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Position detecting apparatus

  • US 5,489,986 A
  • Filed: 04/25/1994
  • Issued: 02/06/1996
  • Est. Priority Date: 02/28/1989
  • Status: Expired due to Term
First Claim
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1. A projection type exposure apparatus including,a projection optical system for projecting a pattern formed on a mask;

  • a substrate stage member for holding a photosensitive substrate onto which the pattern is projected, and movable in a two dimensional X-Y plane substantially perpendicular to an optical axis of said projection optical axis and further movable in a Z direction along the optical axis; and

    a pattern position detecting device for radiating two beams, each of which intersects the other on said photosensitive substrate and has a frequency which is different from that of the other, and for optoelectrically detecting and converting beat light caused by interference between at least two diffracted beams generated along the same direction from a grating pattern on said photosensitive substrate, into a signal, and for determining a position of the grating pattern along a pitch direction thereof based on phase of the signal, thereby detecting the grating pattern formed on said photosensitive substrate or an alignment;

    said apparatus comprising;

    (a) a reference plate provided on said substrate stage member and having a reference grating pattern which is substantially the same as the grating pattern on said photosensitive substrate;

    (b) a first stage control system for positioning said substrate stage member in the X-Y plane so that the reference grating pattern is irradiated by the two beams from said pattern position detecting device;

    (c) a second stage control system for controlling movement of said substrate stage member along the Z direction go that said reference grating pattern is moved parallel to the optical axis of said projection optical system within a range where the two beams intersect;

    (d) a monitoring device to monitor the phase of the signal optoelectrically detected and converted from the beat light generated from the reference grating pattern by said pattern position detecting device at each predetermined change in position of said reference plate on said substrate stage member along the Z direction;

    (e) a calculating device to calculate an inclination of an imaginary line bisecting an intersect angle formed between the two beams at the grating pattern, based on a characteristic of a change in the phase of the signal with respect to a change in said position along the Z direction; and

    an optical element to compensate the incident angle of each of the two beams at the grating pattern so that the imaginary line is maintained substantially perpendicular to the pitch direction of said grating pattern.

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