Fabrication of amorphous silicon films for arrayed waveguide grating application

Amorphous silicon (a-Si) optical films were deposited on a silicon substrate by ICP-PECVD at the temperature of 300 degrees C, using argon (At) and silane (SiH4) as gas precursors, with the influences of precursors' flow rate, RF power and operating vacuum pressure on the optical properties and microstructure evolutions of a-Si films as the object of our investigation in this study. Optical characteristics of a-Si films indicated that optimum refractive index and extinction coefficient at 1550 nm wavelength can be achieved by using the process parameters of argon/silane flow rate of 400 seem, P,F power wattage of 40 W with an operating vacuum pressure of 60 Pa, respectively. Microstructure evolutions show that the few defects and silicon nano-crystallized structures existing in a-Si films might increase the extinction coefficient. We strongly suggest adopting the optimum process parameters and thermal annealing to fabricate a rib-type a-Si arrayed waveguide grating device with 8 channels and 1.6 nm channel spacing; and its coupling loss and propagation loss were about -0.74 dB and -0.14 dB/cm, respectively. (c) 2006 Elsevier B.V. All rights reserved.