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Proceedings Paper

Identifying And Monitoring Effects Of Lens Aberrations In Projection Printing
Author(s): Kenny K.H. Toh; Andrew R. Neureuther
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Paper Abstract

Basic studies of projection printed images are presented to identify the types of patterns which are most susceptible to residual aberrations and to establish test structures which may be used to monitor the presence of critical types of residuals. These effects are explored by including arbitrary lens optical path difference (OPD) aberration functions in a two-dimensional optical image simulation program associated with SAMPLE. The lens aberration function is expressed either in Zernike polynomials or a series expansion. The intensity is calculated from Hopkin's transmission cross-coefficient formula-tion with a self-checking algorithm. A catalog of results is presented here for the dominant primary aberrations of coma and astigmatism for a fixed maximum OPD of 0.4 λ. Contact holes are shown to be much more susceptible to astigmatism than coma and the traditional checkerboard test pattern is verified as a sensitive diagnostic pattern. An alternative structure con-sisting of thin lines with a short break is shown to be even more sensitive to astigmatism and useful for distinguishing it from coma. A further improvement in sensitivity is obtained through the use of small nonprintable defect-like features in proximity to regular features which coherently interact with the blurred image of the feature. A test target of this type is recommended for monitoring coma.

Paper Details

Date Published: 1 January 1987
PDF: 8 pages
Proc. SPIE 0772, Optical Microlithography VI, (1 January 1987); doi: 10.1117/12.967051
Show Author Affiliations
Kenny K.H. Toh, University of California (United States)
Andrew R. Neureuther, University of California (United States)

Published in SPIE Proceedings Vol. 0772:
Optical Microlithography VI
Harry L. Stover, Editor(s)

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