Abstract:
A cooling block for coupling a remote plasma source to a resistor is disclosed. As processed substrates become larger for solar panels, organic light emitting diodes, and flat panel displays, a greater amount of cleaning gas and hence, plasma from a remote plasma source, may be necessary. When large amounts of cleaning gas such as fluorine containing gas is ignited into a plasma, the temperature of the remote plasma source that ignites the plasma may become very hot. The hot plasma may transfer heat to adjacent components and to any components through which the plasma flows. By cooling the block connecting the remote plasma source to the resistor, the plasma may be cooled prior to reaching the resistor and hence, prior to reaching the processing chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional patent application Ser. No. 61/016,204 (APPM/013016L), filed Dec. 21, 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 a cooling block for coupling a remote plasma source to a resistor. 
         [0004]    2. Description of the Related Art 
         [0005]    During a plasma deposition process, material deposits not only on the substrate, but also chamber components that are exposed to the plasma. The deposition onto locations other than the substrate is not ideal because over time, flaking may occur. Flaking occurs when material that has been deposited onto chamber surfaces breaks off. The flaking may occur due to expansion and contraction of the material due to temperature fluxuations during processing. The flaking may also occur due to rapid changes in pressure that may occur when a slit valve door is opened to access the processing chamber. When material flakes off, it may fall onto the substrate and contaminate the substrate. 
         [0006]    To avoid flaking, plasma processing chambers may need to be periodically cleaned to remove deposits. The technician operating the processing chamber may decide to clean the processing chamber after a predetermined number of deposition processes. It would be beneficial to have a method and an apparatus that cleans the processing chamber to avoid undesired flaking. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention generally comprises a cooling block for coupling a remote plasma source to a resistor. In a first embodiment, a cooling block for coupling between a remote plasma source and a resistor comprises an inner body having a cavity extending therethrough, an outer body surrounding the inner body and spaced therefrom, one or more plates extending between and coupled to the inner body and the outer body, the one or more plates occupying less than about 50 percent of the space, and a flange coupled to and extending from the outer body, the flange enclosing a passage extending to the cavity. 
         [0008]    In another embodiment, a cooling block for coupling a remote plasma source to a resistor comprises a rectangular shaped first body having a fluid inlet disposed at a first end and a fluid outlet disposed at the second end, and a rectangular shaped second body enclosed within the first body, the second body having a cylindrical cavity therein, wherein the second body is coupled to the first body such that the entire perimeter of at least a portion of the second body is spaced from the first body. 
         [0009]    In another embodiment, a plasma processing apparatus comprises a processing chamber having a backing plate, an inlet block coupled to the backing plate, a power source coupled to the inlet block, a resistor coupled to the inlet block, a cooling block coupled to the resistor, the cooling block having a body with a flange extending therefrom, an inside portion having a passage therethrough for plasma to flow therein, an outside portion coupled to the inside portion with one or more plates such that greater than about 50 percent of an outside surface of the inside portion is spaced from the outside portion, a fluid source coupled to the cooling block, and a remote plasma source coupled to the flange of the cooling block. 
         [0010]    In another embodiment, a plasma processing method comprising igniting a plasma in a remote plasma source, flowing the plasma from the remote plasma source through a cooling block, a resistor, an inlet block, and into a plasma processing chamber, flowing a cooling fluid through the cooling block, wherein the plasma flows through a body disposed within the cooling block, and wherein the cooling fluid flows along the entire perimeter of the outside of the body for at least a portion of the length of the body, processing a substrate in a plasma environment. 
     
    
     
       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 schematic cross sectional view of a plasma enhanced chemical vapor deposition apparatus according to one embodiment of the invention. 
           [0013]      FIG. 2  is a schematic isometric view of a cooling block according to one embodiment of the invention. 
           [0014]      FIG. 3  is a schematic cross sectional isometric view of a cooling block according to another embodiment of the invention. 
           [0015]      FIG. 4A  is a schematic top view of a cooling block according to one embodiment of the invention. 
           [0016]      FIG. 4B  is a schematic bottom cross sectional view of the cooling block of  FIG. 4A . 
       
    
    
       [0017]    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 and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
       DETAILED DESCRIPTION 
       [0018]    The present invention generally comprises a cooling block for coupling a remote plasma source to a resistor in a plasma enhanced chemical vapor deposition (PEDVD) apparatus.  FIG. 1  is a schematic 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  120 . One suitable PECVD apparatus which may be used is available from 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. 
         [0019]    The chamber  100  generally includes walls  102 , a bottom  104 , a showerhead  106 , and susceptor  118  which define a process volume. The process volume is accessed through a slit valve opening  108  such that the substrate  120  may be transferred in and out of the chamber  100 . The susceptor  118  may be coupled to an actuator  116  to raise and lower the susceptor  118 . Lift pins  122  are moveably disposed through the susceptor  118  to support a substrate  120  prior to placement onto the susceptor  118  and after removal from the susceptor  118 . The susceptor  118  may also include heating and/or cooling elements  124  to maintain the susceptor  118  at a desired temperature. The susceptor  118  may also include grounding straps  126  to provide RF grounding at the periphery of the susceptor  118 . 
         [0020]    The showerhead  106  may be coupled to the backing plate  112  by one or more coupling supports to help prevent sag and/or control the straightness/curvature of the showerhead  106 . Additionally and/or alternatively, a center coupling mechanism may be present to couple the backing plate  112  to the showerhead  106 . The center coupling mechanism may surround a backing plate support ring (not shown) and be suspended from a bridge assembly (not shown). The showerhead  106  may additionally be coupled to the backing plate  112  by a bracket  134 . The bracket  134  may have a ledge  136  upon which the showerhead  106  may rest. The backing plate  112  may rest on a ledge  114  coupled with the chamber walls  102  to seal the chamber  100 . 
         [0021]    A gas source  132  is coupled to the backing plate  112  to provide both processing gas and cleaning gas through gas passages in the showerhead  106  to the substrate  120 . The processing gases travel through a remote plasma source  130 . A microwave current from a microwave source (not shown) coupled to the remote plasma source  130  may ignite the plasma. The cleaning gas may be further excited by the RF power source  150  provided to the showerhead  106 . Suitable cleaning gases include by are not limited to NF 3 , F 2 , and SF 6 . The cleaning gas may be ignited into a plasma within the remote plasma source  130 . The plasma may then flow from the remote plasma source  130  to a resistor (or RF choke)  138 . The remote plasma source  130  may be coupled to the resistor by a cooling block  140 . 
         [0022]    At high flow rates, fluorine plasmas may reach very high temperatures. In one embodiment, the fluorine containing plasma may flow from the remote plasma source  130  at a rate between about 25 slm to about 35 slm. When the plasma is very hot, the remote plasma source  130  is heated as are any components through which the plasma may flow. The high temperatures may be undesirable as they could lead to expansion and contraction and/or damage of chamber components. The remote plasma source  130  and the plasma flowing therefrom may be cooled by the cooling block  140 . A cooling fluid may be introduced to the cooling bloc from a cooling fluid source  142  via conduit  144 . The cooling fluid may enter at the top of the cooling block  140  and exit at the bottom of the cooling block  140 . The cooling fluid may then return to the cooling fluid source through conduit  146 . 
         [0023]    After the plasma passes through the cooling block  140  and the resistor  138 , the plasma enters an inlet block  148  before entering the processing chamber  100  through the backing plate  112 . A vacuum pump  110  is coupled to the chamber  100  at a location below the susceptor  118  to maintain the process volume  106  at a predetermined pressure. A RF power source  150  is coupled to the backing plate  112  and/or to the showerhead  106  to provide a RF current to the showerhead  106 . The RF current creates an electric field between the showerhead  106  and the susceptor  118  so that a plasma may be generated from the gases between the showerhead  106  and the susceptor  118 . Various frequencies may be used, such as a frequency between about 0.3 MHz and about 200 MHz. In one embodiment, the RF current is provided at a frequency of 13.56 MHz. The spacing between the top surface of the substrate  120  and the showerhead  106  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. 
         [0024]      FIG. 2  is a schematic isometric view of a cooling block  200  according to one embodiment of the invention. The cooling block comprises a flange  202  extending from the body. A sealing flange  204  is coupled to the flange  202  to couple the cooling block to a remote plasma source. A removable panel  206  may be present on a side  210  of the cooling block. The plasma entering the cooling block  200  may flow into the cooling block  200  through the flange  202  and down towards the end  208 . 
         [0025]    When the cooling block  200  is formed from a unitary piece of material, one or more panels  206  may be cut into the sides  210  of the cooling block  200 . The panels  206  permit portions inside the cooling block  200  to be hollowed out. Once sufficient material has been removed from the inside of the cooling block  200 , the panel  206  may be re-coupled to the cooling block  210 . The panel  206  may be coupled by welding or any other conventional fastening mechanism known in the art. 
         [0026]      FIG. 3  is a schematic cross sectional isometric view of a cooling block  300  according to another embodiment of the invention. The cooling block  300  comprises a top end  302  and a plurality of sides  304 . One or more panels  306  may be carved into one or more sides  304 . The panels  306  may be cut out of the cooling block  300  to permit a space  308  to be carved between the inner body  318  and the outer body  320 . In one embodiment, the inner body  318  and the outer body  320  comprise a unitary body. In another embodiment, the inner body  318  and the outer body  320  comprise separate entities coupled together. The inner body  318  may have a rectangular shape and the outer body  320  may have a rectangular shape. 
         [0027]    A cavity  310  may be formed into the inner body  318 . The cavity may have an open portion at the top end  302  to permit metrology through an optically transparent window (not shown) that may be coupled to the top side  302 . The plasma may enter the cooling block  300  through a passage  316  within a flange  314  disposed adjacent the top side  302 . The plasma may enter the cooling block  300  through the passage  316 , flow perpendicular thereto and exit through a second passage  312  disposed near an end opposite to the top end  302 . Cooling fluid may be continually provided within the space  308  between the inner body  318  and the outer body  320 . The cooling fluid may for perpendicular to the direction of the plasma flowing through the passages  312 ,  316  and parallel to the plasma within the cavity  310 . In one embodiment, the cooling fluid flows counter to the direction of flow of the plasma through the cavity  310 . In another embodiment, the cooling fluid flows in the same direction as the plasma flowing through the cavity  310 . The space  308  permits a greater surface area of the inner body  318  to be exposed to the cooling fluid as opposed to gun drilled cooling channels. In one embodiment, an entire perimeter of the inner body, for at least a portion of the body, is exposed to the cooling fluid. In another embodiment, greater than about 50 percent of the outside surface of the inner body  318  is exposed to the cooling fluid. In another embodiment, the greater than 75 percent is exposed. 
         [0028]    It is to be understood that while the cooling block has been shown as a rectangle shaped structure, other structures are contemplated including round or non-uniform shaped structures. 
         [0029]      FIG. 4A  is a schematic top view of a cooling block  400  according to one embodiment of the invention.  FIG. 4B  is a schematic bottom cross sectional view of the cooling block  400  of  FIG. 4A . The cooling block  400  comprises a top end  402  having an optically transparent metrology window  404  coupled to the top end  402 . One or more flanges  406  extend from the metrology window  404  to permit one or more fastening mechanisms  408  to couple the metrology window  404  to the top end  402 . A cooling fluid inlet  410  may also be disposed on the top end  402 . The outer body  412  of the cooling block  400  may be spaced from the inner body  414 . The cavity  418  of the inner body  414  is shown. In one embodiment, the cavity  418  may comprise a circular or cylindrical shape while the inner body comprises a rectangular shape. The outer body  412  may be coupled to the inner body  414  by a plate  416 . In one embodiment, the plate  416 , outer body  412 , and inner body  414  may comprise a unitary piece of material. In another embodiment, the flange  416 , inner body  414 , and outer body  412  may comprise separate pieces coupled together. 
         [0030]    By coupling a cooling block between a remote plasma source and a resistor (or RF choke), the temperature of the plasma may be reduced and/or controlled. Additionally, the remote plasma source may be cooled. By maintaining a temperature control over the plasma and the remote plasma source, expansion and contraction of the apparatus components may be controlled and apparatus component damage may be reduced. 
         [0031]    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.