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Proceedings Paper

Freeform illumination sources: an experimental study of source-mask optimization for 22-nm SRAM cells
Author(s): J. Bekaert; B. Laenens; S. Verhaegen; L. Van Look; D. Trivkovic; F. Lazzarino; G. Vandenberghe; P. van Adrichem; R. Socha; S. Baron; M. C. Tsai; K. Ning; S. Hsu; H. Y. Liu; M. Mulder; A. Bouma; E. van der Heijden; O. Mouraille; K. Schreel; J. Finders; M. Dusa; J. Zimmermann; P. Gräupner; J. T. Neumann; C. Hennerkes
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Paper Abstract

The use of customized illumination modes is part of the pursuit to stretch the applicability of immersion ArF lithography. Indeed, a specific illumination source shape that is optimized for a particular design leads to enhanced imaging results. Recently, freeform illumination has become available through pixelated DOEs or through FlexRayTM, ASML's programmable illuminator system, allowing for virtually unconstrained intensity distribution within the source pupil. In this paper, the benefit of freeform over traditional illumination is evaluated, by applying source mask co-optimization (SMO) for an aggressive use case, and wafer-based verification. For a 22 nm node SRAM of 0.099 μm² and 0.078 μm2 bit cell area, the patterning of the full contact and metal layer into a hard mask is demonstrated with the application of SMO and freeform illumination. In this work, both pixelated DOEs and FlexRay are applied. Additionally, the match between the latter two is confirmed on wafer, in terms of CD and process window.

Paper Details

Date Published: 3 March 2010
PDF: 12 pages
Proc. SPIE 7640, Optical Microlithography XXIII, 764008 (3 March 2010); doi: 10.1117/12.846918
Show Author Affiliations
J. Bekaert, IMEC vzw (Belgium)
B. Laenens, IMEC vzw (Belgium)
S. Verhaegen, IMEC vzw (Belgium)
L. Van Look, IMEC vzw (Belgium)
D. Trivkovic, IMEC vzw (Belgium)
F. Lazzarino, IMEC vzw (Belgium)
G. Vandenberghe, IMEC vzw (Belgium)
P. van Adrichem, ASML-BRION (United States)
ASML (Netherlands)
R. Socha, ASML-BRION (United States)
S. Baron, ASML-BRION (United States)
M. C. Tsai, ASML-BRION (United States)
K. Ning, ASML-BRION (United States)
S. Hsu, ASML-BRION (United States)
H. Y. Liu, ASML-BRION (United States)
M. Mulder, ASML (Netherlands)
A. Bouma, ASML (Netherlands)
E. van der Heijden, ASML (Netherlands)
O. Mouraille, ASML (Netherlands)
K. Schreel, ASML (Netherlands)
J. Finders, ASML (Netherlands)
M. Dusa, ASML (Netherlands)
J. Zimmermann, Carl Zeiss SMT AG (Germany)
P. Gräupner, Carl Zeiss SMT AG (Germany)
J. T. Neumann, Carl Zeiss SMT AG (Germany)
C. Hennerkes, Carl Zeiss SMT AG (Germany)

Published in SPIE Proceedings Vol. 7640:
Optical Microlithography XXIII
Mircea V. Dusa; Will Conley, Editor(s)

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