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Proceedings Paper

Resist vector: connecting the aerial image to reality
Author(s): Steven G. Hansen
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Paper Abstract

Lithographic performance is controlled by both the projected aerial image and the photoresist process. It is usually easier to calculate the output of the optical system than to construct an accurate predictive model for the photoresist process. This point, coupled with the trend toward extremely high contrast photoresists where the resist starts to act like an ideal image threshold detector, means that aerial images alone are increasingly useful for predicting performance. In this work, discrepancies between resist processes with finite imaging contrast, and aerial image predictions are explored. The method used is to construct several lithographic problems (various line and hole patterns with high NA lenses) and to directly calculate differences for important responses such as exposure latitude, dense:isolated bias, and isofocal curvature. The expected performance range for resist processes can be found with a simulation program and systematically varied resist models, producing hundreds of trial cases. The results show that the resist process predictions deviate from the aerial image predictions in a consistent way; interpretable as a resist vector whose magnitude varies depending on the details of the resist process, but whose direction does not vary much. Knowledge of the vector provides a route for extrapolating aerial image calculations to what actually prints on the wafer. Physical explanations based on finite dissolution contrast and non-zero diffusion are offered. Where possible, experimental data is used to support the arguments.

Paper Details

Date Published: 24 July 2002
PDF: 15 pages
Proc. SPIE 4690, Advances in Resist Technology and Processing XIX, (24 July 2002); doi: 10.1117/12.474236
Show Author Affiliations
Steven G. Hansen, ASML (United States)

Published in SPIE Proceedings Vol. 4690:
Advances in Resist Technology and Processing XIX
Theodore H. Fedynyshyn, Editor(s)

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