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Optical Engineering

Simulation of the polarization effects induced by the bilayer absorber alternating phase-shift mask in conical diffraction
Author(s): Liang Yang; Yanqiu Li; Ke Liu
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Paper Abstract

Hyper numerical aperture (NA) and off-axis illumination enable extension of ArF lithography for 45 nm technology node and beyond. Also, rigorous electromagnetic field modeling is taken into account for the optical and topographical properties of the mask. A rigorous three-dimensional mask model for bilayer absorber alternating phase shift mask (AltPSM) with the rigorous coupled-wave analysis (RCWA) is established. First, the harmonic waves are expanded based on the least common multiple of the periods in order to model the diffraction of multiple grating layers with different periods. Second, Lalanne’s formulation is used to improve the convergence of RCWA for multiple grating layers in conical diffraction. Third, the enhanced transmittance matrix approach is also extended to conical diffraction to avoid the numerical instability. Given the chromium oxide/chromium AltPSM, the change of polarization state as a function of mask and incident light properties is investigated. When the linewidth is below 30 nm, the mask acts as a transverse magnetic field polarizer, which is not preferred in terms of image quality, so the mask-induced polarization effects must be considered in the hyper NA lithography.

Paper Details

Date Published: 7 March 2013
PDF: 8 pages
Opt. Eng. 52(9) 091702 doi: 10.1117/1.OE.52.9.091702
Published in: Optical Engineering Volume 52, Issue 9
Show Author Affiliations
Liang Yang, Beijing Institute of Technology (China)
Yanqiu Li, Beijing Institute of Technology (China)
Ke Liu, Beijing Institute of Technology (China)

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