Atomic layer deposition of HfNx films and improving the film performance by annealing under NH3 atmosphere

Abstract

HfN_x films were deposited by atomic layer deposition (ALD) using Hf[N(CH₃)(C₂H₅)]₄ (TEMAHf) and NH₃ as the Hf-precursor and reactant gas, respectively. A precleaning step using TEMAHf as a reducing agent was devised to minimize the oxygen concentration in the as-deposited film. Consequently, the oxygen concentration in the film was reduced by ∼66%. In addition, the carbon impurity concentration caused by the side effects of the precleaning step and the remaining oxygen concentration were effectively reduced through post-NH₃ annealing. The oxygen concentration inside HfN_x decreased as the annealing temperature increased. HfN_x films annealed under 900 °C showed dielectric properties similar to hafnium oxynitride (HfO_xN_y). However, films annealed over 950 °C transformed into a more electrically conducting HfN film, showing a resistivity of ∼10⁶ μΩ cm.