Abstract:
A substrate handling system auxiliary to a plasma sputtering system is described. The substrate handling system inserts an unprocessed substrate (e.g., an optical disk), an inner mask, and an outer mask into a loadlock of the sputtering system, and then seals the access opening to the loadlock. The substrate and the masks then are moved to a sputtering chamber where the substrate is coated by sputtering. Subsequently, the substrate handling system moves a processed substrate, and its accompanying inner mask and an outer mask, from the loadlock to an external disk change station, where the processed substrate is removed from the masks, which are still gripped by the substrate handling system. Subsequently, another unprocessed disk is placed on the inner mask and within the outer mask, and the sequence repeats. The substrate handling system only contacts the masks on surfaces thereof that are not subjected to direct sputter deposition, so that the masks can be gripped without causing particulate contamination. A coated surface of the inner mask and outer mask has numerous asperities to trap sputtered material and reduce contamination.

Description:
FIELD OF THE INVENTION 
     This invention relates generally to a system for loading and masking substrates in association with a sputter deposition system. 
     BACKGROUND OF THE INVENTION 
     A conventional optical disk includes a plastic base upon which layers of various materials, such as metals, alloys, or dielectrics, are applied. One method of applying the layers of materials is to use a sputter deposition process. 
     A conventional sputter deposition process is performed using a plasma formed in a vacuum chamber of a sputter deposition system. The plasma is generated by applying electric power to a low pressure gas in the vacuum chamber. Ions originating within the plasma bombard a target formed of a material that is to be deposited on the optical disk. The bombarding ions eject material from the target. The ejected material deposits in a layer on the disk. 
     A conventional sputtering system known as the BALZERS™ BIG SPRINTER™ is believed to include a loadlock between a main vacuum chamber and a disk loader robot. The disk loader robot includes two opposing arms, each of which includes an identical disk holder. An external robot loads an unprocessed optical disk (or other substrate) into the disk holder, and unloads a processed disk from the disk holder. The disk loader robot rotates 180°, and thereby alternatively positions each disk holder at the loadlock and the external robot. 
     During the sputtering operation, the two masks, one known as an inner mask and one as an outer mask, prevent deposition on the central and peripheral portions of the disk, respectively. The inner mask consists of a solid cylindrical body with an annular head attached to one end of the cylindrical body. At the outside of the cylindrical body is a spring mechanism that traps the disk under the annular head. The outer mask is in shape of a flat ring. The disk holders and the carrier arm hold the masks using magnets. The annular head of the inner mask and the surface of the outer mask that faces in the same direction as the sputtered surface of the disk both get a coating of the sputtered material. Magnetized components of the disk holder and the carrier arm contact the sputtered surfaces of the inner and outer masks during loading and handling processes. 
     The sputter-coated inner and outer masks need to be replaced periodically. To do this, the disk loader robot is rotated 90°, thereby placing the disk holder with the masks that are to be replaced at a station dedicated to changing of the masks. 
     There are drawbacks to the above described system that heretofore have not been resolved. First, contacting the sputtered surfaces of the inner and outer masks dislodges sputtered material from the masks, causing particulate contamination on the disk and in the sputtering system. Second, the masks get hot in the vacuum chamber, and have limited opportunities to cool. The hot masks can cause heat damage to the surface of the disk. Third, the use of magnets near the substrate to hold the masks affects the plasma, thereby affecting the uniformity of the film. Fourth, the sputtering system includes a station dedicated to changing of the masks, which consumes valuable space in the machine. 
     SUMMARY OF THE INVENTION 
     The present invention overcomes the aforesaid shortcomings of the prior art, while at the same time providing a high throughput and reliable system for loading, unloading, handling, and masking substrates, such as optical disks, that are to be coated with a sputtered material. The surfaces of the masks that are subjected to direct sputter deposition (i.e., the surfaces that face in the same direction as the coated surface of the substrate) are not handled, which avoids the particulate contamination seen in the prior art system. 
     A sputtering system within the present invention includes a substrate handling system. The substrate handling assembly moves individual unprocessed disks (i.e., disks to be sputter coated) between a disk change station, which is external to the sputtering system, and a loadlock of the sputtering system. The substrate handling assembly moves individual processed disks (i.e., coated disks) between the loadlock and the disk change station. An inner mask and an outer mask accompany each unprocessed disk from the external disk change station, through the sputtering system, and back to the disk change station. 
     The substrate handling system includes one or more arms. At the end of each arm is a disk and mask handling assembly, which is called an “end effector” herein. In one embodiment, the end effector comprises a lid that fits over an access opening to the loadlock. The end effector also includes an inner mask gripper and an outer mask gripper. The inner mask gripper grips the inner mask, and the outer mask gripper grips the outer mask. 
     The inner mask is generally mushroom shaped and fits in a hole in the center portion of the disk. Unlike the prior art inner mask, however, the inner mask of the present invention has a central cylindrical opening that is accessed through the annular head. The inner mask gripper grips the inner mask on a sidewall surface within the cylindrical opening that is not subjected to direct sputter deposition. 
     The outer mask has a hollow vertically-extending body with a central opening that is sized so that a disk can be horizontally disposed within the central opening. A lip at the top of the body superimposes a circumferential portion of the disk. The outer mask gripper grips the outer mask on an outer surface of a vertically-extending sidewall of the body of the outer mask. The gripped surface is not subjected to direct sputter deposition. 
     In one embodiment, the substrate handling system operates by positioning an end effector that is gripping an inner mask and an outer mask at the external disk change station. An unprocessed disk is placed and centered on the inner mask and within outer mask. The substrate handling system moves the end effector to the loadlock, places the unprocessed disk and masks into the loadlock, and seals the access opening to the loadlock with the lid. The end effector pushes the inner mask and outer mask onto a substrate transfer tray positioned in the loadlock. The masks are released by the end effector. The disk and its accompanying inner and outer masks then move on the tray to a sputtering station. Subsequently, after a tray having a processed disk and inner and outer masks is moved into the loadlock, the load lock is vented, and the end effector at the loadlock grips the inner and outer masks on unsputtered surfaces thereof, thereby capturing the processed disk. The substrate handling system moves the end effector to the disk change station, where the processed disk is removed from the inner and outer masks. The cycle subsequently repeats. The design of the system allows high throughput loading and unloading of the disks. 
    
    
     Further features and advantages of the invention will become apparent in view of the drawings and detailed description of the exemplary embodiments. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional side view of a substrate handling system mounted on a sputtering system. 
     FIG. 2 is a simplified top plan view an alternative substrate handling system having three arms. 
     FIG. 3 is a cross-sectional side view of an inner mask. 
     FIG. 4 is a cross-sectional side view of an alternative inner mask. 
     FIG. 5 is a cross-sectional side view of an outer mask. 
     FIG. 6 is a cross-sectional side view of an alternative outer mask. 
     FIG. 7 is a cross-sectional side view of an end effector. 
     FIG. 8 is a perspective view of a rotary actuated outer mask gripper. 
     FIG. 9A is a simplified top plan view of an end effector having four rotary actuated outer mask grippers. 
     FIG. 9B is a simplified top plan view of an end effector having one rotary actuated outer mask gripper and a belt. 
     FIG. 10 is a cross-sectional side view of a portion of an alternative outer mask gripper for use with an outer mask. 
     FIG. 11 is a cross-sectional side view of an end effector having an alternative outer mask gripper. 
     FIGS. 12 a - 12   f  are cross-sectional side views of stages in the operation of substrate handling system. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates portions of an embodiment of a sputtering system within the present invention. Sputtering system  20  sputters layers of material onto the surface of a substrate using a plasma formed in each of several sequential sputtering stations. The disks and their accompanying inner and outer masks move from station to station on a carousel. In the example embodiments described herein, the substrate is an optical disk, but the type of substrate may vary. Other features that may be part of sputtering system  20  are disclosed in a commonly-assigned co-pending U.S. patent application entitled “Magnetic Array for Sputtering System,” Ser. No. 09/499,092, which was filed on Feb. 4, 2000, and is incorporated herein by reference in its entirety. 
     Sputter system  20  includes a loadlock  24  that is used for loading and unloading optical disks. A substrate handling system  21  is mounted to sputtering system  20  adjacent to loadlock  24 . In this embodiment, substrate handling system  21  includes two opposing arms  26  on a shaft  23  that rotates and moves vertically. The number of arms can vary, however, as is discussed below. Handling system  21  loads unprocessed disks into loadlock  24  and unloads processed disks from loadlock  24  through access opening  24 A in loadlock  24 . This loading and unloading process is repeated over and over by handling system  21 . 
     An end effector  28 A is present at the end of one arm  26  of substrate handling system  21 , and an end effector  28 B is attached to the opposing arm  26 . Each end effector  28 A,  28 B includes an inner mask gripper and an outer mask gripper. When handling system  21  rotates, end effectors  28 A and  28 B are moved between loadlock  24  and the external disk change station. A conventional electric motor  23 A rotates and lifts arms  26  and shaft  23 . 
     The number of arms on substrate handling system  21  can vary. At a minimum, handling system  21  has one arm  26  that supports a single end effector. FIG. 2 is a simplified top plan view of alternative handling system  21 - 1  that includes three arms  26 , which respectively support identical end effectors  28 A,  28 B, and  28 C. When such a system is in use, end effector  28 A may be positioned at loadlock  24  (FIG.  1 ), end effector  28 B may be at an external station where processed disks are removed from end effector  28 B, and end effector  28 C may be at an external station where unprocessed disks are placed on end effector  28 C. Rotation of substrate handling system  21 - 1  moves each arm to the next station. The methods used at the external disk change station to remove processed disks from the end effector and to load unprocessed disks onto the end effector may vary. 
     Each end effector  28 A,  28 B of FIG. 1 includes a lid  32  that is located vertically between arm  26  and the inner mask gripper and the outer mask gripper. During the loading and unloading process, lid  32  is placed over opening  24 A in loadlock  24 . When lid  32  is placed over opening  24 A, lid  32  closes the opening and forms a vacuum seal. An O-ring seal may be provided around opening  24 A or on lid  32  to help form the gas tight seal. 
     FIG. 3 is a cross-sectional view of a first embodiment of an inner mask  42 . Inner mask  42  is generally mushroom shaped, and includes an annular head  43  integrally connected to a first end of a vertically-extending body  44 . Body  44  has tapered sides  46  at an opposite second end of body  44 , and an orthogonal portion between head  43  and tapered sides  46 . Body  44  has a hollow cylindrical aperture  45  that begins at the center of annular head  43  and extends vertically into body  44 . While the circumference of aperture  45  is circular in this embodiment, the shape may vary. The width and depth of central aperture  45  are sufficient to allow the gripper fingers of the inner mask gripper to be inserted into aperture  45  and achieve a firm grip on sidewall  45 A of aperture  45 . A groove  47  is present around the orthogonal portion of the outer surface of body  44  adjacent to aperture  45  and just below head  43 . A circular steel helical spring  48  is in groove  47  around body  44  and extends slightly beyond the sides of body  44 . 
     An optical disk having a central aperture is captured on inner mask  42  by inserting the tapered end of body  44  through the aperture in the disk. Spring  48  deflects and allows the disk to move upward toward head  43 . Once the disk is past, spring  48  springs back, and captures the disk under head  43 . Head  43  extends over the surface that is to be coated, and thereby masks a central circular portion of the disk during the sputtering process. 
     Inner mask  42  may be formed from aluminum, steel, or other materials. All or part of the upper surface of annular head  43  (which is exposed to direct sputter deposition) has a rough surface that includes many asperities  49  that can trap sputtered material. Accordingly, material sputtered onto annular head  43  does not fall on and contaminate the disk. The asperities may be provided by spraying the upper surface of annular head  44  with an aluminum ARC spray. The coating gets rougher going from the outer perimeter of head  43  toward aperture  45 . 
     FIG. 4 is an exploded view of an alternative inner mask  50 . Features similar to inner mask  42  of FIG. 3 have similar reference numbers. Mask  50  is an assembly of several parts, including a first body  51  having a vertically-extending cylindrical portion  51 A and an integral annular head  43  with asperities  49  thereon. Cylindrical portion  51 A has a central cylindrical aperture  45  with an inner vertical sidewall  45 A. A screw hole  52  is at the bottom of cylindrical portion  51 A. First body  51  is within a hollow second body  53 . The outer surface of second body  53  includes an orthogonal upper portion  56  and a tapered lower portion  57 . A strip  58  of spring steel is between first body  51  and second body  53 . A screw  54  extends through a hole  55  in second body  53  and a hole in strip  58  and engages the threads of screw hole  52  of first body  51 . Screw  54  thus secures first body  51  to second body  52 . Orthogonal portion  56  of second body  53  includes one or more (e.g., two or four) chamfered openings in which a steel ball  59  is held. As a disk passes up second body  53 , the sidewall of the central aperture of the disk contacts balls  59  and causes balls  59  to deflect inward. After the disk moves past balls  59 , spring  58  pushes balls  59  outward, which causes the disk to be captured under head  43 . 
     FIG. 5 is a cross-sectional side view of a first embodiment of an outer mask  60 . Outer mask  60  is formed of aluminum, steel, or another material. 
     Outer mask  60  includes a hollow, vertically-extending body  61 . Outer mask  60  is sized so that a disk  22  will fit horizontally within the round central aperture  67  of body  61 . A lip  62  is at an upper first end of body  61  and extends inwardly around aperture  67 . Lip  62  extends over a circumferential portion of disk  22 , and thereby masks the outer periphery of disk  22  during the sputtering process. Lip  62  does not contact the sputtered surface of the disk. The upper surface of lip  62  (which is exposed to direct sputter deposition) has numerous asperities  49  thereon to catch sputtered material, although asperities  49  may be omitted. A horizontal flange  63  extends outwardly from an outer surface of body  61 . In one embodiment, flange  63  may be present around the entire outer surface  65  of body  61 . In other embodiments, one or more (e.g., four) discrete flanges or other protrusions may be spaced around the outer surface  65  of body  61 . The inner surface of body  61  includes a tapered portion  66  adjacent to end  64 , where disk  22  enters aperture  67 . The inner surface of body  61  also includes a groove  68 , which is engaged by a helical spring  41  (FIG. 7) in the tray  39  upon which disk  22  rests during the sputtering process. The outer mask gripper of the end effector grips mask  60  on the unsputtered outer surface  65  of body  61  beneath flange  63 , and may use the lower surface of flange  63  to lift outer mask  60 . 
     FIG. 6 is a cross-sectional side view of an alternative outer mask  69 . Most of the features of outer mask  69  are the same as those of outer mask  60  of FIG.  5 . Instead of having a flange  63 , however, outer mask  69  has a groove  70  in outer surface  65  that is engaged by the outer mask gripper of the end effector. 
     FIG. 7 is a cross-sectional view of a first embodiment of an end effector  28 A (or  28 B) of FIG.  1 . In this view, end effector  28 A is positioned at loadlock  24  (FIG. 1) so that lid  32  is covering loadlock opening  24 A. End effector  28 A includes an inner mask gripper  29  and an outer mask gripper  30 , the component parts of which are described below. Inner mask gripper  29  is gripping inner mask  42 , and outer mask gripper  30  is gripping outer mask  60 . 
     Disk  22  of FIG. 7 is captured and centered on inner mask  42 , and is horizontally disposed within outer mask  60 . Disk  22  rests horizontally on a metal tray  39 , which in turn rests on a vertically moveable pedestal  27  (FIG.  1 ). In particular, disk  22  is supported on flat-topped annular protrusions that extend from the top surface of tray  39 . The protrusions are located near the center of disk  22  and at the periphery of disk  22 , respectively. 
     Tray  39  also supports inner masks  42  and outer mask  60 . Body  44  (FIG. 3) of inner mask  42  is supported in a central aperture in tray  39 . Spring  48  (FIG. 3) of inner mask  42  presses against the sidewall of the central aperture in tray  39 , and thus provides a supportive engagement with tray  39 . Second end  64  (FIG. 4) of outer mask  60  is supported above an outwardly extending flange  40  of tray  39 . A helical spring coil  41  in a groove around tray  39  engages groove  58  (FIG. 5) on the inside surface of body  61  of outer mask  60  and applies an outward force, thereby supporting and securing outer mask  60  to tray  39 . The metal to metal contacts between inner mask  42  and outer mask  60 , on the one hand, and tray  39  on the other allow heat from the plasma to be conducted from inner mask  42  and outer mask  60  to tray  39 , which prevents heat damage to disk  22 . 
     Pedestal  27  is vertically raised to bring a processed disk  22 , tray  39 , inner mask  42 , and outer mask  60  from the carousel carrier in the main vacuum chamber to loadlock  24 . Pedestal  27  is vertically lowered to bring an unprocessed disk  22 , tray  39 , inner mask  42 , and outer mask  60  to the carousel carrier from loadlock  24 . 
     Inner mask gripper  29  includes gripper fingers  34  that are inserted into aperture  45  of inner mask  42 . Gripper fingers  34  are connected to gripper arms  33 . A linear actuator  31  and a bellows  31 A cause gripper arms  33  and gripper fingers  34  to move laterally back and forth, as shown by the two headed arrow of FIG.  7 . When gripper arms  33  are moved apart (the “open” position), gripper fingers  34  push against inner wall  45 A of aperture  45  of inner mask  42  with sufficient force to allow inner mask  42  and disk  22  to be lifted and moved. When gripper fingers  34  are moved together (the “closed” position), inner mask  42  is released onto tray  39 . Gripper fingers  34  may be threaded to enhance their grip on inner mask  42 . Inner mask  50  of FIG. 4 may be used instead of inner mask  42 . 
     A feature of inner mask gripper  29  is that inner masks  42  and  50  are only gripped on vertically-extending sidewall  45 A within aperture  45 , which is not subjected to direct sputter deposition. Artisans will appreciate that numerous methods may be implemented for gripping the inner mask within central aperture  45 . 
     Outer mask gripper  30  of FIG. 7 is shown in an enlarged view in FIG.  8 . Threads  35  mount outer mask gripper  30  to lid  32 . Outer mask gripper  30  includes a rotary actuator  37  that rotates an “L” shaped cam  36  that grips outer mask  60  (FIG.  5 ). When actuator  37  rotates cam  36  into the “open” position, the horizontal portion of cam  36  is positioned beneath flange  63  (FIG. 5) so that outer mask  60  may be lifted by cam  36 . When actuator  37  rotates cam  36  into a “closed” position, cam  36  is positioned so that there is no overlap between cam  36  and flange  63 , thereby releasing outer mask  60 . 
     The number of outer mask grippers  30  of end effector  28 A may vary. For example, FIG. 9A is illustrates an end effector  28 A having four outer mask grippers  30  at 90 degree angles to each other. In an alternative embodiment, two or three outer mask grippers  30  may be used. 
     FIG. 9B illustrates another embodiment an outer mask gripper  30 - 1  for end effector  28 A. In this embodiment, one rotational actuator  37  is used to control three cams  36 . The cams  36  are connected by a timing belt  38  that provides for synchronized motion. The rotation of actuator  37  to the “open” position moves each of the cams  36  beneath flange  63  in a coordinated fashion. Inner mask gripper  29  is within timing belt  38 . 
     FIG. 10 is a simplified view alternative embodiment of end effector  28 A for use with outer mask  69  of FIG.  6 . For simplicity, inner mask gripper  29  is not shown. In this embodiment, each of four outer mask grippers  80  includes a pneumatic actuator, air passage  81  (shown in part), and bellows  82 . When outer mask gripper  80  is in an “open” position, a plunger  83  is moved toward outer mask  69 . Plunger  83  moves toward outer mask  69  and engages groove  70  of outer mask  69  (FIG.  6 ), thereby gripping outer mask  69 . When the pneumatic pressure is released, springs  93  in hollow cylindrical body  92  force plunger  83  outward, thereby moving gripper  20  to the “closed” position and releasing outer mask  69 . 
     In FIG. 10, end  64  of outer mask  69  is resting on a flange  85  of a metal substrate transport tray  84 . Tray  84  supports disk  22 , inner mask  50  and outer mask  69  on the carousel and in the sputtering chambers, similar to tray  39  of FIG.  7 . Tray  84  has a central aperture in which inner mask  50  is inserted and supported. Tray  84  is on a vertically moveable pedestal  27 - 1 , which is similar to pedestal  27  of FIG.  7 . 
     FIG. 11 illustrates pertinent portions of an alternative embodiment of an end effector  28 A. In this embodiment, only a single actuator and a single feed-through are used to grip both the inner mask and the outer mask. In addition, lid  32 - 1  is flat, rather than peaked like lid  32  of FIG.  7 . 
     In FIG. 11, inner mask gripper  29  is the same as shown in FIG. 7, except that inner mask gripper arm  33  includes a flange  86  that extends outwardly from each arm  33 . A flexure  88  of steel, spring steel, or the like is connected between flange  86  and a metal (e.g., steel or aluminum) outer mask gripper  87 . Outer mask gripper  87  has roughly a “C” shape and is supported on pin  90 . Pin  89  links movement from gripper arm  33  and slides and rotates pin  90 . Flexure  88  is connected to pin  89 . 
     When inner mask gripper  29  moves gripper arms  33  and gripper fingers  34  to an “open” position so as to engage inner mask  42 , flexure  88  moves laterally outward, which causes outer mask gripper  87  to rotate towards outer surface  65  of outer mask  60  (FIG.  5 ). A horizontal gripper finger  91  of outer mask gripper  87  is thereby positioned closely beneath flange  63  of outer mask  60  (FIG. 5) so that outer mask  60  may be lifted by finger  91  of outer mask gripper  87 . When inner mask gripper  29  moves gripper arms  33  and gripper fingers  34  to a closed position, flexure  88  moves laterally inward, which causes outer mask gripper  87  to be rotated away from outer mask  60  so that there is no longer any overlap between flange  63  and finger  91 , and thereby releases outer mask  60 . 
     Thus, in the embodiment of FIG. 11, the motion of inner mask gripper  29  is used to cause a gripping of both inner mask  42  and outer mask  60 . Other ways of borrowing the motion of inner mask gripper  29  to grip outer masks  60  or  69  (FIGS. 5 and 6) will be readily apparent to practitioners of the mechanical arts. Such methods include using cables and/or linkages. Conversely, the motion of an outer mask gripper  30  of FIG. 7 could be borrowed to grip inner masks  42  or  50  in alternative embodiments. 
     A feature of the outer mask grippers shown in FIGS. 7 through 11 is that outer masks  60  and  69  are only gripped on an outer surface that is not subject to direct sputter deposition. Artisans will appreciate that numerous methods may be implemented for gripping the unsputtered portion of the outer mask other than using the example methods shown herein. 
     The operation of the substrate handling system  21  of FIG. 1 will be described with the aid of FIGS. 12 a - 12   f.  FIG. 12 a  shows substrate handling system  21  in a down position. End effector  28 A is located at an external disk change station  100 . Inner mask  42  and outer mask  60  are gripped (i.e., “open” position) by the inner mask gripper and outer mask gripper, respectively, of end effector  28 A. A vacuum system or some other disk loading system at disk change station  30  is used to place an unprocessed disk  22  onto inner mask  42  and within outer mask  60 . While inner mask  42  and outer mask  60  are at disk changing station  30 , and in route to and from disk changing station  30 , masks  42  and  60  are exposed to ambient and therefore can cool. 
     Meanwhile, the opposing end effector  28 B is located at loadlock  24  of sputtering system  20 . End effector  28 B is not engaged with a disk  22 , inner mask  42 , or outer mask  60 , but the carousel of sputtering system  20  has been indexed to position a processed optical disk  22 , inner mask  42 , outer mask  60 , and tray  39  beneath end effector  28 B. As mentioned above, inner mask  42 , outer mask  60 , and tray  39  accompany disk  22  on the carousel and to the sputtering stations of sputtering system  20 . The inner mask gripper and outer mask grippers are in a “closed” position. Lid  32  of end effector  28 B covers opening  24 A of loadlock  24 . 
     FIG. 12 b  has pedestal  27  of sputtering system  20  (FIG. 1) in up position. Pedestal  27  moves a processed disk  22 , masks  42  and  60 , and tray  39  to meet loadlock  24  and end effector  28 B. Tray  39  also seals the lower access to loadlock  24  when pedestal  27  is in its up position, which isolates loadlock  24  from the main vacuum chamber of sputtering system  20 . After pedestal  27  has risen, loadlock  24  vents to the atmosphere. After the venting is complete or during venting, the inner mask gripper and outer mask gripper of end effector  28 B are moved to their respective open positions so that processed inner mask  42  and outer mask  60  are gripped by end effector  28 B, thereby capturing disk  22 A. 
     FIG. 12 c  shows substrate handling system  21  in an up position, which raises end effectors  28 A and  28 B. End effector  28 B is gripping a processed disk  22 , inner mask  42 , and outer mask  60 , and end effector  28 A is gripping an unprocessed disk  22 , inner mask  42 , and outer mask  60 . Tray  39  stays in loadlock  24  and pedestal  27  stays up. 
     Next, as illustrated in FIG. 12 d,  substrate handling system  21  is rotated by 180 degrees, thereby locating end effector  28 B at disk change station  100 , and end effector  28 A at loadlock  24 . Pedestal  27  remains in an up position at loadlock  24 . 
     FIG. 12 e  shows substrate handling system  21  having returned to a down position. At disk change station  100 , the unloading of processed disk  22  from inner mask  42  of end effector  28 B (and the subsequent loading of another unprocessed disk  22  onto inner mask  42  and within outer mask  60  of end effector  28 B) is accomplished by the vacuum apparatus or other mounting system at disk change station  100 . 
     At loadlock  24  of FIG. 12 e,  lid  32  of end effector  28 A is placed over access opening  24 A of loadlock  24  so as to form a vacuum tight seal. End effector  28 A pushes inner mask  42  and outer mask  60  onto tray  39 , securing masks  42  and  60  to tray  39 . The inner mask gripper and outer mask gripper are moved to the “closed” position, thereby releasing the unprocessed disk  22 , inner mask  42  and outer mask  60  onto tray  39 . Next, loadlock  24  is pumped down to create a vacuum. 
     FIG. 12 f  illustrates processed disk  22  after its separation from end effector  28 B at disk changing station  100 . Disk changing station  100  subsequently exchanges the processed disk with an unprocessed disk  22 . Meanwhile, at loadlock  24 , pedestal  27  is lowered through an aperture in the carousel so that unprocessed disk  22 , inner mask  42 , outer mask  60 , and tray  39  are placed on the carousel system of sputtering system  20 . Subsequently, the carousel indexes while the plasma is off. The indexing of the carousel locates another processed disk  22 , inner mask  42 , outer mask  60 , and tray  39  under end effector  28 A. Whereupon, the cycle described above is repeated, so that end effector  28 A removes a processed disk  22  from loadlock  24 , and end effector  28 B provides an unprocessed disk  22  to loadlock  24 . Substrate handling system  21  is capable of handling several thousand disks per day. 
     The material that is being sputtered onto disk  22  also coats the upper surfaces of annular head  43  of inner mask  42  and lip  62  of outer mask  60  (FIGS.  3  and  5 ). Over time, the edges of annular head  43  and circular lip  62  become irregular and extended further. The combined effect of the deposition on the annular head  43  and circular lip  62  is a reduction in coated surface area on the disk and irregularity in the coated area boundaries. When this deposition or other maintenance issues have made inner mask  42  and outer mask  60  unusable, they are replaced by a new or refurbished inner mask  42  and outer mask  60 . Deteriorated inner mask  42  and outer mask  60  are removed at disk change station  100  by closing the inner mask gripper and outer mask gripper, thereby releasing inner mask  42  and outer mask  60 . A new inner mask  42  and outer mask  60  are provided for gripping by the end effector. There is no need for a special mask change station, nor is there any need for venting sputtering system  20  to change the masks. 
     The embodiments described above are exemplary only. Variations will be apparent to artisans in view of the above disclosure. The invention is limited only by the following claims.