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Method of feedback control of ESC voltage using wafer voltage measurement at the bias supply output

  • US 7,375,947 B2
  • Filed: 02/07/2007
  • Issued: 05/20/2008
  • Est. Priority Date: 05/10/2005
  • Status: Expired due to Fees
First Claim
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1. In a plasma reactor having an electrostatic chuck (ESC) supporting a wafer to be processed, a method of processing the wafer while controlling an ESC clamping voltage, comprising:

  • applying RF bias power to said ESC from a bias power source at an input to said ESC and applying a D.C. voltage at said input to said ESC from a D.C. voltage source;

    measuring voltage and current near said input to produce a measured voltage and a measured current;

    providing a wafer voltage signal as a sum of said measured voltage and said measured current multiplied by first and second coefficients respectively, said wafer voltage signal representing the voltage on a wafer supported on said ESC; and

    computing a wafer clamping voltage as a difference between a D.C. component of said wafer voltage signal and said D.C. voltage from said D.C. voltage source, and controlling said D.C. voltage to regulate said wafer clamping voltage.

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