Patent Publication Number: US-2011076848-A1

Title: Semiconductor process chamber and seal

Description:
RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 61/221,694 filed Jun. 30, 2009, which is hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to seals and more particularly to seals for use in a substrate processing apparatus. 
     BACKGROUND 
     Many semiconductor manufacturing methods now require processing chambers to create ultra-high-vacuum (UHV—pressures lower than about 10 −7  pascal and/or 10 −9  torr) and/or ultra-high-purity (UHP—total maximum contaminant level of 10 ppm) environments. These manufacturing methods can involve repeated opening and sealing of process chambers so that substrates (e.g., wafers) can be continuously loaded, processed, and then unloaded therefrom. Slow production rates (e.g., caused by long pump-down times), significant equipment downtime (e.g., for seal replacement or interface cleaning) and/or substandard yields (e.g., due to particle generation) are generally viewed as undesirable by semiconductor manufacturers. 
     SUMMARY OF THE INVENTION 
     A seal is provided for sealing the container-lid interface of a semiconductor process chamber. In this seal, a relatively rigid metallic or polymeric element and an elastomeric element are arranged to seal the interface in series, with the metallic or polymeric sealing element being situated to encounter processing activity upstream of the elastomeric element, thereby protecting the elastomeric element from harsh processing conditions while minimizing particle generation. In this manner, the seal can be constructed to achieve ultra high vacuum levels without compromising on cleanliness, and still allow a clamped (rather than bolted) container-lid interface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a schematic view of a process chamber comprising a container and a lid, the lid being shown in its load/unload position. 
         FIG. 1B  is a schematic view of a process chamber comprising a container and a lid, the lid being shown in its closed/sealed condition. 
         FIG. 2A  is a close-up view showing a seal installed in a groove in an interface surface of the container when the lid is in its load/unload position. 
         FIG. 2B  is a close-up view similar to  FIG. 2A , except that the lid is shown in its sealed condition. 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, and initially to  FIGS. 1A and 1B , a process chamber  10  comprises a container  12 , a lid  14 , and an interface  16  therebetween. The container  12  defines a processing space  20  (and an access opening  22  thereinto). The lid  14  is movable between a loading/unloading position ( FIG. 1A ), whereat the access opening  22  is uncovered, and a sealed condition ( FIG. 1B ), whereat it seals the access opening  22  into the processing space  20 . 
     The process chamber  10  can be an ultra-high-vacuum (UHV) and/or ultra-high-purity (UHP) chamber which is part of a semiconductor manufacturing process. When the lid  14  is in its load-unload condition, the substrate  24  (e.g., a wafer) can be inserted through the access opening  22  into the processing space  20  and staged on the pedestal  26 . Once the lid  14  is moved to its sealed position, the interface  16  is sealed; the substrate  24  can be processed within the container  12 . The processing can comprise photo-masking, deposition, oxidation, nitridation, ion implantation, diffusion, and/or etching. 
     After the wafer-processing step, the vacuum can be released within the processing space  20 , and the lid can be converted from its sealed condition to its load-unload condition. The substrate  24  can be withdrawn from the processing space  20  through the access opening  22 . These steps can be repeated for the next substrate (e.g., the next wafer in the processing line) and so on. 
     The container  12  includes an interface surface  30  surrounding the access opening  22  and the lid  14  includes an interface surface  32  seated against the container&#39;s interface surface  30  when in its sealed condition. These surfaces  30  and  32  together define the interface  16  between the container  12  and the lid  14 . A clamp  34  (or other suitable means) can be provided to brace, lock or otherwise hold the lid  14  against the container  12 . 
     The container&#39;s interface surface  30  and/or the lid&#39;s interface surface  32  include at least one continuous groove  36 . The groove  36  may have a circular plan shape or other plan shape. And as is best seen by referring additionally to  FIGS. 2A and 2B , the groove  36  preferably has a dove-tail cross-sectional shape with a wider bottom than top. A seal  40  having a generally ring-like (annular) shape is seated in the continuous groove  36 . 
     The seal  40  generally comprises a metallic or polymeric sealing element  50  and an elastomeric sealing element  60 . The metallic or polymeric sealing element  50  can be made from a suitable metal such as aluminum, steel, stainless steel, copper, brass, titanium, nickel, and alloys thereof, or from a suitable polymeric material such as polyether ether ketone (PEEK), polytetrafluoroethylene (PTFE), polyamide (PA), fluoropolymers (PFA), polyetherimide (PEI aka Ultem), nylon or the like, so that the sealing element  50  is relatively rigid and non-elastomeric in comparison to the elastomeric sealing element  60 . The elastomeric sealing element  60  can be made from any suitable elastomeric material including fluorocarbon (FKM, FPM), high performance fluoroelastomers (HiFluor), perfluoroelastomers (FFKM, elastomeric PTFE), polyacrylate (ACM), ethylene acrylate (AEM), isobutylene-isoprene (IIR), polychloroprene rubber (CR), ethylene propylene rubber (EPM, EPR, EPDM), fluorosilicone (FVMQ), acrylonitrile-butadiene (NBR), hydrogenated nitrile (HNBR, HSN), polyurethane (AU, EU), silicone (VMQ, PVMQ), and tetrafluoroethylene-propylene (AFLAS registered trademark). 
     The metallic or polymeric sealing element  50  preferably has an L-shaped cross section with a bottom leg  51  oriented parallel to the floor of the groove and a side leg  52  oriented perpendicular thereto. The legs  51  and  52  together define the floor  53  and the radially inner side wall  54  of the metallic or polymeric sealing element  50 . The leg  51  further defines a ledge  55  and a radially outer side wall  56 , and the leg  52  further defines a roof  57  and a radially intermediate side wall  58 . 
     The elastomeric element  60  has a roof portion  61 , a radially-inner floor portion  62 , and a radially-outer floor portion  63 . The roof portion  62  is situated in the shelf-like space defined by the ledge  55  and the side wall  58  of the metallic or polymeric sealing element  50 . The floor portions  62  and  63  extend downward from the floor  53  of the metallic or polymeric sealing element  50 . When the seal  40  is in an uncompressed condition ( FIG. 2A ), the roof portion  62  has a rounded projection  64  that axially extends beyond the height of the metallic or polymeric sealing element  50  (e.g., its roof  57 ). The floor portions  62  and  63  each have a bead-like shape, with the outer portion  63  having an extension  65  extending radially beyond the metallic or polymeric sealing element  50  (e.g., its side wall  56 ). 
     The metallic or polymeric sealing element  50  and the elastomeric element  60  are arranged to seal a lid interface in series. Specifically, the lid&#39;s interfacing surface will first contact the roof portion  61  of the elastomeric member  60  (e.g., its projection  64 ). This contact will cause compression of the roof portion  61  against the lid and compression of the floor portions  62  and  63  against the floor of the groove. This preliminarily seals the process chamber thereby allowing a vacuum to build and further pull the lid towards the container&#39;s interfacing surface. As the container-lid gap decreases, the portions  61 - 63  of the elastomeric member  60  are further compressed until the height of the roof portion  62  corresponds to the groove&#39;s height. 
     When the seal  40  is installed in the process chamber, and the lid is completely closed, the metallic or polymeric sealing element  50  (e.g., its side wall  54 ) is situated to encounter processing activity upstream of the elastomeric element. The wider the leg  52 , the better protection against, for example, process plasma flow. The metallic or polymeric sealing element  50  is preferably rigid and essentially is not compressed during the closing process. But it is lowered into the groove due to the compression of the floor portions  62  and  63  of the elastomeric member  60 . In any event, the metallic or polymeric sealing element  50  functions as a shield to protect the elastomeric element  60  from gas permeation and/or direct impingement of high energy or ions. 
     The metallic or polymeric sealing element  50  (e.g., its roof  57 ) may encounter the lid during latter stages of closing depending upon the shape/size of the roof portion  61  and/or its rounded projection  64 . The roof  57  of the metallic or polymeric sealing element  50  can have a profile (e.g., flat) to makes parallel contact with the lid&#39;s interface surface. The floor portions  62  and  63  of the elastomeric member  60  provide a non-rocking platform for the metallic or polymeric sealing element  50  during the closing process. The inner floor portion  62  provides a vacuum seal along the bottom of the groove and the outer floor portion  63  provides a secondary or redundant seal along this lower path. 
     The extension  65  on the outer floor portion  63  can perform as a retention feature for the seal  40  once it is installed in the groove. Specifically, for example, if the groove has a dove-tail shape (as shown), the seal  40  cannot be removed therefrom without compression of this extension  65 . This retention feature may ease installation and/or reduce seal-pullout when the lid is opened. To perform this role, the extension  65  must result in the radial span of the lower region of the seal  40  having a greater dimension than the radial span of the top of the groove. 
     The seal  40  can be designed by optimizing parameters including the compressibility of the elastomeric element, the stiffness value of the metallic or polymeric sealing element, the uncompressed height of the elastomeric element, the relative height of the metallic or polymeric sealing element, and/or the initial gap distance between the interfacing surfaces. The optimizing step can comprise, for example, finite element analysis (FEA). 
     Although the processing chamber  20 , the seal  10 , the elastomeric element  40 , the metallic or polymeric sealing element  50 , and/or associated methods have been shown and described with respect to certain embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art. In regard to the various functions performed by the above described elements (e.g., components, assemblies, systems, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.