Comparision of residual stress and optical properties in Ta2O5 thin films deposited by single and dual ion beam sputtering

We systemically studied the influence of the main deposition parameters on the properties of tantalum pentaoxide (Ta2O5) thin films deposited by single ion beam sputtering (SIBS) and dual ion beam sputtering (DIBS) as a function of the substrate temperature (50–200 °C). We found that as the substrate temperature increased, the deposition rate of both the SIBS and DIBS processes increased. For the DIBS process, increasing the substrate temperature caused the refractive index to be increased, with the maximum value being attained at 200 °C (n = 2.112). In the case where the assist ion gun is used, the use of a low process temperature (<100 °C) can greatly reduce the residual stress, whereas the residual stress was unaffected at a high temperature process. The atomic ratio of O/Ta was very close to the stoichiometric ratio of 2.5 for the films deposited using the DIBS process at 100 °C. The use of the low temperature process with the assist ion source improved the properties of the deposited films, which exhibited low residual stress, a stoichiometric composition and a smooth surface morphology.