Full field wavefront error aware source and mask optimization for extreme ultraviolet lithography

Abstract

Source and mask optimization (SMO) should be applied in extreme ultraviolet lithography (EUVL) for 7-3 nm technology node. Ineluctable wavefront error (WFE) coming from projection optics or 3D mask effect is considered as a single field point effect instead of full field aware in traditional SMO flow. For getting more qualified SMO, a model of full-field wavefront error aware source and mask optimization (FFSMO) is invented. This method focuses on the tradeoff of lithographic imaging at different typical field point as a multi-objective problem. A new multi-objective cost function is established to improve the uniformity of pattern fidelity at different field point. Simulation results show that the proposed FFSMO method has better imaging uniformity at different field points than non-wavefront error aware SMO (SMO-Ideal) or single field point aware SMO (SMO-F2). For line and space pattern at 7nm node, the standard deviation of pattern error (PAE) reduced from 185.0 to 79.2 comparing with the single field point aware SMO. It is demonstrated that the effectiveness of this FFSMO model in terms of balancing and improving imaging uniformity and PW across full exposure field. For contact hole pattern, the standard deviation of pattern error (PAE) reduced from 233.7 to 75.6 comparing with the single field point aware SMO.