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As nanometer technology advances, conventional OPC (Optical Proximity Correction) that minimizes the EPE (Edge Placement Error) at the nominal corner alone often leads to poor process window. To improve the mask printability across various process corners, process-window OPC optimizes EPE for multiple process corners, but often suffers long runtime, due to repeated lithographic simulations. This paper presents an efficient process-variation-aware mask optimization framework, namely PVOPC (Process-Variation OPC), to simultaneously minimize EPE and PV (Process-Variation) band with fast convergence. The PVOPC framework includes EPE-sensitivity-driven dynamic fragmentation, process-variation-aware EPE modeling, and post correction with three new EPE-converging techniques and a systematic sub-resolution assisted feature insertion algorithm. Experimental results show that our approach efficiently achieves high-quality EPE and PV band results.

Abstract. We consider the broadcasting problem in heterogeneous tree networks. A heterogeneous tree network is represented by a weighted tree T = (V, E) such that the weight of each edge denotes the communication time between the two end vertices. The broadcasting problem is to find a broadcast center such that the maximum communication time from the broadcast center to all vertices is minimized. In this paper, we propose a linear time algorithm for the broadcasting problem in a heterogeneous tree network following the postal model. As a byproduct of the algorithm, we can compute in linear time the broadcasting time of any vertex in the tree, i.e., the maximum time required to transmit messages from the vertex to every other vertex in the tree. Furthermore, an optimal sequence by which the broadcast center broadcasts its messages to all vertices in T can also be determined in linear time.

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