Abstract:
The method of preserving the anodized finish of a barrier door of a process module includes bonding a seal to a metal surface, anodizing the metal surface, and then using a CNC machine to polish the metal surface without damaging the seal. The metal surface is polished by traversing a polishing path along the metal surface with a polishing head maintaining frictional contact with the metal surface. The integrity of the seal is preserved by bounding the polishing head to skirt the edge of the seal by following the polishing path.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 61/595,719 filed Feb. 7, 2012, entitled “METHOD OF POLISHING A METAL SURFACE OF A BARRIER DOOR OF A GATE VALVE USED IN A SEMICONDUCTOR CLUSTER TOOL ARCHITECTURE.” 
    
    
     TECHNICAL FIELD 
     The present specification generally relates to methods of polishing metal surfaces, and more particularly to methods of polishing metal surfaces of barrier doors of gate valves used in semiconductor cluster tools. 
     BACKGROUND 
     In vacuum processing of thin film materials, such as in the manufacture of semiconductor devices, multiple processing modules are typically interfaced to permit transfer of wafers between the interfaced processing modules. The transfer of wafers between interfaced processing modules is typically accomplished with the help of transport modules, which typically move the wafers through slots or ports provided in the adjacent walls of the interfaced processing modules. Transport modules may be used in conjunction with a variety of processing modules, which may include, among others, semiconductor etching systems, material deposition systems, and flat panel display etching systems. The particular arrangement of transport modules and processing modules is frequently referred to as “cluster tool architecture.” 
     In semiconductor process cluster tool architecture, the pressure within the transport module may be different than the pressure within an adjacent processing module. A gate drive valve may be used to isolate the various modules to: minimize leaks between a transport module that is at a different pressure than a processing module; minimize leaks between modules during pressure varying transitions; or to seal off a processing module from a transport module during processing. 
     In order to isolate a particular module, a gate valve may include a seal plate and a barrier door that seals off the particular module when engaged by the barrier door. The barrier door may include a vacuum seal that extends about the periphery of the door and a surface finished barrier seal face. The seal plate may include a barrier seal and a vacuum seal face. When the barrier door engages the seal plate in order to isolate the particular module, the vacuum seal of the barrier door may engage the mating vacuum seal face of the seal plate and the barrier seal of the seal plate may engage the mating barrier seal face of the barrier door. The seal plate sealing surfaces may be integrated into the chamber design, thus not requiring a separate seal plate, and the seal surfaces would be the chamber housing surfaces. 
     The barrier door may be fabricated from a metal, such as aluminum, by a process that involves anodizing the barrier door. Yet, such barrier doors can be prone to microcrack of the anodized surface thereby compromising the electrical and corrosive resistance of the anodized surface. 
     Accordingly, a need exists for additional methods of preserving the anodized metal surface of gate valve barrier doors. 
     SUMMARY 
     The method of preserving an anodized finish on a metal surface of a barrier door for a gate valve in a process module is described. According to one embodiment, the method can include bonding a seal to the metal surface, anodizing the metal surface, and then polishing the seal surface. The seal surface is polished by traversing a polishing path along the seal surface with a polishing head maintaining frictional contact with the seal surface. The seal integrity is maintained by bounding the polishing head to skirt the edge of the seal by following the polishing path. By following the polishing path, the polishing head can polish the seal surface immediately adjacent to the seal without touching or damaging the seal. 
     According to another embodiment, the anodized finished is preserved by applying the high temperatures needed to vulcanizing an elastomer seal to the metal surface of a barrier door before the anodize process. The metal surface is anodized after vulcanization and the seal surface is polished. The seal surface is polished by traversing a polishing path along the seal surface with a polishing head maintaining frictional contact with the seal surface. The seal integrity is maintained by bounding the polishing head to skirt the edge of the seal by following the polishing path and polishing the seal surface immediately adjacent to the seal without touching or damaging the seal. 
     These and additional features provided by the embodiments described herein will be made more fully understandable in view of the following detailed description, in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments set forth in the drawings are illustrative and exemplary in nature and not intended to limit the subject matter defined by the claims. The following detailed description of the illustrative embodiments can be understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which: 
         FIG. 1  schematically depicts a semiconductor process cluster tool architecture that includes a transport module, a plurality of processing modules, and a plurality of valves, according to one or more embodiments shown and described herein; 
         FIG. 2  depicts a perspective view of one of the valves shown in  FIG. 1 , according to one or more embodiments shown and described herein; 
         FIG. 3  depicts a plan view of the interface between a transport module, a processing module, and a valve located between the transport module and processing module, according to one or more embodiments shown and described herein; 
         FIG. 4  depicts a plan view of the interface between a processing module and a process module barrier door according to one or more embodiments shown and described herein; 
         FIG. 5  depicts a perspective view of the processing module barrier door of the valve shown in  FIG. 3 , according to one or more embodiments shown and described herein; 
         FIG. 6  depicts a partial cross-sectional view along the  6 - 6  line of the processing module barrier door depicted in  FIG. 5 , according to one or more embodiments shown and described herein; and 
         FIGS. 7   a - c  depicts several paths the polishing head can follow along a metal surface, according to one or more embodiments shown and described herein. 
     
    
    
     DETAILED DESCRIPTION 
     In the present disclosure, the process of preserving an anodized metal surface involves curing the seal first, then anodizing the metal surface, and finally polishing the surface. Depending on the type of seal used, the curing process could require vulcanizing the vacuum seal to barrier door which requires high curing temperatures for an extended period of time (e.g., a pre-cure stage at temperatures of about 350° F. to about 370° F. for about five minutes and a final cure at temperatures about 400° F. for about 24 hours). The barrier door is then anodized. The final step of polishing can be accomplished via a computer numerical control (CNC) machine, polishing in an omni-directional direction, and using a polishing head. A method of polishing metal surfaces that require high temperature curing and anodized metal surfaces will be described in more detail herein. 
       FIG. 1  schematically depicts a typical semiconductor process cluster tool architecture  100  that includes a transport module  102 , a first processing module  106   a , and a second processing module  106   b . As depicted in  FIG. 1 , transport module  102  is coupled to the first processing module  106   a  through a first valve  104   a , which is located between the transport module  102  and the first processing module  106   a . Transport module  102  is also coupled to the second processing module  106   b  through a second valve  104   b , which is located between the transport module  102  and the second processing module  106   b.    
     In order to transfer a wafer from the first processing module  106   a  to the second processing module  106   b , for example, a robotic arm within transport module  102  may reach into the first processing module  106   a , pick up the wafer to be transported, and move the wafer through a slot or port in the adjacent wall of the first processing module  106   a , through an opening in the valve  104   a , through the interior of the transport module  102 , through an opening in the second valve  104   b , and finally through the adjacent wall of the second processing module  106   b . While the semiconductor process cluster tool architecture  100  depicted in  FIG. 1  includes two processing modules,  106   a  and  106   b , the semiconductor process cluster tool architecture  100  may include more than or less than two processing modules. 
     The first valve  104   a  typically functions to isolate the first processing module  106   a  and the transport module  102  from one another in order to minimize leaks when it is desirable to isolate the modules, e.g., during pressure varying transitions, or to seal off the first processing module  106   a  from the transport module  102  during processing in the first processing module  106   a . Similarly, the second valve  104   b  typically functions to isolate the second processing module  106   b  and the transport module  102  from one another in order to minimize leaks when it is desirable to isolate the modules, e.g., during pressure varying transitions, or to seal off the second processing module  106   b  from the transport module  102  during processing in the second processing module  106   b.    
     Still referring to  FIG. 1 , each of the first processing module  106   a  and the second processing module  106   b  may be individually optimized to perform various processing steps. By way of example, but not by way of limitation, the first processing module  106   a  and the second processing module  106   b  may be configured to perform semiconductor etching, material deposition, flat panel display etching, and/or sputtering. 
       FIG. 2  depicts a perspective view of the first valve  104   a  as shown in  FIG. 1 . The first valve  104   a  includes an actuator-driven mechanism  118  that is operatively connected to a shaft  116  that extends from a top of the actuator-driven mechanism  118  in a direction substantially perpendicular to the top of the actuator-driven mechanism  118 . The shaft  116  is mechanically coupled to a carrier  114 . A process module barrier door  110  and a transport module door  112  are affixed to opposing sides of the carrier  114 . 
       FIG. 3  depicts a plan view of the interface between the transport module  102 , the first processing module  106   a , and the first valve  104   a . The first valve  104   a  is positioned between the transport module  102  and the first processing module  106   a  of the semiconductor process cluster tool architecture  100 . 
     The first valve  104   a  includes a transport module wall  134 , a processing module wall  132 , a processing module barrier door  110 , a transport module door  112 , a carrier  114 , and a shaft  116 , an opening  136 P, and an opening  136 T. The opening  136 P is provided in the processing module wall  132  in order to permit wafers (not shown) to be transferred into and out of the first processing module  106   a . Similarly, the opening  136 T is provided in the transport module wall  134  in order to permit wafers (not shown) to be transferred into and out of the transport module  102 . The opening  136 P is generally rectangular in shape and is smaller in each dimension than the generally rectangular shape of the processing module barrier door  110 , which is provided for sealing the opening  136 P. The opening  136 T is also generally rectangular in shape and is smaller in each dimension than the generally rectangular shape of the transport module door  112 , which is provided for sealing the opening  136 T. 
     In some embodiments, the corners of the processing module barrier door  110 , the transport module door  112 , the opening  136 P, and the opening  136 T are rounded, thus resulting in the “generally rectangular” shape referred to in the preceding paragraph. In other embodiments, the corners of the barrier doors and openings may not be rounded. In still other embodiments, the barrier doors and openings may be formed to have a shape other than rectangular. 
       FIG. 4  depicts a plan view of the interface between a processing module  106   a  and a process module barrier door  110 . The process module barrier door  110  has a barrier seal surface  150  and a vacuum seal  120 . The process module wall  132  has a barrier seal  122  and a vacuum seal surface  125 . The combination of the barrier seal  122  and the respective barrier seal surface  150  and the vacuum seal  120  and the respective vacuum seal surface  125  work to provide a vacuum-tight, or gas-tight, seal when the process module barrier door  110  is in a closed position, i.e. the barrier door  110  is pressed against the process module wall  132 . Alternatively, a seal device may be vulcanized to the process module barrier door  110  or process module wall  132 , or another type of seal device having a replaceable seal may be used. 
       FIG. 5  a perspective view of the processing module barrier door  110  of the first valve  104   a  shown in  FIG. 3 . The process module barrier door  110  encompasses a vacuum seal  120 , a barrier seal surface  150 , a groove  140  shaped to accept the vacuum seal  120 , and the interior face  160 . The entire face of the barrier door  110  to include the interior face  160 , the barrier seal surface  150 , and groove  140  are anodized surfaces. It should be understood that the groove  140  could also be unanodized. The cross section depicted in  FIG. 6  is referenced by the  6 - 6  line on  FIG. 5 . 
       FIG. 6  depicts a partial cross-sectional view along the  6 - 6  line of the processing module barrier door  110  depicted in  FIG. 5 . The process module barrier door  110  is shaped from aluminum to form an interior face  160 , a barrier seal surface  150 , and a groove  140  shaped to accept the vacuum seal  120 . The vacuum seal  120  and process module barrier door  110  can be heated to about 350-370 degrees Fahrenheit for five minutes for pre-cure and 400 degrees Fahrenheit for 24 hours for final cure to vulcanize or bond the vacuum seal  120  to the groove  140 . The process module barrier door  110  can then be treated to achieve a Type III hard anodized finish. A polishing head  200  is held by the CNC machine tool holder (not shown) and polishes the barrier seal surface  150  by skirting the edge  180  of the vacuum seal  120 . Skirting the edge of the vacuum seal  120  means to polish the barrier seal surface  150  immediately adjacent to the edge  180  of the vacuum seal  120 . Accordingly, in polishing the barrier seal surface  150  immediately adjacent to the edge  180 , the polishing head  200  does not touch the edge  180  of the vacuum seal  120 . It is believed that by avoiding contact with the vacuum seal  120 , by bounding the motion of the polishing head  200 , damage to the vacuum seal  120  can be avoided. The barrier seal surface  150  can be polished to a finish of less than or equal to about 8 Ra. 
       FIGS. 7   a - c  depict a top down view of the process module barrier door  110  along with the vacuum seal  120 , barrier seal surface  150 , and the interior face  160 . In  FIG. 7   a , the polishing head  200  is depicted as moving along a parallel path  210  that is formed along the length of the edge  180  of the vacuum seal  120  on the process module barrier door  110 . The polishing head  200  can traverse the parallel path  210  by incrementally offsetting enough to polish unpolished material. The polishing head  200  can continue to run in successive parallel motions similar to the parallel path  210  until all the unpolished barrier seal surface  150  adjacent to the vacuum seal  120  of the process module barrier door  110  is polished. 
     Referring now to  FIG. 7   b , the polishing head  200  can traverse a perpendicular path  220 . The perpendicular path  220  can be defined such that at least a portion of the perpendicular path  220  is substantially perpendicular to the edge  180  of the vacuum seal  120  of the process module barrier door  110 . The polishing head  200  can traverse the perpendicular path  220  in one or more iterations to enough to polish unpolished material. Accordingly, the polishing head  200  can continue to run in successive perpendicular motions until all the unpolished barrier seal surface  150  adjacent to the vacuum seal  120  of the process module barrier door  110  is polished. 
     Referring now to  FIG. 7   c , the polishing head  200  can move in an overlapping and substantially circular path  230  that covers the area of the barrier seal surface  150  adjacent to the vacuum seal  120  of the process module barrier door  110 . The polishing head  200  can continue to run in overlapping and substantially circular paths  230  until all the unpolished barrier seal surface  150  adjacent to the vacuum seal  120  of the process module barrier door  110  is polished. It is noted that, while  FIGS. 7   a - c  depict the parallel path  210 , the perpendicular path  220 , and the overlapping and substantially circular path  230  individually, the polishing head  200  can traverse a path that includes two or more of the perpendicular path  220 , and the overlapping and substantially circular path  230 . 
     The polishing head can be equipped with a backing pad and grit paper of various abrasiveness and material make-up; a buffing pad and an abrasive compound or abrasive slurry; a router bit; or any other tool or material that is designed to polish a surface. The polishing head can move the abrasive material in a circular motion, an orbital motion, or lock in place. 
     The polishing head engages the barrier door at the precise pressure required by the combination of the hardness of the metal composition of the barrier door and the type and abrasiveness of the grit to achieve the proper polish on the metal surface or anodize surface. 
     It should be appreciated that the precision of the CNC machine allows the polishing head to skirt the edge of the vacuum seal by tracing without touching or physically damaging the vacuum seal on the barrier door. A protective film or cover can be placed over the vacuum seal to protect the vacuum seal from the polishing head. 
     It should be appreciated that the vacuum seal could be a removable o-ring or a bonded seal through vulcanization. The vacuum seal could be made from rubber or fluoroelastomer or perfluoroelastomer or any other elastomer. Furthermore, the process module barrier door can be made of any type of metal to include aluminum, more specifically, type 6061-T6XX aluminum. The embodiments described herein are not limited to the process module barrier door or the processing module. The barrier seal could be made from a chemically inert material, more specifically, PFA. Since chemically inert plastics typically have low relative elastic properties, seals utilizing such materials typically have an inner elastic energizer, more specifically, an elastomeric material such as silicone or Viton, or a metallic spring energizer. When the application of the barrier seal is sensitive to metallic materials, the elastomeric energizer is preferred over the metallic spring energizer. A seal of this type is often referenced as a solidcore PFA encapsulated seal. 
     It is noted that the terms “substantially” and “about” may be utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. These terms are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue. 
     While particular embodiments have been illustrated and described herein, it should be understood that various other changes and modifications may be made without departing from the spirit and scope of the claimed subject matter. Moreover, although various aspects of the claimed subject matter have been described herein, such aspects need not be utilized in combination. It is therefore intended that the appended claims cover all such changes and modifications that are within the scope of the claimed subject matter.