Subresolution assist feature and off-axis illumination optimization for 200- and 240-nm contact windows using 248-nm lithography

Pat G. Watson; Raymond A. Cirelli; Allen G. Timko; Omkaram Nalamasu; Carl Lockstamphor; Steven D. Berger; Neil J. Bassom; Ganesh Sundaram

doi:10.1117/12.310743

29 June 1998 Subresolution assist feature and off-axis illumination optimization for 200- and 240-nm contact windows using 248-nm lithography

Pat G. Watson, Raymond A. Cirelli, Allen G. Timko, Omkaram Nalamasu, Carl Lockstamphor, Steven D. Berger, Neil J. Bassom, Ganesh Sundaram

Author Affiliations +

Proceedings Volume 3334, Optical Microlithography XI; (1998) https://doi.org/10.1117/12.310743
Event: 23rd Annual International Symposium on Microlithography, 1998, Santa Clara, CA, United States

Abstract

Sub-resolution assist features, coupled with appropriate off- axis illumination conditions, have been studied with the goal of fabricating 200 and 240 nm contact windows with uniform critical dimensions over a range of pitches and with large depths of focus (DOF). Results show that 240 nm isolated contacts without assist features possessed a useful DOF of less than 0.4 microns. The same features with 140 nm assist slots on each window edge, located 190 nm away, possessed a DOF of over 0.8 microns, using quadrupole illumination. Soft quadrupole illumination, where a mixture of quadrupole and conventional illumination is employed, yielded nearly the same DOF as quadrupole and printed both semi-dense and isolated contact windows near their optimum size as well. Contact holes, 200 nm wide, have been printed with smaller sub- resolution features, soft quadrupole illumination, and higher performance resists with a DOF of over 0.6 microns using a stepper with a numerical aperture of 0.53.

Citation Download Citation

Pat G. Watson, Raymond A. Cirelli, Allen G. Timko, Omkaram Nalamasu, Carl Lockstamphor, Steven D. Berger, Neil J. Bassom, and Ganesh Sundaram "Subresolution assist feature and off-axis illumination optimization for 200- and 240-nm contact windows using 248-nm lithography", Proc. SPIE 3334, Optical Microlithography XI, (29 June 1998); https://doi.org/10.1117/12.310743

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