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Proceedings Paper

Improved diffraction computation with a hybrid C-RCWA-method
Author(s): Joerg Bischoff
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Paper Abstract

The Rigorous Coupled Wave Approach (RCWA) is acknowledged as a well established diffraction simulation method in electro-magnetic computing. Its two most essential applications in the semiconductor industry are in optical scatterometry and optical lithography simulation. In scatterometry, it is the standard technique to simulate spectra or diffraction responses for gratings to be characterized. In optical lithography simulation, it is an effective alternative to supplement or even to replace the FDTD for the calculation of light diffraction from thick masks as well as from wafer topographies. Unfortunately, the RCWA shows some serious disadvantages particularly for the modelling of grating profiles with shallow slopes and multilayer stacks with many layers such as extreme UV masks with large number of quarter wave layers. Here, the slicing may become a nightmare and also the computation costs may increase dramatically. Moreover, the accuracy is suffering due to the inadequate staircase approximation of the slicing in conjunction with the boundary conditions in TM polarization. On the other hand, the Chandezon Method (C-Method) solves all these problems in a very elegant way, however, it fails for binary patterns or gratings with very steep profiles where the RCWA works excellent. Therefore, we suggest a combination of both methods as plug-ins in the same scattering matrix coupling frame. The improved performance and the advantages of this hybrid C-RCWA-Method over the individual methods is shown with some relevant examples.

Paper Details

Date Published: 23 March 2009
PDF: 12 pages
Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72723Y (23 March 2009);
Show Author Affiliations
Joerg Bischoff, Timbre Technologies, Inc. (United States)
Tokyo Electron Germany GmbH (Germany)

Published in SPIE Proceedings Vol. 7272:
Metrology, Inspection, and Process Control for Microlithography XXIII
John A. Allgair; Christopher J. Raymond, Editor(s)

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