Abstract
Proximity effect is one of the most tremendous consequences that produces unacceptable exposures during electron beam lithography (EBL), and thus distorting the layout pattern. In this paper, we propose the first work which considers the proximity effect during layout stage. We first give an accurate evaluation scheme to estimate the proximity effect by fast Gauss transform. Then, we devote a proximity effect aware detailed placement objective function to simultaneously consider wirelength, density and proximity effect. Furthermore, cell swapping and cell matching based methods are used to optimize the objective function such that there is no overlap among cells. Compared with a state-of-the-art work, experimental result shows that our algorithm can efficiently reduce the proximity variations and maintain high wirelength quality at a reasonable runtime.
Highlights
As the feature sizes keep shrinking, the complexity of a circuit design increases dramatically
We present proximity aware cell swapping and cell matching technologies, which can make a good tradeoff between minimizing proximity variation and wirelength
Based on NTUplace4dr [5], we implemented our algorithm for proximity effect aware detailed placement in the C++ programming language, and tested it on the benchmarks provided by the authors[6].These benchmarks were obtained by modifying the 2015 ISPD Blockage-Aware Detailed Routing-Driven Placement Contest [1], where the fence-region constraints were removed
Summary
As the feature sizes keep shrinking, the complexity of a circuit design increases dramatically. When a primary electron beam emitted from the electron gun and hits the resist and substrate, the electrons may scattered and the scattered electrons produce backscattered electrons. The electrons scattered within the resist and from the substrate cause inaccurate exposure of the resist in regions adjacent to those addressed by the electron beam. We consider the EBL proximity effect during layout stage. During the detailed placement stage, we propose an algorithm to optimize the wirelength, displacement, and proximity variation simultaneously. Compared with a state-of-the-art work, our algorithm can achieve 6.6% lower proximity variation.
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