Resolution Enhancement Techniques (RET) for Immersion Lithography

Abstract

Optical lithography has been critical in enabling the progressive miniaturization of semiconductor devices. Immersion lithography has extended the life time of 193 nm lithography while the industry is facing delays in next generation lithography technology. The main objective of this work is to achieve resolution enhancement for immersion lithography. The study is primarily dealing with the interaction of mask defects on wafer imaging, solving forbidden pitch issues in application of off-axis illumination (OAI), and handling contact holes patterning challenges. Thorough understanding of mask defects and their influence on imaging are necessary in controlling process variations and implementing systematic defects disposition. Moreover, modifications of conventional OAI through studying effects of diffraction order overlapping achieved improved uniformity in wafer linewidth through pitch performance; forbidden pitch issues are addressed and mitigated. Furthermore, new approach in designing segmentation for contact holes improves contact holes patterning and process robustness.