"Actinic-only" defects in EUVL mask blanks-native defects, barely detectable by visible-light inspection

An actinic (at-wavelength) inspection technology is essential for learning the nature of defects at the developmental stage of the technology and for eventually qualifying less costly non-EUV inspection methods. In this paper, we discuss recent results of actinic defect counting experiments covering several cm/sup 2/ area. Results include some small actinic-only defects, not detected by optical inspection tools, and a new class of relatively large, absorbing defects.