Advanced lithography: wafer defect scattering analysis at DUV

Considerable effort is directed towards the development of next-generation lithography processes, addressing the need for transistor densification to meet Moore's Law. The aggressive design rule shrinkage requires very tight process windows and induces various types of pattern failure with lithography process variations. Since the lithography process is critical in the wafer fabrication process, the requirements for high sensitivity defect detection in the lithography process becomes tighter as design rules shrink. Analysis of the root cause of the defects and of their interaction with various light sources and optics systems configurations for wafer inspection is essential for understanding the detection limits and requirements from advanced inspection systems targeting future lithography inspection applications. In this work, we present an analysis of wafer defects light scattering and detection for a variety of 3xnm design rule resist structures with various polarizations and optics configurations, at the visible, at UV and at DUV wavelengths. The analysis indicates on the defect scattering and inspection performance trends for a variety of resist structures and defect types, and shows that control of the polarization of the optical inspection system is critical for enhanced scattering and detection sensitivity. The analysis is performed also for the 2xnm and 1xnm design rules showing the advantages of polarized DUV illumination over unpolarized and visible illumination.