Patents by Inventor Ashwin M. Purohit

Ashwin M. Purohit has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Patent number: 9558980
    Abstract: Aspects of the present invention relate to ion implantation systems that make use of a vapor compression cooling system. In one embodiment, a thermal controller in the vapor compression system sends refrigeration fluid though a compressor and a condenser according to an ideal vapor compression cycle to help limit or prevent undesired heating of a workpiece during implantation, or to actively cool the workpiece.
    Type: Grant
    Filed: March 17, 2010
    Date of Patent: January 31, 2017
    Assignee: AXCELIS TECHNOLOGIES, INC.
    Inventors: William D. Lee, Ashwin M. Purohit, Marvin R. LaFontaine
  • Patent number: 9281227
    Abstract: A Johnsen-Rahbek (J-R) electrostatic clamp is provided for clamping a workpiece, wherein the J-R clamp has a dielectric layer having a clamping surface associated with the workpiece and a backside surface generally opposing the clamping surface. The dielectric layer has a plurality of regions, wherein each of the plurality of regions comprises one of a plurality of dielectric materials. Each of the plurality of dielectric materials has a baseline resistivity that is different from the remainder of the plurality of dielectric materials, and each of the plurality of regions of the dielectric layer has a baseline resistivity that is different from the remainder of the plurality of regions of the dielectric layer. A plurality of electrically conductive electrodes are associated with the backside surface of the dielectric layer, wherein each of the plurality of electrically conductive electrodes are associated with one or more of the plurality of regions of the dielectric layer.
    Type: Grant
    Filed: June 28, 2013
    Date of Patent: March 8, 2016
    Assignee: Axcelis Technologies, Inc.
    Inventors: William D. Lee, Ashwin M. Purohit
  • Patent number: 9048276
    Abstract: An apparatus and method are provided for selecting materials for forming an electrostatic clamp. The electrostatic clamp has a backing plate having a first coefficient of thermal expansion, wherein the backing plate provides structural support and rigidity to the electrostatic clamp. The electrostatic clamp further has a clamping plate having a clamping surface associated with contact with a workpiece, wherein the clamping plate has a second coefficient of thermal expansion associated therewith. The clamping plate is bonded, attached or grown to the backing plate, wherein minimal deflection of the clamping plate is evident across a predetermined temperature range. The first coefficient of thermal expansion and second coefficient of thermal expansion, for example, are substantially similar, and vary by no greater than a factor of three.
    Type: Grant
    Filed: May 26, 2011
    Date of Patent: June 2, 2015
    Assignee: Axcelis Technologies, Inc.
    Inventors: William D. Lee, Ashwin M. Purohit
  • Patent number: 8941968
    Abstract: An electrostatic clamp is provided, having a clamping plate, wherein a clamping surface of the clamping plate is configured to contact the workpiece. A voltage applied to one or more electrodes selectively electrostatically attracts the workpiece to the clamping surface. One or more auxiliary clamping members are further provided wherein the one or more auxiliary clamping members are configured to selectively secure at least a portion of the workpiece to the clamping surface. A temperature monitoring device configured to determine a temperature of the workpiece is provided, and a controller is configured to selectively clamp the workpiece to the clamping surface via a control of the voltage to the one or more electrodes and the one or more auxiliary clamping members, based, at least in part, on the temperature of the workpiece.
    Type: Grant
    Filed: June 3, 2011
    Date of Patent: January 27, 2015
    Assignee: Axcelis Technologies, Inc.
    Inventors: Perry J. I. Justesen, Allan D. Weed, William Davis Lee, Ashwin M. Purohit, Robert D. Rathmell, Gary M. Cook
  • Publication number: 20150002983
    Abstract: A Johnsen-Rahbek (J-R) electrostatic clamp is provided for clamping a workpiece, wherein the J-R clamp has a dielectric layer having a clamping surface associated with the workpiece and a backside surface generally opposing the clamping surface. The dielectric layer has a plurality of regions, wherein each of the plurality of regions comprises one of a plurality of dielectric materials. Each of the plurality of dielectric materials has a baseline resistivity that is different from the remainder of the plurality of dielectric materials, and each of the plurality of regions of the dielectric layer has a baseline resistivity that is different from the remainder of the plurality of regions of the dielectric layer. A plurality of electrically conductive electrodes are associated with the backside surface of the dielectric layer, wherein each of the plurality of electrically conductive electrodes are associated with one or more of the plurality of regions of the dielectric layer.
    Type: Application
    Filed: June 28, 2013
    Publication date: January 1, 2015
    Inventors: William D. Lee, Ashwin M. Purohit
  • Patent number: 8902560
    Abstract: An electrostatic chuck and method for clamping a workpiece is provided. The ESC comprises a clamping plate having a clamping surface, and one or more electrodes. An electric potential applied to the one or more electrodes selectively clamps the workpiece to the clamping surface. A punch is operably coupled to the clamping plate and an electrical ground, wherein the punch comprises a trigger mechanism and a punch tip. The punch tip translates between extended and retracted positions, wherein a point of the punch tip is proud of the clamping surface when the punch tip is in the extended position. The punch tip is configured to translate toward the clamping surface upon clamping the workpiece to the clamping plate. Upon reaching the retracted position, the trigger mechanism imparts an impact force to the punch tip, forcing the punch tip into the workpiece and providing an electrical ground connection to the workpiece.
    Type: Grant
    Filed: October 31, 2008
    Date of Patent: December 2, 2014
    Assignee: Axcelis Technologies, Inc.
    Inventors: David B. Smith, William D. Lee, Marvin R. LaFontaine, Ashwin M. Purohit
  • Patent number: 8797706
    Abstract: A clamping device and method is provided for securing first and second workpieces having different sizes to a clamping device and providing thermal conditioning thereto. An electrostatic clamping plate having a diameter associated with the first workpiece surrounds a central portion of the clamp. A non-electrostatic central portion provides a heater within the annulus, wherein the central portion has a diameter associated with the second workpiece. A workpiece carrier is provided, wherein the workpiece carrier is configured to hold the second workpiece above the heater, and wherein a diameter of the workpiece carrier is associated with the electrostatic clamping plate annulus. The annulus selectively electrostatically clamps the workpiece carrier or a circumferential portion of the first workpiece to its clamping surface, therein selectively maintaining a position of the first or second workpiece with respect to the annulus or non-electrostatic central portion.
    Type: Grant
    Filed: June 7, 2011
    Date of Patent: August 5, 2014
    Assignee: Axcelis Technologies, Inc.
    Inventors: William Davis Lee, Gary M. Cook, Perry J. I. Justesen, Ashwin M. Purohit, Robert D. Rathmell, Allan D. Weed
  • Patent number: 8422193
    Abstract: An electrostatic clamp (ESC), system, and method for clamping a workpiece is provided. A clamping plate of the ESC has central disk and an annulus encircling the central disk, wherein the central disk is recessed from the annulus by a gap distance, therein defining a volume. Backside gas delivery apertures are positioned proximate to an interface between the annulus and the central disk. A first voltage to a first electrode of the annulus clamps a peripheral region of the workpiece to a first layer. A second voltage to a second electrode of the central disk generally compensates for a pressure of a backside gas within the volume. The ESC can be formed of J-R- or Coulombic-type materials. A cooling plate associated with the clamping plate further provides cooling by one or more cooling channels configured to route a cooling fluid therethrough.
    Type: Grant
    Filed: December 19, 2006
    Date of Patent: April 16, 2013
    Assignee: Axcelis Technologies, Inc.
    Inventors: Teng Chao D. Tao, William D. Lee, Marvin R. LaFontaine, Ashwin M. Purohit
  • Patent number: 8270142
    Abstract: One embodiment of the present invention relates to a method for declamping a semiconductor wafer that is electrically adhered to a surface of an electrostatic chuck by a clamping voltage. In this method, the clamping voltage is deactivated. For a time following the deactivation, a first region of the wafer is lifted an first distance from the surface of the electrostatic chuck while a second region of the wafer remains adhered to the surface of the electrostatic chuck. A predetermined condition is monitored during the time. The second region is lifted from the surface of the electrostatic chuck when the predetermined condition is met.
    Type: Grant
    Filed: December 10, 2008
    Date of Patent: September 18, 2012
    Assignee: Axcelis Technologies, Inc.
    Inventors: William D. Lee, Ashwin M. Purohit, Marvin R. LaFontaine, Richard J. Rzeszut
  • Patent number: 8241425
    Abstract: The present invention is directed to an apparatus and method of forming a thermos layer surrounding a chuck for holding a wafer during ion implantation. The thermos layer is located below a clamping surface, and comprises a vacuum gap and an outer casing encapsulating the vacuum gap. The thermos layer provides a barrier blocking condensation to the outside of the chuck within a process chamber by substantially preventing heat transfer between the chuck when it is cooled and the warmer environment within the process chamber.
    Type: Grant
    Filed: January 23, 2009
    Date of Patent: August 14, 2012
    Assignee: Axcelis Technologies, Inc.
    Inventors: William D. Lee, Ashwin M. Purohit, Marvin R. LaFontaine
  • Patent number: 8228658
    Abstract: A method for clamping a workpiece involves placing the workpiece on a clamping surface of an electrostatic clamp. A clamping voltage is applied to the electrostatic clamp at a first frequency, therein providing a first clamping force between the workpiece and the electrostatic clamp. The application of clamping voltage at the first frequency is halted and another clamping voltage at a second frequency is applied to the electrostatic clamp, therein providing a second clamping force between the workpiece and the electrostatic clamp. The second frequency is greater than the first frequency, wherein the second clamping force is less than the first clamping force. The application of the clamping voltage at the second frequency is then halted, and the workpiece is removed from the electrostatic clamp. The clamping voltage can be controlled based on a set of performance criteria, such as a desired minimum clamping force and a maximum de-clamp time.
    Type: Grant
    Filed: February 8, 2007
    Date of Patent: July 24, 2012
    Assignee: Axcelis Technologies, Inc.
    Inventor: Ashwin M. Purohit
  • Publication number: 20110299218
    Abstract: A clamping device and method is provided for securing first and second workpieces having different sizes to a clamping device and providing thermal conditioning thereto. An electrostatic clamping plate having a diameter associated with the first workpiece surrounds a central portion of the clamp. A non-electrostatic central portion provides a heater within the annulus, wherein the central portion has a diameter associated with the second workpiece. A workpiece carrier is provided, wherein the workpiece carrier is configured to hold the second workpiece above the heater, and wherein a diameter of the workpiece carrier is associated with the electrostatic clamping plate annulus. The annulus selectively electrostatically clamps the workpiece carrier or a circumferential portion of the first workpiece to its clamping surface, therein selectively maintaining a position of the first or second workpiece with respect to the annulus or non-electrostatic central portion.
    Type: Application
    Filed: June 7, 2011
    Publication date: December 8, 2011
    Applicant: Axcelis Technologies, Inc.
    Inventors: William Davis Lee, Gary M. Cook, Perry J.I. Justesen, Ashwin M. Purohit, Robert D. Rathmell, Allan D. Weed
  • Publication number: 20110299217
    Abstract: An electrostatic clamp is provided, having a clamping plate, wherein a clamping surface of the clamping plate is configured to contact the workpiece. A voltage applied to one or more electrodes selectively electrostatically attracts the workpiece to the clamping surface. One or more auxiliary clamping members are further provided wherein the one or more auxiliary clamping members are configured to selectively secure at least a portion of the workpiece to the clamping surface. A temperature monitoring device configured to determine a temperature of the workpiece is provided, and a controller is configured to selectively clamp the workpiece to the clamping surface via a control of the voltage to the one or more electrodes and the one or more auxiliary clamping members, based, at least in part, on the temperature of the workpiece.
    Type: Application
    Filed: June 3, 2011
    Publication date: December 8, 2011
    Applicant: Axcelis Technologies, Inc.
    Inventors: Perry J.I. Justesen, Allan D. Weed, William Davis Lee, Ashwin M. Purohit, Robert D. Rathmell, Gary M. Cook
  • Patent number: 8023247
    Abstract: The present invention is directed to an electrostatic chuck (ESC) with a compliant layer formed from TT-Kote® and a method of forming a clamping plate for an ESC. The ESC comprises a compliant layer having a low friction surface for reducing or eliminating particulates generated from thermal expansion. The method comprises forming a clamping member for a substrate comprising a ceramic material and a ceramic surface, and coating the ceramic surface with a compliant layer comprising an organic silicide or TT-Kote®.
    Type: Grant
    Filed: December 10, 2008
    Date of Patent: September 20, 2011
    Assignee: Axcelis Technologies, Inc.
    Inventors: Ashwin M. Purohit, Marvin R. LaFontaine, William D. Lee, Richard J. Rzeszut
  • Patent number: 7952851
    Abstract: An electrostatic chuck and method for clamping and de-clamping a workpiece is provided. The ESC comprises a clamping plate having a clamping surface, and one or more electrodes. An electric potential applied to the one or more electrodes selectively clamps the workpiece to the clamping surface. An arc pin operably coupled to the clamping plate and a power source provides an arc for penetrating an insulating layer of the workpiece. The arc pin is selectively connected to an electrical ground, wherein upon removal of the insulative layer of the workpiece, the arc pin provides an electrical ground connection to the workpiece.
    Type: Grant
    Filed: October 31, 2008
    Date of Patent: May 31, 2011
    Assignee: Axcelis Technologies, Inc.
    Inventors: Marvin R. LaFontaine, Ari Eiriksson, Ashwin M. Purohit, William D. Lee
  • Publication number: 20100187447
    Abstract: The present invention is directed to an apparatus and method of forming a thermos layer surrounding a chuck for holding a wafer during ion implantation. The thermos layer is located below a clamping surface, and comprises a vacuum gap and an outer casing encapsulating the vacuum gap. The thermos layer provides a barrier blocking condensation to the outside of the chuck within a process chamber by substantially preventing heat transfer between the chuck when it is cooled and the warmer environment within the process chamber.
    Type: Application
    Filed: January 23, 2009
    Publication date: July 29, 2010
    Applicant: Axcelis Technologies, Inc.
    Inventors: William D. Lee, Ashwin M. Purohit, Marvin R. LaFontaine
  • Publication number: 20100171044
    Abstract: Aspects of the present invention relate to ion implantation systems that make use of a vapor compression cooling system. In one embodiment, a thermal controller in the vapor compression system sends refrigeration fluid though a compressor and a condenser according to an ideal vapor compression cycle to help limit or prevent undesired heating of a workpiece during implantation, or to actively cool the workpiece.
    Type: Application
    Filed: March 17, 2010
    Publication date: July 8, 2010
    Applicant: Axcelis Technologies, Inc.
    Inventors: William D. Lee, Ashwin M. Purohit, Marvin R. LaFontaine
  • Patent number: 7751172
    Abstract: The present invention is directed to a system and a method for peeling a wafer off of an electrostatic clamp (ESC). The ESC removal system comprises a electrostatic clamp and a wafer electrically coupled and physically in contact with each other. A plurality of grippers or pins are arranged with respect to the wafer and the ESC to allow the wafer to be peeled off or removed section by section from the electrostatic clamp. The system and method allow the wafer to be removed with a much lower pull force than current systems and methods.
    Type: Grant
    Filed: October 18, 2006
    Date of Patent: July 6, 2010
    Assignee: Axcelis Technologies, Inc.
    Inventors: Ashwin M. Purohit, Dale Stone, Dave Broyer, Steve Drummond
  • Publication number: 20100142114
    Abstract: The present invention is directed to an electrostatic chuck (ESC) with a compliant layer formed from TT-Kote® and a method of forming a clamping plate for an ESC. The ESC comprises a compliant layer having a low friction surface for reducing or eliminating particulates generated from thermal expansion. The method comprises forming a clamping member for a substrate comprising a ceramic material and a ceramic surface, and coating the ceramic surface with a compliant layer comprising an organic silicide or TT-Kote®.
    Type: Application
    Filed: December 10, 2008
    Publication date: June 10, 2010
    Applicant: Axcelis Technologies, Inc.
    Inventors: Ashwin M. Purohit, Marvin R. LaFontaine, William D. Lee, Richard J. Rzeszut
  • Publication number: 20100142113
    Abstract: One embodiment of the present invention relates to a method for declamping a semiconductor wafer that is electrically adhered to a surface of an electrostatic chuck by a clamping voltage. In this method, the clamping voltage is deactivated. For a time following the deactivation, a first region of the wafer is lifted an first distance from the surface of the electrostatic chuck while a second region of the wafer remains adhered to the surface of the electrostatic chuck. A predetermined condition is monitored during the time. The second region is lifted from the surface of the electrostatic chuck when the predetermined condition is met.
    Type: Application
    Filed: December 10, 2008
    Publication date: June 10, 2010
    Applicant: Axcelis Technologies, Inc.
    Inventors: William D. Lee, Ashwin M. Purohit, Marvin R. LaFontaine, Richard J. Rzeszut