Tolerance-based OPC and solution to MRC-constrained OPC

Model based optical proximity correction (MB-OPC) has been widely used in advanced lithography process today. However controlling the edge placement error (EPE) and critical dimension (CD) has become harder as the k1 process factor decreases and design complexity increases. Especially, for high-NA lithography using strong off-axis illumination (OAI), ringing effects on 2D layout makes CD control difficult. In addition, mask rule check (MRC) limits also prevent good OPC convergence where two segment edges are corrected towards each other to form a correction-conflicting scenario because traditional OPC only consider the impact of the current edge when calculating the edge movement. A more sophisticated OPC algorithm that considers the interaction between segments is necessary to find a solution that is both MRC and convergence compliant. This paper first analyzes the phenomenon of MRC-constrained OPC. Then two multiple segment correction techniques for tolerance-based OPC and MRC-constrained OPC are discussed. These correction techniques can be applied to selected areas with different lithographic specifications. The feasibility of these techniques is demonstrated by quantifying the EPE convergence through iterations and by comparing the simulated contour results.