Selective formation of dielectric films on vertical surface of substrate for photonic integrated circuits

The authors investigated the deposition conditions of the bias-sputtering technique to form some sophisticated thin-film geometries for photonic integrated circuits, and they successfully formed a dielectric film selectively on a vertical surface of a substrate. The deposition rate on the vertical surface increases with the increases of the bias RF power because of the resputtering effect from the bottom surface. When the etching rate by the bias RF power is balanced with the deposition rate on the horizontal surface, one can form a film selectively on the vertical surface. This technique can be applied to the AR coating of DFB lasers and the formation of a multilayer filter on the vertical surface of a waveguide