Patent Publication Number: US-2006011137-A1

Title: Shadow frame with mask panels

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims benefit of U.S. Provisional Application No. 60/588,462, filed Jul. 16, 2004, which is hereby incorporated by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      Embodiments of the present invention generally relate to a shadow frame assembly for large area substrates.  
      2. Description of the Related Art  
      The ability to process large glass substrates has become important as the demand for large area, flat panel displays such as televisions and computer screens is increasing rapidly. Large area, flat panel displays typically include thin film transistors (TFTs) formed thereon.  
      The formation of TFTs on large area, flat panel displays or substrates typically includes the deposition of one or more films on the displays by plasma enhanced chemical vapor deposition (PECVD). Depositing uniform thin films across large substrates has proven challenging for several reasons. For example, it is difficult to uniformly heat large area substrates. In addition, plasma conditions often vary across the surface of a large area substrate. Large area substrates are also prone to deformation, such as warping and bowing, as a result of non-uniform heating across the substrate.  
      Shadow frames have been developed to hold down the edges of large area substrates on a substrate support in a processing chamber during processing to prevent deformation of the substrates. The shadow frames also help prevent unwanted deposition of material on the edges and backside of substrates. However, improved shadow frames are needed, as deposition uniformity is often still an issue even with the use of shadow frames. For example, the shadow frame itself can create non-uniform processing conditions across a substrate by having an uneven substrate contact surface that allows leakage of process gases between the shadow frame and the substrate. Uniformity issues are very critical for large area substrates as a defect in a large area substrate that renders the substrate useless may mean the loss of millions of devices, such as TFTs, with the loss of one substrate.  
      There also remains a need for a method of dividing large area substrates into multiple components, such as multiple displays. In one aspect, dividing large area substrates can be used to provide multiple displays from one substrate. In another aspect, dividing large area substrates into multiple components may comprise providing multiple screen areas on one large panel.  
     SUMMARY OF THE INVENTION  
      The present invention generally provides a method and apparatus for masking portions of a large area substrate, such as large panels, during substrate processing. In one embodiment, an apparatus for masking portions of a large area substrate during processing includes a shadow frame having one or more mask panels.  
      In another embodiment, an aluminum shadow frame is provided having one or more mask panels made of ceramic. The mask panels are disposed in a recess formed in the upper surface of the frame to enable contact with a substrate being processed while maintaining a planar upper surface with the frame. In one aspect, the shadow frame assembly creates multiple processing regions on a large substrate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      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.  
       FIG. 1  is an exploded view of an embodiment of a shadow frame assembly of the invention.  
       FIG. 2A  is a cross-sectional view of a region of a shadow frame assembly in which the shadow frame and a mask panel are connected.  
       FIG. 2B  is a cross-sectional view of a region of a shadow frame assembly in which the shadow frame and a mask panel are connected and fastened together.  
       FIG. 3  is a top plan view of an embodiment of a shadow frame assembly positioned on a substrate support member.  
       FIG. 4  is a cross-sectional view through lines  4 - 4  of  FIG. 3 .  
       FIG. 4A  is an enlarged view of a region of  FIG. 4  showing an embodiment of a shadow frame assembly positioned on a substrate support member.  
       FIG. 5  is an exploded view of another embodiment of a shadow frame assembly of the invention.  
       FIG. 6  is a schematic cross-sectional view of an exemplary processing chamber having an embodiment of the shadow frame assembly of the invention disposed therein.  
       FIG. 7  is a sectional view of another embodiment of a fastener securing a mask panel to a shadow frame.  
      To facilitate understanding, identical reference numerals have been used, wherever possible, to designate identical elements that are common to the figures. It is contemplated that elements of one embodiment may be advantageously utilized in other embodiments without further recitation. 
    
    
     DETAILED DESCRIPTION  
      The present invention provides a method and apparatus for masking portions of large area substrates, such as large glass and/or plastic panels, during substrate processing. A shadow frame assembly is provided that includes a shadow frame having one or more mask panels. The shadow frame may be adapted or configured to receive one or multiple mask panels. By masking portions of a large area substrate underlying the shadow frame assembly, multiple isolated processing regions on the substrate can be formed such that material may be selectively deposited on predefined regions (e.g., unmasked areas) of the substrate.  
       FIG. 1  is an exploded view of one embodiment of a shadow frame assembly  10 . The shadow frame assembly  10  comprises a shadow frame  12  and at least one mask panel. In the embodiment depicted in  FIG. 1 , mask panels  16 ,  18 , and  20  are shown. A substrate is received within the shadow frame  12  and contacted by the mask panels  16 ,  18 , and  20  on a lower surface thereof.  
      The shadow frame  12  typically has a generally rectangular shape and defines a central aperture  11 . Aperture  11  is sized to receive a substrate to be processed therethrough. The shadow frame may have an aperture sized such that the shadow frame can be used with large area substrates, such as substrates having a surface area of at least about 13,000 cm 2  or at least about 15,000 cm 2 . The shadow frame may have dimensions such that it can be used to process substrates having a surface area of greater than one square meter. The shadow frame  12  may be made of aluminum, ceramic or other suitable material. In one embodiment, the shadow frame  12  is made of aluminum. The shadow frame  12  includes holes  13 ,  15  in an inner recessed region  14  of the shadow frame  12  circumscribing the central aperture  11 . The holes  13 ,  15  are adapted to receive fasteners  28  that secure the mask panels  16 ,  18 , and  20  to the shadow frame  12 .  
      The inner recessed region  14  of the shadow frame  12  is stepped from the outer region  21  of the shadow frame  12 , such that the inner region  14  forms a shelf which accommodates the mask panels  16 ,  18 , and  20  in a substantially co-planar orientation relative to an upper surface of the outer region  21  of the shadow frame. The inner region  14  of the shadow frame may include a stepped surface  39  along an outer edge thereof to support a lateral mask panel and the transverse mask panels along one surface thereof. The stepped surface orients the lateral mask panel at a slight angle in the recess to ensure sealing contact with the substrate once the frame assembly is positioned over the substrate.  
      The mask panels  16 ,  18 , and  20  may be fabricated from a heat resistant material, such as ceramic or other suitable material, that can withstand chamber processing temperatures, e.g., about 450° C., without substantially bending or warping while having a minimal thickness, such as several hundredths or even several hundred thousandths of an inch. The mask panels may be sized to minimize interference with a gas distribution assembly disposed in the chamber while maintaining the requisite spacing between the glass substrate and the gas distribution assembly. It is contemplated that the panel  20  may be retained by one or more fasteners  28  on a single side so that the panel  20  extends in a cantilevered manner into the interior region  14  defined by the frame  12 .  
      In the embodiment shown in  FIG. 1 , the shadow frame assembly  10  includes two lateral mask panels  16  that are parallel or approximately parallel to a major axis of the shadow frame  12 . The lateral mask panels cover the long edges of a substrate. The lateral mask panels  16  have holes  17  formed therethrough that enable fasteners  28  to be disposed therethrough to fasten the lateral mask panels  16  to the holes  13  formed in the shadow frame  12 . The holes  17  may be elongated to allow the fastener  28  to move with holes  13  as the panel expands. The lateral mask panels  16  may have slotted regions  24  that are sized to mate with projecting regions  19  defined at the ends of transverse mask panels  18 . The lateral mask panels  16  may have slotted regions  26  that are sized to receive the ends  23  of transverse mask panel  20 . In one embodiment, holes  17  may be located adjacent the slotted regions  24  and  26 .  
      In the embodiment depicted in  FIG. 1 , two terminal transverse mask panels  18  are provided for masking regions of a substrate adjacent the two ends of the lateral mask panels  16  and at least one central transverse mask panel  20  for masking an interior portion of the substrate. The central transverse mask panel  20  masks a region of the substrate disposed between the two terminal transverse mask panels  18 . It is contemplated that panels  16 ,  18 ,  20  may be arranged to cover other portions of the substrate.  
      In one embodiment, the transverse mask panels  18 ,  20  may be substantially parallel to the short axis of the shadow frame  12 . In one embodiment, transverse mask panels  18 ,  20  may be substantially co-planar with and substantially perpendicular to lateral mask panels  16 . The transverse mask panels  18 ,  20  may have holes  22  formed therein. The holes  22  enable fasteners, such as fasteners  28 , to be disposed therethrough to fasten the transverse mask panels  18 ,  20  to the holes  15  formed in the shadow frame  12 . The holes  22  may be elongated to accommodate panel expansion. The holes  22  in the terminal transverse mask panels  18  may be located in the projecting regions  19  of the ends of the terminal transverse mask panels  18 . The holes  22  in the central transverse mask panel  20  may be located in the ends  23  of transverse mask panel  20 .  
      As shown in  FIG. 1 , the projecting ends  19  of the terminal transverse mask panels  18  fit into slotted regions  24  of lateral mask panels  16 , and the ends  23  of central transverse mask panel  20  fit into the slotted regions  26  of lateral mask panels  16 . As the mask panels  16 ,  18 , and  20  are interlocked with each other rather than fastened on top of each other, the total thickness of the mask provided by all of the mask panels is approximately the thickness of one of the mask panels  16 ,  18 , and  20 . While fasteners  28  are shown connecting mask panels  16 ,  18 , and  20  to the shadow frame  12 , the fasteners may alternatively be used to connect one or more of the mask panels  16 ,  18 , and  20  to each other.  
       FIG. 2A  is a cross-sectional view of a region of the shadow frame assembly  10  in which the shadow frame  12  and a lateral mask panel  16  are connected via fastener  28 . In another embodiment, the fastener  28  may be deformable and/or ductile. In one embodiment, the fastener  28  may be fabricated from a metal, such as aluminum. In the embodiment depicted in FIGS.  2 A-B, the fastener  28  includes a blind hole  36  formed in a first end  39  of the fastener  28 . The first end  39  has a cylinder  34  extending from a main body  29  of the fastener  28 . The cylinder  34  has smaller diameter than the diameter of the body  29 . A washer  30 , such as an aluminum washer, is disposed over the cylinder  34  and abuts the body  29  of the fastener  28 . The cylinder  34  and washer  30  are configured to fit at least partially within a recess  32  formed in the underside of the shadow frame  12 . The washer  30  has an inner surface  31  that is angled away from the fastener  28  such that there is a space  35  defined between the fastener  28  and the inner surface  31  of the washer  30 .  
      A second end  202  of the fastener  28  includes a head  204  that extends outward from the body  29 . The head is configured to prevent the fastener  28  from passing through the hole  17  formed in the lateral mass panel  16 . In one embodiment, the head  204  is configured to fit into a recess  205  formed in the upper surface  207  of the lateral mass panel  16 , such that the exposed surface  211  of the head  204  is substantially co-planar or recessed below the upper surface  207 .  
      The shadow frame  12  and the lateral mask panel  16  may be fastened together by inserting a tool, e.g., a flaring tool, into the blind hole  36  and the fastener  28 , such that the tool flares the first end  39  of the cylinder  34  to abut the inner surface  31  of the washer  30 , as shown in  FIG. 2B . The flaring tool may be any suitable device for deforming the fastener  28  as depicted in  FIG. 2B . When deformed, the fastener  28  is secured to the washer  30 , thereby capturing the panel  16  to the shadow frame  12 .  
      It is contemplated that the washer  30  and fastener  28  may be secured by interference, fit, broaching, staking, braising, welding, riveting, keying or other suitable fastening method. It is also contemplated that the fastener  28  may be a screw, bolt, rivet or other type of fastener suitable for coupling the frame and panels. For example as depicted in  FIG. 7 , the fastener  28  may include a male threaded member  700  and a female threaded member  702  that engage to secure the panel to the frame. To reduce the height required for the members  700 ,  702 , one or more of the members  700 ,  702  may include a reduced profile drive  704 , such holes for a spanner wrench.  
      The flaring of the cylinder  34  of the fastener  28  prevents the fastener from being displaced upward past the upper surface of the mask panel  16 . Another advantage of working the fastener  28  to secure the washer  30  is that typically the fastener  28  may be shorter than necessary for conventional threaded engagement. A shorter fastener minimizes the amount of separation that the shadow frame assembly provides between the substrate and the gas distribution plate in the chamber during substrate processing. However, alternatively or in combination, the mask panels  16 ,  18 ,  20  and the shadow frame  12  may be fastened by alternative methods. It is also contemplated that at least one of the shadow frame  12  or panels  16 ,  18 ,  20  may be engaged loosely on the fasteners  28  without fastening.  
      A further advantage of using the fastener  28  described herein for fastening is that it can allow an appropriate clearance, for example, several thousandths of an inch, between the mask panels and the shadow frame. Such a clearance allows for thermal expansion differences during substrate processing at elevated temperatures between a shadow frame and mask panels made of different materials, such as an aluminum shadow frame and ceramic mask panels.  
       FIG. 3  is a top plan view of the shadow frame assembly  10  of  FIG. 1  in an assembled form positioned over a substrate  40  disposed on a substrate support member. The substrate  40  is positioned inward of an edge  43  of the frame  12  defining the inner region  14 . Short side edges  41  of the substrate  40  are covered by terminal transverse mask panels  18  and a lateral side edge  42  of the substrate  40  are covered by lateral mask panels  16 . As shown in  FIG. 3 , mask panels  16 ,  18 ,  20  are seated in recessed inner region  14  of the mask frame  12 . Lateral mask panels  16  and terminal transverse mask panels  18  are seated in an outer portion of the recessed inner region  14 , while central mask panel  20  is seated in an inner portion of the recessed inner region  14 . In the embodiment shown in  FIG. 3 , the lateral mask panels  16  do not overlap and are not overlapped by terminal transverse mask panels  18  or central mask panel  20  such that no portion of the lateral mask panels  16  rests on the mask panels  18 ,  20  or supports a portion of the mask panels  18 ,  20 . The lateral mask panels and the transverse mask panels interlock without overlapping, as slotted regions  24  ( FIG. 1 ) of the lateral mask panels  16  are sized to receive projecting regions  19  of the ends of transverse mask panels  18 , and slotted regions  26  of the lateral mask panels  16  are sized to receive the ends  23  ( FIG. 1 ) of transverse mask panel  20 .  
       FIG. 4  is a cross-sectional view through lines  44  of  FIG. 3 .  FIG. 4  is shown with break  71  for clarity and to show details of the shadow frame assembly. The shadow frame  12  is supported on substrate support assembly  50 . The lateral mask panel  16  and the terminal transverse mask panel  18  are secured to shadow frame  12  by fasteners  28 . Substrate  40  is supported by support region  56  of the substrate support assembly  50 .  
       FIG. 4A  is an enlarged view of a region of  FIG. 4 . Lateral mask panel  16  and terminal transverse mask panel  18  are supported in the recessed inner region  14  of the shadow frame. While all of the recessed inner region  14  is lower than the outer region  21  of the shadow frame, the recessed inner region may be angled or stepped such that an outer portion  60  of the recessed inner region  14  is slightly higher, e.g., a few hundredths of an inch, than the inner portion  64  of the recessed inner region  14 . It is believed that the higher elevation of the outer portion  60  causes the mask panels  16 ,  18  to slope inwardly toward the center of the substrate  40  and thus, ensures that the inner edges of the panels  16 ,  18  contact the substrate  40  to effectively mask the portions of the substrate underlying the panels  16 ,  18  from deposition.  
      The panels  516 ,  518 ,  520  are secured to the frame  512  by pins  18  as described with reference to the panels  16 ,  18 ,  20  and frame  12  above. Referring back to  FIG. 1 , the shadow frame assembly  10  is assembled by placing fasteners  28  through the holes  17 ,  22  in the mask panels into the corresponding holes  13 ,  15  in the shadow frame  12 . After all of the fasteners  28  are placed in the holes, the pins are fastened, as described above with respect to  FIG. 2B . Mask panels  16 ,  18 , and  20  collectively form a mask defining an outer perimeter having a rectangular shape similar to the shape of the shadow frame  12 , wherein the outer perimeter of the mask is smaller than the outer perimeter of the shadow frame  12  and the perimeter of a substrate to be processed so that the edges thereof are masked. The outer perimeter of the mask is formed by lateral mask panels  16  and terminal transverse mask panels  18 . The mask is bisected by central transverse mask panel  20  such that the mask defines two apertures between the lateral mask panels  16  and the terminal transverse mask panels  18 .  
      In one embodiment, the outer region  21  of the shadow frame  12  may include a lower surface  402  that extends below and circumscribes a lower surface  400  of the frame  12 . A wall  406  extends between the lower surface  402  of the outer region  21  and the lower surface  400  of the inner region of the frame  12 . The wall  406  is configured to surround and overlap a wall  408  of the substrate support assembly  50  on which the shadow frame  12  is disposed.  
      The outer region  21  includes a sloped surface  404  that couples the lower surface  402  of the outer region  21  and an outside edge  410  of the frame  12 . The sloped surface  404  facilitates locating and supporting of the shadow frame  12  inside the chamber as shown below in  FIG. 6 .  
      The shadow frame assembly  10  of  FIG. 1  is configured to form two isolated processing regions on a substrate which define an area for forming a desired display, wherein the perimeter of one of the processing regions is defined by the inner edges of lateral mask panels  16 , one edge of the central transverse mask panel  20  and the inner edge of one of the terminal transverse mask panels  18 . The perimeter of the other processing region is defined by the inner edges of lateral mask panels  16 , the opposing edge of the central transverse mask panel  20  and the inner edge of the other terminal transverse mask panel  18 .  
       FIG. 5  is an exploded view of another embodiment of a shadow frame assembly  500 . Reference numerals from  FIG. 1  are used to show identical parts in  FIG. 5 . While shadow frame assembly  10  in  FIG. 1  comprises two terminal transverse mask panels  18  and one central transverse mask panel  20 , the shadow frame assembly  500  in  FIG. 5  includes a frame  512 , two terminal transverse mask panels  518  and two central transverse mask panels  520 . Each lateral mask panel  516  of shadow frame assembly  500  includes two slotted regions  26  that are sized to receive the ends  23  of central transverse mask panels  520 .  
      The shadow frame assembly  500  of  FIG. 5  is configured to form three isolated processing regions on a substrate. The perimeter of a first isolated processing region is defined by the inner edges of lateral mask panels  516 , one edge of one of the central transverse mask panels  520  and the inner edge of one of the terminal transverse mask panels  518 . The perimeter of a second isolated processing region is defined by the inner edges of lateral mask panels  516  and the two central transverse mask panels  520 . The perimeter of a third isolated processing region is defined by the inner edges of lateral mask panels  516 , one edge of the other central transverse mask panel  520  and the inner edge of the other terminal transverse mask panel  518 .  
      As can be seen in  FIGS. 1 and 5 , the mask panels  516 ,  58 , and  520  can have varying widths. The mask panels  518 ,  520  may have substantially the same widths, similar to those shown in  FIG. 1 , or the terminal transverse mask panels  518  and the central transverse mask panels  520  may have different widths, as shown in  FIG. 5 . The widths of the mask panels  516 ,  518 , and  520  can be chosen to provide processing regions of a desired area on a substrate.  
      While embodiments of shadow frame assemblies having two lateral mask panels, two terminal transverse mask panels, and one or two central transverse mask panels are shown and described herein, it is contemplated that shadow frame assemblies may include other numbers of mask panels, i.e., two or more lateral mask panels and one or more central transverse mask panels. For example, four processing regions may be provided on a substrate by using a shadow frame assembly comprising three lateral mask panels, one central transverse mask panel, and two terminal transverse mask panels. The panels may be arranged to mask areas of the substrate that are not polygonal in form. One or more of the masks may include an aperture  530  as shown in phantom in  FIG. 5 . The aperture  530  permits deposit on the substrate to occur through the aperture.  
      In another embodiment, multiple processing regions may be provided on a substrate by using a shadow frame assembly comprising a one-piece mask rather than a mask comprised of multiple mask panels. For example, a one-piece mask having the shape of the mask formed by mask panels  16 ,  18 , and  20  in FIGS.  1  or  5  may be used. The one-piece mask may be formed as one piece or formed from multiple pieces fused together. The one-piece mask may be made of ceramic.  
      An example of a substrate processing chamber including a shadow frame assembly as described herein will be described with respect to  FIG. 6 .  FIG. 6  is a schematic cross-sectional view of one embodiment of a plasma enhanced chemical vapor deposition chamber  200 , available from AKT, a division of Applied Materials, Inc. of Santa Clara, Calif. The chamber  200  generally includes a processing chamber body  202  coupled to a gas source  204 . The processing chamber body  202  has walls  206  and a bottom  208  that partially define a process volume  212 . The process volume  212  is typically accessed through a port (not shown) in the walls  206  that facilitate movement of a substrate  240  into and out of the processing chamber body  202 . The walls  206  and bottom  208  are typically fabricated from a unitary block of aluminum or other material compatible with processing. The walls  206  support a lid assembly  210  that contains a pumping plenum  214  that couples the process volume  212  to an exhaust port (that includes various pumping components, not shown).  
      A temperature controlled substrate support assembly  238  is centrally disposed within the processing chamber body  202 . The support assembly  238  supports a substrate  240  during processing. In one embodiment, the substrate support assembly  238  comprises an aluminum body  224  that encapsulates at least one embedded heater  232 . The heater  232 , such as a resistive element, disposed in the support assembly  238 , is coupled to a power source  274  and controllably heats the support assembly  238  and the glass substrate  240  positioned thereon to a predetermined temperature. Typically, in a CVD process, the heater  232  maintains the substrate  240  at a uniform temperature between about 150 to at least about 460 degrees Celsius, depending on the deposition processing parameters for the material being deposited.  
      Generally, the support assembly  238  has a lower side  226  and an upper side  234 . The upper side  234  supports the substrate  240 . The lower side  226  has a stem  242  coupled thereto. The stem  242  couples the support assembly  238  to a lift system (not shown) that moves the support assembly  238  between an elevated processing position (as shown) and a lowered position that facilitates substrate transfer to and from the processing chamber  202 . The stem  242  additionally provides a conduit for electrical and thermocouple leads between the support assembly  238  and other components of the system  200 .  
      A bellows  246  is coupled between support assembly  238  (or the stem  242 ) and the bottom  208  of the processing chamber  202 . The bellows  246  provides a vacuum seal between the chamber volume  212  and the atmosphere outside the processing chamber  202  while facilitating vertical movement of the support assembly  238 .  
      The support assembly  238  generally is grounded such that RF power supplied by a power source  222  to a gas distribution plate assembly  218  positioned between the lid assembly  210  and substrate support assembly  238  (or other electrode positioned within or near the lid assembly of the chamber) may excite gases present in the process volume  212  between the support assembly  238  and the distribution plate assembly  218 . The RF power from the power source  222  is generally selected commensurate with the size of the substrate to drive the chemical vapor deposition process.  
      The support assembly  238  has a plurality of holes  228  disposed therethrough that accept a plurality of lift pins  250 . The lift pins  250  are typically comprised of ceramic or anodized aluminum. The lift pins  250  may be actuated relative to the support assembly  238  by an optional lift plate  254  to project from the support surface  230 , thereby placing the substrate in a spaced-apart relation to the support assembly  238 .  
      The support assembly  238  additionally supports a shadow frame assembly  270 . The shadow frame assembly  270  includes a shadow frame  248  and mask panels, including mask panels  253 . The shadow frame assembly  270  covers one or more portions of the substrate  240  during processing so that only predefined regions of the substrate are exposed for receiving deposition materials thereon. The shadow frame assembly  270  may be configured as described above. When the substrate  240  is on the support assembly  238  in a lowered, non-processing position, the shadow frame assembly  270  is supported by the chamber body  202 . When the glass substrate  240  is raised into the processing position, the shadow frame assembly  270  is lifted from the chamber body such that the shadow frame assembly is supported by the support assembly  238  and covers portions of the substrate  240 .  
      The lid assembly  210  provides an upper boundary to the process volume  212 . The lid assembly  210  typically can be removed or opened to service the processing chamber  202 . In one embodiment, the lid assembly  210  is fabricated from aluminum (Al). The lid assembly  210  includes a pumping plenum  214  formed therein coupled to an external pumping system (not shown). The pumping plenum  214  is utilized to channel gases and processing by-products uniformly from the process volume  212  and out of the processing chamber  202 .  
      The lid assembly  210  typically includes an entry port  280  through which process gases provided by the gas source  204  are introduced into the processing chamber  202 . The entry port  280  is also coupled to a cleaning source  282 . The cleaning source  282  typically provides a cleaning agent, such as disassociated fluorine, that is introduced into the processing chamber  202  to remove deposition by-products and films from processing chamber hardware, including the gas distribution plate assembly  218 .  
      The gas distribution plate assembly  218  is coupled to an interior side  220  of the lid assembly  210 . The gas distribution plate assembly  218  is typically configured to substantially follow the profile of the glass substrate  240 , for example, rectangular for large area flat panel substrates. The gas distribution plate assembly  218  includes a perforated area  216  through which process and other gases supplied from the gas source  204  are delivered to the process volume  212 . The perforated area  216  of the gas distribution plate assembly  218  is configured to provide uniform distribution of gases passing through the gas distribution plate assembly  218  into the processing chamber  202 .  
      The gas distribution plate assembly  218  typically includes a diffuser plate  258  suspended from a hanger plate  260 . The diffuser plate  258  and hanger plate  260  may alternatively comprise a single unitary member. A plurality of gas passages  262  are formed through the diffuser plate  258  to allow a predetermined distribution of gas passing through the gas distribution plate assembly  218  and into the process volume  212 . The hanger plate  260  maintains the diffuser plate  258  and the interior surface  220  of the lid assembly  210  in a spaced-apart relation, thus defining a plenum  264  therebetween. The plenum  264  allows gases flowing through the lid assembly  210  to uniformly distribute across the width of the diffuser plate  258  so that gas is provided uniformly above the center perforated area  216  and flows with a uniform distribution through the gas passages  262 .  
      It is contemplated that the shadow frame assemblies described herein may be used in other plasma enhanced chemical vapor deposition chambers or in other substrate processing chambers including other chambers for processing large glass panel substrates.  
      A brief description of the engagement of a shadow frame assembly with a substrate in a processing chamber is provided herein. A shadow frame assembly is lifted from its support (as described with respect to  FIG. 6 ) by the substrate support assembly. Contact pins  52  ( FIG. 4A ) of a substrate support assembly are received by a recess  54  ( FIG. 4A ) in shadow frame  12  to ensure alignment of the shadow frame with the substrate support and hence a substrate supported thereon. The substrate has a smaller perimeter than the central aperture  11  of the shadow frame  12 . Thus, the substrate is raised through the aperture  11  of the shadow frame  12  and surrounded by the shadow frame  12 , as shown in  FIG. 3 . Mask panels are arranged to cover predefined regions of the substrate to prevent processing, such as deposition of a thin film, on the regions of the substrate disposed underneath the frame assembly.  
      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.