Characterization of Amorphous Silicon (α-Si) and Silicon Rich Silicon Oxide (SiOx) Materials Produced by ECR-PECVD

Abstract

Silicon based materials, including silicon oxides and silicon oxynitrides, have found use in a number of areas in photonics including waveguides, antireflection and highly reflective coatings for laser facets, and detectors. For effective use of these materials in photonics it is necessary to characterize their optical properties as a function of their composition and structure. Since these characteristics are often dependent on the method used to deposit the films it is necessary to also determine the effect of deposition type and conditions on the film's properties. Recently, silicon based materials have been seen to display luminescence due to quantum confinement effects when nanocrystals are formed. This opens up the possibility of a silicon based emitter, something that has not had previous success due to the indirect bandgap of bulk silicon. The development of a silicon based emitter in turn would open up the possibility for monolithically integrated photonic circuits that could take advantage of CMOS processing technology. This thesis presents the results of research into the characterization of amorphous silicon and silicon oxide thin films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition. Optical properties of the films have been determined through the use of ellipsometry and correlated with the results from compositional analysis, done using Rutherford backscattering and elastic recoil detection, and bonding structure analysis, done using Fourier transform infrared spectroscopy. Nanocrystals were formed within the films by subjecting them to post-deposition thermal annealing, which induces a phase separation in silicon rich silicon oxide films. The effects of different annealing conditions on composition, structure and optical properties have also been analyzed. Finally, photoluminescence experiments were conducted on the films and correlated with the results from other characterization techniques.