Extreme Ultraviolet Mask Defect Observation Using an Extreme Ultraviolet Microscope

To predict the effect of a phase defect position relative to the absorber pattern on a wafer printed image, a programmed phase defect mask was fabricated, and was observed using an extreme ultraviolet (EUV) microscope employing EUV light from a beam line BL3 of the New SUBARU at the University of Hyogo. The mask prepared for this work contains programmed phase defects along with half-pitch (hp) 64 nm lines-and-spaces (L/S) absorber patterns. The phase defects were located at different locations in reference to the absorber lines. A lithography simulator predicted that when the distance between the line center and defect center range from 26 to 102 nm, the prepared 1.8 nm-high and 57.4 nm-wide phase defects would cause errors of more than 10 % in wafer printed critical dimension (CD). The EUV microscope could identify these phase defects with the EUV light intensity losses of more than 17 % in comparison to the space pattern image intensity in the absence of the phase defect. The EUV microscope can predict the existence of the phase defect, and its impact on a wafer printed CD even where the EUV microscope does not completely emulate the image of the EUV scanner.