United States Patent [191
`Kadomura et al.
`
`I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll 111111111111111111
`US005981913A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,981,913
`Nov. 9, 1999
`
`[54] STATIC ELECTRICITY CHUCK AND WAFER
`STAGE
`
`[75]
`
`Inventors: Shingo Kadomura; Tomohide Jozaki;
`Shinsuke Hirano; Kinya Miyashita,
`all of Kanagawa; Seiichirou Miyata,
`Yamaguchi; Yoshiaki Tatsumi,
`Kanagawa, all of Japan
`
`[73] A.&5ignee: Sony Corporation, 1bkyo, Japan
`
`[21] Appl. No.: 08/821,334
`
`[22] Filed:
`
`Mar. 20, 1997
`
`[30]
`
`Foreign Application Priority Data
`
`Mar. 22, 1996
`
`[JP]
`
`Japan ....................... ,, ........... 8-065625
`
`[51]
`
`Int. Cl.6
`
`............................. HOSB 3/68; C23C 16/00;
`B23B 5/22
`[52] U.S. Cl . ........................ 219/444.1; 118/724; 279/128
`[58] Field of Search ..................................... 219/443, 457,
`219/464, 544; 279/128, 134; 361/234; 269/8;
`IJ8/724-725
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,166,856 11/1992 Llporace et al. ........................ 361/233
`5,191,506
`3/1993 Logan et al. ............................ 361/234
`5,280,156
`1/1994 Niori et al. ............................. 361/234
`5,374,807 12/1994 Yahav et al. ............................ 219/464
`5,663,865
`9/1997 Kawada et al. ......................... 361/234
`
`Primary Examiner-Teresa Walberg
`Assistant Examiner--,_"fam Paik
`Attorney, Agent, or Firm-Hill & Simpson
`
`[57]
`
`ABSTRACT
`
`There are provided a static electricity chuck which can vary
`the temperature of a wafer in a short time without adversely
`effecting throughput, and a wafer stage having the static
`electricity chuck. The static electricity chuck includes a
`dielectric member 4 formed of insulating material, an elec(cid:173)
`trode 5 of conductor which is disposed at the lower side of
`the dielectric member 4, and a heater 6 which is disposed at
`the lower side of the electrode 5 and heats the dielectric
`member 4. The wafer stage 1 includes the static electricity
`chuck which is provided on a metal jacket having cooling
`apparatus.
`
`5,151,845
`
`9/1992 Watanabe ct al. ...................... 361/234
`
`9 Claims, 3 Drawing Sheets
`
`9b
`
`2
`
`Tokyo Electron Limited
`EXHIBIT 1002
`IPR Petition for
`U.S. Patent No. RE40,264
`
`

`

`U.S. Patent
`
`Nov. 9, 1999
`
`Sheet 1 of 3
`
`5,981,913
`
`,----
`
`"',j- ____ ,
`cd
`'
`
`

`

`Nov. 9, 1999
`Nov. 9, 1999
`
`Sheet 2 of 3
`Sheet 2 of 3
`
`5,981,913
`5,981,913
`
`0::
`w
`...J
`
`...J -J:
`
`
`
`YaTIIHOYaMOd—_*—saeOpa9@@ZL7MYOMLSN|EbebbSE
`ogJOUNNOS8k#4M/\
`oewaMOd!I_sviaik:|{!i!1i2etyoveeraiHe!
`
`ezM1%T,,rt
`
`MaMOdSNIHOLVIN
`ONIHOLVIN()TT].6¢Sid
`YATIONLNOD69zJOYNOS
`
`0
`
`~
`
`
`
`
`
`
`U.S. Patent
`U.S. Patent
`
`~I
`
`as
`,...
`,...
`,...
`
`II)
`
`N
`•
`
`CJ -u.
`
`--------,
`" N
`
`---------,
`
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`I
`
`O')
`N
`
`0::
`w
`...J
`...J
`0
`0::
`1-z
`0
`0
`
`co
`N
`
`,...J_/
`
`N
`
`,...
`
`

`

`U.S. Patent
`
`Nov. 9, 1999
`
`Sheet 3 of 3
`
`5,981,913
`
`w
`
`34
`
`32
`
`31
`
`30
`
`31
`
`30
`
`FIG. 3A
`
`FIG. 38
`
`FIG. 3C
`
`

`

`5,981,913
`
`1
`STATIC ELECTRICITY CHUCK AND WAFER
`STAGE
`
`BACKGROUND OF THE INVENTION
`
`1. Field of the Invention
`The present invention relates to a static electricity chuck
`which is used to adsorptively hold a wafer in a manufac(cid:173)
`turing apparatus for a semiconductor device such as an
`etching device or the like, and a wafer stage having the static 10
`electricity chuck.
`2. Description of Related Art
`Recently, a technical requirement for the micromachining
`in a super LSI technique has been increasingly severer. For
`example, with respect to an etching treatment, it is indis(cid:173)
`pensable to use a treatment method which can achieve both
`a high-precision micromachining which suppress a dimen(cid:173)
`sional conversion difference as much as possible, and a high
`selection ratio to a back layer.
`It is well known that when materials other than oxide film 20
`are subjected to a plasma etching treatment, a so-called side
`wall protection film is used to ensure an anisotropic shape.
`That is, when reaction products generated during the plasma
`etching treatment are re-dissociated in plasma, and these
`re-dissociated materials are deposited as various kinds of 25
`deposits such as organic polymer, etc. on the side walls of a
`pattern to thereby form a side wall protection film. The side
`wall protection film thus formed serves to protect the side
`walls from being etched.
`As described above, the side wall protection film is
`formed by the deposits which are generated from the reac(cid:173)
`tion products. Therefore, when a pattern formed by an
`etching treatment is convex, the thickness of the side wall
`protection wall is relatively larger as the width of the pattern 35
`is finer, and thus the whole pattern width is liable to be still
`smaller than a desired width. Accordingly, as described
`above, the fineness of each pattern is promoted, and if the
`pattern width is small (narrow), the dimensional precision of
`the pattern thus obtained is reduced when the anisotropy of 40
`the etching is achieved by using the side wall protection
`film.
`In order to solve the above disadvantage, a technique of
`performing an etching treatment while exhausting at high
`speed has been recently attempted and considered to ensure
`the dimensional precision. In this high-speed exhausting
`process, a pump having a higher exhausting speed than a
`conventional etching treatment apparatus is secured, and the
`conductance of etching gas is improved to shorten the
`residence time of the etching gas during the etching 50
`treatment, whereby the re-dissociation of reaction products
`in plasma is suppressed during the etching treatment.
`According to the high-speed exhausting process as described
`above, the amount of deposits which are generated by the
`re-dissociation of the reaction products can be greatly 55
`reduced, so that the absolute value of the dimensional
`conversion difference and the dispersion thereof can be
`remarkably suppressed.
`However, in the high-speed exhausting process as
`described above, the reaction products are quickly 60
`exhausted, resulting in reduction of a supply source for
`forming a side wall protection film. Therefore, a side wall
`protection film is not formed at a sufficient thickness, and the
`anisotropic shape is not sufficiently ensured. Accordingly,
`there occurs a new problem that the precision in shape of a 65
`pattern obtained when an overetching is carried out is
`lowered.
`
`2
`That is, when a substrate-applied bias is lowered to ensure
`the selection ratio to the back layer in the overetching
`process, occurrence of side etching or notching is unavoid(cid:173)
`able because the side wall protection film is thin and thus
`5 weak. On the other hand, when the applying bias is increased
`to ensure the shape precision, the selection ratio to the back
`layer is lowered.
`In view of the foregoing, a low-temperature etching
`technique for cooling a wafer so that the temperature of the
`water is reduced to zero degree or less in the etching
`treatment is proposed as a technique which can solve the
`trade-off problem between the selection ratio and the shape
`precision as described above and achieve both the selection
`ratio and the anisotropic shape. This low-temperature etch-
`15 ing technique is proposed by K. Tsujimoto, et al. in "Pro(cid:173)
`ceedings of Symposium on Dry Process" pp 42-49 on 24th
`and 25th of Oct. 1988 in Tokyo.
`According to this technique, radical reaction is suppressed
`by reducing the temperature of samples to keep the anisot(cid:173)
`ropy even under a low substrate-applied bias.
`However, this low-temperature etching technique has the
`following disadvantages.
`First, it is difficult to process those materials like W
`polyside for which reaction products have different vapor(cid:173)
`ization pressures. If the temperature of samples are reduced
`to a low temperature suitable for etching of polysilicon to
`etch W polyside because reaction products such as WCt,
`WOxCly, etc. which are generated by the etching treatment
`30 of WSix have low vaporization pressure, it would be impos(cid:173)
`sible to perform the etching of WSix.
`Secondly, ti. T (the difference between a set temperature of
`a sample stand and wafer temperature) increases during the
`etching treatment That is, for example, in a contact hole
`processing work, the setting of the low temperature is
`effective to ensure the selection ratio to the back layer of Si,
`however, the low-temperature setting induces the contact
`hole to be tapered in shape due to excessive deposition of
`polymer. Therefore, as described above, it is difficult to set
`the low-temperature condition, and incident energy must be
`increased to dissociate Si-0 bonds in the contact hole
`processing work, resulting in increase of ti. T.
`Accordingly, in the low-temperature etching treatment as
`described above, the etching must be performed at an
`45 incompletely low temperature.
`In order to solve this disadvantage, it may be considered
`that the set temperature of a sample such as wafer or the like
`is varied between materials whose reaction products are
`different in vaporization pressure, or between an just etching
`treatment and an over etching treatment. However, if the set
`temperature is varied in the midst of the etching treatment,
`the throughput would be reduced, and it is inconvenient on
`cost.
`Accordingly, there has been required a mechanism which
`can vary the temperature of a wafer in short time with no
`effect on the throughput, that is, which enables quick tem(cid:173)
`perature reduction and increase.
`
`OBJECT AND SUMMARY OF THE INVENTION
`
`An object of the present invention is to provide a static
`electricity chuck which can vary the temperature of a wafer
`in short time without adversely effecting throughput, and a
`wafer stage for the static electricity chuck.
`In order to attain the above object, according to a first
`aspect of the present invention, a static electricity chuck
`comprises a dielectric member formed of insulating
`
`

`

`5,981,913
`
`3
`material, an electrode which is disposed below the dielectric
`member and formed of electric conductor, and a heater
`which is disposed below the electrode and adapted to heat
`the dielectric member.
`According to the static electricity chuck as described
`above, the static electricity chuck and the heater is unified
`into one body, the heat of the heater is quickly transferred
`through the electrode to the dielectric member, and thus a
`wafer which is mounted and held on the dielectric member
`is quickly heated.
`The electrode may be formed of a soldering layer which
`is used to fix the dielectric member. In this case, the
`dielectric member and the electrode can be surely joined to
`each other, and the electrode can be formed at a small
`thickness. In addition, since the electrode is formed of
`soldering material, that is, metal or alloy having high heat
`conductivity, the heat conduction from the heater to the
`dielectric member is performed more quickly.
`Sintered material may be directly used as the dielectric
`member, or the dielectric member may be formed by a
`thermal spraying method. In this case, the degree of freedom
`in manufacturing is high, and the cost is low. With respect
`to the shape of the dielectric member, it may be designed to
`have a disc portion which forms an adsorbing face for the
`wafer, and a cylinder portion which extends from the side
`peripheral edge downwardly. In this case, if the cylinder
`portion is disposed to cover the side peripheral portion of the
`electrode, occurrence of a leak current on the side surface of
`the electrode due to plasma can be prevented, for example,
`when the static electricity chuck is used for the plasma
`treatment of the plasma treatment apparatus.
`With respect to the mount of the heater on the electrode,
`the heater may be mounted through an insulating member
`having high thermal conductivity on the electrode. In this
`case, aluminum nitride is most suitably used as the insulat(cid:173)
`ing member. The interposition of the insulating member
`between the electrode and the heater prevents current flow
`from the electrode to the heater, and the delay of thermal
`conduction from the heater due to the insulating member can
`be prevented because the insulating member has high ther(cid:173)
`mal conductivity (for example, the thermal conductivity of
`aluminum nitride is equal to 0.235 [cal/cm.sec. 0 C.].
`The heater may be designed in a thin film type. In this
`case, a metal plate is preferably provided between the
`insulating member and the heater or below the heater. The
`provision of the metal plate keeps sufficient mechanical
`strength for the whole static electricity chuck irrespective of
`the thin-film design of the heater. Further, if the metal plate
`is provided above the heater, it serves as a heat transfer plate
`for quickly transferring the heat from the heater to the
`insulating plate. On the other hand, if the metal plate is
`provided below the heater, the metal plate serves as a heat
`transfer plate for transferring cool heat from a metal jacket
`or the like to the heater side.
`Particularly when the heater is designed not only in a thin
`film structure, but also in a spiral shape, the whole mechani-
`cal strength of the heater is reduced, and the heat conduc(cid:173)
`tivity thereof is also reduced. However, as described above,
`the reduction of these physical properties can be compen- 60
`sated by providing the metal plate. Further, when the insu(cid:173)
`lating member is formed of aluminum nitride, it is preferable
`that the metal plate is formed of molybdenum having high
`heat conductivity of0.37 [cal/cm.sec. 0 C.] because the metal
`plate sufficiently functions as the heat transfer plate as 65
`described above. Further, Molybdenum has a linear expan(cid:173)
`sion coefficient of 5.7xl0- 6
`0 C. which is near to the linear
`/
`
`4
`expansion coefficient of ceramics (for example, aluminum
`nitride has a linear expansion coefficient of 5.lxl0- 6
`0 C.).
`/
`Therefore, if molybdenum is used for the metal plate, even
`when the metal plate suffers a thermal stress due to appli-
`5 cation of repetitive cycle of cooling and heating, the insu(cid:173)
`lating member and the dielectric member disposed on the
`insulating member can be prevented from being cracked or
`exfoliated due to the thermal stress.
`The insulating member may be designed to have a cyl-
`10 inder portion which extends from the side peripheral edge
`thereof downwardly, and the heater may be disposed inside
`the cylinder portion. In this case, the side surfaces of the
`heater can be surely covered by the cylinder portion.
`Therefore, when the static electricity chuck is used in a
`plasma treatment by a plasma treatment apparatus, occur-
`15 rence of a leak current on the side surfaces of the heater due
`to plasma can be prevented. Further, if a flange portion is
`formed in the cylinder portion so as to extend outwardly
`from the lower end edge of the cylinder portion, the insu(cid:173)
`lating member is mechanically reinforced by the flange
`20 portion.
`Further, according to a second aspect of the present
`invention, a wafer stage is characterized in that a static
`electricity chuck comprising a dielectric member formed of
`insulating material, an electrode which is disposed below the
`25 dielectric member and formed of conductor, and a heater
`which is disposed below the electrode and adapted to heat
`the dielectric member, are provided on a metal jacket having
`cooling means.
`According to the wafer stage, the static electricity chuck
`30 according to the first aspect of the present invention is
`provided on the metal jacket having the cooling means.
`Therefore, not only the wafer can be quickly heated by the
`heater provided to the static electricity chuck, but also the
`wafer can be cooled through the static electricity chuck by
`35 the metal jacket.
`As described above, according to the static electricity
`chuck of the present invention, the heater and the static
`electricity chuck are unified into one body, whereby the heat
`of the heater is quickly transferred through the electrode to
`40 the dielectric member and thus the wafer which is mounted
`and held on the dielectric member is quickly heated.
`Accordingly, for example, when the static electricity chuck
`is applied to an etching apparatus, a temperature switching
`operation from a low temperature to a high temperature can
`45 be performed in short time.
`Further, according to the wafer stage of the present
`invention, the static electricity chuck is provided on the
`metal jacket having the cooling means. Therefore, not only
`the heating, but also cooling can be quickly performed, so
`50 that the switching operation of the wafer temperature can be
`performed in short time. Accordingly, as compared with a
`conventional etching process which carries out an etching
`treatment sequentially at plural times while varying the
`wafer temperature, the etching treatment of the present
`55 invention can be performed without adversely effecting the
`throughput while using the advantage of the low(cid:173)
`temperature etching treatment more effectively.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a diagram showing the construction of a wafer
`stage of the present invention, in which only a static elec(cid:173)
`tricity chuck is illustrated as a cross-sectional view;
`FIG. 2 is a diagram showing the construction of an
`etching apparatus using the wafer stage shown in FIG. 1; and
`FIGS. 3A to 3C are cross-sectional views showing a series
`of a dry etching treatment method using the etching appa(cid:173)
`ratus shown in FIG. 2 in a step order.
`
`

`

`5
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`
`5,981,913
`
`6
`plates 9a and 9b as described above is hermetically accom(cid:173)
`modated in the cylinder portion 7b of the insulator 7. Metal
`or alloy having high thermal conductivity is preferably used
`for the metal plates 9a and 9b in order to quickly transfer the
`5 heat of the heater 6 to the dielectric member 4 or quickly
`transfer the cool heat from the metal jacket 2 to the heater
`6. In this embodiment, a molybdenum plate of about 2 mm
`in thickness is used. Further, insulating coating as shown in
`FIG. 1 of oxide film or the like is provided on the inner
`surfaces of the metal plates 9a and 9b, thereby preventing
`current flow from the heater 6 to the metal plates 9a and 9b.
`The metal plate 9a is joined to the dielectric member 7 by
`soldering, and the metal plate 9b is joined to the metal jacket
`2 by soldering. Here, like the soldering material serving as
`the electrode 5, alloy which is formed of titanium tin,
`15 antimony and magnesium is used as the soldering material
`for the metal plates 9a and 9b.
`In the static electricity chuck 3, the gap between the
`dielectric member 4 and the insulator 7 is covered by
`insulator of resin or the like (not shown) so that the electrode
`20 5 formed of the soldering layer is prevented from being
`exposed to the outside at the side peripheral edge thereof. If
`the side peripheral edge of the electrode 5 is covered by the
`insulator (not shown) as described above, there can be
`prevented occurrence of leak current at the side peripheral
`25 edge of the electrode 5 due to plasma even when the static
`electricity chuck 3 is used for the plasma treatment in the
`plasma treatment apparatus.
`In the static electricity chuck 3 is embedded a pusher pin
`(not shown) for pushing up the wafer which is mounted and
`30 held on the dielectric member 4, and the pusher pin is
`connected to a retracting mechanism (not shown) for pro(cid:173)
`jecting the pusher pin from the surface of the dielectric
`member 4 into the outside and embedding the pusher pin
`into the dielectric member 4.
`Next, a method of using the wafer stage 1 having the static
`electricity chuck 3 will be described on the basis of the case
`where the wafer stage 1 of this embodiment is used in a
`plasma etching apparatus 10 shown in FIG. 2.
`First, the plasma etching apparatus (hereinafter referred to
`as "etching apparatus") 10 will be described. The plasma
`etching apparatus 10 is designed to have a helicon-wave
`plasma generating source in which two RF antennas are
`disposed, and a stage which is movable upwardly and
`downwardly. Specifically, the plasma etching apparatus 10
`45 comprises a diffusion chamber 11, RF antennas 12 which are
`disposed at the upper side of the diffusion chamber 11, an RF
`antenna 13 which is disposed in a loop form on a top plate
`lla of the diffusion chamber 11, a multipole magnet 14
`which is disposed at the outside of the lower portion of the
`50 diffusion chamber 11 and adapted to form Cusp magnetic
`field for suppressing extinction of electrons on the wall of
`the stage. Each of the RF antennas 12 is provided so as to
`surround a belljar comprising a cylindrical quartz tube
`which has a diameter of 350 mm and is formed at the upper
`55 portion of the diffusion chamber 12. The RF antennas 12 are
`designed so that plasma of M=l mode stands. Further, a
`solenoid coil assembly 16 which comprises an inner periph(cid:173)
`eral coil and an outer peripheral coil is disposed at the
`outside of these antennas 12. The inner peripheral coil of the
`60 solenoid coil assembly 16 contributes to propagation of
`Helicon wave, and the outer peripheral coil contributes to
`transport of the generated plasma. The RF antennas 12 are
`connected to a power source 18 through a matching network
`17, and the RF antenna 13 is connected to a power source 20
`65 through a matching network 19.
`The wafer stage 1 for supporting and fixing a wafer W
`serving as a sample is provided in the diffusion chamber 11,
`
`10
`
`Preferred embodiments according to the present invention
`will be described hereunder with reference to the accompa(cid:173)
`nying drawings.
`FIG. 1 shows an embodiment of a wafer stage according
`to the present invention. In FIG. 1, reference numeral 1
`represents a wafer stage. The wafer stage 1 is constructed so
`that a static electricity chuck 3 of an embodiment of the
`present invention is fixedly mounted on a metal jacket 2.
`The metal jacket 2 is designed to have cooling means (not
`shown) as described above, and it serves to transfer cool heat
`from the cooling means to the static electricity chuck 3
`disposed on the metal jacket 2.
`The static electricity chuck 3 is designed in a substantially
`cylindrical (disc) shape and comprises a dielectric member
`4 formed of insulating material, an electrode 5 which is
`disposed below the lower surface of the dielectric member
`4, a heater 6 disposed below the electrode 5, and an insulator
`7 interposed between the electrode 5 and the heater 6. The
`dielectric member 4 comprises a disc-shaped ceramic plate
`having about 0.2 mm in thickness, which is formed of
`insulating material having high thermal conductivity such as
`sapphire (thermal conductivity: 0.1 [cal/cm.sec. 0 C.]) or alu(cid:173)
`mina (thermal conductivity: 0.05 [ cal/cm.sec 0 C.]). In this
`embodiment, the dielectric member 4 comprises a sintered
`member which is formed in advance.
`Any material may be used for the electrode 5 insofar as it
`is formed of conductor such as metal or alloy. In this
`embodiment, the electrode 5 is formed of a soldering layer
`for fixing the dielectric member 4 on the insulator 7, that is,
`a soldering material of about 0.5 mm in thickness which is
`provided between the insulator 7 and the dielectric member
`4. Specifically, an alloy which is formed of titanium, tin, 35
`antimony and magnesium is used as the soldering material.
`The electrode 5 is connected through a wire to a high voltage
`source (as not shown in FIG. 1). By applying a DC voltage
`to the electrode 5, the dielectric 4 has an absorptive force.
`The insulator 7 comprise a disc portion 7a which is
`brought into contact with the electrode 5, that is, the sol(cid:173)
`dering layer, a cylinder portion 7b which extends down(cid:173)
`wardly from the side peripheral edge of the disc portion 7a,
`and a flange portion 7c which extends outwardly from the
`lower end edge of the cylinder portion 7b, and it is formed
`of an insulating material having high thermal conductivity at
`a thickness of about 2 mm as a whole. As the insulating
`material may be used aluminum nitride (AIN) (thermal
`conductivity: 0.235 [cal/cm.sec. 0 C.]). In this embodiment,
`the insulator 7 is formed of aluminum nitride.
`In this embodiment, the heater 6 is formed of an Fe-Cr-
`5%Al-0.5%Y alloy, and it has a spiral form in a plan view.
`Further, the heater 6 is formed as a thin film of about 0.1 mm
`in thickness and about 2 to 3 mm in width. As not shown, the
`heater 6 is connected through a wire to a power source, and
`the heater 6 generates heat of about 2 kW.
`The heater 6 is provided with an insulating member 8 so
`that the insulating member 8 is embedded in the gap of the
`spiral heater pattern, and with this structure, the heater 6
`forms a disc shape while reinforced by the insulating mem(cid:173)
`ber 8. In this embodiment, aluminum nitride is used as the
`insulating member 8.
`The disc member comprising the heater 6 and the insu(cid:173)
`lating member 8 is attached to a metal plate 9a on the upper
`surface thereof and to a metal plate 9b on the lower surface
`thereof. The heater 6 which is sandwiched between the metal
`
`40
`
`

`

`5,981,913
`
`7
`and an exhaust port 21 for exhausting gas in the diffusion
`chamber 11 is formed in the diffusion chamber 11 and
`intercommunicates with a negative pressure means (not
`shown) such as a vacuum pump or the like. The wafer stage
`1 is connected to a bias power source 22 for controlling the 5
`energy of incident ions to the wafer W.
`
`8
`
`First step (main etching)
`
`Etching gas
`Pressure
`Source power
`RF bias
`Wafer stage temperature
`
`Cl2/0 2
`10 mTorr
`1500 W
`100W
`50 degrees
`
`450/50 seem
`
`With respect to the temperature adjustment of the wafer,
`the heating operation is performed by the heater 6 of the
`static electricity chuck 3 provided to the wafer stage 1, the
`cooling operation is performed by the chiller 25, and the fine
`adjustment of the wafer temperature is performed by the
`cooling control of the controller 29 as described above.
`
`The metal jacket 2 of the wafer stage 1 is connected to a
`chiller 25 through refrigerant pipes 23 and 24, and further
`connected to a fluorescent fiber thermometer 26 for detect- 10
`ing the temperature of the wafer W. The chiller 25 supplies
`the metal jacket 2 of the wafer stage 1 through the refrigerant
`pipe 22 with gas refrigerant which is formed of He gas or the
`like and whose temperature is set to 100° C. or less, and
`receives refrigerant which is returned from the metal jacket 15
`2 through the refrigerant pipe 22 to further cool the refrig(cid:173)
`erant to a predetermined temperature. Accordingly, the
`wafer W which is held and fixed on the wafer stage 1 is
`cooled by circulating the gas refrigerant. That is, the cooling
`means of the present invention is constructed by the chiller 20
`25, the refrigerant pipes 23 and 24 and the gas refrigerant
`which is circulated from the chiller 25 to the metal jacket 2.
`
`An electrical control valve 27 which can operated at an
`extremely low temperature is disposed in the refrigerant pipe
`23 connected to the chiller 25, and an electrical control valve
`27 which can operate at an extremely low temperature is
`disposed in a bypass pipe 28 between the refrigerant pipes
`23 and 24.
`
`Here, the cooling level of the wafer Wis controlled by the
`flow amount of the refrigerant which is supplied from the
`chiller 25. That is, in order to cool the metal jacket of the
`wafer stage 1 so that the temperature of the wafer W is
`reduced to a desired temperature, the temperature which is
`detected by the fluorescent fiber thermometer 26 is detected
`by a controller (PID controller) 29, and on the basis of the
`detected temperature and a preset temperature of the wafer
`W, the controller 29 controls the opening/closing degree of
`the electric control valves 27 so as to obtain a gas refrigerant
`flow amount which is predetermined by experiments and
`calculations. In FIG. 2, the detailed construction of an
`etching gas inlet port, a gate valve, etc. is omitted from the
`illustration.
`
`25
`
`30
`
`35
`
`40
`
`Next, in order to perform the overetching treatment of the
`second step which is subsequent to the first step, the dis(cid:173)
`charging operation of the etching apparatus 10 is tempo(cid:173)
`rarily turned out to exhaust the residual gas from the
`diffusion chamber 11 through the exhaust port 21 to the
`outside. Etching gas used in the second step (in this embodi(cid:173)
`ment the same gas as the first step is used) as described later
`is introduced into the diffusion chamber 11, and the gas is
`stabilized to adjust the pressure in the diffusion chamber 11
`to a fixed pressure value. Between the series of operations as
`described above, that is, immediately after the etching
`treatment of the first step is finished, the current supply to the
`heater 6 is stopped, the electric control valve 27 of the
`bypass pipe 28 in the cooling system using the chiller 25 is
`fully closed, the electric control valve 27 of the refrigerant
`pipe 23 is fully opened, and the gas refrigerant below -100
`degrees is supplied from the chiller 25 to the metal jacket 2
`to quickly cool the wafer W.
`By the quick cooling operation, the wafer stage 1 is
`reduced to -50 degrees (the etching temperature as
`described later) in short time ( about 30 seconds). This is
`because as described above, in the wafer stage 1 of the
`present invention, the metal plate 9b of molybdenum having
`high thermal conductivity is joined to the metal jacket 2 by
`the soldering, and the metal plate 9a of molybdenum which
`is provided on the metal plate 9b through the thin-film type
`heater 6 is joined to the insulator 7 by the soldering, so that
`the cool heat from the metal jacket 2 is quickly transferred
`from the metal plate 9b, the heater 6 and the metal plate 9a
`to the insulator 7. In addition, since the insulator 7 is formed
`of aluminum nitride having high thermal conductivity, and
`the electrode 5 is formed of a soldering layer, the cool heat
`50 transferred to the insulator 7 is quickly transferred through
`the insulator 7 and by the electrode 5 to the dielectric
`member 4.
`A series of steps as described above, that is, the sequence
`of the step of turning out the discharge, the step of exhaust(cid:173)
`ing the residual gas in the diffusion chamber 2, the step of
`introducing new etching gas and the step of stabilizing the
`gas need a process time which is longer than or equal to the
`quick cooling. Therefore, the quick cooling operation is not
`the factor which causes increase of the process time required
`for the etching treatment of the wafer W.
`
`Next, a dry etching treatment method using the etching 45
`apparatus 1 will be described with reference to FIGS. 3A to
`3C.
`
`According to this treatment method, W polyside is pro(cid:173)
`cessed by a two-step etching treatment. That is, in this
`embodiment, W polyside comprising a polysilicon layer 32
`and a WSix layer 33 is formed on an Si02 film 31 on a silicon
`substrate 30 as shown in FIG. 3A, and further a photoresist
`pattern 34 is formed on the W polyside. Thereafter, the W
`polyside of the wafer Wis subjected to the etching treatment
`through the photoresist pattern 34 to process the W polyside
`in the pattern corresponding to the photoresist pattern 34. In
`a first step, a main etching is performed at a temperature
`which is slightly higher than the normal temperature, and in
`a subsequent second step, an over etching is performed at a
`low temperature.
`
`55
`
`60
`
`First, the main etching of the first step is performed under
`the following condition at a high temperature (50 degrees)
`which is slightly higher than the normal temperature so that
`the WSix layer 33 and the polysilicon layer 32 are etched
`until a part of the polysilicon layer 32 is left as shown in
`FIG. 3B.
`
`Subsequently, the discharge operation is restarted, and the
`overetching treatment of the second step at the low tem(cid:173)
`perature (-50 degrees) is performed under the following
`65 condition so that a part of the polysilicon layer 32 which is
`left while exposed from the Si02 film as shown in FIG. 3C
`is etched.
`
`

`

`9
`
`Second step (overetching treatment)
`
`Etching gas
`Pressure
`Source power
`RF bias
`Wafer stage temperature
`
`Cl2/0 2
`10 mTorr
`1500 W
`10W
`-50 degrees
`
`450/50 seem
`
`5,981,913
`
`5
`
`35
`
`10
`be performed in short time of about 40 seconds by desig