United States Patent ' [19]
`Ooshio et al.
`
`'
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`[11] Patent Number:
`[45] Date of Patent:
`
`4,645,218
`Feb. 24, 1987
`
`[54] ELECTROSTATIC CHUCK
`[75] Inventors:
`Hirosuke Ooshio; Osamu Watanabe, ‘
`both of Zama, Japan
`,
`[73] Assignee: Kabushiki Kaisha Tokuda Seisakusho,
`Zama, Japan
`[21] Appl. No.: 760,512
`[22] Filed:
`Jul. 30, 1985
`[30]
`Foreign Application Priority Data
`Jul. 31, 1984 [JP]
`Japan .............................. .. 59-117493
`
`[56]
`
`[51] Int. Cl.4 ............................................ .. B25B 11/00
`[52] US. Cl. .................................... .. 279/1 M; 269/8;
`269/13; 361/145; 361/234
`[58] Field of Search ............................. .. 361/145, 234;
`29/DIG. 95; 269/8, 13; 279/1 M, 1 R
`References Cited
`U.S. PATENT DOCUMENTS
`361/234
`4,184,188 l/l980 Briglia
`. 361/234 X
`4,384,918 5/1983 Abe .............. ..
`....... .. 269/8 X
`4,502,094 2/1985 Lewin et a1. ..
`4,554,611 11/1985 Lewin ............................... .. 361/234
`
`FOREIGN PATENT DOCUMENTS
`
`56-85828 7/1981 Japan .
`58-190037 11/1983 Japan .................................... .. 269/8
`1443215 7/1976 United Kingdom .................. .. 269/ 8
`Primary Examiner—-Gil Weidenfeld
`Assistant Examiner-Steven C. Bishop
`Attorney, Agent. or Firm-Schwartz, Jeffery, Schwaab,
`Mack, ‘Blumenthal & Evans
`[57]
`ABSTRACT
`An electrostatic chuck for holding a work by electro
`static forces, which has an electrostatic attraction body
`for attracting the work, an electrostatic conductive
`support body for supporting the electrostatic attraction
`body, channels for passing cooling medium there
`through and cover means for covering the exposed
`surfaces of the support body except a portion thereof
`over which the work is placed. This chuck can not only
`prevent impure matters from generating from the sur
`faces of the support body but also prevent damages due
`to heat.
`
`16 Claims, 6 Drawing Figures
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`LAM Exh 1005-pg 1
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`U.S. Patent Feb. 24, 1987
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`Sheet 1 of2
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`FIG.3
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`U.S. Patent Feb. 24, 1987
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`S‘heet2of2
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`4,645,218
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`FIG.6
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`1
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`ELECTROSTATIC CHU_CK
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`4,645,218
`2
`surfaces of the metal support body other than a portion
`on which the work is attracted.
`In another aspect of the invention, the insulator layer
`is formed of thin ?lms, the cover means is made of
`5 either a ceramic material or a heat resistant resin, and
`the metal support body is formed of a material with a
`suf?ciently high thermal conductivity.
`The present invention is further described with the
`aid of the accompanying drawings, which illustrate
`preferred embodiments by way of an example only. The
`nature, utility and features of this invention will be more
`clearly apparent from the following detailed description
`with respect to the preferred embodiments when read in
`conjunction with the accompanying drawings brie?y
`described below.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`In the accompanying drawings:
`FIG. 1 is an elevational sectional view of the electro
`static chuck and a specimen wafer placed thereon;
`FIG. 2 is a perspective view of the electrostatic
`chuck and the specimen wafer as shown in FIG. 1;
`FIG. 3 is an enlarged elevational sectional view of the
`electrostatic attraction body shown in FIG. 1; and
`FIGS. 4, 5 and 6, respectively, show a second, third
`and fourth embodiments in accordance with the present
`invention.
`
`25
`
`BACKGROUND OF THE INVENTION
`This invention relates to an electrostatic chuck and
`more particularly to an improved electrostatic chuck
`for securing a work by electrostatic forces in a vacuum
`process apparatus such as a dry-etching apparatus.
`In a vacuum microfabrication apparatus such as a
`dry-etching apparatus, a variety of means for securing a
`wafer have been used. In recent years electrostatic
`chucks are used for securing a specimen wafer by elec
`trostatic forces.
`Japanese Patent Laid-Open Publication No.
`85828/ 1981 discloses an electrostatic chuck of a type
`which has a holding portion for holding a wafer. The
`holding portion is so formed that its size is almost the
`same as that of a wafer to be processed. The holding
`portion comprises a ?rst insulator layer, a plurality of
`20
`electrodes provided upon the ?rst insulator layer, and a
`second insulator layer provided upon the plurality of
`electrodes and over the ?rst insulator layer. The other
`portion except the holding portion consists of a metal
`support body such as a stainless steel member.
`In operation, the specimen wafer is placed over the
`holding portion of the electrostatic chuck. When a high
`voltage is applied to the electrodes, the electrostatic
`attractive forces arise and attract and securely hold the
`specimen wafer in position. A vacuum process such as
`etching is done thereafter.
`.
`The above described electrostatic chuck can prevent
`wear and degradation of the second insulator layer
`contacting directly the wafer since the holding portion
`is entirely covered by the specimen wafer. However,
`though the insulator layer is protected from wearing,
`the upper surface of the metal support body is subjected
`to an etching process, with a result that the metallic
`material of the support body may disperse or scatter as
`impurities.
`.
`In addition, although a high temperature during the
`etching process often has an adverse effect on the wa
`fer, no consideration has been made to mitigate heat
`impacts regarding the electrostatic chuck.
`
`SUMMARY OF THE INVENTION
`It is an object of the present invention to provide an
`electrostatic chuck capable of holding a work by elec
`trostatic forces without dispersing impure matters from
`a metallic support body and of preventing damages due
`to high heat.
`In one aspect of the present invention, the electro
`static chuck includes an electrostatic attraction body
`having an electrode and an insulator layer which buries
`the electrode therein. The electrostatic attraction body
`attracts the work on its upper surface. The electrostatic
`chuck further includes below the electrostatic attrac
`tion body an electric conductive metal support body for
`supporting the lower surface of the electrostatic attrac
`tion body. The chuck has also channels for passing
`cooling medium such as cooling water either in the
`metal support body or in the electrostatic attraction
`body, an electric connection portion for supplying volt
`age across the electrode, and cover means placed at
`least on the same side as the electrostatic attraction
`body with respect to the metal support body for cover
`ing the generation of impure matters from the exposed
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`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`Referring ?rst to FIG. 1 in accordance with the ?rst
`embodiment of the present invention, an improved elec
`trostatic chuck with a specimen wafer A as a work
`placed thereon, includes an electrically conductive sup
`port body 1 at the bottom of the chuck. The support
`body 1 has, at its center, a round protrusion 1a with the
`thickness slightly greater than the rest of the body 1.
`The support body 1 is made of a material with a high
`conductivity such as copper or aluminum. To the upper
`surface of the protrusion 1a of the support body 1 is
`applied an electrostatic attraction body 3 in which a
`metallic electrode 2 is accommodated.
`Referring next to FIGS. 2 and 3, the construction of
`the attraction body 3 will be explained in detail. The
`body 3 comprises an insulator layer and an adhesive
`layer 6. The insulator layer has an insulator base ?lm 4
`and a insulator cover ?lm 5. The insulator layer is made
`of an organic resin layer with the thickness of 10 to 100
`um, such as a polyimide layer or a polyester layer. To
`the insulator base ?lm 4 made of polyimide or polyester
`is applied the electrode 2 made of, for example, copper
`?lm with the thickness of 10 to 50 pm. After the elec
`trode 2 is formed in a preselected form, the insulator
`cover ?lm 5 made of polyimide or polyester is applied
`to the electrode 2, placing the electrode 2 between the
`insulator cover ?lm 5 and the insulator base ?lm 4.
`Further, on the bottom of the insulator base ?lm 4 is
`provided the adhesive layer 6.
`The electrode 2 may be made of a metallic ?lm with
`the thickness of less than 2 pm, formed on the insulator
`60
`base ?lm 4 or the insulator cover ?lm 5 by means of
`vacuum evaporation or sputtering.
`In this embodiment, for example, the thicknesses of
`both the insulator base ?lm 4 and the insulator cover
`?lm 5 are 50 pm, respectively, the thickness of the
`copper-made electrode 2 is 18 pm, the adhesive layer 6
`is 40 um, and the entire thickness of the electrostatic
`attraction body 3 amounts to 158 pm. It is desirable that
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`the embodiment, an annular groove 9 is formed around
`the entire periphery of the central protrusion 1a of the
`support body 1. As is the case with respect to the ?rst
`embodiment, an electrostatic attraction body 3 is ?xed
`to the upper surface of a round protrusion la formed by
`digging an annular groove 9. An electric connection
`portion 3a is projected from the main body 3b of the
`attraction body 3 and extended across the groove 9.
`Over the whole upper surfaces of the support body 1
`and the groove 9, with the exception of the circular
`protrusion upon which the specimen wafer A is to be
`placed, a cover plate 8b and a cover ring 80 are placed,
`respectively.
`In this embodiment, the preferred relationships with
`regard to the dimensions of the elements are:
`
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`20
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`3
`the body 3 is formed as thin as possible in order to
`increase heat transmission ef?ciency. Both the electro
`static attraction body 3 and the specimen wafer A have
`circular shapes, respectively. However, the electro
`static attraction body 3 has an attracting surface slightly
`smaller than the surface, to be attracted, of the specimen
`wafer A. A portion of the periphery of the electrostatic
`attraction body 3 is so projected from its circular main
`body 3b as to form an electric connection portion 3a for
`connecting the electrode 2 with an external power sup
`ply, not shown.
`Referring back to FIG. 1, through the support body
`1, there are provided a plurality of channels 7 for pass
`ing cooling medium therethrough in order to cool the
`wafer A. Such channels may be formed in the electro
`static attraction body 3 (shown at 7a in FIG. 3). The
`electrostatic chuck according to the present invention is
`further provided with a cover plate 8 applied onto the
`support body 1 by means of an adhesive The cover plate
`8 has a round aperture 8a at its center for placing the
`wafer A therein. The cover plate 8 can cover the ex
`posedsurfaces except the surface of the protrusion 1a
`on which the wafer A is placed and is formed of a ce
`ramic material such as carbon, quartz, alumina, silicon
`carbide (SiC), or silicon nitride (SiN), etc. The cover
`plate 8 may be formed of a heat-resistant synthetic resin
`such as polyimide or ?uoreoresin, etc. Further, the
`cover plate 8 may be ?xed to the support body 1 by
`means of screws (see element 10 in FIG. 5). In addition,
`the cover plate 8 may be simply placed or clamped upon
`the support body 1 by means of a clamping member
`provided on the periphery of the cover means (See
`element 12 in FIG. 6).
`In accordance with the above-described ?rst embodi
`ment, in operation, the specimen wafer A is placed upon
`35
`the electrostatic attraction body 3, and thereafter a DC
`voltage is applied to the electrode 2. The wafer A is
`thus attracted by means of electrostatic forces and is
`secured on the electrostatic attraction body 3. The elec
`trostatic chuck described above is placed in a vacuum
`40
`chamber, and a vacuum process such as etching opera
`tion, etc. is carried out for the specimen wafer A. In the
`meantime, cooling water is provided through the chan
`nels 7 during the processing.
`It is to be understood that loading and unloading of 45
`the speciment wafer A on the electrosatic chuck are
`done by a loader mechanism, not shown, which is pro
`vided through the support body 1 and which is capable
`of vertically lifting and lowering the wafer A through
`the support body 1. The electrostatic attraction body 3
`and the support body 1 are provided with apertures (not
`shown) to permit the vertical movements of the lifting
`mechanism, respectively.
`Accordingly, with the aforementioned construction
`of the electrostatic chuck in accordance with this inven
`tion, since the exposed surface of the support body 1
`except the surface of protrusion la on which the wafer
`A is placed is covered with the cover plate 8, the mate
`rial of the support body is no longer directly hit by ion
`beams nor scattered during an etching process. In addi
`60
`tion, no impure materials are generated in the vacuum
`processing chamber.
`Moreover, with the aid of cooling water passing
`through the channels in the support body 1, the support
`body 1 is cooled off desirably and consequently the
`specimen wafer A does not suffer damage due to heat.
`In FIG. 4, an electrostatic chuck according to a sec
`ond embodiment of the current invention is shown. In
`
`where
`(b1: the internal diameter of the cover ring 80 placed
`in the groove 9,
`dug: the diameter of the specimen wafer A,
`(b3: the internal diameter of the cover plate 8b, and
`(124: the external diameter of the cover plate 8b.
`It is apparent that in accordance with the second
`embodiment it is also possible, by means of the two
`pieces of the cover members 8b, 8c, to prevent the mate
`rial of the support body 1 from dispersing or scattering,
`by keeping the ion beam impacts away from the support
`body 1. The embodiment also ensures satisfactory cool
`ing effects by the cooling water passing through the
`channels 7.
`Referring to FIG. 5 illustrating the third embodiment
`of the current invention, an electrostatic chuck includes
`an electrostatic attraction body 3 which has an electric
`connection portion 3a extending downward through
`the support body 1 for an electrical connection. This
`structure enables the electrostatic chuck to be con
`nected to a power source directly below the support
`body 3. This construction also ensures to prevent ion
`beam from attacking the upper surface of the support
`body 1.
`Referring next to FIG. 6, the electrostatic chuck in
`accordance with the fourth embodir'nent of the inven
`tion includes a cover ring 80 provided immediately
`below the adjoining portion of a cover plate 8b and the
`electrostatic attraction body 3. The provision of the
`cover members 8b, 8c further ensures to prevent ion
`beam from hitting the upper surface of the support body
`1. Naturally, the fourth embodiment also ensures the
`electrostatic chuck to be connected to a power source
`directly below the support body 1, as is the case with
`the third embodiment described above.
`Preferably, if the support body 1 is made of alumi
`num, an anodic oxidation process should be carried out
`on the surface of the support body 1. In this case‘, an
`anodic oxidation layer forms cover means instead of the
`cover members 8b, 8c.
`As thus has been described it should be clear that in
`accordance with the current invention, it is possible to
`prevent the generation of the impurities by the provi
`sion of the cover means and to prevent the wafer from
`suffering damages due to heat by the provison of the
`cooling means.
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`What is claimed is:
`1. An electrostatic chuck for holding a work such as
`a specimen wafer by electrostatic forces, comprising:
`an electrostatic attraction body including an elec
`trode and an insulator layer which contains and
`insulates said electrode, said insulator layer having
`an upper surface for attracting and securing the
`work;
`an electrically conductive support body for support
`ing a lower surface of said electrostatic attraction
`body, said support body having, at the center of the
`support body, a round protrusion on which the
`electrostatic attraction body is placed;
`channel means provided in at least in one said support
`body and said attraction body for passing a cooling
`medium to cool said electrostatic chuck;
`an electric connection portion for connecting said
`electrode with a power supply; and
`cover means provided at least on the same side as said
`electrostatic attraction body with respect to the
`support body, for covering exposed surfaces of the
`support body except a surface over which the elec
`trostatic attraction body is positioned so that im
`pure materials are prevented from being generated
`therefrom, said cover means being formed of a
`cover plate with an aperture in which the work is
`placed.
`2. An electrostatic chuck as set forth in claim 1 in
`which said insulator layer of said electrostatic attraction
`body is formed of an organic resin layer such as a poly
`imide layer or a polyester layer with a thickness of 10 to
`100 um, and said electrode is made of a metallic ?lm
`with a thickness of 10 to 50 pm.
`3. An electrostatic chuck as set forth in claim 1 in
`which said insulator layer of said electrostatic attraction
`body is formed of an organic resin layer such as a poly
`imide layer or a polyester layer with the thickness of 10
`to 100 um, and said electrode is made of a metallic ?lm
`formed by means of vacuum evaporation or spattering
`with a thickness of less than 2 pm.
`4. An electrostatic chuck as set forth in claim 1 in
`which the cover means is made of a ceramic material.
`5. An electrostatic chuck as set forth in claim 1 in
`which the cover means is made of a heat-resistant syn
`thetic resin.
`6. An electrostatic chuck as set forth in claim 1 in
`which the cover means is in the form of an anodic oxi
`dation layer.
`7. An electrostatic chuck as set forth in claim 1 in
`which the support body comprises a material with a
`high thermal conductivity such as copper or aluminum.
`8. An electrostatic chuck as set forth in claim 1 in
`which the cover means is clamped upon the support
`body by means of a clamping member provided on a
`periphery of the cover means.
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`4,645,218
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`9. An electrostatic chuck as set forth in claim 1 in
`which the attracting surface of said electrostatic attrac
`tion body is smaller than a surface of the work to be
`attracted.
`10. An electrostatic chuck as set forth in claim 1 in
`which said electrostatic attraction body further has an
`adhesive layer as a means to securely affix itself onto the
`support body.
`11. An electrostatic chuck as set forth in claim 1 in
`which an electric connection portion is extended from a
`main body of said electrostatic attraction body out
`wardly between the cover means and the support body
`for connection with an external power source.
`12. An electrostatic chuck as set forth in claim 1 in
`which an electric connection portion is extended out
`wardly from a main body of the electrostatic attraction
`body through said support body for connection to an
`external power source.
`13. An electrostatic chuck as set forth in claim 1 in
`which the cover means is securely affixed onto the
`support body by means of an adhesive.
`14. An electrostatic chuck as set forth in claim 1 in
`which the cover means is securely held onto the support
`body by means of screws.
`15. An electrostatic chuck as set forth in claim 1 in
`which the cover means is simply placed upon the sup
`port body.
`16. An electrostatic chuck for holding a work such as
`a specimen wafer by electrostatic forces, comprising:
`an electrostatic attraction body including an elec
`trode and an insulator layer which contains and
`insulates said electrode, said insulator layer having
`an upper surface for attracting and securing the
`WOrk;
`an electrically conductive support body for support
`ing a lower surface of said electrostatic attraction
`body, said support body having an annular groove
`for forming a protrusion on which the electrostatic
`attraction body is placed,
`channel means provided at least in one of said support
`body and attraction body for passing cooling me
`dium therethrough to cool said electrostatic chuck;
`an electric connection portion for connecting said
`electrode with a power supply; and
`cover means provided at least on the same side as said
`electrostatic attraction body with respect to the
`support body, for covering exposed surfaces of the
`support body except a surface over which the elec
`trostatic attraction body is positioned so that im
`pure materials are prevented from being generated
`therefrom, said cover means comprising a cover
`ring placed in the groove of the support body and
`I a cover plate for covering other surfaces of the
`support body except the groove.
`it
`ll=
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