According to an International Technology Roadmap for Semiconductors (ITRS-2012) update, the sensitivity requirement for an extreme ultraviolet (EUV) mask pattern inspection system is to be less than 18 nm for half pitch (hp) 16-nm node devices. The inspection sensitivity of extrusion and intrusion defects on hp 64-nm line-and-space patterned EUV mask were investigated using simulated projection electron microscope (PEM) images. The obtained defect images showed that the optimization of current density and image processing techniques were essential for the detection of defects. Extrusion and intrusion defects 16 nm in size were detected on images formed by 3000 electrons per pixel. The landing energy also greatly influenced the defect detection efficiency. These influences were different for extrusion and intrusion defects. These results were in good agreement with experimentally obtained yield curves of the mask materials and the elevation angles of the defects. These results suggest that the PEM technique has a potential to detect 16-nm size defects on an hp 64-nm patterned EUV mask.