Effect of post deposition annealing on the optical properties of HfOxNy films

We report in this letter that Hafnium oxynitride (HfO(x)N(y)) gate dielectrics were prepared by radio frequency (RF) reactive magnetron sputtering and optical properties of the HfO(x)N(y) thin films were investigated by spectroscopic ellipsometry with photon energy of 0.75-6.5 eV at room temperature. The investigations showed that the annealing temperatures have a strong effect on the optical properties of HfO(x)N(y) thin films. With increased annealing temperature, the refractive index n is observed to increase, while the extinction coefficient k decreases, respectively. The changes of the complex dielectric functions and the optical band gap E(g) with the annealing temperature are also discussed.(c) 2006 American Institute of Physics.