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Etch rate monitor using collimated light and method of using same

  • US 5,337,144 A
  • Filed: 05/05/1992
  • Issued: 08/09/1994
  • Est. Priority Date: 06/19/1990
  • Status: Expired due to Term
First Claim
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1. An etch rate monitor for monitoring the etch rate of a substrate being etched in an etch chamber comprisinga) a light transmissive window in said etch chamber;

  • b) means for applying a collimated light beam through said window near the periphery thereof to said substrate at a normal angle of incidence to the surface of the substrate being etched;

    c) means for collecting reflected light having multiple diffraction orders of time varying intensity through said window at a substantial angle to the path of said collimated light;

    d) a photodetector, for said reflected light; and

    e) means coupled to said photodetector and responsive to the time varying intensity of the collected light for monitoring etch rate in said chamber.

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