EUV Resists: Pushing to the Extreme

Despite achieving 15-nm half pitch, the progress in extreme ultraviolet chemically amplified resist has arguably decelerated in recent years. We show that this deceleration is consistent with approaching stochastic limits both in photon counts and material parameters. Contact hole printing is a crucial application for extreme ultraviolet lithography and is particularly challenged by resist sensitivity due to inherent inefficiencies in darkfield contact printing. Checkerboard strong phase shift masks have the potential to alleviate this problem through a 4x increase in optical efficiency. The feasibility of this method is demonstrated using the SEMATECH-Berkeley Microfield Exposure Tool pseudo phase shift mask configuration and preliminary results are provided on the fabrication of an etched multilayer checkerboard phase shift mask.