A dual exposure method with an alternating phase shift mask has been proposed for using KrF laser lithography to fabricate 100 nm gate patterns for logic devices. Fine and uniform patterns can be formed and so this process is considered very advantageous in terms of the formation of gate for logic devices. Several factors determine the lithographic performance of the alternating phase shift mask: phase accuracy, amount of undercutting, quartz and chromium defects, and so on. It is thought that these factors need to be strictly controlled. We thus investigated the impact of errors in the fabrication of alternating phase shift masks to determine the quality required for the dual exposure method, focusing on three factors: phase accuracy, amount of undercutting, and defects. A phase error causes CD variation and lateral shift in the defocused condition. Unsuitable undercutting causes lateral shift at the best focus. Shifter and chromium defects cause CD variation and distortion of the gate patterns. Our experimental results showed that these factors do not need to be strictly controlled. We thus propose a fabrication process for alternating phase shift masks to be used in the dual exposure method. Keywords: Alternating phase shift mask, dual exposure, phase accuracy, undercutting, defect

Date Published: 22 January 2001
PDF: 10 pages
Proc. SPIE 4186, 20th Annual BACUS Symposium on Photomask Technology, (22 January 2001); doi: 10.1117/12.410719

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