Silicon oxynitride integrated waveguide for on-chip optical interconnects applications

This work explores the microfabrication technology for realizing miniature waveguide structure for on-chip optical interconnects applications. Thick oxynitride films were prepared by plasma enhanced chemical vapor deposition (PECVD) with N₂O, NH₃ and SiH₄ precursors. The composition and the bonding structure of the oxynitride films were investigated with Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and secondary ion mass spectroscopy. Results showed that the silicon oxynitride deposited with gas flow rates of NH₃/N₂O/SiH₄ = 10/400/10 (sccm) has favorable properties for integrated waveguide applications. The refractive index of this layer is about 1.5 and the layer has comparative low densities of O–H and N–H bonds. The hydrogen bonds can be further eliminated with high temperature annealing of the as-deposited film in nitrogen ambient and the propagation loss can be reduced significantly with thermal annealing. An integrated miniature waveguide with cross-section of 2 μm × 3 μm was realized with the proposed technology. The waveguide is able to transmit signal in either TE or TM mode with propagation loss <0.6 dB/cm (at 1550 nm) and bending radius of about 6 μm.