Dependence of defect size and shape on detectability for EUV patterned mask inspection

Abstract

Defect detectability using electron beam (EB) inspection for extreme ultraviolet (EUV) mask was investigated by comparing a projection electron microscope (PEM) and a scanning electron microscope (SEM) inspection system. The detectability with EB does not coincide with the printability data because the contrasts of EUV aerial image and EB image for EUV mask are reversed. The detectability for 16 nm sized defect on a half pitch 64 nm line and space pattern is acceptable under 2-nm-line edge roughness (LER) (3 sigma) in both PEM and SEM inspections by applying a special algorithm for image processing. The required and robust inspection conditions such as the number of electrons per pixel and pixel size (resolution) are examined for SEM inspection system. Throughput of a PEM inspection system corresponds to that of a multi-beam SEM one with 250 – 1000 beams.