Exploration of fabrication techniques for phase-shifting masks

Anton K. Pfau; William G. Oldham; Andrew R. Neureuther

doi:10.1117/12.44778

1 July 1991 Exploration of fabrication techniques for phase-shifting masks

Anton K. Pfau, William G. Oldham, Andrew R. Neureuther

Proceedings Volume 1463, Optical/Laser Microlithography IV; (1991) https://doi.org/10.1117/12.44778
Event: Microlithography, 1991, San Jose, CA, United States

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).

Citation Download Citation

Anton K. Pfau, William G. Oldham, and Andrew R. Neureuther "Exploration of fabrication techniques for phase-shifting masks", Proc. SPIE 1463, Optical/Laser Microlithography IV, (1 July 1991); https://doi.org/10.1117/12.44778

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