Optimization of Dipole Off-Axis Illumination by 1st-Order Efficiency Method for Sub-120 nm Node with KrF Lithography

Abstract

To extend the limitation of KrF lithography into the 110 nm design rule region, dipole off-axis illumination (OAI) is suggested. We have investigated the availability of the 1st-order efficiency as a method of optimization and confirmed it in the conventional OAI. By the 1st-order-efficiency method, we have designed two dipole apertures that are capable of resolving horizontal and vertical dense patterns, and have evaluated the basic performance of the modified dipole apertures. To verify the applicability of the modified dipole apertures to memory devices, we tested a variety of patterns and obtained fine patterns with the help of optical proximity correction (OPC). In this study, we found that the optimized dipole OAI can serve as an extension method of KrF lithography for 110 nm devices.