Abstract:
Apparatuses and methods are provided for sealing a slit valve passage between two substrate processing chambers. A body with two openings to register with openings in the walls of the process chambers, and a passageway between them, houses a sealing member configured to extend and retract to block or open the passageway. The sealing member comprises a seal on one face that covers one opening, and a moveable lateral extension on the other face that braces against the other opening. The extension is actuated to contact the wall of the body, providing a bracing or sealing force to the seal on the other face of the sealing member. The sealing force may be adjusted by varying the gas pressure to the sealing member based on pressure conditions in the process chambers.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional patent application Ser. No. 60/892,511 (APPM/11888L), filed Mar. 1, 2007, which is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the present invention generally relate to a silt valve for interfacing between two vacuum chambers. 
         [0004]    2. Description of the Related Art 
         [0005]    In semiconductor, flat panel display, photovoltaic/solar panel, and other substrate processing systems, it is common to arrange vacuum chambers (i.e., load locks, transfer chambers, process chambers) in a cluster, in-line, or a combination of cluster/in-line arrangements to process substrates. These systems may process substrates in a single or batch substrate fashion. During processing, substrates may be transferred to and from chambers in which vacuum must be maintained or established. To allow access to the inside of the chamber, and to enable vacuum operation, an opening in the shape of a slit is frequently provided to accommodate the substrate being processed. The opening is usually sealed by a door that retracts to open the slit and moves into position covering the slit to seal the chamber. 
         [0006]    At each interface between two vacuum chambers, a slit valve assembly may be present. A slit valve door may be movably actuated to open or close the slit valve passageway. The slit valve passageway, when open, permits one or more substrates to be transferred between the two vacuum chambers through the slit valve. When the slit valve passageway is closed by a slit valve door, substrates may not be transferred between the two vacuum chambers through the slit valve passageway and the two vacuum chambers are isolated from each other. For example, one of the vacuum chambers may be a process chamber which requires isolation from other chambers, which may be other process chambers or a transfer chamber. 
         [0007]    As the substrate size for manufacturing flat panel display grows, the manufacturing equipment for these substrates becomes larger in size as well. Accordingly, the door or gate that isolates one vacuum chamber (or load lock chamber) from another becomes larger or, specifically, longer because the slot opening between the two chambers has to become longer to accommodate the large width of the substrate passing through the slot opening. The increasing length of the door poses technical challenges for obtaining a good isolation seal between the two chambers, which is maintained by an elastomeric seal disposed around the slot opening between the door and a chamber wall. 
         [0008]    Therefore, there is a need for a slit valve door capable of sealing chambers used to process large area substrates. 
       SUMMARY OF THE INVENTION 
       [0009]    Embodiments described herein provide a slit valve assembly, comprising a slit valve body comprising a first wall and a second wall; and a slit valve door disposed within the slit valve body, the slit valve door comprising a sealing surface facing the first wall; a bracing surface substantially parallel to the sealing surface facing the second wall, wherein the bracing surface may extend away from the sealing surface; and a gas supply configured to vary a sealing force on the sealing surface. 
         [0010]    Other embodiments provide an apparatus for coupling two vacuum chambers together, comprising a sealing member comprising a first face and a second face; a seal coupled to the first face; a moveable extension coupled to the second face; one or more lift rods coupled to the sealing member, each lift rod comprising a conduit in communication with the moveable extension; and a gas supply of adjustable pressure in communication with one or more of the conduits. 
         [0011]    Other embodiments provide a method, comprising disposing a slit valve door between a first chamber and a second chamber, the slit valve door having a sealing surface and a bracing surface substantially parallel to the sealing surface; supplying a gas between the sealing surface and the bracing surface to close the slit valve door; and adjusting a distance between the sealing surface and the bracing surface to control sealing force. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0013]      FIGS. 1A-1C  are schematic cross-sectional views of a slit valve assembly according to one embodiment of the invention. 
           [0014]      FIG. 2  is a schematic control diagram according to one embodiment of the invention. 
       
    
    
       [0015]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
       DETAILED DESCRIPTION 
       [0016]    For ease of Illustration, embodiments of the present invention will be described in reference to  FIGS. 1A-1C  with the vacuum chamber  100   a  comprising a transfer chamber and the vacuum chamber  100   b  comprising a process chamber. Exemplary transfer chambers and process chambers are available from AKT™, a subsidiary of Applied Materials, Inc., located in Santa Clara, Calif. Slit valve assemblies are also disclosed in U.S. Pat. No. 7,086,638 assigned to Applied Materials, Inc., and are all incorporated by reference to the extent they are not inconsistent with this disclosure. It is contemplated that the invention is equally applicable between any two vacuum chambers, including those produced by other manufacturers. 
         [0017]      FIGS. 1A-1C  are schematic cross-sectional views of one embodiment of two vacuum chambers  100   a  and  100   b  coupled together by a slit valve assembly  102 . The slit valve assembly  102  includes a slit valve body  116  that defines a slit valve passageway  106 , and a sealing member  104  for sealing the slit valve passageway  106 . The slit valve body  116  has a first wall  107 A and a second wall  107 B, embodying two internal surfaces of the slit valve body  116 . A lift mechanism  108 , such as a pneumatic, belt-driven, screw-driven, or other suitable mechanism, is coupled to the sealing member  104  by one or more lift rods  109  to raise the sealing member  104  to block the slit valve passageway  106  or to lower the sealing member  104  to leave the slit valve passageway  106  open. 
         [0018]    The sealing member  104 , which may be a slit valve door, further includes a first face  118 , which may be a sealing surface, facing the internal surface embodied by the first wall  107 A and a second face  120  substantially parallel to the first face  118  facing the internal surface embodied by the second wall  107 B. The sealing member  104  may further include a moveable extension  112 , which may be a bracing member, coupled to the second face  120 . The extension  112  has a bracing surface  122  substantially parallel to the first face  118  and the second face  120 , and facing the second wall  107 B, that is configured to extend away from the first face  118  when extension  112  is operated. As the bracing surface  122  extends away from the first face  118 , it comes into contact with the second wall  107 B. As the bracing surface  122  is extended further, it pushes the first face  118  to contact the first wall  107 A. 
         [0019]    A seal  110 , which may be an o-ring, sealing pad, or gasket, seals the slit valve passageway  106  when the first face  118  contacts the first wall  107 A. In this embodiment, the extension  112  expands laterally to provide a sealing force between the seal  110  and the first wall  107 A, and retracts to create space between the first face  118  and the first wall  107 A, and the bracing surface  122  and the second wall  107 B, thus allowing vertical movement of the sealing member  104  by the lift mechanism  108 . 
         [0020]    The bracing surface  122  and the first face  118  cooperatively define an internal cavity (not shown) inside the sealing member  104 . An external actuator  114  is coupled to the moveable extension  112  to laterally expand or laterally retract the extension  112 , thus moving the bracing surface  122  with respect to the first face  118 . In one embodiment, the external actuator  114  is a pneumatic actuator which applies pressure to the internal cavity inside the sealing member  104  to expand the moveable extension  112  and releases the pressure to retract the extension  112 . A fluid, such as a gas, is provided to the internal cavity through one or more conduits  124  that are provided through one or more of the lift rods  109  and are in communication with the internal cavity and the external actuator  114 . In an alternate embodiment, the external actuator  114  may be hydraulically operated, providing a liquid to the internal cavity through the conduits  124 . 
         [0021]    In  FIG. 1A , the sealing member  104  is moveably disposed in a lowered position to leave the slit valve passageway  106  open. In  FIG. 1B , the sealing member  104  is moveably disposed in a raised position in which the extension  112  is retracted. In  FIG. 1C , the extension  112  of the sealing member  104  is expanded to provide a sealing force between the seal  110  and the first wall  107 A of the slit valve passageway  106 . 
         [0022]    In certain instances, different sealing force levels will be applied to the sealing surface by supplying gas at varying pressures to the sealing member. The need for different sealing force levels may arise from changing process conditions in the chambers to be sealed. A sealing force level that is too low may cause leakage of gas or air from the environment (i.e., if the chamber is opened up to air for maintenance) through the slit valve passageway. A sealing force level that is too high may damage the slit valve assembly. For example, if the sealing force level is too high there may be metal-to-metal contact between slit valve assembly components causing undesirable particle formation. 
         [0023]    Typically, in normal operation, both process chambers will be at vacuum for processing of substrates. In this instance, a “low” sealing force/pressure is applied to the lateral member. From time-to-time, one process chamber may need to be vented to atmosphere for maintenance thereof while the other chamber remains at vacuum. For example, a transfer chamber may be in operation to transfer substrates to other chambers, while a process chamber coupled to the transfer chamber via a slit valve assembly is at atmospheric pressure. In this instance, a “high” sealing force/pressure is applied to the lateral member to help prevent the leaks from the high pressure chamber to the low pressure chamber. From time-to-time, the transfer chamber may need to be vented to atmosphere for maintenance thereof while the process chamber remains at vacuum. In this instance, a “low” sealing force/pressure is applied to the lateral member because the pressure of the transfer chamber adds to the sealing force of the lateral member (i.e., the atmospheric pressure of the transfer chamber presses against the lateral member helping to urge the seal against the slit valve passageway wall). 
         [0024]    In one embodiment, the pressure applied to extend the lateral member is set at a high pressure setting, such as about 35 psi or above, whenever the process chamber is at atmosphere pressure. The pressure setting to extend the lateral member is set at a low pressure setting, such as about 25 psi or below, whenever the process chamber is at vacuum pressure (such as 300 torr or below). The pressure settings are summarized in the below Table 1. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Transfer 
                 Process 
                   
               
               
                   
                 Chamber 
                 Chamber 
                 Pressure Applied to the Lateral 
               
               
                   
                 Condition 
                 Condition 
                 Member 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Case 1 
                 Vacuum 
                 Vacuum 
                 Low 
               
               
                 Case 2 
                 Vacuum 
                 Atmosphere 
                 High 
               
               
                 Case 3 
                 Atmosphere 
                 Vacuum 
                 Low 
               
               
                 Case 4 
                 Atmosphere 
                 Atmosphere 
                 High 
               
               
                   
               
             
          
         
       
     
         [0025]    In certain embodiments, the process chamber pressure condition may be monitored and pressure applied to the sealing member may be automatically adjusted.  FIG. 2  is a schematic control diagram illustrating a control system for automatically adjusting the pressure applied to a bracing member of a slit valve door such as that described above based upon the process chamber pressure. Gas is supplied from gas source  204 , which may comprise one or more gas canisters, to actuate a bracing member of sealing member  214 . A pressure regulator  202  is provided to reduce the supply pressure of the gas going to the sealing member  214  to enable application of low sealing force. Valves  206  and  208  may be operated to apply low or high sealing force. Valve  208  may be closed and valve  206  opened to apply low sealing force, and vice-versa to apply high sealing force. Pressure sensors  212   a  and  212   b  may be used to sense pressure in chambers  200   a  and  200   b , respectively. A selector  210 , which may be a control device, may operate valves  206  and  208  in response to pressures in the respective chambers. When chamber  200   a  is at high pressure and chamber  200   b  at low pressure, selector  210  may close valve  206  and open valve  208  to apply high sealing force to the bracing member. When chamber pressures call for low sealing force, as delineated in the table above, selector  210  may open valve  206  and close valve  208  to apply low sealing force to the bracing member. Applied to the scenario described above, atmospheric pressure in the process chamber will open valve  208  and close valve  206  to apply a high pressure to the bracing member. Vacuum in the process chamber opens valve  206  and closes valve  208  and a low pressure is provided to the bracing member. In an alternate embodiment, valves  206  and  208  may be replaced by a 3-way valve switchable between two sources. [ 0024 ] Providing a low pressure to the bracing member when the transfer chamber is at atmospheric pressure and the process chamber under vacuum reduces metal-to-metal contact in the slit valve assembly. Providing a high pressure to the bracing member when the transfer chamber is under vacuum and the process chamber is at atmospheric pressure provides an improved sealing force between the seal and the slit valve passageway wall and reduces leakage therethrough. Thus, using a plurality of gas sources at different pressures, embodied alternately as a gas at ambient pressure selectably controlled by a pressure regulator or as multiple gas supplies at different pressures, and a selector for applying one source at a time to the conduit in the bracing member, enables the slit valve assembly to maintain an operable seal as process conditions change. 
         [0026]    In operation, embodiments of the present invention provide a method of sealing openings at one end of a passageway, such as a slit valve passageway, between two vacuum chambers. A sealing member such as the sealing member  104  of  FIGS. 1A-1C , having a seal on one face and a lateral member projecting from the other face, is disposed in a slit valve passageway between a first chamber and a second chamber by a lifting mechanism. The lateral member may be configured as described in the above embodiment, depicted in  FIGS. 1A-1C . The sealing member, having a sealing surface and a bracing surface substantially parallel to the sealing surface, is positioned such that the sealing surface covers a first opening in a wall of the first chamber at one end of the passageway, while the lateral member having the bracing surface covers a second opening in a wall of the second chamber at the other end of the passageway, while the seal covers an opening at the other end of the passageway. The lateral member is extended to adjust the distance between the sealing surface and the bracing surface, such that the bracing surface contacts the wall area surrounding the second opening and transmits a bracing or sealing force to the seal disposed in the sealing surface. The seal impinges the wall area surrounding the first opening of the passageway, thus sealing the slit valve passageway at both ends. The lateral member may be extended using pressurized gas applied through a conduit in the sealing member to the inside of the sealing member to force the lateral member outward. When an open passageway is desired, the lateral member may be retracted and the sealing member lowered. 
         [0027]    While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.