Patent Document

BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention generally relates to semiconductor device fabrication, and more particularly, to an object handling system and apparatus for moving objects through a pressure sensitive system.  
           [0003]    2. Related Art  
           [0004]    Specialized wafer processing systems used to process semiconductor wafers into electronic devices is well known. Because floor space in a semiconductor fabrication clean-room and equipment area is typically scarce and costly, it is highly desirable to have a wafer processing system which occupies minimal floor space. One solution is to have a vertically oriented wafer processing system, which has vertically mounted modules or chambers, because such a system can be operated in a small contiguous area.  
           [0005]    A vertically oriented wafer processing system typically employs a robot to automate the movement of wafers between the vertically arranged modules. In most of these types of systems, the robot is mounted atop a post-like drive member inside a transfer chamber. The post-like drive member moves in and out of the transfer chamber to move the robot in a vertical direction within the processing system. In this example, the movement of the robot and post-like drive member can be compared to the movement of a piston. Unfortunately, as the post-like drive member operates the space (i.e., volume) being occupied by the robot increases as the robot is raised and decreases as the robot is lowered. The variableness of the occupied volume can cause pressure changes to occur in the processing system.  
           [0006]    Pressure changes can be undesirable in the processing system, since some processing recipes are optimized to work at a specific pressure (and/or temperature). Pressure changes can also create contamination control problems, since a pressure imbalance may cause contaminants to more readily enter the processing system.  
           [0007]    For these reasons, what is needed is a system and apparatus for handling and transporting an object in a processing system, and which does not adversely influence the pressure environment within the processing system.  
         SUMMARY  
         [0008]    In accordance with the present invention, a handling system and apparatus can operate in a processing system having a pressurized environment, without adversely influencing or causing pressure changes. In one example of the present invention, the handling system and apparatus can be used in a semiconductor processing system having vertically mounted multiple modules (i.e., vertically integrated chambers), which can include reactors, load locks, and cooling stations, since these processing systems can require substantial vertical movement of the handling system.  
           [0009]    As described in greater detail below, the handling system of the present invention includes a handling mechanism operatively coupled to a robotic device, mounted to a driver member. The driver member is slidably secured at opposite ends to a top and a bottom portion of a chamber in which it operates. In this arrangement, the handling mechanism, the robotic device, and the driver member are fully enclosed in the chamber during a typical operation. In one example, the vertical movement allows the handling mechanism to access the vertically mounted reactors, load locks, cooling stations, and other modules of the semiconductor processing system. Once the robotic device reaches a desired vertical position, the handling mechanism can extend in the horizontal plane to grab or pick-up an object and can then be rotated to move the object to an alternative location.  
           [0010]    Accordingly, the handling system consistently occupies a predetermined volume of space within the chamber. Thus, as the handling system is raised, lowered, extended or rotated to transport an object, the volume of space occupied by the handling system remains constant. Accordingly, for a given pressure sensitive operation occurring within the processing system, movement of the handling system of the present invention causes substantially little or no pressure change or fluctuation.  
           [0011]    The present invention provides a simple design with numerous advantages, especially for semiconductor wafer processing systems. For example, since the volume of space in the processing system occupied by the handling system is constant, pressure fluctuation caused by movement of the handling device is reduced or eliminated. The reduction or elimination of pressure fluctuations causes fewer disturbances to the processing operations. The configuration of the present invention also lowers the opportunity for particle migration into the processing system, which can cause contamination of the wafer processing operation. Thus, various pressure sensitive wafer processing recipes can be applied more accurately and more uniformly to wafers.  
           [0012]    Other uses, advantages, and variations of the present invention will be apparent to one of ordinary skill in the art upon reading this disclosure and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIGS. 1A and 1B show a side view and a top view, respectively, of a wafer processing system in accordance with the invention;  
         [0014]    [0014]FIG. 2 is a simplified diagram of a wafer handling system in accordance with the present invention;  
         [0015]    [0015]FIGS. 3A and 3B are simplified illustrations of alternative embodiments in accordance with the present invention; and  
         [0016]    FIGS.  4 A- 4 F are simplified illustrations of side views of the wafer processing system shown in FIG. 1A illustrating the movement of a wafer from a carrier in a load lock to a reactor using the wafer handling system of FIG. 2. 
     
    
     DETAILED DESCRIPTION  
       [0017]    Although the system and apparatus of the present invention may be used as part of any pressure sensitive system, the embodiments described below generally disclose a semiconductor processing system. It should be understood that these embodiments are exemplary and their disclosure is not intended to limit the invention thereby.  
         [0018]    [0018]FIGS. 1A and 1B show a side view and a top view, respectively, of a wafer processing system  100 , which provides a representative environment for the use of the present invention. A processing system of the type of system  100  is fully disclosed and described in commonly assigned U.S. patent application Ser. No. 09/451,677, filed Nov. 30, 1999, which is herein incorporated by reference for all purposes. System  100  includes a loading station  10 , a load lock  12 , a transfer chamber  20 , a robot  21 , reactors  30  and  40 , and a cooling station  60 . Loading station  10  has platforms  11 A,  11 B, and  11 C for supporting and moving wafer carriers, such as a wafer carrier  13 , up into load lock  12 . While three platforms are used in this embodiment, the invention is not so limited. Two platforms can also be used as can additional platforms to increase throughput. Carrier  13  is a removable wafer carrier which can carry up to 25 wafers at a time. Other types of wafer carriers, including fixed wafer carriers, can also be used. Wafer carriers are loaded onto platforms  11 A,  11 B, and  11 C either manually or by using automated guided vehicles (“AGV”).  
         [0019]    While the movement of a wafer carrier into load lock  12  is illustrated herein using carrier  13  on platform  11 A as an example, the same illustration applies to the movement of other wafer carriers using platforms  11 B and  11 C. Further, because platforms  11 A,  11 B, and  11 C are structurally and functionally the same, any reference to platform  11 A also applies to platforms  11 B and  11 C.  
         [0020]    The rotational movement of platforms  11 A,  11 B, and  11 C into position  2  minimizes the floor space occupied by loading station  10 . Loading station  10  occupies just enough area to accommodate the number of platforms used, for example, three.  
         [0021]    Referring to FIG. 1A, in this embodiment, reactors  30  and  40  are rapid thermal processing (“RTP”) reactors. However, the invention is not limited to a specific type of reactor and may use any semiconductor processing reactor such as those used in physical vapor deposition, etching, chemical vapor deposition, and ashing. Reactors  30  and  40  may also be of the type disclosed in commonly assigned U.S. patent application Ser. No. 09/451,494, filed Nov. 30, 1999, entitled “Resistively Heated Single Wafer Furnace,” which is incorporated herein by reference in its entirety. Reactors  30  and  40  are vertically mounted to save floor space. Process gases, coolant, and electrical connections are provided through the rear end of reactors  30  and  40  using interfaces  33 .  
         [0022]    A pump  50 , shown in FIG. 1A, is provided for use in processes requiring vacuum. In the case where the combined volume of reactors  30  and  40  less than the combined volume of load lock  12 , cooling station  60 , and transfer chamber  20 , a single pump  50  may be used to pump down the entire volume of system  100  (i.e. combined volume of load lock  12 , cooling station  60 , transfer chamber  20 , reactor  30 , and reactor  40 ) to vacuum. Otherwise, additional pumps such as pump  50  may be required to separately pump down reactors  30  and  40 .  
         [0023]    After wafer  22  is processed in a well known manner inside reactor  30  (or  40 ), gate valve  31  opens to allow robot  21  to move wafer  22  into cooling station  60  (FIG. 1A). Because newly processed wafers may have temperatures upwards of 200° C. and could melt or damage a typical wafer carrier, cooling station  60  is provided for cooling the wafers before placing them back into a wafer carrier in load lock  12 . In this embodiment, cooling station  60  is vertically mounted above load lock  12  to minimize the floor space area occupied by system  100 . Cooling station  60  includes shelves  61 , which may be liquid-cooled, to support multiple wafers at a time. While two shelves are shown in FIG. 1A, of course, a different number of shelves can be used, if appropriate, to increase throughput.  
         [0024]    Subsequently, wafer  22  is picked-up from cooling station  60  and replaced to its original slot in carrier  13  using robot  21 . Platform  11 A lowers from load lock  12  and rotates out of position to allow another platform to move a next wafer carrier into load lock  12 .  
         [0025]    [0025]FIG. 2 shows an embodiment of transfer chamber  20 , which includes wafer handling system  80 , an alternative to robot  21  (FIG. 1A). As described in more detail below, wafer handling system  80  is disposed in wafer transfer chamber  20  to transport wafer  22  from a wafer carrier to a reactor or other processing chamber. Wafer handling system  80  includes a wafer handling mechanism  82  and a driver member  84 . Wafer handling mechanism  82  can include a robot arm  86  operably coupled to a linear movement actuator  88 . Typically, at the end of robot arm  86  is an end effector  90  for picking up and/or grabbing wafer  22 .  
         [0026]    In one embodiment, driver member  84  is arranged, such that opposing ends of driver member  84  are held in a sliding relationship with transfer chamber  20 . Advantageously, by mounting driver member  84  in sliding arrangement with the top and bottom opposed ends of transfer chamber  20 , the need for additional linear guides, typically used to prevent wobble and increase stability, are reduced or eliminated. Since driver member  84  is supported at both ends, driver member  84  can be made relatively narrow and still remain stiff. The actual specification for drive member  84  is determined by the actual application (i.e., the size of the process chamber and handling mechanism). For example, in one embodiment, driver member  84  may have a diameter of between about 10 mm and 50 mm; preferably 20 mm. Accordingly, driver member  84  can be made of any high strength structural material, such as steel, aluminum and the like.  
         [0027]    In one embodiment, driver member  84  is a smooth cylindrical shaft that can be driven linearly in direction Z through bearings  92  to move driver member  84  up or down. In this embodiment, a top portion of driver member  84  is mounted through the top of transfer chamber  20  through a combination of a roller bearing  92  and a seal  95  (collectively “sealable bearing  92 ”) or similarly functioning bearing/seal combination that provides smooth linear translation in direction Z and smooth rotation in direction θ. A bottom portion of driver member  84  is similarly using roller bearing  92  mounted through the bottom of transfer chamber  20 . Bearings  92  are well known and the function of bearings is well understood by those of ordinary skill in the art. Seals  95  ensure that the internal environment of transfer chamber  20  and/or system  100  is unaffected by the movement of driver member  84 . Seals  95  can be any type of seal which does not expand and compress with a moving part being moved therethrough. For example, seals  95  can be o-rings, lip-seals, or t-seals, such as the type of seals available from Sierracin Corporation of Sylmar, Calif.  
         [0028]    As shown in FIG. 3A, a direction Z (i.e., vertical motion) motor/controller  94  (hereinafter “driver motor”), can be used to cause driver member  84  to move in the Z and θ directions. Drive motor  94  may be any typical drive motor, such as is available from Yaskawa Electric of Fukuoka, Japan. In this embodiment, driver motor  94  may be mechanically coupled to a lead screw or worm drive  96  via a belt or similarly conventional power transmission means. A collar  97  is operably coupled to lead screw  96 , and is attached to a corresponding collar  98 , which is fixedly attached to driver member  84 . As lead screw  96  rotates, collar  97  rides up (or down) on lead screw  96 , causing collar  98  to move driver member  84  up (or down). In this manner, handling mechanism  82  may be raised/lowered as much as desired, for example, between a range of about 250 mm or greater; preferably about 350 mm.  
         [0029]    Optionally, as shown in FIG. 3B, driver member  84   a  may be a threaded member, which can operate as a worm drive or lead screw drive. In this embodiment, driver motor  94   a  may be mechanically coupled directly to threaded driver member  84   a  via a belt system, a gear system or similarly conventional power transmission means. A collar  98   a  is operably coupled to handling mechanism  82 , such that as driver member  84   a  rotates θ, collar  98   a  rides up (or down), causing handling system  82  to move up (or down) in the Z direction.  
         [0030]    Movement of handling mechanism  82  in the horizontal direction is accomplished by extending robot arm  86  with end effector  90  attached thereto. End effector  90  can be made of any heat resistant material, such as quartz, for picking-up and placing wafer  22 . End effectors and robot arms are well known and their function well understood by those of ordinary skill in the art.  
         [0031]    Robot arm  86  and end-effector  90  are operably coupled to a linear movement actuator  88 . For example, the extension and retraction of robot arm  86  and end effector  90  along a straight line can be accomplished using a conventional belt and pulley arrangement operably coupled to a linear motor. In one embodiment, the entire handling mechanism  82  can rotate θ relative to driver member  84  using a rotation motor. The rotation and linear motors are available from Yaskawa Electric.  
         [0032]    [0032]FIGS. 4A to  4 F show side views of system  600  illustrating the movement of wafer  22  from carrier  13 , which is inside load lock  12 , to a reactor  30  (or  40 ). Once carrier  13  is inside load lock  12 , handling system  80  in transfer chamber  20  rotates and lowers towards load lock  12  (FIG. 4A). Handling mechanism  82  extends robot arm  86  and end-effector  90  to pick up wafer  22  from wafer carrier  13  (FIG. 4B). Robot arm  86  then retracts and rotates towards reactor  30  (FIGS. 4C and 4D). Drive motor  94  causes driver member  84  to elevate, which, in turn, causes wafer handling mechanism  82  to position wafer  22  in-line with reactor  30  (FIG. 4E). Robot arm  86  then extends, such that end-effector  90  places wafer  22  into reactor  30  (FIG. 4F). Robot arm  86  then retracts and, subsequently, the processing of wafer  22  begins.  
         [0033]    The description of the invention given above is provided for purposes of illustration and is not intended to be limiting. The invention is set forth in the following claims.

Technology Category: 5