With shrinking pattern size, mask 3D effects are estimated to become stronger, such as horizontal/vertical shadowing, best
focus shifts through pitch and pattern shift through focus. To reduce these mask 3D effects, we have proposed etched
multilayer EUV mask structure and have also reported on the fabrication process of etched multilayer EUV mask, in which
line and space mask patterning has been demonstrated. And by using etched multilayer EUV mask, the reduction of mask 3D
effects is experimentally demonstrated. In our previous study, we have shown etched multilayer EUV mask has enough
durability against chemical erosion in suitable cleaning process.
In this work, to meet the demands of different variation on pattern in etched multilayer mask, especially fabrication process
for sub-60nm pattern based on effective mirror width in dark-field exposure is studied. 60 nm pillar pattern on mask is
obtained using negative tone resist with keeping resolution of line and space pattern. We also examined CD characteristics 60
nm line and space pattern in consideration of effective mirror width. This work represents that etched multilayer EUV mask
is ready for dark-field exposure of 15 nm pattern in wafer.