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Proceedings Paper

Precise alignment using optical phase-shifting technique
Author(s): Yiping Xu
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Paper Abstract

A new precise alignment technique using optical phase-shifting, Fourier transform and spatial filtering has been developed for registering a symmetric pattern on the substrate to a phase-shifting pattern on the reticle. The alignment between two marks was determined by detecting a minimum point in the zero order spatial frequency intensity of the light reflected from the alignment mark on the substrate. The minimum is due to the complete phase-cancellation when the alignment marks co-centered. The theoretical analysis and computer simulations were performed to show that this technique is not affected by variations of linewidth and step height of the alignment mark pattern as well as variations of optical properties of the substrate in which the alignment mark is built. The preliminary experimental results were in good agreement with the calculations. It has been shown that this technique does not have the alignment ambiguity problem existed in the techniques using grating pattern and detecting interference moire image. Current results indicate that the overlay accuracy of the technique can be better than 0. 1 .tm.

Paper Details

Date Published: 1 June 1990
PDF: 9 pages
Proc. SPIE 1264, Optical/Laser Microlithography III, (1 June 1990); doi: 10.1117/12.20188
Show Author Affiliations
Yiping Xu, Univ. of California/Santa Barb (United States)

Published in SPIE Proceedings Vol. 1264:
Optical/Laser Microlithography III
Victor Pol, Editor(s)

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