Scan and repeat high resolution projection lithography system

  • US 4,924,257 A
  • Filed: 10/05/1988
  • Issued: 05/08/1990
  • Est. Priority Date: 10/05/1988
  • Status: Expired due to Term
First Claim
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1. A high resolution, high exposure speed, large effective field size scan and repeat lithography system for producing precise images of a pattern that is present on a mask onto a substrate, comprising:

  • (a) a substrate stage capable of scanning a substrate in one dimension and, when not scanning in that dimension, capable of moving laterally in a direction perpendicular to the scan direction so as to position the substrate for another scan;

    said substrate stage thus being capable of exposing the full substrate by breaking up the substrate are into a certain number of parallel strips, and exposing each of said strips by scanning the length of the strip across a fixed illumination region;

    (b) a mask stage capable of scanning in the same dimension as, and synchronized with, the substrate stage, at a speed equal to the substrate stage scanning speed multiplied by a certain ratio M;

    (c) an illumination subsystem having the desired characteristics of wavelength and intensity distribution, having an effective source plane in the shape of a polygon, and capable of uniformly illuminating a polygon-shaped region on the mask;

    (d) a projection subsystem for imaging the said polygon-shaped illuminated region on the mask onto the substrate, having an object-to-image reduction ratio M, having the desired image resolution, and having an image field in the shape of a polygon and of an area smaller than the desired effective image field size of the said lithography system; and

    (e) control means to operatively interrelate said substrate stage, said mask stage and said illumination subsystem, and to provide complementary exposures in an overlap region between the areas exposed by adjacent scans in such a way that the exposure dose distribution received in the overlap region is seamless, and such that the exposure dose delivered across the entire substrate is uniform.

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