Influence of substrate bias on microstructure and morphology of ZrN thin films deposited by arc ion plating

Abstract

Zirconium nitride thin films were fabricated using arc ion plating under negative substrate biases to investigate the influence of substrate bias on the ZrN films. The phase, composition, and surface morphology of the ZrN ?lms, with respect to substrate bias, were studied by XRD, EPMA, and FE-SEM, respectively. The results show that cubic ZrN and hexagonal Zr phases form in the ZrN films. The competition between surface energy and strain energy makes the preferred orientation change from (111) to (200) and then back to highly (111) preferred orientation as a function of substrate bias. With the increase of bias voltage, the crystallite size of ZrN films reduces from 30 to 15 nm. Meanwhile, the film microstructure evolves from an apparent columnar structure to a highly dense equiaxed structure, indicating that the ion bombardment enhanced by substrate bias can suppress the columnar growth in the ZrN films. Deposition rate and mole ratio of Zr to N increase with the increase of bias voltage and reach the maximum at –50 V, and then show a decline trend when bias voltage further increases.