Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 1 of 41
`
`
`
`
`Exhibit 8
`
`
`
`
`
`
`
`
`

`

`IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIHIIIIII»
`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 2 of 41
`US005565071A
`United States Patent ti9]
`[ii] Patent Number:
`[45] Date of Patent:
`Demaray et al.
`
`5,565,071
`Oct. 15, 1996
`
`[54] INTEGRATED SPUTTERING TARGET
`ASSEMBLY
`
`[75] Inventors: Richard E. Demaray, Portola Valley;
`David E. Berkstresser, Los Gatos;
`Manuel J. Herrera, San Mateo, all of
`Calif.
`
`[73] Assignee: Applied Materials, Inc., Santa Clara,
`Calif.
`
`[21] Appl. No.: 449,618
`[22] Filed: May 24, 1995
`
`Related U.S. Application Data
`
`[60] Division of Ser. No. 236,715, Apr. 29, 1994, Pat. No.
`5,487,822, which is a continuation-in-part of Ser. No. 157,
`763, Nov. 24, 1993, Pat. No. 5,433,835.
`[51] Int. Cl.6 ................................................. C23C 14/34
`[52] U.S. Cl................................ 204/192.12; 204/192.13;
`204/298.03; 204/298.07
`[58] Field of Search ....................... 204/192.12,298.07,
`204/298.09, 298.12, 298.2, 192.13, 298.03
`
`[56]
`
`3,630,881
`3,956,093
`4,100,055
`4,116,806
`
`References Cited
`U.S. PATENT DOCUMENTS
`12/1971 Lester et al........................... 204/298.09
`5/1976 McLeod ............................... 204/192.12
`7/1978 Rainey ................................. 204/298.12
`9/1978 Love et al............................. 204/298.19
`(List continued on next page.)
`FOREIGN PATENT DOCUMENTS
`................................. 204/298.09
`Japan
`1-147061 6/1989
`.................................. 204/298.09
`Japan
`3-140464 6/1991
`Japan
`.................................. 204/298.07
`1/1992
`4-26760
`................................... 204/298.2
`WO90/13137 11/1990
`WIPO
`OTHER PUBLICATIONS
`“Influence of Surface Preparation on the Diffusion Welding
`of High Strength Aluminum Alloys,” Ed. D. J. Stephenson,
`published in Diffusion Bonding 2, pp. 101-110.
`
`“Diffusion Bonding of T1-6A1-4V Alloy: Metallurgical
`Aspects and Mechanical Properties,” Ed. D. J. Stephenson,
`published in Diffusion Bonding 2, pp. 144-157.
`Korman, et al., “Research Study of Diffusion Bonding of
`Refractory Materials, Columbium and Tantalum,” Army
`Materials and Mechanics Research Center, Nov. 10, 1967,
`pp. 1-27.
`S. Pineau, et al., “The Investigation and Production of
`Titanium-Tantalum Junctions Diffusion Bonded at High
`Temperature (855° C. to 920° C.), etc.,” Royal Aerospace
`Establishment, Library Translation 2180, Jan. 1990, pp.
`3-34.
`
`Primary Examiner—Aaron Weisstuch
`Attorney, Agent, or Firm—Janis Biksa
`
`ABSTRACT
`[57]
`A target plate assembly completely covers and seals against
`a top opening of a sputtering processing chamber. Cooling
`liquid connections are provided only from the perimeter of
`the target assembly. When a top vacuum chamber seals the
`side opposite the pressure chamber, the pressure on both
`sides of the target assembly is nearly equalized. Large thin
`target assemblies, such as large flat plates used for flat panel
`displays can be sputtered effectively and uniformly without
`adverse sputtering effects due to target deflection or cooling
`deficiencies.
`
`A target, target backing plate, and cover plate form the target
`plate assembly. The sputtering target assembly includes an
`integral cooling passage. A series of grooves are constructed
`in either the target backing plate or the target backing
`cooling cover plate, which are then securely bonded to one
`another. The sputtering target can be a single monolith with
`a target backing plate or can be securely attached to the
`target backing plate by one of any number of conventional
`bonding methods. Tantalum to titanium, titanium to titanium
`and aluminum to titanium, diffusion bonding can be used.
`
`The energized target assembly is protected from adjacent
`components by overlapping insulators to prevent accidents
`and isolate the target assembly from other components. An
`electrical connection to the target assembly remains uncon­
`nected until a vacuum is produced in the top chamber.
`
`11 Claims, 26 Drawing Sheets
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 3 of 41
`
`5,565,071
`Page 2
`
`U.S. PATENT DOCUMENTS
`8/1979 Chapin ............................. ... 204/192.12
`.. 204/298.18
`Love et al..........................
`11/1979
`.. 204/298.09
`Nishiyama et al.................
`3/1982
`9/1983 Kobayashi et al................. .. 204/298.16
`2/1984 Eilers et al......................... .. 204/298.12
`4/1984 Garrett ............................. .... 204/298.2
`1/1985 Krause ............................. ... 204/192.12
`2/1985 Boys et al.......................... ... 204/298.03
`1/1986 Wickcrsham ................... ... 204/298.12
`7/1987 Lamont, Jr. ...................... ............ 165/1
`
`4,166,018
`4,175,030
`4,318,796
`4,405,436
`4,430,190
`4,444,643
`4,491,509
`4,500,409
`4,564,435
`4,680,061
`
`4,714,536
`4,826,584
`
`12/1987 Freeman et al........................ 204/298.2
`5/1989 dos Santos
`Pereiro Ribeiro .......... ...... 204/298.09
`6/1989 Ramalingam et al............... 204/192.38
`4,839,011
`2/1990 Gaertner et al...................... 204/192.12
`4,904,362
`4,978,437 12/1990 Wirz ............................. ....... 204/192.23
`3/1992 Boozenny et al............. ...... 204/298.22
`5,096,562
`7/1992 Hurwitt et al................. ...... 204/192.12
`5,130,005
`5,171,415 12/1992 Miller et al.......................... 204/298.09
`1/1993 Hughes ........................ ....... 204/298.09
`5,180,478
`9/1993 Inoue ........................... ....... 204/192.12
`5,244,556
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 4 of 41
`U.S. Patent
`5,565,071
`65
`
`Oct. 15,1996
`
`Sheet 1 of 26
`
`tyia. 2 (PRIOR ART)
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 5 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996
`
`Sheet 2 of 26
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 6 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996
`
`Sheet 3 of 26
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 7 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996
`
`Sheet 4 of 26
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 8 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996
`
`Sheet 5 of 26
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 9 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15,1996
`
`Sheet 6 of 26
`
`92
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 10 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996
`
`Sheet 7 of 26
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 11 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996
`
`Sheet 8 of 26
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 12 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996
`
`Sheet 9 of 26
`
`^./7
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 13 of 41
`5,565,071
`U.S. Patent
`
`Sheet 10 of 26
`
`Oct 15, 1996
`
`175
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 14 of 41
`5,565,071
`U.S. Patent
`
`Sheet 11 of 26
`
`Oct. 15, 1996
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 15 of 41
`5,565,071
`U.S. Patent
`
`Oct. 15, 1996 Sheet 12 of 26
`
`J / /
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 16 of 41
`5,565,071
`U.S. Patent
`
`Sheet 13 of 26
`
`Oct. 15,1996
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 17 of 41
`5,565,071
`U.S. Patent
`
`Sheet 14 of 26
`
`Oct. 15,1996
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 18 of 41
`5,565,071
`U.S. Patent
`
`Sheet 15 of 26
`
`Oct. 15, 1996
`
`113
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 19 of 41
`5,565,071
`U.S. Patent
`
`Sheet 16 of 26
`
`Oct. 15, 1996
`
`SYSTEM
`
`^.32
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 20 of 41
`5,565,071
`U.S. Patent
`
`Sheet 17 of 26
`
`Oct. 15, 1996
`
`tylfy.33
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 21 of 41
`5,565,071
`U.S. Patent
`
`Sheet 18 of 26
`
`Oct. 15, 1996
`
`tyicf 34
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 22 of 41
`5,565,071
`U.S. Patent
`
`Sheet 19 of 26
`
`Oct. 15, 1996
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 23 of 41
`5,565,071
`U.S. Patent
`
`Sheet 20 of 26
`
`Oct. 15, 1996
`
`209
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 24 of 41
`5,565,071
`U.S. Patent
`
`Sheet 21 of 26
`
`Oct. 15, 1996
`
`209
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 25 of 41
`5,565,071
`U.S. Patent
`
`Sheet 22 of 26
`
`Oct. 15,1996
`
`163
`
`tyicj,. 38
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 26 of 41
`5,565,071
`U.S. Patent
`
`Sheet 23 of 26
`
`Oct. 15, 1996
`
`39
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 27 of 41
`5,565,071
`U.S. Patent
`
`Sheet 24 of 26
`
`Oct. 15, 1996
`
`233
`
`40
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 28 of 41
`5,565,071
`U.S. Patent
`
`Sheet 25 of 26
`
`Oct. 15, 1996
`
`241
`
`241
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 29 of 41
`5,565,071
`U.S. Patent
`
`Sheet 26 of 26
`
`Oct. 15, 1996
`
`43
`
`tylcj,. 44
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 30 of 41
`
`5,565,071
`
`1
`INTEGRATED SPUTTERING TARGET
`ASSEMBLY
`
`RELATED INVENTION
`This application is a divisional application of prior U.S. of
`application Ser. No. 08/236,715, filed Apr. 29, 1994, now
`U.S. Pat. No. 5,487,822, which is a continuation-in-part
`(CIP) of application Ser. No. 08/157,763, filed Nov. 24,
`1993, now U.S. Pat. No. 5,433,835 issued Jul. 18, 1995.
`
`FIELD OF THE INVENTION
`This invention relates to planar magnetron sputtering
`targets and more specifically to a structure and method for
`cooling the sputtering target and a structure and method for
`holding such a target being cooled.
`
`BACKGROUND OF THE INVENTION
`Sputtering describes a number of physical techniques
`commonly used in, for example, the semiconductor industry
`for the deposition of thin films of various metals such as
`aluminum, aluminum alloys, refractory metal silicides, gold,
`copper, titanium-tungsten, tungsten, molybdenum, tantalum
`and less commonly silicon dioxide and silicon on an item (a
`substrate), for example a wafer or glass plate being pro­
`cessed. In general, the techniques involve producing a gas
`plasma of ionized inert gas “particles” (atoms or molecules)
`by using an electrical field in an evacuated chamber. The
`ionized particles are then directed toward a “target” and
`collide with it. As a result of the collisions, free atoms or
`groups of ionized atoms of the target material are ejected
`from the surface of the target, essentially converting the
`target material to free atoms or molecules. Most of the free
`atoms which escape the target surface in the direction of the
`substrate, strike the substrate without intervening collision,
`and form (deposit) a thin film on the surface of the object
`(e.g. wafer, substrate) being processed, which is located a
`relatively short distance from the target.
`One common sputtering technique is magnetron sputter­
`ing. When processing wafers using magnetron sputtering, a
`magnetic field is used to concentrate sputtering action in the
`region of the magnetic field so that target sputtering occurs
`at a higher rate and at a lower process pressure. The target
`itself is electrically biased with respect to the wafer and
`chamber, and functions as a cathode. Objectives in engi­
`neering the cathode and its associated magnetic field source
`include uniform erosion of the target and uniform deposition
`of pure target material on the wafer being processed. During
`sputtering, if magnets generating a magnetic field are sta­
`tionary at a location, then continuous sputtering quickly
`consumes the sputtering target thickness at that location and
`generates hot spots at the locations of sputtering. Therefore,
`the magnets are usually continuously moved over the back
`of the target during its sputtering. Nonetheless, non-uniform
`wear patterns persist. To avoid contaminating the process,
`sputtering is stopped before the non-uniform sputtering wear
`pattern has consumed the full thickness of the target material
`at any point. If any point on the target plate behind the target
`were to be reached, sputtering of the target backing plate
`material (often copper) would occur, contaminating the
`vacuum chamber and the water being processed with the
`target backing material (e.g., copper). Because of the non-
`uniform pattern of target utilization, conventional practice is
`to stop the sputtering while a large percentage of the target
`still remains.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`As the target erodes, the distance between the target
`surface (which is eroding away) and the substrate being
`sputtered is slowly increasing. The change in the distance
`between the target surface and the substrate being sputtered
`creates a change in the qualities of the sputtered material
`deposited and its uniformity. When large areas such as glass
`plates are being deposited, variations in the thickness of
`deposited sputtered material are measurable and may be
`unacceptable if the change in the target thickness detrimen­
`tally affects the deposition of the target material on the
`substrate being deposited.
`Considerable energy is used in generating the gas plasma
`and creating ion streams impacting on the cathode. This
`energy must be dissipated to avoid melting or nearly melting
`the structures and components involved. Common tech­
`niques used for cooling sputtering targets are shown in
`FIGS. 1 and 2. One technique, as used in many prior art
`sputtering devices, passes water or other cooling liquid
`through a fixed internal passage of the sputtering target as
`shown in FIG. 1, a first cooling liquid passageway such as
`a hose 65 supplies water or other cooling liquid to a target
`backing plate 63 where it passes through cavities or passages
`of the backing plate and out a second hose 66. The target 64
`is thereby quickly cooled. To complete the picture of FIG. 1,
`the sputtering chamber 60 includes an object (substrate)
`support structure 62 on which rests the substrate to be
`deposited 61. In this configuration the sputtering target is
`completely immersed in the process environment. A water-
`to-vacuum seal is often needed to prevent the water or other
`cooling liquid from leaking out of its passages. A magnetron
`sputtering cathode as described by Carlos dos Santos Pereiro
`Ribeiro in his U.S. Pat. No. 4,826,584 is typical of the prior
`art showing cooling line attachments hidden behind the
`sputtering target and attached to the back of the target to pass
`liquid through structures adjacent to the target. While a
`magnet is not shown in FIG. 1, commonly these devices
`have stationary or rotating magnets to assist in directing the
`ion flow and controlling the primary sputtering location.
`Another technique which is commonly used which has
`eliminated the vacuum-to-water seal problem is shown in
`FIG. 2. A processing chamber 50 includes a sputtering table
`56 supporting a substrate 55 to be sputter coated in close
`proximity to a target 54. The sputtering chamber 50 includes
`a circumferential top flange on which a target assembly 52
`rests. The target assembly 52, consisting of a target backing
`plate 53 and the target 54, completely covers the flange of
`the processing chamber 50. A seal is made between the
`processing chamber 50 and ambient air outside the flange. A
`cooling chamber 51 encloses the top of the target assembly
`52. A stationary magnet or a moveable magnet 57 is located
`closely adjacent to the back of the target backing plate 53.
`A magnet sweep mechanism (not shown) causes the mov­
`able magnet 57 to move in a magnet sweep zone as shown
`by the dashed lines 58. The moveable magnet 57 and
`portions of the magnet sweep mechanism (not shown), in
`this configuration, are immersed in cooling liquid which
`generally fills the cooling chamber 51 and is circulated
`through the chamber behind the target to ensure cooling of
`the target.
`In these configurations the target backing plate 53 is
`subjected to a strong vacuum pressure on the processing side
`(less than 1 torr) with a positive pressure of as much as
`several atmospheres on the cooling side. The actual pressure
`on the cooling side depends on the weight of the coolant in
`the cooling chamber and on the static and dynamic pressures
`of the coolant in the cooling chamber as enough coolant to
`maintain acceptable temperatures on the sputtering target is
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 31 of 41
`
`5,565,071
`
`3
`moved through the system. To avoid short-circuiting the
`flow of coolant through the chamber (from the inlet imme­
`diately by the shortest path to the discharge), often distri­
`bution manifolds or flow directing restrictions are placed in
`the path of the coolant:to minimize short-circuiting and
`maximize cooling.
`To obtain maximum thermal conduction between the
`cooling liquid and the target backing plate, it is necessary
`that the flow regime in the cooling chamber 51 be such that
`any fluid boundary layer formed at and near the back of the
`target backing plate 53 be minimized or eliminated. There­
`fore, laminar cooling flow is not sufficient, the flow must be
`in the turbulent range to maximize heat transfer between the
`fluid target and the fluid. Higher fluid pressures are needed
`to generate the fluid velocities required for turbulent flow
`resulting in higher pressures in the cooling chamber 51.
`For small sputtering targets, the target backing plate and
`target can be built to be quite massive to resist deflections
`due to the differential pressures between the vacuum in the
`processing chamber 50 and the ambient air pressure plus
`fluid pressure in the cooling chamber 51. When the size of
`the target and target backing plate become large because the
`area to be coated is quite large, as might be done for a flat
`glass panel to be used in a flat panel display of a computer
`or television screen, the thickness of the target and target
`backing plate must be substantially increased to avoid
`unacceptable deflections. When a magnetron is used, sput­
`tering is most effective when the magnets are just behind the
`surface of the sputtering target. Increasing the distance
`between the surface of the sputtering target and any magnets
`used for magnetron sputtering behind the target (by increas­
`ing target thickness) substantially decreases the effect of the
`magnets on sputtering, or conversely, much more powerful
`magnets need to be used in order to be sure that the magnet
`field is effective through the thickness of the thicker target
`and its backing plate. The target assembly, in its present
`target size of 510 mmx620 mm, or 570x720, however, does
`not require the top chamber to be under vacuum for the
`system to operate properly because the deflecting loads due
`to vacuum from the process-side chamber are small and the
`coolant loads are all internal to the target assembly.
`The deflection of the target and target backing plate under
`the differential pressure between the processing chamber
`and the cooling chamber causes the target and target backing
`plate to bow substantially. Many targets are attached to their
`target backing plates using a relatively ineffective soldering
`or brazing technique. The bowing of the target backing plate
`and target creates an enormous stress in the solder or brazing
`material, or in the target material if it is softer, such that the
`probability of de-lamination or separation of the target from
`the target backing plate is greatly increased. In instances
`where solder or low temperature brazing has been used, a
`separation between the target and target backing plate at one
`point acts as a nucleus for a propagating defect. Once a
`pinhole surface defect forms, a hot spot develops progres­
`sively melting the solder and brazing compounds located
`there. When sufficient melting and/or separation has
`occurred, the target will actually drop off the target backing
`plate, ruining the process and requiting complete replace­
`ment of the target, if not a complete cleaning of the process
`chamber.
`Methods that have been used in the past to attempt to
`overcome these difficulties include high pressure— high
`temperature diffusion bonding, explosion bonding, friction
`welding, or roll bonding of the target to its backing plate. In
`these processes there is a large non-uniform thermal or
`mechanical gradient to which the target and target backing
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`4
`plate are subjected. The microstructure of the various pieces
`is affected by the stress induced by thermal gradients or
`mechanical deflections and the dimensions of the pieces
`change. Subsequent processing (machining and or thermal
`stress reduction techniques) must often be used to arrive at
`a target-target backing plate assembly that is dimensionally
`stable without warpage under the thermal cycling of sput­
`tering.
`The disadvantages of the existing sputtering target sys­
`tems as described above continue to inhibit the wide use of
`sputtering as an efficient and cost-effective means for apply­
`ing surface coatings.
`
`SUMMARY OF THE INVENTION
`This invention relates to an improved configuration for a
`sputtering target and sputtering target backing plate. This
`configuration overcomes many of the drawbacks of the
`previous configurations and provides a structure and method
`to improve sputtering coverage and sputter large areas such
`as glass plates. In particular, large targets are required when
`stationary, full coverage deposition is required with high
`film quality for large substrates.
`The new configuration includes a processing chamber
`having a top circumferential flange surface. A sputtering
`target assembly is supported on the flange. The target
`assembly includes a target separate or integral with a target
`backing plate. In a monolithic (integral) configuration the
`target (e.g. aluminum and its alloys) and target backing plate
`can be a single piece of material into which O-ring grooves
`and other fixtures are machined to seal with the process
`chamber. In other instances the target material is separate
`from the target backing plate and is secured to the target
`backing plate using one of several commonly known joining
`techniques such as soldering, welding, or brazing. Addi­
`tional techniques for joining the target to the target backing
`plate according to this invention include bonding the target
`to its backing plate by use of diffusion bonding, by filler­
`metal, solid state, or liquid phase diffusion bonds—all at
`comparatively low temperatures and pressures.
`A cooling cover plate is firmly attached (perhaps bonded)
`to the back (top) of the target backing plate. The cooling
`cover plate must be tightly joined with the back of the target
`backing plate so that a fluid fight seal is created for the
`cooling fluid. The cooling cover plate has cavities or grooves
`therein which provide a flow path (passages) for cooling
`fluid. The cooling fluid cavities or grooves are configured in
`such a way as to distribute the cooling liquid flow over a
`substantial area of the target backing plate so as to provide
`a maximum cooling or heating effect over the whole plate.
`The grooves are machined or east into the side of the cooling
`cover plate facing the target backing plate. The grooves or
`cavities have intermediate fins or walls. When the ends of
`these fins or groove walls are secured to the backing plate,
`they help maintain the dimensions of the cooling passages
`over the wide span of the cooling cover plate. In this way
`cooling fluid pressure in the cooling passages does not cause
`bowing of the cooling cover plate or the target and its target
`backing plate.
`The cooling cover plate can be joined to the target backing
`plate by any reliable means. However, it has been found that
`in order to reliably join the ends of the fins or intermediate
`walls of the cooling passage cavities or grooves to the target
`backing plate, it is sometimes necessary to provide a strong
`bond such as achieved by using a structural type adhesive,
`diffusion bonding, or brazing. It is important that the coef­
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 32 of 41
`
`5,565,071
`
`5
`ficient of thermal expansion of the target backing plate and
`its cover be closely matched. If not closely matched, then the
`shear stress associated with differential thermal expansion
`between the pieces causes bond failure. The differential
`strain between the target backing plate and a cooling cover
`plate of different materials can be minimized by using pins
`at intermediate locations across the field between the edges
`of the plates. Screws or bolts at intermediate locations can
`also establish and assure that de-bonding does not take
`place.
`When using a structural type adhesive such as a nitrile
`epoxy adhesive, the surfaces to be bonded are cleaned and
`treated (roughened) to improve the adherence of the nitrile
`epoxy. The adhesive is precisely located on its respective
`bonding surfaces by being attached to a carrying screen or
`mesh. In accordance with good work practices, the adhesive
`is placed on the mesh only at those locations corresponding
`to places between the cover plate and target backing plate
`where joining (bonding) is desired. The target backing plate
`and cooling cover plate are then pressed against each other
`with a predetermined pressure and heated to a predetermined
`temperature to assure the bonding of the pieces. Once the
`nitrile epoxy has set, a very strong bond is created between
`the cooling cover plate and the target backing plate such that
`differential pressures of several atmospheres can be applied
`without failure of the epoxy bond.
`The cooling cover plate can also be joined to the target
`backing plate using diffusion bonding techniques as dis­
`cussed below for bonding a separate target material to its
`backing plate.
`When the target and target backing plate are separate and
`need to be joined, there is always concern about the bond
`between the target and the target backing plate under the
`locally high temperatures of the process. Diffusion bonding,
`a technique often used in the aircraft industry to join and
`guarantee the bonding of critical parts, can be used to bond
`various target materials to various backing plates such that
`a failure of the bond in some areas will not cause propaga­
`tion of the de-lamination over the whole target as happens
`now with prior art soldering or brazing techniques. For
`sputtering it is sufficient that there initially be in excess of
`70% contact (bonding) between the target and the target
`backing plate to provide a satisfactory electrical and thermal
`connection between the two to adequately dissipate the
`thermal energy delivered to the target plate by the process.
`Diffusion bonding at comparatively low temperatures and
`pressures provides a gentle method of joining of the target
`to the target plate. Bonding by diffusion permits dimensional
`stability and bonding reliability while avoiding thermally or
`mechanically induced stresses due to localized gradients
`when high pressure—high temperature diffusion bonding,
`explosive bonding, friction welding, or roll bonding are
`performed. Also, diffusion bonding can be employed to bond
`the cooling cover plate to the backing plate at the same time
`that the target is being bonded to the target backing plate.
`Various diffusion recipes are identified to bond tantalum to
`titanium-based materials, titanium targets to titanium, and
`tantalum to aluminum (and its alloys).
`In some cases, preparation of a target assembly using
`diffusion bonding consists of diffusion bonding the target to
`the target backing plate. Once the target backing plate is
`bonded to the target then the target backing plate is bonded
`to the cooling cover plate using the structural epoxics.
`Simultaneous with this step, an insulating sheet of glass
`epoxy laminate (e.g., G-11/FR4) can be bonded over the
`cooling cover plate, or the laminate may be bonded over the
`cooling cover plate at a later time.
`
`5
`
`10
`
`15
`
`20
`
`25
`
`30
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`6
`In other cases, the cooling cover plate and insulating sheet
`of glass epoxy laminate are formed by a single cast operation
`using a composite prepreg product that is cast in place. Wax
`or other material with a low melting point can be formed into
`the shape (pattern) of the desired cooling flow passages on
`the back of the target backing plate. A fluid dam formed
`around the edge of the plate retains a casting material, such
`as prepreg—an ambient temperature castable structural
`epoxy that can be reinforced with various forms, tapes and
`fabrics (e.g., aramid fiber, glass, nylon, etc.) poured over the
`backing plate to form the cooling passages and insulate the
`target within the edges of the plate. Once the castable
`material sets, openings are made to the fluid passage and the
`assembly is heated to above the melting (or fluidizing)
`temperature of the pattern material so that the wax (or other
`pattern material) can be removed leaving cooling fluid
`passages in the shape of the pattern.
`Machining to final dimensions is done once final bonding
`is complete. Alternately, cooling water passages and grooves
`can also be provided in the target backing plate. The cooling
`cover plate is then a flat piece to bond over the cooling
`passages in the target backing plate. For reusable target
`assemblies, the target backing cover plate can seal the
`cooling channel using O-rings with removable fasteners
`spaced generally regularly across the target backing plate
`area to bond the cooling cover plate to the target backing
`plate. Or, a sheet of elastomeric material can be sandwiched
`between the backing plate and cover plate and squeezed with
`removable fasteners to act as a gasket to seal the cooling
`fluid passages.
`The target, target backing plate, and cooling cover plate
`make up a target assembly which is placed over the sput­
`tering chamber. When the target assembly is made in a
`configuration with a rigid cross section or reinforced to
`minimize bending, sputtering can take place while the target
`carries the load of the differential pressure between ambient
`conditions and the vacuum of the processing chamber.
`Alternatively, a top chamber can be put in position to
`enclose a magnet and be sealed to the top of the target
`assembly. When sputtering is desired, the pressures in both
`the sputtering chamber and the top chamber are reduced
`substantially and nearly equally. The target assembly then
`acts as a diaphragm separating the two chambers of nearly
`equal pressure. The cooling fluid flowing through the cool­
`ing passages in the target assembly is isolated from both of
`the vacuum chambers. The strong bond between the target
`backing plate and the ends of the fins of the cooling cover
`plate reduces, if not completely eliminates, the deflection of
`the target assembly and target due to cooling fluid pressures.
`A magnet sweeping mechanism placed in the dry top
`chamber does not need to overcome the resistance of fluid as
`it would if it were immersed in fluid. Further, since the target
`assembly is acting as a diaphragm sealing two chambers of
`nearly identical pressure, the target assembly can be made
`very thin to decrease the distance between the magnets and
`the target face.
`Many types of high-intensity magnets reduce their mag­
`netic field strength at elevated temperatures. Using a con­
`figuration according to this invention, unlike previous con­
`figurations where the magnets are immersed in the hot
`cooling fluid, the magnets’ temperature increases very little,
`if at all, due to the sputtering process. The magnets are
`located in the top evacuated chamber and there is virtually
`no conductive heat flow to the magnets and radiative heat
`flow from the target assembly to the magnets will be quite
`minuscule as the cooling cover plate face of the target
`
`

`

`Case 6:20-cv-00636-ADA Document 48-11 Filed 02/16/21 Page 33 of 41
`
`5,565,071
`
`7
`assembly will have a maximum temperature substantially
`identical with that of the average cooling fluid temperature,
`e.g. 50° C. At such temperatures, radiative heat transfer is
`negligible. In addition, because the target assembly is elec­
`trically biased, an electrical insulating sheet is often placed
`over and bonded to the backside of the cooling cover plate.
`This sheet acts as a barrier and further reduces any heat
`transfer from the target assembly to the magnets.
`The electrically charged target ass