Surface nitrogen concentration dependence of the nitrogen incorporation in reactively sputtered FeXN films

Abstract

N incorporation is critical to soft magnetic properties of the FeXN film. Previous work showed experimentally that the N concentration is linearly proportional to the ratio of the N to Fe atomic fluxes arriving at the surface of the film (flux ratio rule). Recently it was shown that under certain conditions, N incorporation is more efficient than the flux ratio rule would suggest. In this work a simple analytic model based on steady-state N and Fe transport fluxes during the reactive sputtering process is used to understand these two observed phenomena. It is shown that the N concentration in the film depends on the amount of N on the surface of the growing film. In a surface N-depleted state, the flux ratio rule is followed, while in a surface-N rich state, the N incorporation in the film increases with deposition rates even when the ratio of incoming N to Fe fluxes is kept constant. Experimental data from sputtered FeAlN films can be reproduced reasonably well with the current analysis.