Particle-in-cell/Monte Carlo collisions treatment of an Ar/O2magnetron discharge used for the reactive sputter deposition of TiOxfilms

Abstract

The physical processes in an Ar/O-2 magnetron discharge used for the reactive sputter deposition of TiOx thin films were simulated with a 2d3v particle-in-cell/Monte Carlo collisions (PIC/MCC) model. The plasma species taken into account are electrons, Ar+ ions, fast Ar-f atoms, metastable Ar-m* atoms, Ti+ ions, Ti atoms, O+ ions, O-2(+) ions, O- ions and O atoms. This model accounts for plasma-target interactions, such as secondary electron emission and target sputtering, and the effects of target poisoning. Furthermore, the deposition process is described by an analytical surface model. The influence of the O-2/Ar gas ratio on the plasma potential and on the species densities and fluxes is investigated. Among others, it is shown that a higher O-2 pressure causes the region of positive plasma potential and the O- density to be more spread, and the latter to decrease. On the other hand, the deposition rates of Ti and O are not much affected by the O-2/Ar proportion. Indeed, the predicted stoichiometry of the deposited TiOx film approaches x = 2 for nearly all the investigated O-2/Ar proportions.