WO1989010430A1

WO1989010430A1 - Vacuum coating system

Info

Publication number: WO1989010430A1
Application number: PCT/US1989/001772
Authority: WO
Inventors: Larry E. Homstad
Original assignee: American Thin Film Laboratories, Inc.
Priority date: 1988-04-27
Filing date: 1989-04-27
Publication date: 1989-11-02

Abstract

In vacuum coating deposition systems an improved mobile roll coater of compact construction for the sputter deposition of thin films, the roll coater having an improved winding configuration which maximizes the area available for positioning source targets (24) at desirable angles of incidence relative to the roll coater chill drums (10 and 12) over which the roll to be coated moves. The overall vacuum deposition systems described may also include computer control (70).

Description

VACUUM COATING SYSTEM'^' BACKGROUND This invention relates to thin film coating deposition systems of the vacuum coating type generally and more particularly to improved winding configurations used with roll coaters for use in vacuum coating systems, especially in sputtering vacuum coating systems. Vacuum coating deposition of thin films covers a broad class of coating processes in which material is removed from a source and deposited on a substrate, the process being carried out in a vacuum or partial vacuum. For example, when one considers vapor deposition one will include chemical vapor deposition in which gaseous chemical compounds react and deposit on heated substrates. In ion vapor deposition, an inert gas is ionized and a high negative potential is applied to the substrate to be coated. The coating metal is melted and vaporized then ionized to accomplish the coating procedure. Lastly, there is physical vapor deposition in which material is physically removed from a source by evaporation or sputtering, transported through a vacuum or partial vacuum by the energy of the vapor particles and condensed as deposited coating or a film on the surface of a substrate. A myriad of physical vapor processes are known including diode or triode sputtering planar or cylindrical magnetron sputtering, direct current or radio frequency sputtering, electron beam evaporation, activated reactive evaporation and arc evaporation. This invention most specifically relates to sputtering and will be specifically described with reference thereto. When rolls of flexible substrate material are to be coated by vacuum deposition, the process is referred to as "roll coating". This invention most specifically relates to roll coating. Typically, rolls of polyester or polyimide are used as flexible substrates in roll coating although a wide variety of other roll materials may be used including other plastic films , metallized papers, fabrics and even sheet metals. The improved rol l coater and winding configuration of the invention is broadly applicable for use in all of the various vacuum coating procedures including chemical vapor deposition and ion vapor deposition as well as physical vapor deposition processes. However, it is described herein particularly with respect to the sputtering process as applied to roll coating. In a typical roll coater, a roll of flexible substrate material, also known as a web, is carried on a feed roll. The substrate is threaded or led through various idler, drive and tension control rolls, passed through the coating region and taken up on a take-up roll after being coated. The apparatus is operated in a vacuum chamber. A pumping system evacuates the vacuum chamber to a low pressure, for example approximately 1.0 x 10 ~- torr or so. After evacuation is attained the chamber is backfilled with an inert gas, typically, argon, to a pressure of 2 x 10 ^"~ torr or so. In roll sputtering, as in the preferred embodiments of this invention, the flexible substrate passes through a cloud of charged particles at a specific rate. Positively charged ions in a plasma (cloud of charged particles) strike a negatively biased source target, causing metal atoms to be ej cted from the target toward the substrate surface. The ejected metal atoms strike and adhere to the substrate, forming a thin coating. After the entire roll is coated, the vacuum chamber is opened and the coated roll is removed-. SUMMARY OF THE INVENTION Generally, sputtering is the deposition of materials under vacuum onto substrates. Sputtering differs from vacuum metallizing (evaporation) in that the material is removed from a solid cathode or source target instead of being vaporized by a heating source. Rapidly moving gas ions in the vacuum chamber strike a negatively biased source target causing metal atoms to be ejected through a transfer of momentum. Subsequently, the target atoms strike and adhere to the substrate surface forming a thin coating. Some of the more common sputtering methods are planar diode, triode, magnetron and ion gun sputtering, all of which are adaptable to the subject invention. Direct current discharges are generally used for sputtering conductive substrates; a radio frequency (RF) potential is applied to the source target to sputter nonconducting substrates. Reactive sputtering can be performed with the addition of small controlled amounts of a reactive gas, such as oxygen to argon. In its preferred embodiment, this invention is concerned with vacuum coating systems for sputtering thin films of various materials onto flexible substrates in which a roll of flexible substrate (web) with a leader portion is set up; the leader portion is led through a roll handling mechanism, which includes a pair of chill drums, in a predetermined path to expose both sides of the substrate for coating by source targets. Then the coated substrate is moved to a take-up roll. In operation, the system is evacuated; sputtering gas(es) are bled into the system; the roll mechanism is started; the source targets are turned "on"; the flexible substrate winds through the mechanism and receives the deposition coating on both sides as it passes between the source targets and the chill drums. When all of the flexible substrate has been coated, the vacuum valves are 1 closed and the system is vented with a clean dry gas.

2 The coated substrate may then be transferred from the

3 take-up roll to another core for subsequent handling.

4 All of the operations described may be

5 preprogrammed and computer controlled as described in the

6 aforementioned related application or the system can be

7 operated in a fully manual or automatic mode. Vital

8 functions have feedback and active control when under

9 computer control and data is updated preferably twice per 0 second; control signals output at the same rate. The 1 system provides "pinhole-free" deposited thin films of 2 various materials. 3 4 5 16 17 18 19 20 21 22

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36 Brief Description of the Drawings Fig. 1 is a schematic showing of the improved winding configuration in a roll coater operating in a vacuum environment; Fig. 2 is a schematic front view showing of the vacuum chamber and related controls; Fig. 3 is a schematic showing of the pumping arrangement and various lines (cooling, power, etc.) as they relate to the vacuum chamber; Fig. 4 is a schematic showing of the gas controls for the system; Fig. 5 is schematic showing of the temperature monitoring and control arrangement for the system along with the computer control; Fig. 6 is a schematic showing the overall installation; Fig. 7 is a perspective view of a preferred embodiment of the roll coater apparatus chassis mounted atop a transport dolly, showing some parts exploded; Fig. 8 is a front elevational view of the chassis of Fig. 7 with some parts exploded; Fig. 9 is a simplified sectional front elevation taken along line 9-9 in Fig. 7 with the transport dolly omitted; Fig. 10 is a front elevational view of the roll coater chassis with a coolant plumbing fixture added and connections to partial assembly shown; Fig. 11 is an enlarged top plan detail section taken along line 11-11 in Fig. 10; Fig. 12 is a perspective view of the containment vessel vacuum chamber in accordance with the present invention; Fig. 13 is a fragmentary front elevational view of the rear bulkhead of the containment vessel vacuum chamber; and Fig. 14 is a right side orthographic view of the elements of Fig. 13. Description of the Preferred Embodiments As already indicated, the preferred embodiment of the invention involves a sputtering deposition system including a roll coater of improved winding configuration as shown schematically in Fig. 1. That Figure shows two oppositely disposed chill drums 10 and 12 positioned one above the other pref rably directly above and below each other (side by side is also operable) . Preferably the apparatus is driven, as by a stepper motor 13, while the other drums idle and rotate with the movement of substrate material over their surface. stepper motor 13 may be of the type supplied by Superior Electric Company of Bristol, Connecticut as their Slo-Syn synchronous stepping motor type M172-FD-306 with a rating of 200 steps/revolution. Any relative positioning of the chill drums is acceptable so long as they allow the substrate to be coated to lie flat on both drums as it moves through the roll coater and so long as the path will include introduction of substrate 14 from a feed roll or the like 16 to a side portion of drum 10 on the same side of feed roll 16 as shown. Substrate 14 then extends over several idler/drive rolls generally indicated at 18 and extends upwardly over drum 10 and downwardly on its other side to cross the space between the drums and onto the side of drum 12 which is also on the same side as feed roll 16. Substrate 14 continues in a path which extends around the bottom portion of drum 12 and upwardly along its other side to another set of idler/drive rolls generally indicated at 20 and to a take-up roll 22. This winding configuration allows for maximum exposure of chill drum surface to a plurality of source targets 24 and for coating both sides of the substrate. Up to three source targets may preferably be positioned as shown with respect to each chill drum, allowing for multiple layer coating to take place. One or more target sources may also be used. Preferably three will be used. It is important to note that they may be positioned at an ideal angle of incidence with respect to the closest surface area of each drum i.e., at normal or perpendicular positions with respect thereto. Chill drums 10 and 12 are electrically isolated from the chamber 26 and may be biased or floated electrically. They are also provided with means for heating or cooling them. Referring now to Figure 2, a front view of the overall system with all the various instrument displays is shown. The ion gauge display is shown at 29. The manual valve sequencer display is shown at 31. The stepper motor display is shown at 33. The tension module displays are shown at 35. The six power supply displays are shown generally at 37. A viewport 27 allows for viewing of the process in the vacuum chamber during a run. Referring to Figs. 3 to 6, a more or less typical installation is shown for the system in a schematic form to provide a general overview of a complete installation. As can be seen, particularly in Figs. 3 and 6, the vacuum chamber 26 is preferably built into a wall 30 along one side of a clean room (not shown) forming an access room 34 behind wall 30. All pumps and services are accessed from room 34 behind the vacuum chamber. A vent valve 35 is shown at the bottom of chamber 26. This valve may be used to introduce a dry gas e.g., N₂ into the chamber following a coating run, in which case it would be suitably connected to a conduit arrangement (not shown) . Room 34 contains cryogenic pumps 36 and 38 with their respective cold heads 36a and 38a (only 38a shown in Figures) and Hi-Vac valves 36b and 38b (only 38b is shown in Fig. 3) . The Hi-Vac valves are preferably of the ten inch gate valve type supplied by Vacuum Research Corporation. Preferred pumps are CTI-10 Helium Cryogenic pumps and CTI-Cryogenic, Inc., 102R Helix Compressors. The installation also includes a roughing pump 40 (seen in Fig. 6) connected to Chamber 26 by valve 42. A preferred roughing pump is a Leybold- Heralus DK-200. As is best seen in Fig. 3, computer feed back loops 50 extend into Chamber 26 via feedthroughs 52 to provide for computer control . Gas inlets and flow controls 54 also extend into chamber 26 via feedthroughs. Sensors and power inputs 56 extend into chamber 26 via feedthroughs 58. Also, heating and cooling lines 60 extend into chamber 26. Preferably, electrical power to the source targets enters the vacuum chamber and contacts the source targets by means of the input conduits which ^' are of copper. Referring to Fig. 4, a gas control sub-system is shown. It includes vacuum chamber 26 to which gas inlet conduits 62 and 64 are connected. Conduit 62 extends to flow monitor 62a, to electrically operated metering valve 62b and to a gas container 62c which contains a first gas "A", such as argon. Conduit 64 extends to electrical flow monitor 64a, to an electrically operated metering valve 64b and to a gas container 64σ which contains a second gas "B", such as oxygen. One gas only may be used but two are preferred. It is also possible to use a third gas e.g.., nitrogen or carbon dioxide. A mass spectrometer 66 is connected to chamber 26 with its output connected to a computer 70 by input line 78. Computer output lines 72b and 74b attached to computer 70 extend to metering valves 62b and 64b, respectively. Input lines 72a and 74a extend to computer 70 from flow monitors 62a and 64a respectively. In operation, the desired ratio of gas "A" to gas "B" is set by computer 70 along with the total pressure. Data from the mass spectrometer 66 and flow monitors 62a and 64a is used by computer 70 to adjust metering valves 62b and 64b, respectively, in order to achieve the proper mix. Temperature monitoring and control of the chill drums 10 and 12 by computer 70 is shown schematically in Fig. 5. A source of heat and coolant flow (shown only schematically for simplicity) 80a and 82a respectively, is connected to each drum through electrically operated metering valves 80b and 82b, each of which is connected to computer 70 via output lines 80c and 82c. Preferably the heater (not shown) is of the type supplied by Watlow Company of Hannibal, Missouri as a Watlow heater model CBLC720L IOS2. The cooler (not shown) is preferably of the type supplied by Poly-Cold, Inc. of San Rafael, California. It is a freon chiller. Water is used in those devices as the working fluid. These items are shown here schematically only and are not specifically shown in subsequent Figures for the sake of simplicity. Flow of heat and coolant is controlled by a Flo-Tron 116 Series liquid flow control (not shown) and by thermocouple temperature monitor- 80g and 82g operating through electrically operated flow valves 80d and 82d, respectively, and check valves 80c and 82c. Flow valves 80d and 82d are connected to computer 70 by input lines 80e and 82e, respectively. They are also connected to the computer by computer output lines 80k and 82k, respectively. Temperature is sensed by electrical sensors 80g and 82g which are connected to computer 70 by input lines 8Oh and 8 h, respectively. Thus each chill drum can be controlled at its own predetermined temperature. Referring now to Figures 7-14, a more detailed description of the improved roll coater and vacuum deposition system installation is provided. Referring first specifically to Figures 7, 8 and 9, the improved roll coater is seen comprising a chassis generally indicated at 90 and having front walls 90a and rear wall 90b held together in spaced relationship by longitudinal bars 94. The edges 96 of the chassis front and rear walls 90a and 90b provide mounting surfaces 96 for receiving a plurality of source target assemblies 98. Six such assemblies are included in the preferred embodiment. Three, 98a, 98b and 98c, are located about the upper chill drum 10 and three, 98d, 98e and 98f, are located about the lower chill drum 12. Each of the source target assemblies, as best seen in Figures 9 and 10 include a target body 100 composed of a material suitable for sputtering as in this embodiment or suitable for other vacuum coating procedure. The specific source target material can vary widely and each of the source targets can actually be different materials to provide different coating layers on the substrate. Typical sputtering materials are chromium, stainless steel, titanium, aluminum, copper, brass, tungsten, molybdenum, gold, silver, tantalum and various alloys and compounds. The target assemblies (as is best seen in Figure 7) are cooled by means of cooling fluid inlets 101 and outlets 103. The inlets and outlets may also be used for circulating a heating fluid. The target assemblies also include a metal shields 102 of a suitable material such as 316 ss. Shields 102 are shaped similarly overall to the source targets 100. In this embodiment the overall shape is rectangular and as best seen in Figure 7 has side walls 102a which receive and envelope or enclose target body 100 to confine its deposition only to the immediate area of the exposed substrate under the assembly. Additional isolation is provided by isolation barriers 104 which are appropriately positioned and arranged within the chassis 90 as shown in the Figures to provide in effect six separated and isolated coating chambers. Only one elongated barrier wall is shown in Figure 8 although another is in fact included in the chassis in a symmetrical position. This overall arrangement localizes the coating at each target/shield area. Each of the shields 102 also includes cooling means. Input 106 and output 108 conduits are included for this purpose. Lastly, each of the target assemblies 98 include a pair of shim pieces 110 as best seen at assembly 98b in Figure 7 and assembly 98a in Figure 8. Shims 110 are placed between source target body 100 and shield 102 as shown and control the relative position of the source target body with respect to the surface of its associated chill drum and the substrate to be coated which is carried thereon. The distance between the target body and the surface of the chill drum is controlled by the thickness of shims 110. The angle of incidence of the target body with respect to the surface of the associated chill drum is controlled by the shape of shims 110. The target assemblies 98 are held together and fastened to the surfaces 96 of the chassis 90 by means of bolts 112 which are received in threaded holes 114. Chassis 90 walls 90a and 90b may include various openings or windows 116 located in the coating areas to facilitate observation of those areas when the system is in operation. The cooling system arrangement of the target shield assemblies 98 (98a specifically) and the chill drums 10 and 12 can best be understood with reference to Figure 10 which is a front elevational view of chassis 90. The cooling inlet arrangement is shown in the Figure on the front side of the roll coater, as shown. Not shown but identically arranged on the unseen backside or rear is the cooling outlet arrangement. Only the coolant inlet arrangement is shown for the sake of simplicity. It includes for the shields a conduit manifold 118 having couplers 124 connected to shield inlets 106 by means of conduits 126 (only one shown in Fig. 10 on the upper left shield) . The source targets, as shown for the upper left are at 98a in Fig. 12 are separated from the shield cooling system. The inlet of each target 101 is contacted by a conductive conduit such as copper tubing 122 which also serves to carry electrical power to each target. The outlet side may be a non-conductive tubing such as Teflon. Similarly, chill drums 10 and 12 are connected to conduits as shown at 128 in Figure 10 by means of fittings 128a and in more detail in Figure 11. As seen in Figure 11 an appropriate rotary connection 128a generally indicated at 130 and seals 132 within a hub 134 or the like may be used. A flanged compression coupling flare 136 may also be used, as shown, with a suitable clamp 138. Suitable electrical insulator means 140 is also included. Chill drum outlets are shown at 128b in Figure 7. As previously described in earlier Figures , the roll coater includes a feed roll 16 which carries a supply of flexible substrate 14 , idler/ drive roll arrangements generally indicated at 18 and 20 and a take-up roll 22. Feed roll 16 is designed to mount on drive connector mounts 142a and 142b, 142a being adapted as shown in Figure 7 to be connected to a source of rotary drive power or rotating roll 16. Take-up roll 22 is similarly mounted on drive connector mounts , 144a being shown in Figure 7 and being similar to 142a . Idler/drive roll arrangement 18 may include idler roller 146, roller 147 which senses tension of the flexible substrate 14, and drive roller 148 which functions to move substrate 16 through frictional surface engagement when tensioned and to thereby drive chiller drums 10 and 12. Tension is sensed by means of a tension sensor control system (not shown) consisting of two magnetic clutches, two "Dancer-Follower" position sensors and two web tension controllers such as the Magpower DF-C system by Magnetic Power Systems, St. Louis, Missouri. Idler/drive roll arrangement 22 also includes a roller 150 which senses tension of substrate 14 as described above. Roll coater chassis 90 is shown in Figure 7 carried by a transport dolly 152 having a base 153 on caster wheels 154 thereby enabling roll coater 90 to be moved about when outside the vacuum chamber 26. The top of base 153 includes a pair of rails 155 on rail supports 156 which are adjustable as to height by four screw adjustment mounts 157. Rails 155 terminate at one end in male pin rail connectors 158 adapted for connection to a set of rails described hereinbelow which are inside vacuum chamber 26. Chassis 90 is carried on rails 155 by four trolley wheels 160 which ride on the rails. With the arrangement described above transport dolly 152 may be wheeled to the open vacuum chamber 26 shown in Figure 12. Rails 155 may be connected to rails 162 by inserting mail connector pins 158 into female rail connectors 163 after which the roll coater may be transferred from the dolly into the vacuum chamber by rolling it on the rails. Additional rails 162 are supported on rollers 161 inside the lip 169 of the vacuum chamber. Rails 162 form part of a support arrangement in vacuum chamber 26 including a spreader 164, a stand 165 and a cross member 166, all of which are fastened together securely. Shuttle 166 is supported on member 167 and carries rails 162 such that they protrude over the lip of the chamber opening as shown in Fig. 12. The roll coater on the dolley may be rolled up to rails 162 and transferred thereto at which time various operating connections in the chamber are made to the roll coater. The operating connections in the chamber are made through a series of feedthroughs arranged in rear bulkhead 168 and shown schematically in Figures 12 and 13 as a series of arcuately arranged circles. For example, with reference to Figures 12-14, a series of shafts are shown extending through rear bulkhead 168 forwardly into chamber 26. These shafts are each positioned to mate within a specific operating device on the roll coater when it is moved into chamber 26 to engage the shafts. Specifically, shaft 170 operably engages fee roll connector 142a. Shaft 172 operably engages connector 149 on drive roller 148. Shaft 173 operably engages roller 147. Shaft 174 operably engages roller 150. Shaft 175 operably engages take-up roll 22. Shafts 170 and 175 are driven by electric motors 176 and 177, respectively, through belt and pulley arrangements shown schematically in Figures 13 and 14. Likewise, drive shaft 172 is driven by stepper motor 13 and a belt/pulley arrangement shown schematically in Figures 13 and 14. Coolant connections 178 and 179 (Fig. 12) also extend forwardly through rear bulkhead 168 for appropriate connection to the roll coater inlets 120 and 128. When the chamber door is closed, the protruding ends of rails 162 and received therein. This completes the description of the preferred and alternate embodiments of the invention. Those skilled in the art may recognize other equivalents to the specific embodiment described herein which equivalents are intended to be encompassed by the claims attached hereto.

Claims

WHAT IS CLAIMED IS: 1. A roll coater for deposition coating, comprising: a pair of rotatable chill drums which are oppositely positioned one above the other and relative to each other such that a flexible substrate to be coated lays flat on surface portions of each of the drums as the substrate moves over the drums; a feed roll positioned to one side of the drums for supplying a length of flexible substrate to be run over the drums and coated; a take-up roll positioned to the other side of the drums for receiving the coated substrate after it has run over the chill drums; drive means for moving the substrate from the feed roll and over the chill drums; a roll of flexible substrate carried on the feed roll and extending to the lower portion of the upper drum on the side thereof on which the feed roll is positioned, the substrate extending upwardly, over the top of the top drum, down the other side of the top drum and crossing the space between the top and lower drum to extend downwardly over the side of the lower drum which the feed roll is positioned, around the bottom of the lower drum and upwardly over the other side of the lower drum and then to the take-up roll whereby the substrate is fed over the top drum in a first direction and is subsequently fed over the lower drum in a second and opposite direction, the drums counter rotating as the substrate moves over them to the take-up roll, opposite sides of the substrate being exposed on the respective drums for being coated as the substrate moves over the drums, and means for positioning a plurality of source targets near each of the drums, to each side and at the top of the top drum and to each side and at the bottom of the lower drum whereby the angle of incidence of the source target surface of each source target is adjustable with respect to that surface portion of the respective drum to which a source target is closest. 2. The roll coater of of claim 1 wherein the chill drums are positioned directly one above the other. 3. The roll coater of claim 1 including means for maintaining an electrical bias on at least one of the chill drums. 4. The roll coater of claim 1 including means for electrically isolating the chill drums from the rest of the roll coater structure. 5. The roll coater of claim 1 including a plurality of source targets disposed about each chill drums for providing multiple layer coatings on the substrate. 6. The roll coater of claim 1 in which the source targets provide different coating materials. 7. The roller coater of claim 1 including shielding means for physically isolating the source targets to prevent cross-deposition and provide discrete boundaries between deposited layers. 8. The roll coater of claim 1 including means for heating and cooling the chill drums. 9. The roll coater of claim 1 in which up to three source targets are included with each chill drum, one to each side and one at the top or bottom, respectively. 10. A roll coater apparatus for use in depositing a coating on a substrate, said Roll-Coater apparatus comprising: (a) two rotatable cylindrical chill drums each having an outer surface with upper, lower and side surface portions, the chill drums arranged in a side by side configuration a predetermined distance apart with the axis of rotation of each chill drum aligned, each chill drum having a feed-in and feed-out side; (b) means for feeding a flexible substrate to the feed-in side of the first chill drum; (c) means for pulling the substrate through the apparatus and taking up coated substrate from the feed-out side of the second chill drum; (d) a flexible substrate to be coated, the substrate running from the feeding means to the feed-in side of the first chill drum, around the side, upper portion, and other side of the chill drum, then running across the space separating the two chill drums to the feed-in side of the second chill drum, said feed-in side being on the same side as the feeding means, the substrate running around the side, lower portion, and other side of the chill drum, then running to the take up means; ^' (e) at least one target by each chill drum arranged a predetermined distance from the substrate movement contacting each chill drum such that the deposition has an angle of incidence substantially perpendicular to the surface of the chill drum; whereby the substrate is coated on both sides as the substrate is pulled through the apparatus, the substrate movement causing the first chill drum to rotate in a first direction, and causing the second chill drum to rotate in an opposite direction. 11. The roll coater of claim 10 including means for adjustably mounting the source targets whereby their distance from the substrate may be varied. 12. The roll coater of claim 10 including means for adjustably mounting the source targets whereby the angle of incidence may be varied. 13. A roll coater transfer arrangement adapted to provide mobile movement of a roll coater into and out of a vacuum chamber, comprising in combination: a roll coater chassis including a set of trolley wheels for rolling the chassis back and forth; a transportation dolly including a base, wheels attached to the base and a pair of spaced rails on the base for receiving the wheels of the chassis thereon, the rails being adapted for connection to a pair of mating rails, and support means carrying a pair of mating rails, the support means being adapted for installation in a vacuum chamber.