To extend optical lithography technology to the sub-100 nm linewidth regime using 157 nm UV light, all mask-related distortions must be eliminated or minimized. Thermal distortion during the scanning exposure process is a significant contribution to the total pattern placement error budget for advanced photomasks. This paper presents the results of numerical simulations predicting the transient thermal response and the corresponding structural response of modified fused silica reticles during scanning exposure with 157 nm light. Full threedimensional finite element heat transfer and structural models have been developed. Transient and periodic steady- state temperature distributions have been determined for typical exposure duty cycles. Corresponding in-plane and out-of-plane thermal distortions are also presented. Parametric studies were performed to identify the effect of the system variables on the thermomechanical response of the reticle. Simulation results for 157 nm and 193 nm technologies are subsequently compared.

Date Published: 22 January 2001
PDF: 9 pages
Proc. SPIE 4186, 20th Annual BACUS Symposium on Photomask Technology, (22 January 2001); doi: 10.1117/12.410752

Published in SPIE Proceedings Vol. 4186:
20th Annual BACUS Symposium on Photomask Technology
Brian J. Grenon; Giang T. Dao, Editor(s)