RBS and ERD characterization of SiON films for optical waveguide applications

Silicon-based thin films on silicon substrates are interesting materials for the fabrication of passive and active channel waveguides since they are compatible with silica fibers used in telecommunications. They enable hybrid or monolithic integration with other active optoelectronic devices as well. Electron cyclotron resonance (ECR) plasma sources are used for plasma enhanced chemical vapour deposition (PECVD) of silicon oxynitride thin films. Unfortunately, films deposited using silane (SiH4) with ammonia (NH3) or deuteronammonia (ND) as nitrogen precursors, suffer from a too high absorption in the most interesting wavelength range for optical communication, 1.3-1.55 μm, due to the incorporation of H in the film. In this work the content of Si, O, N and H in waveguides with the structure Si/SiO2/SiON/SiO2, made by means of ECR-PECVD, has been determined with high accuracy using IBA techniques with the 5 MV tandem accelerator at CMAM. Specifically, 2 MeV He RBS and 35 MeV Si ERDA measurements, complemented with simultaneous RBS and ERDA measurements with 2.87 MeV He ions, have provided a detailed and reliable determination of the composition profile of the films.