`Hurwitt et al.
`
`I IIIII IIIIIIII Ill lllll lllll lllll lllll lllll lllll lllll lllll llllll Ill lllll llll
`US005130005A
`5,130,005
`{11] Patent Number:
`{45] Date of Patent:
`Jul. 14, 1992
`
`[75]
`
`[54] MAGNETRON SPUITER COATING
`METHOD AND APPARATUS WITH
`ROTATING MAGNET CATHODE
`Inventors: Steven Hurwitt, Park Ridge, N.J.;
`Robert Hieronymi, Rock Cavern;
`Israel Wagner, Monsey, both of N.Y.
`Assignee: Materials Research Corporation,
`Orangeburg, N.Y.
`Appl. No.: 626,987
`Dec. 13, 1990
`Filed:
`
`[73]
`
`[21]
`[22]
`
`[63]
`
`[51J
`[52)
`
`[58]
`
`[56}
`
`Related U.S. AppliCJ1tion Data
`Continuation-in-part of Ser. No. 606,701, Oct. 31, 1990,
`abandoned, which is a continuation-in-part of Ser. No.
`570,943, Aug. 22, 1990, which is a continuation-in-part
`of Ser. No. 339,308, Apr. 17, 1989, Pat. No. 4,957,605.
`Int. a.s .............................................. C23C 14/35
`U.S. Cl. ............................ 204/192.12; 204/298.2;
`204/298.09
`Field of Search ...................... 204/192.12, 298.09,
`204/298.2
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,393,142 7/1968 Moseson ......................... 204/298.06
`3,956,093 5/1976 McLeod ......................... 204/192.12
`4,162,954 7/1979 Morrison, Jr .................. 204/298.19
`4,180,450 12/1979 Morrison, Jr .................. 204/i98.19
`4,239,611 12/1980 Morrison, Jr .................. 204/298.19
`4,265,729 5/1981 Morrison, Jr .................. 204/298.19
`4,401,539 8/1983 Abe et al. ....................... 204/192.13
`4,444,643 4/1984 Garrett ............................. 204/298.2
`4,461,688 7/1984 Morrison, Jr .................. 204/192.12
`4,498,969 2/1985 Ramachandran .............. 204/192.12
`4,525,264 6/1985 Hoffman ......................... 204/298.22
`4,631,106 12/1986 Nakazato et al .................... 156/345
`4,714,536 12/1987 Freeman et al .................. 204/298.2
`4,746,417 5/1988 Ferenbach et al ............... 204/298.2
`4,761,219 8/1988 Sasaki et al .................... 204/298.37
`4,793,911 12/1988 Kemmerer et al ............. 204/298.27
`4,892,633 1/1990 Welty ............................. 204/192.12
`4,943,361 7/1990 Kakehi et al ................... 204/192.32
`
`4,995,958 2/1991 Anderson et al. ............... 204/298.2
`5,026,470 6/1991 Bonyhard et al. ............. 204/298.16
`
`FOREIGN PATENT DOCUMENTS
`0054201 6/1982 European Pat. Off ........ 204/298.37
`0211412 7/1986 European Pat. Off .......... 204/298.2
`0334347 3/1989 European Pat. Off .......... 204/298.2
`0365249 10/1989 European Pat. Off .......... 204/298.2
`2707144 8/1977 Fed. Rep. of Germany ... 204/298.2
`59-215484 12/1984 Japan ................................ 204/298.2
`61-291971 12/1986 Japan ................................ 204/298.2
`63-149374 6/1988 Japan ................................ 204/298.2
`63-290275 11/1988 Japan ................................ 204/298.2
`63-307270 12/1988 Japan ................................ 204/298.2
`Primary Examiner-Aaron Weisstuch
`Attorney, Agent, or Firm-Wood, Herron & Evans
`[57]
`ABSTRACT
`A target of a thickness, which varies across its radius
`according to the amount of material required to be
`sputtered, is supported in a nest in a chamber of a sput(cid:173)
`ter coating apparatus. Positioned behind the nest is a
`rotating magnet carrier having arranged thereon in a
`closed loop a permanent or electro magnetic strip, but
`preferably a flexible permanently magnetic material,
`with portions near the rim of the target and portions
`near, but not on, the target center about which the
`magnet rotates. The magnetic loop is transversely po(cid:173)
`Jarized with one pole toward the target rim and one
`toward the target center so that its field will enclose the
`rim of the target within a magnetic tunnel that traps a
`plasma over the target. Lumped magnets across the
`center from the strip support the plasma near the center
`so as to cause some sputtering at the target center.
`Other lumped magnets adjacent the strip help sharpen
`the field so that a desired distribution of sputtering can
`be achieved. Enclosed in a sealed space behind and in
`thermal contact with the target nest is the carrier from
`which the magnets project to facilitate the flow of cool(cid:173)
`ing fluid across the back surface of the nest to cool the
`target as the carrier rotates.
`
`22 Claims, 5 Drawing Sheets
`
`Page 1 of 14
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`5,130,005
`
`MAGNETRON SPU1TER COATING METHOD
`AND APPARATUS WITH ROTATING MAGNET
`CATHODE
`
`This application is a continuation-in-part of U.S. pa(cid:173)
`tent application Ser. No. 07/606,701, filed Oct. 31, 1990
`entitled "Magnetron Sputter Coating Apparatus with
`Rotating Cathode Magnet," now abandoned, which is a
`continuation-in-part of U.S.
`patent
`application 10
`07/570,943, filed Aug. 22, 1990 entitled "Sputter Coat(cid:173)
`ing Process Control Method and Apparatus," which is
`continuation-in-part of U.S. patent application Ser. No.
`07/339,308, filed Apr. 17, 1989 entitled "Method and
`Apparatus for Sputter Coating Stepped Wafers," now
`U.S. Pat. No. 4,957,605.
`
`FIELD OF THE INVENTION
`The present invention relates to sputter coating and
`more particularly to magnetron enhanced sputter coat- 20
`ing processes and apparatus employing magnets which
`· are movable with respect to a sputtering cathode target.
`
`2
`coated. Varying the relative parameters affecting the
`energization of the two target regions provides control
`of coating uniformity on the substrate surfaces, which is
`especially important on the differently facing surfaces
`5 of stepped semiconductor wafers. The aforereferenced
`patent application particularly describes effects on the
`coating caused by the target geometry and by the elec(cid:173)
`trical parameters relating to the energization of the
`target and plasmas.
`In magnetron sputter coating processes, the sputter-
`ing of materials from the sputtering target occurs most
`~pidly into regions of the target where the plasma
`trapped by the magnetic field is the most dense. This
`causes a proportionate consumption or erosion of the
`15 sputtering' material from the target surface. The erosion
`of sputtering material from other portions of the sput(cid:173)
`tering target surface generally occurs at a rate which
`varies in proportion to the strength and/or duration of
`the plasma over that portion of the target surface.
`In the prior art it has been proposed in certain appli(cid:173)
`cations to move the magnetic field in relation to the
`sputtering target surface either by movement of the
`target or movement of the magnetic field. A purpose of
`the relative movement of the target or magnetic field
`with respect to each other is, in many cases, to provide
`a more uniform erosion or consumption of the sputter-
`ing target material over the surface of the target. Such
`devices have for many reasons been unsatisfactory.
`In sputtering from a sputtering target while moving
`the target with respect to the magnetic field, a desirable
`erosion pattern is sometimes achieved for purposes of
`uniformly consuming the target material, but often such
`a pattern does not provide the proper or desired distri(cid:173)
`bution of sputter coating material onto the surface of
`the substrate being coated. Furthermore, such devices
`of the prior art have insufficiently controlled the distri-
`bution of the plasma or the duration of the moving
`plasma with respect to the target surface so as to affect
`a desired non-uniform erosion pattern.
`In addition, rotating magnet devices of the prior art
`have not effectively provided for the sputtering of the
`entire surface of the target. It has been found that the
`absence of at least some sputtering from any given re(cid:173)
`gion of the target may cause redeposition of the material
`sputtering from elsewhere on the target onto those
`regions where no sputtering is occurring. This causes a
`build-up of sputtering material which is undesirable.
`Accordingly, there is a need to provide a method and
`apparatus for sputter coating substrates which employs
`2 magnet which is movable relative to the sputtering
`target and which is capable of precisely controlling the
`distribution of sputtering on the target surface in its
`entirety.
`When the magnet structure and target are rotated
`relative to each other, the prior art devices have failed
`to provide for sufficient sputtering from certain regions
`of the target surface, such as the center and edge re(cid:173)
`gions of the target, and further have failed to effectively
`distribute the sputtering across the target surface in a
`manner which is effective to produce the desired ero(cid:173)
`sion pattern to yield the proper coating uniformity on
`the substrate.
`
`BACKGROUND OF THE INVENTION
`Sputter coating is a process carried out in a vacuum 25
`chamber which is filled with a generally chemically
`inert gas in which a substrate is coated with a material
`from a target of sputtering material subjected to a nega(cid:173)
`tive electrical potential with respect to the chamber
`wall or other anode. The potential gradient adjacent the 30
`target surface causes electrons to be emitted from the
`target which, on their way to the chamber anode which
`is usually formed in part by the grounded chamber wall,
`strike and ionize some of the inert gas. The positive ions
`formed are then attracted to the negative target which 35
`they strike, transferring momentum to the target mate(cid:173)
`rial, and ejecting particles of the material from the tar(cid:173)
`get surface. The substrate to be coated, which is posi(cid:173)
`tioned in the chamber usually with its surface facing the
`target, receives some of the ejected particles which 40
`adhere to and coat the substrate surface.
`With magnetron sputtering, a magnetic field
`is
`formed over the target surface, usually including mag(cid:173)
`netic field lines parallel to the target surface, and, in
`many applications, in the form of a closed magnetic 45
`tunnel. The magnetic field causes the electrons emitted
`to move in curved spiral paths which trap them in re(cid:173)
`gions proximate the target surface enclosed by the field,
`thereby increasing the rate of electron collisions with
`gas atoms, which in turn increase the ionization of the 50
`gas and the efficiency of the sputtering process.
`In the commonly assigned and copending U.S. patent
`application Ser. No. 07/339,308, filed Apr. 17, 1989,
`entitled "Method and Apparatus for Sputter Coating
`Stepped Wafers", now U.S. Pat. No. 4,957,605, ex- 55
`pressly incorporated herein by reference, a sputter coat(cid:173)
`ing apparatus and method are disclosed in which a con(cid:173)
`cave annular target is provided with concentric annular
`electromagnets which cause the formation of a pair of
`concentric plasma rings. The plasma rings are alter- 60
`nately energized by alternately supplying current to
`energize the magnet coils while the target power level
`is switched in synchronization with the switching of the
`current to the magnetic coils. This causes different rates
`of sputtering from inner and outer concentric regions of 65
`the target surface, with the sputtering from each region
`causing different distribution characteristics of the sput(cid:173)
`tered material deposited on the substrate or wafer being
`
`SUMMARY OF THE INVENTION
`It is an objective of the present invention to provide
`a sputtering coating method and apparatus in which a
`magnet, positioned behind a sputtering target opposite
`the sputtering surface to generate a plasma trapping
`
`Page 7 of 14
`
`
`
`5,130,005
`
`4
`field provided by the magnetic loop to sharpen the field
`at various points. Particularly, certain of the Jumped
`magnets are provided opposite the axis of rotation from
`the point of the loop where the magnet most closely
`approaches the axis. In this way, a small portion of the
`magnetic field, which docs not otherwise extend across
`the central portion of the target, is drawn across the
`center to provide some degree of erosion to, and sput(cid:173)
`tering from, the central portion of the target. In addi(cid:173)
`tion, in accordance with certain embodiments of the
`present invention, the lumped magnets are provided at
`the outermost reaches of the loop near the edge of the
`target to shape the field more precisely in these regions.
`In accordance with further objectives of the present
`IS invention, the target itself is shaped in a way to cooper(cid:173)
`ate with the sputtering pattern created by the magnetic
`configuration so as to provide for a maximum utilization
`of the target material. In this respect, the target is of
`non-uniform thickness and is, for example, in the illus(cid:173)
`trated embodiment, more particularly thicker at the
`outer regions near the outer edge thereof.
`In alternative embodiments, particularly wher.e there
`may be some advantage to varying or adjusting the
`magnetic field strength, any of the magnets, and partic(cid:173)
`ularly the closed loop magnet, may be electromagnets.
`In accordance with further objectives of the present
`invention, the target is bonded or otherwise secured in
`intimate heat conducting contact with a target nest. A
`closed cavity is provided behind the target nest enclos(cid:173)
`ing the rotating magnet. A turbulent layer of water or
`other cooling fluid is maintained by injecting cooling
`water into the cavity behind the nest. The fluid is in(cid:173)
`jected into the space near the center of the target assem-
`bly near the axis of rotation of the magnet so as to flow
`through a narrow space between the rotating magnet
`and the back surface of the target nest. In this space, the
`cooling fluid is propelled along the back surface of the
`nest and outwardly by the rotation of the magnet struc-
`ture, and more particularly by the raised surface of the
`magnets themselves, so as to provide a turbulent skin of
`cooling water adjacent the surface of the nest improv(cid:173)
`ing the flow of the water and the
`These and other objectives and advantages of the
`present invention will be more readily apparent from
`the following detailed description of the drawings in
`which:
`
`20
`
`3
`closed magnetic field or tunnel over the sputtering tar(cid:173)
`get surface, is shaped and rotated so as to produce a
`desired average sputtering distribution across the sur(cid:173)
`face of the target.
`It is a more particular objective of the present invcn- S
`tion to provide a rotating magnet magnetron sputtering
`apparatus that avoids unsputtered areas of the target,
`and thus avoids a buildup by redeposition of sputtered
`material on the target.
`It is another objective of the present invention to 10
`provide a rotating magnet sputtering target apparatus
`and method having a magnet structure which is con(cid:173)
`figurable to produce a desired coating deposition on the
`substrate when the magnet structure is rotated during
`sputtering.
`It is a further objective of the present invention to
`provide the rotating magnet structure in a sputter coat(cid:173)
`ing apparatus wherein the rotating magnet structure
`facilitates the circulation of cooling fluid for the sputter-
`ing cathode assembly.
`According to the principles of the present invention
`there is provided a sputter coating apparatus having a
`sputtering target included in a cathode assembly with a
`magnet located behind the sputtering target so as to
`produce a closed magnetic field over the target surface. 2S
`The magnet is rotatably mounted so as to rotate the
`magnetic field over the surface of the sputtering target.
`The magnet is configured with respect to the target to
`cause sputtering from the center of the target to the
`outer rim of the target at a rate which varies with the 30
`radius from the center in a desired manner.
`In the preferred and illustrated embodiment of the
`present invention, the magnet is preferably a permanent
`magnet which includes a closed loop of magnetic mate(cid:173)
`rial formed of a flexible magnetic strip. The strip has its 3S
`poles spaced transversely across the strip, preferably
`generally in the plane in which the closed loop lies. The
`magnet, which is formed of flexible laminated strips of
`magnet impregnated plastic, is arranged on a rotating
`plate behind the sputtering target in a shape having a 40
`plurality of curves including a plurality of outwardly
`convex curves, some near the outer rim of the target,
`and at least one point at which the strip passes near, but
`not through, the target center. The magnet is shaped in
`such a way that the plasma trapped by the magnetic 4S
`field will be present over various portions of the sput(cid:173)
`tering target at various radii from the center for prede(cid:173)
`termined amounts of time so as to provide a desired
`erosion pattern on the target surface.
`According to the preferred embodiment of the pres- SO
`cnt invention, the magnet is polarized in such a way that
`one pole faces the outer edge of the rotating plate while
`the other pole faces the axis of rotation so that, particu(cid:173)
`larly at the outer edge, the field emerges from the mag(cid:173)
`net 111d surrounds the outer rim of the target to facilitate SS
`sputtering from the target rim, without the nee<' to
`provide an enlarged magnet structure extending beyond
`the target outer rim.
`In addition, according to a preferred embodiment of
`the present invention, fixed lumped magnets of different 60
`magnetic material arc positioned at various points along
`the magnetic loop so as to selectively influence portions
`of the magnetic field to provide certain desired field
`shapes. Particularly, according to certain preferred
`embodiments of the present invention, the lumped mag- 6S
`nets arc oriented with one pole toward the target and
`one away from the target so that the magnetic fields
`produced by the lumped magnets cooperate with the
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a cross-sectional view through a target
`assembly of one preferred embodiment of an apparatus
`embodying principles of the present invention.
`FIG. 2 is a view taken generally along lines 2-2 of
`FIG. 1 illustrating the face of the rotatable plate and
`magnet assembly.
`FIG. 3 is a cross-sectional view along lines 3-3 of
`FIG. 2.
`FIG. 4 is a fragmentary cross-sectional view along
`lines 4-1 of FIG. 2.
`FIG. S is a view similar to FIG. 2 illustrating an
`alternative rotating magnet assembly configuration.
`FIG. 6 is a set of diagrams A through D illustrating
`the preferred magnetic pole orientation for the main
`magnet according to certain features of the present
`invention.
`FIG. 7 is a set of diagrams A through D illustrating a
`preferred auxiliary magnetic arrangement according to
`certain features of the present invention.
`
`Page 8 of 14
`
`
`
`5
`FIG. 8 is a set of diagrams A and B illustrating a
`preferred auxiliary magnetic arrangement according to
`other features of the present invention.
`
`5,130,005
`
`6
`the above incorporated U.S. Pat. Nos. 4,909,675 and
`4,915,564.
`In this preferred embodiment, the wafer 21 is sup(cid:173)
`ported in a plane perpendicular to, and concentric with,
`S a central axis 27 of the main chamber 10, which is also
`concentric with the hole 15 in the plenum wall 14. Sur(cid:173)
`rounding the wafer 21 on the holder 25 is a disk 29
`which at least partially protects the holder 25 from an
`excessive accumulation of coating intended for but
`which missed, the surface 22 of the wafer 21. Details of
`the sputtering apparatus of which the processing cham-
`ber 10 is a part including particularly details of the
`wafer transport 17, wafer holder 25, and backplane
`section 16, are described and illustrated in U.S. Pat.
`Nos. 4,909,695 and 4,915,564 incorporated by reference
`above.
`The cathode assembly module 20 includes two assem-
`blies, a removable cathode assembly 30 and a fixed
`assembly portion 31. The fixed assembly portion 31 is an
`annular enclosure rigidly mounted in sealed relationship
`against the plenum wall 14 surrounding the opening 15.
`It includes a cylindrical metal side wall 33 of the cham(cid:173)
`ber 10. which is electrically grounded to the frame 14 of
`the plenum, a wafer holder shield 34 which surrounds
`the opening 15 and a chamber door frame assembly 35.
`The cathode assembly 30 is mounted to a hinged door
`assembly 37 which removably but sealably supports the
`cathode assembly 30 to the fixed assembly 31. The cath-
`ode assembly 30 carries the sputtering target 40, which
`is a circular target having a continuous smooth concave
`sputtering surface 41 and a back surface 39. The assem-
`bly 30 supports the target 40 with its axis in alignment
`with the axis 27 of the chamber 10 and with its sputter(cid:173)
`ing surface 41 facing the surface 22 of the wafer 21 to be
`coated.
`The target 40 is supported in a target nest 42 having
`a front surface 43 conforming to surface 39 and concen(cid:173)
`tric with axis 27. The back surface 39 of the target 40 is
`soldered or otherwise bonded to the front surface 43 of
`the nest 42, in intimate thermal contact therewith. The
`target back surface 39 is a cooling surface which, when
`the target 40 is mounted in holder 42, conforms to and
`lies in close cooling contact with the surface 43 of the
`holder 42. Behind the nest 42, opposite the cooling
`surface 43 thereof, is a space 44 for the circulation of
`cooling liquid, which is generally water, to remove heat
`generated in the target 40 during sputtering by cooling
`the heat conductive target holder 42. The cooling fluid
`is circulated into and out of the space 44 from an inlet
`port 45 to an outlet port 46 in a magnet assembly 50, as
`described below. The space 44 is enclosed behind the
`nest 42 by a housing structure 48 onto which the nest 42
`is rigidly supported, and to which it is secured by bolts
`49.
`The shapes of the surfaces of the target 40 are prefer(cid:173)
`ably such that all the target 40 is capable of being
`formed by turning a block of sputtering material on a
`lathe. The target holder 40 is made of a heat conductive
`and electrically conductive material, preferably hard
`tempered OFHC copper or Alloy 110.
`The magnet assembly SO includes a shaft 51 having a
`threaded end 52 by which the shaft 51 is rigidly
`mounted in a threaded bore 53 at the center of the back
`surface of the nest 42. The assembly SO also includes a
`rotatable magnet carrier assembly 55 which includes a
`circular disk 56 of non-magnetic stainless steel or other
`such material having a central hole 57 therein at which
`the disk 56 is rigidly mounted to a sleeve assembly 58
`
`25
`
`30
`
`DETAILED DESCRIPTION OF ORA WINGS
`Magnetron sputtering devices of the type to which
`the present invention relates are described in the follow(cid:173)
`ing commonly assigned U.S. patents and copending
`patent applications which are hereby expressly incorpo(cid:173)
`rated in their entirety into this application by reference: 10
`U.S. Pat. Nos. 4,909,695 and 4,915,564 entitled
`"Method and Apparatus for Handling and Processing
`Wafer-Like Materials"; and,
`U.S. patent application Ser. No. 07 /339,308, filed
`Apr. 17, 1989, now U.S. Pat. No. 4,957,605, entitled 15
`"Method and Apparatus for Sputter Coating Stepped
`Wafers."
`FIG. 1 illustrates, in cross-section, a sputter coating
`processing chamber 10 of a sputter coating apparatus
`according to principles of the present invention. The 20
`chamber 10 is a portion of the sputter processing appa(cid:173)
`ratus disclosed in U.S. Pat. No. 4,909,695. The process(cid:173)
`ing chamber 10 is a vacuum processing chamber formed
`of an isolated section of a main chamber 11. The main
`chamber 11 is isolated from the atmosphere of the ma(cid:173)
`chine. environment 12 by a plenum wall 14. The pro(cid:173)
`cessing chamber 10 is capable of communicating with
`the main chamber 11 throughout opening 15 (shown
`sealed) in the plenum wall 14.
`As more fully described in U.S. Pat. No. 4,909,695,
`the sealing of the opening 15 isolates the chamber 10
`from the main processing chamber 11 by the selective
`movement of a processing chamber backplane section
`16 against a portion of a disk shaped rotary wafer trans- 35
`port member 17 clamping the transport member 17
`between the backplane section 16 and the plenum wall
`14 in a sealing relationship (as shown), thereby enclos(cid:173)
`ing a backplane space 19 within the processing chamber
`JO and isolating the processing chamber 10 from the 4-0
`main chamber 11.
`Opposite the backplane section 16, on the front plane
`side of the transport member 17, the processing cham(cid:173)
`ber 10 is isolated from the machine environment 12 with
`a cathode assembly module 20 mounted in a vacuum 45
`sealing relationship against the plenum wall 14 surround
`the opening 15. The module 20, or processing chamber
`frontplane section, cooperates with the backplane sec(cid:173)
`tion 16 and the transport member 17 to form the sealed
`isolated processing chamber which is isolated from both 50
`the main chamber 11 and the machine external environ(cid:173)
`ment 12.
`Within the processing chamber 10 is a substrate or
`workpiece 21 in the form of a flat silicon wafer or disk
`which has the surface 22 upon which a coating is to be ss
`deposited in a sputter coating process to be performed
`within the processing chamber 10. The wafer 21 is held
`by a set of clips or other retaining devices 24 in a wafer
`holder 25 resiliently carried by the transport member
`17. The transport member 17 is rotatable within the 60
`main chamber to bring the holder 25, and the workpiece
`or wafer 21 into alignment with the hole 15 so that the
`processing chamber 10 can be formed around the wafer
`21 on the holder 25 by transverse movement of the
`backplane section 16 to move the member 17 against the 65
`plenum wall 14. The transport member portion 17 is a
`transversely movable ring carried by a rotatable index
`plate which is not shown, but described more fully in
`
`Page 9 of 14
`
`
`
`5,130,005
`
`8
`7
`approximately 45 degrees toward the central axis 27
`rotatably mounted through a bearing assembly through
`the housing 48 and to the nest 42 to rotate about the
`while the magnets 91 and 92 are oriented parallel to the
`shaft 51 on the axis 27. The rotatable magnet assembly
`axis 27 (see FIGS. 3 and 4, respectively).
`In FIG. 5, an alternative embodiment of magnet
`further includes a magnet structure 60 rigidly mounted
`on the disk 56 to rotate therewith. The magnet 60 sur- S structure 60a is illustrated which is differently shaped
`than the magnet 60 of the embodiment of FIG. 2. The
`rounds the axis 27 and lies beneath or behind the nest 42,
`ribbon magnet 80a of the magnet structure 60a is se-
`opposite the front surface 43 thereof, and close enough
`thereto to generate a closed magnetic field above the
`cured to the disk 56 through appropriately shaped
`sputtering surface 41 of the target 40 mounted on the
`clamping blocks 81a-85a. In this embodiment there is
`surface 43 of the nest 42.
`10 also provided additional permanent magnets 95, 96, 97
`and 98 clamped to the block 82a by clamps 99 and
`The shaft 51 has a cooling fluid inlet duct 62 extend-
`ing therethrough which communicates with the inlet
`oriented with their north poles facing towards the tar-
`port 45 to the interior cooling chamber 44 between the
`get and nest, their south poles toward the plate 56 and
`nest 42 and the housing 48. The housing 48 has mounted
`their axes generally parallel to the axis 27 of the cathode
`near the edge thereof a cooling fluid outlet duct 63 IS assembly.
`which communicates with the fluid outlet port 46 in the
`The magnets are arranged on the carrier plate 56 to
`cooling space 44.
`cause sputtering from the target 40 to be distributed in
`Mounted to the back of the housing 48 is a bracket 64
`such a way as to achieve a desired distribution, usually
`to which is mounted a magnet rotary drive motor 65.
`a uniform distribution, of the coating material on the
`The motor 65 has an output shaft 66 with a cogged 20 substrate 20. With a generally circular target 40 and
`circular substrate 20, with a magnet assembly that ro(cid:173)
`drive wheel 67 mounted at the end thereof for driving a
`cogged drive belt 68. The belt 68 extends around a
`cogged drive wheel 69 attached to a drive shaft 70
`tates about the axis 27 through the centers of the target
`40 and substrate 20, as in the illustrated embodiments,
`which is rotatably mounted on the housing 48 extending
`therethrough and having a free end 71 to which is 25 the relative average sputtering rate will be constant at
`any given radius from the target center, but may vary
`mounted a drive gear 72. The drive gear 72 is positioned
`within the space 44 where it engages a mating gear 74
`with the distance from the axis 27. The variation will be
`a function of the average intensity of ion bombardment
`attached to the disk 56 of the rotatable magnet assembly
`55. Accordingly, the motor 65, when energized, rotates
`of the target surface at any given radius, which is in turn
`the magnet assembly 55 to rotate the magnet 60 behind 30 a function of the average plasma density over the area
`of the target at that the given radius. This variation will
`the target nest 42 to rotate the magnetic field over the
`sputtering surface 41 of the target 40. The details of the
`generally be proportional to the portion of a circle at
`construction of the magnet structure 60 and its arrange-
`any given radius which is enclosed by the magnetic
`ment on the magnet assembly 55 can be better under-
`field. Integrating the plasma density around such circles
`atood by reference to FIGS. l-4.
`35 will yield the approximate relative sputtering from the
`Referring to FIG. 2, according to one preferred em-
`target surface 41 at the given radius from the target
`bodiment of the present invention, the magnet structure
`center.
`60 is shown supported on the disk or plate 56. The
`To obtain erosion of all parts of the target, it is neces-
`magnet structure 60 is a strip of flexible magnet impreg-
`sary that the plasma be present for some portion of the
`nated plastic made up of a laminated plurality of flexible 40 rotation of the magnet assembly over every region of
`plastic magnetic ribbons 80, for example 24 in number,
`the target. This is desirable even