Role of nitrogen concentration in the thermal stability of the anisotropy in FeTiN thin films

The thermal stability of the anisotropy of FeTiN films has been investigated. The films were prepared by DC reactive sputtering on glass substrates in a N-2/Ar atmosphere, and the N flow rate, chamber pressure, sputtering power and film thickness were varied. Target-substrate distances of 6.7 cm and 4.1 cm were used. For films sputtered at the normal target-substrate distance of 6.7 cm, the anisotropy of FeTiN films rotated about 90 degrees after a 100 degreesC, 1 hour annealing in the presence of a 300-400 Oe field perpendicular to the original easy axis. When the 4.1 cm target-substrate distance was used, the anisotropy direction was stable with N concentrations of 6 at.% or less in the films. The anisotropy was unstable for higher N concentrations. X-ray data and stress measurements taken as a function of N concentration showed lattice and stress changes coincident with the stability changes. The dependence of the thermal stability of the film anisotropy on target-substrate distance and N flow rate will be presented and possible mechanisms will be discussed.