Actinic EUVL mask blank inspection capability with time delay integration mode

We have been developing an actinic full-field mask blank inspection system to detect multilayer phase defects with dark field imaging. Detection probability with no false detection at full-field of a mask blank was improved, and then a probability of capturing 1.5 nm-high and 60 nm-wide defects was attained to be 100 %. A mask blank was inspected, and a small native defect with its top dimensions of 1.1 nm in height and 20 nm in width was successfully detected. The bottom dimensions of the smallest two defects were estimated with simulation so that the experimental and simulated signal intensities could be correlated. Using the estimated bottom dimension, the defects were found to impact on CD of 22 nm L/S pattern. Assuming that the bottom dimension was the same as the top dimension, CD variation due to the defects was found to be approximately half of those of the estimated bottom dimension. This means that some internal structure within the defect is a key factor in the estimation of impact on wafer. The detection probability improvement also attained 100% detection of the both defects.