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Proceedings Paper

Exploration of fabrication techniques for phase-shifting masks
Author(s): Anton K. Pfau; William G. Oldham; Andrew R. Neureuther
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Paper Abstract

Techniques for fabrication and testing of phase-shifting masks have been explored. The masks were formed using quartz blanks with both directly etched-in phase-shifters as well as deposited SiO2 films and photoresist for the phase-shifting layer. The etched-in phase- shifters were fabricated by standard lithographic patterning and dry etching of the quartz mask surface. Phase-shifters consisting of photoresist were applied and important resist properties such as index of refraction and absorption were determined. A technique for precise control of the etched phase step using a self-terminated plasma etch into CVD SiO2 has also been explored. Printed patterns using the masks showed the expected benefits of phase-shifting. We also investigated the effect of fabrication tolerances. For example, misalignment of the auxiliary phase-shifters surrounding a contact hole has little impact on printed resist patterns. Phase-shifter parameters deviating from the optimum value were explored both experimentally and using the optical simulator SPLAT. Sloping side walls as well as absorption and interference in the phase-shifter show varying influence depending on the specific feature and the lens reduction. The tolerance in phase-shift magnitude has been examined in a number of cases, and is generally found to be in the neighborhood of 30 degree(s).

Paper Details

Date Published: 1 July 1991
PDF: 11 pages
Proc. SPIE 1463, Optical/Laser Microlithography IV, (1 July 1991); doi: 10.1117/12.44778
Show Author Affiliations
Anton K. Pfau, Univ. of California/Berkeley (United States)
William G. Oldham, Univ. of California/Berkeley (United States)
Andrew R. Neureuther, Univ. of California/Berkeley (United States)

Published in SPIE Proceedings Vol. 1463:
Optical/Laser Microlithography IV
Victor Pol, Editor(s)

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