Patent Publication Number: US-2010122655-A1

Title: Ball supported shadow frame

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/114,866 (APPM/13876L), filed Nov. 14, 2008, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to an alignment assembly for a shadow frame. 
     2. Description of the Related Art 
     When depositing material onto a substrate during processing, material may deposit onto other areas of the processing chamber as well. If the substrate is not as large as the susceptor, then material may deposit onto the susceptor upon which the substrate may be situated during processing. Material deposited onto the susceptor may be problematic because the material may flake off during susceptor movement and/or substrate movement. The material that flakes off may contaminate the substrate or substrates later processed in the same processing chamber. 
     Additionally, material deposited on the substrate may bridge to material deposited on the susceptor. When the substrate is removed, the bridged material may break and potentially damage the substrate and/or the material deposited on the substrate. 
     When material is deposited onto the susceptor, the susceptor surface that receives the substrate may not be substantially planar and thus, substrates that are placed on the susceptor may not be properly aligned. The substrate could break. The material buildup on the susceptor could also lead to uneven deposition on the substrate. Because the substrate may not be resting on a planar surface, the substrate may bend and thus, the deposition surface of the substrate may not be substantially planar which may lead to uneven deposition. 
     Therefore, there is a need in the art to prevent or reduce deposition from occurring on a susceptor not covered by a substrate during processing. 
     SUMMARY OF THE INVENTION 
     Embodiments disclosed herein generally include an alignment assembly for aligning a shadow frame on a susceptor. For producing large area flat panel displays or solar panels, the shadow frame that protects the areas of the susceptor not covered by the substrate from deposition may be so large that the shadow frame bends and doesn&#39;t properly align. By utilizing an alignment assembly having one or more ball bearings, the shadow frame may roll on the susceptor to a proper alignment position. Thus, the shadow frame may be prevented from bending and also align on the susceptor. 
     In one embodiment, a shadow frame is disclosed. The shadow frame includes a shadow frame body and one or more shadow frame slider assemblies recessed into the shadow frame body. 
     In another embodiment, an apparatus is disclosed. The apparatus includes a processing chamber body and a susceptor disposed in the processing chamber body and having a surface for receiving a substrate. The susceptor is movable from a first position to a second position. The apparatus also includes one or more slider elements coupled to the susceptor and a shadow frame disposed in the processing chamber body. The shadow frame is movable from a third position spaced from the susceptor to a fourth position in contact with the susceptor. The apparatus also includes one or more shadow frame slider assemblies coupled to the shadow frame. 
     In another embodiment, a method of aligning a shadow frame above a susceptor is disclosed. The method includes moving a susceptor from a first position to a second position. The susceptor has one or more slider surfaces. The method also includes moving a shadow frame from a third position spaced from the susceptor and a fourth position in contact with the susceptor when the susceptor is in the second position. The shadow frame has one or more shadow frame slider assemblies coupled thereto. The method also includes sliding the one or more shadow frame slider assemblies along the one or more slider surfaces to align the shadow frame above the susceptor. 
    
    
     
       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 a schematic cross sectional view of an apparatus according to one embodiment of the invention. 
         FIG. 2A  is a schematic top view of a shadow frame. 
         FIG. 2B  is a schematic cross sectional view of a misaligned shadow frame. 
         FIG. 2C  is a schematic cross sectional view of a shadow frame aligned with an alignment assembly according to one embodiment. 
         FIG. 2D  is a schematic cross sectional view of an alignment pin assembly according to one embodiment. 
         FIG. 3A  is a schematic cross sectional view of an alignment ball assembly in a raised position according to one embodiment. 
         FIG. 3B  is a schematic cross sectional view of the alignment ball assembly of  FIG. 3A  in a lowered position. 
         FIG. 3C  is a schematic cross sectional view of an alignment ball assembly embedded according to another embodiment. 
         FIG. 3D  is a schematic cross sectional view of the alignment ball assembly of  FIG. 3C  in an aligned position. 
         FIG. 4A  is a schematic cross sectional view of an apparatus  400  according to one embodiment. 
         FIG. 4B  is a schematic bottom view of the shadow frame  402  of  FIG. 4A . 
         FIG. 5  is a schematic cross sectional view of an apparatus  500  according to another embodiment. 
         FIG. 6A  is a schematic cross sectional view of an alignment assembly according to another embodiment. 
         FIG. 6B  is an isometric view of the alignment receiver of  FIG. 6A . 
         FIG. 6C  is an isometric view of the alignment button of  FIG. 6A . 
     
    
    
     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 and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Embodiments disclosed herein generally include an alignment assembly for aligning a shadow frame on a susceptor. For producing large area flat panel displays or solar panels, the shadow frame that protects the areas of the susceptor not covered by the substrate from deposition may be so large that the shadow frame bends and doesn&#39;t properly align. By utilizing an alignment assembly having one or more ball bearings, the shadow frame may roll on the susceptor to a proper alignment position. Thus, the shadow frame may be prevented from bending and also align on the susceptor. 
     The invention, as described below, may be practiced in a plasma enhanced chemical vapor deposition (PECVD) system available from AKT America, Inc., a subsidiary of Applied Materials, Inc., Santa Clara, Calif. It is contemplated that the invention may be practiced in other plasma processing chambers, including those from other manufacturers. 
       FIG. 1  is a schematic cross-sectional view of one embodiment of an apparatus  100  according to one embodiment. The apparatus  100  may include a processing chamber  102  coupled to a gas source  104 . The processing chamber  102  has walls  106  and a bottom  108  that partially define a process volume  112 . The process volume  112  may be accessed through a slit valve opening (not shown) in the walls  106  that facilitate movement of a substrate  140  into and out of the processing chamber  102 . In one embodiment, the walls  106  and bottom  108  may be fabricated from a unitary block of aluminum or other material compatible with processing. In another embodiment, the walls  106  and bottom  108  may comprise separate pieces coupled together. The walls  106  support a lid assembly/backing plate  110 . The processing chamber  102  may be evacuated by a vacuum pump  184 . 
     A temperature controlled substrate support assembly  138  may be centrally disposed within the processing chamber  102 . The support assembly  138  may support a substrate  140  during processing. The support assembly  138  may have a susceptor  134 . The susceptor  134  supports the substrate  140  during processing. The susceptor  134  may have one or more heat exchange elements  132  embedded therein to provide a measure of control over the substrate temperature. A stem  142  may be coupled to the lower side of the support assembly  138 . The stem  142  couples the support assembly  138  to a lift system (not shown) that moves the support assembly  138  between an elevated processing position and a lowered position that facilitates substrate transfer to and from the processing chamber  102 . The stem  142  additionally provides a conduit for electrical and thermocouple leads between the support assembly  138  and other components of the apparatus  100 . 
     A bellows  146  may be coupled between support assembly  138  or the stem  142  and the bottom  108  of the processing chamber  102 . The bellows  146  provides a vacuum seal between the chamber volume  112  and the atmosphere outside the processing chamber  102  while facilitating vertical movement of the support assembly  138 . 
     The support assembly  138  may be grounded such that RF power supplied by a power source  122  to a gas distribution plate  118  positioned between the lid assembly/backing plate  110  and substrate support assembly  138  (or other electrode positioned within or near the lid assembly/backing plate  110  of the chamber  102 ) may excite gases present in the process volume  112  between the support assembly  138  and the gas distribution plate  118 . The RF power from the power source  122  may be selected commensurate with the size of the substrate to drive the PECVD process. Periodically, the chamber  102  may need to be cleaned. A cleaning gas may be supplied from a cleaning source  182 . The cleaning gas may be remotely ignited into a plasma. 
     The processing gas and the cleaning gas may be provided to the chamber  102  through the lid assembly/backing plate  110  and enter a plenum  164  between the lid assembly/backing plate  110  and the gas distribution plate  118 . The gas distribution plate  118  may be electrically coupled to the lid assembly/backing plate  110  by a bracket  160 . The processing gas may pass from the plenum  164  to the processing area  112  through gas passages  162  formed through the gas distribution plate  118 . 
     The support assembly  138  may additionally support a circumscribing shadow frame  148 . The shadow frame  148  may prevent deposition at the edge of the substrate  140  and support assembly  138  so that the substrate  140  may not stick to the support assembly  138 . 
     As shown in  FIG. 1 , a controller  186  may interface with and control various components of the substrate processing system. The controller  186  may include a central processing unit (CPU)  190 , support circuits  192  and a memory  188 . 
     The processing gas may enter into the chamber  102  from the gas source  104  and be exhausted out of the chamber  102  by a vacuum pump  184 . As will be discussed below, when the substrate  140  is placed on the susceptor  134 , the susceptor  134  raises to meet the shadow frame  148  such that the shadow frame  148  is resting on the susceptor  134  and placed around the substrate  140  to cover the area on the susceptor  134  that is exposed to the processing gas in the processing chamber  102 . The shadow frame  148  is raised by the susceptor  134 . To ensure the shadow frame  148  is properly aligned onto the susceptor  134 , alignment inserts may be used. By placing the shadow frame  148  around the substrate  140 , the deposition at the edge of the substrate  140  and the susceptor  134  may be reduced. 
       FIG. 2A  is a schematic top view of a shadow frame  200 . The shadow frame  200  has a substantially rectangular shape with an opening  202  therethrough where a substrate will be visible during processing. The shadow frame  200  may have a side having a length shown by arrows “A” and a width shown by arrows “B”. In one embodiment, the length and the width may each be greater than about 1 meter. Thus, both the length and the width may span a substantially large distance. 
       FIG. 2B  is a schematic cross sectional view of a misaligned shadow frame  206 . The susceptor  204  has one or more alignment pins  208  extending upward from the susceptor  204 . The shadow frame  206  has a corresponding alignment receiver  210  having a cavity  214  which receives the alignment pin  208 . One or more rollers  212  may be present within the alignment receiver  210 . The one or more rollers  212  permit the alignment pin  208 , which has a sloped outer surface, to slide thereon such that the alignment pin  208  substantially centers into the cavity  214 . As shown in  FIG. 2A , the shadow frame  206  bows even through the alignment pin  208  is in the cavity  214 . Because the shadow frame  206  spans such a larger distance, the weight of the shadow frame  206  may be sufficient to cause the shadow frame  206  to bow rather than slide the alignment pin  208  along the rollers  212  to properly align the shadow frame  206 . 
       FIG. 2C  is a schematic cross sectional view of a shadow frame  222  aligned with an alignment assembly according to one embodiment. The susceptor  220  may have an alignment pin  224  extending therefrom. The shadow frame  222  may have an alignment receiver  226  having one or more rollers  228  therein that permit the alignment pin  224  to slide in the alignment receiver  226 . As noted above, the shadow frame  222  may be quite large and thus, quite heavy. To prevent the shadow frame  222  from bowing and remaining misaligned, an additional alignment mechanism may be present. 
     The additional alignment mechanism may comprise a slider surface  230 . The slider surface  230  may be recessed into or extending slightly above the susceptor  220 . The shadow frame  222  may have a ball bearing  234  that is centered by a centering ring  236  and rolls along a bearing plate  232 . The ball bearing  234  rolls along the slider surface  230  and the bearing plate  232 . In so doing, the shadow frame  222  may be less likely to bow. Additionally, the alignment pin  224  therefore does not get stuck and the shadow frame  222  does not bow. Along each side of the shadow frame  222 , one or more alignment receivers  226  and one or more ball bearings  234  may be present. In one embodiment, the one or more alignment receivers  226  and the one or more ball bearings  234  may be substantially centered along a side of the shadow frame  222 . 
       FIG. 2D  is a schematic cross sectional view of an alignment pin assembly according to one embodiment. The alignment pin  244  is shown embedded into and extending from the susceptor  240 . The alignment receiver  246  is shown embedded into the shadow frame  242 . It is to be understood that the alignment receiver  246  may be embedded in the susceptor  240  and the alignment pin  244  may be embedded in and extend from the shadow frame  242 . 
       FIG. 3A  is a schematic cross sectional view of an alignment ball assembly in a raised position according to one embodiment.  FIG. 3B  is a schematic cross sectional view of the alignment ball assembly of  FIG. 3A  in a lowered position. As shown in  FIG. 3A , the susceptor  302  has the support button  306  embedded therein. In one embodiment, the susceptor  302  may comprise aluminum. In one embodiment, the support button  306  may comprise ceramic. In another embodiment, the support button  306  may comprise a dielectric material. In another embodiment, the support button  306  may comprise a low friction material. The support button  306  may comprise a dielectric material to ensure electrical isolation of the shadow frame  304  from the susceptor  302 . In the embodiment shown in  FIGS. 3A and 3B , the support button  306  is embedded within the susceptor  302  and partially extends above the surface of the susceptor  302 . In one embodiment, the support button  306  may be substantially flush with the susceptor  302  such that the support button  306  has a top surface that is substantially planar with the top surface of the susceptor  302 . The support button  306  is the surface upon which the ball  312  may roll to permit the shadow frame  312  to properly align. 
     The shadow frame  312  may have a ball assembly therein. The ball assembly may comprise a bearing plate  308 , a ball  312 , and a centering ring  310 . In one embodiment, the bearing plate  308  may comprise ceramic. In another embodiment, the bearing plate  308  may comprise a dielectric material. In another embodiment, the bearing plate  308  may comprise a low friction material. The bearing plate  308  is the surface upon which the ball  308  may roll (in addition to the support button  306 ) to bring the shadow frame  304  into alignment. In the embodiment shown in  FIGS. 3A and 3B , the bearing plate  308  may have a substantially planar surface upon which the ball  312  may roll to align the shadow frame  304 . 
     The ball  312  may be contained within the assembly by a centering ring  310 . In one embodiment, the ball  312  may comprise aluminum. In another embodiment, the ball  312  may comprise ceramic. In another embodiment, the ball  312  may comprise a metal. In another embodiment, the ball  312  may comprise a dielectric. In one embodiment, the centering ring  310  may comprise a dielectric. In another embodiment, the centering ring  310  may comprise a ceramic. In another embodiment, the centering ring  310  may comprise a low friction material. 
     The centering ring  310  permits the ball  312  to rest in the centering ring  310  when the shadow frame  312  is in the raised position shown in  FIG. 3A . When the shadow frame  304  is coupled to the susceptor  302  as shown in  FIG. 3B , the ball  312  is free to move in any direction as shown by the arrows “C” along the bearing plate  308  subject to the boundaries of the centering ring  310 . The ball  312  is free to move to permit the shadow frame  304  to move relative to the susceptor  302  and properly align on the susceptor  302 . 
       FIG. 3C  is a schematic cross sectional view of an alignment ball assembly embedded according to another embodiment.  FIG. 3D  is a schematic cross sectional view of the alignment ball assembly of  FIG. 3C  in an aligned position. As shown by  FIGS. 3C and 3D , the ball  328  may be in the susceptor  320  as opposed to the shadow frame  322 . The shadow frame  322  may have a bearing plate  324  embedded therein to permit the ball  328  to slide thereon and properly align the shadow frame  322  on the susceptor  320 . In one embodiment, the bearing plate  324  may comprise a dielectric material. In another embodiment, the bearing plate  324  may comprise a ceramic. In another embodiment, the bearing plate  324  may comprise a low friction material. In one embodiment, the bearing plate  324  may have a surface upon which the ball  328  rolls that is substantially coplanar with the shadow frame  322  bottom surface. In another embodiment, the surface of the bearing plate  324  upon which the ball rolls  328  may extend from the shadow frame  322  bottom surface. 
     The ball assembly, on the other hand, may be embedded within the susceptor  320 . The ball assembly may comprise a ball  328 , a support button  326 , and a retaining ring  320 . In one embodiment, the ball  328  may comprise a metal. In another embodiment, the ball  328  may comprise aluminum. In another embodiment, the ball  328  may comprise a dielectric. In another embodiment the ball  328  may comprise a ceramic. 
     The ball  328  may rest on a support button  326 . In one embodiment, the support button  326  may comprise a dielectric. In another embodiment, the support button  326  may comprise a ceramic. The ball  328  rolls along the support button  326  when aligning the shadow frame  322 . The support button  326  may have a slightly conical surface upon which the ball  328  rolls to permit the ball  328  to center on the support button  326 . The ball  328  is permitted to roll in any direction as shown by arrows “D”. 
     A retaining ring  330  maintains the ball  328  within the ball assembly. In one embodiment, the retaining ring  330  may comprise a dielectric. In another embodiment, the retaining ring  330  may comprise a ceramic. The retaining ring  330  and hence, the ball assembly, may be coupled with the susceptor  320  by a fastening mechanism  332 . In one embodiment, the fastening mechanism  332  may comprise a retaining screw that is received by threaded portions of the susceptor  320 . The support button  326  may be placed in a cavity formed in the susceptor  320 . The ball  328  may be placed on the support button. The retaining ring  330  may then be placed in the cavity formed in the susceptor  320  and in contact with the support button  326 . The fastening mechanism  332  may then be coupled with the susceptor  320  to maintain the ball assembly within the cavity in the susceptor  320 . 
       FIG. 4A  is a schematic cross sectional view of an apparatus  400  according to one embodiment.  FIG. 4B  is a schematic bottom view of the shadow frame  402  of  FIG. 4A . The shadow frame  402  is disposed above the susceptor  404 . The susceptor  404 , during processing, raises to meet the shadow frame  402  and raises the shadow frame  402  along with the susceptor  404 . The susceptor  404  has a support button  406  embedded therein. The support button  406  is used to permit the shadow frame  402  to slide into alignment on the susceptor  404 . In one embodiment, the support button  406  may comprise a ceramic material. In another embodiment, the support button  406  may comprise a low friction material. 
     The shadow frame  402 , meanwhile, has a ball bearing  410  within that rolls on the support button  406  to align the shadow frame  402 . In one embodiment, the ball bearing  410  may comprise a metal. In another embodiment, the ball bearing  410  may comprise aluminum. In another embodiment, the ball bearing  410  may comprise a ceramic material. 
     The ball bearing  410  may be retained within the shadow frame  402  by a retaining structure  412 . In one embodiment, the retaining structure  412  may comprise a ceramic material. The ball bearing  410  may roll within the shadow frame on a bearing plate  408 . In one embodiment, the bearing plate  408  may comprise a ceramic material. The ball bearing  410  is permitted to move within the area enclosed by the bearing plate  408  and the retaining structure  412  for a distance shown by arrows “E”. 
     The retaining structure  412  may have a groove  416  along the outside surface thereof to permit a fastening mechanism  414  to couple the retaining structure  412  to the shadow frame  402 . In one embodiment, the fastening mechanism  414  may comprise a screw. While a groove  416  has been shown with the fastening mechanism  414  pressed thereagainst, it is to be understood that the fastening mechanism  414  may be coupled into the retaining structure  412  directly as opposed to pressed thereagainst. In such a situation, the retaining structure  412  may have threaded openings to receive the fastening mechanism  414 . The bearing plate  408 , ball bearing  410 , retaining structure  412 , and fastening mechanism  414  are all below the top surface  418  of the shadow frame  402  such that the top surface  418  is substantially planar and unitary in material. 
     It is to be understood that while the ball bearing  410  and the support button  406  have been shown in the shadow frame  402  and susceptor  404  respectively, the positions may be reversed. 
       FIG. 5  is a schematic cross sectional view of an apparatus  500  according to another embodiment. The shadow frame  502  is disposed above the susceptor  504 . The susceptor  504 , during processing, raises to meet the shadow frame  502  and raises the shadow frame  502  along with the susceptor  504 . The susceptor  504  has a support button  506  embedded therein. The support button  506  is used to permit the shadow frame  502  to slide into alignment on the susceptor  504 . In one embodiment, the support button  506  may comprise a ceramic material. In another embodiment, the support button  506  may comprise a low friction material. 
     The shadow frame  502 , meanwhile, has a ball bearing  512  within that rolls on the support button  506  to align the shadow frame  502 . In one embodiment, the ball bearing  512  may comprise a metal. In another embodiment, the ball bearing  512  may comprise aluminum. In another embodiment, the ball bearing  512  may comprise a ceramic material. 
     The ball bearing  512  may be retained within the shadow frame  502  by an enclosure  510  and a retaining ring  516 . In one embodiment, the enclosure  510  and retaining ring  516  may comprise a ceramic material. The retaining ring  516  may rest on a ledge  514  carved into the shadow frame  502 . The retaining ring  516 , ball bearing  512 , and enclosure  510  may be inserted into the shadow frame  502  from the top surface  508  thereof. 
     The enclosure  510  may have a groove  518  along the outside surface thereof to permit a fastening mechanism to couple the enclosure  510  to the shadow frame  502 . In one embodiment, the fastening mechanism may comprise a screw. It is to be understood that while the ball bearing  510  and the support button  506  have been shown in the shadow frame  502  and susceptor  504  respectively, the positions may be reversed. 
       FIG. 6A  is a schematic cross sectional view of an alignment assembly  600  according to another embodiment. The assembly includes a shadow frame  602  aligned on a susceptor  604 . An alignment element  606  may be coupled to the shadow frame  602  by one or more fastening mechanisms  608 . In one embodiment, the fastening mechanism  608  may comprise a screw. In one embodiment, the screw may comprise aluminum. In another embodiment, the screw may comprise anodized aluminum. In one embodiment, the alignment element  606  may comprise a ceramic material. The alignment element  606  may have a cavity  610  therein to receive an alignment ball  614  that is coupled to the susceptor  604 . 
     An alignment button  612  may be coupled to the susceptor  604 . The alignment button may have one or more balls  614  that engage the cavity  610  of the alignment element  606 . In one embodiment, the ball  614  may comprise aluminum. In another embodiment, the ball  614  may comprise anodized aluminum. The ball  614  may roll within the button  612  on one or more smaller balls  616 . In one embodiment, the balls  616  may comprise aluminum. In another embodiment, the balls  616  may comprise anodized aluminum. As can be seen in  FIG. 6A , the ball  614  may have a larger diameter than the balls  616 . The ball  614  is contained in the button  612  by a cover  618  that is coupled to a lower portion  620 .  FIG. 6B  is an isometric view of the alignment receiver of  FIG. 6A .  FIG. 6C  is an isometric view of the alignment button of  FIG. 6A . 
     To alignment the shadow frame  602  on the susceptor  604 , the susceptor  604  is raised and the ball  614  engages the sloped surface of the cavity  610 . The sloped surface of the cavity  610  slides down the ball  614  and thus, the shadow frame  602  is aligned on the susceptor  604 . As the sloped surface of the cavity  610  slides down the ball  614 , the ball  614  rotates within the button  612  along the smaller balls  616 . The smaller balls  616  rest on a low friction bearing surface. In one embodiment, the cover  618  and lower portion  620  each comprise a ceramic material. 
     It is to be understood that while the button  612  is shown coupled to the susceptor  604  and the alignment element  606  is coupled with the shadow frame  602 , the items could be reverses such that the alignment element  606  is coupled with the susceptor  604  and the button  612  is coupled with the shadow frame  602 . 
     By utilizing a ball assembly that has a ball capable of rolling on a bearing surface, a shadow frame may be properly aligned on a susceptor. If necessary, an alignment pin assembly may be used in addition to the ball assembly. The pin assembly in combination with the ball assembly may permit the shadow frame to roll into properly alignment over the susceptor when the susceptor raises the shadow frame into the processing position. 
     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.