Tip-to-tip variation mitigation in extreme ultraviolet lithography for 7 nm and beyond metallization layers and design rule analysis

Abstract

The authors develop and present computational lithography solutions to mitigate the tip-to-tip variations in 7 nm and beyond metallization layers. An array of patterns that represent lithography challenges are generated from basic design rules. The lithography process is optimized by source mask co-optimization to achieve high image qualities and maximum overlapping process windows for all patterns. By analyzing the role of diffraction orders in forming images with tight tip-to-tip, the authors identify the diffraction orders that should be admitted or rejected in the projection imaging system. This leads to analytically derived source profiles that match and explain numerical results. The authors have also found optimal minimum pitches that can achieve robust lithography process as well as design flexibility without losing throughput. Our work provides design for manufacturability guidance to metallization layers in advanced technology nodes so that patterning failures can be avoided before time-consuming optical rule check and expensive wafer validation.