Abstract:
A susceptor assembly and an insulator strip for a susceptor assembly to reduce or eliminate arcing and temperature spikes between a ground cable and a thermocouple wire in susceptor and C-chuck assemblies. In one embodiment of the invention, an insulator strip is placed between the thermocouple lead and the ground cable in a susceptor assembly support arm channel.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    This invention relates generally to the field of susceptor assemblies as generally used to process semiconductor substrates and more particularly to an insulator for placement between a ground conductor and a thermocouple lead.  
           [0003]    2. Background Art  
           [0004]    Susceptor and C-chuck assemblies are commonly used in processing chambers to support a wafer opposite a gas distribution plate. U.S. Pat. No. 5,522,937 to Chew, et al. entitled  Welded Susceptor Assembly , which is incorporated by reference herein, discloses a susceptor assembly for use in a substrate processing chamber. The susceptor assembly includes a ceramic susceptor support arm having a channel formed along an underside of the support arm and an opening in the susceptor end of the ceramic susceptor support arm. A ground connection passes through the channel between the susceptor and a ground. The ground conductor is typically configured as a wire rope or cable, preferably made of aluminum, which is conductively connected at a first end to the susceptor disk and at a second end to a system ground. Similarly, a thermocouple lead passes through the channel to a thermocouple. A set of grooves in the bottom sides of the channel slidably receive a channel cover to isolate the ground wire and a thermocouple lead from the processing chamber environment.  
           [0005]    Failure of susceptor and C-chuck assemblies has in some instances been traced to two causes, thermocouple failures due to arcing from the ground cable to a nickel sheath surrounding the thermocouple wires, or internal thermocouple faults relating to junction or grounding problems. The result of a failure is premature removal and replacement of the C-chuck assembly during operation or failure-on-install.  
           [0006]    There may be advantage found in developing an apparatus and/or method for isolating or insulating the ground cable and thermocouple lead as they pass through the support arm of a susceptor assembly.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to an insulator strip for a susceptor assembly to reduce or eliminate arcing and temperature spikes between the ground cable and the thermocouple wire in susceptor and C-chuck assemblies. In one embodiment of the invention, an insulator strip is placed between the thermocouple lead and the ground cable in a susceptor assembly support arm channel. The insulator strip may be shaped to conform to the geometry of the channel in the support arm. Preferably, the insulator strip is made to fit within the channel of the support arm somewhat loosely in order to facilitate installation and to reduce the chances of breakage in installation and operation. The insulator strip should be adequately held in place by the ground cable, support arm cover, and surrounding components.  
           [0008]    The insulator strip is preferably constructed of 99.5% aluminum oxide, or the same material as support arm. The insulator strip may be configured having a bend at one end to facilitate the bend of the thermocouple from the arm down to the platter as well as a backside locking member to hold the insulator strip in place and provide limited protection of the thermocouple as it is routed from the support arm to a housing body.  
           [0009]    It will be noted that the support arm channel may have to be enlarged to accommodate the addition of the insulator strip between the ground cable and the thermocouple. The support arm of existing susceptor and C-chuck assemblies may be modified to include a shallow groove running along the inside bottom of the support arm to accommodate the added combined thicknesses of the thermocouple, the insulator strip and the ground cable. The groove may also serve to keep the thermocouple sheath centered in the arm and to minimize the possibility of crushing damage to the insulative sheath of the thermocouple.  
           [0010]    The present invention consists of the device and system hereinafter more fully described, illustrated in the accompanying drawings and more particularly pointed out in the appended claims, it being understood that changes may be made in the form, size, proportions and minor details of construction without departing from the spirit or sacrificing any of the advantages of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a representative cross-section of a processing chamber including a susceptor assembly;  
         [0012]    [0012]FIG. 2 Is a representative blow-up view of a susceptor support arm, thermocouple lead, grounding conductor, channel cover and an insulator strip according to the present invention;  
         [0013]    [0013]FIG. 3 is a representative top view of a susceptor support arm according to the present invention;  
         [0014]    [0014]FIG. 4 is a representative side view of a susceptor support arm according to the present invention;  
         [0015]    [0015]FIG. 5 is a representative bottom view of a susceptor support arm according to the present invention;  
         [0016]    [0016]FIG. 6 is a representative cross-section of a susceptor support arm according to the present invention;  
         [0017]    [0017]FIG. 7 is a representative top view of an insulator strip according to the present invention;  
         [0018]    [0018]FIG. 8 is a representative side view of an insulator strip according to the present invention;  
         [0019]    [0019]FIG. 9 is a representative side view of an insulator strip according to the present invention;  
         [0020]    [0020]FIG. 10 is a representative side view of an insulator strip according to the present invention;  
         [0021]    [0021]FIG. 11 is a representative cross-section of an insulator strip according to the present invention;  
         [0022]    [0022]FIG. 12 is a representative side view of an insulator strip according to the present invention; and  
         [0023]    [0023]FIG. 13 is a representative cross-section of an insulator strip according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    Referring to in FIG. 1, a typical configuration of a vapor deposition processing chamber  10  is shown including susceptor assembly  20  according to one embodiment of the invention. Susceptor assembly  20  is shown including susceptor plate  21 . Susceptor plate  21  is backed by ceramic plate  23  which supports wafer  50 . Susceptor plate  21  and ceramic plate  23  are supported by susceptor support arm  30  at susceptor hub receiver end  22 . Susceptor support arm  30  is made of a ceramic material, preferably 99.5% alumina. A process gas flows through holes  11  formed in electrically biased gas distribution plate  12 . Gas distribution plate  12  may be energized by the use of RF power which causes the process gas to form a plasma. Susceptor plate  21  is grounded by grounding conductor  32  which extends through an interior cavity of susceptor support arm  30 . Thermocouple lead  33  is shown extending from a lower end of arm  50 . During processing, susceptor disk  21  is heated by radiant heat from heating lamps  13  shining through a sealed quartz window  14 . Susceptor temperatures may reach approximately 475 to 500 degrees Celsius.  
         [0025]    Referring to FIG. 2, susceptor support arm  30  includes channel  31  formed along a length of mid-section  24  to carry grounding conductor  32  which, in the preferred embodiment, is configured as a wire rope. Grounding conductor  32  passes through channel  31  formed on the interior of susceptor support arm  30  and terminates at first end  36  at ground receiving hole  37 , shown in FIG. 4, formed in susceptor plate  21 . A second end of grounding conductor  32  is secured to wall  15  of processing chamber  10  by connector  16 , as shown in FIG. 1. Thermocouple lead  33  is also routed through channel  31  and terminates at first end  34  in a thermocouple receiving hole  35 , shown in FIG. 4, formed in susceptor plate  21 . Insulator strip  40  is disposed between grounding conductor  32  and thermocouple lead  33 . Susceptor support arm  30  includes susceptor hub receiver end  22  and bellows end  27 .  
         [0026]    Grooves  35 A and  35 B formed in the sides of channel  31  slidably receive channel cover  36  to block radiation from the radiant heat lamps  13 , shown in FIG. 1. Grooves  35 A and  35 B inside susceptor support arm channel  31  extend generally parallel to a throat of susceptor support arm  30  and around an inner perimeter of susceptor hub receiver end  22 . Channel cover  36  is sized to fully cover susceptor support arm channel  31 .  
         [0027]    [0027]FIGS. 3, 4 and  5  are details showing susceptor support arm  30  including susceptor hub receiver end  22  and bellows end  27  connected by mid-section  24 . As seen in FIGS. 3 and 5, keyhole shaped slot  26  is formed in susceptor hub receiver end  22  and permits for clearance and passage of grounding conductor  32  as seen in FIG. 4. Screw holes  28 A and  28 B are sized to receive fasteners to permit connection of susceptor plate  21  and ceramic plate  23  to susceptor support arm  30  at susceptor hub receiver end  22 , as shown in FIG. 1. Bellows connecting holes  29 A,  29 B,  29 C and  29 D are sized to receive appropriately sized fasteners to permit connection of bellows end  27  which, as shown in FIG. 1, may be attached to an upper support end of arm  50 .  
         [0028]    Referring to FIGS. 4 and 5, susceptor support arm  30  includes channel  31  formed along a length and from an underside of mid-section  24 . As seen in FIG. 4, insulator strip  40  is disposed between grounding conductor  32  and thermocouple lead  33 . FIG. 4 shows susceptor plate  21  is backed by ceramic plate  23  positioned for connection to susceptor support arm  30  at susceptor hub receiver end  22 . Grounding conductor  32  passes through channel  31 , terminating at first end  36  which may be connected to at ground receiving hole  37  formed in susceptor plate  21  at susceptor hub  25 . A second end of grounding conductor  32  is secured to wall  15  of processing chamber  10  by connector  16 , as shown in FIG. 1. Thermocouple lead  33  is routed through channel  31  and terminates at first end  34  in thermocouple receiving hole  35 , also formed in susceptor plate  21  at susceptor hub  25 . Insulator strip  40  is disposed between grounding conductor  32  and thermocouple lead  33 .  
         [0029]    [0029]FIG. 6 is a representative cross-section of susceptor support arm  30  including channel  31 . FIG. 6 shows the relative positioning of thermocouple lead  33 , grounding conductor  32  and insulator strip  40 . Channel cover  36  slideably engages grooves  35 A and  35 B formed on opposing inner walls of susceptor support arm channel  31 .  
         [0030]    [0030]FIGS. 7 through 13 depict additional embodiments of the insulator strip of the present invention. FIGS. 7, 8 and  9  show insulator strip  140  including curved first end  141  and second end  142  including thermocouple lead retainer  143 . Linear detent  144 , shown in FIGS. 7 and 9, extends from first end  141  towards second end  142 . As seen in FIG. 4, insulator strip  40  is disposed between grounding conductor  32  and thermocouple lead  33  passes along an upper surface of insulator strip  40  following generally the contour of the upper surface of insulator strip  40  from curved first end  41  to second end  42  and linear detent  144 , shown in FIGS. 7 and 9, before passing on to thermocouple lead retainer  43 , shown in FIG. 4.  
         [0031]    [0031]FIGS. 10 and 11 show an alternate embodiment of insulator strip  240  including first end  241  and second end  242  including thermocouple lead retainer  243 . Linear detent  244 , shown in FIGS.  11 , extends from first end  241  towards second end  242 .  
         [0032]    [0032]FIGS. 12 and 13 show an additional alternate embodiment of insulator strip  340  including first end  341  and second end  342  including thermocouple lead retainer  343 . Linear detent  344 , shown in FIG. 13, extends from first end  341  towards second end  342 . Thermocouple guide  345  is formed at first end first end  341  for guiding and directing a thermocouple lead, (not shown in FIGS. 10 and 11), towards the susceptor plate.  
         [0033]    While this invention has been described with reference to the detailed embodiments, this is not meant to be construed in a limiting sense. Various modifications to the described embodiments as well as the inclusion or exclusion of additional embodiments will be apparent to persons skilled in the art upon reference to this description. It is therefore contemplated that the appended claims will cover any such modifications or embodiments as fall within the true scope of the invention.