Changes in chemical composition and nanostructure of SiC thin films prepared by PECVD during thermal annealing

Silicon carbide (SiC) thin films were deposited on silicon (Si) using plasma enhanced chemical vapor deposition (PECVD). Annealing was done in a rapid thermal annealing furnace at a temperature of 1300 degrees C. As-deposited and annealed Si-rich and stoichiometric SiC thin films were investigated by analytical transmission electron microscopy (AEM). TEM-energy-dispersive X-ray spectroscopy was used to quantify the chemical composition of the SiC thin films with high accuracy. The chemical composition of the near stoichiometric SiC thin film changed during annealing from Si0.4C0.6 to Si0.5C0.5 due to diffusion of Si from the Si substrate into the film. The Si-rich Si1-xCx film had the identical chemical composition of Si0.8C0.2 before and after annealing. As-deposited films show nanoporosity within the bulk film. During annealing, v-shaped defect structures were formed at the interface of the stoichiometric SiC thin film to the Si substrate. Diffraction patterns revealed that as-deposited films were amorphous. During annealing the crystallization of 3C-SiC occurred in near-stoichiometric SiC thin films, whereas in Si-rich Si1-xCx thin films two phases, namely Si and 3C-SiC, crystallized. Low-loss and core-loss electron energy loss spectroscopy (EELS) verified the diffraction results. In the low-loss spectra of the near stoichiometric SiC thin film, a plasmon peak located at 20.2 eV before and at 22.3 eV after annealing was detected. The low-loss spectra of the Si-rich Si1-xCx thin film showed an asymmetric plasmon peak with two maxima located at 18.5 and 25.0 eV in the as-deposited film and 18.6 and 24.3 eV in the annealed Si-rich Si1-xCx film. The 18.5 eV plasmon peaks is assigned to Si and the 25 eV plasmon peak is attributed to the SiC phase. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim