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Proceedings Paper

Pattern-dependent correction of mask topography effects for alternating phase-shifting masks
Author(s): Richard A. Ferguson; Alfred K. K. Wong; Timothy A. Brunner; Lars W. Liebmann
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Paper Abstract

Strategies for modifying both mask fabrication processes and design data for alternating phase-shifting masks to account for mask scattering phenomena are explored. Results were derived from the rigorous solution of Maxwell's equations using the EMFlex and TEMPEST programs for an etched-quartz fabrications process. By importing the resulting diffracted orders into VCIMAGE, full vector calculation of the aerial image from mask to wafer was obtained. From the rigorous mask simulations, the 0th and 1st diffracted orders were translated into an effective transmission and phase based on a thin-mask approximation. With this analysis technique, a 0.25 micrometers line-space grating for the baseline etched-quartz process (4X magnification) showed a transmission error of 7.2% and a phase error of 1.6 degree(s). In order to compensate for these errors, etch-back fabrication techniques, in which the quartz was recessed beneath the chrome, were evaluated to determine the extent to which the transmission and phase errors could be reduced. For the dual etch-back process typically in use today, a residual transmission error of approximately 0.5% could not be completely removed, even for etch-back depths greater than 200 nm. Correction of the phase errors was achieved by reducing the reactive-ion etch depth by 2-3 nm. Design manipulation, in which the 180 degree(s) opening was increased in size, required feature-dependent phase errors as large as 1 degree(s) were present.

Paper Details

Date Published: 26 May 1995
PDF: 12 pages
Proc. SPIE 2440, Optical/Laser Microlithography VIII, (26 May 1995); doi: 10.1117/12.209267
Show Author Affiliations
Richard A. Ferguson, IBM Microelectronics (United States)
Alfred K. K. Wong, Univ. of California/Berkeley (Hong Kong)
Timothy A. Brunner, IBM Microelectronics (United States)
Lars W. Liebmann, IBM Microelectronics (United States)

Published in SPIE Proceedings Vol. 2440:
Optical/Laser Microlithography VIII
Timothy A. Brunner, Editor(s)

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