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Proceedings Paper

Precision process calibration and CD predictions for low-k1 lithography
Author(s): Ting Chen; Sangbong Park; Gabriel Berger; Tamer H. Coskun; Joep de Vocht; Fung Chen; Linda Yu; Stephen Hsu; Doug van den Broeke; Robert Socha; Jungchul Park; Keith Gronlund; Todd Davis; Vince Plachecki; Tom Harris; Steve Hansen; Chuck Lambson
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Paper Abstract

Leading resist calibration for sub-0.3 k1 lithography demands accuracy <2nm for CD through pitch. An accurately calibrated resist process is the prerequisite for establishing production-worthy manufacturing under extreme low k1. From an integrated imaging point of view, the following key components must be simultaneously considered during the calibration - high numerical aperture (NA>0.8) imaging characteristics, customized illuminations (measured vs. modeled pupil profiles), resolution enhancement technology (RET) mask with OPC, reticle metrology, and resist thin film substrate. For imaging at NA approaching unity, polarized illumination can impact significantly the contrast formation in the resist film stack, and therefore it is an important factor to consider in the CD-based resist calibration. For aggressive DRAM memory core designs at k1<0.3, pattern-specific illumination optimization has proven to be critical for achieving the required imaging performance. Various optimization techniques from source profile optimization with fixed mask design to the combined source and mask optimization have been considered for customer designs and available imaging capabilities. For successful low-k1 process development, verification of the optimization results can only be made with a sufficiently tunable resist model that can predicate the wafer printing accurately under various optimized process settings. We have developed, for resist patterning under aggressive low-k1 conditions, a novel 3D diffusion model equipped with double-Gaussian convolution in each dimension. Resist calibration with the new diffusion model has demonstrated a fitness and CD predication accuracy that rival or outperform the traditional 3D physical resist models. In this work, we describe our empirical approach to achieving the nm-scale precision for advanced lithography process calibrations, using either measured 1D CD through-pitch or 2D memory core patterns. We show that for ArF imaging, the current resist development and diffusion modeling can readily achieve ~1-2nm max CD errors for common 1D through-pitch and aggressive 2D memory core resist patterns. Sensitivities of the calibrated models to various process parameters are analyzed, including the comparison between the measured and modeled (Gaussian or GRAIL) pupil profiles. We also report our preliminary calibration results under selected polarized illumination conditions.

Paper Details

Date Published: 28 June 2005
PDF: 15 pages
Proc. SPIE 5853, Photomask and Next-Generation Lithography Mask Technology XII, (28 June 2005); doi: 10.1117/12.617218
Show Author Affiliations
Ting Chen, ASML MaskTools (United States)
Sangbong Park, ASML MaskTools (United States)
Gabriel Berger, ASML MaskTools (United States)
Tamer H. Coskun, ASML MaskTools (United States)
Joep de Vocht, ASML MaskTools (United States)
Fung Chen, ASML MaskTools (United States)
Linda Yu, ASML MaskTools (United States)
Stephen Hsu, ASML MaskTools (United States)
Doug van den Broeke, ASML MaskTools (United States)
Robert Socha, ASML TDC (United States)
Jungchul Park, ASML MaskTools (United States)
Keith Gronlund, ASML MaskTools (United States)
Todd Davis, ASML (United States)
Vince Plachecki, ASML (United States)
Tom Harris, ASML (United States)
Steve Hansen, ASML TDC (United States)
Chuck Lambson, ASML (United States)

Published in SPIE Proceedings Vol. 5853:
Photomask and Next-Generation Lithography Mask Technology XII
Masanori Komuro, Editor(s)

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