Abstract

Integrated optics is believed to be the key technology for future integrated optical systems. One standard method for processing planar waveguides is a combination of plasma enhanced chemical vapor deposition (PECVD) for growing glass layers and photolithography/reactive ion etch (RIE) for creating the waveguides² (Fig. la). We present an investigation of the photosensitivity of germania-doped silica films. The results may lead to an alternate method for creating the guiding structure in planar waveguides that requires much fewer process steps. Instead of using a combination of photolithography and RIE for defining the guiding core, the index change due to photosensitivity of germanium-doped silica may be utilized (Fig. 1b). To investigate the photosensitivity, germanium-doped silica films were grown on a 4" silicon wafer in a PECVD chamber. These films were fabricated at a temperature of 300°C, a base pressure of 700 mTorr, and gas flows of 17 seem silane, 1600 sccm nitrousdioxide and up to 8 sccm germane followed by annealing at 800°C in a nitrogen atmosphere for two hours.

© 1994 IEEE