Patent Publication Number: US-11021794-B2

Title: Graphite susceptor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 14/863,063 filed Sep. 23, 2015, which claims benefit of Indian Provisional Patent Application Serial No. 4662/CHE/2014 filed Sep. 24, 2014, which is incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the present disclosure generally relate to methods and apparatus for semiconductor processing. More specifically, embodiments described herein relate to methods and apparatus for performing atomic layer epitaxy. 
     BACKGROUND 
     Temperature non-uniformity is a major design challenge in the design of Rapid Thermal Processing chambers. Temperature uniformity between 5° C. and 10° C. across a substrate is helpful in achieving a high quality of deposition or annealing all around the substrate. In this regard, temperature uniformity is defined as the difference between a maximum temperature measured at any point on a substrate and a minimum temperature measured concurrently at any point on the substrate. The substrate may be heated using conductive heaters or radiation. Several methods are conventionally used to control temperature uniformity of a substrate during processing, including use of reflective and/or absorptive shields, liners, specially designed coil layout inside the heater, and power supply control. Despite these measures, temperature uniformity still remains a major issue. Non-uniformity may result because of the differential heating of a substrate from the heater below. 
     Therefore, there exists a need for a susceptor that provides improved temperature uniformity of a substrate during thermal processing. 
     SUMMARY 
     Embodiments described herein provide a substrate support, comprising a support member; and an oriented graphite plate having a thickness of about 1 mm to about 10 mm disposed on the support member. 
     Other embodiments described herein provide a substrate support, comprising a support member; and a substrate support surface disposed on the support member, the substrate support surface comprising an oriented graphite plate having a thickness of about 1 mm to about 10 mm disposed within an outer member. 
     Other embodiments described herein provide a substrate support, comprising a susceptor having low thermal mass; and an oriented graphite plate disposed in a recess in contact with the susceptor, wherein the oriented graphite plate has a thickness between about 1 mm and about 10 mm and a substrate contact surface. 
    
    
     
       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 cutaway view of a substrate support according to one embodiment. 
         FIG. 2  is a cutaway view of a substrate support according to another embodiment. 
     
    
    
     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 
     Oriented graphite surfaces may be used in substrate supports for thermal processing of semiconductor substrates to promote temperature uniformity across the substrate. Embodiments described herein include a substrate support for semiconductor processing including a heat spreading surface made of oriented graphite. The heat spreading surface is a surface that would contact or be in close proximity to a semiconductor substrate during processing to transfer thermal energy to the semiconductor substrate. The heat spreading surface is a surface of a graphite plate that may have a thickness of 1 mm or more. The graphite plate is made using a carbon pyrolysis process to build the plate by layers of graphite. Often called “pyrolytic graphite”, such a material has thermal conductivity along the graphite layers that is at least 100 times the thermal conductivity across the layers. 
       FIG. 1  is a cutaway view of a substrate support  100  according to one embodiment. The substrate support  100  has a support member  102  on which an oriented graphite plate  104  is disposed. The oriented graphite plate  104  may have a thickness of about 1 mm to about 10 mm, for example about 4 mm. The oriented graphite plate is in contact with a heat transfer surface  105  of the support member  102 , which may be made of a thermally conductive material such as aluminum or aluminum nitride, or another metal. 
     The support member  102  may have a rim  108  at an edge  109  of the support member  102 . The rim  108  may define a recess  106  in which the oriented graphite plate  104  is disposed. The recess  106  may have a depth substantially equal to the thickness of the oriented graphite plate  104 , such that a contact surface  106  of the oriented graphite plate  104  is substantially coplanar with an upper surface  107  of the rim  108 . A ring  111  may be disposed on the heat transfer surface  105  inward of the rim  108 . The ring  111  may be used for edge thermal control of a substrate disposed on the substrate support  100 . 
     The ring  111  may include an edge conduit  110 . The edge conduit  110  may be a thermal conduit for housing a thermal control medium. The thermal control medium may be used to control thermal state at an edge of a substrate disposed on the contact surface  106 . The thermal control medium may be a fluid that is circulated through the edge conduit  110 , for example a liquid or gas, or the thermal control medium may be a solid material, such as a resistive heater or a heat sink member, disposed in the edge conduit  110 . 
     The support member  102  may be a susceptor, which may be heated by radiant or conductive means. In one embodiment, the support member  102  is made of silicon and carbon in any desired proportion. The support member  102  may be silicon carbide, or another mixture of silicon and carbon, which may be a molecular mixture, an alloy, or a structured mixture such as silicon carbide coated silicon or silicon carbide coated graphite. In other embodiments, the support member  102  may be ceramic, such as alumina, or metal, such as aluminum. 
     The support member  102  may have a center conduit  112  near a center of the support member  102 . The center conduit  112  may have an annular cross-sectional shape. The center conduit  112  may be used generally to provide energy to the support member  102 . For example, power for resistive heating, or thermal fluids for conductive heating or cooling, may be provided through the center conduit  112 . 
     In the embodiment of  FIG. 1 , the oriented graphite plate  104  is shown in contact with the support member  102 . In other embodiments, a separation layer may be disposed between the support member  102  and the oriented graphite plate  104 . The separation layer may be a coating to prevent contact between the oriented graphite plate  104  and the support member  102 , if desired. 
       FIG. 2  is a cutaway view of a substrate support  200  according to another embodiment. The substrate support  200  is generally similar to the substrate support  100 , except as described below. The substrate support  200  has a center conduit  112  similar to the substrate support  100 . The center conduit  112  may include a passage that couples the center conduit  112  to a surface of the support member  102  for vacuum chucking a substrate to the oriented graphite plate  104 . The center conduit  112  may be a thermal conduit for routing a thermal control element  114 . The thermal control element  114  may be a resistive heater, a heat sink, or a heating or cooling fluid circulated through the conduit  112 . The support member  102  may be substantially solid between the center thermal conduit  112  and the edge thermal conduit  110 , or the support member  102  may have a thermal element, such as the thermal control element  114 , distributed throughout, for example in a spiral pattern through the support member  102 . A plurality of such thermal elements may be included in the support member  102  to provide discrete thermal control zones. For example a first thermal control element may be located at and around the center of the support member  102  while a second thermal control element may be disposed around a periphery of the support member  102 . The thermal control elements described above may be fluid elements that flow through the support member  102  or solid elements that may provide resistive or conductive heating. Due to the high thermal conductivity of the oriented graphite plate  104 , temperature uniformity of a substrate disposed on the oriented graphite plate may be maintained at 5° C. or less, for example about 4° C. 
     The substrate support  200  has a support surface  202  that includes an oriented graphite plate  204  disposed within an outside member  206 . The oriented graphite plate  204  may be encapsulated in the outside member  206 , covered by the outside member  206 , or sandwiched between two outside member  206 . The outside member  206  may be made of a material that resist chemical attack from the processing environment used to process a substrate on the substrate support  200 . For example, the outside member  206  may be a ceramic material, such as alumina or yttria. In other embodiments, the outside member  206  may be silicon, silicon-carbon, or silicon carbide. In still other embodiments, the outside member  206  may be metal, such as aluminum or titanium, or glass, such as silica, quartz, or a doped glass. 
     The outside member  206  is shown in  FIG. 2  as a monolithic member, but the outside member  206  may also be a layered structure of different materials including any of the materials mentioned above. 
     The supporting surface  202  is generally disk-shaped in the substrate support  200 , and may be removably disposed on the support member  102 , adhered to the support member  102 , or attached to the support member  102 . A gap  208  may be provided between a periphery  210  of the supporting surface  202  and an inner radius  212  of the ring  111 . The gap  208  may be used to manage processing conditions near an edge region of a substrate disposed on the supporting surface  202 , for example by flowing a gas or other fluid in the gap  208 . The oriented graphite plate  204  may have a thickness of about 1 mm to about 10 mm, for example about 4 mm, and the outside member  206  may have a thickness of about 10 μm to about 5 mm. Thus, the outside member  206  may be a coating on the oriented graphite plate  204  in some embodiments. 
     The outside member  206  may be formed completely around the oriented graphite plate  204 , such that the oriented graphite plate  204  is enclosed by, or encapsulated by, the outside member  206 , or the outside member  206  may sandwich the oriented graphite plate  204 , such that the outside member  206  includes a first layer between the oriented graphite plate  204  and the support member  102  and a second layer over the oriented graphite plate  204  and forming a substrate contact surface. Alternately, the outside member  206  may be a layer over the oriented graphite plate  204 , where the oriented graphite plate  204  is in contact with the support member  102 . 
     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.