Hard pellicle study for 157-nm lithography

Emily Y. Shu; Fu-Chang Lo; Florence O. Eschbach; Eric P. Cotte; Roxann L. Engelstad; Edward G. Lovell; Kaname Okada; Shinya Kikugawa

doi:10.1117/12.477011

1 August 2002 Hard pellicle study for 157-nm lithography

Emily Y. Shu, Fu-Chang Lo, Florence O. Eschbach, Eric P. Cotte, Roxann L. Engelstad, Edward G. Lovell, Kaname Okada, Shinya Kikugawa

Author Affiliations +

Proceedings Volume 4754, Photomask and Next-Generation Lithography Mask Technology IX; (2002) https://doi.org/10.1117/12.477011
Event: Photomask and Next Generation Lithography Mask Technology IX, 2002, Yokohama, Japan

Abstract

Identifying a functional pellicle solution for 157-nm lithography remains the most critical issue for mask technology. Developing a hard pellicle system has been a recent focus of study. Fabrication and potential pellicle-induced image placement errors present the highest challenges to the technology for meeting the stringent error budget for manufacturing devices in the 65-nm regime. This paper reports the results of a comprehensive proof-of-concept study on the state-of-art hard pellicle systems, which feature 800-mm thick modified fused silica pellicles and quartz frames. Pellicles were fabricated to ensure optical uniformity and flatness. Typical intrinsic warpage of these pellicles was close to the theoretical limit of 4.0 mm under a gravitational load. Quartz frames had bows less than 1.0 mm. The advantage of quartz frames with matched thermal expansion was demonstrated. An interferometric facility was developed to measure the flatness of the mask and pellicle system before and after pellicle mounting. Depending on the mounting process as well as mounting tool characteristics and techniques, variations were observed from pellicle to pellicle, mount to mount, and mask to mask. A redesign of the mounter and mounting process has significantly improved pellicle flatness. Finite element models were also generated to characterize the relative importance of the principal sources of pellicle-induced photomask distortions. Simulation results provide insightful guidance for improving image quality when employing a hard pellicle.

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Emily Y. Shu, Fu-Chang Lo, Florence O. Eschbach, Eric P. Cotte, Roxann L. Engelstad, Edward G. Lovell, Kaname Okada, and Shinya Kikugawa "Hard pellicle study for 157-nm lithography", Proc. SPIE 4754, Photomask and Next-Generation Lithography Mask Technology IX, (1 August 2002); https://doi.org/10.1117/12.477011

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