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Off-axis levelling in lithographic projection apparatus

  • US 6,882,405 B2
  • Filed: 10/17/2003
  • Issued: 04/19/2005
  • Est. Priority Date: 03/08/1999
  • Status: Expired due to Term
First Claim
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1. A method of calibrating a lithographic projection apparatus comprising:

  • generating a first height map of a substrate by measuring a position in a first direction substantially perpendicular to a surface of said substrate of a plurality of points on said substrate surface and simultaneously measuring a position of a substrate holder using a first position detection system, at a measurement station of a lithographic system;

    generating a second height map of said substrate by measuring a position in said first direction of said plurality of points on said substrate surface and simultaneously measuring a position of said substrate holder using a second position detection system, at an exposure station of the lithographic system; and

    comparing said first and second height maps to calibrate said first and second position detection systems.

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