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Self referencing heterodyne reflectometer and method for implementing

  • US 7,545,503 B2
  • Filed: 09/27/2005
  • Issued: 06/09/2009
  • Est. Priority Date: 09/27/2005
  • Status: Active Grant
First Claim
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1. A method for measuring a thickness parameter comprising:

  • measuring a heterodyne phase shift, comprising;

    receiving a split frequency, dual polarized beam;

    detecting a reference signal from the split frequency, dual polarized beam;

    propagating the split frequency, dual polarized beam to a target;

    receiving a reflected split frequency, dual polarized beam from the target;

    detecting a measurement signal from the reflected split frequency, dual polarized beam; and

    measuring a phase difference between the reference signal and the measurement signal for the reflected split frequency, dual polarized beam;

    measuring a self referencing phase shift, comprising;

    receiving a split frequency, p-polarized beam;

    detecting a reference signal from the split frequency, p-polarized beam;

    propagating the split frequency, p-polarized beam to a target;

    receiving a reflected split frequency, p-polarized beam from the target;

    detecting a second measurement signal from the reflected split frequency, p-polarized beam; and

    measuring a self referencing phase difference between the reference signal and the measurement signal for the split frequency, p-polarized beam;

    calibrating the phase difference for the target with the self referencing phase difference; and

    finding a thickness parameter from the phase difference for the target.

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