Influence of Defects on Top of the Absorber in Extreme Ultraviolet Lithography

Abstract

Extreme ultraviolet lithography (EUVL) is expected to be used in device manufacturing starting at 32 nm half pitch and possibly 22 nm half pitch. EUVL is an optical technology that uses a 13.5 nm wavelength of the light. A Mask defect is any unintended mask anomaly that prints or changes a printed image size by 10% or more. Thus, the influence of defects oil the mask and oil the wafer is becoming more and more important. An EUV mask must be free of small defects, requiring development of new inspection tools and low defect fabrication processes. An EUV mask mainly consists of a multilayer, a buffer, and ail absorber. Defects can be formed in my layer. In this research, we simulated the influence of a defect oil top of the mask absorber. First, we used defect materials with different refractive indexes. Second, we changed the defect size from 30 to 50 nm. For the influence of a defect oil a 50 run isolated line pattern and oil a line and space pattern, we employed the SOLID-EUV simulation tool. We found that the shadow effect had little influence oil the defect. There was no effect on the pattern if the defect size was under 42 run for a 50 nm pattern, but displacement was seen when a defect existed on top of the absorber.