Growth and stress evolution of hafnium nitride films sputtered from a compound target

Abstract

Hafnium nitride films were deposited on silicon substrates by direct sputtering a compound target in an Ar atmosphere using a radio-frequency magnetron sputtering system. X-ray diffraction, x-ray photoemission spectrum, and Rutherford backscattering spectrometry revealed the successful formation of cubic stoichiometric HfN films in a wide deposition condition range. The residual stress in stoichiometric HfN films is compressive, and depends strongly on Ar pressure and sputtering power. Unlike element metal deposition, a transition point of Ar pressure at which residual stress experiences from compressive to tensile state has not been found in stoichiometic HfN films. Although an increase in Ar pressure could lower the stress value, nitrogen enrichment was found at 2.0 Pa and much oxygen was incorporated in the film deposited at 3.0 Pa and above, which can lead to a dramatic increase in film resistivity. Shallow recoil implantation of HfN species receiving energy from fast Ar species reflected at the target surface is suggested responsible for the evolution of the stress. A possible explanation was also given for the stoichiometric composition.