United States Patent [19]
`Tsubone et al.
`
`[54] WAFER COOLING METHOD AND
`APPARATUS
`[75] Inventors: Tsunehiko Tsubone, Hikari; Naoyuki
`Tamura, Kudamatsu; Shigekazu
`Kato, Kudamatsu; Kouji Nishihata,
`Tokuyama; Atsushi Itou,
`Kudamatsu, all of Japan
`[73] Assignee: Hitachi, Ltd., Tokyo, Japan
`[21] Appl. No.: 724,801
`[22] Filed:
`Jul. 2, 1991
`[30]
`Foreign Application Priority Data
`Jul. 2, 1990 [JP]
`Japan
`
`2-172757
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`437/20
`
`
`
`4,261,762 4/1981 King 4,384,918 5/1983 Abe 4,457,359 7/1984 Holden 4,615,755 10/1986 Tracy et al. .
`
`
`
`
`
`lllllllllllllllllllllllllllllllllllllllllllllllIlllllllllllllllllllllllllllv
`
`US005320982A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,320,982
`Jun. 14, 1994
`
`4,864,461 9/1989 Kasahara 4,931,135 6/1990 Horiuchi et al.
`
`4,949,783 8/1990 Lakios et a1.
`
`279/128
`156/345
`.. 118/724
`437/248
`156/345
`FOREIGN PATENT DOCUMENTS
`
`
`
`5,106,787 4/1992 Yen 5,203,958 4/1993 Arai et al.
`
`64-32628 2/1989 Japan .
`
`Primary Examiner-Olik Chaudhuri
`Assistant Examiner-Ramamohan Rao Paladugu
`Attorney, Agent, or Firm-—Antonelli, Terry, Stout &
`Kraus
`
`ABSTRACI‘
`[57]
`This invention relates to a vacuum processing method
`and apparatus. When a sample is plasma-processed
`under a reduced pressure, a sample bed is cooled by a
`cooling medium kept at a predetermined temperature
`lower than an etching temperature, the sample is held
`on the sample bed, a heat transfer gas is supplied be
`tween the back of the sample and the sample installation
`surface of the sample bed, and the pressure of the heat
`transfer gas is controlled so as to bring the sample to a
`predetermined processing temperature. In this way, a
`sample temperature can be regulated rapidly without
`increasing the scale of the apparatus.
`
`4,771,730 9/1988 Tezuka
`4,842,683 6/1989 Cheng et a1.
`
`.
`
`13 Claims, 3 Drawing Sheets
`
`PRESSURE
`
`—>H|GH
`
`CASEI I
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`CASEI [EASEII
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`EXHIBIT 2002
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`US. Patent
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`June 14, 1994
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`Sheet 1 of 3
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`5,320,982
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`EXHIBIT 2002
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`US. Patent
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`June 14, 1994
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`Sheet 2 of 3
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`5,320,982
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`PRACTICAL
`RANGE
`
`LOW+—
`
`PRESSURE
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`—* HIGH
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`F/G. 4
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`
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`wmammmmm m<w
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`EXHIBIT 2002
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`U.S. Patent
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`June 14, 1994
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`Sheet 3 of 3
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`5,320,982
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`’¢-—:.u:--1:u——x—— -
`I
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`EXHIBIT 2002
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`1
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`5,320,982
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`WAFER COOLING METHOD AND APPARATUS
`
`2
`installation surface and the sample installation surface of
`the sample bed and controlling the pressure of the heat
`transfer gas in accordance with a predetermined pro
`cessing temperature of the sample. In a method of pro
`cessing a sample under a reduced pressure, the vacuum
`processing method in accordance with the present in
`vention includes the steps of cooling a sample bed by a
`cooling medium kept at a predetermined temperature
`lower than an etching temperature, holding the sample
`on a sample installation surface of the sample bed, sup
`plying a heat transfer gas into the gap between the back
`of the sample held on the sample installation surface and
`the sample installation surface of the sample bed so as to
`control the pressure of the heat transfer gas in accor
`dance with a predetermined processing temperature of
`the sample, and processing the sample controlled to the
`predetermined temperature.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a structural view showing a microwave
`etching apparatus of an embodiment of a vacuum pro
`cessing apparatus of the present invention;
`FIG. 2 is a diagram showing the relation between the
`pressure of a heat transfer gas and the heat transfer
`coefficient of the heat transfer gas and the relation be
`tween the heat transfer gas pressure and the time con
`stant, when a sample is held on a sample bed by an
`electrostatic chuck;
`FIG. 3 is a structural view showing a parallel sheet
`type dry etching apparatus as another embodiment of
`the vacuum processing apparatus of the invention; and
`FIG. 4 is a diagram showing the relation between the
`temperature of a sample processed by the apparatus
`shown in FIG. 1 and the time necessary for the process
`mg.
`
`10
`
`30
`
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`This invention relates to a method and apparatus for
`vacuum processing. More particularly, the present in
`vention relates to a method and apparatus for vacuum
`processing which is suitable for controlling a sample
`such as a semiconductor device substrate to different
`temperatures and vacuum processing the sample.
`2. Description of the Prior Art
`As disclosed in, for example, Japanese Patent Laid
`Open No. 76876/1984, a conventional technology for
`vacuum-processing a sample by controlling it to differ
`ent temperatures is such that an object (hereinafter
`referred to as a “substrate”) to be etched is placed on an
`electrode disposed in a vacuum vessel, a reactive gas is
`introduced into the vacuum vessel, a voltage is applied
`to the electrode so as to generate gas discharge and the
`substrate is etched by this discharge gas at two or more
`different electrode temperatures.
`In the prior art technology described above, a sub
`strate temperature (to 60° C. in this prior art technol
`ogy) is raised in view of the etching selection ratio of
`25
`MoSi; to a resist and of producibility when an MoSi;
`?lm is etched, and the substrate temperature (to 30° C.
`in this prior art technology) is lowered in view of over
`etching. This prior art technology in the electrode is
`divided into an electrode on a high temperature side and
`another on a low temperature side. Etching of the sub
`strate is carried out on the higher temperature electrode
`side, and after this etching, the substrate is transferred to
`the lower temperature electrode, and over-etching of
`the substrate is carried out. Alternatively, only one
`35
`electrode is provided and the electrode temperature can
`be changed to high and low temperatures while the
`substrate is kept placed on the same electrode. The
`substrate temperature is raised to a high temperature to
`conduct its etching during processing and is lowered to
`achieve overetching of the substrate after the etching.
`
`4-0
`
`50
`
`SUMMARY OF THE INVENTION
`In the prior art technology described above, the time
`necessary for raising the substrate temperature to two
`45
`or more different temperatures and reduction of the
`scale of the apparatus have not been considered. In
`other words, if a plurality of electrodes are used, the
`apparatus becomes greater in scale because of the in
`crease in the number of electrodes. Moreover, the time
`for attaining a predetermined processing condition or a
`predetermined temperature becomes long. A long time
`is necessary, too, in order to change the electrode tem
`perature to predetermined temperatures using a single
`electrode because the heat capacity of this electrode is
`great.
`One of the references concerning the present inven
`tion is U.S. Pat. No. 4,261,762.
`In an apparatus for processing a sample under a re
`duced pressure, so as to rapidly regulate a sample tem
`perature without increasing the scale of the apparatus,
`the apparatus in accordance with the present invention
`includes means for cooling a sample bed by a cooling
`medium kept at a predetermined temperature lower
`than an etching temperature, means for holding the
`sample on a sample installation surface of the sample
`bed, and means for supplying a heat transfer gas into the
`gap between the back of the sample held on the sample
`
`55
`
`65
`
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`A sample bed is cooled by a cooling medium kept at
`a predetermined temperature lower than a processing
`temperature. A sample is held on a sample installation
`surface of the cooled sample bed by an electrostatic
`chuck, or the like. The temperature of the sample thus
`held is controlled to a predetermined processing tem
`perature in the following way.
`A heat transfer gas having a ,high thermal conductiv
`ity such as helium gas (GI-1e), etc, is supplied between
`the sample installation surface of the sample bed and the
`back of the sample. When this gas is supplied, the gas
`pressure between the sample installation surface and the
`back of the sample rises. The gas pressure is regulated
`by regulating the quantity of the heat transfer gas sup
`plied and is kept stably under a gas pressure at which
`the sample temperature is kept at the predetermined
`processing temperature.
`When the processing temperature of the sample is to
`be lowered, for example, the quantity of the heat trans
`fer gas supplied is further increased. Accordingly, the
`gas pressure in the space between the sample installation
`surface and the back of the sample becomes higher than
`the gas pressure that corresponds to the initial process
`ing temperature. Thus, the number of molecules that
`transfer heat becomes great and the sample can be
`cooled more effectively. The gas pressure is regulated
`to the one corresponding to the subsequent processing
`temperature.
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`When the processing temperature of the sample is ,to
`be raised, on the contrary, the quantity of the heat trans
`fer gas supplied is reduced, so that the gas pressure in
`the space between the sample installation surface and
`the back of the sample falls below the one that corre
`sponds to the initial processing temperature. In this
`way, the number of gas molecules that transfer heat
`becomes small and the drop of temperature of the sam
`ple can be restrained. This gas pressure is regulated to
`the one corresponding to the subsequent processing
`temperature.
`In this case, in order to improve the followup prop
`erty of the sample temperature, the heat transfer gas
`between the sample installation surface of the sample
`bed and the back of the sample is exhausted and the
`supply of the heat transfer gas is stopped or the quantity
`of the supplied gas is reduced. In this way, the gas pres
`sure in the space between the sample installation surface
`and the back of the sample drops more rapidly. Thereaf
`'ter, the exhaust of the heat transfer gas between the
`sample installation surface and the back of the sample is
`stopped.
`As described above, while the sample is held on the
`sample installation surface of the sample bed, that is,
`while the gap between the sample installation surface
`and the back of the sample is kept small (or in other
`words, in a state where the gap is kept smaller than the
`mean free path of the heat transfer gas), the coefficient
`of heat transfer between the sample and the sample bed
`can be changed by changing the gas pressure of the heat
`transfer gas in this gap, and only the sample temperature
`can be rapidly varied to a different temperature while
`the temperature of the sample bed is kept as such.
`Hereinafter, an embodiment of the present invention
`will be described with reference to FIGS. 1 and 2. FIG.
`1 shows a parallel flat plate type dry etching apparatus
`in this case.
`A sample bed 5 for placing a sample 6 thereon is
`disposed at a lower part of a vacuum processing cham
`ber 1. The sample bed Sis electrically insulated from the
`vacuum processing chamber 1 by a dielectric member 9.
`A dielectric film 7 is formed on the upper surface of the
`sample bed 5. The sample 6 is placed on or removed
`from the sample bed 5 by a conveyor device not shown
`in the drawing. The sample 6 is place on the sample bed
`45
`5 through the dielectric film 7. An insulating ring 8 is
`disposed on the part surrounding the sample 6 and on
`the side surface of the sample bed 5 in such a manner as
`to cover these portions. An upper electrode 2 is dis
`posed inside the vacuum processing chamber 1 so as to
`face the sample bed 5. A gas introduction passage for
`introducing a processing gas into the vacuum chamber
`1 through a gas introduction pipe 3 is formed in the
`upper electrode 2. An evacuator (in this case, this evac
`uator comprises a turbo molecular pump 26 and a me
`chanical booster pump 27) for decompressing and ex
`hausting the inside of the vacuum processing chamber
`1, is connected to the vacuum processing chamber 1
`through an exhaust port 4 disposed on the side surface
`of the vacuum processing chamber 1.
`A high frequency power supply 12 is connected to
`the sample bed 5 through a matching circuit 11 and a
`DC. power supply 14 is likewise connected to the sam
`ple bed 5 through a high frequency cutoff circuit 13.
`A flow passage for circulating a cooling medium is
`defined inside the sample bed 5, and a pipe 10 for trans
`ferring the cooling medium between the sample bed and
`a temperature regulator not shown in the drawing is
`
`4
`connected to this flow passage. This circulated heat
`medium is controlled to a predetermined temperature
`and is sent to the sample bed 5.
`A flow passage of the heat transfer gas is formed in
`this sample bed 5 in such a manner as to pass through
`the sample bed 5 and the dielectric film 7, and a heat
`transfer gas supply line 15 is connected to this flow
`passage. The heat transfer gas such as He gas is supplied
`under the back of the sample 6 on the dielectric film 7
`through a flow rate regulator 16 and a supply valve 17
`that are disposed in this heat transfer gas supply line 15.
`A portion of the dielectric ?lm 7, on which the sample
`6 is placed, is provided with a groove that makes the
`passage of the heat transfer gas easy. This groove is
`disposed in an area which does not reach the periphery
`of the sample 6. Accordingly, the pressure of the heat
`transfer gas under the back of the sample 6 is substan
`tially equal to the pressure of the heat transfer line 15. It
`is preferable that the heat transfer gas pressure on the
`back of the sample be higher than the pressure in the
`vacuum processing chamber 1 so as to provide a pres
`sure difference. The heat transfer gas supplied through
`the heat transfer gas line 15 passes through the gap
`between the sample 6 and the sample installation surface
`of the sample bed 5, in other words, through the gap
`between the back of the sample 6 and the dielectric film
`7 formed on the sample bed 5, and finally flows into the
`vacuum processing chamber 1 and is exhausted.
`An absolute pressure vacuum gauge 18 is provided in
`the heat transfer gas line 15 between the sample 6 and
`the supply valve 17, and a heat transfer gas exhaust line
`19 is also connected between them. The heat transfer
`gas line 19 is provided with an exhaust valve 20, and is
`connected, in this case, to the evacuator for decom
`pressing and exhausting the inside of the vacuum pro
`cessing chamber 1.
`A controller 25 is connected to the absolute pressure
`vacuum gauge 18 so that the pressure of the vacuum
`gauge 18 can be monitored, and is connected also to the
`flow rate regulation valve 16, the supply valve 17 and
`the exhaust valve 20 so that it can control them, respec
`tively. The controller 25 stores the relation between the
`heat transfer gas pressure and the sample temperature
`and can control the flow rate regulator 16, the supply
`valve 17 and the exhaust valve 20 by the pressure of the
`heat transfer gas supply line 15 measured by the abso
`lute pressure vacuum gauge 18. The relation between
`the heat transfer gas pressure and the sample tempera
`ture that is stored in the controller 25 is the values
`which is obtained by making examination in advance
`and, in this case, which is obtained by cooling the sam
`ple bed 5 by a cooling medium at a predetermined tem
`perature, and holding the sample 6 on the cooled sample
`bed 5 and supplying the heat transfer gas under the back
`of the sample 6.
`Reference numeral 21 represents a bypass line for the
`bypasses of the flow rate regulator 16; 22 is a valve
`disposed in the bypass line 21; 23 is an exhaust line
`connected between the supply valve 17 of the heat
`transfer gas supply line 15 and the flow rate regulator
`16; and 24 is a valve disposed in the exhaust line 23. The
`bypass line 21 and the exhaust line 23 are disposed in
`order to exhaust the heat transfer gas remaining in the
`heat transfer gas supply line 15 between the main valve
`of a heat transfer gas supply source (not shown in the
`drawing) and the supply valve 17 when the operation of '
`the apparatus is stopped. V
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`The apparatus thus constructed is used in the follow
`ing way. The sample 6 is placed on the sample bed 5 by
`the conveyor device not shown in the drawing. A pro
`cessing gas is supplied at a predetermined flow rate into
`the vacuum processing chamber 1 through the gas in
`troduction pipe 3. The vacuum processing chamber 1 is
`evacuated by the evacuator from the exhaust port 4 and
`the pressure in the vacuum processing chamber 1 is
`controlled to a predetermined degree of vacuum by an
`absolute pressure vacuum gauge (not shown) disposed
`in the vacuum processing chamber and a control valve
`(not shown) disposed in the exhaust system. Thereafter,
`high frequency power is supplied by the high frequency
`power supply 12 to the sample bed 5 through the match
`ing circuit 11, and DC. power is supplied, too, by the
`DC. power supply 14 to the sample bed 5 through the
`high frequency cutoff circuit 13. When this high fre
`quency power is applied, discharge takes place inside
`the vacuum processing chamber 1 and the processing
`gas is converted to plasma, so that etching of the sample
`6 is started.
`When DC. voltage is applied, an electrostatic at
`tracting force takes place and the sample 6 is held on the
`dielectric ?lm 7. After the sample 6 is held by the sam
`ple bed 5 through the dielectric ?lm 7, the heat transfer
`gas is supplied under the back of the sample 6 through
`the heat transfer gas supply line 15. The sample bed 5 is
`cooled by a cooling medium kept at a predetermined
`temperature. Accordingly, the heat input to the sample
`6 by the plasma processing is transferred to the sample
`bed 5 through the heat transfer gas on the back of the
`sample 6 and through the dielectric ?lm 7 and is re
`moved by the temperature regulator (not shown in the
`drawing) through the cooling medium circulating
`through the sample bed 5.
`When the sample 6 is electrostatically held as in this
`embodiment, the gap between the sample 6 and the
`dielectric ?lm 7 can be made sufficiently small. Accord
`ingly, the heat transfer gas under the back of the sample
`6 can be within the pressure range of from about 1 Torr
`to around 10 Torr. In other words, the major propor
`tion of the gap (except for the groove, and the like)
`between the back of the sample 6 and the upper surface
`of the dielectric ?lm 7 are narrower than the mean free
`path of the heat transfer gas and the gap of such por
`tions is a molecular ?ow region of the heat transfer gas.
`Therefore, the quantity of heat transfer is determined by
`the number of molecules of the heat transfer gas, that is,
`by the pressure of the heat transfer gas, and the heat
`transfer coef?cient is approximately proportional to the
`heat transfer gas pressure on the back of the sample 6 as
`shown in FIG. 2.
`Accordingly, though depending on the performance
`of the heat regulator when the temperature of the sam
`ple bed 5 is lowered beforehand by the maximum capac
`ity of the temperature regulator, the temperature of the
`sample bed 5 has the following relation with the quan
`tity of heat inputted to the sample 6:
`
`6
`transfer gas under the back of the sample 6 and the heat
`transfer coef?cient. When, for example, the sample 6 is
`processed while the sample bed 5 is cooled by a cooling
`medium at —60 ° C. and the sample 6 is cooled to -30
`° 0, this processing is carried out in the following way.
`The measured values and proportional expression are
`experimentally determined and stored in the controller
`25 beforehand. The ?ow rate regulator 16 is controlled
`by the controller 25, while the value of the pressure
`measured by the absolute pressure guage 18 being read,
`so that the pressure of the heat transfer gas supplied
`from the heat transfer gas supply line 15 may be equal to
`the one corresponding to the temperature of the sample,
`that is, - 30 ° C., in this case. Thus, the pressure is set to
`the predetermined pressure value by regulating the heat
`transfer gas flow rate. In this manner, the sample 6 is
`controlled to the set temperature.
`The result of the experiment, shows that the heat
`transfer coef?cient was from about 50 to about 500 and
`the time constant was from 20 to about 2 seconds when
`the heat transfer gas pressure on the back was from 1 to
`10 Torrs. When the sample temperature is changed
`during processing, about 70% of the desired tempera
`ture can be accomplished in a time which is approxi
`mately the sum of the control time of the pressure plus
`the time constant. Therefore, when the sample tempera
`ture is to be controlled to a lower temperature, so as to
`change rapidly the sample temperature to a desired
`temperature, taken is a method of closing the exhaust
`valve 20 by the controller 25, opening the supply valve
`17 so as to pass the heat transfer gas from the flow rate
`controller 16 at a maximum flow rate, speeding up the
`rise of the pressure of the heat transfer gas under the
`back of the sample 6 and increasing the heat transfer
`quantity. (Ordinarily, the valves 22 and 24 are kept
`closed.) Thereafter, the pressure of the heat transfer gas
`is returned to the predetermined pressure and is stabi
`lized. In this manner, the sample temperature can be
`rapidly lowered to the predetermined temperature.
`When the sample 6 is changed to a further lower tem
`perature after the processing performed at this tempera
`ture or at a certain time during this processing, the same
`operation as described above is carried out and the
`pressure is stabilized to the predetermined one corre
`sponding to the lower temperature.
`When the sample temperature is to be adjusted to a
`higher temperature, on the contrary, the pressure of the
`heat transfer gas under the back of the sample 6 must be
`lowered. However, it is not easy to do so since the
`pressure of the heat transfer gas under the back of the
`sample 6 which is electrostatically held hardly lowers
`because the gap between the back of the sample 6 and
`the dielectric ?lm 7 is small and the gas in the gap can
`not escape easily. For this reason, even if the supply of
`the heat transfer gas is stopped, the pressure drop is
`small. Accordingly, the flow rate regulator 16 decreases
`the ?ow of the gas by the operation of the controller 25
`and the heat transfer gas in the heat transfer gas supply
`line 15 is once exhausted by opening the exhaust value
`20. Then, the heat transfer gas is supplied at a ?ow rate
`where the predetermined pressure is attained and is kept
`stably under a lower pressure. In this manner, the sam
`ple temperature can be rapidly raised to the predeter
`mined one. In this case, the temperature is raised by use
`of the heat input to the sample 6.
`The control operation described above can control
`arbitrarily and rapidly the temperature of the sample 6,
`
`35
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`40
`
`45
`
`55
`
`(quantity of heat inputted to sample 6)=(heat
`transfer coefficient of heat transfer gas under back
`of sample 6)><(temperature of sample
`6-tempcrature of sample bed 5)
`
`where the difference between temperatures of the di
`electric ?lm 7 formed on the sample bed 5 and the sam
`ple bed 5 can be neglected.
`The temperature of the sample can be controlled
`appropriately by using the relation between the heat
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`5,320,982
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`even during the processing of the sample, by controlling
`the pressure of the heat transfer gas under the back of
`the sample 6 without changing the temperature of the
`sample bed.
`Since the temperature of the sample can be controlled
`rapidly during processing as described above, the selec
`tion ratio of the etched material to the base can be in
`creased by lowering the temperature of the sample, for
`example, near the end of etching, if a large selection
`ratio is required at that point.
`In the embodiment described above, the sample tem
`perature can be controlled more and sufficiently rapidly
`than the conventional technique in which the tempera
`ture of the sample bed is changed during the processing.
`Therefore, the present invention will be suitable for
`sheet~type dry etching for fabricating more miniatur
`ized integrated circuitry by the use of a low temperature
`technique.
`Since the temperature can be controlled quickly, and
`there is no need to carry out the processing on a plural
`ity of sample beds having mutually different tempera
`tures, the sample conveying time is unnecessary and the
`through-put can therefore be improved. Since the num
`bers of sample beds and cooling devices are small, the
`25
`scale of the apparatus is small and the apparatus is more
`economical.
`The present invention is not particularly limited to
`the embodiment given above but can be applied suitably
`to the following cases:
`(1) The case where vacuum processing is carried out
`by changing and controlling the sample temperature.
`Here, the term “vacuum processing” includes not only
`processings such as an etching by use of plasma, CVD
`processing, cleaning processing, ashing processing, cor
`rosion-proo?ng processing and sputtering processing
`but also vacuum processings which do not utilize
`plasma such as ion implantation processing, vacuum
`deposition processing, and MBE processing.
`(2) The case where the samples which are processed
`at different temperatures are placed sequentially on the
`same sample bed and are subjected continuously to
`vacuum processing. For example, the sample is sub
`jected to high precision plasma etching below a pm
`order at different temperatures below 0° C.
`45
`Next, another embodiment of the present invention
`will be explained with reference to FIGS. 3 and 4. FIG.
`3 shows in this case a microwave plasma etching appa
`ratus.
`In these drawings, like reference numerals are used to
`identify like constituent members as in FIG. 1 and the
`explanation of such members will be omitted. The dif
`ferences between these drawings and FIG. 1 are that a
`microwave is used as means for generating plasma in
`side the vacuum processing chamber and that feedback
`control is employed by measuring the sample tempera
`ture and controlling the heat transfer gas pressure.
`A waveguide 32 is ?tted to the upper part of the
`vacuum processing chamber 30 through an insulation
`window 31 so disposed as to face the sample bed 5. A
`magnetron 33 for generating microwaves is connected
`to the end portion of the waveguide 32. A solenoid coil
`34 for generating a magnetic ?eld inside the vacuum
`processing chamber 30 is ?tted around the outer periph
`ery of the vacuum processing chamber 30 above the
`sample bed 5. Reference numeral 35 represents a gas
`introduction pipe for introducing the processing gas
`into the vacuum processing chamber 30.
`
`8
`A temperature detection sensor 28 (such as a thermo
`couple, a ?uorescent temperature detector) for detect
`ing the temperature of the sample 6 from its back is
`disposed on the sample bed 5. The temperature detec
`tion sensor 28 is connected to the controller 29. The
`controller 29 receives a detection signal from the tem
`perature detection sensor 28 and controls the flow rate
`regulator 16. The rest of the construction is the same as
`those of the embodiment described above.
`In the apparatus having the construction as described
`above, the microwave is oscillated by the magnetron 33
`and the magnetic ?eld is generated by the solenoid coil
`34, so that the plasma of the processing gas is generated
`inside the vacuum processing chamber 30. After this
`plasma is generated, the DC voltage is applied to the
`sample bed 5 in the same way as in the ?rst embodiment
`described already and the sample 6 is held electrostati
`cally on the sample bed 5. The application of high fre
`quency power to the sample bed 5 in the microwave
`etching apparatus is used for controlling the incidence
`of ions in the plasma to the sample 6. The heat transfer
`gas is supplied under the back of the sample 6 held on
`the sample bed 5 in the same way as in the ?rst embodi
`ment.
`The controller 29 inputs the temperature detection
`signal detected by the temperature detection sensor 28
`in this case, controls the flow rate regulator 16 so that
`the temperature of the sample 6 may be a predetermined
`set temperature, and controls also the heat transfer gas
`pressure on the back of the sample 6. The flow rate
`regulator 16 is controlled on the basis of the relation
`with the sample temperature in the same way as in the
`first embodiment.
`When the plasma processing is carried out, for exam
`ple, by setting the sample temperature to a predeter
`mined temperature lower than the room temperature as
`shown in FIG. 4 (Case I), the sample is rapidly cooled
`by increasing tee heat transfer gas flow rate to the maxi
`mum in the region a-b so as to raise the pressure. In the
`region b-c where the sample temperature reaches sub
`stantially the predetermined one, the heat transfer gas
`flow rate is lowered and stabilized. In the region c-d
`where the plasma processing started, the heat transfer
`gas pressure is controlled while detecting the sample
`temperature because there is the heat input to the sam
`ple due to the plasma processing. In this case, the heat
`transfer gas pressure rises gradually.
`Next, in the case where the sample is subjected to the
`plasma processing at a predetermined further lower
`temperature after the processing of Case I (Case II), the
`processing can be carried out in the same way as in the
`Case I described above. The processings in the regions
`d-e, e-f and f-g are carried out in the same way as in the
`regions a-b, b-c and c-d, respectively.
`When the sample is processed by raising the tempera
`ture (Case III), on the contrary, the supply of the heat
`transfer gas is stopped in the region g-h and cooling of
`the sample is prevented by exhausing the remaining heat
`transfer gas. The sample is then heated by the radiant
`heat inside the vacuum processing chamber, or the like.
`In such a case where the temperature is set to be higher
`than the room temperature, a rapid temperature rise is
`made by utilizing the heat input from the plasma. In the
`region h-i where the sample temperature has reached
`substantially the predetermined one, the heat transfer
`gas flow rate is stabilized. In the region i—j where the
`plasma processing is started, the control is made in the
`same Way as in the region c—d. When the plasma pro
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`cessing is completed and the sample temperature must
`sample being spaced from said sample installation
`be returned to the room temperature, the sample is
`surface by a gap; and
`cooled by raising the heat transfer gas pressure as in the
`means for supplying a heat transfer gas into the gap
`region j-k.
`between the back surface of said sample and said
`This embodiment provides the same effects as those
`sample installation surface of said sample bed;
`of the ?rst embodiment, and makes it possible to con
`control means for changing the pressure of said heat
`duct temperature control with higher accuracy because
`transfer gas to establish a plurality of processing
`the heat transfer gas pressure is controlled while detect
`temperatures of said sample; and
`ing the sample temperature.
`processing means for processing said sample at said
`According to the present invention, only the sample
`plurality of processing temperatures so as to
`temperature can be changed without changing the tem
`achieve a plurality of predetermined processing
`perature of the sample bed and consequently, the sam
`conditions, and for rapid change from one of said
`ple temperature can be quickly controlled to different
`processing temperatures to another.
`temperatures.
`8. A vacuum processing apparatus according to claim
`What is claimed is:
`7, wherein said control means stores the relation be
`1. A vacuum processing method for processing a
`tween the pressure of said heat transfer gas and said
`sample having front and back surfaces under a reduced
`sample temperature.
`pressure, comprising the steps of:
`9. A vacuum processing apparatus according to claim
`cooling a sample bed by a cooling medium kept at a
`7, wherein said sample bed includes detection means for
`temperature lower than an etching temperature;
`detecting the temperature of said sample, and said con
`holding said sample on a sample installation surface of
`trol means controls the pressure of said heat transfer gas
`said sample bed, said back surface of said sample
`in accordance