Magnetic Properties and Film Structure of Fe-N Films prepared by Multipolar Magnetic Plasma Confinement Sputtering Method

Thin films of Fe and Fe-N have been prepared using an rf magnetron sputtering system equiped with multipolar magnetic plasma confinement (MMPC), which is efficient for preparation of ferromagnetic thin films at low pressures. For sputtering with 150 W rf-power, the deposition rate of Fe film is 12-14 nm/min, which is three times larger than that of conventional planar magnetron sputtering system. Iron nitride films have been sputter-deposited in an Ar-N2 gas mixture at several pressures, Psp, of 5-0.6 mTorr and the gas flow ratio, fN2 = N2/(Ar + N2), of 0-0.6. The crystalline and morphological structures, the nitrogen content in the film, and the resistivity depend strongly on Psp and fN2. These dependences are explained by the energy of sputtered particles reached at the film surface. In particular, the films prepared at 0.6 mTorr, which is realized by MMPC method, exhibit the crystalline structures of Fe, Fe4N and Fe3N phases depending on fN2, and show the very high purity.