Feedback control applied to improve convergence of performance-based optical proximity correction in advanced lithography

Abstract

The continuous shrinking of VLSI critical dimensions (CD) has led to increasing difficulties in nano-scale fabrication to transfer mask pattern onto silicon wafers. Optical proximity correction (OPC) is introduced to improve print image fidelity. Conventional OPC aims at minimizing edge placement error (EPE), without considerations of post-lithography circuit performances. We have previously proposed a performance-based OPC (PB-OPC) methodology which focuses on the circuit performance. This novel method reduces mask size significantly with little loss in timing accuracy. However one limitation of our approach is the computational time used in generating the required mask. In this paper, we make use of ideas from feedback control to improve on the convergence speed of generating the OPC mask.