Effect of thermal annealing on the structural and mechanical properties of amorphous silicon carbide films prepared by polymer-source chemical vapor deposition

We report on the effect of thermal annealing on the structural and mechanical properties of amorphous SiC thin films prepared by means of a polymer-source chemical vapor deposition process. The chemical bondings of the a-SiC:H films were systematically examined by means of Fourier transform infrared spectroscopy (FTIR). The film composition was measured by X-ray photoelectron spectroscopy, while X-ray reflectivity measurements were used to account for the film density variations caused by the post-annealing treatments over the 750-1200 degrees C range. In addition, their mechanical properties (hardness and Young's modulus) were investigated by using the nano-indentation technique. FTIR measurements revealed that not only the intensity of a-SIC absorption band linearly increases but also its position is found to shift to a higher wave number as a result of annealing. In addition, the bond density of Si C is found to increase from (101.6-224.5) x 10(21) bond center dot cm(-3) accompanied by a decrease of Si-H bond density from (2.58-0.46)x10(21) bond center dot cm(-3) as a result of increasing the annealing temperature (L) from 750 to 1200 degrees C. Annealing-induced film densification is confirmed, as the a-SIC film density is found to increase from 236 to similar to 2.75 g/cm(-3) when L is raised from 750 to 1200 degrees C. In addition, as T-a is increased from 750 to 1200 degrees C, both hardness and Young's modulus are found to increase from 15.5 to 17.6 GPa and 155 to 178 GPa, respectively. Our results confirm the previously established linear correlation between the mechanical properties of the a-SiC films and their bond densities. (C) 2009 Elsevier B.V. All rights reserved.