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Wafer sensing and clamping monitor

  • US 5,436,790 A
  • Filed: 01/15/1993
  • Issued: 07/25/1995
  • Est. Priority Date: 01/15/1993
  • Status: Expired due to Term
First Claim
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1. Apparatus for securing a semiconductor wafer to a wafer support comprising:

  • a) a wafer support including spaced electrodes for attracting wafers to the wafer support by means of an electrostatic attraction between the wafer support and wafers placed onto the wafer support;

    b) capacitive sensing circuitry coupled to the spaced electrodes for monitoring a capacitance and producing an output signal related to said capacitance;

    c) a power supply for energizing the two electrodes; and

    d) a controller to apply energization signals from the power supply to the two electrodes, thereby attracting the wafer to the wafer support once a wafer has been placed onto the wafer support;

    e) said controller including an input coupled to an output from the capacitive sensing circuitry corresponding to a sensed capacitance indicating a presence of the wafer on the wafer support and having an output for initiating one or more processing steps based upon a change in the output from the capacitive sensing circuit indicating the wafer is properly secured to the wafer support.

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