On the phase formation of sputtered hafnium oxide and oxynitride films

Abstract

Hafnium oxynitride films are deposited from a Hf target employing direct current magnetron sputtering in an Ar-O 2 -N 2 atmosphere. It is shown that the presence of N 2 allows for the stabilization of the transition zone between the metallic and the compound sputtering mode enabling deposition of films at well defined conditions of target coverage by varying the O 2 partial pressure. Plasma analysis reveals that this experimental strategy facilitates control over the flux of the O − ions which are generated on the oxidized target surface and accelerated by the negative target potential toward the growing film. An arrangement that enables film growth without O − ion bombardment is also implemented. Moreover, stabilization of the transition sputtering zone and control of the O − ion flux without N 2 addition is achieved employing high power pulsed magnetron sputtering. Structural characterization of the deposited films unambiguously proves that the phase formation of hafnium oxide and hafnium oxynitride films with the crystal structure of HfO 2 is independent from the O − bombardment conditions. Experimental and theoretical data indicate that the presence of vacancies and/or the substitution of O by N atoms in the nonmetal sublattice favor the formation of the cubic and/or the tetragonal HfO 2 crystal structure at the expense of the monoclinic HfO 2 one.

Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbOxfilm growth

“…Most of the work regarding negative oxygen ions was performed using dcMS discharges rather than HiPIMS and the acceleration mechanism appears to remain unchanged when applying energetic pulses instead of dc power [41,42]. However, with the discovery of the ionisation zones, the question arises whether the associated potential hump influences the trajectory of the negatively charged oxygen ions or not.…”

Angular-resolved energy flux measurements of a dc- and HIPIMS-powered rotating cylindrical magnetron in reactive and non-reactive atmosphere

“…The dramatic increase of the overall energy per adparticle when working in the oxide regime could be attributed to the significant amount of negative ions such as O -reaching the probe surface. These ions have been detected in a DC magnetron discharges [35,36] and in HIPIMS plasmas [37]. Negative ions are sputtered from the oxidized target and accelerated by the cathode sheath.…”

Origin of the energetic ions at the substrate generated during high power pulsed magnetron sputtering of titanium

“…Several mechanisms have been proposed to explain the presence of energetic metal species in HiPIMS: i) reflected ions at the target [14]; ii) the high energy tail of the Thompson distribution [10]; iii) negative ions that are generated in front of the target surface that are accelerated towards the substrate by the full target potential [18,19,20]; iv) acceleration of metal species by a two-stream instability induced by localized ionization zones on the target [21]. Fast optical diagnostics revealed a pattern formation in HiPIMS plasmas, namely the formation of localized ionization zones or so called spokes [22,23].…”