I have used: 5% H2O2:5% H2SO4:90% H2O. to etch 6.66 µm Bi. My notes say that 2.5% may be better, but I have no data. Photoresist gap was 5 µm and yielded 12-15 µm etched linewidth. > > Does anyone knows about the wet etchant for the Bismuth thin film?