Abstract:
Embodiments of lift pin assemblies are provided herein. In some embodiments, a lift pin assembly includes an elongate base formed of a first material and having a first feature formed in a distal end of the base to interface with and removably support a tip; and a tip formed of a second material different than the first material and having a support surface on a first side of the tip and an opposing second side of the tip, wherein the opposing second side includes a second feature to mate with the first feature of the base to removably retain the tip on the distal end of the base.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional patent application Ser. No. 62/006,846, filed Jun. 2, 2014, which is herein incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    Embodiments of the present disclosure generally relate to apparatus for handling a substrate. 
       BACKGROUND 
       [0003]    Lift pins extend through a substrate support to lift a substrate off the substrate support to facilitate placement and removal of the substrate onto the substrate support. Conventionally, lift pins are formed of a metal to improve rigidity. The inventors have observed that impact between the substrate and metal surfaces results in particle generation on the substrate and in the processing chambers. 
         [0004]    In some processes, to maintain process uniformity and ensure optimal performance of a processing chamber, a conditioning operation such as a pasting process is performed, in which a covering is applied over materials deposited on process chamber surfaces to prevent the deposited materials from flaking off the process chamber surfaces and contaminating the substrate during subsequent processes. During the pasting process, a shutter disk may be positioned atop a substrate support disposed in the process chamber to prevent the deposition of any materials upon the substrate support. 
         [0005]    In addition, when a process chamber is opened, a target containing material to be deposited on a substrate may begin to oxidize. As such, a burn-in process may be performed to remove an oxide layer on the target. During the burn-in process, a shutter disk may be positioned atop a substrate support disposed in the process chamber to prevent the deposition of any materials upon the substrate support. 
         [0006]    Although the inventors believe that eliminating hard lift pin surfaces altogether would address the issue of particle generation on a backside of the substrate, the inventors have observed that a hard surface is desirable for contacting the shutter disk, which is heavier and becomes hotter than the substrate. 
         [0007]    Therefore, the inventors have provided an improved lift pin assembly. 
       SUMMARY 
       [0008]    Embodiments an apparatus for handling a substrate are provided herein. In some embodiments, a lift pin assembly includes an elongate base formed of a first material and having a first feature formed in a distal end of the base to interface with and removably support a tip; and a tip formed of a second material different than the first material and having a support surface on a first side of the tip and an opposing second side of the tip, wherein the opposing second side includes a second feature to mate with the first feature of the base to removably retain the tip on the distal end of the base. 
         [0009]    In some embodiments, a lift pin assembly includes a lift pin comprising a first material providing a first support surface and a second material providing a second support surface, wherein the first material is different than the second material, wherein the first material is an electrically conductive polymer, and wherein the second material is metallic. 
         [0010]    In some embodiments, a substrate processing chamber includes a chamber body defining an inner volume; a substrate support disposed in the inner volume, the substrate support including a plurality of channels extending from a lower surface to an upper surface of the substrate support; and a plurality of lift pin assemblies to extend through the plurality of channels to facilitate placement or removal of a substrate or a shutter disk, each of the lift pin assemblies including a lift pin comprising a first material providing a first support surface and a second material providing a second support surface, wherein the first material is different than the second material, wherein the first material is an electrically conductive polymer, and wherein the second material is metallic. 
         [0011]    Other and further embodiments of the present disclosure are described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Embodiments of the present disclosure, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
           [0013]      FIG. 1  depicts a process chamber suitable for use with a lift pin assembly in accordance with some embodiments of the present disclosure. 
           [0014]      FIG. 2  depicts a lift pin assembly in accordance with some embodiments of the present disclosure. 
           [0015]      FIGS. 3A-B  depict a lift pin assembly in accordance with some embodiments of the present disclosure. 
           [0016]      FIGS. 4A-B  depict a lift pin assembly in accordance with some embodiments of the present disclosure. 
           [0017]      FIGS. 5A-B  depict a lift pin assembly in accordance with some embodiments of the present disclosure. 
           [0018]      FIG. 6  depicts a cross sectional view of the lift pin assembly of  FIGS. 5A-B  in accordance with some embodiments of the present disclosure. 
       
    
    
       [0019]    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 
       [0020]    Embodiments of lift pin assemblies are provided herein. Embodiments of the lift pin assembly may advantageously decrease particle generation on a backside of a substrate while maintaining the capability of supporting a shutter disk when present. Embodiments of the inventive lift pin assembly may advantageously be easily retrofitted to existing processing systems, thereby avoiding unnecessary and costly modification of existing processing systems. Although useful for many substrate handling apparatuses, the apparatus disclosed below is illustratively described with respect to a physical vapor deposition (PVD) processing chamber. 
         [0021]      FIG. 1  is a schematic diagram of an exemplary process chamber  100  for use in connection with some embodiments of the present disclosure. In some embodiments, the process chamber  100  may be one of a plurality of chambers combined to form a multi-chamber processing system (e.g., a cluster tool). Alternatively, the process chamber  100  may be a standalone process chamber. In some embodiments, the process chamber  100  may be a deposition chamber, for example, a PVD chamber. Alternatively, the process chamber  100  may be any suitable process chamber in which a shutter disk assembly may be used to protect the substrate support from damage during chamber/target cleaning and or seasoning processes. 
         [0022]    The process chamber  100  includes a chamber body  102  and a lid assembly  104  that defines an evacuable process volume  106 . The chamber body  102  generally includes one or more sidewalls  108  and a bottom  110 . The one or more sidewalls  108  may be a single circular sidewall or multiple sidewalls in process chambers having non-circular configurations. The sidewalls generally contain a shutter disk assembly port  112 . The shutter disk assembly port  112  is configured to allow at least a portion of a shutter disk assembly  140  therethrough when the shutter disk assembly  140  is in a retracted position. A housing  116  generally covers the shutter disk assembly port  112  to maintain the integrity of the vacuum within the process volume  106 . Additional ports may be provided in the sidewalls, such as a sealable access port to provide for the entrance and egress of the substrate  114  from the process chamber  100 . A pumping port may be provided in the sidewalls and/or the bottom of the chamber body  102  and is coupled to a pumping system that evacuates and controls the pressure within the process volume  106 . In other embodiments, a shutter garage (not shown) located outside of process chamber  100  may store the shutter disk assembly  140  and move it into process chamber  100  through an opening (not shown) in process chamber  100 . 
         [0023]    The lid assembly  104  of the chamber body  102  generally supports an annular shield  118  that supports a shadow ring  120 . The shadow ring  120  is generally configured to confine deposition to a portion of the substrate  114  exposed through the center of the shadow ring  120 . The lid assembly  104  generally comprises a target  122  and a magnetron  124 . 
         [0024]    The target  122  provides material that is deposited on the substrate  114  during the deposition process while the magnetron  124  enhances uniform consumption of the target material during processing. The target  122  and substrate support  126  are biased relative each other by a power source  128 . An inert gas, for example, argon, is supplied to the process volume  106  from a gas source  130 . A plasma is formed between the substrate  114  and the target  122  from the gas. Ions within the plasma are accelerated toward the target  122  and cause material to become dislodged from the target  122 . The dislodged target material is attracted towards the substrate  114  and deposits a film of material thereon. 
         [0025]    The substrate support  126  is generally disposed on the bottom  110  of the chamber body  102  and supports the substrate  114  during processing. A lift pin assembly  133  may include a plurality of lift pins  109  mounted on a platform  117  connected to a shaft  111  which is coupled to a second lift mechanism  135  for raising and lowering the lift pin assembly  133  so that the substrate  114  or the shutter disk may be placed on or removed from the substrate support  126 . The substrate support  126  includes channels  121  (e.g., thru-holes) to receive the lift pins  109 . A bellows assembly  131  is coupled between the platform  117  and the bottom  110  to provide a flexible seal which maintains the chamber vacuum during vertical motion of the lift pin assembly  133 . 
         [0026]    A shutter disk assembly mechanism  132  is generally disposed proximate the substrate support  126 . The shutter disk assembly mechanism  132  generally includes a blade  134  that supports the shutter disk assembly  140  and an actuator  136  coupled to the blade  134  by a shaft  138  to control the position of the blade  134 . 
         [0027]    The blade  134  may be moved between the retracted, or cleared, position shown in  FIG. 1  and a second position that places the shutter disk assembly  140  substantially concentric with the substrate support  126 . In the second position, the shutter disk assembly  140  may be transferred (by utilizing the lift pins) to the substrate support  126  during a target burn-in (in PVD chambers) and chamber pasting (in substrate preclean chambers) processes. The blade  134  is returned to the retracted position after the target burn-in and chamber pasting processes. The actuator  136  may be any device that may be adapted to rotate the shaft  138  through an angle that moves the blade  134  between the cleared and second positions. In other embodiments consistent with present disclosure, a robotic mechanism which positions a substrate  114  for processing may also be used to move the shutter disk assembly  140  in position to protect the substrate support  126 . 
         [0028]      FIG. 2  depicts a schematic view of an upper portion of a lift pin  209  in accordance with some embodiments of the present disclosure. The lift pin  209  includes an elongate base  204  with a first feature  206  at a distal end. The first feature  206  interfaces with and retains a tip  202  for supporting a substrate or shutter disk thereon. The tip  202  includes a second feature  208  that is sized and shaped to be held by the first feature  206 . In some embodiments, the first feature  206  may be a collet and the second feature is a tapered surface to be inserted into and engaged by the collet to couple the tip  202  to the elongate base  204 . In other embodiments, the second feature of the tip  202  may be threaded to engage corresponding threads in the first feature  206 . In order to reduce particle generation on a backside of a substrate, the tip  202  is formed of an electrically conductive polymer such as, for example, CELAZOLE®, which can withstand temperatures of up to about 400° C. The elongate base  204  is formed of a metal such as, for example, stainless steel. Such a polymer advantageously prevents particle generation on the backside of a substrate while maintaining the ability to support a hot and heavy shutter disk. 
         [0029]      FIGS. 3A and 3B  depict a schematic view of an upper portion of a lift pin  309  in accordance with some embodiments of the present disclosure. The lift pin  309  includes a pin  302  that extends through a sheath  304 . The pin  302  is formed of a first material and the sheath  304  is formed of a second material different from the first material. In some embodiments, the first material is an electrically conductive polymer and the second material is metallic. The pin  302  provides a first support surface  306  for supporting a substrate thereon. The sheath  304  provides a second support surface  308  for supporting a shutter disk thereon. The pin  302  extends beyond the second support surface  308  so that the first and second support surfaces  306 ,  308  are offset. As depicted in  FIG. 3A , the shutter disk includes a recess, such as an annular groove  310 , to advantageously center the shutter disk on the lift pin assembly  133 . The annular groove  310  is sized and shaped so that, when the shutter disk is placed atop the lift pin assembly, the pin  302  extends into the annular groove  310  and is spaced apart from the shutter disk by a distance D1. In some embodiments, D1 may be at least 0.01 inches. As such, the shutter disk rests on the second support surface  308  of the sheath  304 . As depicted in  FIG. 3B , when a substrate is placed atop the lift pin assembly  133 , the substrate rests on the first support surface  306  of the pin  302 . Because the pin  302  extends beyond the sheath  304 , the substrate never contacts the sheath  304 , thereby avoiding particle generation on a backside of the substrate. In some embodiments, the first support surface  306  may be round shaped to reduce a contact area between the pin  302  and the substrate. 
         [0030]      FIGS. 4A and 4B  depict a schematic view of a lift pin  409  according to some embodiments of the present disclosure. The lift pin  409  includes a pin  402  that extends through a sheath  404 . The pin  402  is formed of a first material and the sheath  404  is formed of a second material. In some embodiments, the first material is an electrically conductive polymer and the second material is metallic. In other embodiments, both the first and second materials are metallic (e.g., stainless steel). The pin  402  includes a collar  406 , beneath which a spring  408  is disposed. The spring  408  extends between the collar  406  and the platform  117 . When a substrate is placed atop the lift pin  409 , the spring  408  is in an uncompressed state. When a shutter disk is placed atop the lift pin  409 , the spring  408  is in a compressed state. The spring  408  is selected so that its spring constant is sufficient to support the weight of a substrate and remain uncompressed. The specific spring constant required may be determined by the respective weights of the substrate and the shutter disk as well as the number of lift pins (e.g., three or more) that support the substrate and shutter disk. When a shutter disk is placed atop the pin  402 , the weight of the shutter disk compresses the spring  408  so that the shutter disk rests on an upper support surface  414  of the sheath  404 . A polymer tip  412  is disposed atop the pin  402 . The polymer tip  412  advantageously prevents particle generation on a backside of the substrate if the pin  402  is metallic. In some embodiments, the polymer tip  412  may be a ball. 
         [0031]      FIGS. 5A and 5B  depict a schematic view of a lift pin  509  according to some embodiments of the present disclosure. The lift pin  509  includes a pin  502  that extends through a sheath  504 . The pin  502  is formed of a first material and the sheath  504  is formed of a second material different from the first material. In some embodiments, the first material is an electrically conductive polymer and the second material is metallic. The lift pin  509  also includes a locking mechanism  506  that moves the pin  502  to a raised ( FIG. 5B ) or lowered ( FIG. 5A ) position. The locking mechanism  506  includes an actuator  508  with a lower portion extending through the platform  117  and a spring  514  that biases the locking mechanism  506  towards the platform  117 . To move the pin  502  to either of the two positions, the lift pin assembly  133  is lowered until the actuator  508  is pressed against the bottom  110  of the process chamber  100  and subsequently lifted off of the bottom  110 . The actuator  508  has a length D 2  that is long enough to contact the bottom  110  of the process chamber  100  when the lift pin assembly  133  is lowered, thereby depressing the actuator  508 . As a result, the pin  502  is pushed upwards and then is lowered into a resting position (raised or lowered position). To move the pin  502  to the other position, the lift pin assembly  133  is lowered again until the actuator  508  is pressed against the bottom  110  of the process chamber  100  and subsequently lifted off of the bottom  110 . When a substrate is to be placed atop the lift pin  509 , the locking mechanism  506  is actuated to move the pin  502  to the raised position so that the substrate rests on a first support surface  510  of the pin  502  ( FIG. 5B ). When a shutter disk is to be placed atop the lift pin  509 , the locking mechanism  506  is actuated to move the pin  502  to the lowered position so that the shutter disk rests on a second support surface  512  of the sheath  504 . 
         [0032]    As illustrated in  FIG. 6 , the locking mechanism  506  includes a first cam  516  at a lower end of the pin that engages with a second cam  518  at an upper end of the actuator  508 . The first cam  516  has a first profile and the second cam  518  has a second profile. An inner surface of the sheath  504  surrounding the first cam  516  includes a plurality of protrusions  520  separated by a plurality of channels. In the resting position (shown in  FIG. 6 ), the first cam  516  rests on the plurality of protrusions  520  or extends into the plurality of channels. When the lift pin assembly  133  is lowered and the actuator  508  is pushed up, the second cam  518  is forced against the first cam  516 , thereby pushing the pin  502  upward. The second profile of the second cam  518  is configured to rotate the first cam  516  (and the pin  502 ) when the second cam  518  engages the first cam  516 . When the lift pin assembly  133  is raised, the spring  514  forces the pin  502  back to its resting position, in which the first cam  516  either rests against the plurality of protrusions  520  or extends into the channels between them. The rotation of the pin  502  facilitates the switching between the raised position and the lowered position of the pin  502  because the pin either rests on plurality of protrusions  520  or extends into the channels between them. 
         [0033]    While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.