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Proceedings Paper

Improving the CD linearity and proximity performance of photomasks written on the Sigma7500-II DUV laser writer through embedded OPC
Author(s): Anders Österberg; Lars Ivansen; Angela Beyerl; Tom Newman; Amanda Bowhill; Emile Sahouria; Steffen Schulze
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Paper Abstract

Optical proximity correction (OPC) is widely used in wafer lithography to produce a printed image that best matches the design intent while optimizing CD control. OPC software applies corrections to the mask pattern data, but in general it does not compensate for the mask writer and mask process characteristics. The Sigma7500-II deep-UV laser mask writer projects the image of a programmable spatial light modulator (SLM) using partially coherent optics similar to wafer steppers, and the optical proximity effects of the mask writer are in principle correctable with established OPC methods. To enhance mask patterning, an embedded OPC function, LinearityEqualizeTM, has been developed for the Sigma7500- II that is transparent to the user and which does not degrade mask throughput. It employs a CalibreTM rule-based OPC engine from Mentor Graphics, selected for the computational speed necessary for mask run-time execution. A multinode cluster computer applies optimized table-based CD corrections to polygonized pattern data that is then fractured into an internal writer format for subsequent data processing. This embedded proximity correction flattens the linearity behavior for all linewidths and pitches, which targets to improve the CD uniformity on production photomasks. Printing results show that the CD linearity is reduced to below 5 nm for linewidths down to 200 nm, both for clear and dark and for isolated and dense features, and that sub-resolution assist features (SRAF) are reliably printed down to 120 nm. This reduction of proximity effects for main mask features and the extension of the practical resolution for SRAFs expands the application space of DUV laser mask writing.

Paper Details

Date Published: 30 October 2007
PDF: 20 pages
Proc. SPIE 6730, Photomask Technology 2007, 673034 (30 October 2007); doi: 10.1117/12.747074
Show Author Affiliations
Anders Österberg, Micronic Laser Systems AB (Sweden)
Lars Ivansen, Micronic Laser Systems AB (Sweden)
Angela Beyerl, Micronic Laser Systems AB (Sweden)
Tom Newman, Micronic Laser Systems AB (Sweden)
Amanda Bowhill, Mentor Graphics Corp. (United States)
Emile Sahouria, Mentor Graphics Corp. (United States)
Steffen Schulze, Mentor Graphics Corp. (United States)

Published in SPIE Proceedings Vol. 6730:
Photomask Technology 2007
Robert J. Naber; Hiroichi Kawahira, Editor(s)

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