 105b, or between the
circulation duct selector 120 and the temperature controllers 105a,
105b. The capacity of the reservoir will be large enough if it
contains a quantity of cooling medium that can fill the concentric
ducts 203 and the circulation dusts 119.
[0089] Consequently, the temperature in the surface of the base
member 202 is changed to and kept at, Tc2. Then, the "film 2
processing" is performed by changing the temperature Ts2 of and its
distribution in the wafer 205 to desired values and keeping the
values, in accordance with plural different steps.
[0090] In the example shown in FIG. 4, the supply and circulation
of cooling medium is changed over between the two temperature
controllers 105a and 105b which can supply cooling media of
different temperatures, so as to set up different temperatures and
different temperature distributions in the base member 202 in
accordance with the processing steps for plural films of different
types or compositions. FIG. 5, on the other hand, shows an example
wherein the supply and circulation of cooling medium is changed
over between the two temperature controllers 105a and 105b in
accordance with the plural process steps for a single film. FIG. 5
graphically shows an example of how the plasma processing performed
with the apparatus shown in FIG. 2 proceeds with time. FIG. 5 shows
the changes in the temperature of the wafer 205 (or sample
supporting surface) and the temperature in the surface of the base
member 202 in the case where all films in the top surface of the
wafer 205 are continuously processed in the processing unit 103
without being transferred out of the processing unit 103.
[0091] In FIG. 5, the process 1 and the process 2 are the etching
processes performed on any film under different process conditions.
Before and after these processes, the transition of temperature in
the wafer 205 occurs due to the changeover of the cooling media fed
into the concentric ducts 203 and circulated through the coolant
channel and due to the operation of the heater embedded in the
dielectric film 217.
[0092] In this example shown in FIG. 5, the process 1 is performed
while the cooling medium whose temperature is set to 20.degree. C.
by the temperature controller 105a is being supplied, whereas the
process 2 is performed after the cooling medium with its
temperature kept at 20.degree. C. by the temperature controller
105a has been switched to the cooling medium whose temperature is
set to 80.degree. C. by the temperature controller 105b. In the
transition period before the process 1, the transition of
temperature in the base member 202 does not occur. Due to the
operations of the inner heater 322, the intermediate heater 321 and
the outer heater 320, the temperature of and its distribution in
the top surface of the dielectric film 217 or the wafer 205 are set
up while the cooling medium is being supplied from the temperature
controller 105a (TCU1). In the transition period after the process
1, on the other hand, the switching of the cooling medium supply
and circulation through the concentric ducts 203 and the
circulation ducts 119 takes place due to the operation of the
circulation duct selector 120 as shown in the example in FIG. 4.
Namely, the cooling medium being presently supplied from the
temperature controller 105a (TCU1) to the base member 202 is
switched to the cooling medium to be supplied from the temperature
controller 105b (TCU2) so that the transition of temperature in the
surface of the base member 202 occurs.
[0093] Thereafter, in the process 2, the temperature of and its
distribution in the top surface of the dielectric film 217 or the
wafer 205 are set up due to the operation of the inner heater 322,
the intermediate heater 321 and the outer heater 320 while the
cooling medium from the temperature controller 105b (TCU2) is being
supplied to the base member 202. After the process 2, the switching
of the cooling medium supply and circulation through the concentric
ducts 203 and the circulation ducts 119 takes place again due to
the operation of the circulation duct selector 120. As a result,
the cooling medium being presently supplied from the temperature
controller 105b (TCU2) to the base member 202 is switched to the
cooling medium to be supplied from the temperature controller 105a
(TCU1 so that the transition of temperature in the surface of the
base member 202 occurs.
[0094] The processing is placed in a transition state (transitions
1, 2, 3) between the respective processes in order to set the
temperature of the base member 202 or the sample table 103a to a
value suitable for the next process. Among these transition states,
in each of the transitions 2 and 3 accompanied with the switching
of the temperature controllers 105a, 105b, the control unit 337
instructs the switching of the control valves 345 to 348 to thereby
switch the temperature controllers in the similar manner as FIG.
4.
[0095] The switching operations in FIGS. 4 and 5 will be explained
in detail. As shown in FIG. 5, in each of the transitions 2 and 3,
the flow rate of the cooling medium supplied to the duct 203 from
the circulation duct selector is once set to 0 at the initial stage
of the transition. The flow rate is restored to the constant value
after closing all the control valves 345 to 348. On the other hand,
since the electric power supplied to (or heat generated from) the
inner heater 322, the intermediate heater 321 and the outer heater
320 is interrupted or reduced abruptly earlier than the operation
of the control valves 345 to 348, the temperatures of the areas
corresponding to the respective heaters 320 to 322 reduces once.
Then, the respective heaters are kept in the off state or the
reduced power state until the control valves 345 to 348 are
switched. Thereafter, when the control valves 345 to 348 are
switched, the flow path of the cooling medium flowing into the base
member 202 is changed between the temperature controllers 105a and
105b, so that the cooling medium flows into the duct 203 from the
switched one of the temperature controllers 105a and 105b to change
the temperature of the base member 202, whereby the temperature of
the base member 202 approaches the temperature of the cooling
medium thus applied from the switched one of the temperature
controllers. During this operation, the respective heaters 320 to
322 are subjected to the PID control so as to attain the
predetermined target temperatures thereof set for the next process,
based on the temperature values of the inner heater area, the
intermediate heater area and the outer heater area of the base
member 202 or the sample table 103a detected based on the output
from the detection device shown in FIG. 3.
[0096] Since the temperature of the cooling medium whose supply and
circulation paths are switched, is previously set up, the
temperature of the base member 202 which is made of metal such as,
for example, titanium having a large heat transfer coefficient, can
be changed (or make transition) to another level in a very short
time. Accordingly, if the temperature of the wafer 205 or the
dielectric film 217 needs to be changed in excess of the range of
temperature differences attainable in the dielectric film 217 by
means of heaters, the efficiency of processing can be improved by
performing the processing wherein the temperature of the base
member 202 is changed by switching to the circulation of the
cooling medium whose temperature is previously set up to attain
such temperature differences in excess of the range while heating
by heaters is still used. Further, since the temperature in the
base member 202 of metal is controlled by the cooling medium
passing through the concentric ducts 203 cut in the base member
202, the unevenness in temperature distribution throughout the base
member 202 is relatively small. Accordingly, even when the
temperature in the wafer 205 is largely changed by means of the
heaters, the unevenness in temperature distribution throughout the
wafer can be rendered small so that the temperature distribution in
the radial or circumferential direction of the wafer 205 can be
controlled with high precision. Thus, the manufacturing yield can
be improved.
[0097] In the embodiment described above, the two temperature
controllers 105a, 105b are used to set up the temperatures of
cooling medium, but more than two temperature controllers may be
employed to embody this invention. Further in the above described
embodiment, the concentric ducts 202 cut in the base member 202 are
fed with the cooling medium having a single temperature value
supplied from a single temperature controller at a time, but it
will be needless to say that in another embodiment of this
invention, more than one independent set of concentric ducts may be
cut in the base member 202 and that the respective independent sets
of concentric ducts may be fed with the cooling media whose
temperatures are different from one another, so as to set up
different temperature distributions in the central and peripheral
areas of the base member 202. In still another embodiment, each set
of concentric ducts mentioned above may be provided with more than
two temperature controllers and more than one circulation duct
selector so as to feed the set of concentric ducts with more than
two flows of cooling medium having more than two temperature
values.
[0098] This embodiment requires the complicated control at the
switching timing of the cooling medium circulation path as compared
with the related art. However, in the process of the film 2 of FIG.
4 or the process 2 of FIG. 5 for performing the high-temperature
control, since the temperature difference between the cooling
medium (or the temperature of the base member 202) and the
respective heater portions to be controlled becomes small, an
amount of the electric power supplied to (or an amount of heat
generated from) the respective heaters can be made small. Further,
since the temperature of the cooling medium can be changed at the
time of the temperature increase or reduction, an amount of the
electric power supplied the heaters can be reduced or the switching
speed can be enhanced advantageously.
[0099] According to the investigation of the inventors of the
present invention, it was found that the temperature difference
between the respective heater areas and the base member 202 (the
cooling medium in the duct 203) influences to each other with and
is in proportional to the control error (the degradation of the
control accuracy) of the temperatures at the heater areas of the
wafer 205 or the surface temperature of the base member 202 or the
dielectric film 217. This is because, although a large amount of
electric power is required in order to maintain the temperature of
the wafer 205 at a high value and to enlarge the temperature
difference from the base member 202, the control error (the
degradation of control accuracy) of the temperatures becomes larger
as the electric power increases. Further, since, among the
receptive processing apparatuses, there are heating or cooling
variances within the dielectric films 217 on the base members 202
due to the variance of the resistance value densities of the
heaters 320 to 322, the partial shortage of the cooling ability of
the cooling medium of the base member 202, the partial shortage of
the cooling ability due to the structural reason such as the wafer
insertion portion and the feeding portion disposed within the
sample table 103a or the base member 202. Such the heating or
cooling variances become large as the electric power increases. The
variation can be reduced by adjusting the resistance values of the
heaters, for example, but the reduction of the variance is limited
to some extent in the case of the improving the accuracy of the
temperature adjustment requirement according to the
micro-fabrication of devices.
[0100] The function to be realized finally in the aforesaid
embodiment is to uniformize the etching result on the wafer
surface. To this end, according to the embodiment, the plasma
distribution set to be uniform as possible is realized by adjusting
the magnetic field generated by the solenoid coil 214. Further, in
the case of forming different kinds of films continuously, the
electric power applied to the respective heaters 320 to 322 is
adjusted for each of these films so as to change the temperature
distribution in the radial direction of the wafer 205 for each film
to thereby adjust the optimum temperature and the adhesion degree
of reactive products at the outer peripheral portion of the wafer.
In general, the density of the reactive products is lower at the
outer peripheral portion of the wafer as compared with that at the
center portion of the wafer. Thus, the uniform etching result can
be obtained by reducing the temperature at the outer peripheral
portion of the wafer to reduce the adhesion degree of reactive
products thereat. However, for each wafer, the degree of the
uniform etching result is influenced by the variance of the
temperature at the outer peripheral portion of the wafer and such
the influence becomes remarkable particularly in the case of
micro-fabricating a semiconductor device with a line width of 32 nm
or less. Further, when a semiconductor device is configured to have
more layers and the materials of the respective layers are varied,
the difference of the optimum etching temperatures becomes larger
among these respective layers. In this case, it becomes difficult
to process the semiconductor device in a single processing chamber
and so a plurality of the processing chamber are required, which
disadvantageously results in the reduction of the etching speed and
the increase of the cost of the equipments.
[0101] According to the embodiment, since the temperature variance
on the entire surface (processed surface) of a wafer 205 can be
suppressed, a shift amount of the line with (CD) on the major
surface of a wafer can be reduced at the time of performing the
etching process.
[0102] Further, according to the embodiment, even in the case where
the difference of the optimum etching temperatures is large due to
the multilayer of the device structure and the variation of
materials of the respective layers, such various kinds of the
semiconductor devices can be processed by the single processing
chamber without employing a plurality of the processing chambers.
Thus, since the etching speed can be enhanced, the productivity of
the semiconductor devices can be enhanced and the cost of the
semiconductor device processing equipment can be reduced.
[0103] 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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