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Ultrasonic methods and apparatus for the in-situ detection of workpiece loss

  • US 6,264,532 B1
  • Filed: 03/28/2000
  • Issued: 07/24/2001
  • Est. Priority Date: 03/28/2000
  • Status: Expired due to Fees
First Claim
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1. An apparatus for detecting the presence of an extraneous material on a polishing pad of a chemical mechanical polishing machine during polishing of a workpiece held by a carrier against a surface of the polishing pad, the apparatus comprising:

  • an ultrasonic source proximate the carrier, the ultrasonic source configured to direct an input ultrasonic signal at an area on the surface of the polishing pad, wherefrom the input ultrasonic signal is reflected to created a reflected signal; and

    an ultrasonic detector proximate the carrier, the ultrasonic detector configured to receive the reflected signal, wherein the reflected signal is processed to generate an output indicative of the presence or absence of the extraneous material at the area on the polishing pad.

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