WO1996006205A9 - Support charge par ressort pour cathode de pulverisation rotative - Google Patents

Support charge par ressort pour cathode de pulverisation rotative

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Publication number
WO1996006205A9
WO1996006205A9 PCT/US1995/010818 US9510818W WO9606205A9 WO 1996006205 A9 WO1996006205 A9 WO 1996006205A9 US 9510818 W US9510818 W US 9510818W WO 9606205 A9 WO9606205 A9 WO 9606205A9
Authority
WO
WIPO (PCT)
Prior art keywords
cathode
dark space
cylindrical
frontal
space shield
Prior art date
Application number
PCT/US1995/010818
Other languages
English (en)
Other versions
WO1996006205A1 (fr
Filing date
Publication date
Application filed filed Critical
Publication of WO1996006205A1 publication Critical patent/WO1996006205A1/fr
Publication of WO1996006205A9 publication Critical patent/WO1996006205A9/fr

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Definitions

  • the present invention relates generally to magnetron sputtering apparatus, and more particularly to rotating magnetron cathodes with a spring-loaded mount.
  • DC reactive sputtering is a most frequently used deposition process for large area commercial coating applications, such as the application of thermal control coatings to architectural and automobile glazing.
  • the articles to be coated are passed through a series of in-line vacuum chambers isolated from one another by vacuum locks. This system may be referred to as a continuous in-line system or a glass coater.
  • a sputtering gas discharge is maintained at a partial vacuum at a pressure of about 3 millitorr.
  • the sputtering gas comprises a mixture of an inert gas, such as argon, with a small proportion of a reactive gas, such as oxygen, for the formation of oxides.
  • Each chamber contains one or more cathodes held at a negative potential of about -200 to -1000 volts.
  • a layer of material to be sputtered covers the cathode surface. This surface layer is known as the target or the target material.
  • the reactive gas forms the appropriate compound with the target material. Ions from the sputtering gas discharge are accelerated into the target and dislodge, or sputter off, atoms of the target material. These atoms, in turn, are deposited on a substrate, such as a glass sheet, passing beneath the target. The atoms react on the substrate with the reactive gas in the sputtering gas discharge to form a thin film.
  • the rotary or rotating magnetron developed to overcome some of the problems inherent in the so-called planar magnetron, uses a substantially cylindrical cathode and target.
  • the target is rotated continually over a magnet array which defines a sputtering zone, such that a new portion of the target is continually presented to the sputtering zone. This has the favorable effects of easing cooling problems and allowing higher operating powers.
  • the rotation of the target also ensures that the erosion zone comprises the entire circumference of the cathode covered by the sputtering zone. This increases target utilization.
  • the rotating magnetron is described further in U.S. Patent Nos. 4,356,073 and 4,422,916, the entire disclosures of which are hereby incorporated by reference.
  • the rotating magnetron requires bearings to permit rotation, and vacuum seals for the drive shaft, the electrical conduits and the cooling conduits. Vacuum and rotary water seals have been used to seal around the drive shaft and the conduits which extend between the coating chamber and the ambient environment.
  • Various mounting, sealing and driving arrangements are described in U.S. Patent Nos. 4,443,318; 4,445,997; and 4,466,877, the entire disclosures of which are also hereby incorporated by reference.
  • These patents describe rotating magnetrons mounted horizontally in a coating chamber and supported at both ends, each end of the cathode being attached to a spindle held by bearings attached to a sputtering chamber sidewall.
  • a cantilever mounted magnetron usually includes a bearing housing containing a drive shaft, a rotary vacuum seal, and at least two bearings spaced along the drive shaft, one of which may function as a shaft seal.
  • Cantilever-mounted magnetron removal does not require removal of a difficult to remove sidewall mounting structure to provide the necessary clearance, and cantilever-mounted magnetrons require only one rather than two rotary seals.
  • a rotating magnetron incorporating a cantilever mounted removable cathode detachable from its bearing assembly is described in U.S. Patent No. 5,100,527, assigned to the assignee of the subject application, the entire disclosure of which is hereby incorporated by reference.
  • Such a system allows, among other things, the cathode to be removed easily and without special equipment, thus reducing system down time both by reducing the time required to replace a cathode and by making simultaneous removal of two or more cathodes more practical.
  • a cantilever-mounted cathode having low vacuum seal loads is described in U.S. Patent No. 5,200,049, assigned to the assignee of the subject application, the entire disclosure of which is hereby incorporated by reference.
  • a dark space shield or sleeve may be concentrically disposed about the cathode body and spaced from its surface to form a gap. The distance across this gap is less than the dark space length.
  • the dark space is the region of gas discharge next to the cathode.
  • the electrons accelerate under an applied operating voltage to become adequately energized to cause ionization of the sputtering gas.
  • the dark space length is a function of the type of sputtering gas, the gas pressure and the applied electric field.
  • the dark space length for example, may be on the order of three millimeters.
  • the dark space shield usually provided with means for attachment to a suitable mounting surface, protects a portion of the cathode body from the gas discharge and resultant ion bombardment.
  • Dark space shields are usually provided at both ends of the cathode.
  • the shield around the drive end of the cathode body should prevent the sputtering gas discharge from contacting that end.
  • the mounting surface has been the chamber wall or a flange attached to the chamber wall, such that the dark space shield does not rotate with the cathode.
  • the shield may also be electrically insulated from this mounting surface so that it is electrically isolated therefrom. The shield then floats electrically and acquires an electrical potential of the gas discharge.
  • a preferred material for the shield is stainless steel.
  • a film of deposited material grows on the dark space shield, usually under tensile or compressive stress. The stress is highest on sharp edges. Eventually the film deposited begins to spall off, beginning usually on such sharp edges and on areas where the film is thickest. If the resulting flakes of material fall onto a substrate, they obstruct deposition on the areas of the substrate that they cover, resulting in defective products. In order to minimize the rate of film growth on a given dark space shield surface, that surface should point in a direction as close as possible to the direction away from the sputtering target.
  • the spacing between the dark space shield and the cathode must be well controlled to be less than a dark space length and to ensure that the shield does not touch the cathode.
  • the cantilever mounting arrangement produces a high bearing load, especially if a heavy target material, such as niobium, is used.
  • High bearing loads have a detrimental effect on bearing life. Relieving the load on the bearing using an outboard support must allow for radial displacement of the free end to avoid additional loads.
  • an object of the present invention is to provide a rotating magnetron cathode with one end adapted to be attached to a spindle and the other end adapted to be supported such that the force on the bearings can be reduced, while maintaining the advantages of cantilever-mounted cathodes of clearance between and end of the cathode and a sidewall for easy removal, and need for only one rotary vacuum seal.
  • the rotating magnetron apparatus of the present invention includes an evacuable chamber containing a cathode.
  • the cathode has a first end detachably attached to a drive shaft and a second end distal from the first end.
  • the second end is supported by spring loaded supporting means attached to a chamber wall.
  • the supporting means allows radial displacement of the second end.
  • the cathode of the present invention may comprise a cylindrical tubular structure with a first end rotatably supported and a second end distal from the first end.
  • a dark space shield is rotatably mounted onto the cylindrical structure at the second end, without electrical contact to the cylindrical structure.
  • Fig. 1 is a cross-sectional, schematic view of a sputtering chamber containing a rotatable magnetron cathode, taken in a vertical direction parallel to the cathode.
  • Fig. 2 is a cross-sectional view of the sputtering chamber of Figure 1 taken along line 2-2 of Figure 1.
  • Fig. 3 is a partially sectional, exploded view of the drive end dark space shield assembly of Fig. 1.
  • Fig. 4 is a sectional side view of the upper half of an end portion of the cathode of Fig. 1 where it connects the drive shaft.
  • Fig. 5A is a view of the rotating dark space shield of Figs. 2 and 3 taken along line 5A-5A of Fig. 3, and Fig. 5B is its cross-sectional view taken along line 5B-5B of Fig. 5A;
  • Fig. 6A is a cross-sectional view of the spring- loaded mounted end portion of the cathode of Figs. 1 and 4, and Fig. 6B is an exploded view of Fig. 6A.
  • Fig. 7A is a partial cross-sectional and exploded view of the spring-loaded mount of Figures 1 and 2
  • Fig. 7B is a plan view taken along line 7B-7B in Fig. 7A
  • Fig. 7C is a cross-sectional view taken along line 7C-7C of Figure 7A.
  • FIG. 1 and 2 show an evacuable sputtering chamber 41 bounded by walls 44 and sealed by a cover 32, containing a rotatable magnetron apparatus 42 which comprises a tubular cathode 52.
  • a substrate 36 to be coated may be transported through the sputtering chamber 41 on rollers 38 mounted on a spindle 40.
  • the spindle may be supported on bearings 37 attached to a floor 33 of the sputtering chamber 41.
  • the cathode 52 has its tubular body attached by welding or bolting to a mounting flange 50 at one end, adapted to be connected to a front flange 48 of a drive shaft (shown at 68 in Figs.
  • a rotating dark space shield 54 is attached to the cathode 52 so as to rotate therewith.
  • the dark space shield 54 may be attached to the cathode mounting flange 50 by means, for example, of three lock pin and socket assemblies 56 positioned 120° apart from one another around the axis of the cathode 52.
  • Stand-off insulators 58 maintain a minimum spacing between the shield 54 and the flange 50 and may be positioned diametrically opposite the lock pin and socket assemblies 56.
  • Fig. 3 shows more in detail the manner of attaching the shield 54 to the flange 50, sockets 64 and O-rings 66 being inserted into a recess 63 of the cathode flange 50 before mounting the cathode 52 to the drive shaft flange 48, for example, by bolting.
  • Lock pins 60 are secured to the shield 54 using retainers 62, and the O-rings 66 resist deformation of the sockets 64 to thereby improve lock pin retention.
  • the shield 54 is attached to the flange 50 by inserting the pins 60 into the sockets 64.
  • Arrangements for rotating, cooling and shielding the cathode 52 are explained next with reference to Fig. 4 which, however, will show only the upper half of the portion of the cathode 52 connecting to the drive shaft 68, the lower half being symmetrical to the upper half.
  • reference numeral 49 indicates a flange which is welded to the chamber wall 44 supporting a bearing housing 51, the cathode 52 and the drive shaft 68.
  • the bearing housing 51 is mounted on the exterior side of the flange 49 relative to the sputtering chamber 41.
  • the water ring 46 with a cooling channel 47 inside is mounted on the interior side of the flange 49 relative to the sputtering chamber 41 and is covered by a cleanable aluminum cover 45.
  • the drive shaft 68 is hollow and is held within the bearing housing 51 by a bearing 34 and is sealed against the bearing housing 51 by a rotary seal 81 or, preferably, a ferrofluidic seal incorporating a colloidal suspension of ultramicroscopic magnetic particles in a carrier liquid.
  • Drive shaft 68 is rotated relative to bearing housing 51 by a motor (not shown) .
  • the drive shaft flange 48 is secured to the drive shaft 68 by a nut 82.
  • Concentric with and inside the hollow drive shaft 68 is a cooling fluid transport tube 70 which, together with the drive shaft 68, defines inner and outer cooling fluid conduits 71 and 69, respectively.
  • the fluid transport tube 70 does not rotate with the drive shaft 68 but is held concentric with the drive shaft 68 by a centering ring 77. Externally, the cathode 52 is covered over most of its length by a target material 78.
  • the cathode 52 may be covered with a collar (such as collar 80 of Figure 4) of a material such as titanium to reduce arcing and increase maximum power as described in co-pending U.S. Patent Application Serial. No. 08/016,492, assigned to the owner of the subject application, the entire disclosure of which is hereby incorporated by reference.
  • the collars 80 may also extend the target life by reducing erosion at the plasma "racetrack"-turnarounds where the power density is greatest.
  • a check valve 76 for stopping the flow of coolant when the cathode 52 is removed is mounted on a check valve mounting flange 74.
  • Reference numeral 79 indicates a bushing which rotatably supports therein a fluid transport tube 72, which, together with cathode 52, defines inner and outer cooling fluid conduits 73 and 75, respectively.
  • the lock pins 60 have a body member with a tapered end 60b to facilitate insertion into the socket 64 and a neck 60c which, when the dark space shield 54 is mounted, is engaged by a matching bore of the socket 64.
  • the sockets 64 also have a base 64a for retention inside the recesses 63 of the cathode mounting flange 50 and a groove for the O-ring 66 for improved pin retention.
  • the sockets 64 are made of an electrically-insulating material such as nylon such that the dark space shield 54 is electrically floating relative to the cathode 52. More detailed descriptions of other components such as the retainers 62, the lock pins 60 and the sockets 64 are given in U.S. Patent Application Serial No.
  • FIGs. 1, 6A and 6B show the spring-loaded mounted end of the tubular part of the cathode 52 distal from the flange 50 and the drive shaft 68.
  • This end part may be characterized briefly as having a front end flange 10 covered by, but not in direct contact with, another dark space shield 20 (hereinafter to be referred to as "the front dark space shield” or simply “the front shield” in order to distinguish from the dark space shield 54 described above) .
  • the front end flange 10 has a generally disk-shaped base 13 with a generally flat front surface 13' and a cylindrical part 11 protruding axially (with respect to the cylindrical part of the cathode 52) forward (to the left with reference to Fig. 6A) from the center of the base 13.
  • the front shield 20 has a circular disk-shaped base part 21 adapted to be positioned in a face-to-face but electrically non-conducting relationship with, and separated by a well-controlled distance less than the dark space length from, the front surface 13' of the base 13 of the front end flange 10 when the front shield 20 is properly mounted, as will be discussed below.
  • the front shield 20 has a peripheral cylindrical tubular part 22 (referred to as the sleeve) protruding backwards towards the cathode 52 from the outer periphery.
  • the sleeve 22 is below a line of sight from the cathode surface such that growth of any sputtered coating thereon will be prevented.
  • the external diameter of the sleeve 22 is smaller than that of the cylindrical part of the cathode 52, whose end 52' is tapered. Since the sleeve 22 is intended to cover the front surface of the base 13 of the front end flange 10, the base 13 has a frustoconical part such that its outer diameter at the front surface is even smaller than the inner diameter of the sleeve 22, as shown in Fig. 6A.
  • a tubular part 23 with a cylindrical inner surface protrudes forward axially from the disk-shaped base part 21 of the front shield 20, such that the cylindrical part 11 protruding from the front end flange 10 can be inserted and engage rotatably with the inner cylindrical surface of the tubular part 23 of the front shield 20 with a tubular insulator bearing 15 made, say, of vespel inserted in between.
  • the cylindrical part 11 of the front end flange 10 is provided with a screw-accepting hole 12 in the axial direction, a thrust washer 17 of a steel material is inserted from the front into the vespel insulator bearing 15, and a steel screw 18 is passed through this washer 17 and further into the screw- accepting hole 12 of the front end flange 10 of the cathode 52 so as to support the front end flange 10 rotatably therearound.
  • the front dark space shield 20 can rotate around bearing 15 relative to cathode 52, and hence the cathode 52 can be rotated freely while the shield 20 remains stationary.
  • a circular steel cover piece 25 with a vent hole 26 therethrough is mounted onto and fastened to the tubular part 23 of the shield 20.
  • Vent hole 26 is used to evacuate the space covered by cover piece 25.
  • the cathode 52 according to this invention is supported at its free end from below by a yoke 100 of the spring-loaded mount 111, as shown in Fig. 2.
  • Both arms of the yoke 100 are provided with vespel insulator buttons 101 ( Figures 7A- 7C) which are used as spacers to separate shield surface 21 from yoke 100 and, together with vespel insulator pad 105 by which the cover piece 25 of front shield 20 is supported, prevent electrical contact between yoke 100 and shield 20.
  • the frontal dark space shield 20 is insulated from yoke 100 and floats electrically.
  • Each insulator button 101 is attached to yoke 100 using a set-screw and screw accepting hole 136.
  • Pad 105 is bolted onto yoke 100 using holes 134 of the pad and screw accepting holes 132 of the yoke.
  • Yoke 100 is welded to a pair of spring loaded supporting devices 110 attached to a bar 112 ( Figure 2) which is in turn attached to the wall of sputtering chamber 41.
  • each device 110 has a housing 116 with two generally cylindrical cavities 122. Near the top of cavities 122, their diameter decreases to form a horizontal surface 130 for engaging the top of springs 120. The bottoms of springs 120 rest against surface 128 of supports 118. Supports 118 are held by bolts 114 which are bolted to bar 112 as shown in Figure 1.
  • the diameter of cavities 122 is larger than the diameter of bolts 114 such that housing 116 can move laterally while being supported vertically by springs 120.
  • housing 116 has a dimple 126 on its top surface.
  • Dimple 126 is positioned underneath a threaded hole 124 in bar 112.
  • Hole 124 and dimple 126 allow lowering of yoke 100 to release cover piece 25, by threading a bolt through hole 124 and using it to press against dimple 126 to lower housing 116 with respect to bar 112.
  • a rotatable magnetron cathode has a dark space shield attached both at its drive end where it is connected to the drive shaft of its drive motor and at its opposite and free end such that the gap between these shields and the cathode can be reliably controlled.
  • a spring loaded-mounting mechanism is provided at the cathode's free end.
  • the spring-loaded mounting mechanism includes insulator buttons and a pad so as to reliably maintain the front shield in an electrically floating condition.
  • the spring-loaded mount assembly reduces the load on the bearings caused by the magnetron weight as the cathode rotates.
  • the spring-loaded mount also allows radial displacement of the free end of the cathode without stressing the bearings.

Abstract

Une cathode rotative (52) de magnétron comporte une extrémité se fixant à un arbre d'entraînement (68) et une extrémité libre supportée par un joug (100) suspendu à des dispositifs-supports chargés par ressort (111) qui sont fixés à une paroi de la chambre de pulvérisation. Un écran à zone sombre (54) est fixé à la cathode, cette dernière se raccordant à l'arbre d'entraînement de son moteur de façon à ce que l'arbre tourne avec la cathode. Un autre écran à zone sombre (20) est fixé au niveau de l'extrémité libre de la cathode, un palier isolant étant placé entre les deux de sorte que la cathode puisse tourner sans faire également tourner l'écran au niveau de sa partie frontale. Un coussin isolant est placé entre le joug et une pièce de couverture métallique fixée à la partie frontale de l'écran de façon à maintenir l'écran à zone sombre frontale dans un état de flottement électrique.
PCT/US1995/010818 1994-08-24 1995-08-24 Support charge par ressort pour cathode de pulverisation rotative WO1996006205A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US29629594A 1994-08-24 1994-08-24
US08/296,295 1994-08-24

Publications (2)

Publication Number Publication Date
WO1996006205A1 WO1996006205A1 (fr) 1996-02-29
WO1996006205A9 true WO1996006205A9 (fr) 1996-05-02

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/US1995/010818 WO1996006205A1 (fr) 1994-08-24 1995-08-24 Support charge par ressort pour cathode de pulverisation rotative

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Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5108574A (en) * 1991-01-29 1992-04-28 The Boc Group, Inc. Cylindrical magnetron shield structure
DE4117518C2 (de) * 1991-05-29 2000-06-21 Leybold Ag Vorrichtung zum Sputtern mit bewegtem, insbesondere rotierendem Target

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