Abstract:
A baffle assembly for an etching apparatus is disclosed. The baffle assembly comprises a ring and a lower baffle portion having a curved wall extending between a flange portion and a lower frame portion. A heating assembly may be present within the lower frame portion to control the temperature of the baffle. The baffle assembly may help confine the plasma within the processing space in the chamber. The ring may comprise silicon carbide and the lower baffle portion may comprise aluminum.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional patent application Ser. No. 60/914,583 (APPM/012092L), filed Apr. 27, 2008, 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 baffle assembly for confining a plasma in an etching chamber. 
         [0004]    2. Description of the Related Art 
         [0005]    Plasma processing of semiconductor substrates in the manufacture of microelectronic integrated circuits is used in dielectric etching, metal etching, chemical vapor deposition (CVD) and other processes. In semiconductor substrate processing, the trend towards increasingly smaller feature sizes and line-widths has placed a premium on the ability to mask, etch, and deposit material on a semiconductor substrate, with greater precision. 
         [0006]    Etching may be accomplished by applying radio frequency (RF) power to a working gas supplied to a processing region over a substrate supported by a support member. The resulting electric field creates a reaction zone in the processing region that excites the working gas into a plasma. The support member may be biased to attract ions within the plasma towards the substrate supported thereon. Ions migrate towards a boundary layer of the plasma adjacent to the substrate and accelerate upon leaving the boundary layer. The accelerated ions produce the energy required to remove, or etch, the material from the surface of the substrate. As the accelerated ions can etch other components within the processing chamber, confining the plasma to the processing region above the substrate may be beneficial. 
         [0007]    Unconfined plasmas may cause etch-byproduct (typically polymer) deposition on the chamber walls and could also etch the chamber walls. Etch-byproduct deposition on the chamber walls could cause the process to drift. The etched materials from the chamber walls could contaminate the substrate by re-deposition and/or could create particles for the chamber. In addition, unconfined plasmas could also cause etch-byproduct deposition in the downstream areas. The accumulated etch-byproduct may flake off and result in particles. 
         [0008]    Therefore, there is a need in the art for an improved baffle assembly for confining plasma within a processing region inside the plasma chamber. 
       SUMMARY OF THE INVENTION 
       [0009]    A baffle assembly for an etching apparatus is disclosed. The baffle assembly includes a ring and a lower baffle portion having a curved wall extending between a flange portion and a lower frame portion. A heating assembly may be present within the lower frame portion to control the temperature of the baffle. The baffle assembly may help confine the plasma within the processing space in the chamber. The ring may comprise silicon carbide and the lower baffle portion may comprise aluminum. 
         [0010]    In one embodiment, baffle assembly is disclosed. The baffle assembly may include a ring and a base portion coupled to the ring. The base portion comprises a flange having a first diameter, a lower frame portion having a second diameter less than the first diameter, and a first wall coupled between the flange and the lower frame portion. The first wall curves out from the lower frame portion to the flange. 
         [0011]    In another embodiment, a ring for use in a baffle assembly of an etching chamber is disclosed. The ring may include a top wall extending to a first diameter, an outer wall having a second diameter greater than the first diameter, and a second wall coupled between the top wall and the outer wall. The second wall curves from the top wall at the first diameter to the outer wall at the second diameter. 
         [0012]    In another embodiment, a base portion of a baffle is disclosed. The base portion may include a flange having a first diameter, a lower frame portion having a second diameter less than the first diameter, and a first wall coupled between the flange and the lower frame portion. The first wall curves out from the lower frame portion to the flange. 
         [0013]    In another embodiment, a baffle assembly is disclosed. The baffle assembly may include a ring and a base portion coupled to the ring. The base portion comprises a flange having a first diameter, a lower frame portion having a second diameter less than the first diameter, a supporting portion for supporting the flange, and a heating assembly. 
         [0014]    In another embodiment, a base portion of a baffle is disclosed. The base portion may include a flange having a first diameter, a lower frame portion having a second diameter less than the first diameter, a supporting portion for supporting the flange, and a heating assembly. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    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. 
           [0016]      FIG. 1  is a schematic view of a plasma processing chamber according to one embodiment of the invention. 
           [0017]      FIG. 2A  is a cross sectional view of a baffle assembly according to one embodiment of the invention. 
           [0018]      FIG. 2B  is a cross sectional view of cut out A from  FIG. 2A . 
           [0019]      FIG. 2C  is a cross sectional view of cut out B from  FIG. 2B . 
           [0020]      FIG. 3A  is a top view of a ring according to one embodiment of the invention. 
           [0021]      FIG. 3B  is a cross sectional view of a ring of  FIG. 3A . 
           [0022]      FIGS. 4A and 4B  are schematic perspective views of a lower baffle portion according to one embodiment of the invention. 
           [0023]      FIG. 4C  is a cross sectional view of cut out C from  FIG. 4A . 
           [0024]      FIG. 4D  is a cross sectional view of  FIG. 4C . 
           [0025]      FIG. 5  shows a baffle assembly according to another embodiment of the invention. 
       
    
    
       [0026]    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 
       [0027]    The present invention comprises a baffle assembly for confining a plasma to a processing region in a plasma processing apparatus. While the invention will be described below in relation to an ENABLER® etching system available from Applied Materials, Inc., Santa Clara, Calif., it is to be understood that the invention may be used in other processing chambers including physical vapor deposition (PVD) chambers, CVD chambers, etc., including those chambers sold by other manufacturers. 
         [0028]      FIG. 1  illustrates an example of a plasma reactor, such as the ENABLER® etching system manufactured by Applied Materials, Inc., of Santa Clara, Calif., that includes a reactor chamber  100 , which may include liners to protect the walls, with a substrate support (or pedestal)  105  at the bottom of the chamber  100  supporting a semiconductor substrate. The chamber  100  is bounded at the top by a disc shaped overhead aluminum electrode  125  supported at a predetermined gap length above the substrate on grounded chamber body  127  by a dielectric (quartz) seal  130 . A power generator  150  applies very high frequency (VHF) power to the electrode  125 . VHF is typically between about 30 MHz to about 300 MHz and is one of the RF bands, which range from about 10 kHz to about 10 GHz. In one embodiment, the VHF source power frequency is 162 MHz for a 300 mm substrate diameter. VHF power from the generator  150  is coupled through a coaxial cable  162  matched to the generator  150  and into a coaxial stub  135  connected to the electrode  125 . The stub  135  has a characteristic impedance, resonance frequency, and provides an impedance match between the electrode  125  and coaxial cable  162  or the VHF power generator  150 . The chamber body is connected to the VHF return (VHF ground) of the VHF generator  150 . Bias power is applied to the substrate by a bias power RF signal generator  102  coupled through a conventional impedance match circuit  104  to the substrate support  105 . The power level of the bias generator  102  controls the ion energy near the substrate surface. The bias power (typically at 13.56 MHz) is typically used to control ion energy, while the VHF source power is applied to the overhead electrode to govern plasma density. A vacuum pump system  111  evacuates the chamber  100  through a plenum  112 . 
         [0029]    The substrate support  105  includes a metal pedestal layer  106  supporting a lower insulation layer  107 , an electrically conductive mesh layer  108  overlying the lower insulation layer  107  and a thin top insulation layer  110  covering the conductive mesh layer  108 . The semiconductor workpiece or substrate is placed on top of the top insulation layer  110 . The substrate support  105  and the substrate form a cathode during substrate processing. If the substrate is not present, the substrate support  105  is the cathode during plasma processing. The electrically conductive mesh layer  108  and the metal pedestal layer  106  may be formed of materials such as molybdenum and aluminum respectively. The insulation layers  107  and  110  may be formed of materials such as aluminum nitride or alumina. The conductive mesh layer  108  supplies the RF bias voltage to control ion bombardment energy at the surface of the substrate. The conductive mesh  108  also can be used for electrostatically chucking and de-chucking the substrate, and in such a case can be connected to a chucking voltage source in the well-known fashion. The conductive mesh  108  therefore is not necessarily grounded and can have, alternately, a floating electric potential or a fixed D.C. potential in accordance with conventional chucking and de-chucking operations. The substrate support  105 , in particular the metal pedestal layer  106 , typically (but not necessarily) is connected to ground, and forms part of a return path for VHF power radiated by the overhead electrode  125 . 
         [0030]    In order to improve the uniformity of impedance across the substrate support, a dielectric cylindrical sleeve  113  is designed to surround the RF conductor  114 . The axial length and the dielectric constant of the material constituting the sleeve  113  determine the feed point impedance presented by the RF conductor  114  to the VHF power. By adjusting the axial length and the dielectric constant of the material constituting the sleeve  113 , a more uniform radial distribution of impedance can be attained, for more uniform capacitive coupling of VHF source power. 
         [0031]    A terminating conductor  165  at the far end  135   a  of the stub  135  shorts the inner and outer conductors  140 ,  145  together, so that the stub  135  is shorted at its far end  135   a . At the near end  135   b  (the unshorted end) of the stub  135 , the outer conductor  145  is connected to the chamber body via an annular conductive housing or support  175 , while the inner conductor  140  is connected to the center of electrode  125  via a conductive cylinder  176 . A dielectric ring  180  is held between and separates the conductive cylinder  176  and the electrode  125 . 
         [0032]    The inner conductor  140  can provide a conduit for utilities such as process gases and coolant. The principal advantage of this feature is that, unlike typical plasma reactors, the gas line  170  and the coolant line  173  do not cross large electrical potential differences. They therefore may be constructed of metal, a less expensive and more reliable material for such a purpose. The metallic gas line  170  feeds gas inlets  172  in or adjacent the overhead electrode  125  while the metallic coolant line  173  feeds coolant passages or jackets  174  within the overhead electrode  125 . 
         [0033]    Since plasma density is relatively low near the wall, a baffle assembly  131  placed around the substrate with a distance (or gap) from the inner chamber wall  128  may confine the plasma. The distance (or gap) between the edge of the baffle assembly  131  and the inner chamber wall  128  cannot be too large. If the gap distance is larger than the plasma sheath thickness near the chamber wall, it could increase the amount of plasma being drawn away from the reaction zone above the substrate and toward the chamber wall and downstream, which makes the plasma less confined. The distance (or gap) between the edge of the baffle assembly  131  and the inner chamber wall  128  cannot be too small either, since the flow resistance, which affects the chamber pressure, would increase to an unacceptable level. Therefore, the baffle assembly  131  is placed around the substrate with a suitable distance from the inner chamber wall  128  to provide good plasma confinement and low flow resistance. 
         [0034]      FIG. 2A  is a cross sectional view of a baffle assembly  200  according to one embodiment of the invention. The baffle assembly  200  comprises a ring  202  and a base portion  204 . The base portion  204  also comprises a flange  206  having a first diameter “D” of between about 19 inches and about 20 inches. A curved wall  208  extends from the flange  206  to a heating assembly  214  that is coupled with the base portion  204 . The curved wall  208  provides support for the flange  206  extending from the base portion  204  as well as the ring  202 . The innermost outer wall  220  of the base portion  204  has a diameter “G” of between about 14 inches and about 16 inches. A notch  222  may also be present on the bottom of the base portion  204 . A heating assembly may be present in the baffle assembly  200 . The heating assembly may comprise a heating tube brazed inside the base potion  204 . 
         [0035]      FIG. 2B  is a cross sectional view of cut out A from  FIG. 2A . A ledge  210  may be disposed radially inward of the flange  206 . A curved wall  218  may extend between the outer wall  218  of the flange  206  and a bottom wall  216  of the flange  206 . 
         [0036]      FIG. 2C  is a cross sectional view of cut out B from  FIG. 2B . The ring  202  may be bonded to the base portion  204  with one or more spacers  212  disposed therebetween. One or more O-rings  224  may also be disposed between the base portion  204  and the ring  202  to provide a bonded seal between the ring  202  and the base portion  204 . The O-rings  224  may be disposed within a notch formed in the base portion  204 . 
         [0037]      FIG. 3A  is a top view of a ring  300  according to one embodiment of the invention.  FIG. 3B  is a cross sectional view of the ring  300  of  FIG. 3A . The ring  300  may comprise a top wall  302  having a diameter “E” between about 18 inches and about 19 inches. The ring  300  may also comprise an outer wall  308  having a diameter “F” between about 19 inches and about 20 inches. A curved wall  304  may extend between the outer wall  308  and the top wall  302 . The ring  300  may comprise an opening  306  having a diameter “I” between about 13 inches and about 14 inches. In one embodiment, the diameter of the outer wall  308  of the ring may be substantially equal to the diameter of the flange  206 . 
         [0038]      FIGS. 4A and 4B  are schematic perspective views of a lower baffle portion according to one embodiment of the invention.  FIG. 4A  is a schematic perspective view of the lower baffle portion viewed from the bottom.  FIG. 4B  is a schematic view of the lower baffle portion viewed from the top. As may be seen in  FIG. 4A , the bottom of the lower baffle portion has a female receptacle for providing power to the heating assembly.  FIG. 4C  is a cross sectional view of cut out C from  FIG. 4A  showing the female receptacle  400 . As may be seen from  FIG. 4C , the receptacle comprises three slots  402  for receiving a power plug. 
         [0039]      FIG. 4D  is a cross sectional view of  FIG. 4C .  FIG. 4D  shows a cross sectional view of the female receptacle  400  shown in  FIG. 4C . The lower baffle portion comprises a top portion  404  coupled with a bottom portion  406 . Fastening mechanisms  408  may be used to secure the female receptacle to the bottom portion  406 . In one embodiment, the fastening mechanism  408  is a screw, but it is to be understood that other fastening mechanisms  408  may be utilized. Two electrical contacts  412  are disposed in the receptacle  410  to deliver the electrical power to the heating tubes  414  that are brazed within the lower baffle portion. 
         [0040]      FIG. 5  shows a baffle assembly  500  according to another embodiment of the invention. As may be seen in  FIG. 5 , the baffle assembly  500  comprises a ring  502  coupled with a lower portion  504  having a flange  506  supported by a support structure  508 . In one embodiment, the support structure  508  may comprise a step or corner shape. While a step or corner shape is shown as the support structure  508 , it is to be understood that other shapes may be utilized to provide mechanical strength to support the flange  506 , including curved walls as discussed above. 
         [0041]    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.