Abstract:
To achieve cost efficiency, solar cells must be processed at a high throughput. Breakages, which may leave debris on the clamping surface of the platen, adversely affect this throughput. A plurality of embodiments are disclosed which may be used to remove debris from the clamping surface without breaking the vacuum condition within the processing station. In some embodiments, a brush is used to sweep the debris from the surface of the platen. In other embodiments, an adhesive material is used to collect the debris. In some embodiments, the automation equipment used to handle masks may also be used to handle the platen cleaning mechanisms. In still other embodiments, stream of gas or ion beams are used to clean debris from the clamping surface of the platen.

Description:
[0001]    This application claims priority of U.S. Provisional Patent Application Ser. No. 61/366,641, filed Jul. 22, 2010, the disclosure of which is incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    This disclosure relates to processing tools having a platen, and more particularly, to platen cleaning apparatuses and methods. 
       BACKGROUND 
       [0003]    One type of processing tool is an ion implanter that treats a workpiece with ions. The ion implanter may be a beam line ion implanter or plasma doping ion implanter. A beam line ion implanter includes an ion source and an extraction electrode assembly to extract a well defined ion beam from the ion source. One or more beamline components known in the art may control and modify the ion beam to obtain an ion beam with desired characteristics, which is directed towards a surface of the workpiece. The ion beam may be distributed across the surface of the workpiece by ion beam movement, workpiece movement, or a combination of the two. The entire path traversed by the ion beam may be pumped to a vacuum condition during ion treatment. 
         [0004]    An ion implanter may also include plasma doping ion implanters that generate plasma in a chamber. The workpiece is also positioned in the chamber of the plasma doping ion implanter. Ions from the plasma are attracted towards a surface of a workpiece during certain time intervals. 
         [0005]    For either type of ion implanter, the workpiece may include, but not be limited to, a solar cell, a semiconductor substrate, a polymer substrate, and a flat panel. The workpiece is supported by a platen having a clamping surface. The platen may be an electrostatic platen that generates electrostatic forces to clamp the workpiece to the clamping surface as is known in the art. The platen also may physically clamp the workpiece in an alternate embodiment. 
         [0006]    Particles or debris may adhere to the clamping surface of the platen and degrade the performance of the same. For instance, the clamping force, clamping release times, and ability of the platen to cool the workpiece may be degraded. One source of particles is from a workpiece breakage event. For example, a solar cell is generally thinner and more fragile than other workpieces. A solar cell may therefore break when being coupled to, or released from, the clamping surface of the platen. Residue and particles from the solar cell itself may adhere to the clamping surface. 
         [0007]    One conventional method of cleaning particles from a clamping surface of the platen is to vent a processing station from a vacuum condition to an atmospheric condition to allow personnel access to the platen in the processing station to manually clean the same. One major drawback with this conventional method is the time it takes to accomplish this task. For example, it may take considerable time to pump the processing station back to a vacuum condition after venting of the same and cleaning of the platen. This down time adversely impacts the overall throughput of the ion implanter or the number of workpieces that can be processed in a given time interval. 
         [0008]    Accordingly, there is a need for platen cleaning apparatuses and methods that overcome the above described inadequacies and shortcomings. 
       SUMMARY 
       [0009]    To achieve cost efficiency, solar cells must be processed at a high throughput. Breakages, which may leave debris on the clamping surface of the platen, adversely affect this throughput. A plurality of embodiments are disclosed which may be used to remove debris from the clamping surface without breaking the vacuum condition within the processing station. In some embodiments, a brush is used to sweep the debris from the surface of the platen. In other embodiments, an adhesive material is used to collect the debris. In some embodiments, the automation equipment used to handle masks may also be used to handle the platen cleaning mechanisms. In still other embodiments, stream of gas or ion beams are used to clean debris from the clamping surface of the platen. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a better understanding of the present disclosure, reference is made to the accompanying drawings, in which like elements are referenced with like numerals, and in which: 
           [0011]      FIG. 1  is a block diagram of a beam line ion implanter; 
           [0012]      FIG. 2A  is a block diagram of a processing station of the beam line ion implanter of  FIG. 1  having a platen cleaning apparatus according to one embodiment of the disclosure; 
           [0013]      FIG. 2B  is a perspective view of another platen cleaning apparatus; 
           [0014]      FIG. 2C  is a top view of the platen cleaning apparatus of  FIG. 2B ; 
           [0015]      FIG. 2D  is a side view of the platen cleaning apparatus of  FIG. 2B  in the operative position; 
           [0016]      FIG. 2E  is a side view of the platen cleaning apparatus of  FIG. 2B  in the stowed position; 
           [0017]      FIG. 2F  is a view of the connection between the arm and support of the platen cleaning apparatus of  FIG. 2B ; 
           [0018]      FIGS. 3A-C  are partial perspective and cross sectional views of another platen cleaning apparatus according to another embodiment of the disclosure; 
           [0019]      FIG. 4  shows the sequence used to clean a platen using the platen cleaning apparatus of  FIGS. 3A-C ; 
           [0020]      FIGS. 5A-C  is a partial perspective and cross sectional view of another embodiment of a cleaning apparatus having a double-sided brush; 
           [0021]      FIGS. 6A-C  are partial perspective and cross sectional views of another platen cleaning apparatus according to another embodiment of the disclosure having an adhesive roller; 
           [0022]      FIG. 7  shows the sequence used to clean a platen using the platen cleaning apparatus of  FIGS. 6A-C ; 
           [0023]      FIG. 8  is a perspective view of another embodiment of a cleaning apparatus having an adhesive sheet; 
           [0024]      FIGS. 9A-B  is a sequence showing a cross sectional view of a mechanism to controllably remove an adhesive sheet from a platen; and 
           [0025]      FIG. 10  is a perspective view of a platen cleaning apparatus having an adhesive sheet. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. This invention, however, may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. 
         [0027]    Turning to  FIG. 1 , a simplified schematic block diagram of a beam line ion implanter  100  is illustrated. The beam line ion implanter  100  includes an ion source  102 , beam line components  104 , and a processing station  106  that supports one or more workpieces such as a workpiece  110 . The ion source  102  generates an ion beam  105  that is directed via the beam line components  104  to the workpiece  110 . 
         [0028]    The beam line components  104  may include components known to those skilled in art to control and direct the ion beam  105  towards the workpiece  110 . Some examples of such beam line components  104  include, but are not limited to, a mass analyzing magnet, a resolving aperture, ion beam acceleration and/or deceleration columns, an energy filter, and a collimator magnet or parallelizing lens. Those skilled in the art will recognize alternative and/or additional beam line components  104  that may be utilized in the ion implanter  100 . 
         [0029]    The processing station  106  supports one or more workpieces, such as workpiece  110 , in the path of ion beam  105  such that ions of the desired species strike the workpiece  110 . The workpiece  110  may be, for example, one or more solar cells receiving ion treatment. The processing station  106  may include a platen  112  to support the workpiece  110 . The platen  112  may secure the workpiece  110  using electrostatic forces. The end station  106  may also include a scanner (not illustrated) for moving the workpiece  110  in a desired direction. 
         [0030]    The processing station  106  may also include additional components known to those skilled in the art. For example, the processing station  106  typically includes automated workpiece handling equipment for introducing workpieces into the ion implanter  100  and for removing workpieces after ion treatment. It will be understood to those skilled in the art that the entire path traversed by the ion beam  105  is evacuated during ion treatment. The ion implanter  100  may also have a controller (not illustrated) to control a variety of subsystems and components of the ion implanter  100 . 
         [0031]    A plurality of different platen cleaning apparatuses is described herein. These devices may utilize a plurality of different mechanisms, such as mechanical movement to push debris from the platen, or adhesion to draw debris away from the platen. 
         [0032]      FIG. 2A  shows a first embodiment, which utilizes a brush-like mechanism. In  FIG. 2A , a diagram of a platen cleaning apparatus  200  looking downstream in a direction of travel of the ion beam  105  is illustrated. The platen cleaning apparatus  200  is configured to clean a clamping surface  116  of the platen  112  without breaking a vacuum condition of the processing station  106 . The platen cleaning apparatus  200  may include an actuator  202 , a controller  204 , and a platen cleaning device, such as a brush  206 . The actuator  202  may include a motor and drive mechanism to drive the platen cleaning device  206  from a parked position to cleaning positions. The controller  204  can be or include a general-purpose computer or network of general-purpose computers that may be programmed to perform desired input/output functions. The controller  204  can also include other electronic circuitry or components, such as application specific integrated circuits, other hardwired or programmable electronic devices, discrete element circuits, etc. For clarity of illustration, the controller  204  is illustrated as providing an output signal to the actuator  202  and receiving signals from the same. Those skilled in the art will recognize that the controller  204  may provide output signals to other components of the beam line ion implanter  100  and receive input signals from the same. The platen cleaning device  206  may further include a head  208  and bristles  210 . The bristles  210  may be made of materials strong enough to remove particles  220  from the clamping surface  116  of the platen  112  yet gentle enough to not damage the clamping surface  116 . The bristles  310  of this and other embodiments may be any type of object or material that performs a cleaning operation. In some embodiments, the bristles may be nylon, polypropylene or Teflon. In other embodiments, the bristles of this or other embodiments may be conductive, so as to remove any built up charge from the platen, while removing debris. These conductive bristles, or fingers, may be grounded to facilitate removal of excess charge from the platen  112 . 
         [0033]    In operation, the platen  112  may have a rectangular shape and be sized to accommodate six solar cells in a 2×3 matrix. When the platen is in an implanting position  112 ′ an ion beam may strike six solar cells (illustrated in phantom) clamped to a clamping surface  116  of the platen. Particles  220 , shown in exaggerated size, may accumulate on the clamping surface  116  of the platen due to different conditions including solar cell breakage. To clean the clamping surface  116 , the platen  112  may be driven in a “Y” direction  214  to a cleaning position  112 ″. A scan arm  228  is configured to rotate about an axis  226  to position the clamping surface  116  facing downward as shown in the position  112 ″. The actuator  202  may then drive the brush  206  to and from in the direction indicated by arrow  230  so the bristles  210  contact and clean the clamping surface  116  by removing particles  220 . Since the clamping surface  116  is facing downward, the particles  220  would fall downward due to gravity. The platen  112  may then be rotated and driven in the “Y” direction  214  back to the position  112 ′ for further processing of additional workpieces after receipt of the same. 
         [0034]    A view port (not illustrated) may provide a viewing window for an operator to inspect the clamping surface  116 . In addition, a camera (not illustrated) may also be used to verify the condition of the clamping surface  116  after a cleaning operation. 
         [0035]    The bristle  210  material may be vacuum compatible and not impact metals. A cleaning station (not illustrated) may also be added to clean the brush  206  of particles. An air jet could be used in the cleaning station to blow particles from the bristles  210  and/or another “comb” type device could be mechanically driven through the bristles  210  to clean the same. 
         [0036]    Another embodiment that utilizes a brush-like mechanism is shown in  FIGS. 2B-2F . In  FIG. 2B , the platen  112  is shown in the vertical position, although any position in which gravity aids in the removal of debris can be used. The platen cleaning apparatus  240  includes a rotatable arm  245 , pivotably attached to a support  250  (see  FIG. 2C ) at one end, and having a brush  260  with bristles  210  at the opposite end. The brush  260  extends to contact the platen  112 . To clean the platen  112 , an actuator moves the platen up and down, as shown by arrow  255 . This motion removes debris from the platen  112 . 
         [0037]    Turning to  FIG. 2F , a close-up view of the support  250 , rotatable arm  245  and actuator  270  is shown. The actuator  270  has a piston  271 , which may be extended and retracted. When the piston  271  is extended, as shown in  FIG. 2F , the rotatable arm  245  rotates along arc  272  to its stowed position. When the piston is retracted, it causes the arm  245  to rotate along arc  272  to the cleaning position, as shown in  FIGS. 2B and 2D . The actuator  270  can be controlled by a controller  204  ( FIG. 2A ), or any other mechanism. 
         [0038]      FIG. 2D  shows the arm  245  rotated so as to contact the platen in the cleaning position. In this position, the piston  271  is retracted. The brush  260  is in contact with the platen  112 . The platen  112  then is translated in the vertical direction, as shown in arrow  274 , to remove debris.  FIG. 2E  shows the arm  245  rotated to the stowed position. In this position, the piston  271  is extended. While the platen cleaning apparatus is within the processing station, the brush  2600  is out of the path of the ion beam when in this position. 
         [0039]    Turning to  FIGS. 3A-C , yet another embodiment of the present disclosure is illustrated having a platen cleaning device, such as a mask brush  306 .  FIG. 3A  shows a perspective view of a mask brush  306 , while  FIG. 3B  shows a cross-sectional view.  FIG. 3C  shows the mask brush  306  positioned between the platen  112  and the robot end effector  312 . 
         [0040]    In general, a mask may be used in the beam line ion implanter  100  to define selected areas for ion treatment. This mask may be a proximity mask or shadow mask, for example. The beam line ion implanter  100  may also include differing mask handling robots with associated end effectors  312  to retrieve the mask and/or mask-like structure and position the same upstream of the workpiece. A brush including bristles  310  may be affixed to a mask or a mask-like structure to form the mask brush  306 . 
         [0041]    Turning to  FIG. 4 , a cross sectional view of a mask brush  306  having bristles  310  to clean the clamping surface  116  of the platen  112  is illustrated in different operational positions. To initiate the cleaning operation, the platen  112  would be driven to a similar position  112 ″ of  FIG. 2  with its clamping surface  116  facing downward as illustrated in step ( 1 ) of  FIG. 4 . As described above, the platen  112  may be rotated such that the clamping surface  116  is facing downward, or another direction in which gravity aids in the removal of debris. In this position, the end effector  312  may not be in contact with the platen  112 . 
         [0042]    An end effector  312  of a robot may engage and secure a mask brush  306  having bristles  310  affixed thereto. The end effector  312 , with the mask brush  306  secured thereto may extend toward the platen  112  as shown in step ( 2 ). The end effector  312  with the mask brush  306  may extend so as to contact the entirety of clamping surface  116 , as shown in step ( 3 ). In step ( 4 ), the end effector  312  begins retracting away from the platen  112 . In step ( 5 ) the end effector  312  retracts away from the platen  112  so as not to be in contact with the platen  112 . The end effector  112  may move to and from the platen, as shown in steps ( 2 )-( 5 ), one or more times so that the bristles  310  contact the clamping surface  116  to clean the same by removing most, if not all, of the particles  220  stuck to the clamping surface  116 . The inverted orientation of the platen  112  ensures that once the particles  220  are dislodged by the bristles  310 , they fall away from the platen  112  due to gravity. 
         [0043]    After the clamping surface  116  has been cleaned, the end effector  312  of a robot may disengage the mask brush  306 . The robot is then free to engage a different mask, such as one used to create patterned implants. Thus, the mask brush  306  enables the use of an existing piece of equipment to perform this cleaning operation. 
         [0044]    Turning to  FIG. 5A-C , yet another embodiment is illustrated having a double-sided mask brush  406 .  FIG. 5A  shows a perspective view of a double-sided mask brush  406 , while  FIG. 5B  shows a cross-sectional view.  FIG. 5C  shows the double-sided mask brush  406  positioned relative to the robot end effector  312 . 
         [0045]    In a double-sided mask brush  406 , a first set  502  of bristles  310  may be positioned on one side and a second set  504  of bristles may be positioned on an opposing side of the mask brush  406 . The embodiment of  FIGS. 5A-C  is similar to embodiment of  FIGS. 3A-C  and  4  with the main different being the additional set  504  of bristles  310  facing the end effector  312 . This set  504  of bristles  310  allows the end effector  312  to be cleaned any time there is relative motion between the set  504  of bristles  310  and the end effector  312 . This relative motion may be used to clean the end effector of particles such as particles  520  resulting from a broken wafer event. 
         [0046]    In operation, the double-sided mask brush  406  may be in a storage location, such as a shelf, and retrieved by an end effector  312  of an associated robot. The end effector  312  may be positioned underneath the double-sided mask brush and then the double-sided mask brush  406  may be lowered onto the end effector  312 . The end effector  312  with the double-sided mask brush  406  affixed thereto may then clean the clamping surface  116  of the platen  112  similar to the steps ( 1 )-( 5 ) detailed in  FIG. 4 . The additional set  504  of bristles  310  can clean the end effector  312  during the extension or retraction operation or essentially anytime there is relative motion between the end effector  312  and the second set  504  of bristles  310 . Again, the bristles  310  of this and other embodiments may be any type of object or material that performs a cleaning operation. 
         [0047]    In each of the previous embodiments, a platen cleaning device having bristles on at least one surface is disclosed. This platen cleaning device may attached to a robot end effector, either permanently or may be removably held by the end effector. In another embodiment, the platen cleaning device is attached to an actuator which moves the platen cleaning device. In all of these embodiments, the platen cleaning device is attached to a movable arm, which can be extended or retracted from the platen. 
         [0048]    The platen cleaning device is used to sweep debris from the platen, preferably when an ion implantation is not occurring. When implantation is occurring, the platen cleaning device is located so as not to be in the path of the ion beam. When ion implantation is not occurring, the platen may be cleaned. During this time, the platen may be rotated or otherwise moved such that the clamping surface is facing downward, or another direction in which gravity aids in the removal of debris . The movable arm with the platen cleaning device having bristles is then extended and retracted so as to sweep debris from the platen. Since the surface of the platen is facing downward, the debris falls, due to gravity. 
         [0049]    In the embodiment of  FIG. 2 , the movable arm may be dedicated to this cleaning operation, in that it is not used for any other purposes. In this embodiment, the actuator and controller are used to control the platen cleaning device. 
         [0050]    In the embodiments of  FIGS. 3A-C  and  5 A-C, the movable arm may be an end effector, capable of also be used to engage, position and disengage masks during ion implantation. In these embodiments, the platen cleaning device having the bristles may be shaped like a traditional mask or may be a mask-like structure. A mask-like structure, as defined herein, is a device having a size and shape such that the end effector may engage it as it would a traditional mask. Thus, a mask-like structure includes both masks and similarly shaped carriers or other structures. 
         [0051]    Each of these platen cleaning devices is configured to clean a clamping surface  116  of the platen  112  without breaking a vacuum condition of the processing station  106 . 
         [0052]    While the disclosure describes bristles in conjunction with the embodiments of  FIGS. 2-5 , it is understood that any cleaning mechanism suitable for moving across the surface of the platen and mechanically removing debris may be used. 
         [0053]    In addition to sweeping, other methods may be used to remove debris from a platen. 
         [0054]    Turning to  FIGS. 6A-C , yet another embodiment of the present disclosure is illustrated having an adhesive roller  506  fixed to an object  520 , such as a mask-like structure. A mask-like structure, as defined herein, is a device having a size and shape such that the end effector may engage it as it would a traditional mask. Thus, a mask-like structure includes both masks and similarly shaped carriers or structures.  FIG. 6A  shows a perspective view of an adhesive roller  506 , while  FIG. 6B  shows a cross-sectional view.  FIG. 6C  shows the adhesive roller  506  positioned relative to the platen  112  and the robot end effector  312 . 
         [0055]    The adhesive roller  506  may include an adhesive material, such as tape, that can clean the clamping surface  116  of the platen  112  while leaving little harmful residue. A plurality of adhesive rollers may be fixed to the object  520  and each adhesive roller  506  is configured to rotate about a central axis  502  of the same. In some embodiments, a rod passes through the central axis  502  and is secured at both ends to the object  520 . 
         [0056]    Turning to  FIG. 7 , a cross sectional view of a plurality of adhesive rollers  506  fixed to an object  520  to clean the clamping surface  116  of the platen  112  is illustrated in different operational positions. To initiate the cleaning operation, the platen  112  would be driven to a similar position  112 ″ of  FIG. 2  with its clamping surface  116  facing downward, or another direction in which gravity aids in the removal of debris, as illustrated in step ( 1 ) of  FIG. 7 . An end effector  312  of a robot may engage the object  520  with the plurality of adhesive rollers  506  fixed thereto. The object  520  may be a mask-like structure so it can be handled by existing handling automation equipment such as robots with associated end effectors. The end effector  312 , with the object  520  secured thereto may extend toward the platen  112  as shown in step ( 2 ). The end effector  312  with the object  520  may extend so as to contact the entirety of clamping surface  116 , as shown in step ( 3 ). In step ( 4 ), the end effector  312  begins retracting away from the platen  112 . In step ( 5 ) the end effector  312  retracts away from the platen  112  so as not to be in contact with the platen  112 . The end effector  312  may extend to and from the platen  112  in steps ( 2 )-( 5 ) one or more times so that the plurality of adhesive rollers  506  contact the clamping surface  116  to clean the same by removing most, if not all, of the particles  220  stuck to the clamping surface  116 . The inverted orientation of the platen  112  ensures that any dislodged particles not adhered to the rollers  506  fall away from the platen  112  due to gravity. 
         [0057]    In each of the previously described embodiments, the brush or end effector is described as moving relative to the platen. However, it is understood that in other embodiments, the brush or end effector may be moved to contact the platen, and the platen is then moved, while the brush or end effector remains stationary. In other words, it is the relative movement between the platen and the platen cleaning apparatus that aids in the removal of debris. Relative movement can be accomplished by moving the brush or end effector, the platen, or both components. 
         [0058]    The above embodiments disclose the use of gravity to aid in debris removal. However, the disclosure is not limited to these configurations. Certain embodiments may rely only on the action of the platen cleaning apparatus, without the use of gravitational force. 
         [0059]    Turning to  FIG. 8 , yet another embodiment of the present disclosure is illustrated having one or more adhesive sheets  802  affixed to an object  904  that is brought into contact with the clamping surface  116  of the platen  112  to clean the same. The object  904  may be a mask-like structure, where a mask-like structure is a device having a size and shape such that the end effector may engage it as it would a traditional mask. Thus, a mask-like structure includes both masks and similarly shaped carriers or structures. The adhesive sheets  802  include one side to contact the clamping surface  116 . This side is fabricated of adhesive material, such as tape, to remove particles from the same while leaving little harmful residue. 
         [0060]    In operation, the adhesive sheets  802  have one side that is adhered to an object  904 , such as a mask or mask-like structure that can be handled by existing handling automation equipment. The cleaning adhesive side of the adhesive sheet  802  is brought into contact with the clamping surface  116  and particles are removed there from when the adhesive sheet is removed from the clamping surface  116 . 
         [0061]      FIGS. 9A-B  illustrates one embodiment where an adhesive sheet  802  is affixed to an object  904 . The object  904  is driven towards the clamping surface  116  and hence the cleaning side of the adhesive sheet  802  contacts the same. To aid in a controlled removal of the adhesive sheet  802  (by preventing the adhesive sheet  802  from “popping” off), one side of the object  904  may have a downward protrusion  906 . When in the cleaning position, the object  904  and adhesive sheet  802  rests flat on the clamping surface  802 , as shown in  FIG. 9A . Downward protrusion  906  is positioned such that it does not contact the clamping surface  116 . 
         [0062]    During removal of the adhesive sheet  802 , shown in  FIG. 9B , a clamping mechanism having brackets  912   a ,  912   b  may be driven upward in the direction of arrows  922  so that a shelf  910  of one bracket  912   a  first contacts the protrusion  906  before any portion of the other bracket  912   b  contacts the object  904 . In this way, one side of the adhesive tape  802  proximate the arrow  914  is first peeled off the clamping surface  116  to promote a peeling effect for disengaging the adhesive sheet  802  and to help prevent a sudden “popping” off of the adhesive sheet  802 .  FIG. 9B  shows the object  904  partially disengaged from the clamping surface  116 , as the protrusion  906  is pushed up by bracket  912   a.    
         [0063]    Alternatively, or in addition to the offset surfaces of  FIGS. 9A-B , the lift pins  931 ,  932  of the platen  112  may also be employed to aid in the peeling or lifting of the adhesive sheet  802  from the clamping surface  116 . 
         [0064]      FIG. 10  is a perspective view of one embodiment of the disclosure having an adhesive sheet  802  adhered to a mask-like structure  904  that can be brought into contact with the clamping surface  116  of the platen  112  to clean the same. In this embodiment, the robotic end effector  312  may bring the mask-like structure  904  to the mask clamp/lift  955 . The mask clamp/lift  955  lowers the mask-like structure  904  to the platen  112  and clamps it. The adhesive sheet  802  is now in contact with the clamping surface  116  of the platen  112 . Subsequently, the mask clamp/lift  955  lifts the mask-like structure  904  off the clamping surface of the platen  112 , taking debris with it on the adhesive sheet. 
         [0065]    In yet another embodiment consistent with the present disclosure, a cleaning workpiece may be brought into contact with the clamping surface  116 . Testing has shown that bringing clean solar cell wafers into contact with the clamping surface  116  of the platen  112  has a cleaning effect by removing some particles adhered thereto. In one method of operation, a solar cell breakage event may leave particles on the clamping surface  116  of the platen  112 . One or more clean solar cells may be loaded into and cycled through the ion implanter being clamped and released from the clamping surface until the platen  112  has adequately recovered from the breakage event. Running such test or clean wafers through the implanter can clean the clamping surface  116  without breaking the vacuum condition in the processing station. In this embodiment, the test or clean wafers are clamped and removed from the platen without performing any processing on the wafers. In other words, the wafers are used exclusively for their ability to remove debris from the platen and are not processed. 
         [0066]    In yet another embodiment, a single array of jets or a plurality of arrays of jets may direct a cleaning gas towards the clamping surface. The cleaning gas may be nitrogen or other benign process gases to remove particles from the clamping surface  116 . The pressure within the processing station may also be varied to maximize particulate removal. In one embodiment, the position of the jets is fixed. In this case, the clamping surface  116  may be scanned across an array of jets. The clamping surface  116  may also be positioned in such a way that gravity does not allow the dislodged particles to redeposit on the clamping surface  116 . In another embodiment, the platen may remain stationary, while the gas source is moved. The process of directing a cleaning gas uses a pump and vent cycle. This pump and vent cycle may be repeated several times, as desired. 
         [0067]    In yet another embodiment, a low energy ion beam of a particular species may be directed at the clamping surface  116 , which is positioned at a high incident angle to effectively have the ion beam provide a glancing blow to the clamping surface. In one embodiment, the species may be argon. The glancing ion beam effectively cleans the clamping surface  116  while enabling the vacuum condition in the processing station to be maintained. 
         [0068]    The clamping surface  116  can be exposed to the ion beam in one of more orientations to maximize the cleaning effect, e.g., the platen  112  can rotate about its center four times by 90 degrees each time, thus exposing each quadrant to the high incident angle ion beam. 
         [0069]    There has thus been provided platen cleaning apparatuses and methods that enable the ion implanter to maintain high throughput. For workpieces such as solar cells, the throughput of the ion implanter is critical to maintaining a low cost of ownership. The cleaning apparatuses and methods provided herein can be utilized without breaking the vacuum condition in the processing station. 
         [0070]    The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Further, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes.