Feasibility study of EUV patterned mask inspection for the 22nm node

Extreme Ultra Violet Lithography (EUVL) is a major patterning solution candidate being considered for the ITRS (International Technology Roadmap for Semiconductors) advanced technology nodes commencing with the 22nm Half Pitch (HP) nodes. Achieving defect free EUVL masks is a critical issue in the wafer manufacturing process and thus the importance for mask inspection technology to be ready to support pilot line development. EUV mask inspection presents additional challenges with smaller line width, multilayer defects and no pellicle to protect the mask. In addition, Line Edge Roughness on the mask can limit the detection sensitivity. Configurable inspection illumination conditions were considered to enhance the contrast of the mask image and improve the detection sensitivity. Here we present experimental results of evaluating the defects detecting capability on several EUVL masks of different technology nodes. EUVL mask inspections were done using Material's Aera3 TM DUV (193nm) reflected illumination optical inspection system employing configurable inspection illumination conditions and magnifications.