Pattern Fabrication Technique for Ta–Ge Amorphous X-Ray Absorber on a SiC Membrane by Inductively Coupled Plasma

We developed a pattern etching method for Ta–Ge (Ta3Ge) amorphous X-ray absorbers on a SiC membrane using a mixture of Cl2 and BCl3 gases with a single-layer e-beam resist. For this work, an inductively coupled plasma (ICP) etcher with a helium back surface cooling system was used. High etching selectivity and anistropic etching were achieved by regulating electrode temperature and BCl3 concentration ratio. The etching selectivity of Ta3Ge to the resist is 6.5. Ta3Ge patterns of 0.1 µm dimensions with vertical sidewalls were fabricated. Good etching rate uniformity was also obtained over a 61-mm-diameter membrane field. We found that Ru film was a suitable etching stopper material because it has high dry-etching durability and can be easily removed by oxygen plasma etching.