Fabrication of step-edge structures on R-plane sapphire using a selective wet etch process

With the aim of using some well established techniques in the planar tecnology of silicon for the fabrication of high-T-c grain boundary based junctions, we investigated a process suitable for the realisation of step-edge on R-plane sapphire substrates. Step-edges were prepared by exposing a photolitographically defined area to Ar+ ion implantation. The damaged area was selectively removed by different wet etching processes. With this technique we were able to produce 150 nm height steps, 30 degrees-45 degrees slope. The surface roughness on both sides of the step was the same as that of the virgin sustrate. The influences of dose, angle of implant, etch rate and related main feature of the process are discussed.