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Proceedings Paper

Modeling and optimization of mass-limited targets for EUV lithography
Author(s): T. Sizyuk; A. Hassanein
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Paper Abstract

Current challenges in the development of efficient laser produced plasma (LPP) sources for EUV lithography are increasing EUV power at IF and maximizing lifetime and therefore, reducing cost of devices. Mass-limited targets such as small tin droplets are considered among the best choices for cleaner operation of the optical system because of lower mass of atomic debris produced by the laser beam. The small diameter of droplets, however, decreases the conversion efficiency (CE) of EUV photons emission, especially in the case of CO2 laser, where laser wavelength has high reflectivity from the tin surface. We investigated ways of improving CE in mass-limited targets. We considered in our modeling various possible target phases and lasers configurations: from solid/liquid droplets subjected to laser beam energy with different intensities and laser wavelength to dual-beam lasers, i.e., a pre-pulse followed by a main pulse with adjusted delay time in between. We studied the dependence of vapor expansion rate, which can be produced as a result of droplet heating by pre-pulse laser energy, on target configuration, size, and laser beam parameters. As consequence, we studied the influence of these conditions and parameters on the CE and debris mass accumulation. For better understanding and more accurate modeling of all physical processes occurred during various phases of laser beam/target interactions, plasma plume formation and evolution, EUV photons emission and collection, we have implemented in our HEIGHTS package state-of-the art models and methods, verified, and benchmarked against laboratory experiments in our CMUXE center as well as various worldwide experimental results.

Paper Details

Date Published: 23 March 2012
PDF: 6 pages
Proc. SPIE 8322, Extreme Ultraviolet (EUV) Lithography III, 83222K (23 March 2012); doi: 10.1117/12.916432
Show Author Affiliations
T. Sizyuk, Purdue Univ. (United States)
A. Hassanein, Purdue Univ. (United States)

Published in SPIE Proceedings Vol. 8322:
Extreme Ultraviolet (EUV) Lithography III
Patrick P. Naulleau; Obert R. Wood, Editor(s)

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