Abstract:
An apparatus and method for recovery and cleaning of broken substrates, especially beneficial for fabrication systems using silicon wafer carried on trays. Removal of broken wafers and particles from within the fabrication system is enabled without requiring disassembly of the system and without requiring manual labor. A placing mechanism moves a suction head to location of the broken substrate and a suction pump coupled to a flexible hose is used to remove the broken pieces. A hood is positioned at the inlet of the suction head, and setback extensions are provided at the bottom of the hood to allow air flow into the inlet and prevent thermal conductance from the tray to the hood. Pins are extendable about the inlet of the suction head to enable breakage of the wafer to smaller pieces for easy removal.

Description:
RELATED CASES 
       [0001]    This Application is a divisional application of, and claims priority from, U.S. application Ser. No. 13/115,064 filed on May 24, 2011. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to system and method for processing substrates, such as silicon wafers for semiconductor, solar cells, and other applications, in a clean environment. More specifically, the invention relates to system and method for handling broken substrates, especially broken silicon wafers. 
         [0004]    2. Description of the Related Art 
         [0005]    State of the art systems for fabrication of semiconductor wafers generally utilize a mainframe, about which several processing chambers are mounted. Other systems, especially those used for solar cell fabrication, are structured as in-line systems, wherein transport of substrates from one chamber to the next is performed in a linear fashion. Regardless of the architecture used, at some point the wafers have to be transferred from atmospheric environment to vacuum environment. This is done in order to introduce the wafers into a vacuum processing chamber, such as chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), physical vapor deposition system (PVD), etc. 
         [0006]    In many systems used for fabricating integrated circuits, the wafers move from chamber to chamber individually. On the other hand, for solar cells fabrication, many linear systems utilize trays, upon which multiple silicon wafers are placed. The tray can move from chamber to chamber in a linear fashion, or the wafers can be moved separately and placed on stationary trays, such that in each chamber many silicon wafers are processes concurrently on a single tray e.g., 64 substrates of 125 mm by 125 mm each. 
         [0007]    As can be appreciated, such systems operate in clean rooms under strict handling protocols. However, at times it happens that a wafer breaks in the system, whether during processing or during transport. Such breakage generates broken pieces, particles, and dust, that can cause contamination and lead to disruptions of production. Generally, when such breakage occurs, the system has to be stopped and disassembled in order to perform manual cleaning. Such disruption is costly from the manufacturing throughput perspective, and also requires manual labor for the cleaning. The effect on system throughput is especially acute in solar cell fabrication, where generally each system&#39;s throughout is on the order of one to three thousand wafers per hour. 
       SUMMARY 
       [0008]    The following summary of the invention is included in order to provide a basic understanding of some aspects and features of the invention. This summary is not an extensive overview of the invention and as such it is not intended to particularly identify key or critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented below. 
         [0009]    Various embodiments of the present invention provide system and method for detection, recovery and cleaning of broken substrates. Embodiments of the invention are especially beneficial for fabrication systems using silicon wafer carried on trays. Embodiments of the invention enable removal of broken wafers and particles from within the fabrication system without requiring disassembly of the system and without requiring manual labor. 
         [0010]    According to various embodiments of the subject invention, a broken substrate removable system for use in a substrate processing system is provided, comprising: a suction head having an inlet; a placing mechanism for moving the suction head to location of the broken substrate; a suction pump; and a flexible hose coupling the suction head to the suction pump. A hood is positioned at the inlet of the suction head, and setback extensions are provided at the bottom of the hood to allow air flow into the inlet and prevent thermal conductance from the tray to the hood. A plurality of movable pins are extendable about the inlet of the suction head to enable breakage of the wafer to smaller pieces for easy removal. The head placing mechanism can be constructed as a first gantry providing linear motion in one direction and a second gantry providing linear motion is a perpendicular direction. Alternatively, The head placing mechanism can be constructed as a rotatable pivot providing rotational motion and an arm providing linear motion. A parking and disposal station enables parking of the suction head when not in use and disposal of broken pieces removed by the suction head. Optical sensors, such as digital cameras, are coupled to a controller to detect a broken wafer, and monitor and/or control the placing mechanism to place the suction head above the location of the broken wafer, and to confirm the broken wafer has been successfully removed post operation. 
         [0011]    According to embodiments of the invention, a method for removing pieces of broken wafer from a plate supporting a plurality of wafers in a fabrication system is disclosed, comprising: analyzing an optical signal to determine whether one of the plurality of wafers is broken; when it is determined that a broken wafer occupies a position on the plate, transporting the plate to an exchange station, placing a suction head over the position of the broken wafer, and activating a suction pump to remove the pieces of the broken wafer. Optionally, when it is determined that a broken wafer occupies a position on the plate, the plate is moved to a position of a secondary optical sensor to verify that a broken wafer is on the plate. In another embodiment, incoming wafers are analyzed to determine if there are breakages or damage to the wafers prior to processing. Suspected wafers are removed from the incoming tray to minimize the potential of wafers breaking inside the processing apparatus. 
         [0012]    Other aspects and features of the invention will become apparent from the description of various embodiments described herein, and which come within the scope and spirit of the invention as claimed in the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIGS. 1A and 1B  are general schematics depicting major components of examples of system architectures for implementing embodiments of the invention. 
           [0014]      FIGS. 2A and 2B  are general schematics depicting major components of system architectures according to embodiments of the invention, showing the broken substrate recovery system installed over the factory interface of the systems shown in  FIGS. 1A and 1B . 
           [0015]      FIG. 2C  illustrates another embodiment, showing two processing chambers arranged linearly, and a flipping station with broken wafer recovery system positioned between the two processing chambers. 
           [0016]      FIG. 3A  is a general schematic depicting major components of the broken wafer recovery system according to an embodiment of the invention. 
           [0017]      FIG. 3B  is a general schematic depicting major components of the broken wafer recovery system according to another embodiment of the invention. 
           [0018]      FIG. 4  is a general schematic depicting further elements of the broken wafer recovery system shown in  FIGS. 3A and 3B . 
           [0019]      FIG. 5  illustrates a susceptor that can be used for processing substrates in plasma processing chambers. 
       
    
    
       [0020]    The invention is described herein with reference to particular embodiments thereof, which are exemplified in the drawings. It should be understood, however, that the various embodiments depicted in the drawings are only exemplary and may not limit the invention as defined in the appended claims. 
       DETAILED DESCRIPTION 
       [0021]    Various embodiments of the present invention provide apparatus and method for recovering pieces of wafers that were broken during the fabrication of, e.g., semiconductor integrated circuits, solar cells, flat panel displays, LED&#39;s etc. Embodiments of the invention are particularly useful for systems that utilize trays to transport and/or process wafers. 
         [0022]      FIG. 1A  illustrates example of a processing system that can be used to implement embodiments of the invention. It should be appreciated that other architectures and other systems can be used to implement the invention, and that the system shown in  FIG. 1A  is provided only as an example. For simplicity of explanation, only a single processing chamber  100  is illustrated, situated at one end of a simple linear system. In this embodiment, the processing chamber is a plasma processing chamber such as, for example, a PECVD or PVD processing chamber. One vacuum valve,  102 , is provided on the side of the chamber  100 , to enable introduction of trays  104  into the chamber  100 . A loadlock chamber  110  is provided on the side of chamber  100 , and vacuum valve  112  is provided at the entry of loadlock  110 . A loading chamber  120 , also referred to as factory interface, is provided at the entry side of loadlock chamber  110 , and is used to load trays  104  for processing, and unload processed wafers from the system. 
         [0023]    The flow of wafers illustrated in  FIG. 1A  will now be described in further details, starting with wafers loaded on the right side of the system. A tray  104  with substrates is loaded into loading chamber  120 . Notably, the tray may remain within the system and wafers loaded onto the tray within the system, or the tray may be loaded outside the system and brought to and loaded onto loading chamber  120 . The tray  104  may carry, for example, 64 substrates arranged in a two-dimensional array. The tray is then introduced into loadlock  110 , gate valves  102  and  112  are closed, and vacuum pump is energized to bring the loadlock  110  to a vacuum level matching or sufficiently close to that of chamber  100 . Then valve  102  is open and the tray is moved into the chamber for processing. That is, the wafers remain on the tray  104  while they are processed in chamber  100 . After processing is completed, the reverse operation is performed to remove the tray  104  from the chamber  100  and from the loadlock  110 , so as to remove the processed wafers and load fresh wafers for processing. 
         [0024]      FIG. 1B  depicts a similar system as that of  FIG. 1A , and similar elements to those shown in  FIG. 1A  are identified with similar reference numerals. In the embodiment of  FIG. 1B , the tray  104  does not move into the loadlock  110 . Rather, in the embodiment of  FIG. 1B , in loading chamber  120  the wafers are removed from the tray  104  and loaded onto one of specially designed wafer hangers  118  or  119 . The loaded hanger, say  118 , is then moved into loadlock chamber  110  and the valve  112  is then closed. A vacuum is then drawn in loadlock chamber  110 . Once the proper vacuum level is reached, valve  102  is opened and the wafer hanger moves into processing chamber  100 , wherein the wafers are removed from the wafer hanger and placed onto a susceptor  108 . The wafer hanger is then removed from the processing chamber  100 , back to the loadlock chamber  110 , and the valve  102  is closed. The processing chamber  100  is then energized to process the substrates that are in the chamber. 
         [0025]    Meanwhile, concurrent with the above processing, the other wafer hanger  119  is positioned in the loading chamber  120  and is loaded with new substrates. The loaded hanger  119  is then moved into the loadlock  110 , valve  112  is closed, and vacuum is drawn. When processing in chamber  100  is completed, valve  102  is opened and wafer hanger  118  is moved from loadlock  110  into chamber  100  so as to collect the processed substrates, and hanger  119  is moved from loadlock chamber  110  into chamber  100 , so as to deposit its new substrates for processing in chamber  100 . When both hangers have been removed back into loadlock  110 , the valve  102  is closed, and chamber  100  is energized for processing of the new wafers. The loadlock  110  is then vented to atmospheric pressure, upon which valve  112  is then opened and hanger  118  is moved into loading chamber  120 , to unload its processed wafers and load new substrates for processing. 
         [0026]      FIG. 2A  is a general schematic depicting major components of a system architecture according to an embodiment of the invention, showing the broken substrate recovery system installed over the factory interface of the system shown in  FIG. 1A . In  FIG. 2A , elements that are similar to those shown in  FIG. 1A  are identified with similar reference numeral, except that they are in the 2xx series. In  FIG. 2A , loading chamber  220  is fitted with a first sensing mechanism,  244 , which receives signals from controller  205 , once a new set of wafers have been received by the load chamber, to detect breakage of wafers on trays  204  entering and/or exiting loadlock chamber  210 . In this embodiment, sensing mechanism  244  is a light sensor or a camera, which is positioned on the broken wafer recovery system described below. Also, a second sensing mechanism,  246 , is provided to detect broken wafers inside the processing chamber  100 . In this embodiment, sensing mechanism  246  is a camera coupled to image processor and a monitor of the controller  205 . In this embodiment camera  246  is positioned inside the loadlock  210  and is oriented to view the interior of chamber  200  when gate valve  202  is opened. An illumination source  232  may be provided for illuminating the area viewed by the sensing mechanism  246 . Illumination source  232  may be positioned inside the loadlock  210 , may be provided outside the processing chamber and illuminating the interior via a window  233 , etc. The image processor in controller  205  uses image processing program to determine whether a wafer has broken inside the chamber  200 , while the monitor of controller  205  enables an operator to confirm or override the image processor&#39;s determination. The monitor also enables the operator to designate wafers as broken when the image processor missed such breakage. 
         [0027]    The broken wafer recovery system shown in  FIG. 2A  has an x-motion gantry  250  which moves the y-motion gantry  252  in the x direction, as shown by the double-headed arrow marked X. The y-motion gantry moves a suction head  254  in the y direction, as indicated by the double-headed arrow marked Y. The suction head can also move vertically, as illustrated by the double-headed arrow marked Z. In this way, the suction head can be placed above any coordinate on tray  204 . When a broken wafer is identified in the process chamber  200 , the tray  204  is moved to the loading chamber  220 . Conversely, if the broken wafer is detected on incoming or outgoing wafer trays, the tray is held in the load chamber for broken wafer removal. The controller  205  moves the suction head to the location of the broken wafer, and energizes the suction pump  365  to remove the broken wafer from the tray. Sensing mechanism  244  then confirms successful removal of the broken wafer, and the system returns to operation. 
         [0028]      FIG. 2B  is a general schematic depicting major components of a system architecture according to an embodiment of the invention, showing the broken substrate recovery system installed over the factory interface of the system shown in  FIG. 1B . In  FIG. 2B , elements that are similar to those shown in  FIG. 1B  are identified with similar reference numeral, except that they are in the 2xx series. In  FIG. 2B , loading chamber  220  is fitted with a first sensing mechanism,  244 , which receives signals from controller  205 , once a new set of wafers have been received by the load chamber, to detect breakage of wafers on trays  204  entering and/or exiting loadlock chamber  210 . In this embodiment, sensing mechanism  244  is a light sensor, thru beam sensors, a camera, etc., which is positioned on the broken wafer recovery system described below. Also, a second sensing mechanism,  246 , is provided to detect broken wafers inside the processing chamber  200 . In this embodiment, sensing mechanism  246  is a camera coupled to image processor and a monitor of controller  205 . In this embodiment camera  246  is positioned inside the loadlock  210  and is oriented to view the interior of chamber  200  when gate valve  202  is opened. Illumination source  232  may be positioned inside the loadlock  210 , may be provided outside the processing chamber and illuminating the interior via a window  233 , etc. The image processor of controller  205  uses image processing program to determine whether a wafer has broken inside the chamber  200 , while the monitor of controller  205  enables an operator to confirm or override the image processor&#39;s determination. The monitor also enables the operator to designate wafers as broken when the image processor missed such breakage. 
         [0029]    The broken wafer recovery system shown in  FIG. 2B  has an x-motion gantry  250  which moves the y-motion gantry  252  in the x direction, as shown by the double-headed arrow marked X. The y-motion gantry moves a suction head  254  in the y-direction, as indicated by the double-headed arrow marked Y. The suction head can also move vertically, as illustrated by the double-headed arrow marked Z. In this way, the suction head can be placed above any coordinate over tray  204 . When a broken wafer is identified, the suction head is moved to the location of the broken wafer, and a suction generator is energized to remove the broken wafer from the tray. Sensing mechanism  244  then confirms successful removal of the broken wafer, and the system returns to operation. 
         [0030]    Additionally, in the embodiment of  FIG. 2B  hanger  219  is equipped with implements to remove the susceptor  208  from within the chamber  200  and move it to the loading chamber  220 . When a image processor or the operator identifies a broken wafer inside the processing chamber  200 , hanger  219  is moved into the processing chamber  200  and engages the susceptor  208 . It then transports the susceptor  208  to the loading chamber  220 . At loading chamber  220  the suction head is moved to the location of the broken wafer and a suction generator is energized to remove the broken wafer from the susceptor  208 . Sensing mechanism  244  then confirms successful removal of the broken wafer, and the system returns to operation. 
         [0031]    According to an embodiment of the invention, when image processor utilizes an image of sensor  246  to indicate that a wafer has been broken on the susceptor  208 , the hanger  219  is used to engage the susceptor and bring it to sensor  244  for a second inspection. If sensor  244  also indicates that the wafer is indeed broken, then the hanger can be used to move the susceptor to station  220  for removing the broken pieces. 
         [0032]    According to another embodiment, the system of  FIG. 2B  has sensor  244 , but does not have sensor  246 . According to this embodiment, when a hanger is moved into the loadlock with fresh wafers, sensor  244  is used to record each location on the hanger which is occupied by a wafer. Then, when the hanger is sent back to the chamber to remove the processed wafers, the sensor  244  is again used to check whether all of the locations on the hanger that were previously occupied by a wafer are still occupied. If not, this is an indication that the wafer broke and is still inside the chamber. The hanger is then sent to retract the susceptor and deliver it to the loading chamber  220  to use the suction head to remove the broken wafer from the susceptor. 
         [0033]      FIG. 2C  illustrates another embodiment, showing a first processing chamber  200  and a second processing chamber  201 . Positioned between the first and second processing chambers is a flipping station  221 . This configuration is advantageous when chamber  210  is used to process one surface of the wafers, and chamber  201  is used to process the other side of the wafers. Therefore, after processing the wafers in the first chamber  200 , the tray  204  (or hanger) is moved to flipping station  221 , where the wafers on the tray  204  are flipped. The tray  204  then moves into the second chamber  201  for processing. When processing is completed in the second chamber, the tray is moved to unloading chamber  226 . Note that the flipping station  221  is in atmosphere, so that loadlocks  216  and  222  are provided on either side of it, which are shown abbreviated in  FIG. 2C . Also, loadlock  223  is provided between processing chamber  201  and unloading chamber  226 . 
         [0034]    In this example, the broken wafer recovery system is provided on the flipping station  221 . The broken wafer recovery system can be in the form of those described with respect to  FIGS. 2A and 2B  above. As with the previous examples, various sensors, here sensors  244 ,  246  and  248 , communicate with controller  205  to identify breakage of wafers. For example, if any of sensors  244 ,  246  or  248  detects a broken wafer, the tray  204  is moved to the flipping mechanism and the suction head  254  is used to remove the broken wafer from the tray. Sensor  248  can be used to verify complete removal of the broken wafer from the tray, before the wafers are flipped and the tray proceeds into chamber  201 . 
         [0035]      FIG. 3A  is a general schematic depicting major components of the broken wafer recovery system according to an embodiment of the invention. The broken wafer recovery system shown in  FIG. 3A  may be used in any of the embodiments shown above, or in other main-frame, linear, or other system architectures. The recovery system includes a suction head  362  and a mechanism enabling placement of the suction head  362  anywhere above a tray  304  (or a hanger or a susceptor, as described above). In the embodiment of  FIG. 3A , the placement mechanism includes a first gantry  364  and a second gantry  366  mounted onto frame  360 . The frame  360  may be the frame of the loading chamber, the flipping station, etc. The first gantry  364  moves the suction head  362  in one linear direction, say X direction, and the second gantry  366  moves the suction head  366  in a linear direction perpendicular to the first gantry, i.e., Y direction. This is shown by the double-headed arrows in  FIG. 3A . Also illustrated by a vertical double-headed arrow is the capability to move the suction head  362  in a vertical, i.e., z-direction, to lower and retract the suction head from the tray. A flexible house  368  couples the suction head  362  to the suction pump  365 . 
         [0036]    Another feature illustrated in  FIG. 3A  is the park and disposal station  370 . In this embodiment, when the suction head is not used, it is parked on the station  370 . Also, once the suction head removes broken pieces of a wafer, illustrated as broken wafer  372 , the suction head is moved to the station  370  and any residual wafer pieces are disposed into the station  370  once vacuum is removed from the suction head. 
         [0037]      FIG. 3B  is a general schematic depicting major components of the broken wafer recovery system according to another embodiment of the invention. The embodiment shown in  FIG. 3B  is similar to that of  FIG. 3A , except that in  FIG. 3B  an (r,□) arrangement is used for the placement mechanism, rather than an (x,y) arrangement. That is, rather than moving the suction head  362  using orthogonal linear directions (i.e., Cartesian coordinates), in the embodiment of  FIG. 3B  an angular motion about pivot  374 , together with linear motion along arm  376 , are used to place the suction head at the proper location, using polar coordinates. 
         [0038]      FIG. 4  is a general schematic depicting further elements of the broken wafer recovery system shown in  FIGS. 3A and 3B . Specifically,  FIG. 4  illustrates some details of the suction head  462 . As shown in  FIG. 4 , a hood  469  is mounted at the inlet of the suction head  462 . Inside the hood are several retractable pins  480 . The pins are used to break the wafer into small pieces that can be easily removed by the suction head and will not get stuck in the suction head or hose leading to the pump. The pins  480  are connected to a common frame  486 , through holes  484  provided in the hood  469 . The common frame  486  is retractable by the retracting mechanism  488 . 
         [0039]      FIG. 4  also illustrate set back extensions  481 , which ensures that the hood  469  does not fully contact or is sealed to the tray, susceptor or hanger. This ensures that there&#39;s sufficient air flow into the inlet to enable proper suction to remove the broken pieces. This also reduce thermal conductance to the hood, especially since if the tray or susceptor is moved out after processing it may be as hot as 300° C. With the set back extensions  481 , the hood is kept from heating up by contacting the tray or susceptor. 
         [0040]      FIG. 5  illustrates a susceptor that can be used for processing substrates in systems such as those illustrated above. The susceptor  508  is basically in the form of a plate having plurality of seats  591  for wafers. At the center of each seat  591 , a hole  593  is provided to enable a lift pin to lift the substrate. In this embodiment, the lift pins do not engage the wafer directly. Rather, a puck  597  is seated inside a puck seat  595  that is provided inside the lift pin hole  593 . The lift pin engages the puck, and as it lifts the pucks, it engages and lifts the wafer. 
         [0041]    When the broken wafer removal system is fitted into a system utilizing the susceptor of  FIG. 5 , provisions must be made to avoid sucking the puck when removing broken wafer. According to one embodiment, the pins  480 , shown in  FIG. 4 , are made to engage the puck and hold it in place prior to energizing the suction pump. In such configuration the pins serve dual purpose: they are used to break the wafer to smaller pieces when needed and also to hold the puck during suction. 
         [0042]    While the invention has been described with reference to particular embodiments thereof, it is not limited to those embodiments. Specifically, various variations and modifications may be implemented by those of ordinary skill in the art without departing from the invention&#39;s spirit and scope, as defined by the appended claims. Additionally, all of the above-cited prior art references are incorporated herein by reference.