Phase imaging results of phase defect using micro coherent EUV scatterometry microscope

Abstract

To evaluate defects on extreme ultraviolet (EUV) masks at the blank state of manufacturing, we developed a micro coherent EUV scatterometry microscope (micro-CSM). The illumination source is coherent EUV light with a 140-nm focus diameter on the defect using a Fresnel zoneplate. This system directly observes the reflection and diffraction signals from a phase defect. The phase and the intensity image of the defect is reconstructed with the diffraction images using ptychography, which is an algorithm of the coherent diffraction imaging. We observed programmed phase defect on a blank EUV mask. Phase distributions of these programmed defect were well reconstructed quantitatively. The micro-CSM is very powerful tool to review an EUV phase defect.