Effects of sputtering parameters and annealing temperatures on magnetic properties of CoFeB films

Abstract

In this paper, soft magnetic CoFeB films were successfully deposited onto silicon substrates using radio frequency (RF) magnetron sputtering technique and their morphology, roughness (Rq) and magnetic properties were focused. Before annealing, CoFeB films prepared with different sputtering powers (60 W, 90 W, 120 W and 150 W) exhibit amorphous structure. The out-of-plane coercivity (Hc) gradually enhances from 40.2 to 66.4 Oe as the sputtering power increases, and the saturation magnetization (Ms) reaches the maximum of 1117 emu/cm3 at 90 W sputtering power. Then, the CoFeB film samples with 90 W were annealed by 200 °C, 300 °C, 400 °C and 500 °C, respectively. Annealing treatments at 300 °C and 400 °C transfers amorphous state into crystalline state, which is demonstrated by the appearance of the observable diffraction peak of CoFe (110). The out-of-plane Hc decreases from 40.2 to 30.5 Oe at annealing temperature range of RT to 300 °C. The annealed film has a greatest Ms of 1280 emu/cm3 at 300 °C. However, the Hc gradually increases from 30.5 to 68.9 Oe annealed from 400 °C to 500 °C due to the deterioration of the thin film. Collectively, the process conditions of sputtering at 90 W and annealing at 300 °C or 400 °C are favorable for crystallization and excellent magnetic properties in CoFeB films.