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Focusing method

  • US 5,323,016 A
  • Filed: 06/28/1993
  • Issued: 06/21/1994
  • Est. Priority Date: 02/09/1990
  • Status: Expired due to Term
First Claim
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1. A method of bringing a surface of a wafer into coincidence with an image plane of a projection optical system on the basis of detection of a deviation of the wafer surface from a reference plane of a deviation detecting sensor, comprising the steps of:

  • moving the wafer surface to a position close to the reference plane;

    detecting a deviation of the wafer surface from the reference plane;

    correcting any inclination of the wafer surface in accordance with the detected deviation; and

    moving, after said correcting step, the wafer surface along an optical axis of the projection optical system in accordance with an amount which is predetermined on the basis of the deviation of the image plane with respect to the reference plane of the deviation detecting sensor.

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