Patent Publication Number: US-2010112212-A1

Title: Adjustable gas distribution apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 61/110,210, filed Oct. 31, 2008, which is herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     Embodiments of the present invention provide apparatus and methods for adjusting the contour of a gas distribution plate. 
     2. Description of the Related Art 
     As demand for larger solar panels and flat panel displays continues to increase, so must the size of substrates and chambers for processing the substrates. One method for depositing material onto a substrate for solar panels or flat panel displays is plasma enhanced chemical vapor deposition (PECVD). In PECVD, process gases are typically introduced across a gas distribution plate in a process chamber through a central gas feed orifice. The process gases diffuse through the gas distribution plate and are ignited into plasma by an RF current applied to the gas distribution plate. The plasma envelops a substrate disposed in a process region of the chamber and deposits thin films on the surface of the substrate. 
     As substrate sizes increase, depositing uniform films on the substrate becomes increasingly difficult. Therefore, there is a need in the art for an apparatus and method for adjusting the contour of a gas distribution panel in a process chamber to provide improved film deposition uniformity. 
     SUMMARY OF THE INVENTION 
     In one embodiment of the present invention, a process chamber comprises a chamber body having walls, a bottom, and a backing plate defining a pressure tight volume, a gas distribution plate coupled to the backing plate about a peripheral region thereof, a central support member coupled to an upper surface of the gas distribution plate and extending through the backing plate, a sealing member disposed between the backing plate and the central support member, a lift mechanism disposed outside of the pressure tight volume and coupled to the central support member to move the central support member with respect to the backing plate, and an actuator disposed outside of the pressure tight volume configured to activate the lift mechanism. 
     In another embodiment, a process chamber comprises a chamber body having walls, a bottom, and a backing plate defining a pressure tight volume, a gas distribution plate coupled to the backing plate about a peripheral region thereof, a first plurality of support members coupled to an upper surface of the gas distribution plate and extending through the backing plate, a sealing member disposed between each support member and the backing plate, and one or more first actuators disposed outside of the pressure tight volume and coupled to at least one of the first plurality of support members for moving the support member with respect to the backing plate. In one embodiment, the first plurality of support members are capable of being actuated from outside of the pressure tight volume to move regions of the gas distribution plate coupled to each support member. 
     In yet another embodiment of the present invention, a method for processing a substrate comprises placing the substrate onto a substrate support opposite a gas distribution plate inside a process chamber, establishing a vacuum processing condition inside the process chamber, introducing a process gas into the chamber, and automatically altering the surface contour of the gas distribution plate without altering the pressure condition within the process chamber. 
    
    
     
       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 a process chamber according to one embodiment of the present invention. 
         FIG. 2  is a schematic, cross-sectional view of a process chamber according to another embodiment of the present invention. 
         FIG. 3  is a schematic, top view of a backing plate of a process chamber according to one embodiment of the present invention. 
         FIG. 4  is a schematic, top view of a backing plate of a process chamber according to another embodiment of the present invention. 
         FIGS. 5A ,  5 B, and  5 C schematically depict examples of altering the contour of the gas distribution plate according to certain embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     During processing, thermal conditions within a process chamber may cause deformity in or drooping of a gas distribution plate disposed therein. Additionally, thermal conditions within the process chamber may cause deformity in a substrate support disposed within the process chamber for supporting the substrate. Either condition may result in differences in the distance between the substrate and the gas distribution plate across the surface of the substrate, which may lead to deposition non-uniformities. 
     Embodiments of the present invention generally provide apparatus and methods for altering the contour of a gas distribution plate within a process chamber without breaking vacuum conditions within the chamber. In one embodiment, a central support device is adjusted to vary the height of a central region of a gas distribution plate with respect to the periphery of the gas distribution plate. In another embodiment, a plurality of central support devices is adjusted to vary the height of a central region of a gas distribution plate with respect to the periphery of the plate. In yet another embodiment, a plurality of central support devices and a plurality of mid-range support devices are adjusted to vary the height of certain regions of the gas distribution plate with respect to other regions of the gas distribution plate. In one embodiment, the contour of the gas distribution plate is altered based on changes detected within the process chamber. By providing adjustment of the contour of a gas distribution plate within a process chamber without breaking vacuum, the thickness of a film deposited on certain regions of a substrate within the chamber may be adjusted and tuned in situ resulting in improved deposition uniformity with minimal process interruptions. 
     The invention is illustratively described below in reference to a chemical vapor deposition system, processing large area substrates, such as a PECVD system, available from Applied Materials, Inc., Santa Clara, Calif. However, it should be understood that the apparatus and method may have utility in other system configurations. 
       FIG. 1  is a schematic, cross-sectional view of a process chamber  100  according to one embodiment of the present invention. The process chamber  100  generally includes walls  102 , a bottom  104 , a gas distribution plate  110 , and a substrate support  130 , which cumulatively define a process volume  106 . The process volume may be accessed through a valve opening  108  such that a substrate  101  may be transferred into and out of the process chamber  100 . The substrate support  130  includes a substrate receiving surface  132  for supporting the substrate  101  and a stem  134 , which may be coupled to a lift system  136  to raise and lower the substrate support  130 . Lift pins  138  are moveably disposed through the substrate support  130  to move the substrate  101  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 RF return straps  131  to provide a shortened return path for RF current from the substrate support  130  to an RF power source  122 . 
     In one embodiment, the gas distribution plate  110  is coupled to a backing plate  112  at its periphery by a suspension  114 . The gas distribution plate  110  includes a plurality of gas passages  111  disposed therethrough. A gas source  120  is coupled to the backing plate  112  to provide gas through the backing plate  112  and through the gas distribution plate  110  to the substrate  101 . A vacuum pump  109  is coupled to the process chamber  100  to control the process volume  106  at a desired pressure. The RF power source  122  is coupled to the backing plate  112  to provide an RF current to the gas distribution plate  110  so that an electric field is created between the gas distribution plate  110  and the substrate support  130  such that plasma may be generated from process gases disposed between the gas distribution plate  110  and the substrate support  130 . A cover plate  116  may be disposed above the backing plate  112 . 
     In one embodiment, the gas distribution plate  110  is adjustably coupled to the backing plate  112  via a central support member  150 . In one embodiment, the central support member  150  is mechanically coupled to a central region of the gas distribution plate  110 , such as by a slot and key, welded, or other mating connection such that if the central support member  150  is raised or lowered, the central region of the gas distribution plate  110  is correspondingly raised or lowered. 
     Additionally, a sealing mechanism  155  is disposed between the central support member  150  and the backing plate  112  to maintain a pressure tight seal between the central support member  150  and the backing plate  112 . In one embodiment, the sealing mechanism  155  comprises one or more o-ring seals, such as silicone elastomer seals. In another embodiment, the sealing mechanism  155  comprises a bellows  155 A, such as aluminum or stainless steel bellows. Other embodiments comprise other sealing mechanisms such that the central support member  150  may be raised or lowered without affecting the pressure conditions within the process chamber  100 . 
     In one embodiment, the central support member  150  may be raised or lowered with respect to the backing plate  112  in order to raise or lower the central region of the gas distribution plate  110  with respect to the periphery of the gas distribution plate  110 . In one embodiment, the central support member  150  may be manually raised and lowered via a lift mechanism  160  disposed outside of the process chamber  100 , such that the central support member  150  may be manually raised and lowered without altering vacuum or other processing conditions within the process chamber  100 . In one embodiment, the lift mechanism  160  may comprise a configuration using jacking screws (not shown) to lift and/or lower the central support member  150  with respect to the backing plate  112 . Other embodiments may comprise other lifting configurations, such as other screw or linear jacking configurations. 
     In another embodiment, the central support member  150  may be automatically raised and lowered via an actuator  170  responding to commands sent by a controller  180 . In one embodiment, the actuator  170  may be a linear motor. In another embodiment, the actuator  170  may include one or more pneumatic or hydraulic cylinders. In still other embodiments, the actuator may include electric or pneumatic rotary/screw type lifting mechanisms, rotary motors, or the like. Regardless of the type of actuator  170  used, the actuator  170  and/or lift mechanism  160  are disposed outside of the process chamber  100 , such that such that the central support member  150  may be manually raised and lowered without altering vacuum or other processing conditions within the process chamber  100 . 
     The controller  180  may include a central processing unit (CPU) (not shown), memory (not shown), and support circuits (or I/O) (not shown). The CPU may be one of any form of computer processors that are used in industrial settings for controlling various system functions, substrate movement, chamber processes, and support hardware, and monitor the processes. The memory is connected to the CPU, and may be one or more of a readily available memory, such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored within the memory for instructing the CPU. The support circuits are also connected to the CPU for supporting the processor in a conventional manner. The support circuits may include cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. A program (or computer instructions) readable by the controller  180  determines which tasks are performable. 
     In the embodiment of the present invention described with respect to  FIG. 1 , the contour of the gas distribution plate  110  may be altered between concave, planar, and convex shapes according to desired process and deposition conditions. Additionally, the contour of the gas distribution plate  110  may be altered either manually or automatically without breaking vacuum within the process chamber  100 . Thus, the deposition uniformity across the surface of the substrate  101  may be tuned as desired in situ resulting in improved deposition uniformity with minimal process interruptions. 
       FIG. 2  is a schematic, cross-sectional view of a process chamber  200  according to another embodiment of the present invention. The process chamber  200  is similar to the process chamber  100  depicted in  FIG. 1 , and as such, identical reference numbers are shown to reflect identical chamber parts without further description. 
     In one embodiment, as shown in  FIG. 2 , the gas distribution plate  110  is adjustably coupled to a backing plate  212  via a plurality of support members  250 . In one embodiment, the plurality of support members  250  are mechanically coupled to the gas distribution plate  110 , such as by screwed, welded, or other mating connection such that when the plurality of central support members  250  are raised or lowered, the corresponding region of the gas distribution plate  110  is raised or lowered. 
     Additionally, each support member  250  may have a sealing mechanism  255  disposed between the support member  250  and the backing plate  212  to maintain a pressure tight seal between the support member  250  and the backing plate  212 . In one embodiment, the sealing mechanism  255  comprises one or more o-ring seals, such as silicone o-rings. In another embodiment, the sealing mechanism  255  comprises a bellows  255 A, such as aluminum or stainless steel bellows. Other embodiments comprise other sealing mechanisms such that each support member  250  may be raised or lowered without affecting the pressure conditions within the process chamber  200 . 
     In one embodiment, each support member  250  may be raised or lowered with respect to the backing plate  212  in order to raise or lower the central region of the gas distribution plate  110  with respect to the periphery of the gas distribution plate  110 . In one embodiment, each support member  250  may be a threaded screw member that may be either manually adjusted or automatically adjusted via an actuator  270 . In one embodiment, a single actuator  270  is configured to automatically adjust a single support member  250 . In another embodiment, a single actuator  270  is configured to automatically adjust more than one support member  250 . In either case, adjustment may be made without breaking the vacuum seal of the process chamber  200 . In one embodiment, the actuator  270  may include a motor for applying torque to a screw member of the support member  250 . The actuator  270  may be controlled by the controller  180 . 
     In one embodiment, each support member  250  may be a rod or bar comprising a material such as aluminum, stainless steel, or a ceramic material. In one embodiment, the plurality of support members  250  may be, individually or collectively, manually raised and lowered via a lift mechanism  260  disposed outside of the process chamber  200 . In one embodiment, the lift mechanism  260  may comprise one or more jacking screws (not shown) to lift and/or lower the support members  250  with respect to the backing plate  212 . Other embodiments may comprise other lifting configurations, such as other screw or linear jacking configurations. In one embodiment, the support member  250  may be externally threaded to mate with internally threaded apertures in the backing plate or internally threaded components not shown attached to the backing plate. 
     In another embodiment, the support members  250  may be, individually or collectively, automatically raised and lowered via an actuator  270  responding to commands sent by the controller  180 . In one embodiment, the actuator  270  may be a linear or rotary motor. In another embodiment, the actuator  270  may include one or more pneumatic or hydraulic cylinders. In still other embodiments, each support member  250  may include the actuator  270 , such as a cylinder controlled by the controller  180 . Regardless of the type of actuator  270  used, the actuator  270  and/or lifting mechanism  260  are disposed outside of the process chamber  200 , such that such that the support members  250  may be raised and lowered without altering vacuum or other processing conditions within the process chamber  200 . 
       FIG. 3  schematically depicts one embodiment of a top view of the backing plate  212  from  FIG. 2 . In this embodiment, the support members  250  are arranged in a circular pattern about a central region of the backing plate  212 . In one embodiment, the lifting mechanism  260  or the actuator  270  may raise or lower the plurality of support members  250  simultaneously or one or more at a time a substantially identical amount in order to provide a substantially convex, planar, or concave surface contour to the gas distribution plate  110 . In another embodiment, the lifting mechanism  260  or the actuator  270  may adjust one or more of the central support members  250  in different amounts to provide other contours to the gas distribution plate  110 . 
       FIG. 4  schematically depicts another embodiment of a top view of the backing plate  212  from  FIG. 2 . In this embodiment, a first plurality of support members  250  is arranged in a circular pattern about a central region of the backing plate  212 . Additionally, a second plurality of support members  250  is arranged in a pattern between the first plurality of support members  250  and the periphery of the backing plate  212 . In one embodiment, the lifting mechanism  260  or the actuator  270  may raise or lower all the support members  250  a substantially identical amount to provide a desired contour to the gas distribution plate  110 . In another embodiment, one lifting mechanism  260  or actuator  270  may raise or lower the first plurality of support members  250  a different amount than another lifting mechanism  260  or actuator  270  raises or lowers the second plurality of support members  250  to provide a desired contour to the gas distribution plate  110 . In yet another embodiment, one or more lifting mechanisms  260  or actuators  270  may raise or lower one or more of the support members  250  different amounts to provide a contorted contour to the gas distribution plate  110 . 
     In the embodiment of the present invention described with respect to  FIGS. 2 ,  3 , and  4 , the contour of the gas distribution plate  110  may be altered between concave, planar, convex, and other contorted shapes according to the desired process and deposition conditions. 
       FIGS. 5A ,  5 B, and  5 C schematically depict examples of altering the contour of the gas distribution plate  110  according to certain embodiments of the present invention.  FIG. 5A  schematically depicts the gas distribution plate  110  supported in a planar configuration by support members  250 .  FIG. 5B  schematically depicts the support members  250  raising the central region of the gas distribution plate  110  to provide a concave lower surface contour to the gas distribution plate  110 .  FIG. 5C  schematically depicts raising one region of the gas distribution plate  110 , while forces another region of the gas distribution plate  110  downwardly, resulting in a contorted lower surface contour to the gas distribution plate  110 . These figures are only exemplary as numerous other gas distribution plate  110  lower surface contours may be achieved by applying different forces to different regions of the gas distribution plate via the respective support members  250 . 
     Additionally, the contour of the gas distribution plate  110  may be altered either manually or automatically without breaking vacuum within the process chamber  200 . Thus, the deposition uniformity across the surface of the substrate  101  may be tuned as desired in situ resulting in improved deposition uniformity with minimal process interruptions. 
     In one embodiment of the present invention described with respect to  FIGS. 2-4 , the process chamber  100  and/or  200  may further include sensors  199  for detecting changes within the system requiring adjustment of the surface contour of the gas distribution plate  110 . The sensors  199  may be temperatures sensors, position sensors, displacement sensors, or the like. For instance, sensors  199  may be embedded in either the gas distribution plate  110  or the substrate support  130  for detecting changes in the distance between the gas distribution plate  110  and the substrate support  130  across the surfaces thereof. Alternatively, sensors  199  may be embedded within the gas distribution plate  110  for detecting a change in the surface contour thereof due to process conditions within the process chamber  100  or  200 . Additionally, sensors  199  may be embedded within the substrate support  130  for detecting a change in the surface contour thereof due to process conditions within the process chamber  100  or  200 . In another embodiment, sensors  199  may be positioned in other locations within the chamber to detect process conditions, such as thermal conditions, requiring adjustment of the surface contour of the gas distribution plate  110 . Regardless of the type or position of sensors used, the sensors may send signals to the controller  180 , which in turn sends signals for adjusting the surface contour of the gas distribution plate  110 , all without breaking vacuum within the process chamber  100  or  200 . 
     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.