Magnetron sputtering equipment

Abstract: The movable magnet track housing (110) of a magnetron sputtering apparatus is provided with a cooling channel (136) and a plurality of nozzels (135) for cooling the backing plate (20) of the magnetron sputtering target (10). A cooling liquid (40) is delivered to the cooling channel, which distributes the pressure of the liquid to its nozzles. Fluid dispensed from the nozzles is directed at a given area on the target backing plate to make cooling more efficient.

Description: The present invention relates to a planar magnetron sputtering apparatus, a coolable sputtering target plate assembly, a magnet housing unit and a method of cooling a target plate for use in planar magnetron sputtering equipment. One common sputtering technique is magnetron sputtering. When processing wafers using magnetron sputtering, a magnetic field is used to concentrate sputtering action in the region of the magnetic field so that 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. Techniques of this kind are disclosed in EP-A-0 213 922, EP-A-0 300 995 and DE-A-3636 524. Conventional cooling methods in prior art sputtering devices employ a cavity behind or internal to a plate being heated by sputtering; see, e.g., the patents to Lamont, Jr., Rainey, Garrett, and Freeman mentioned above, as well as U.S. Patents 3,956,093 issued on 5/11/76 to McLeod; 4,116,806 issued on 9/26/78 to Love et al.; and 4,175,030 issued on 11/20/79 to Love et al. In these patents, water or other cooling liquid is provided through an opening to fixed internal passages of the device or a cavity of the device. A separate opening allows the water to be discharged from the device. The devices having fixed internal passages route the cooling water through these passages, which are adjacent to the heat generated elements of the device, to cool them. In the devices where the water is routed to a cavity, the direction of the flow of water as well as the movement of a mechanism inside the cavity contribute to the agitation of the cooling liquid as it cools the heat generating elements before the cooling liquid exits the cavity. These prior art methods for cooling devices having internal cavities for cooling sometimes create large and often random differences in actual water flow and in the temperature of a heat generated target plate from one side to the other and across the plate. The water cavity is pressurized as coolant flows. Pressurizing the water cavity in contact with the target plate requires that it be strengthened, because the pressure within the water chamber when added to the vacuum pressure in the evacuated sputtering cavity provides a large differential pressure across the target plate. The target plate must be sized to support this large differential pressure. While cooling has also been proposed by drilling gun bore type channels in the target backing plate similar to the fixed cooling passages in the prior art, the location of these channels necessarily causes localized hot spots between the channels and in the prior art temperature increases away from the location of cooling liquid flow. Also, drilling, locating, and connecting cooling liquid piping to these channels unnecessarily complicates the construction of the target backing plate. The distance between the magnets and the surface of the target affects the degree to which sputtering is concentrated by the magnet's magnetic field. For a given magnet design, a short distance causes sputtering to be more highly concentrated than a greater distance. The highest sputtering concentration occurs if a target having a negligible thickness is mounted directly on the magnets. Every additional increment of distance between the surface of the target and the magnets reduces the influence of the magnetic field on sputtering of the target. A thick target backing plate is necessary in a pressurized water chamber device to attain the additional strength needed to support the pressure behind the target backing plate, and is also necessary in a device using a target backing plate which has been drilled for cooling and therefore requires additional thickness to retain its nominal strength. Unfortunately, the use of a thick target backing plate, which together with the target forms a target plate assembly, adds extra thickness to the target plate assembly. To avoid a change in magnetic flux at the target's surface, a thin target must be substituted to maintain the same distance between the magnets and the target's surface. Alternately, a reduced magnetic flux at the target surface, as a result of increased distance (thickness) between the magnets and the surface of the target, must be accepted. Therefore, the need to increase the thickness of the target backing plate to provide more strength is in conflict with the desire to reduce the distance between the surface of the target and the magnets to concentrate the location of sputtering. Effective cooling of a magnetron sputtering apparatus is achieved in the present invention without the need for a target backing plate having sufficient thickness to resist the pressure of a pressurized water cavity or to accommodate internal bore-type channels. According to one aspect of the invention, there is provided a planar magnetron sputtering apparatus comprising: a cooling chamber; a thermally conductive target plate having a front side and a back side, the front side of the target plate being adapted to receive a sputter target and the back side of the target plate forming a portion of a wall of said cooling chamber; a magnet assembly mounted in said cooling chamber for sweeping a surface of a body across the back side of the target plate in co-ordination with the magnet assembly, the surface being opposite the back side of said target plate and maintained parallel to and in proximity to the back side of the plate and comprising ports for introducing cooling liquid from the body directly into a volume between the surface and the back side of the target plate; and a cooling chamber drain. According to another aspect of the invention there is provided a coolable sputtering target plate assembly comprising: a cooling chamber; a target plate having a front side for receiving a sputtering target and a back side forming a portion of a wall of the cooling chamber; a rotatable drive shaft having a hollow portion; inlet means for rotatably supporting the drive shaft and for routing and sealing a cooling liquid flowing from an inlet connection to the hollow portion of the drive shaft; outlet means for routing the cooling liquid from the hollow portion of the drive shaft, the outlet means being operatively supported from the drive shaft; and a housing operatively coupled to the drive shaft for sweeping a planar surface thereof across the back side of the target plate, the housing comprising a cooling channel coupled to the outlet means for receiving the pressurised cooling fluid from the hollow portion of the drive shaft, the housing having disposed therein ports for directing a stream of cooling fluid from the channel to impinge on the back side of the target plate. According to yet another aspect of the invention there is provided a magnet housing unit for sweeping behind the target support plate of a planar magnetron sputtering apparatus, comprising: a supporting body having a surface thereof adapted for sweeping behind the target support plate; a magnet track disposed in the supporting body; a fluid line disposed in the support body for receiving pressurised cooling fluid; a fluid channel provided in the supporting body, the fluid channel being connected to the fluid line; and a plurality of ports from the channel to the supporting body sweeping surface. According to a further aspect of the invention, there is provided a method of cooling a target plate in a planar magnetron sputtering apparatus comprising a magnet assembly movable in a cooling chamber, wherein the target plate is thermally conductive and has a front side and a back side, the front side of the target plate being adapted to receiving a sputter target and the back side of the target plate forming a portion of a wall of the cooling chamber contains cooling liquid and the magnet assembly is swept across the back side of the target plate, the method comprising the steps of: sweeping a surface of a body across the back side of the target plate in coordination with the magnet assembly, the surface being opposite the back side of the target plate and maintained parallel to and in proximity with the back side of the target plate; discharging cooling liquid from the body directly into a volume between the surface and the back side of the target plate; and draining cooling liquid from the cooling chamber. The invention is further described below, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a cross sectional view of a magnetron sputtering apparatus in accordance with an embodiment of the present invention, Figure 2 shows an end view of a radial slide of Figure 1, Figure 3 shows a partial bottom view of Figure 2 with the top of the radial slide 151 offset from its bottom 159, Figure 4 shows an internal cross sectional view of Figure 1 taken at section 4 - 4 with the outline of an external gear 185 and an internal gear 45 superimposed, Figure 5 shows a magnet housing body including a magnet track and a cooling channel with nozzles, Figure 6 is a close-up view of the back of the magnet housing around its water inlet connection, Figure 7 is a cross section of the magnet housing taken at 10-10 in Figure 6, and Figure 8 is a cross section of the magnet housing taken at 11-11 in Figure 6. In the plan of magnetron sputtering apparatus of Figure 1, a sputtering target 10 is mounted on a front side 21 of a target backing plate 20 having a rotating mechanism 100 mounted within a water chamber 30 on a backside 22 of the target backing plate 20. The rotating mechanism 100 has a magnet housing assembly 110 containing magnets 121, . . ., 125 in a magnet track channel 130. The magnet housing assembly 110, which is eccentrically mounted on the rotating mechanism 100, is rotated by the rotating mechanism 100 about a common central axis 35 of the target 10 and water chamber 30. As the magnet housing assembly 110 is rotated by the rotating mechanism 100, it has an outer edge which is also radially oscillated between an extreme outer position closest to the perimeter and an extreme inner position farthest from the perimeter. This oscillating motion on the backside 22 of the sputtering target 10 is accomplished by using a radial slide assembly 150 mounted to a block 144 at a bottom end 145 of a rotatable drive shaft 140. The radial slide assembly 150 supports the magnet housing assembly 110 which at its outer edge is oscillated between its extreme inner position 256a and its extreme outer position 255a by a connecting rod 160. The connecting rod 160 transmits a force which oscillates the magnet housing assembly 110 when the rotating mechanism 100 is rotated. Thermal energy must be dissipated to prevent the target 10 from overheating. In this embodiment, the thermal energy is dissipated by the injection of a cooled liquid (i.e. water or glycol) 40 which is routed directly to the back surface 22 of the conducting target backing plate 20 and generally adjacent to the magnets 121, . . . , 125 in the magnet housing assembly 110. Figure 1 shows a partial cross section of about one-half of the central axis 35 of the water chamber 30 while showing a complete cross section of the rotating mechanism 100. The device as shown is generally mounted on top of a magnetron sputtering chamber (not shown). This magnetic sputtering chamber has a magnetic sputtering chamber flange appropriate for mating with the bottom insulating ring 50. The magnetic sputtering chamber flange also has an O-ring containing sealing channel, as does the bottom insulating ring 50. A dark space ring 51 is press fit mounted inside the diameter of the bottom insulating ring 50 such that when the target backing plate 20, with the target 10 bonded to it, is placed with the target 10 facing the evacuated sputtering chamber, a small gap 52 of 3 - 6 mm or less exists between the edge of the target 10, which is circular in shape, and the inside edge of the dark space ring 51. A dark space 53 is formed behind the dark space ring 51 between the edge of the target 10 and the inside of the bottom insulating ring 50. The bottom insulating ring 50 is made of an insulating material, such as nylon, which insulates the target backing plate 20 from the magnetic sputtering chamber housing (not shown). A top insulating ring 54 is provided on top of the target backing plate 20 to insulate it from the water chamber 30. The top insulating ring 54 is provided with an O-ring containing channel 55 facing the target backing plate 20 and with flanged shoulders 56, 57 to locate the top insulating ring 54 on the target backing plate 20 and to positively locate the water chamber 30 on the top insulating ring 54. The water chamber 30 has a bottom flange 32 which mates with the top insulating ring 54. This bottom flange 32 also has an O-ring containing channel 33 which seals its mating surface with the top insulating ring 54. The bottom insulating ring 50, the target backing plate 20, the top insulating ring 54, and the bottom flange 32 of the water chamber 30 adjacent to the top insulating ring 54 all have bolt holes 99 for passing a bolt or a stud (not shown) through them such that once the bolt or stud is tightly fastened, these pieces are held tightly together. Insulating the target backing plate 20 from its adjacent parts allows it to act as a cathode, in concert with an anode (not shown), creates the electric field necessary for a plasma to form and magnetron sputtering to take place. A power level of approximately 30 kW is provided to the target backing plate 20. To prevent current leakage, bolt insulators 95, 96 are provided to line the flange hole 98 of the target backing plate 20 and the bolt hole of the water chamber flange 32, respectively, so that a bolt or stud (not shown) holding the flange set together does not conduct or easily leak electricity from the target backing plate 20 to either the evacuated sputtering housing (not shown) or the water chamber 30. The water chamber 30, in this embodiment, is a short hollow aluminum cylinder. It is supported by the top insulating ring 54 to form a vertical cylinder within which the rotating mechanism 100 operates. The water chamber 30 has two flanges: a lower flange 32 and an upper flange 36. The lower flange 32 connects to the magnetic sputtering housing and is supported by it through a flange set containing the target backing plate 20. The upper flange 36 of the water chamber 30 has an inner landed shoulder 37 which contains a threaded bolt hole pattern 38. The face of the top flange 36 has an O-ring containing groove 39 for sealing the top flange 36 against a water chamber cover 41. The threaded bolt hole pattern 38 in the landed shoulder 37 of the upper flange 36 of the water chamber 30 mates with an internal gear 45 mounted to the lower land 37. This internal gear 45 is attached to the inner landed shoulder 37 of the upper flange 36 of the water chamber 30 and provides 348 gear teeth extending towards the center of the water chamber 30 having a 368 mm (14.5 inch) pitch diameter with a diametral pitch of 24. The water chamber cover 41 is supported by the face of the top flange 36 of the water chamber 30 and is sealed by O-rings in the O-ring channel 39 of the upper flange 36 of the water chamber 30. A bolt hole pattern matching the hole pattern of the upper flange 36 of the water chamber 30 is provided in the water chamber cover 41 so that these pieces can be water tightly mated. The water chamber cover 41 is circular and completely covers the top of the water chamber 30. It is made of a rigid non-corroding material such as aluminum. The water chamber cover 41 has a water outlet opening 42 which provides the outlet for cooling liquid 40, which is directed by the magnetic housing 110 onto the target backing plate 20 to cool the target backing plate 20 during sputtering. This water outlet opening 42 provides nearly no back pressure to the cooling liquid 40 contained in the water chamber 30 as the cooling liquid 40 merely needs to rise in the water chamber 30 to attain the level of the water outlet connection in the water chamber 30 and provide enough pressure to drive the cooling liquid 40 out the water outlet opening 42 and through the attached fitting 31 and tubing 43 to its destination. The water chamber cover 41 has at its center a hole 44 having a bolt hole pattern around it. This central hole 44 supports a rotating support/seal block 60 having a flange 61 which mates with the central hole 44 in the water chamber cover 41. The rotating support/seal block flange 61 has an O-ring containing channel 64 facing the water chamber cover 41 and a hole pattern which matches the bolt hole pattern in the water chamber cover 41 such that bolts placed in these threaded holes will liquid tightly hold the rotating support/seal block 60 to the water chamber cover 41. The inside part of the flange of the rotating support/seal block 60 has a shoulder 62 which mates with the outside diameter of the center hole of the water chamber cover 41 such that a tight fit is provided which prevents any lateral motion and provides a second means to locate the rotating support/seal block 60 in the water chamber cover 41. The rotating support/seal block 60 has a hole 65 through its central axis which is also the vertical central axis 35 of the water chamber 30 and the target backing plate 20. This central axis of the rotating support/seal block 60 is designed to support and seal the rotating drive shaft 140. The support/seal block 60 acts as a rotating coupling which is part of the internal passage of cooling liquid 40 being routed into the water chamber 30. The rotating support/seal block 60 has an inlet opening 63 providing a threaded opening to connect feed tubing 66 to the central hole 65 in the rotating support/seal block 60. The drive shaft 140 is provided through the rotating support/seal block 60. The drive shaft 140 is hollow from one end to the other. A welded plug 142 is welded inside the top end 143 of drive shaft 140, closing the shaft opening to the top and an end block 144 is provided on the shaft 140 at its bottom end 145. The drive shaft end block 144 supports a portion of the rotating mechanism and provides a fluid outlet opening from the drive shaft's hollow central fluid passage. The hole 65 in the center of the rotating support/seal block 60 consists of several sections: two bearing sections 67a and 67b, two sealing sections 68a and 68b, and a water section 69. The two end bearing sections 67a, 67b hold respective bearing races 71a and 71b such that respective roller bearings 70a and 70b mounted on the drive shaft 140 roll in these races 71a, 71b and provide the rotating support between the stationary rotating support/seal block 60 and the rotating drive shaft 140. The roller bearings 70a, 70b are held in contact with their respective races 71a, 71b by, respectively, spacers 220 and collars 225 with spring washers 230, only one set (several of which might be installed) being shown in Figure 1, or other suitable means which connect to the drive shaft 140. These collars and spring washers locate the bearings 70a, 70b on the drive shaft 140 and hold the drive shaft 140 in a predetermined relationship with the rotating support/seal block 60. The two sealing sections 68a, 68b of the rotating support/seal block 60 are located inboard from the bearing sections 67a, 67b. Each of the sealing sections 68a, 68b comprises a seal containing channel 72 along with a seal containing washer 73. A circular ring seal 74 constructed of resilient material (i.e., Buna-N rubber (Trade mark)) having a U-shaped cross section is provided around the shaft 140 in the seal containing channel 72. The opening at the top of the "U" in the U-shaped seal cross section in each seal faces towards the center of the rotating support/seal block 60. The sealing washer 73 is disposed between the seal 74 and its external adjoining bearing 70a, 70b such that the washer forms the bottom side of a three-sided box against which the U-shaped seal 74 rests. The inside of the U-shape is pressurized by fluid pressure emanating from the water section 69 of the rotating support/seal block 60. The water section 69 is at the center of the support/seal block 61 between the two sealing sections 68a, 68b. When liquid pressure is provided to the water section 69 of the rotating support/seal block 60, the sides of the U-seal 74 expand, against the rotating support/seal block 60 on one side and the drive shaft 140 on the other side, to seal the opening between the drive shaft 140 and the rotating support/seal block 60. The water section 69 at the center of the rotating support/seal block 60 is of a larger diameter than the outside of the drive shaft 140. The inlet opening 63 to the water section of the rotating support/seal block 60 provides a passage for cooling liquid 40 to pass from the inlet tubing 66 into the water section 69 of the rotating support/seal block 60. The drive shaft 140 being hollow and plugged at one end 143 and having an end block 144 at its other end 145 also has cross drilled holes 146 (drilled through from one side to the other at 90°) in five locations within the water section 69 of the rotating support/seal block 60, as located when assembled. As the drive shaft 140 is positioned, supported, and sealed within the rotating support/seal block 60, water passing into the water section 69 passes through the cross drilled holes 146 of the drive shaft 140 and into the hollow center of the drive shaft 140. The drive shaft 140 is disposed along the center line 35 of the water chamber 30 and extends from a point above the rotating support/seal block 60, where the drive shaft 140 is connected to a coupling 149 which is connected to a motor or gear motor (not shown), to a point within the water chamber 30 where the end block 144 of the drive shaft 140 is connected to a radial slide assembly 150. The drive shaft 140 is rotatably held at this location by the roller bearings 70a, 70b. Connected to the side of the drive shaft 140 in between the rotating support/seal block 60 and the end block 144 of the drive shaft 140 is a drive shaft arm 170. This arm 170 is clamped or otherwise firmly connected to the drive shaft 140 at a fixed predetermined location such that the arm 170 rotates with the drive shaft 140, when the drive shaft 140 is rotated. The bottom end block 144 of the drive shaft 140 is firmly connected to a radial slide top 151 of the radial slide assembly 150. The radial assembly slide 150 (Figures 1, 2, & 3) includes two rectangular pieces of rigid material, the slide top 151 and a slide bottom 159, preferably made of strong lightweight material such as aluminum, in a closely spaced relationship as shown in Figure 2. The radial slide top 151 has one side whose longitudinal central axis 154 is cut with a slot 152 along the full length of the piece. The slot 152 has a dovetail shaped section for most of its length while a rectangular section 153 of the slot closest to a hole 111 in the center of the magnet housing assembly 110 is rectangularly shaped and wider than the dovetail section of slot 152. The rectangular section 153 provides clearance for movement of a head of a shoulder bolt 180, which is threaded into the hole 111 of the magnet housing assembly 110, as the bolt 180 moves with the center 120 of the magnet housing assembly 110 into the outline of the radial slide top 151. The shoulder of the shoulder bolt 180 acts as a bearing journal for a connecting rod bearing 161 which rotatably connects and moves the magnet housing assembly 110 along the central axis 154 of the slot 152 as the connecting rod 160 transmits a motive force. A radial slide dovetail protrusion 157, made of delrin, nylon or other material having a high lubricity, is attached by countersunk screws such as 158 to the radial slide bottom 159. The radial slide dovetail protrusion 157 when inserted in the radial slide top dovetail slot 152 causes the radial slide bottom 159 to easily slide linearly along the central axis 154 longitudinal to the dovetail slot 152 (Figures 2 and 3). The radial slide top 151 is connected to the drive shaft 140 in a predetermined offset relationship wherein the rectangularly relieved end 153 of the radial slide top 151 is attached to the drive shaft bottom end block 144 so that the other end of the radial slide top 151 overhangs the block 144 (Figure 1). The radial slide bottom 159 is connected to the magnet housing assembly 110. The magnet housing assembly 110 includes a magnet housing body 116 having a magnet track channel 130 and a cooling channel 136 formed therein with a magnet housing cover 115 enclosing both the magnet track channel 130 and the cooling channel 136 (Figures 1 and 5). The magnet housing assembly 110 is circular and has the threaded hole 111 at its center. The magnet housing body 116 is annularly shaped having an opening at its center. The magnet track channel 130 and the cooling channel 136 are formed in the top side of the annular shaped magnet housing body 116 around its central opening. The magnet track channel 130 has a uniform regular rectangular shape at any given cross section perpendicular to the centerline of the channel; the shape formed by the magnet track channel is discussed below. Specially cut magnet segments 121, . . ., 125 conforming closely to each other and the walls of the magnet track channel are placed in the magnet track channel 130 (Figure 5). The cooling channel 136 in the magnet housing body 116 forms an annular ring having a uniformly rectangularly shaped cross section at any point perpendicular to the centerline of the channel. The outside diameter of the ring is less than the inside dimension of any part of the magnet track channel 130. A series of angularly disposed holes (nozzles) 135 (including nozzles 135a,b,x,y) connect a bottom surface 117 of the magnet housing body 116, facing the backside 22 of the target backing plate 20, and the inside of the cooling channel 136. These are called orifice water outlets 135. The magnet housing cover 115 also covers and seals the cooling channel 136. Various O-ring containing channels such as 118 (others shown but not numbered to preserve clarity) are provided on both sides of the cooling channel 136 in the magnet housing body 116 and on the extreme outside of the magnet track channel 130 so that when the magnet housing cover 115 is firmly attached to the magnet housing body 116 by bolts or some other reliable and easily-detachable means, the magnet track channel 130 is sealed, preventing leakage into the magnet track channel 130. The cooling channel is sealed to assure that flow of all cooling liquid is out through the nozzles 135 and not through some other undesired path. While the magnet housing body 116 is open at its center (annularly shaped), the magnet housing cover 115 is provided with the threaded hole 111 at its center, which corresponds to the center of the magnet housing assembly 110. Around the threaded hole 111 and the inside of the annular portion of the magnet housing body 116 a series of openings 119a,b,c,d are provided to allow fluid flow through the center of the magnet housing assembly 110. These openings 119a,b,c,d are sized so as not to adversely impact the structural integrity of portions of the magnet housing cover 115 connecting its outer annular portion to the threaded bolt hole 111 at its center (Figure 4). In Figure 1 holes 119a and 119c are shown to illustrate their location with respect to other pieces, even though the holes 119a and 119c are offset 45° from this location, as can be seen in Figures 4 and 6. A water connecting hole 113 is provided on back of the magnet housing cover 115 to accommodate an inlet water fitting 112 (Figures 1,4,6, and 8). The location of this inlet water connection 112 on the magnet housing cover 115 matches the location of the cooling channel 136 in the magnet housing body 116 in such a way that when cooling liquid 40 passes through the inlet water fitting 112 and water connection hole 113, it goes directly into the cooling channel 136. The bottom end block 144 of the drive shaft 140 has a closed fluid passage from the center of the hollow drive shaft 140 to a shaft outlet water connection 147. A length of tubing 148 is provided connecting between the shaft outlet water connection 147 and the magnet housing inlet water fitting 112 such that a cooling liquid 40 flowing out of the bottom end 145 of the drive shaft 140 will flow into the cooling channel 136 of the magnet housing body 116 by flowing through the tubing 148. The cooling channel 136 also contains a diffusion ring 137 which divides the cooling channel 136 into a cooling channel top portion 138 and a cooling channel bottom portion 139. The diffusion ring 137 provides a means for diffusing the pressure of the cooling liquid 40 injected at one (or more) location in the cooling channel top portion 138 so that pressure is equalized as the cooling liquid flows around the edges of the diffusion ring to the cooling channel bottom portion 139 and exits a plurality of orifice water outlets 135 (Figures 1, & 6-8). This diffusion ring 137 is supported by a fixed means 133 from the magnet housing cover 115 and provides one or more orifice openings (holes, slots 134a, 134b, or a combination) internally or in a spaced relationship with the wall of cooling channel 136 to assist in equally distributing the pressure on the cooling channel top portion 138 to the cooling channel bottom portion 139. In this way, a nearly uniform pressure is assured at the inlet side of each of the orifice water outlets 135 (in one embodiment there are 36 outlets). The outlets 135 are spaced a predetermined distance apart in a circular pattern in the magnet housing body 116. The nearly uniform pressure distributed around the cooling channel bottom portion 139 provides nearly uniform cooling liquid flow out each of the nozzles 135. The shoulder of the shoulder bolt 180 connected and retained in the hole 111 of the magnet housing cover 115 acts as a journal for the connecting rod bearing 161 which is a ball bearing. The bearing 161 operatively connects one end of the connecting rod 160 to a point (e.g. the central axis 120) on the magnet housing assembly 110 at which the journal is located so that the force can be transmitted. A gear shaft 175 is generally parallel to but spaced a predetermined distance from the central axis 35 of the drive shaft 140 within the water chamber 30. The drive shaft arm 170 which is clamped to (or otherwise firmly fixed to) and rotates with the drive shaft 140, provides support for the gear shaft 175. The gear shaft 175 is supported by gear shaft bearings 176a and 176b mounted on the drive shaft arm 170 close to its end. The gear shaft 175 is supported by the drive shaft arm 170 in such a manner that teeth of an external gear 185 mounted at a top end of the gear shaft 175 mesh with the teeth of the internal gear 45 mounted inside and at the top end of the water chamber 30. When the drive shaft 140 is rotated also rotating the drive shaft arm 170, the teeth of the external gear 185 continue their meshing relationship with the internal gear 45 and thereby rotate the gear shaft 175. The bottom end of the gear shaft 175 beyond the bottom of the drive shaft arm 170 has one end of a gear shaft crank arm 177 clamped (or otherwise fixedly attached) to it. One end of a drive pin 190 is clamped (or otherwise fixedly attached) to the other end of the gear shaft crank arm 177. The drive pin 190 is located a fixed distance away from the gear shaft 175 and generally parallel to it. As the gear shaft 175 rotates, when the drive shaft 140 is turned, the gear shaft crank arm 177 turns about the central axis of the gear shaft 175 which causes the drive pin 190 to move with the gear shaft 175 and describe a circular path around the gear shaft 175 with respect to the gear shaft 175. The other end of the drive pin 190 acts as a journal for the center of a second connecting rod bearing 163, a ball bearing, which is connected to one end of the connecting rod 160. The other end of the connecting rod 160 is connected to the shoulder bolt 180 at the center of the magnet housing assembly 110, as described above. As the drive shaft 140 is rotated, the gear shaft 175 rotates the drive pin 190 about the gear shaft 175, and the connecting rod 160 is thereby moved by the drive pin 190 and causes the magnet housing assembly 110 to slide back and forth along the longitudinal axis 154 of the dovetail slot 152 in the radial slide assembly 150. The shaft spacer (collar) 225 and the spring washer (spring collar) 230, along with other devices as necessary typically are provided along the drive shaft 140 to hold the drive shaft bearings 70 in a predetermined relationship with the drive shaft 140 and to hold the gear shaft crank arm 177 in a predetermined aligned relationship with its rotating support/seal block 60. The gear shaft bearings 176a, 176b and gear shaft 175 are also held in a fixed relationship with the drive shaft arm 170, the water chamber 30, and internal gear 45 by spacers (not shown). The spacers are located on the gear shaft 175 between the attachment (by clamping or other method of fixedly connecting) of the external gear 185 to the top end of the gear shaft 175 and attachment of the gear shaft crank arm 177 at the bottom end of the gear shaft 175. These spacers assist in holding the gear shaft bearings 176a, 176b fixed to the drive shaft arm 170 in a predetermined relationship. Spacers, washers, and other devices (not shown) are used as required to keep the various pieces in their prescribed relationship. The drive shaft 140 is connected through the coupling 149 to a motor or gear motor (not shown) which rotates the drive shaft 140. Motion is imparted to the magnet housing assembly 110 as follows. As the drive shaft 140 rotates in the rotating support/seal block 60, the drive shaft arm 170 and the drive shaft lower end block 144 also rotate. This rotation causes the rotating mechanism 100 (the radial slide assembly 150, the magnet housing assembly 110, the external gear 185, the gear shaft 175, and all pieces directly connected to those pieces) to rotate about the central axis 35 of the drive shaft 140. As the rotating mechanism 100 rotates, the teeth of the external gear 185 mesh with the teeth of the internal gear 45 causing the external gear 185 and the gear shaft 175 to rotate about the gear shaft's axis as the drive shaft 140 rotates about the central axis. As the gear shaft 175 rotates about its axis, the gear shaft crank arm 177 clamped to the bottom end of the gear shaft 175 also rotates causing the drive pin 190, which is clamped to the other end of the gear shaft crank arm 177, to rotate about the gear shaft axis as the gear shaft 175 rotates. As the drive pin 190 moves in a circular path about the gear shaft axis, the drive pin 190 together with the gear shaft crank arm 177 act as a crank shaft to force the end of the connecting rod 160, mounted to the end of the drive pin 190, by a ball bearing, to move with the pin 190 as it rotates. Since the gear shaft 175 is held in a fixed relationship with (clamped to) the drive shaft 140, to which is mounted the radial slide top 151, the movement of one end of the connecting rod 160, with the rotating pin 190, moves the other end of the connecting rod 160 connected to the center of the magnet housing assembly 110 fixed to the radial slide 150 and causes the radial slide bottom 159 to oscillate along the central axis 154 of the radial slide 150 in conjunction with the motion of the drive pin 190. The radial slide bottom 159 is fixed to the magnet housing assembly 110 which therefore also oscillates. The magnet housing assembly 110 therefore oscillates as the drive shaft 140 is turned. The radial slide assembly 150 connected to the end of the drive shaft 140 prevents the magnet housing assembly 110 from moving in a vertical direction, as seen in Fig. 1. The motion of the magnet housing assembly 110 is limited to a direction parallel to the longitudinal direction 154 of the dovetail slot 152 in the radial slide 150. Figures 2 and 3 show end and bottom views of the radial slide 150 which hold the magnet housing assembly 110 aligned with the central axis 154 of the dovetail slot 152. A rectangular section 153 of the end of the radial slide top 151 is relieved to allow the shoulder bolt 180 to move into the end of the radial slide top 151, and avoid interfering with it, as the magnet housing assembly 110 moves into the radial slide 150 at a point in the oscillation where the magnet housing assembly 110 moves closest to the central axis 35 of the water chamber 30 as the radial slide bottom 159 is moved by the connecting rod 160. Figure 4 shows the magnet housing assembly 110 within the water chamber 30 as viewed from above, cut at a cross section 4 - 4 in Figure 1, but with the external gear 185 and internal gear 45 superimposed. The gear shaft crank arm 177 is shown 90° to a vertical (as seen in Figure 4) centerline of the water chamber 30. It shows the connecting rod 160 connecting the drive pin 190 with the shoulder bolt 180 at the center of the magnet housing assembly 110. The radial slide bottom 159 is at approximately one-half of its travel between its innermost and outermost positions. The bottom piece 144 of the drive shaft 140 is also shown. The water connection 147 on the end block 144 of the drive shaft 140 is shown connecting by the tubing 148 (partially shown in two places) to the magnet housing inlet water fitting 112. As the drive shaft 140 rotates, the water connection 147 of the drive shaft end block 144 also rotates as does the magnet housing assembly 110 and the tubing 148. The flexible tubing 148 accommodates a linearly oscillating motion as the magnet housing assembly 110 moves toward and away from the center 35 of the water chamber 30 as it is rotated by the drive shaft 140. The external gear 185 and the internal gear 45 are shown superimposed on cross section 4 - 4, as described above. The external gear 185 rolls on the internal gear 45 which is mounted on a landed shoulder of a top flange of the inside perimeter of the water chamber 30. As the external gear 185 rotates, it causes the gear shaft crank arm 177 to rotate with it causing the drive pin 190 to drive the connecting rod 160 and the shoulder bolt 180 connected into the magnet housing assembly 110 to move the magnet housing assembly 110 in an oscillatory motion along the central axis 154 of the dovetail slot 152 in the radial slide assembly 150. Figure 5 shows the magnet track channel 130 in the magnet housing body 116 of the magnet housing assembly 110. The magnet track channel 130 is a flattened teardrop shape, which is moved in a combination radially oscillating and circularly rotating motion nearly completely covering the back of the target backing plate 20. A magnet housing axis 154 as shown directly corresponds to the radial slide central axis 154, and as the magnet assembly rotates in the water chamber 30 this centerline becomes parallel with each of the radial axes, i.e., 155, 156 a,b,c,d, as the magnet housing rotates around the center. The geometric relationship between the cooling channel 136, the nozzles 135, and the magnet track 130 is also pictured. The cross section of the magnet housing body 116 is shown as part of Figure 1 cut at section 1a-1a. The bottom of the housing as shown in Figure 5 is the point on the housing 110 which is always closest to the water chamber lower inner wall 34. In the embodiment described above, the drive shaft 140 is turned at a speed of 20 to 60 rpm. The internal gear 45 has 348 teeth, while the external gear 185 has 83 teeth. The gear shaft crank arm 177 provides a 15.6 mm (0.615 inch) arm to cause the magnet housing assembly 110 to have a total stroke of 31.2 mm (1.23 inches) in a water chamber 30 having an inside lower diameter of approximately 394 mm (15.51 inches) at its bottom end facing the target backing plate 20. The outside of the magnet housing body 116 is approximately 219 mm (8.62 inches) in diameter with its body 116 having a centrally located open space having a diameter of approximately 50.8 mm (2 inches). Cooling liquid 40 is introduced into the water chamber 30 through tubing 66 connecting to the internal passages of the rotating support/seal block 60 and passes into, through, and out of the drive shaft 140, .through the tubing 148, and into the magnet housing cooling channel 136 from which the cooling liquid is distributed by uniformly spaced orifice water outlets 135 on the face of the magnet housing body 116 facing the backside of the target backing plate 20. Cooling liquid 40 is thereby routed and injected into the water chamber 30 at the space between the backside of the target backing plate 20 and the front face of the magnet housing assembly 110 through orifices disposed at 45° directed toward the location of the magnet track in a circular pattern having a diameter smaller than any portion of the magnet track 130 containing the magnets. The flow of the cooling liquid 40 past the back of the target backing plate 20 can cause turbulent flow along its surface, which will enhance the fluid's transfer of heat. The magnetic field created by the magnets 121, . . ., 125, concentrates the sputtering action and to a lesser extent the heat generated by that sputtering action in the target backing plate in the path of those magnets as they are moved. While the sputtering action is instantaneous and localized, causing localized hot spots on the target's surface, the heat the sputtering generates, as it is conducted through the target 10 and the target backing plate 20, is spread to an area much larger than those localized hot spots and reaches the back of the target backing plate 20 at a predetermined time after the magnets inducing sputtering have already moved to another location. Cooling liquid 40 is routed and directed toward the target backing plate 20 such that the cooling liquid with the lowest temperature is routed and directed at the back of the target backing plate 20 in an area where the backing plate's temperature would rise without this cooling. The cooling system for this sputtering device provides that as the magnet housing assembly 110 containing the magnets 121, . . ., 125, rotates and oscillates, cooling liquid injection nozzles 135 in the magnet housing assembly 110 also move and oscillate with the magnets. The cooling liquid thereby cools the back of the target backing plate 20 with a high efficiency by directing a stream of cooling liquid at a selected area of the back surface of the heated target backing plate 20. If cooling liquid were not directed at the back of the target backing plate 20 the plate's temperature would rise until the difference between the plate's temperature and its surrounding cooling fluid would be enough to generate natural convective fluid currents for heat transfer. However, as a result of the coldest cooling liquid being forcibly directed at a selected area on the back of the target backing plate 20 which is receiving thermal energy from the sputtering process, the cooling liquid forcibly flowing across the surface of the back of the target backing plate 20 provides high efficiency cooling and thereby immediately reduces the temperature of the target backing plate 20 to be in equilibrium with the temperature of the cooling liquid 40 in contact with it. In this embodiment, the water chamber 30 is oriented in such a fashion that the target 10 is horizontal facing down and the water chamber 30 is above it, as shown in Figure 1, such that cooling liquid 40 being injected into the chamber 30, directed at the back of the target backing plate 20, fills up the water chamber 30, and with relatively little back pressure exits the water outlet fitting 31 on top of the water chamber 30. The flow rate of cooling liquid 40 through the water chamber 30 as Drescribed for this embodiment is 19-38 litres (5-10 gallons) per minute and the cooling nozzles 135 approximately 36 in number have a diameter of approximately 1.57mm (.062 inches) each. These cooling nozzles provide a very efficient heat transfer at the back of the copper target backing plate 20. The very efficient heat transfer at this copper-to-cooling liquid interface allows the sputter target to sustain high dissipated power densities for prolonged periods of time without excessive target temperatures. The injected cooling liquid 40 is forced to flow between the sweeping magnet housing assembly 110 and the copper target backing plate 20 which thereby provides increased heat transfer efficiency. The cooling liquid 40 (water or other) then fills a large low pressure (nearly no back pressure) liquid cavity behind the plate until it reaches its overflow (the water outlet fitting 31) from which it flows away. A generalized cooling of the target backing plate 20 is provided qnce the cooling liquid 40 has exited the magnet housing assembly 110 and starts to mix with the mass of cooling liquid 40 in the water chamber 30 which is bathing the rotating mechanism 100. In the present embodiment, about eighty percent of the sputter power of approximately 30 kilowatts is dissipated in target backing plate 20, which is 15.9mm (0.625 inches) thick and 374.7mm (14.75 inches) in diameter. Inlet cooling liquid pressure is approximately 0.012 kgm⁻² (40 psi). The target backing plate 20 is made of oxygen-free, high conductivity copper (OFHC). As the target backing plate 20 is made from a simple flat plate and requires relatively little machining, production costs are relatively modest. The cost savings over time may be significant, as the target backing plate 20 is replaced each time the target thickness has been depleted to a point where a high probability of imminent target breakthrough exists. Figure 6 shows a close-up of the cooling channel 136 in the magnetic housing assembly 110, from the back of the assembly over the water inlet connecting hole 113, as seen in Figure 1. Figure 7 is a cross section of Figure 6 cut at 10-10. The diffusion ring 137 is supported by a fixing means 133 one of several connected to the magnetic housing cover 115. In this embodiment the fixing means is a screw post. Circular slot gaps 134a and 134b of approximately 0.040 inches are provided between the edges of the diffusion ring 137 and the adjacent walls of the cooling channel 136. Figure 8 shows a cross section of Figure 6 cut at 11-11. The magnet housing cover inlet water fitting 112 provides a flow path for cooling liquid 40 into the cooling channel top portion 138. The slots 134a, 134b prevent the cooling liquid from immediately flowing to the cooling channel bottom portion 139 and out the cooling nozzle 135y, during normal operation. The normal flow of cooling liquid is so high that it is restricted by the slots, so that the slots 134a and 134b act as orifices to regulate flow (and thereby pressure) from the cooling channel top portion 138 to the cooling channel bottom portion 139. These slots restrict the flow so that the pressure to the nozzle orifice 135y closest to water inlet fitting 112 will be nearly equal to the pressure at a nozzle most distant from the water inlet fitting 112. This will provide nearly equal flow rate and velocity through each of the equally sized orifices 135. While our invention has been described with respect to the embodiments set forth above, our invention is not to be considered limited thereto.

Claims: A planar magnetron sputtering apparatus comprising: a cooling chamber (30); a thermally conductive target plate (20) having a front side (21) and a back side (22), the front side of the target plate being adapted to receive a sputter target (10) and the back side of the target plate forming a portion of a wall of the cooling chamber; a magnet assembly (110) mounted in the cooling chamber for sweeping a magnet (121-125) across the back side of the target plate; a cooling assembly mounted in the cooling chamber for sweeping a surface (117) of a body (116) across the back side of the target plate in coordination with the magnet assembly, the surface being opposite the back side of the target plate and maintained parallel to and in proximity to the back side of the target plate and comprising ports (135) for introducing cooling liquid from the body directly into a volume between the surface and the back side of the target plate; and a cooling chamber drain (42). An apparatus as claimed in claim 1, wherein the ports are directed towards the back side of the target plate for impinging streams of cooling liquid thereon. An apparatus as claimed in claim 1 or 2 wherein the magnet assembly and the cooling assembly are integrated, and wherein the body comprises the magnet. An apparatus as claimed in claim 1, 2 or 3 having: a cooling channel (136) disposed in the body; a cooling channel inlet (112); and means for providing the cooling liquid (40) under pressure to the cooling channel inlet; the ports comprising a plurality of nozzles connected to the cooling channel for discharging cooling liquid from the cooling channel. An apparatus as claimed in claim 4 wherein the cooling channel comprises a diffusion ring (137) mounted therein, and wherein the diffusion ring is disposed to intercept pressurised cooling liquid introduced through the cooling channel inlet and to distribute the cooling liquid to the nozzles at a uniform pressure. An apparatus as claimed in any preceding claim wherein the cooling chamber drain is a negligible back pressure drain. A coolable sputtering target plate assembly comprising: a cooling chamber (30); a target plate (20) having a front side (21) for receiving a sputtering target and a back side (22) forming a portion of a wall of the cooling chamber; a rotatable drive shaft (140) having a hollow portion; inlet means (60) for rotatably supporting the drive shaft and for routing and sealing a cooling liquid (40) flowing from an inlet connection (63) to the hollow portion of the drive shaft; outlet means (144) for routing the cooling liquid from the hollow portion of the drive shaft, the outlet means being operatively supported from the drive shaft; and a housing (116) operatively coupled to the drive shaft for sweeping a planar surface (117) thereof across the back side of the target plate, the housing comprising a cooling channel (136) coupled to the outlet means for receiving pressurised cooling fluid from the hollow portion of the drive shaft, the housing having disposed therein ports (135) for directing a stream of cooling fluid from the channel to impinge on the back side of the target plate. An assembly as claimed in claim 7 wherein the housing and the outlet means are rotatable with the drive shaft. An assembly as claimed in claim 7 or 8 having a cooling chamber outlet fitting (42), wherein cooling liquid dispensed from the nozzles collects in the cooling chamber with a substantially minimal back pressure and is conducted to the cooling chamber outlet fitting. An assembly as claimed in claim 9 wherein the cooling chamber outlet fitting is disposed at a higher level in a gravitational field than the target plate. An assembly as claimed in claim 7, 8, 9 or 10 wherein the inlet means comprises a rotary joint including a joint body having: a cooling liquid receiving section (69) at a longitudinal center of the body, the inlet connection of the inlet means opening into the cooling liquid receiving section; a sealing section (68a,68b) adjacent to each end of the cooling liquid receiving section; and a bearing section (67a, 67b) adjacent to each sealing section and opposite the cooling liquid receiving section. An assembly as claimed in claim 11 wherein the sealing section comprises a resilient ring (74) having a "U-shaped" cross section disposed in a sealing channel (72) surrounding the drive shaft with the open side of the "U"-shape facing the cooling liquid receiving section, wherein one side of the "U"-shaped section rests against a side of the drive shaft, wherein a second side of the "U"-shaped section rests against a side of the sealing channel, and wherein a bottom end of the "U"-shaped section rests against a sealing washer. An assembly as claimed in claim 11 or 12 wherein a portion of the drive shaft is enclosed by the cooling liquid receiving section and the sealing section of the rotary joint and includes cross drilled holes (146) disposed therein for providing a passage for cooling liquid to flow from the cooling liquid receiving section of the rotary joint into the hollow portion of the drive shaft. An assembly as claimed in any one of claims 7-13 wherein the outlet means comprises: a drive shaft end block (144) having an outlet connection (147); and a flexible tube (148) having one end connected to the outlet connection of the drive shaft end block and another end connected to the cooling channel (136). An assembly as claimed in claim 14 wherein the outlet means is supported by said drive shaft in a manner such that said cooling channel can be oscillated with respect to said drive shaft, and wherein said flexible tube accommodates the oscillatory motion while maintaining a fluid connection between the outlet connection of said drive shaft end block and said cooling channel. An assembly as claimed in any one of claims 7-15 wherein the cooling channel contains a diffusion ring (137) which causes a cooling liquid pressure to be distributed around the cooling channel to equalise the pressure of a cooling liquid reaching the nozzles. A magnet housing unit (110) for sweeping behind the target support plate (20) of a planar magnetron sputtering apparatus, comprising: a supporting body (116) having a surface (117) thereof adapted for sweeping behind the target support plate; a magnet track (130) disposed in the support body; a fluid line (112) disposed in the support body for receiving pressurised cooling fluid (40); a fluid channel (136) provided in the supporting body, the fluid channel being connected to the fluid line; and a plurality of ports (135) from the channel to the supporting body sweeping surface. A method of cooling a target plate (20) in a magnetron sputtering apparatus comprising a magnet assembly (110) movable in a cooling chamber (30), wherein the target plate is thermally conductive and has a front side (21) and a back side (22), the front side of the target plate being adapted to receive a sputter target (10) and the back side of the target plate forming a portion of a wall of the cooling chamber, and wherein the cooling chamber contains cooling liquid (40) and the magnet assembly is swept across the back side of the target plate, the method comprising the steps of: sweeping a surface (117) of a body (116) across the back side of the target plate in coordination with the magnet assembly, the surface being opposite the back side of the target plate and maintained parallel to and in proximity with the back side of the target plate; discharging cooling liquid from the body directly into a volume between the surface and the back side of the target plate; and draining cooling liquid from the cooling chamber. A method as claimed in claim 18, wherein the discharging step comprises directing cooling liquid from the body so as to impinge on the back side of the target plate. A method as claimed in claim 18 or 19 wherein the body comprises the magnet assembly. A method as claimed in claim 18, 19 or 20 comprising the step of providing cooling liquid under pressure to a cooling channel (136) in the body, and wherein the discharging step comprises discharging cooling liquid from the cooling channel through a plurality of nozzles (135) in the body. A method as claimed in claim 21 comprising the steps of introducing a cooling liquid into the cooling channel at a predetermined inlet pressure, and uniformly distributing the inlet pressure throughout the cooling channel. A method as claimed in claim 21 or 22 wherein the draining step comprises draining cooling liquid from the cooling channel with negligible back pressure.

Inventors: BROADBENT ELIOT K, MILLER KENNETH C, BROADBENT, ELIOT K., MILLER, KENNETH C.
Applicants: NOVELLUS SYSTEMS INC, NOVELLUS SYSTEMS, INC.
Application year: 1991
Main classification: H01J37
IPC codes: C23C14, H01J37, H01L21