Process capability of etched multilayer EUV mask

摘要

With shrinking pattern size at 0.33NA EUV lithography systems, mask 3D effects are expected to become stronger, such as horizontal/vertical shadowing, best focus shifts through pitch and pattern shift through focus. Etched multilayer EUV mask structures have been proposed in order to reduce mask 3D effects. It is estimated that etched multilayer type mask is also effective in reducing mask 3D effects at 0.33NA with lithographic simulation, and it is experimentally demonstrated with NXE3300 EUV Lithography system. We obtained cross-sectional TEM image of etched multilayer EUV mask pattern. It is observed that patterned multilayer width differs from pattern physical width. This means that effective reflecting width of etched multilayer pattern is smaller than pattern width measured by CD-SEM. In this work, we evaluate mask durability against both chemical and physical cleaning process to check the feasibility of etched multilayer EUV mask patterning against mask cleaning for 0.33NA EUV extension. As a result, effective width can be controlled by suitable cleaning chemicals because sidewall film works as a passivation film. And line and space pattern collapse is not detected by DUV mask pattern inspection tool after mask physical cleaning that includes both megasonic and binary spray steps with sufficient particle removal efficiency.