Plasma enhanced chemical vapor deposition silicon oxynitride optimized forapplication in integrated optics

Silicon Oxynitride (SiON) layers are grown from SiH4/N-2, NH3 and N2O by Pl asma Enhanced Chemical Vapor Deposition (PECVD). The process is optimized w ith respect to deposition of layers with excellent uniformity in the layer thickness (delta d < 1%), high homogeneity of the refractive index (Delta n = 2-7 X 10(-4)) and good reproducibility of the layer parameters. The opti cal losses of slab-type waveguides is determined to be as low as 0.2 dB/cm at 632.8 nm wavelength. Due to absorption of N-H and Si-H vibrational overt ones, the optical losses in the third telecommunication window, around 1550 nm, is increased to about 2 dB/cm for low index layers. By an anneal step, however, the hydrogen content of the films can be reduced as is confirmed by IR-spectroscopy and the optical losses decrease to below 0.2 dB/cm. Base d on the optimized PECVD SiON technology, a layer structure fulfilling the strong requirements of telecommunication devices, is designed for operation at 1550 nm wavelength. This structure, consisting of a SiON core layer (n = 1.4857) surrounded by thick oxide cladding layers (n = 1.4637), has the p otential for realization of channel waveguides allowing for low-loss bends with a small bending radius and high fiber-to-chip coupling efficiency. (C) 1999 Elsevier Science S.A. All rights reserved.