Crystallographic texture control of sputtered HfN thin films using low oxygen partial pressures

The authors studied the development of crystallographic texture in hafnium nitride (HfN) films deposited by off-normal incidence reactive magnetron sputtering at room temperature. Films are prepared with and without added oxygen in N2/Ar mixtures. Texture measurements were performed by x-ray pole figure analysis of the (111) and (200) diffraction peaks. The authors found that HfN deposited at 40 deg. without added oxygen has a strong <100> fiber texture with no in-plane alignments showing the dominance of thermodynamic effects in the course of texture evolution. Oxygen is deliberately introduced into the sputtering gas ambient to study its effects on microstructure formation. As the oxygen partial pressure (O2 pp) is increased in the range of 1.33x10-5 to 1.33x10-4 Pa, HfN out-of-plane orientation changed to <111> with a substantial in-plane alignment in <100> direction as well. In this case, texture analysis of each individual diffraction peak revealed the existence of two populations of grains indicating a competition between (111) and (200) planes. A transition towards hafnium oxynitride phases occurred at high O2 pp's. The authors propose that oxygen presence during deposition reduces the adatom surface mobility, which enables kinetic effects to govern the texture formation and thus leads to a biaxial alignment in HfN films