Characterization of Defect Detection Sensitivity in Inspection of Mask Substrates and Blanks for Extreme Ultraviolet Lithography

摘要

Defect detection sensitivity of a multi-beam confocal inspection system operating at a wavelength of 488 nm is characterized using experiments and image modeling. Experimental data on defect sensitivity are reported for programmed defects on mask substrates and blanks that are being developed for extreme ultraviolet lithography. The effects of sample surface roughness on the detection sensitivity and signal-to-noise levels are quantified. Theoretical analysis of confocal imaging of defects is in excellent agreement with measured defect images. Modeling is used to predict inspection sensitivity for defects commonly found on mask blanks.