EUV absorbance and dry-etching characteristics of TaGeN films for EUVL mask absorber

EUV absorbance and dry-etching characteristics of TaGeN film for use as the absorber material in EUVL masks were evaluated. Measurement of the EUV reflectivity of TaGeN on a Mo/Si multilayer revealed the linear absorption coefficient of TaGeN film to be about 35 μm-1 at the wavelength of 13.5 nm. Reflectivity profiles obtained by simulations using this value fit measured profiles for several absorber thicknesses very well. Since the reflectivity of TaGeN on a multilayer is affected by the interference between the EUV light reflected from the absorber surface and that reflected from the multilayer underneath, the mask contrast varies periodically with absorber thickness. To obtain a mask contrast of 100, the TaGeN has to be 66 nm thick, if interference is not taken into account, and 80 nm thick, if it is. TaGeN film was ethced with an ECR plasma etcher using CI2 gas. The etching selectivity was found to be about 1.0 for TaGeN/resist and about 20 for TaGeN/Cr. 275-nm L/S patterns with vertical sidewalls were successfully fabricated in TaGeN. There were no serious problems with the CD control or LER of etched TaGeN patterns.