Effects of Annealing on the Mechanical and Electrical Properties of DC Sputtered Tantalum Pentoxide (Ta2O5) Thin Films

Tantalum oxide (Ta2O5) films were deposited onto p-type silicon substrates using reactive DC magnetron sputtering, and then annealed for one hour in a dry air ambient at temperatures of 730°C, 780°C, and 830°C. Annealing was shown to reduce stress from the as-deposited sample, and resulted in a compressive stress state for samples annealed at 730°C and a tensile stress state for the other samples. Hardness values were approximately 8 GPa, with the exception of the sample annealed at 780°C that demonstrated a hardness of 13 GPa. Leakage current generally decreased with annealing, especially at the lower temperatures. Electrical breakdown was observed for as-deposited and the 830°C annealed films. Resistivities of the films ranged from 6.5 × 109 to 6.1 × 1012 ω-cm, with the film annealed at 830°C being the most conductive. Annealing also led to an increase in dielectric constant. Dielectric constants varied from 9.3 for the as-deposited to greater than 30 for the 780°C and 830°C annealed sample. Annealing resulted in crystalline films that were close to stoichiometric.