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Proceedings Paper

An improved virtual aberration model to simulate mask 3D and resist effects
Author(s): Reiji Kanaya; Koichi Fujii; Motokatsu Imai; Tomoyuki Matsuyama; Takao Tsuzuki; Qun Ying Lin
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Paper Abstract

As shrinkage of design features progresses, the difference in best focus positions among different patterns is becoming a fatal issue, especially when many patterns co-exist in a layer. The problem arises from three major factors: aberrations of projection optics, mask 3D topography effects, and resist thickness effects. Aberrations in projection optics have already been thoroughly investigated, but mask 3D topography effects and resist thickness effects are still under study. It is well known that mask 3D topography effects can be simulated by various Electro-magnetic Field (EMF) analysis methods. However, it is almost impossible to use them for full chip modeling because all of these methods are extremely computationally intensive. Consequently, they usually apply only to a limited range of mask patterns which are about tens of square micro meters in area. Resist thickness effects on best focus positions are rarely treated as a topic of lithography investigations. Resist 3D effects are treated mostly for resist profile prediction, which also requires an intensive EMF analysis when one needs to predict it accurately. In this paper, we present a simplified Virtual Aberration (VA) model to simulate both mask 3D induced effects and resist thickness effects. A conventional simulator, when applied with this simplified method, can factor in both mask 3D topography effects and resist thickness effects. Thus it can be used to model inter-pattern Best Focus Difference (BFD) issues with the least amount of rigorous EMF analysis.

Paper Details

Date Published: 18 March 2015
PDF: 9 pages
Proc. SPIE 9426, Optical Microlithography XXVIII, 94261O (18 March 2015); doi: 10.1117/12.2085606
Show Author Affiliations
Reiji Kanaya, Nikon Corp. (Japan)
Koichi Fujii, Nikon Corp. (Japan)
Motokatsu Imai, Nikon Corp. (Japan)
Tomoyuki Matsuyama, Nikon Corp. (Japan)
Takao Tsuzuki, Nikon Corp. (Japan)
Qun Ying Lin, Institute of Mircoelectronics (Singapore)

Published in SPIE Proceedings Vol. 9426:
Optical Microlithography XXVIII
Kafai Lai; Andreas Erdmann, Editor(s)

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