Dry etching of extreme ultraviolet lithography mask structures in inductively coupled plasmas

Abstract

Extreme ultraviolet lithography (EUVL) is currently being examined for its potential use in the next generation of lithography techniques. Among the core EUVL technologies, mask fabrication is of considerable importance due to the use of new reflective optics. This study investigated the etching properties of EUVL mask materials, such as Al2O3 antireflection coating (ARC), TaN (absorber layer) and Ru (buffer/capping layer), by varying the Cl-2/Ar gas flow ratio, dc self-bias voltage (Vd,) and top electrode power in inductively coupled plasma. The Al2O3 (ARC) layer could be etched with an etch selectivity approaching 0.5 over the TaN absorber layer. The ARC/TaN stack could be etched with an infinitely high etch selectivity over the Ru layer. Etching of the stacked mask structures with a 200 nm line/space hydrogen silsesquioxane e-beam resist pattern showed a profile angle of 85 degrees and an etch stop on the Ru buffer/capping layer.