Damage analysis of EUV mask under Ga focused ion beam irradiation

EUV mask damage caused by Ga focused ion beam irradiation during the mask defect repair was studied. The concentration of Ga atom implanted in the multilayer through the buffer layer was calculated by SRIM. The reflectivity of the multilayer was calculated from the Ga distribution below the capping layer surface. To validate the calculation, a multilayer sample was irradiated with Ga FIB, and then EUV reflectivity was measured. The measured reflectivity change was in good agreement with the calculated value. An aerial image of patterns with Ga implanted region was simulated. The impact of the estimated Ga absorption on the linewidth of 32 nm hp line pattern was found to be less than 1 nm.