Liftoff lithography of metals for extreme ultraviolet lithography mask absorber layer patterning

The authors present a process for patterning Extreme Ultraviolet Lithography (EUVL) mask absorber metal using electron beam evaporation and bi-layer liftoff lithography. The Line Edge Roughness (LER) and Critical Dimension Uniformity (CDU) of patterned chrome absorber are determined for various chrome thicknesses on silicon substrates, and the viability of the method for use with nickel absorber and on EUVL masks is demonstrated. Scanning Electron Microscope (SEM) data is used with SuMMIT software to determine the absorber LER and CDU. The Lawrence Berkeley National Labs Actinic Inspection Tool (AIT) is used to verify the printability of the pattern down to 24nm half pitch. The effect of processing on the integrity of the mask multilayer is measured using an actinic reflectometer at the College of Nanoscale Science and Engineering.