US 3901183 A
An isolation lock for a beam treating chamber includes an evacuable lock having a top entrance closure and a bottom exit closure and adapted to receive a wafer therein. The bottom closure being operable to an inclined position in alignment with an inclined receiver whereby to gravity feed said wafer onto the receiver. The receiver includes means to retain said wafer in a fixed position thereon and is movable to dispose the fixed wafer for beam treatment within the chamber.
Description (OCR text may contain errors)
United States Patent 11 1 1111 3,901,183 Wittkower Aug. 26, 1975  WAFER TREATMENT APPARATUS 2.996.038 8/1961 Hunickc 118 50 3,084,779 4/1963 Mladck et a1 198/27 [751 mentor: Andrew Rockport 3,167,167 1 1965 Key 198 26 Mass- 3,260,383 7/1966 Fitz 06mm 214 17 B 3,560,300 2 1971 Eigenmann... 118/50 x  Ass'gnee Extm corporamncloucester 3,714,925 2 1973 Helm 118/49 Mass.
 Filed: Nov. 18, 1974 Appl. N0.: 524,979
Related US. Application Data  Continuation-impart of Scr. No. 369,153, June 12,
 US. Cl ll8/49.l; 198/26; 214/17 B  Int. Cl. C23C 13/08 [581 Field of Search ll8/48-49.5, 118/50, 50.1, 500-503; 198/26, 27; 34/92, 242; 214/17 A, 17 B, 17 C, 17 CA, 18 R  References Cited UNlTED STATES PATENTS 2,516,908 8/1950 Pottlc 118/50 Primary Exarnir'terMorris Kaplan [5 7 ABSTRACT An isolation. lock for a beam treating chamber includes an evacuable lock having a top entrance closure and a bottom exit closure and adapted to receive a wafer therein. The bottom closure being operable to an inclined position in alignment with an inclined receiver whereby to gravity feed said wafer onto the receiver. The receiver includes means to retain said wafer in a fixed position thereon and is movable to dispose the fixed wafer for beam treatment within the chamber.
31 Claims, 16 Drawing Figures PATENTEDAUGEBIQTS SHEET PATENTED AUG 2 6 I975 .SHEET PATENTED mszsms SHEET FIG 5B FIG 5A FIG PATENTED m 3,901 183 SHEET 7 10 I76 I76 I54 I54 I FIG 9 FIG ilo PATENTEDAUGZBIQYS Y 3,901,183
SHEET 1o 10 FIG l5 WAFER TREATMENT APPARATUS CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of my previous patent application Ser. No. 369,153, filed June 12, 1973, now abandoned for Wafer Treatment Apparatus.
BACKGROUND OF THE INVENTION This invention relates to apparatus for treating discrete items in a protected environment with one or more treatment beams and, in important aspects, to apparatus for the implantation of ions in a semiconductor wafer, the implantation occurring in a vacuum. (As used herein beam" refers to a flow of neutral or charged particles (e.g., electrons, molecules, molecule clusters, etc.) or electromagnetic quanta whether or not collimated or even exhibiting mean flow direction. Thus, a beam will be understood to include sputtering, vacuum depositing, and other techniques as well as more highly directional conventional beams.)
A number of competing goals are typically encountered in the design of such apparatus. Thus, while it is desirable to keep the apparatus simple and reliable in construction, it is also desirable to have it precise in operation so as not to damage fragile and expensive semiconductor wafers and also to minimize the labor requirements in feeding wafers to the apparatus and withdrawing treated wafers therefrom. This latter goal is important, of course, to reduce the cost of treating such wafers, but also to minimize the likelihood of contami nation of the pre-cleaned wafers by contact with a human being.
Furthermore, in the treatment of various items in a vacuum, and particularly in the implantation of ions in a semiconductor wafer, it is highly desirable that the items assume a particular orientation with respect to other elements of the apparatus during the actual treat ment of the item.
SUMMARY OF THE INVENTION In view of the foregoing, it is a principal object of the present invention to provide apparatus for the processing of discrete items in a protected environment which requires a minimum of human labor, can process the items in a rapid and precise manner, can accept items on a continuous basis (e.g., such as items fed from a conveyor), and can precisely orient the items with re spect to other portions of the apparatus.
According to the invention apparatus for processing discrete wafer-form items in a protected environment comprises a chamber and an isolation lock through which the item moves in a path between outside and inside the chamber. The isolation lock includes a casing and a bottom closure member across the path, the member defining an item-receiving surface for items when the member is in a closed position. The member is movable downwardly to an open position where the item'receiving surface resides at an angle to the horizontal to define a slide surface for sliding, guided grav-' ity movement of an item from the lock to a receiver. The apparatus also includes means for producing a treatment beam in the chamber. The receiver is movable to a position which exposes a waferform item retained thereon to the beam. Preferably, the chamber is a vacuum chamber, and means are provided for evacu ating the lock; the lock is at the entry of the chamber, the receiver comprising a wafer holder within the chamber, the member being movable into the interior of said chamber to a position aligned with the wafer holder therebelow, adapted to slidably guide waferform items into the wafer holder; the wafer holder comprises a member rotatable from a wafer receiving position to an exposure position and also from the exposure position to a'downwardly sloping discharging position in which it defines a slide surface for guided gravity movement of an item; an exit lock is provided (the bottom closure member being constructed as the firstmentioned closure) which is adapted to receive items from the wafer holder, and, upon opening, to discharge the items to a receiver outside the chamber; and each bottom closure member comprises either a swingable door or a slidable movable piston.
In another aspect of the invention such apparatus may be combined with a pair of conveyors to achieve a fully automated wafer treatment system. One conveyor is arranged to deliver wafer-form items to the bottom closure member of the entry lock, and the other arranged to convey away wafer-form items received from the bottom closure member of the exit lock.
The invention also features, in such apparatus a wafer holder which includes means for rotating a wafer-form item in its own plane to orient said items relative to an exposure position. For use with round waferform items having a predetermined flat edge at one point on the periphery, the items designed to be oriented in the wafer holder relative to that flat, the wafer holder comprises three support points arranged to supportingly receive the round periphery of the items, the middle of the points defined by a rotary drive element adapted to so apply rotative force to the edge of the items until arrival thereat of the flat,
The invention also features improvements in apparatus for processing discrete wafer-form items in a protected environment, the apparatus including a vacuum chamber, means for producing a treatment beam in the chamber, positioning means for disposing an item for exposure to the beam, delivery means for delivering the item to the positioning means, and receiver means for receiving the item from the positioning means after the exposure. According to the present invention, the positioning means comprise a wafer holder having structure defining the plane of the item disposed thereon, and means for swinging the holder to predetermined orientations with respect to a substantially horizontal axis, the axis being-positioned below the delivery means and above the receiver means. That plane, in a first holder orientation, is upwardly sloped with respect to that horizontal axis and is disposed to receive the item by sliding guided gravity movement from the delivery means, that plane, in a second holder orientation, is downwardly sloped with respect to that horizontal axis and is disposed to deliver the item to the receiver means by a sliding guided gravity movement.
BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features, and advantages of the invention will appear from the following description of-particular preferred embodiments, taken together with the accompanying drawings. In the drawings:
FIG. I is a somewhat schematic diagram illustrating the operation of apparatus constructed according to the present invention;
FIG. 2 is a partially broken away side elevation of a preferred embodiment of apparatus constructed according to the invention;
FIG. 3 is a plan view of the apparatus of FIG. 2;
FIG. 4 is an end view of the apparatus of FIG. 2;
FIGS. 5A and 5B and FIG. 6 are views of alternative wafer holders constructed according to the present invention for use in the apparatus of FIGS. 1 or 2;
FIG. 7 is a partially broken away side elevation of another embodiment of apparatus constructed according to the present invention;
FIG. 8 is a sectional view of the entrance lock of the apparatus of FIG. 7; I
FIGS. 9 and 10 illustrate two steps in the operation of the lock of FIG. 8; I
FIGS. 11, 12, and 13 are schematic diagrams illustrating alternative apparatus arrangements, according to the present invention, which provide for multiple treatments of wafers within a single vacuum chamber;
FIG. 14 is a schematic drawing illustrating an embodiment which provides for preand post-treatment conditioning within the vacuum chamber of the apparatus; and
FIG. 15' is a fragmentary perspective view of a portionof the apparatus of FIG. 2 or FIG. 7.
DETAILED DESCRIPTION OF PARTICULAR PREFERRED EMBODIMENTS FIG. 1 is a greatly simplified, somewhat schematic illustration of a system constructed according to the present invention for implanting ions in semiconductor wafers in a vacuum. In FIG. 1 the ion beam is represented by a cone 10 emanating from an ion source and scanner l2 and terminating in the target plane which may be taken as the open end 14 of evacuated tube 16 (i.e., the Faraday cage) within which the ion source and beam are disposed. The apparatus includes an upper vacuum lock 18 for achieving entry of the wafers 20 into the vacuum chamber and a lower vacuum lock 22 for removing the implanted wafers from the vacuum chamber. The upper vacuum lock includes upper and lower closure members in the form of doors 24, 26 each mounted for swinging motion adjacent the opening 28 into the vacuum chamber itself. Each door is movable between a first position in which it makes a substantially air-tight seal around the opening 28 and a second position in which one end of the door is swung away from the opening 28.
The wafers 20 are delivered to the vacuum lock 18 on a conveyor which approaches the vacuum lock from the direction toward which the door 24 opens.
With the door 26 closed and the door 24 opened, a wafer riding on the conveyor 30 will slide into the opening 28 and rest on the upper surface of door 26. At that point sequencing and control unit 43 causes door 24 to close and the space 28 (the space between doors 24 and 26 in their closed positions) to be connected to a roughing vacuum pump (not shown). The pump evacuates this space, preferably to a vacuum of approximately 10 microns. At that time, the lower door 26 is caused to swing to asecond position (i.e., the open position shown in FIG. 1) so that the wafer can slide under the influence of gravity onto wafer holder or receiver 32 which is aligned at that time to have a receiving surface disposed in the plane of the surface on door 26 that the wafer is resting upon. Means are provided to maintain the wafer 20 on the unit 32 during its subsequent motion (as further described below). The holder 32 is then caused to rotate substantially a vertical orientation closing off the end of tube 16 while door 26 closes once again. At that time the ion beam is activated to accomplish the implantation of ions in the wafer 20. Valving (not shown) connects the space 28 to the ambient to permit upper door 24 to open so that the vacuum lock is ready to receive the next wafer.
On completion of this implantation, unit 32 is caused to swing to a third position which is indicated at 34 in FIG. 1. In this position the surface supporting the wafer 20 is again angled with respect to the vertical and aligned so that the wafer can slide into the removal opening 36 which is exposed by the open upper door 38 of the lower vacuum lock 22. After the wafer has been deposited in the opening 36, the upper door 38 closes and a valve (not shown) is caused to operate connecting the base 36 with the ambient to relieve the vacuum therein. Then the lower door 40 swings open to an appropriate angle such that the wafer 22 may slide on the upper surface of that door to be ultimately deposited on a removal conveyor 42. Door 40 then closes and the space between doors 38 and 40 is reevacuated to about 10 microns. The sequencing and control unit 43 controls the movements of the doors and the wafer holder as well as the operation of the valves which evacuate and pressurize the vacuum locks.
A preferred embodiment is shown in more detail in FIGS. 2-4. The tube 16 through which the ion beam travels (as indicated by arrow 44 in FIG. 2) communicates with a vacuum chamber 46 defined by a casing 48. The upper vacuum lock 18 in the upper casing wall comprises opening 50 in the wall, a first door 52 exterior of the chamber 46 and a second door 54 interior of the chamber 46. Each door overlaps the casing 48 so as to, in its closed position, form a substantially airtight, face-to-face seal with the casing. The upper door 52 is connected to a rotatable shaft 56 by ribs 58 which are secured to both the door and the shaft. The shaft 56 is supported for rotation in supports 60 which in turn are secured to the upper surface of casing 48. A rod 62 is secured to the shaft 56 in the center thereof and forms a part of a linkage which causes movement of the door 52, in a rotational fashion, between open and closed positions. As shown in FIG. 4, rod 62 is pivotally secured to the piston 51 of a vertically mounted pneumatic cylinder 53. Vertical motion of piston 51 thus causes the desired rotation of rod 62 and shaft 56.
The lower door 54 of upper vacuum lock 18 includes an upper planar wafer-receiving surface 64. The door 54 is supported by ribs 66 for movement about an axis 68 between a first or closed position as shown in FIG. 2 and an open, angled position which is indicated in a broken line representation in FIG. 2. This motion is effected by motion of a rod 70 which moves a portion of pneumatic valve actuator (the remainder not shown) and which enters the chamber 46 through one end 72 thereof. (The structure which accomplishes this, and its operation, is identical to that which moves the upper, interior door of the exit vacuum lock 22, all as described below. To simplify the drawing, this structure has been omitted on door 54.)
A wafer receiver or holder 74 is disposed within the chamber 46 and is mounted for rotation on a shaft 76. The device 74 is in the general form of a receiving tray for accepting a wafer which slides under the influence of gravity from surface 64 of door 54. A planar surface 78 is the actual surface which receives the wafer. The device 74 is rotatable about the axis of shaft 76 so as to be positionable in at least three separate positions. The first position is indicated by reference line X (see FIG. 2), the second position by reference line Y, and the third position by reference line Z. In the first position the surface 78 is substantially aligned with surface 64 of the door 54 when the door is open. In the second position the surface 78 is generally upright and dis posed in the open end of tube 16 within the chamber 46. (As shown in FIG. 2, however, it is often desirable that in this position the wafer be not precisely upright but angled with respect to the vertical at an angle of about 7. As is well known in the art, such angling is often desirable to prevent a phenomenon as channeling which can occur during the implantation of ions in a crystalline lattice.) In the third position, indicated by reference line Z, the surface 78 is angled with respect to the vertical such that a wafer supported on surface 78 can slide under the influence of gravity to be received upon the upper surface 80 of a lower door 82 which forms a part of the lower, or wafer-removal, vacuum lock 22. As with the upper vacuum lock, that door 82 overlaps the casing 48 around an opening 84 in the casing to form a face-to-face seal with the casing. Ribs 86 connect the door 82 with a rotatable shaft 88. A rod 90 secured to shaft 88 (see FIG. 4) forms part of a linkage'for a conventional mechanism for rotating the shaft 88 to cause motion of the door 82 between its closed position as illustrated in FIG. 2 and an open position in which the surface 80 is angled with respect to the vertical, as shown by the broken line representation in FIG. 2.
The lower vacuum lock 22 also includes an upper door 92 which overlaps the casing 48 around the open ing 84 to effect a substantially air-tight, face-to-face seal in the closed position of the door, illustrated in FIG. 2. Ribs 94 are secured to both door 94 and a shaft 96 supported for rotation in supports 98 within the chamber 46. Structure 100 projects upwardly from the door 92 and includes an oblong opening 102 which in the closed position of the door is angled with respect to the horizontal. A roller 104 is disposed in the opening 102 and is linked by a rod 106 to a rod 108 which forms a portion of a pneumatic valve actuator (the rest of which is not shown) of conventional design. The motion of rods 106, 108, and roller 104 to the right as viewed in FIG. 2 causes the upward swinging of door 92 from its closed position to the open position shown in broken line form in FIG. 2.
In the open position of door 82 the surface 80 is generally aligned with'the upper end of a guide chute 108 which conducts a wafer from the surface 80 to a conveyor 110 aligned with the lower end of chute 108.
The casing 48 also includes an opening 112 which receives a conduit 114 that is ultimately connected to a vacuum pump (not shown). An opening 116 is provided in the upper surface of casing 48 and is aligned with reference line Y (i.e., the position of the Wafer to be treated in its treatment orientation). Glass viewing disc 115 overlies the opening 116 and is supported in a threaded retainer 120 forming an air-tight seal with resilient seal member 119 which is disposed in a groove which surrounds the opening 116.
The movement of the unit 74 between positions X, Y, and Z is produced by means of a gear 118 which is secured to the shaft 76 exterior of the chamber 46. This is indicated schematically in FIG. 2 and more representationally in FIG. 3. A rack gear 121 engages the gear 1 18 and is itself attached to a rod 122 which is attached to a piston 124 in a pneumatic cylinder 126. Air supply and sequencing control (not shown) of conventional design are provided for the cylinder unit 126.
Simple mechanical stops, of course, are sufficient to achieve precisely the desired locations for the unit 74 in the second and third positions (i.e., the positions identified by reference lines Y and Z For the first position (indicated by reference line X), however, a oneway stop is required. Thus, as the unit 74 is swinging from the second position (reference line Y) to the third position (reference line Z) to discharge an implanted wafer, the position at reference line X must simply be by-passed. After the wafer has been deposited in the removal opening 84 (and upper door 92 has closed to preserve the vacuum within the chamber 46), the unit 74 begins its counterclockwise motion and must stop at its first position (reference line X) to receive the next wafer from surface 64 of door 54. To this end a oneway stop 128, indicated schematically in FIG. 2, is provided adjacent the reference line X. This stop may be at a conventional design; e.g., being spring loaded with a camming surface which forces the stop to retract as the unit 74 passes in a clockwise direction and a stop surface which engages the unit 74 as it approaches in a counterclockwise direction. Conventional sequencing and control apparatus can be employed to move the stop member against the force of the biasing spring after the fresh semiconductor wafer has been deposited on surface 78 so that the unit 74 may then swing to its second position (reference line Y).
Two particularly preferred forms of the wafer receiver or holder 74 are illustrated in FIGS. 5A and 5B, and 6. Referring to FIGS. 5A and 5B, the holder 74 comprises a planar rigid member 123 for receiving a wafer 20. A pair of V support stops 127 are disposed on the upper surface of member 123 adjacent the wafer 20 and spaced from each other approximately around the periphery of the wafer 20. The wafers periphery is thus held by the relieved area beneath the support stops 127.
In FIG. 6, the unit 74 is generally in the form of a tray including a surface 78 for receiving a wafer 20 and an upstanding lip 130 disposed around three sides of the surface 78. Three retainer members 134, 136, 138 are raised above the surface 78 approximately the thickness of the wafer 20 and are located to partially overlie the peripheral portions of a wafer 20 which is properly located on the surface 7 8. Each of the members 134, 136 is rigidly secured to the surface 78 and is undercut (as indicated at 140, 142) to receive the wafer 20. The member 138 is a disc mounted for rotation about an axis 144 and is located such that the periphery of the disc 138 engages the periphery of the wafer 20.
It will be apparent to those skilled in the art that the operation of the unit as shown in FIG. 5B is such that a wafer 20 may be supported in a plane (i.e., the plane of surface 78), that plane rotated to a predetermined orientation (as by rotation of the unit 74 about shaft 76 between reference lines X and Y of FIG. 2), and the wafer 20 itself may be rotated in that plane to achieve a preferred orientation of the crystalline lattice of the wafer. This latter rotation is achieved by the disc 138 which, as it rotates, causes a rotation of the wafer 20. Such rotation of die wafer 20 continues until a flat 146 (such as is often conventionally provided on the periphery of a otherwise circular wafer) reaches a rotational orientation of wafer there is no longer physical contact between the disc 138 and the wafer and rotation of the wafer ceases. Thus, by rotation of the unit 74 about the axis 76 to a preferred orientation (e.g., the 7 orientation with respect to the ion beam shown in FIG. 2) and the rotation of the wafer 20 in the plane of surface 78, preferred orientations of two axes of the crystalline lattice with respect to the ion beam can be achieved.
FIG. 7 is a view similar to FIG. 2 of another embodiment of an ion implantation system constructed in accordance with the present invention. The present description will concern the entrance and exit isolation locks 148, 150 since the remainder of the apparatus is substantially identical to that of FIG. 2 and thus has already been described. As shown in FIG. 7, a waferform item 20 is delivered by conveyor to a sloped guide 152 aligned with an entrance aperture 154 of the entry isolation lock 148. The lock as a whole is tilted, and oriented with respect to guide 152, such that the item 20 will slide under the influence of gravity through the slot 154 and into the interior of lock 148. An outlet slot 156 of the lock 148 is aligned with an opening 158 in the casing 48 which defines the vacuum chamber 46. This opening 158 is aligned with the wafer receiver or holder 74 when that holder is in the position indicated at X in FIG. 7.
The exit isolation lock 150 includes an entrance slot 160 aligned with opening 162 in the casing 48, the latter positioned to be aligned with the wafer holder 74 when it resides in the wafer discharge position Z shown in FIG. 7. An outlet slot 164 of the exit isolation lock 150 is aligned with guide or chute 108 which transfers items 20 from the lock 150 to a conveyor 110.
FIG. 8 illustrates the internal construction of the lock 148. (The construction of lock 150 would be substantially a mirror-image of the lock 148, as will be apparent to those skilled in the art.) 1
As will be seen from FIG. 8, the lock 148 comprise upper and lower pistons 166, 168 mounted within a generally hollow casing 170. Each piston includes an integral pressure plate 172, 174 and a head 176, 178. The casing 170 is formed from a plurality of coaxial parts so as to facilitate manufacture and assembly and provides internal cavities 180, 182 within which pressure plates 172, 174, respectively, are disposed and a larger cavity 184 within which the piston heads 176, I78 are disposed. An annular flange 186 on casing member 188 adjacent cavity 184 provides stop surfaces defining limits of travel of the pistons and, by means of annular sealing members 190, 192, provides for an air tight seal when the respective piston head 176, 178 abuts the flange 186. The upper surface 194 of the lower piston 158 forms a movable item-receiving surface. (It should be recalled that the entire lock 148 of FIG. 8 is supported on the casing 48 of the apparatus in a tilted orientation such that the surface 194 will be sloped with respect to the horizontal.) To separate high vacuum, high pressure, and intermediate pressure portions of the vacuum lock 148, circumferential resilient sealing members 195 are disposed around the periphery of the pressure plate and the piston shaft, both above and below the pressure plate, for each of the pistons 166, 168. Air channels 196, 196a are provided in casing members 198, 198a and communicate with the cavity 180 above and below, respectively, the pressure plate 172. Similarly, air passages 200, 200a are provided in casing members 202, 202a and communicate with cavity 182 below and above respectively, the pressure plate 174. Each of the passages 196, 196a, 200, 200a communicates with an exterior conduit member 204 which in turn is connected to an air pressure supply and control unit 206.
An air passage 208 is also provided in casing member 188 and communicates with the volume of cavity 184 disposed between the piston heads 176, 178. The passage 208 is connected, via conduit member 210, to a vacuum pump 212. An air tight bellows 214 is disposed around the central shaft of piston 168 and is secured at its opposite ends, in an air tight seal, to the piston head 174 and to a flange portion 216 of the casing member 202a. A pair of resilient bumpers 218, 220 are provided adjacent the item-receiving surface 194 at the input slot 154 and output slot 156 sides of the lock respectively. The member 218 is secured to the piston head 178 and has a portion 222 aligned with surface 192 and a portion 224, radially outward therefrom, which projects upwardly from surface 194. The member 220 is secured to the flange portion 186 of the casing member 188. The individual elements forming the casing 170 of the vacuum lock 148 can be secured together in any conventional fashion.
The operation of the vacuum lock 148 may be described with reference to FIGS. 8-10. The air supply and control unit 206 is conventionally constructed to deliver high pressure to the respective air passages 196, 196a, 200, 200a in accordance with a predetermined sequence to operate the pistons 166, 168 in the manner to be described. Since the sequence is continuous and repetitive, the following description will assume an initial starting point for the sequence as shown in FIG. 9.
With high pressure air supplied to passages 196a and 200 both pistons will be in their uppermost position and thus the entrance slot 154 will not be blocked by the piston head 176 and the high vacuum in the chamber 46 (which communicates with the exit slot 156) will be protected by the compressional seal effected by the pisto'n head 178 bearing against the resilient seal member 192. In this configuration of the pistons, a wafer-form item 20 is gravitationally delivered to entrance slot 154 I and it slides into the lock 148 to rest upon the itemreceiving surface 194 of lower piston 168. The resilient member 218 forms a smooth and non-abrasive surface over which the item 20 slides to reach its position of rest on thesurface 194 and the member 220 provides a resilient and non-abrasive stop surface which the item 20 will bear against.
With the item 20 disposed on the surface 194, the unit 206 disconnects the high pressure from the passage 196a and connects it to the passage 196, thus forcing the piston 166 downwardly such that seal engages the flange 186. In this orientation of the pistons, the volume within which the item 20 is disposed (the volume of cavity 184 between the piston heads 176, 178) is isolated by the action of seal members 190, 192 and thus becomes evacuated by the action of the continuously operating vacuum pump 212. After this evacuation, the unit 206 interrupts the high pressure connected to passage 200 and connects high pressure to the passage 2000 thereby forcing a piston 168 to its lower position, as is illustrated in FIG. 10. In this position, the surface 194 of piston 168 will be positioned relative to the exit slot 156 such as to permit guided sliding motion under the influence of gravity of the item 20 from the surface 194 through the exit slot 156 and on to the surface 78 of holder 74 (see FIG. 7). After the item 20 has left the lock 148, the unit 206 switches the high pressure air from passage 200a back to the passage 200 thereby achieving the piston orientation shown in FIG. 8. The unit 206 then transfers the high pressure from air passage 196 to air passage 196a and drives the upper piston 166 to its upper position illustrated in FIG. 9 for a resumption of the cycle just described.
The portion of cavity 184 below piston head 178 will be at high vacuum conditions at all times during the operation cycle of the lock 148. The portion of cavity 182 above the pressure plate 174, on the other hand, will sequentially experience high pressure conditions. With this arrangement, it would be difficult to maintain the required isolation of high pressure from high vacuum solely by means of sliding seal 195 around the shaft of piston 168 above pressure plate 174. The addition of bellows 214, therefore, provides the required isolation of the high pressure from the high vacuum.
FIGS. 1l14 illustrate embodiments in which waferform items may receive plural treatments within a vacuum chamber. In FIG. 11, which corresponds substan tially to the view of FIG. 1, there are a pair of horizontally aligned tubes 16, 16a for delivering beams generated from beam sources 12, 12a to the target plane of the open ends 14, 14a of the tubes. The entrance and exit vacuum locks 18 and 22 operate as previously described, as do the wafer holders or receivers 32, 32a. In the embodiment of FIG. 11, however, a conveyor 218 is disposed to receive on its upper length a wafer discharged from the holder 32 when in its downwardly sloping wafer discharge position Z. The direction of travel of the item 20 on the conveyor is both horizontal in the direction of the second tube 16a and upward as indicated by sloping portion 220 of the conveyor 218. The discharge end 222 of the conveyor is positioned at substantially the same elevation as the entrance lock 18 and at a lateral position adjacent the second tube 16a and wafer holder 320. A wafer guide structure 224 which includes a wafer support surface 226 is disposed adjacent the discharge end 222 of the conveyor and receives items discharged from the conveyor. The unit 224 changes the orientation of travel of an item by 90 in the horizontal plane and lowers the leading edge thereof for guided sliding gravitational movement onto the wafer holder 320 when positioned in its wafer receiving position X. It is thus apparent that the holders 32, 32a serve as wafers supports which receive wafers, move them to a treatment position (adjacent the open end 14, 14a of the tube), and then move them to a discharge position. The wafers are discharged from support 32 to conveyor 21 8 and from support 320 to the exit lock 22.
FIGS. 12 and 13 are schematic illustrations of multiple-treatment machines in which the treatment beams are vertically rather than horizontally aligned. Each of these embodiments, once again, for simplicity includes only two different treatment beams. In each embodiment there are a pair of receivers 32, 32a which function substantially as described above with reference to both FIGS. 1 and 11. In the embodiment of FIG. 12, by
providing beams 44, 44a which travel to the treatment region from opposite directions, the second wafer support 32a actually becomes the receiver which receives an item directly from the support 32 when the support 32 is in the item discharge position Z. In the embodiment of FIG. 13, a rotary receiver 228 is provided for step-wise motion about an axis 230 and includes a plurality of integral item receiving portions 232. With each step in the motion of the receiver 228, one of the members 232 will be aligned for receiving an item from the first support member 32 and a second member 232 will be disposed for delivering an item previously deposited thereon to the second support member 32a. In each of the embodiments of FIGS. 12 and 13 the appropriate item-receiving surface of the exit lock 22 forms the receiver downstream of a second support member 32a.
In the embodiment of FIG. 14, the entrance and exit locks 18, 22 are laterally displaced from the support 32 and the target plane of the beam 44. Upper and lower conveyors 234, 236 are provided and each has its upper length extending between the respective lock 18, 22 and the support 32. The upper length 238 of the upper conveyor 234 is heated by means of heating elements 240 and the upper length 242 of lower conveyor 236 is cooled by means of cooling elements 244. With this arrangement, an item may be pre-conditioned and post-conditioned within the vacuum chamber prior to and subsequent to, respectively, receiving treatment by the beam 44. In the embodiment illustrated, the pretreatment heating provides for annealing of the wafers crystalline lattice during the ion bombardment and the cooling of the treated wafer prior to its return to room temperature. The provision of the conveyors 232, 236, or equivalent means, intermediate the locks 18, 22 and the support 32 permit a relatively slow and uniform heating and cooling of the items without severely limiting the rate at which items are treated by the beam 44 (since many items may simultaneously be positioned at various locations along each conveyor at any given instant).
FIG. 15 illustrates one preferred embodiment of a mechanism for achieving the step-wise swinging motion of the wafer-holder 74 between the three positions illustrated in FIGS. 2 and 7. In FIG. 15, the wafer holder 74 is shown very schematically and is rigidly secured to a shaft 246 which passes through the casing 48 in a conventional air-tight rotational seal 248. Exterior of the vacuum chamber the shaft 246 is secured for rotation with a member 250 which has a pair of integral posts 252 projecting radially therefrom and which includes stop surfaces 254 adjacent the post 252 at a predetermined distance from the axis of shaft 246. Slide members 256 each have an opening therethrough for receiving one of the rods 252. Springs 258 are disposed around the rods between the slide members 256 and an upper rigid support 260. A rod 262 disposed parallel to the shaft 246 links the slide members 256.
A pair of parallel linking arms 264 are pivotally secured to the rod 262 at one end and pivotally secured to a drive arm 266 at the other end. The drive arm 266 extends from the link arms 264 to a drive shaft 268 to which it is secured for rotation. The drive shaft 268 is parallel to the shaft 246 and is in turn secured for rotation with a geneva wheel 270 of conventional construction. A drive wheel 272 is mounted adjacent the geneva wheel 270 and is driven by a motor 274. A curved cam surface 276 secured to the drive wheel 272 is disposed to engage mating curve surfaces 278 of the geneva wheel. Drive pin 280 also secured to drive wheel 272 is disposed to engage, at the appropriate point in the rotation of the drive wheel 272, slots 282 of the geneva wheel 270. A counter-switch 284 is disposed to be activated by the pin 280 once during each revolution of the drive wheel 272 and is connected in a conventional fashion (not shown) to reverse the direction of rotation of the motor 274 after a predetermined count has been achieved.
A cam member 286 having an upper cam surface 288 is supported to engage the under surfaces of link arms 264 adjacent their pivotal connection with rod 262. The distance of the cam surface 288 from the axis of shaft 246 is adjustable by means of adjustments through 290 which is supported in a structural member 292 of the apparatus.
In the operation of the mechanism illustrated in FIG. 15 we may consider as a starting orientation that orientation in which the holder 74 is in the wafer discharge position indicated at Z. The motor 274 is then actuated to drive the drive wheel 272 in a counterclockwise sense as viewed in FIG. 15. The engagement of arcuate cam surface 276 with a mating surface 278 of the geneva wheel 270 maintains the geneva wheel, and thus the remainder of the mechanism, in a fixed rotational orientation for a period of time determined by the portion of a full circle over which the arcuate surface 276 extends and the rate at which the wheel 272 is driven. As the surface 276 is about to disengage the particular surface 278 on the geneva wheel 270, the rod 280 engages the next slot 282 of the geneva wheel and, with the continued rotation of the drive wheel, produces an incremental clockwise rotation of the geneva wheel 270 such that the next arcuate surface 278 thereof will be positioned for engagement with the surface 276 on the drive wheel. This rotation is transmitted by rod 268 to the drive arm 266. The link arms 264 transmit this same rotation to the member 250 and, thus, ultimately to the shaft 246 and the wafer holder 74. The wafer holder 74 will then be in the position X for receiving a fresh wafer. In one preferred embodiment the step-wise displacement of the geneva wheel 270, and thus the angular displacement of the wafer holder 274 between the positions Z and X, is 72. In this same preferred embodiment, however, the angular displacement of the wafer holder between the positions X and Y is of the order of 50. In order to retain the mechanical simplicity of a symmetrical geneva wheel 270, the cam member 286 has been provided to converge the next incremental 72 rotation of the geneva wheel 270 into a lesser portion of the wafer holder 74. Thus, the surface 288 is positioned such that during the next rotation of the geneva wheel the under surfaces of link arms 264 will bearagainst the cam surface 288 and will be forced upward thus moving slides 256 upwardly on the rods 252 against the force of biasing springs 258. This will effectively increase the length of the arm which is parallel to the arm 266 in the parallelogram linkage illustrated. This arm consists of the member 250 and the portions of the rods 252 below the location of the cross-rod 262. The upward motion of the rod 262 produced by the cam surface 288, therefore, lenghthens this arm of the linkage during the second incremental motion of the geneva wheel and thereby reduces the magnitude of the rotation produced in the shaft 246 and the holder 74. The adjustment screw 290 permits the small changes in the placement of the cam surface 288 and thus provides for a range of angles between the holder orientations at positions X and Y by this very easy adjustment. In one preferred embodiment, this range is from 44 to 54 with the 54 value orienting the holder 74 in a substantially vertical orientation. With this arrangement other angles chosen in the range of 44 through 54 will result in a slightly off vertical implantation position Y of the holder 74 such as illustrated in FIGS. 2 and 7.
The preferred vacuum lock construction as illustrated in FIGS. 8-10 is the joint invention of myself and Geoffrey Ryding.
While particular preferred embodiments of the present invention have been described in detail and illustrated in the accompanying drawings, other embodiments are within the scope of the invention and the following claims.
1. Apparatus for processing discrete wafer-form items in a protected environment, including a vacuum chamber and an isolation entry lock through which a said item moves in a path between outside and inside the chamber, said isolation lock including a casing and a bottom closure member across said path, said bottom closure member overlapping a peripheral portion of said casing forming a face-to-face seal therewith, said member defining an item-receiving surface for said item when said member is in a closed position, said member being movable downwardly to an open position where said surface resides at an angle to the horizontal, said member in said open position defining a slide surface for sliding, guided gravity movement of said item from said lock to a receiver, means for producing a treatment beam in said chamber, said receiver including means to retain said wafer form thereon and said receiver being movable to a position exposing said retained wafer-form item to said treatment beam.
2. The apparatus of claim 1 wherein said apparatus is ,an ion implantation device, said treatment beam comprising ions.
3. The apparatus of claim 1 wherein said receiver comprises a wafer holder within said chamber, said bottom closure member in said open position being aligned with said wafer holder therebelow, adapted to slidably guide said waferform item into said wafer holder.
4. The apparatus of claim 3 wherein said wafer holder comprises a rotatable member, rotatable from a wafer receiving position to said exposure position.
5. The apparatus of claim 4 wherein said wafer holder is rotatable from said exposure position to a downwardly sloping discharging position, said holder in said downwardly sloping position defining a slide surface for guided gravity movement of said item from said holder.
6. The apparatus of claim 5 including an exit lock, the bottom closure of said exit lock being constructed also in accordance with claim 1, adapted to receive a said item from said wafer holder, and upon opening, to slidably discharge said item to a receiver outside said chamber.
7. The apparatus of claim 6 including a pair of conveyors, one arranged to deliver wafer-form items to said bottom closure member of said entry lock, and the other arranged to convey away wafer-form' items re- 1 ceived from said bottom closure member of said exit lock. g I h 8. The apparatus of claim 4 wherein said wafer holder includes means for rotating a said .wafer'j-f drml item in itsown plane to orient said item relative to saidexposure position. 1 v
9. The apparatus of Claim form items each having a flat edge at one predeter-' mined point on its periphery, said items designed to be oriented in said wafer holder relative to said flat edge, said wafer holder comprising three support points arranged to supportingly receive the round periphery of said items, the middle of said points defined by a rotary drive element adapted to so apply rotative force to the round periphery of said items until arrival thereat of said flat.
10. The apparatus of claim 3 wherein in said waferreceiving position said wafer holder extends upwardly, at an angle to the vertical for slidably receiving a said item, said wafer holder being rotatable toward the vertical from said receiving position to said exposure position.
11. The apparatus of claim wherein said wafer holder includes a support surface and a pair of V support stops into which said wafer-form items slide into a retained position.
12. The apparatus of claim 11 wherein said wafer holder rotates from its exposure position through said receiving position to a downwardly sloping slidable discharge position at which said wafer-form item slides along said support surface of said wafer holder, out of said V support stops.
13. The apparatus of claim 1 including a movable conveyor arranged to discharge said wafer-form items upon said item receiving surface of said bottom closure member.
14. The apparatus of claim 1 wherein said lock includes a top closure member having an open position enabling entry of said wafer-form item and a closed position overlapping a peripheral portion of said casing forming a face-to-face seal therewith.
15. The apparatus of claim 14 wherein both said top and bottom closure members comprise swingable doors.
16. The apparatus of claim I wherein said bottom closure member comprises a swingable door.
17. Apparatus for processing discrete wafer-form items in a protected environment, including a vacuum chamber, means for producing a treatment beam in said chamber, a waferform item support within said chamber, said support being movable to a position to expose a said wafer-form item to said treatment beam, and an isolation exit lock through which the item moves from said receiver in a path between inside and outside the chamber, said isolation lock including a casing and a bottom closure member across said path said bottom closure member overlapping a peripheral portion of said casing forming a face-to-face seal therewith, said member defining an item-receiving surface for said item when said member is in a closed position, said member being movable downwardly to an open position where said surface resides at an angle to the horizontal, said member in said open position defining a slide surface for sliding, guided gravity movement of said item from said lock to discharge said item to a receiver outside said chamber.
8 foruse with roundvwafer- 18. The apparatus of claim 1,7? wherein said receiver comprises a movable conveyor-adapted to convey waf. er-form items away from saidchamber. v l9. Theapparatus of claim. 17 wherein saidbottom closure member comprises a'doorswingable about a v substantially horizontalaxis v 20. The apparatus of claim 17 wherein cludes a top-closure member'having anopen position enabling entryof said wafenform item and a closedposition overlapping a peripheral portion of said casing forming a face-to-face seal therewith.
21. The apparatus of claim 20 wherein both said top and bottom closure members comprise swingable doors.
22. In apparatus for processing discrete wafer-form items in a protected environment, including a vacuum chamber, means for producing a treatment beam in said chamber, positioning means for disposing a said item for exposure to said beam, delivery means for delivering said item to said positioning means, and receiver means for receiving said item from said positioning means after said exposure thereof to said beam, the improvement wherein said positioning means comprise a wafer holder having structure defining the plane of a said item disposed thereon, means for swinging said holder to predetermined orientations with respect to a substantially horizontal axis which is positioned below said delivery means and above said receiver means, said plane in a first holder orientation being upwardly sloped with respect to said horizontal axis and disposed to receive said item by sliding guided gravity movement from said delivery means, said plane in a second holder orientation being downwardly sloped with respect to said horizontal axis and disposed to deliver said item to said receiver means by a sliding guided gravity movement.
23. The apparatus of claim 22 wherein said beam has a beam axis which is horizontal, said plane in a third holder orientation being within about 10 of the vertical, said item being exposed to said beam when said holder is in said third orientation.
24. The apparatus of claim 23 for use with round wafer-form items each having a flat edge at one predetermined point on its periphery, said items designed to be oriented in said wafer holder relative to said flat edge,
round periphery of said items until arrival thereat of said flat.
25. The apparatus of claim 23 wherein said delivery means comprise an isolation entry lock constructed in accordance with claim 1.
26. The apparatus of claim 23 wherein said receiver means comprise an isolation exit lock constructed in accordance with claim 17.
27. The apparatus of claim 23 wherein said delivery means comprise means for heating said items in said chamber.
28. The apparatus of claim 27 wherein said receiver means comprises means for cooling said item in said chamber.
29. The apparatus of claim 28 wherein said means for heating and said means for cooling comprise conveyors having itembearing surfaces which are, respectively, heated and cooled.
said; ,lock' ini 30. The apparatus of claim 23 further including means for producing a second treatment beam spaced apart from the first mentioned treatment beam and a second positioning means associated with said second treatment beam, the second positioning means holder in its first orientation forming said receiver means.
31. The apparatus of claim 23 further including means for producing a second treatment beam spaced apart from the first mentioned treatment beam and a