Analysis of step etching on SrTiO3 substrates for the step-edge YBCO Josephson junctions

A way to determine some important etching parameters in the step fabricatio n for high T-c step-edge Josephson junctions is described based on an analy sis of the dynamics of the etching process. The optimum thickness of the et ch mask is defined with negligible recession of the mask edge during the et ch. Under this condition, the equilibrium angle of the steps etched on the SrTiO3 (STO) substrate with an Nb mask has been calculated to be about 76 d egrees. With optimized mask thickness, its sharp sidewall and straight edge , high-quality steps on STO substrates with step height from 200-300nm and step angle above 70 degrees are made. Josephson junctions and dc-SQUIDs wit h high reproducibility and less parameter scatter are obtained on the step substrates.