Effects of substrate bias and growth temperature on properties of aluminium oxide thin films by using filtered cathodic vacuum arc

Two sets of aluminium oxide thin films were deposited using off-plane filtered cathodic vacuum arc (FCVA) at the working pressure of 6×10^-4 Torr under various substrate biases (-60 to -140 V) and substrate temperatures (120-600 °C), respectively. Optical and mechanical properties, such as refractive index, residual stress, hardness and Young's modulus, of the films were investigated. It has been found that both the refractive index and the residual compressive stress of the films increase with increasing substrate bias, while no significant changes in the hardness and Young's modulus could be noted. For the films grown at various growth temperatures, a transition temperature of 300 °C was found. A sharp increase in refractive index is observed as the substrate temperature varies from 200 to 300 °C. Beyond this temperature, no much significant changes in refractive index could be found. Hardness and Young's modulus follow similar trend to that of refractive index, while the residual compressive stress in the films behaves inversely.