Image contrast contributions to immersion lithography defect formation and process yield

Abstract

As the industry extends immersion lithography to the 32 nm node, the limits of image and resist contrast will be challenged. Image contrast is limited by the inherent numerical aperture of a water based immersion lithography system. Elements of resist design and processing can further degrade the final deprotected image contrast^1,2. Studies have been done to understand the effects of image contrast on line width roughness (LER) for dry 193 nm lithography³. This paper focuses on the impacts of image and resist contrast on the formation of defects and LER in an immersion lithography process. Optical and resist simulations are combined with experiments to better understand the relationship between image quality, resist design, scanner/track processing and defect formation. The goal of this work is to develop a relationship between resist contrast metrics and defect formation for immersion processes.