Silicon oxynitride layers for optical waveguide applications

We report on the fabrication and characterization of silicon oxynitride (Si ON) layers for applications as planar optical waveguides in the 1550 nm wav elength region. The optically guiding SiON waveguide core layer has a relat ively high refractive index of 1500 and is sandwiched between two silicon o xide cladding layers with a lower refractive index of 1450. The SiON layer is deposited by plasma-enhanced chemical vapor deposition using silane, nit rous oxide, and ammonia as gaseous precursors. Waveguide bends with a radiu s of curvature as small as 1.5 nun can be realized because of the high refr active index difference achievable between core and cladding layers. This a llows the fabrication of compact, relatively complex integrated optical wav eguide devices. The deposition process and the characterization of the SiON films are discussed. The strengths of this high refractive index contrast planar waveguide technology are illustrated using the trample of an optical add/drop filter for wavelength division multiplexing applications in the f ield of optical communication systems. (C) 2000 The Electrochemical Society . S0013-4651(99)05-109-5. All rights reserved.