Patent Publication Number: US-9404174-B2

Title: Pinned target design for RF capacitive coupled plasma

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of co-pending U.S. patent application Ser. No. 13/327,689, filed Dec. 15, 2011, which is herein incorporated by reference. 
    
    
     FIELD 
     Embodiments of the present invention generally relate to physical vapor deposition processing equipment. 
     BACKGROUND 
     In a physical vapor deposition (PVD) chamber, a dark space region exists between a powered electrode, such as the sputtering target, and a grounded shield disposed proximate the target&#39;s edge, referred to as a dark space shield. In an existing PVD chamber, the dark space shield is typically mounted to the main body of the PVD chamber, separately from the target. The target is typically mounted on a removable lid of the PVD chamber and then lowered onto the chamber body for processing. However, the inventors have discovered that such a configuration may undesirably result in the dark space shield and the target being inaccurately aligned. 
     The inventors have further discovered that as the frequency of radio frequency (RF) energy applied to the target increases, the dark space region becomes more critical to controlling any plasma irregularity and arc events, which may negatively affect the quality of deposition in the PVD chamber. 
     Accordingly, the inventors have provided improved apparatus for PVD processing. 
     SUMMARY 
     Methods and apparatus for physical vapor deposition are provided. In some embodiments, a chamber body; a lid disposed atop the chamber body; a target assembly coupled to the lid, the target assembly including a target of material to be deposited on a substrate; an annular dark space shield having an inner wall disposed about an outer edge of the target; a seal ring disposed adjacent to an outer edge of the dark space shield; and a support member coupled to the lid proximate an outer end of the support member and extending radially inward such that the support member supports the seal ring and the annular dark space shield, wherein the support member provides sufficient compression when coupled to the lid such that a seal is formed between the support member and the seal ring and the seal ring and the target assembly. 
     In some embodiments, an apparatus for physical vapor deposition may include a lid configured to be movable coupled to a substrate process chamber; a target assembly coupled to the lid, the target assembly including a target of material to be deposited on a substrate; an annular dark space shield having an inner wall disposed about an outer edge of the target; a support member coupled to the lid proximate an outer end of the support member and extending radially inward, the support member including a feature that, when the support member is coupled to the lid, biases the annular dark space shield against the target assembly; and a seal ring disposed adjacent to an outer edge of the dark space shield and between the support member and the target assembly, wherein the support member provides sufficient compression when coupled to the lid such that a seal is formed between the support member and the seal ring and the seal ring and the target assembly. 
     Other and further embodiments of the present invention are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the invention depicted 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  depicts a schematic cross sectional view of a process chamber in accordance with some embodiments of the present invention. 
         FIG. 2  depicts a sectional view of a support member and surrounding structure in accordance with some embodiments of the present invention. 
         FIG. 3  depicts a sectional view of a support member and surrounding structure in accordance with some embodiments of the present invention. 
         FIG. 4  depicts a sectional top view of a support member in accordance with some embodiments of the present invention. 
         FIG. 5  depicts an isometric view of a target assembly in accordance with some embodiments of the present invention. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Methods and apparatus for improved physical vapor deposition processing equipment are provided herein.  FIG. 1  depicts a schematic, cross-sectional view of a physical vapor deposition chamber, or process chamber  100  in accordance with some embodiments of the present invention. Examples of suitable PVD chambers include the ENDURA® PVD processing chamber, commercially available from Applied Materials, Inc., of Santa Clara, Calif. Other processing chambers from Applied Materials, Inc. or other manufactures may also benefit from the inventive apparatus disclosed herein. 
     In some embodiments, the process chamber  100  has a chamber lid  134  disposed atop a chamber body  136 . The chamber lid  134  can be removed from the chamber body  136 , for example, to install or replace a target or for performing maintenance on the process chamber  100 . In some embodiments, the chamber lid includes a target assembly  138 , a dark space shield  178 , a seal ring  182 , and a support member  184  for supporting the dark space shield  178  and seal ring  182 . In some embodiments, a feed structure  110  may be coupled to the chamber lid  134  to couple RF and, optionally, DC power to the target. 
     In some embodiments, the target assembly  138  comprises a target  106  and a target backing plate  146 . The target  106  comprises a material to be deposited on the substrate  104  during sputtering, such as a metal or metal oxide. In some embodiments, the backing plate  146  may comprise a conductive material, such as copper-zinc, copper-chrome, or the same material as the target, such that RF and DC power can be coupled to the target  106  via the backing plate  146 . Alternatively, the backing plate  146  may be non-conductive and may include conductive elements (not shown) such as electrical feedthroughs or the like. 
     The support member  184  may be coupled to the chamber lid  134  to support one or more components of the chamber, such as the seal ring  182  and the dark space shield  178 . The support member  184  may be a generally planar member having a central opening to accommodate the dark space shield  178  and the target  106 . In some embodiments, the support member  184  may be circular, or disc-like in shape, although the shape may vary depending upon the corresponding shape of the chamber lid and/or the shape of the substrate to be processed in the process chamber  100 . In use, when the chamber lid  134  is opened or closed, the support member  184  maintains the dark space shield  178  in proper alignment with respect to the target  106 , thereby minimizing the risk of misalignment due to chamber assembly or opening and closing the chamber lid  134 . 
     In some embodiments, the support member  184  may be coupled to the chamber lid  134  proximate an outer peripheral edge of the support member  184  and extends radially inward to support the seal ring  182  and the dark space shield  178 . The seal ring  182  may be a ring or other annular shape having a desired cross-section. The seal ring may include two opposing planar and generally parallel surfaces to facilitate interfacing with the support member  184  on one side of the seal ring  182  and the target backing plate  146  on the other side of the seal ring  182 . The seal ring  182  may be made of a dielectric material, such as ceramic. 
     The dark space shield  178  is generally disposed about an outer edge of the target  106 . In some embodiments, the seal ring  182  is disposed adjacent to an outer edge of the dark space shield  178  (i.e., radially outward of the dark space shield  178 ). In some embodiments, the dark space shield  178  is made of a dielectric material, such as ceramic. By providing a dielectric dark space shield  178 , arcing between the dark space shield and adjacent components that are RF hot may be avoided or minimized. Alternatively, in some embodiments, the dark space shield  178  is made of a conductive material, such as stainless steel, aluminum, or the like. By providing a conductive dark space shield  178  a more uniform electric field may be maintained within the process chamber  100 , thereby promoting more uniform processing of substrates therein. In some embodiments, a lower portion of the dark space shield  178  may be made of a conductive material and an upper portion of the dark space shield  178  may be made of a dielectric material. 
       FIG. 2  depicts a more detailed view of the support member  184  and surrounding structure of the process chamber  100  of  FIG. 1 . In some embodiments, the support member  184  is coupled to the chamber lid  134  proximate an outer periphery of the support member  184 . In some embodiments, the support member  184  is coupled to the chamber lid  134  by a plurality of fasteners  202  such as bolts, or the like. For example,  FIG. 4  depicts a top view of the support member  184  having a plurality of openings  402  distributed about the outer periphery to facilitate the bolts  202  shown in  FIG. 2 . Although eight openings  402  are shown, greater or fewer fasteners may be used depending upon the configuration of the chamber lid and the support member. 
     When coupled to the chamber lid  134 , the support member  184  facilitates forming a seal between portions of the process chamber  100  that are not held at vacuum (such as within the lid) and portions of the process chamber  100  that may be held at vacuum (such as within the interior of the process chamber  100 ). For example, a seal  204  may be disposed between the seal ring  182  and the target backing plate  146 , and a seal  206  may be disposed between the seal ring  182  and the support member  184  such that, when the support member  184  is installed, sufficient force is applied to compress the seals  204 ,  206  to form a vacuum seal at those locations. Seals  204 ,  206 , as well as other seals discussed herein, may be any suitable seal, such as an o-ring, a gasket, or the like. For example, a seal  220  may be provided between the support member  184  and the upper chamber adapter  142  to provide a seal between the chamber lid  134  and the upper chamber adapter  142  when the chamber lid  134  is in a closed position atop the upper chamber adapter  142 . 
     In some embodiments, alignment features may be provided to maintain a gap  208  between the inner wall of the dark space shield  178  and the outer edge of the target  106 . The alignment features may facilitate maintaining a more uniform gap and may prevent contact or near contact of the dark space shield  178  and the target  106  that may undesirably lead to arcing. In some embodiments, the radial gap is in the range of 0.003 to 0.030 inches. In some embodiments, a plurality of inner pins  210  may extend from a bottom surface of the target backing plate  146 . For example, the pins may be press fit or otherwise secured with corresponding holes  260  formed in the target backing plate  146 . The inner pins  210  include portions that extend in a substantially normal direction from the bottom surface of the target backing plate  146  to interface with, or fit into, a corresponding plurality of slots  212  disposed within a top surface of the dark space shield  178 . In some embodiments, there are at least three sets of alignment features (e.g., three inner pins  210  and three slots  212 ) that prevent the side-to-side movement of the dark space shield  178  and the maintain the gap  208  between the inner wall of the dark space shield  178  and the outer edge of the target  106 . The slots  212  may be radially aligned such that a radial length of the slot  212  is greater than the diameter of the inner pins  210  to facilitate relative movement of the dark space shield  178  and the target backing plate  146  due to differences in rates of thermal expansion and contraction, while maintaining alignment between the dark space shield  178  and the target backing plate  146 . In some embodiments, each inner pin  210  may have a hollow passageway  224  disposed axially through the inner pin  210  to allow evacuation of gases trapped within the alignment features. 
     In some embodiments, a plurality of outer pins  250  may be disposed radially outward from the plurality of inner pins  210  near the periphery of the target back plate  146 , and extend from a bottom surface of the target backing plate  146 . For example, the pins  250  may be press fit or otherwise secured with corresponding holes  262  formed in the target backing plate  146 . The outer pins  250  include portions that extend in a substantially normal direction from the bottom surface of the target backing plate  146  to interface with, or fit into, a corresponding plurality of slots  252  disposed within a top surface of the seal ring spacer  182 . In some embodiments, these additional alignment features (e.g., three outer pins  250  and three slots  252 ) further prevent the side-to-side movement of the dark space shield  178  and the maintain the gap  208  between the inner wall of the dark space shield  178  and the outer edge of the target  106  in conjunction with the three inner pins  210  and three slots  212 . The slots  252  may be radially aligned such that a radial length of the slot  252  is greater than the diameter of the outer pins  250  to facilitate relative movement of the dark space shield  178  and the target backing plate  146  due to differences in rates of thermal expansion and contraction, while maintaining alignment between the dark space shield  178  and the target backing plate  146 . In some embodiments, each outer pin  250  may have a hollow passageway  254  disposed axially through the outer pin  250  to allow evacuation of gases trapped within the alignment features. 
     In some embodiments, the inner and outer pins  210 ,  250  may be secured in holes  260 ,  262  such that a top portion of the pins  210 ,  250  extend outward from about 0.05 inches to about 0.5 inches from a bottom surface of backing plate  146 . In some embodiments, the inner and outer pins  210 ,  250  have a total height from about 0.1 inches to about 0.5 inches. In some embodiments, the inner and outer pins  210 ,  250  may be cylindrical and have a diameter from about 0.1 inches to about 0.5 inches. 
       FIG. 5  is an isometric view of target assembly  138  in accordance with at least one embodiment of present invention. As shown in  FIG. 5 , in some embodiments inner pins  210  and outer pins  250  may be disposed equidistantly from each other. 
     In embodiments where the dark space shield  178  is a dielectric, the support member  184  may include a plurality of biasing features that bias the dark space shield  178  against the target assembly  138 . For example, as depicted in  FIG. 3 , a biasing feature  302  may include a ball  304  retained in a recess in the support member  184 . A spring  306  may be disposed between the ball  304  and a bottom of the recess to bias the ball  304  away from the bottom of the recess. A retaining feature, such as a retaining ring  308  may be secured to the support member  184  to retain the ball  304  within the recess. The diameter of the retaining ring  308  may be selected to allow a desired portion of the ball  304  to extend from the recess and contact the dark space shield  178  while retaining the ball  304  within the recess of the support member  184 . Furthermore, by allowing radial movement by moving over the balls  304 , particle generation due to rubbing between components may be reduced or eliminated. 
     Returning to  FIG. 1 , in some embodiments, the feed structure  110  couples RF and, optionally, DC energy to the target  106 . Although a particular feed structure  110  is described below, other feed structures having other configurations may also be utilized. In some embodiments, the feed structure  110  may include a body  112  having a first end  114  that can be coupled to an RF power source  118  and, optionally, a DC power source  120 , which can be respectively utilized to provide RF and DC energy to the target  106 . A second end  116  of the feed structure  110 , opposite the first end  114 , is coupled to the chamber lid  134 . In some embodiments, the body  112  further includes a central opening  115  disposed through the body  112  from the first end  114  to the second end  116 . The feed structure  110  may be fabricated from suitable conductive materials to conduct the RF and DC energy from the RF power source  118  and the DC power source  120 . 
     In some embodiments, the chamber lid  134  may further include a source distribution plate  122  to distribute the energy applied via the feed structure  110  to the peripheral edge of the target  106  via a conductive member  125 . As such, in some embodiments, the second end  116  of the body  112  may be coupled to the source distribution plate  122 . The source distribution plate includes a hole  124  disposed through the source distribution plate  122  and aligned with the central opening  115  of the body  112 . The source distribution plate  122  may be fabricated from suitable conductive materials to conduct the RF and DC energy from the feed structure  110 . 
     The conductive member  125  may be a tubular member having a first end  126  coupled to a target-facing surface  128  of the source distribution plate  122  proximate the peripheral edge of the source distribution plate  122 . The conductive member  125  further includes a second end  130  coupled to a source distribution plate-facing surface  132  of the target  106  (or to the backing plate  146  of the target  106 ) proximate the peripheral edge of the target  106 . 
     A ground shield  140  may be provided to cover the outside surfaces of the chamber lid  134 . The ground shield  140  may be coupled to ground, for example, via the ground connection of the chamber body  136 . In some embodiments, the ground shield  140  may have a central opening to allow the feed structure  110  to pass through the ground shield  140  to be coupled to the source distribution plate  122 . The ground shield  140  may comprise any suitable conductive material, such as aluminum, copper, or the like. An insulative gap  139  is provided between the ground shield  140  and the outer surfaces of the distribution plate  122 , the conductive member  125 , and the target  106  (and/or backing plate  146 ) to prevent the RF and DC energy from being routed directly to ground. The insulative gap may be filled with air or some other suitable dielectric material, such as a ceramic, a plastic, or the like. 
     The chamber body  136  contains a substrate support pedestal  102  for receiving a substrate  104  thereon. The substrate support pedestal  102  may be located within a grounded enclosure wall  108 , which may be a chamber wall (as shown) or a grounded shield. The ground shield  140  may covering at least some portions of the chamber  100  above the target  106 . 
     In some embodiments, the chamber body  134  may further include a grounded bottom shield  180  connected to a ledge  176  of an upper chamber adapter  142 . The bottom shield  180  extends downwardly and may include a generally tubular portion having a generally constant diameter. The bottom shield  180  extends along the walls of the upper chamber adapter  142  and the chamber wall  108  downwardly to below a top surface of the substrate support pedestal  102  and returns upwardly until reaching a top surface of the substrate support pedestal  102 . A cover ring  186  rests on the top of the upwardly extending inner portion  188  of the bottom shield  180  when the substrate support pedestal  102  is in its lower, loading position but rests on the outer periphery of the substrate support pedestal  102  when it is in its upper, deposition position to protect the substrate support pedestal  102  from sputter deposition. 
     The bottom shield  180  may have an inner diameter, or central opening, that is substantially the same as an inner diameter, or corresponding central opening, of the dark space shield  178 , thereby providing a more uniform processing window for the plasma formed in the process chamber  100 . In some embodiments, a plurality of alignment features may be provided to maintain the bottom shield  180  in a desired position. For example, as shown in  FIG. 2 , in some embodiments, a plurality of pins  214  may extend from a surface of the upper chamber adapter  142 . For example, the pins may be press fit or otherwise secured with corresponding holes formed in the upper chamber adapter  142 . The pins  214  include portions that extend in a substantially normal direction from the surface of the upper chamber adapter  142  to interface with, or fit into, a corresponding plurality of slots  216  disposed within the bottom shield  180 . In some embodiments, there are at least three sets of alignment features (e.g., three pins  214  and three slots  216 ) that prevent the side-to-side movement of the bottom shield  180  and the maintain the alignment of the bottom shield  180  and the dark space shield  178 . The slots  216  may be radially aligned such that a radial length of the slot  216  is greater than the diameter of the pins  214  to facilitate relative movement of the bottom shield  180  and the upper chamber adapter  142  due to differences in rates of thermal expansion and contraction, while maintaining alignment between the bottom shield  180  and the dark space shield  178 . In some embodiments, a passageway  218  may be provided through the upper chamber adapter to prevent trapping of gases when installing the pins  214 . In some embodiments, one or more fasteners may be provided to secure the bottom shield  180  to the upper chamber adapter  142 . For example, as shown in  FIG. 3 , a fastener, such as a bolt  310  may be provided through a corresponding hole disposed in the upper chamber adapter  142 . In some embodiments, a ring  312  may be disposed in a recess in the upper chamber adapter  142  in line with the bolts  310 . The bolts  310  may be threaded into the ring  312  to clamp the bottom shield  180  to the upper chamber adapter  142 . 
     Thus, apparatus for enabling concentricity of plasma dark space are provided herein. The inventive apparatus advantageously allows for improved gap control between the dark space shield and the target and for improved concentricity of the plasma dark space region. 
     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.