Abstract:
An apparatus and method for one or more externally mounted temperature sensors in a substrate support utilized in a chemical vapor deposition (CVD) chamber is provided. In one embodiment, a substrate support for a vacuum chamber is provided. The substrate support comprises a body having a substrate receiving surface and an opposing bottom surface, a support stem coupled to and extending away from the bottom surface, one or more thermal control devices embedded within the body, at least one temperature sensor interfaced with the bottom surface of the body, and a removable hermitic enclosure fastened to the second side of the body and covering the at least one temperature sensor.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. Provisional Patent Application Ser. No. 61/467,928 (Attorney Docket No. 11673USAL), filed Mar. 25, 2011, which is hereby incorporated by reference herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    Embodiments of the present invention generally relate to substrate supports having thermocouples for use in vacuum processing chambers, such as chemical vapor deposition (CVD) chambers, physical vapor deposition (PVD) chambers, etch chambers and plasma treatment chambers, among others. 
         [0004]    2. Description of the Related Art 
         [0005]    CVD is a process whereby a gas is introduced into a vacuum chamber to deposit a material layer onto a substrate. The gas may be dissociated prior to deposition on the substrate by dissociating the gas thermally and/or igniting the gas into a plasma (i.e., a PECVD process). There are many applications for utilizing a CVD or a PECVD process such as to deposit layers for a flat panel display (FPD), to deposit layers for a solar panel and to deposit layers for an organic light emitting display (OLED) to name a few. 
         [0006]    CVD chambers include a substrate support for supporting a substrate during deposition. The substrate support typically includes a means for thermal control (i.e., heating and/or cooling) disposed within or in proximity a body of the substrate support. The thermal control means is utilized to control the temperature of the substrate before, during, or after processing. Thus, monitoring the temperature of the substrate support is important in order to control the temperature of the substrate. One way to monitor the temperature of the substrate support is to use one or more temperature monitoring devices, such as a thermocouple, that are embedded within the body of the substrate support. The thermocouples are embedded such that vacuum is not compromised within the vacuum chamber. For example, the thermocouples and associated wiring are mounted through internal holes and passages formed within the body of the substrate support. 
         [0007]    However, thermocouples are subject to failure and require replacement during predetermined preventative maintenance operations. The embedded thermocouples are difficult to access as portions of the body of the substrate support must be removed by drilling or gouging to expose the thermocouple. The removal of material takes substantial time which causes increased downtime of the CVD chamber. Replacement is also difficult as the wiring and mounting of a new thermocouple takes substantial time. All of these operations cause considerable downtime of the CVD chamber when one or more of the thermocouples need to be replaced. Substrate supports utilized in other types of vacuum chambers have the same problem. 
         [0008]    Thus, there is a need in the art to for a method and apparatus that facilitates easy access and replacement of thermocouples within a substrate support for use in a vacuum chamber. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention generally relates to monitoring conditions in a chemical vapor deposition (CVD) chamber for processing substrates in the manufacture of flat-panel displays, light emitting diodes, or solar cells. In one aspect, a substrate support is provided having one or more externally mounted temperature sensors is provided. In another aspect, a method and apparatus for installing temperature sensors in a substrate support utilized in the CVD chamber is provided. The one or more temperature sensors may comprise a process kit for a new substrate support or a retrofit for a used substrate support. 
         [0010]    In one embodiment, a substrate support for a vacuum chamber is provided. The substrate support comprises a body having a substrate receiving surface and an opposing bottom surface, a support stem coupled to and extending away from the bottom surface, one or more thermal control devices embedded within the body, at least one temperature sensor interfaced with the bottom surface of the body, and a removable hermitic enclosure fastened to the second side of the body and covering the at least one temperature sensor. 
         [0011]    In another embodiment, a substrate support for a vacuum chamber is provided. The substrate support comprises a body having a substrate receiving surface and an opposing bottom surface, a support stem coupled to and extending away from the bottom surface, and a plurality of exterior mounted thermal monitoring assemblies disposed on the bottom surface of the body. 
         [0012]    In another embodiment, a method for installing one or more temperature sensors in a substrate support suitable for use in a vacuum chamber is provided. The method comprises cleaning the substrate support, drilling a blind hole in a bottom surface of the substrate support, placing a probe of a temperature sensor in the opening, and installing a cover over the temperature sensor, wherein the cover seals the temperature sensor in a volume that is isolated from the environment exterior of the cover and the volume is in fluid communication with an annulus of a support stem coupled to the body. 
         [0013]    In another embodiment, a process kit for use in a vacuum chamber is provided. The process kit comprises one or more temperature probes, one or more housings adapted to contain at least a portion of one of the one or more temperature probes, one or more conduits. Each of the one or more conduits comprise a fitting at a first end thereof, and a fitting at a second end thereof for coupling to one of the one or more housings, and one or more straps for coupling to the one or more conduits. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    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 selected embodiments of this invention and are not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
           [0015]      FIG. 1  is a side cross-sectional view of one embodiment of a substrate support disposed in an exemplary vacuum chamber. 
           [0016]      FIG. 2A  is a bottom plan view of the substrate support of  FIG. 1  with the support stem shown in cross-section. 
           [0017]      FIG. 2B  is an enlarged plan view of a portion of the support stem and a conduit of  FIG. 2A  showing one embodiment of a first coupling interface. 
           [0018]      FIG. 3  is a partial enlarged view of the support stem of  FIG. 2A  illustrating another embodiment of a first coupling interface. 
           [0019]      FIG. 4  is a side cross-sectional view of a portion of an exterior mounted thermal monitoring assembly coupled to the substrate support of  FIG. 1  showing another embodiment of a second coupling interface. 
       
    
    
       [0020]    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 
       [0021]      FIG. 1  is a side cross-sectional view of one embodiment of a vacuum chamber  100  suitable for processing substrates, such as wafers or flat media, in the manufacture of flat panel displays, solar panels, light emitting diodes (LEDs) or other electronic devices. For the sake of brevity and not by way of limitation, the vacuum chamber  100  is illustrated as a plasma enhanced chemical vapor deposition (PECVD) chamber. Embodiments described herein may also be utilized in vacuum chambers configured for other processes, such as physical vapor deposition (PVD) processes, etch processes, or other vacuum process on a substrate or multiple substrates. In addition, the vacuum chamber  100  may be a stand-alone chamber, an in-line chamber, a cluster tool chamber, or some combination or variation thereof. 
         [0022]    The vacuum chamber  100  is configured to receive a substrate  105  within an evacuable processing volume  110  defined inside walls of the vacuum chamber  100 . The vacuum chamber  100  includes a chamber body  115  containing the evacuable processing volume  110 . The evacuable processing volume  110  includes a substrate support  120 . The substrate support  120  has a body  122 , which has a substrate receiving surface  160  to support the substrate  105  and a bottom surface  124 . A gas distribution plate, such as a showerhead  125 , is also disposed within the evacuable processing volume  110  in an opposing relationship to the substrate support  120 . A processing region  130  is defined in the evacuable processing volume  110  between the showerhead  125  and the substrate  105 . The showerhead  125  facilitates dispersion of process gases from a gas source  135  into the processing region  130 . 
         [0023]    In operation, the substrate  105  is transferred by a robot into the evacuable processing volume  110  through a sealable port  140 . The substrate support  120  is coupled to an actuator  145  by a support stem  150 . A plurality of lift pins  155  are movably disposed through the substrate support  120  to facilitate transfer of the substrate  105 . The actuator  145  is operable to move the substrate support  120  at least in a vertical direction (Z direction) to facilitate placing the substrate  105  on the substrate receiving surface  160 . 
         [0024]    One or more process gases from the gas source  135  flow into the processing region  130  through openings in the showerhead  125 . The process gases may be dissociated and are deposited on an upper surface of the substrate  105  to form the basis of electronic devices. The electronic devices may be thin-film transistors (TFT&#39;s), light emitting diodes (LEDs), organic light emitting diodes (OLED&#39;s), solar cells, or other electronic devices. In one embodiment, the showerhead  125  may be coupled to a power source  165 , such as a radio frequency (RF) power source, to facilitate formation of a plasma of the process gases. Alternatively or additionally, the substrate  105  may be heated to facilitate dissociation of the process gases and deposition of materials thereon. In one embodiment, the substrate support  120  includes an integral thermal control device  170 , such as a resistive heater and/or conduits for flowing a heat transfer fluid. 
         [0025]    During processing, temperature of the substrate  105  is one of the important process controls utilized for the reliable fabrication of the structures used to form the electronic devices. The body  122  of the substrate support  120  may be made of a thermally conductive material, such as aluminum. The temperature of the substrate support  120  is thus indicative of the temperature of the substrate  105 . Therefore, monitoring of the temperature of the substrate  105  may be facilitated by monitoring the temperature of the substrate support  120 . 
         [0026]    In order to facilitate temperature monitoring of the substrate support  120 , one or more temperature sensors  175  are coupled to a bottom surface  124  of the substrate support  120 . Each of the one or more temperature sensors  175  are in communication with a controller  136  through signal leads that are contained within the support stem  150 . Each of the temperature sensors  175  provide a metric indicative of temperature (i.e., temperature data) of the substrate support  120  to the controller  136 . The controller  136  processes the temperature data and provides adjustment of the thermal control device  170  to adjust the temperature of the substrate support  120  and maintain a desired temperature profile. 
         [0027]      FIG. 2A  is a bottom plan view of the substrate support  120  of  FIG. 1 . In this embodiment, the substrate support  120  is partitioned into corner regions I-IV which indicate the location of temperature probes, such as the temperature sensors  175 . The corner regions I-IV shown indicate an area of the body of the substrate support  120  where temperature monitoring is desired. Temperature measurement may be desired and implemented in regions of the body of the substrate support  120  other than the corner regions I-IV but are not shown to avoid drawing clutter. For example, a temperature sensor  175  may be mounted near the center of the bottom surface  124 . Each corner region I-IV may comprise a surface area of the bottom surface  124  of the substrate support  120 . In one embodiment the surface area of each of the corner regions I-IV is about one-third of the surface area of the bottom surface  124 , or less, such as about one-fourth of the surface area of the bottom surface  124 , for example, about one-eighth of the surface area of the bottom surface  124 . 
         [0028]    Within each corner region I-IV, a cover  200  is attached to the bottom surface  124  of the substrate support  120  by fasteners  205 . Each of the covers  200  include an interior volume that houses a temperature sensor  175  (only one is shown in the cutaway in corner region II). Each of the covers  200  are coupled to a conduit  210  that extends between the cover  200  and the support stem  150 . The conduits  210  may comprise a flexible or rigid tubular member that is coupled to the substrate support  120  by fastening devices  215 , such as clips or straps. In one embodiment, the conduit  210  is a tube or a hose comprising a metallic material, such as aluminum. The fastening devices  215  are coupled to the substrate support  120  by fasteners  205 . The substrate support  120  also includes a plurality of through-holes  220  formed between the substrate receiving surface  160  (shown in  FIG. 1 ) and the bottom surface  124 . Each of the through-holes  220  may comprise bushings adapted to receive and facilitate movement of a lift pin  155  (shown in  FIG. 1 ). Each of the conduits  210  and the covers  200  are coupled to the substrate support  120  in a manner that does not cover a through-hole  220  and/or interfere with operation of the lift pins  155 . Thus, while the conduits  210  are shown in a straight line, the conduits  210  may include bends, curves or multiple joints in order to not limit movement or otherwise interfere with the operation of the lift pins  155 . 
         [0029]    In one embodiment, the support stem  150  is a tubular member having an annulus  225 . The annulus  225  serves as a conduit for wiring, control cables, and/or tubular members, to facilitate operation of components disposed within or on the substrate support  120 . For example, the annulus  225  contains cables  230  that facilitate communication between the temperature sensors  175  and the controller  136  (shown in  FIG. 1 ). The annulus  225  may also contain thermal control conduits  235  to facilitate operation of the thermal control device  170  (shown in  FIG. 1 ). The thermal control conduits  235  may be wires or cables adapted to control the temperature of the thermal control device  170 . Alternatively, the thermal control conduits  235  may be conduits adapted to flow a fluid, such as a gas or liquid, that is utilized in cooling or heating of the substrate support  120 . 
         [0030]    In one embodiment, each of the covers  200 , the temperature sensors  175  and conduits  210  are configured as a process kit comprising one or more exterior mounted thermal monitoring assemblies  240 . The process kit may also comprise the fastening devices  215  and fasteners  205 . In one aspect, the substrate support  120  comprises a plurality of exterior mounted thermal monitoring assemblies  240  that are coupled to the bottom surface  124 . In one embodiment, the exterior mounted thermal monitoring assemblies  240  are disposed radially from a center of the substrate support  120 . In another embodiment, the covers  200  (having temperature sensors  175  therein) are substantially equally spaced apart at each corner region I-IV. 
         [0031]    During operation, the substrate support  120  is disposed in the evacuable processing volume  110  (shown in  FIG. 1 ) which may be evacuated to about 0.1 milliTorr to about 100 Torr during processing. The annulus  225  of the support stem  150  provides a path for the cables  230  and thermal control conduits  235  to couple with the controller  136  and other components outside of the evacuable processing volume  110 . Thus, the annulus  225  is maintained at ambient pressure and the exterior mounted thermal monitoring assemblies  240  coupled thereto must be hermetically sealed to prevent leakage into the annulus  225 . The term “hermetic” or “hermetically” refers to a seal, bond or an enclosure utilizing a seal or bond, whether temporary or permanent, that facilitates isolation of one environment from another environment. 
         [0032]    In one embodiment, each of the plurality of exterior mounted thermal monitoring assemblies  240  include a first coupling interface  245  between the conduit  210  and the support stem  150 , and a second coupling interface  250  between the conduit  210  and the cover  200 . In one aspect, at least one of the first coupling interface  245  and second coupling interface  250  comprises a fused joint  255 , that may be formed by welding, soldering or brazing. In one embodiment, the fused joint  255  comprises a weld  260  (shown in corner region IV). 
         [0033]      FIG. 2B  is an enlarged plan view of a portion of the support stem  150  and a conduit  210  of  FIG. 2A  showing one embodiment of a first coupling interface  245 . The first coupling interface  245  comprises a plate  265  that is joined to the conduit  210  by a weld  260 . The plate  265  may be formed from a metallic material, such as aluminum. The plate  265  may also be formed on a radius that substantially equals the outside diameter of the support stem  150 . The plate  265  may be coupled to the support stem  150  by a plurality of fasteners  205 , such as bolts or screws. To facilitate routing of the cable  230  to the annulus  225 , an opening  270  may be formed in the support stem  150  by drilling. The plate  265  also includes an opening  275  that facilitates a path for the cable  230  from the conduit  210  to the opening  270  and into the annulus  225  of the support stem  150 . Holes for the fasteners  205  may also be drilled into the support stem  150  or the fasteners  205  may be self-drilling/self tapping screws. A seal  280 , such as an o-ring or gasket, may be sandwiched between the outer surface of the support stem  150  and the plate  265 . The seal  280  is compressed when the fasteners  205  are tightened against the support stem  150  to seal the openings  270  and  275 . 
         [0034]      FIG. 3  is an enlarged view of one embodiment of a first coupling interface  245  between the support stem  150  and the conduit  210  of  FIG. 2A . The first coupling interface  245  comprises a fitting  305  that facilitates sealable coupling between the conduit  210  and the support stem  150 . The fitting  305  may be a nipple, a union or other plumbing device having an internal cavity formed therein. The fitting  305  may be welded, pressed, or otherwise joined to the support stem  150  in a manner that facilitates access to an opening  310  formed in a wall of the support stem  150 . The opening  310  may be formed by drilling. The fitting  305  may be bonded or joined to the support stem  150  in a manner that facilitates a hermetic seal. 
         [0035]    In one embodiment, the fitting  305  is coupled to the support stem  150  by a threaded connection  315 . The opening  310  may be formed by drilling and/or tapping to form threads in the wall of the support stem  150 . The threaded connection  315  may include tapered threads that facilitate vacuum sealing at the interface between the fitting  305  and the support stem  150 . Alternatively or additionally, a seal  320 , such as an o-ring or gasket, may be compressed between an outer surface  325  of the support stem  150  and a body  330  of the fitting  305 . The exterior of the body  130  may also include flats (not shown) to facilitate holding and/or rotation of the fitting  305  while making the threaded connection  315 . The conduit  210  may be integrated with the fitting  305  prior to coupling with the support stem  150 . Alternatively, the conduit  210  may be sealingly coupled to the fitting  305  by welding or other bonding method that facilitates hermetic sealing of an interior region of the conduit  210 . 
         [0036]    In one embodiment, the conduit  210  couples to the fitting  305  by a threaded connection  335 . In one aspect, the conduit  210  includes a ferrule  340  that interfaces with the threaded connection  335 . The threaded connection  335  may include tapered threads that facilitate hermetic sealing of the ferrule  340  and the conduit  210  with the fitting  305 . Alternatively or additionally, seals  345 , such as an o-ring or gasket, may be compressed between surfaces of the fitting  305  and the conduit  210 . 
         [0037]      FIG. 4  is a side cross-sectional view of a portion of an exterior mounted thermal monitoring assembly  240  of  FIG. 2A . The cover  200  of the exterior mounted thermal monitoring assembly  240  is configured as a hermetic enclosure  400  having an interior volume  405 . The interior volume  405  houses at least a portion of a temperature sensor  175 . The temperature sensor  175  comprises a probe  410  and a mounting portion  415 . The probe  410  is disposed in an opening  420  that may be pre-formed in the bottom surface  124  of the body  122  of the substrate support  120 . Alternatively, the opening  420  may be formed in a retrofit operation, such as by drilling. The mounting portion  415  may be secured to the body  122  by a fastener  205 . The fastener  205  may be disposed in a pre-formed hole in the body  122  or the hole may be drilled and tapped in the body  122  by personnel in a retrofit operation. The hermetic enclosure  400  is adapted to be removable to access the temperature sensor  175  to facilitate inspection or replacement. The hermetic enclosure  400  comprises a flange  430  having holes formed therein to facilitate hermetic coupling to the body  122 . A seal  435 , such as an o-ring or gasket, may be disposed between the flange  430  and the bottom surface  124  of the substrate support  120  to facilitate hermetic sealing. 
         [0038]    The conduit  210  is coupled to the hermetic enclosure  400  by a second coupling interface  250 . The second coupling interface  250  comprises a fitting  445  that facilitates sealable coupling between the conduit  210  and an opening  450  in the cover  200 . The fitting  445  may be a nipple, a union or other plumbing device having an internal cavity formed therein. The fitting  445  may be welded, pressed, or otherwise joined to the cover  200  in a manner that facilitates a hermetic seal. 
         [0039]    In one embodiment, the fitting  445  is coupled to the cover  200  by a threaded connection  455 . A ferrule  460  may be disposed on the conduit  210  that is adapted to couple to the fitting  445 . The threaded connection  455  may include tapered threads that facilitate vacuum sealing at the interface between the fitting  445  and the cover  200  as well as the ferrule  460  and the fitting  445 . Alternatively or additionally, one or more seals  320 , such as an o-ring or gasket, may be compressed between the ferrule  460 , the cover  200  and/or the ferrule  460  and the fitting  445 . One or more fastening devices  215 , such as clips or straps, may be provided to secure the conduit  210  to the substrate support  120 . The fastening devices  215  are coupled to the substrate support  120  by fasteners  205  (shown in  FIG. 2A ), that may be bolts or screws. 
         [0040]    In one embodiment, the substrate support  120  utilized in the vacuum chamber  100  of  FIG. 1  may include one or more exterior mounted thermal monitoring assemblies  240 . The substrate support  120  may be cleaned before installation of the exterior mounted thermal monitoring assemblies  240 . The locations of the exterior mounted thermal monitoring assemblies  240  may be determined and laid out on the bottom surface  124  of the substrate support  120  and the support stem  150 . The locations of thermal control devices  170  (shown in  FIG. 1 ) in the substrate support  120  should also be identified to prevent damage to the thermal control devices by machining during the installation procedure. The substrate support  120  may be cleaned after installation. The temperature sensors  175  may be tested and the substrate support  120  may be packaged for transit or installed in a chamber. 
         [0041]    In another embodiment, the substrate support  120  may be retrofitted with one or more exterior mounted thermal monitoring assemblies  240 . In one aspect the one or more exterior mounted thermal monitoring assemblies  240  comprise a process kit that may be utilized with the substrate support  120  and the vacuum chamber  100  of  FIG. 1 . 
         [0042]    In one embodiment of a retrofit operation, the substrate support  120  may be removed from the chamber body  115 . Alternatively, the substrate support  120  may remain in the chamber body  115  if the bottom surface  124  is readily accessible. The substrate support  120  may be cleaned prior to any handling by personnel to remove deposition residue. The locations of the existing temperature probes should be identified to facilitate placement of the to-be-installed temperature sensors  175 . The existing temperature probes need not be removed. In one embodiment, the to-be-installed temperature sensors  175  are installed in proximity to the locations of any existing temperature probes. This facilitates temperature measurements in or near the same locations of the substrate support  120 , which provides continuity in the temperature measurement and control. The locations of thermal control devices  170  in the substrate support  120  should also be identified to prevent damage to the thermal control devices  170  by machining during the retrofit procedure. 
         [0043]    An opening  310  (shown in  FIG. 3 ) may be formed in the support stem  150  for each of the one or more exterior mounted thermal monitoring assemblies  240 . The opening  310  may be formed by drilling. The opening  420  may include threads, which are formed by tapping and/or disposing a threaded insert into the opening  310 . The threads of the opening  310  are provided to engage the mating threads of the fitting  305 . 
         [0044]    In the corner regions I-IV of the substrate support  120  (shown in  FIG. 2A ), an opening  420  (shown in  FIG. 4 ) may be formed for each temperature sensor  175  to be installed. The opening  420  may be a blind hole having a depth and diameter that receives the probe  410 . The location of the opening  420  should be proximate to the existing temperature sensor. The opening  420  and mounting holes for securing the mounting portion  415  of the probe  410  may be formed by drilling. Threads may be utilized, if needed, with the opening  420  and/or the mounting hole for the fastener  205  in mounting the probe  410 . The threads are formed by tapping and/or disposing a threaded insert into the mounting hole and the opening  420  as needed. 
         [0045]    Prior to securing the cover  200  to the substrate support  120 , the temperature sensor  175  may be installed by inserting the probe  410  into the opening  420 . The mounting portion  415  may be secured to the body  122  of the substrate support  120  by one or more fasteners  205 . The cable  230  may be routed through the second coupling interface  250 , the conduit  210 , the first coupling interface  245 , and into the annulus  225  of the support stem  150  to be coupled with the controller  136  outside of the evacuable processing volume  110 . The cover  200  and coupling interfaces  245  and  250  may be sealingly coupled such that the environment of the interior volume  405  of the hermetic enclosure  400  is maintained substantially the same as the environment of the annulus  225  of the support stem  150 . After installation, the substrate support  120  may be cleaned and re-installed in the chamber body  115 . 
         [0046]    Embodiments of the exterior mounted thermal monitoring assemblies  240  described herein provide a less expensive and less time intensive approach to installation or replacement of temperature sensors  175  in a substrate support  120 . The exterior mounted thermal monitoring assemblies  240  provide a hermetic seal between the environment where the temperature sensor  175  is located and the evacuable processing volume  110  where the substrate support  120  will be used. The exterior mounted thermal monitoring assemblies  240  may be coupled to the substrate support  120  to maintain vacuum integrity of the substrate support  120  and the support stem  150 . The exterior mounted thermal monitoring assemblies  240  may be installed without the need for additional bonding or sealing processes, such as soldering. The exterior mounted thermal monitoring assemblies  240  may be prefabricated and readied for an installation or retrofit procedure at a low cost. Thus, installation time and operating costs are minimized, as well as chamber downtime, which increases efficiency and throughput. 
         [0047]    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.