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Proceedings Paper

Contrast enhancement materials for yield improvement in submicron i-line lithography
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Paper Abstract

Contrast Enhancement Lithography has been in existence for almost two decades, yet its practical advantages are relatively unknown among the general lithography community. This paper attempts to redress this situation by discussing the implementation of a Contrast Enhancement Material into manufacturing. Contrast Enhancement Materials (CEMs) are photobleachable solutions applied as a thin top coat to the photoresist after softbake. The CEM is initially opaque at the actinic wavelength but becomes essentially transparent upon exposure. Optimising the relative bleaching parameters of the photoresist and the Contrast Enhancement Material makes it possible to prevent exposure in nominally unexposed resist regions, while bleaching the exposed resist areas. Thus, a temporary contact mask is formed on the photoresist during exposure, allowing high-intensity parts of the aerial image to pass through while eliminating low intensity regions. The resulting aerial image which exposes the photoresist has higher contrast than the original. This allows superior resist depth-of-focus, improves resist profile, increases exposure latitudes and reduces proximity effects among other benefits. Initially, this paper discusses the chemistry and physics of the CEM process. Next the authors look at the lithographic requirements for a final metal level on a sub-micron CMOS process. Analysis of the Depth-Of-Focus error budget indicated that the process would not be manufacturable without significantly increased DOF. The authors also present the results of the characterization of the CEM, including simulation work, with regard to the effect on primary lithography outputs such as depth-of-focus, resist sidewall and exposure latitude.

Paper Details

Date Published: 16 July 2002
PDF: 10 pages
Proc. SPIE 4689, Metrology, Inspection, and Process Control for Microlithography XVI, (16 July 2002); doi: 10.1117/12.473430
Show Author Affiliations
Shane Geary, Analog Devices BV (Ireland)
James Thompson, Analog Devices BV (Ireland)
Elliott Sean Capsuto, Shin-Etsu MicroSi, Inc. (United States)

Published in SPIE Proceedings Vol. 4689:
Metrology, Inspection, and Process Control for Microlithography XVI
Daniel J. C. Herr, Editor(s)

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