Reactive sputtering of high moment Fe-N soft magnetic films with in-situ plasma diagnosis and control

Fe–N films with 4πM_S of up to 26 kG were deposited by reactive rf-sputtering on single crystal Si(001) and glass substrates with Fe seed layers. Optical emission spectra of the Ar/N₂ plasma were obtained from the vicinity of the target surface via an optical fiber. Nitrogen content of the plasma was pre-set according to the peak height (set point) of a particular wavelength emission peak of the optical emission spectrum of the plasma and maintained constant throughout the film deposition process via the closed loop controller. The saturation magnetization of the Fe–N films initially increased with the increase ofNcontent in the plasma (set point), reaching maximum at set point around 40 and then decreased with further increase of nitrogen. The nitrogen content of the films with maximum 4πM_S was about 4.26 at%. The major phase of the as-deposited Fe–N films, analyzed by X-ray diffraction was α-Fe. Minor diffraction peaks at 2θ of 28.9° corresponding to α"-Fe₁₆N₂ phase were present for Fe–N films, which might be responsible for the increase of saturation magnetization of the Fe–N films.