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Proceedings Paper

Analysis of off-axis-shaped beam systems for high-throughput electron-beam lithography
Author(s): Xieqing Zhu; Haoning Liu; Eric Munro; John A. Rouse
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Paper Abstract

For high-throughput electron beam lithography, projection systems using symmetric magnetic doublet lenses can produce images with zero distortion. However, the projected pattern area is limited by beam blur at large off-axis distances. If an off-axis shaped beam pattern is imaged in a projection system, the aberrations can be greatly reduced by introducing deflectors, which steer the beam through the projection lenses in a modified path. In this paper, the principle of this type of projection with in-lens deflectors is first outlined. The method for computing the optical properties of such systems, based on an extension of our previously published unified aberration theory, is then described. To provide accurate simulation of systems with such large field sizes, our new software computes both the third and fifth-order aberrations. The computation of dynamic corrections, which can not only correct deflection field curvature and astigmatism but also reduce stitching errors, is also described. A design example of an off-axis shaped beam projection system with deflectors is presented, which has been optimized by the damped least squares method. The results show that such systems can have extremely small beam blur, distortion and stitching errors. The presented design images a 0.25 mm square shot over a 3 mm square region of the wafer, with 2 mrad beam half-angle, with a beam blur less than 26 nm, and distortions and stitching errors less than 19 nm.

Paper Details

Date Published: 25 September 1997
PDF: 15 pages
Proc. SPIE 3155, Charged Particle Optics III, (25 September 1997); doi: 10.1117/12.287818
Show Author Affiliations
Xieqing Zhu, Munro's Electron Beam Software Ltd. (United Kingdom)
Haoning Liu, Munro's Electron Beam Software Ltd. (United Kingdom)
Eric Munro, Munro's Electron Beam Software Ltd. (United Kingdom)
John A. Rouse, Munro's Electron Beam Software Ltd. (United Kingdom)

Published in SPIE Proceedings Vol. 3155:
Charged Particle Optics III
Eric Munro, Editor(s)

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