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Exposure method and apparatus

  • US 5,448,332 A
  • Filed: 11/21/1994
  • Issued: 09/05/1995
  • Est. Priority Date: 12/25/1992
  • Status: Expired due to Term
First Claim
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1. An apparatus for exposing a pattern, formed on a mask, on each of a plurality of partitioned areas on a photosensitive substrate by a step-and-repeat scheme, comprising:

  • a projection optical system for projecting the pattern of the mask on the photosensitive substrate;

    a substrate stage for holding the photosensitive substrate and two-dimensionally moving the photosensitive substrate within a plane perpendicular to an optical axis of said projection optical system;

    means for projecting a pattern image having a predetermined shape on the photosensitive substrate and photoelectrically detecting light reflected by the photosensitive substrate to detect a position at each of a plurality of points on the photosensitive substrate along an optical axis of said projection optical system; and

    means for, when each of a plurality of measurement points in a partitioned area on which a pattern of the mask is to be exposed next coincides with or approaches the pattern image, detecting an offset amount between an imaging plane of said projection optical system and the next partitioned area along the optical axis during a stepping operation of said substrate stage,wherein the imaging plane and the next partitioned area are relatively moved along the optical axis in accordance with the measured offset amount before the pattern of the mask is exposed on the next partitioned area.

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