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Proceedings Paper

Coupled eigenmode theory applied to thick mask modeling
Author(s): Gary Allen; Paul Davids
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Paper Abstract

Coupled eigenmode (CEM) theory is presented and applied to the 3D modeling of a line-space reticle. In this approach, the electric field inside a line-space reticle is described in terms of an orthogonal set of eigenmodes of Maxwell's equations. The diffraction of light by the reticle can then be expressed as a coherent sum of diffraction orders produced by each eigenmode independently. Fresnel transmission, overlap of eigenmodes with diffraction orders and propagation through the mask are shown to be the interactions that determine the complex amplitude of the diffraction orders produced by each mode. CEM is then applied to the cases of a binary mask and an att-PSM under dipole illumination. It is shown that the behavior of contrast with pitch and mask bias is primarily affected by the propagation loss of the eigenmodes, which increases for smaller trench widths. In the case of the binary mask, this attenuation causes one eigenmode to become dominant and the resultant image approaches the perfect imaging of a single eigenmode. In the case of att-PSM, this attenuation causes a detuning of the transmission and phase, and thus, the image contrast is degraded.

Paper Details

Date Published: 15 May 2007
PDF: 14 pages
Proc. SPIE 6607, Photomask and Next-Generation Lithography Mask Technology XIV, 660730 (15 May 2007); doi: 10.1117/12.729019
Show Author Affiliations
Gary Allen, Intel Corp. (United States)
Paul Davids, Intel Corp. (United States)

Published in SPIE Proceedings Vol. 6607:
Photomask and Next-Generation Lithography Mask Technology XIV
Hidehiro Watanabe, Editor(s)

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