The capability of high magnification review function for EUV actinic blank inspection tool

One of the most challenging tasks to make EUVL (Extreme Ultra Violet Lithography) a reality is to achieve zero defects for mask blanks. However, since it is uncertain whether mask blanks can be made completely defect-free, defect mitigation schemes are considered crucial for realization of EUVL. One of the mitigation schemes, pattern shift, covers ML defects under absorber patterns by device pattern adjustment and prevents the defects from being printed onto wafers. This scheme, however, requires accurate defect locations, and blank inspection tools must be able to provide the locations within a margin of the error of tens of nanometers. In this paper we describe a high accuracy defect locating function of the EUV Actinic Blank Inspection (ABI) tool being developed for HVM hp16 nm and 11 nm nodes.