Vanadium and vanadium nitride thin films grown by high power impulse magnetron sputtering

Abstract

Thin vanadium and vanadium nitride films were grown on SiO2 by non-reactive and reactive high power impulse magnetron sputtering (HiPIMS), respectively. The film properties were compared to films grown by conventional dc magnetron sputtering (dcMS) at similar conditions. We explored the influence of the stationary magnetic confinement field strength on the film properties and the process parameters. The deposition rate is much lower for non-reactive sputtering by HiPIMS than for dcMS. Furthermore, for both dcMS and HiPIMS the deposition rate is lower for strong magnetic confinement. Structural characterization was carried out using x-ray diffraction and reflection methods as well as atomic force microscopy and scanning electron microscope. Both dcMS and HiPIMS grown vanadium films are polycrystalline with similar grain size regardless of magnetic field strength. For dcMS grown vanadium films the surface roughness is higher when a strong magnetic field is used. For both non-reactive growth of vanadium and reactive growth of vanadium nitride the HiPIMS process produces denser films with lower surface roughness than dcMS does. Lowering the magnetic field strength increases the deposition rate significantly for reactive HiPIMS while it increases only slightly in the reactive dcMS case. The films grown by HiPIMS with strong magnetic confinement exhibit higher density and lower roughness. We find that the operating pressure, growth temperature, discharge voltage and film thickness has influence on the properties of HiPIMS grown vanadium nitride films. The films are denser when grown at high temperature, high discharge voltage and low pressure. The density of those films is lower for thicker films and thicker films consist of larger grain size. For all the films explored, higher density coincides with lower surface roughness. Thus, the deposition method, magnetic field strength, growth temperature, discharge voltage, film thickness and growth pressure have a significant influence on the film quality and structural properties, including the grain size for the various orientations.

Electrochemical Stability Enhancement in Reactive Magnetron Sputtered VN Films upon Annealing Treatment

“…Upon thermal treatment, a small shift towards a greater diffraction angle was noticed, which may be attributed to stress relaxation, with consequent reduction in the lattice constant. The fcc δ-VN phase formation under the prevailing conditions of power density (12.7 W•cm −2 ) and nitrogen gas flow (14 sccm) as well as the resulting film growth rate (3.83 nm•min −1 ) confirm the findings reported earlier [16,17].…”

The Effect of Magnetic Field Strength and Geometry on the Deposition Rate and Ionized Flux Fraction in the HiPIMS Discharge

“…Bradley et al [19] reported on a deposition rate increase by a factor of 2 for a Ti target when the magnetic field strength at the target was reduced by 45%. In addition, while weakening |B| by 82% a factor of 2.6 higher deposition rate was observed while depositing vanadium films by HiPIMS, although for the weaker magnetic field the films exhibited significantly higher surface roughness and were not as dense [28].…”

Comparison of magnetic and structural properties of permalloy Ni80Fe20 grown by dc and high power impulse magnetron sputtering

“…The current initiation delay time changes linearly in the 0.33 -0.73 Pa range and increases dramatically at lower pressures. Previously we have reported the increased delay time with decreasing Ar pressure when sputtering a tantalum target [38] and for a vanadium target in Ar/N 2 mixture [31]. Due to its stochastic nature, the delay time can be explained statistically as described by Yushkov and Anders [39].…”

“…This high electron density leads to a high ionization fraction of the sputtered material. As a result HiPIMS presents denser [27][28][29], void free [30] and smoother coatings [28,30,31] can be grown by HiPIMS and they are claimed to have the same composition as the target over wide range of pressures [32]. This is important since dcMS has been found to present 2.3 at.% change in iron content of Py by changing the pressure in the 0.38 -2.4 Pa range [18] which can have significant effect on the magnetic properties, as discussed e.g.…”