Abstract:
An electrostatic chuck includes a dielectric disk having a support surface to support a substrate and an opposing second surface, wherein at least one chucking electrode is disposed within the dielectric disk; a radio frequency (RF) bias plate disposed below the dielectric disk; a plurality of lamps disposed below the RF bias plate to heat the dielectric disk; a metallic plate disposed below the lamps to absorb heat generated by the lamps; a shaft coupled to the second surface of the dielectric disk at a first end of the shaft to support the dielectric disk in a spaced apart relation to the RF bias plate and extending away from the dielectric disk and through the RF bias plate and the metallic plate; and a rotation assembly coupled to the shaft to rotate the shaft and the dielectric disk with respect to the RF bias plate, lamps, and metallic plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims benefit of U.S. provisional patent application Ser. No. 61/917,921, filed Dec. 18, 2013, which is herein incorporated by reference in its entirety. 
     
    
     FIELD 
       [0002]    Embodiments of the present disclosure generally relate to electrostatic chucks used to retain substrates in microelectronic device fabrication processes. 
       BACKGROUND 
       [0003]    Formation of some devices on substrates (e.g., STT-RAM) requires multiple layers of thin films which are deposited in a deposition chamber, such as a physical vapor deposition (PVD) chamber. In some embodiments, the substrate needs to be rotated during the deposition process to obtain good film uniformity. Deposition of some layers may also require the substrate to be heated. Further, the deposition process requires a high vacuum pressure. An electrostatic chuck is often used to electrostatically retain a substrate on a substrate support during the deposition process. Conventionally, an electrostatic chuck comprises a ceramic body having one or more electrodes disposed therein. Typical electrostatic chucks only move vertically up and down to facilitate substrate transfers. However, the inventors have observed that such a movement limitation prevents using these conventional electrostatic chucks for off-axis deposition due to non-uniform deposition on the substrate. 
         [0004]    Therefore, the inventors have provided embodiments of an improved rotatable heated electrostatic chuck. 
       SUMMARY 
       [0005]    Embodiments of rotatable, heated electrostatic chucks have been provided herein. In some embodiments, an electrostatic chuck includes: a dielectric disk having a support surface to support a substrate and an opposing second surface, wherein at least one chucking electrode is disposed within the dielectric disk; a radio frequency (RF) bias plate disposed below the dielectric disk; a plurality of lamps disposed below the RF bias plate to heat the dielectric disk; a metallic plate disposed below the plurality of lamps to absorb heat generated by the plurality of lamps; a shaft coupled to the second surface of the dielectric disk at a first end of the shaft to support the dielectric disk in a spaced apart relation to the RF bias plate and extending away from the dielectric disk and through the RF bias plate and the metallic plate; and a rotation assembly coupled to the shaft to rotate the shaft and the dielectric disk with respect to the RF bias plate, the plurality of lamps, and the metallic plate. 
         [0006]    In some embodiments, an electrostatic chuck includes: a dielectric disk having a support surface to support a substrate and an opposing second surface, wherein at least one chucking electrode is disposed within the dielectric disk; a radio frequency (RF) bias plate disposed below the dielectric disk; an inductor filter disposed in a conductor coupled to the at least one chucking electrode to minimize RF interference with the at least one chucking electrode; a plurality of lamps disposed below the RF bias plate to heat the dielectric disk; a metallic plate disposed below the plurality of lamps to absorb heat generated by the plurality of lamps; a shaft coupled to the second surface of the dielectric disk at a first end of the shaft to support the dielectric disk in a spaced apart relation to the RF bias plate and extending away from the dielectric disk and through the RF bias plate and the metallic plate; and a magnetic rotation assembly coupled to the shaft to rotate the shaft and the dielectric disk with respect to the RF bias plate, the plurality of lamps, and the metallic plate, wherein the magnetic rotation assembly includes an inner magnet attached to a lower portion of the shaft proximate to a second end of the shaft opposite the first end and an outer magnet disposed about the inner magnet to drive the rotation of the inner magnet. 
         [0007]    In some embodiments, an electrostatic chuck includes: a dielectric disk having a support surface to support a substrate and an opposing second surface, wherein at least one chucking electrode is disposed within the dielectric disk; a radio frequency (RF) bias plate disposed below the dielectric disk; a plurality of lamps disposed below the RF bias plate to heat the dielectric disk; a metallic plate disposed below the plurality of lamps to absorb heat generated by the plurality of lamps; a housing containing the RF bias plate, the plurality of lamps, and the metallic plate; a gap disposed between an outer diameter of the metallic plate and an inner surface of the housing, wherein the gap is sized such that when the metallic plate absorbs heat from the plurality of lamps, thermal expansion of the metallic plate causes the outer diameter of the metallic plate to contact the inner surface of the housing; a shaft coupled to the second surface of the dielectric disk at a first end of the shaft to support the dielectric disk in a spaced apart relation to the RF bias plate and extending away from the dielectric disk and through the RF bias plate and the metallic plate; and a magnetic rotation assembly coupled to the shaft to rotate the shaft and the dielectric disk with respect to the RF bias plate, the plurality of lamps, and the metallic plate. 
         [0008]    Other and further embodiments of the present disclosure are described below. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    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. 
           [0010]      FIG. 1  depicts a process chamber suitable for use with an electrostatic chuck in accordance with some embodiments of the present disclosure. 
           [0011]      FIG. 2  depicts a cross sectional view of an electrostatic chuck in accordance with some embodiments of the present disclosure. 
           [0012]      FIG. 3  depicts a cross sectional view of an upper portion of an electrostatic chuck in accordance with some embodiments of the present disclosure. 
           [0013]      FIG. 4  depicts a top view of a radio frequency (RF) bias plate and substrate heating apparatus in accordance with some embodiments of the present disclosure. 
       
    
    
       [0014]    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 
       [0015]    Embodiments of rotatable, heated electrostatic chucks are provided herein. The inventive electrostatic chucks may advantageously be rapidly heated and cooled (simultaneously with the rapid heating and cooling of a substrate disposed thereon), thereby providing process flexibility and increased throughput in substrate processing. Embodiments of the inventive electrostatic chuck may also advantageously reduce or eliminate damages to the substrate resulting from friction due to differences in thermal expansion of a substrate and electrostatic chuck during processing. 
         [0016]      FIG. 1  is a schematic cross-sectional view of plasma processing chamber in accordance with some embodiments of the present disclosure. In some embodiments, the plasma processing chamber is a physical vapor deposition (PVD) processing chamber. However, other types of processing chambers can also use or be modified for use with embodiments of the inventive electrostatic chuck described herein. 
         [0017]    The chamber  100  is a vacuum chamber which is suitably adapted to maintain sub-atmospheric pressures within a chamber interior volume  120  during substrate processing. The chamber  100  includes a chamber body  106  covered by a lid  104  which encloses a processing volume  119  located in the upper half of chamber interior volume  120 . The chamber  100  may also include one or more shields  105  circumscribing various chamber components to prevent unwanted reaction between such components and ionized process material. The chamber body  106  and lid  104  may be made of metal, such as aluminum. The chamber body  106  may be grounded via a coupling to ground  115 . 
         [0018]    A substrate support  124  is disposed within the chamber interior volume  120  to support and retain a substrate S, such as a semiconductor wafer, for example, or other such substrate as may be electrostatically retained. The substrate support  124  may generally comprise an electrostatic chuck  150  (described in more detail below with respect to  FIGS. 2-4 ) and a hollow support shaft  112  for supporting the electrostatic chuck  150 . The hollow support shaft  112  provides a conduit to provide, for example, process gases, fluids, coolants, power, or the like, to the electrostatic chuck  150 . 
         [0019]    In some embodiments, the hollow support shaft  112  is coupled to a lift mechanism  113  which provides vertical movement of the electrostatic chuck  150  between an upper, processing position (as shown in  FIG. 1 ) and a lower, transfer position (not shown). A bellows assembly  110  is disposed about the hollow support shaft  112  and is coupled between the electrostatic chuck  150  and a bottom surface  126  of chamber  100  to provide a flexible seal that allows vertical motion of the electrostatic chuck  150  while preventing loss of vacuum from within the chamber  100 . The bellows assembly  110  also includes a lower bellows flange  164  in contact with an o-ring  165  or other suitable sealing element which contacts bottom surface  126  to help prevent loss of chamber vacuum. 
         [0020]    The hollow support shaft  112  provides a conduit for coupling a fluid source  142 , a gas supply  141 , a chucking power supply  140 , and RF sources (e.g., RF plasma power supply  170  and RF bias power supply  117 ) to the electrostatic chuck  150 . In some embodiments, RF plasma power supply  170  and RF bias power supply  117  are coupled to the electrostatic chuck via respective RF match networks (only RF match network  116  shown). 
         [0021]    A substrate lift  130  may include lift pins  109  mounted on a platform  108  connected to a shaft  111  which is coupled to a second lift mechanism  132  for raising and lowering the substrate lift  130  so that the substrate “S” may be placed on or removed from the electrostatic chuck  150 . The electrostatic chuck  150  includes thru-holes (described below) to receive the lift pins  109 . A bellows assembly  131  is coupled between the substrate lift  130  and bottom surface  126  to provide a flexible seal which maintains the chamber vacuum during vertical motion of the substrate lift  130 . 
         [0022]    The chamber  100  is coupled to and in fluid communication with a vacuum system  114  which includes a throttle valve (not shown) and vacuum pump (not shown) which are used to exhaust the chamber  100 . The pressure inside the chamber  100  may be regulated by adjusting the throttle valve and/or vacuum pump. The chamber  100  is also coupled to and in fluid communication with a process gas supply  118  which may supply one or more process gases to the chamber  100  for processing a substrate disposed therein. 
         [0023]    In operation, for example, a plasma  102  may be created in the chamber interior volume  120  to perform one or more processes. The plasma  102  may be created by coupling power from a plasma power source (e.g., RF plasma power supply  170 ) to a process gas via one or more electrodes proximate to or within the chamber interior volume  120  to ignite the process gas and creating the plasma  102 . In some embodiments, a bias power may also be provided from a bias power supply (e.g., RF bias power supply  117 ) to one or more electrodes (described below) disposed within the electrostatic chuck  150  via a capacitively coupled bias plate (described below) to attract ions from the plasma towards the substrate S. 
         [0024]    In some embodiments, for example where the chamber  100  is a PVD chamber, a target  166  comprising a source material to be deposited on a substrate S may be disposed above the substrate and within the chamber interior volume  120 . The target  166  may be supported by a grounded conductive portion of the chamber  100 , for example an aluminum adapter through a dielectric isolator. In other embodiments, the chamber  100  may include a plurality of targets in a multi-cathode arrangement for depositing layers of different material using the same chamber. 
         [0025]    A controllable DC power source  168  may be coupled to the chamber  100  to apply a negative voltage, or bias, to the target  166 . The RF bias power supply  117  may be coupled to the substrate support  124  in order to induce a negative DC bias on the substrate S. In addition, in some embodiments, a negative DC self-bias may form on the substrate S during processing. In some embodiments, an RF plasma power supply  170  may also be coupled to the chamber  100  to apply RF power to the target  166  to facilitate control of the radial distribution of a deposition rate on substrate S. In operation, ions in the plasma  102  created in the chamber  100  react with the source material from the target  166 . The reaction causes the target  166  to eject atoms of the source material, which are then directed towards the substrate S, thus depositing material. 
         [0026]      FIG. 2  depicts a cross-sectional view of an electrostatic chuck (chuck  200 ) in accordance with embodiments of the present disclosure. The chuck  200  includes a disk  202 , a shaft  204  extending from the bottom of the disk  202 , and a housing  206  enclosing the disk  202 , the shaft  204 , and all the components (described below) of the chuck  200 . 
         [0027]    The disk  202  is formed of a dielectric material, such as a ceramic material, for example, aluminum nitride, aluminum oxide, boron nitride, alumina doped with titanium oxide, and the like. The disk  202  includes one or more chucking electrodes  208  disposed near an upper surface of the disk  202 . The one or more chucking electrodes  208  are fabricated from a suitable conductive material, such as molybdenum, titanium, or the like. The one or more chucking electrodes  208  may be arranged in any configuration that will sufficiently secure the substrate to the upper surface of the disk during processing. For example, the one or more chucking electrodes  208  may be arranged to provide a single electrode electrostatic chuck, a bipolar electrostatic chuck, or the like. 
         [0028]    As noted above, the disk  202  may also include one or more RF bias electrodes  210 . The one or more RF bias electrodes  210  are capacitively coupled to RF power to attract ions from the plasma towards the substrate disposed on the disk  202 . Power is delivered to the RF bias electrodes  210  via an RF bias plate  212  disposed below the disk  202  that receives power from an external RF power source (e.g., RF bias power supply  117 ). The RF bias plate  212  is capacitively coupled to the RF bias electrodes  210 , thereby removing any direct electrical coupling across a conductor. Accordingly, power can be delivered to the RF bias electrodes  210  while the disk  202  is being rotated. 
         [0029]    To facilitate heating of the disk  202  and a substrate when disposed thereon, the chuck  200  includes a lamp housing  216 , which includes a plurality of lamps  214 , disposed beneath the RF bias plate  212 . The lamp housing  216  is formed of a material capable of withstanding the heat of the plurality of lamps  214 . For example, the lamp housing  216  may be formed of a ceramic material. The plurality of lamps  214  includes any type of lamp capable of emitting enough heat to heat the disk  202  via radiation. For example, the plurality of lamps  214  may include halogen lamps. To allow the heat generated by the plurality of lamps  214  to reach the disk  202 , the RF bias plate  212  includes slots in positions corresponding to positions of the plurality of lamps  214 , as shown in more detail in  FIG. 4 . 
         [0030]    The chuck  200  may also include a bearing  218  located proximate to the disk  202  (for example, within about 3 inches of the disk  202 ) to provide increased rigidity to the chuck  200  during rotation. The bearing  218  may include, for example, a cross roller bearing, or the like. A metallic plate  220  is disposed beneath the lamp housing  216  to conduct heat away from the bearing  218  which could otherwise cause the bearing to expand and eventually seize. The metallic plate  220  may be formed of any process compatible metal or metal alloy such as, for example, aluminum. The metallic plate  220  is sized so that a gap is disposed between an outer edge of the metallic plate  220  and an inner surface of the housing  206 . During operation of the chuck  200 , the heat generated by the plurality of lamps  214  heats the metallic plate  220  causing it to expand such that the outer diameter, or edge, of the metallic plate  220  contacts the inner surface of the housing  206 . Upon contacting the inner surface of the housing  206 , the metallic plate  220  readily transfers heat to the housing  206  through conduction. Fluid channels (described below) may be disposed in the housing  206  to flow a heat transfer fluid (e.g., a coolant) to cool the housing  206 . 
         [0031]    The chuck  200  further includes a magnetic drive assembly  222  to rotate the disk  202 . The magnetic drive assembly  222  includes an inner magnet  222 A and an outer magnet  222 B. The inner magnet  222 A is attached, or fixed, to the shaft  204 . In some embodiments, the inner magnet  222 A is attached to a lower portion of the shaft  204  proximate an end of the shaft  204  opposite the disk  202 . The outer magnet  222 B is disposed outside of the housing  206  proximate to the inner magnet  222 A. The outer magnet  222 B may be driven by a suitable mechanism, for example by a belt drive or a motor, to drive the inner magnet  222 A, and the shaft  204  and the disk  202 . Because the inner magnet  222 A is disposed within the housing  206 , it is at vacuum pressure and because the outer magnet  222 B is disposed outside of the housing  206 , it is at atmospheric pressure. However, both the inner magnet  222 A and the outer magnet  222 B may instead be disposed within the housing  206 . Thus, the magnetic drive assembly  222  rotates the disk  202  and the shaft  204  with respect to the process chamber and the remaining components of the chuck  200  which remain stationary (e.g., the housing  206 , the lamp housing  216 , the metallic plate  220 , the RF bias plate  212 , and the like). Alternatively, the magnetic drive assembly  222  can use other configurations to rotate the disk  202  and the shaft  204 . For example, in some embodiments, the inner magnet  222 A and the outer magnet  222 B can function respectively as a rotor and stator with a conductor wrapped around the stator to electromagnetically drive the rotor. 
         [0032]    The chuck  200  also includes a bearing assembly  224  located at an end of the shaft  204  opposite the disk  202 . The bearing assembly  224  supports the shaft  204  and facilitates rotation of the shaft  204 . In addition, the inventors have provided an improved way to route power to the chucking electrodes  208  through the bearing assembly  224  to facilitate providing power to the chucking electrodes  208  while rotating the chuck  200 . Power is drawn from a DC power source  226  through connections in the housing  206  and routed to the bearing assembly  224 . Current flows through the bearing assembly  224  and is subsequently routed to the chucking electrodes  208  via chucking power lines  228  disposed within an interior of the shaft  204 . In order to avoid any interference with the chucking power supply (e.g., the DC power source  226 ), the bearing assembly may be coupled to an insulator  230 , which is coupled to an interior of the housing  206 . 
         [0033]    Referring to the cross sectional view of the chuck  200  in  FIG. 3 , the plurality of lamps  214  receive power from a plurality of conductors  304  disposed in a dielectric plate  302 , such as a ceramic plate. The conductors  304  may receive power from the DC power source  226  or from another power supply (not shown) via heater power lines (e.g., conductors)  320 . In some embodiments, a dielectric layer  306  may be disposed atop the dielectric plate  302  to protect the conductors  304  and prevent inadvertent contact between the conductors  304  and any other conductive elements of the chuck  200 . Openings in the dielectric layer  306  are provided to facilitate coupling the conductors  304  to respective lamps  214 . In some embodiments, the plurality of lamps may be divided into a plurality of zones, for example, an inner array of lamps and an independently controllable outer array of lamps, as illustrated in  FIG. 4 . 
         [0034]    As explained above, upon activation of the plurality of lamps  214 , heat is generated and the disk  202  is heated. Because the heat is emitted in every direction, and not only towards the disk  202 , the metallic plate  220  is disposed below the lamp housing  216  to absorb the heat. During the absorption process, the metallic plate  220  expands and begins to extend into a gap  316  between an outer edge of the metallic plate  220  and the housing  206 . Upon contacting the housing  206 , the metallic plate  220  transfers heat to the housing  206 . To keep the housing  206  cool, a plurality of fluid channels  308  are formed in the housing  206 . Any suitable coolant (e.g., water, propylene glycol, or the like) may be flowed through the fluid channels  308  to cool the housing  206 . 
         [0035]    The RF bias plate  212  may receive its power from the RF bias power supply  117  or from another power source (not shown) via RF power lines (e.g., conductors)  310 . In order to prevent interference of the RF waves with the chucking power supply, the chuck  200  includes an inductor filter  312 . The inductor filter  312  surrounds the chucking power lines  228  to filter out the RF waves. 
         [0036]    In order to facilitate placement and removal of a substrate on the disk  202 , the chuck  200  may also include a lift pin assembly including a plurality of lift pins  314  to raise and lower a substrate off of or onto the disk  202 . In some embodiments, at least one of the plurality of lift pins  314  may include a pyrometer to measure the temperature of the disk  202 . A region of the disk  202  disposed opposite the lift pins  314  may be treated to have a very high emissivity to facilitate monitoring the temperature of the disk  202  by the pyrometer 
         [0037]    In some embodiments, the shaft  204  may also include a conduit  318  for providing backside gases through the disk  202  to a backside of the substrate when disposed on the disk  202  during processing. The conduit  318  may be fluidly coupled to the gas supply  141 , described above with respect to  FIG. 1 . 
         [0038]      FIG. 4  depicts a top view of an RF bias plate and substrate heating apparatus in accordance with some embodiments of the present disclosure.  FIG. 4  illustrates the RF bias plate  212  including a plurality of openings  404  corresponding to positions of the plurality of lamps  214 . As explained above, the plurality of openings  404  allow heat generated by the plurality of lamps  214  to heat the disk  202 . The RF bias plate  212  and the lamp housing  216  also include a central hole  402  to allow the shaft  204  to pass therethrough and a plurality of holes  406  to allow the plurality of lift pins  314  to pass therethrough. Although shown as slots arranged in a particular configuration, the shape and number of the openings, as well as the shape and number of the lamps, may be varied to provide a desired heat profile on the disk  202 . 
         [0039]    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.