Abstract:
The present invention generally comprises a backing plate reinforcement apparatus for use in a plasma enhanced chemical vapor deposition apparatus. When processing large area substrates, the backing plate extending across the chamber may also be quite large. By supporting a central area of the backing plate with a frame structure, the backing plate may be maintained substantially planar. Alternatively, as necessary, the contour of the backing plate may be adjusted to suit the particular needs of the process.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Patent Application Ser. No. 60/891,842 (APPM/011870L), entitled “PECVD Process Chamber Backing Plate Reinforcement”, filed Feb. 27, 2007, which is herein incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the present invention generally relate to an apparatus for reinforcing the backing plate on a plasma enhanced chemical vapor deposition (PECVD) apparatus. 
         [0004]    2. Description of the Related Art 
         [0005]    Large area substrates may be used for the fabrication of numerous items used in society such as flat panel displays and solar cell panels. A large area substrate may exceed 2 square meters in surface area. To process these large area substrates, chamber size may also increase. One suitable apparatus that may be used to process large area substrates is a PECVD apparatus  700  as shown in  FIG. 7 . A substrate  704  is disposed in the processing chamber opposite to a gas distribution showerhead  702 . A backing plate  706  is disposed behind the showerhead  702  to create a plenum  708  between the showerhead  702  and the backing plate  706  for distribution of processing gas behind the showerhead  702 . For a PECVD chamber, the backing plate  706  may be at least as large as the large area substrate  704 . Hence, in a PECVD apparatus for processing large area substrates, the backing plate may exceed 2 square meters in surface area. By simply scaling up a processing chamber and increasing its surface area, the size and weight of the backing plate may eventually result in the center of the backing plate  706  sagging as shown in  FIG. 7  when the backing plate  706  retains the thickness of the smaller chambers. Therefore, there is a need in the art for a backing plate of sufficient size and mechanical strength to permit processing of large area substrates. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention generally relates to a backing plate reinforcement apparatus for use in a plasma enhanced chemical vapor deposition apparatus. When processing large area substrates, the backing plate extending across the chamber may also be quite large. By supporting a central area of the backing plate with a frame structure, the backing plate may be maintained substantially planar. Alternatively, as necessary, the contour of the backing plate may be adjusted to suit the particular needs of the process. 
         [0007]    In one embodiment, a plasma enhanced chemical vapor deposition apparatus is disclosed. The apparatus comprises a chamber body, a backing plate coupled with the chamber body and enclosing a processing area, and a frame structure disposed outside the processing area and coupled with a center area of the backing plate. 
         [0008]    In another embodiment, a backing plate reinforcement apparatus is disclosed. The apparatus comprises a bridge section, a plurality of legs extending from edge portions of the bridge section, and a support element suspended below a center portion of the bridge section, the support element suspended by one or more anchor elements that extend through the center portion of the bridge section and fasten to a top surface of the bridge section. The support element comprises one or more fasteners extending through the element and an electrically insulating element coupled with each fastener. 
         [0009]    In yet another embodiment, a method of controlling a shape of a backing plate is disclosed. The method comprises supporting a center portion of the backing plate with a support element extending from a frame assembly disposed above the backing plate and adjusting a distance that the support ring extends from the frame assembly to control the shape of the backing plate. 
         [0010]    In still another embodiment, a plasma enhanced chemical vapor deposition method is disclosed. The method comprises depositing a layer of material onto a substrate by plasma enhanced chemical vapor deposition in an apparatus, the apparatus comprising a backing plate coupled with a gas distribution showerhead, and a backing plate support coupled with the backing plate and disposed on a side of the backing plate opposite to the gas distribution showerhead, and adjusting a shape of the backing plate in the apparatus in response to a measured parameter of the depositing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0011]    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. 
           [0012]      FIG. 1  is a cross sectional view of a PECVD apparatus according to one embodiment of the invention. 
           [0013]      FIG. 2  is a top perspective view of a backing plate frame structure according to one embodiment of the invention. 
           [0014]      FIG. 3  is a cross sectional view of a top portion of a PECVD apparatus according to another embodiment of the invention. 
           [0015]      FIG. 4  is a top view of the support ring according to one embodiment of the invention. 
           [0016]      FIG. 5  is a cut away view of the anchor bolt mounted to the support ring of  FIG. 4 . 
           [0017]      FIG. 6  is a cut away view of the bolts through the backing plate and support ring of  FIG. 4 . 
           [0018]      FIG. 7  is a PECVD apparatus  700  having a sagging backing plate. 
       
    
    
       [0019]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
       DETAILED DESCRIPTION  
       [0020]    Embodiments of the present invention generally provide an apparatus and method for supporting a backing plate in a processing chamber. In one embodiment, the center area of the backing plate is coupled with a support ring that maintains the backing plate in a substantially planar orientation. It is understood that the substrate to be processed may be any suitable substrate such as a semiconductor substrate, a flat panel display substrate, a solar panel substrate, etc. 
         [0021]      FIG. 1  is a cross sectional view of a PECVD apparatus according to one embodiment of the invention. The apparatus includes a chamber  100  in which one or more films may be deposited onto a substrate  140 . One suitable PECVD apparatus which may be used is available from AKT, a subsidiary of Applied Materials, Inc., located in Santa Clara, Calif. While the description below will be made in reference to a PECVD apparatus, it is to be understood that the invention is equally applicable to other processing chambers as well, including those made by other manufacturers. 
         [0022]    The chamber  100  generally includes walls  102 , a bottom  104 , a showerhead  110 , and substrate support  130  which define a process volume  106 . The process volume  106  is accessed through a valve  108  such that the substrate  140  may be transferred in and out of the chamber  100 . The substrate support  130  includes a substrate receiving surface  132  for supporting a substrate  140 . One or more stems  134  may be coupled to a lift system  136  to raise and lower the substrate support  130 . A shadow ring  133  may be optionally placed over the periphery of the substrate  140 . Lift pins  138  are moveably disposed through the substrate support  130  to move a substrate  140  to and from the substrate receiving surface  132 . The substrate support  130  may also include heating and/or cooling elements  139  to maintain the substrate support  130  at a desired temperature. The substrate support  130  may also include grounding straps  131  to provide RF grounding at the periphery of the substrate support  130 . 
         [0023]    The showerhead  110  may be coupled to a backing plate  112  at its periphery by a suspension  114 . The showerhead  110  may also be coupled to the backing plate  112  by one or more coupling supports  160  to help prevent sag and/or control the straightness/curvature of the showerhead  110 . In one embodiment, twelve coupling supports  160  may be used to couple the showerhead  110  to the backing plate  112 . The coupling supports  160  may include a fastening mechanism such as a nut and bolt assembly. In one embodiment, the nut and bolt assembly may be made with an electrically insulating material. In another embodiment, the bolt may be made of a metal and surrounded by an electrically insulating material. In still another embodiment, the showerhead  110  may be threaded to receive the bolt. In yet another embodiment, the nut may be formed of an electrically insulating material. The electrically insulating material helps to prevent the coupling supports  160  from becoming electrically coupled to any plasma that may be present in the chamber. Additionally and/or alternatively, a center coupling mechanism may be present to couple the backing plate  112  to the showerhead  110 . The center coupling mechanism may surround the ring  148  (discussed below) and be suspended from a bridge assembly. In still another embodiment, the coupling supports  160  may comprise a fastener threaded into the showerhead  110 . The fastener may have a slotted opening for receiving a rod that is coupled to the backing plate  112 . The rod may be coupled to the backing plate  112  with a vacuum seal. 
         [0024]    A gas source  120  is coupled to the backing plate  112  to provide gas through a gas outlet  142  in the backing plate  112  and through gas passages  111  in the showerhead  110  to the substrate receiving surface  132 . A vacuum pump  109  is coupled to the chamber  100  to control the process volume  106  at a desired pressure. A RF power source  122  is coupled to the backing plate  112  and/or to the showerhead  110  to provide a RF power to the showerhead  110 . The RF power creates an electric field between the showerhead  112  and the substrate support  130  so that a plasma may be generated from the gases between the showerhead  110  and the substrate support  130 . Various frequencies may be used, such as a frequency between about 0.3 MHz and about 200 MHz. In one embodiment, the RF power source is provided at a frequency of 13.56 MHz. 
         [0025]    A remote plasma source  124 , such as an inductively coupled remote plasma source, may also be coupled between the gas source  120  and the backing plate  112 . Between processing substrates, a cleaning gas may be provided to the remote plasma source  124  to that a remote plasma is generated and provided to clean chamber components. The cleaning gas may be further excited by the RF power source  122  provided to the showerhead. Suitable cleaning gases include by are not limited to NF 3 , F 2 , and SF 6 . 
         [0026]    The spacing between the top surface of the substrate  140  disposed on the substrate receiving surface  132  and the showerhead  110  may be between about 400 mil and about 1,200 mil. In one embodiment, the spacing may be between about 400 mil and about 800 mil. The distance between the backing plate  112  and the showerhead  110  may be adjusted. 
         [0027]    The backing plate  112  may be supported by a bridge assembly  144 . One or more anchor bolts  146  may extend down from the bridge assembly  144  to a support ring  148 . The support ring  148  may be coupled with the backing plate  112  by one or more bolts  150 . The support ring  148  may be coupled with the backing plate  112  substantially in the center of the backing plate  112 . The center of the backing plate  112  is the area of the backing plate  112  with the least amount of support in absence of the support ring  148 . Therefore, supporting the center area of the backing plate  112  may reduce and/or prevent sagging of the backing plate. 
         [0028]    In one embodiment, the support ring  148  may be coupled to an actuator that controls the shape of the backing plate  112  so that the center of the backing plate  112  may be raised or lowered relative to the edges of the backing plate  112 . It is contemplated that by raising the center area of the backing plate, a vortex-like flow may be created to enable atomic layer deposition processes to be performed on large area substrates. The movement of the backing plate  112  may occur in response to a metric obtained during processing. In one embodiment, the metric is the thickness of the layer being deposited. The movement of the backing plate  112  may occur simultaneous with the processing. 
         [0029]    The support ring  148  may be integral with or separate from the supporting mechanism for the showerhead  110 . In one embodiment, one or more supporting elements may couple the showerhead  110  to the backing plate  112  at various locations while the support ring  148  is coupled to a center area of the backing plate  112 . In another embodiment, a center mounted coupling mechanism may be used to couple the backing plate  112  to the showerhead  110  while the support ring  148  is coupled to the center area of the backing plate  112 . When the showerhead  110  is center supported in addition to the support ring  148  of the backing plate  112 , the support ring  148  of the backing plate  112  may be disposed within the center support for the showerhead  110 . 
         [0030]    The distance between the bridge assembly  144  and the backing plate  112  may be adjusted as desired. In one embodiment, the distance between the bridge assembly  144  and the backing plate  112  may be adjusted in response to a measured metric of a processing condition. Additionally, when adjusting the distance between the bridge assembly  144  and the backing plate  112 , the distance between the showerhead  110  and the substrate may be adjusted whenever the showerhead  110  is coupled with the backing plate  112 . 
         [0031]      FIG. 2  is a top perspective view of a backing plate frame structure  200  according to one embodiment of the invention. A plurality of coupling mechanisms  224  may be visible which couple a showerhead to the backing plate to prevent showerhead plate sagging. In one embodiment, twelve coupling mechanisms  224  may be present. The edges of the backing plate  202  may rest on a lid body  204 . The center portion  222  of the backing plate, however, may be supported in the center by a support ring  208  suspended from a center area  218  of a bridge assembly  206 . A bridge section  220  of the bridge assembly  206  may span the width of the backing plate  202 . The edges of the bridge section  220  may be supported by one or more legs  216  that are coupled with the lid body  204 . 
         [0032]    The support ring  208  may be suspended from the center area  218  of the bridge section  220  by one or more anchor bolts  212 . The material of the anchor bolts may be any well known material of sufficient strength to support a large area backing plate  202 . In one embodiment, the anchor bolts  212  may comprise stainless steel. The support ring  208  may be coupled with the backing plate  202  by one or more bolts  210 . The bolts  210  may be electrically insulated from the backing plate  202  by insulators  214 . The insulators  214  may be made of any well known electrically insulating material. In one embodiment, the insulators are  214  ceramic. It is to be understood that while bolts  210 ,  212  have been described for coupling the support ring  208  to the backing plate  202 , and for coupling the support ring  208  to the center area  218  of the bridge section  220 , any fastening mechanism capable of coupling the elements together is contemplated. 
         [0033]      FIG. 3  is a cross sectional view of a top portion of a PECVD apparatus  300  according to another embodiment of the invention. The support ring  306  coupled to the backing plate  302  may be suspended from a bridge assembly  304  by one or more anchor bolts  308 . The anchor bolts  308  may be threaded at each end  310  for coupling to the support ring  306  and the bridge assembly  304 . At the bridge assembly  304 , a fastening mechanism  312 , such as a nut, may be threadedly coupled to the threaded end  310  of the anchor bolt  308 . 
         [0034]    At the support ring  306 , the anchor bolts  308  may be threadedly coupled to the support ring  306 . The support ring  306  may have a threaded portion for receiving the threaded end  310  of the anchor bolt  308 . By threadedly attaching the anchor bolt  308  to the support ring  306 , a fastening mechanism, such as a nut, may not be necessary on the underside of the support ring  306 . A nut on the underside of the support ring  306  may lead to undesired electrical coupling of the backing plate  302  to the bridge assembly  304 . However, in one embodiment, a nut may be disposed on the underside of the support ring  306  to couple with the anchor bolt  308 . In one embodiment, insulating fastening mechanisms may be used to couple the support ring  306  to the anchor bolts  308 . If an insulating nut is used to couple the anchor bolts  308  to the support ring  306 , the support ring  306  may or may not be threaded for receiving the anchor bolts  308 . By using both a threaded support ring  306  and a nut, the anchor bolts  308  may be further secured to the support ring  306 . When only a nut is used to couple the anchor bolts  308  to the support ring  306 , the portion of the support ring  306  through which the anchor bolts  308  pass may be substantially straight sided. 
         [0035]      FIG. 4  is a top view of a support ring  400  coupled to a backing plate  406  according to one embodiment of the invention. Anchor bolts  402  and bolts  404  have also been shown. While one or more anchor bolts  402  may be present, six anchor bolts  402  have been shown. It is to be understood that more or less anchor bolts  402  may be used. Additionally, while eight bolts  404  coupling the support ring  400  to the backing plate  406  are shown, it is to be understood that more or less bolts  404  may be used. 
         [0036]      FIG. 5  is a cut away view of the anchor bolt  402  mounted to the support ring  400  of  FIG. 4 . The anchor bolt  402  may have a threaded end  504  coupled with a threaded receiving portion  502  of the support ring  400 . As discussed above, the threaded end  504  may or may not additionally have a fastening mechanism in addition to, or in place of the threaded receiving portion  502 . In one embodiment, the threaded end  504  of the anchor bolt  402  may be coated with an electrically insulating material to reduce any electrical coupling between the backing plate  406  and the anchor bolt  402 . 
         [0037]      FIG. 6  is a cut away view of the bolts  404  through the backing plate  406  and support ring  400  of  FIG. 4 . Between the support ring  400  and the backing plate  406 , the bolts  404  may be electrically isolated by an insulating washer  602 . In one embodiment, the insulating washer  602  may be countersunk into the backing plate  406 . 
         [0038]    The end of the bolt  404  may be threadedly coupled to a threaded insulating nut  606  on the underside of the backing plate  406 . The insulating nut  606  may be countersunk into the backing plate  406 . The threaded end of the bolt  404  may not extend through the insulating nut  606 . If the threaded end of the bolt  404  extends through the insulating nut  606 , then the bolt  404  will be exposed to any plasma provided through the opening  608  in the backing plate  406 . By exposing the bolt  404  to the plasma, the bolt  404  will not be electrically insulated from the backing plate  406  and thus, may provide a path to ground. Thus, the insulating nut  606  may function as an insulating cap for the bolt  404 . 
         [0039]    Within the backing plate  406 , the bolt  404  may be electrically insulated from the backing plate  406  by an insulating sleeve  604  that extends between the insulating nut  606  and the insulating washer  602 . In one embodiment, the insulating material for each of the insulating washer  602 , the insulating sleeve  604 , and the insulating nut  606  may comprise a ceramic material. It is contemplated that any well known electrically insulating material may be used for each of the insulating washer  602 , the insulating sleeve  604 , and the insulating nut  606 . In one embodiment, the insulating washer  602 , insulating sleeve  604 , and insulating nut  606  may comprise a unitary piece of insulating material. 
         [0040]    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.