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 °C, using argon (Ar) 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 sccm, RF 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.