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Method and system for high speed height control of a substrate surface within a wafer inspection system

  • US 9,097,645 B2
  • Filed: 08/19/2014
  • Issued: 08/04/2015
  • Est. Priority Date: 08/23/2013
  • Status: Active Grant
First Claim
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1. A system for high speed height control of a surface of the substrate within a wafer inspection system comprising:

  • a dynamically actuatable substrate stage assembly including a substrate stage for securing a substrate;

    an actuator configured to actuate the substrate along a direction substantially perpendicular to the surface of the substrate;

    a height error detection system configured to measure height error of a surface of the substrate at a position of inspection of the surface;

    a displacement sensor operably coupled to the substrate stage assembly and configured to measure a displacement substantially perpendicular to the surface of the substrate at the location of the substrate stage assembly;

    a feedback control system communicatively coupled to the height error detection system and the actuator, wherein the feedback control system is configured to;

    receive one or more height error measurements from the height error detection system; and

    responsive to the measured one or more height error measurements, adjust an actuation state of the actuator in order to maintain the substrate surface substantially at an imaging plane of a detector of the inspection system or a focus of illumination of the inspection system; and

    a feed forward control system communicatively coupled to the height error detection system and the actuator, wherein the feed forward control system is configured to;

    receive one or more displacement measurements from the displacement sensor;

    responsive to one or more displacement values from the one or more displacements measurements with the one or more height error values from the one or more height error measurements, generate one or more displacement targets; and

    actuate the actuator using at least one of the one or more displacement targets in order to maintain the substrate surface substantially at an imaging plane of a detector of the inspection system or a focus of illumination of the inspection system.

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