Monolithic formation of thin films on the vertical surface of a substrate by a dual-ion-beam sputtering technique

We have developed a novel method for the selective deposition of thin films on the vertical surface of a planar substrate with a vertical step. This was done with a dual-ion-beam sputtering apparatus that is equipped with two ion-beam sources. Using this technique a multilayer filter was monolithically formed on the vertical surface of a Si substrate on which a photodetector had been fabricated, and clear filtering-photodetecting characteristics were observed. This technique can be applied to the monolithic integration of thin-film devices and waveguide-type optical devices with a vertical end facet.