The Effects of Deposition Rate and Annealing on CoFeB/MgO/CoFeB Perpendicular Magnetic Tunnel Junctions

In this study, we report the effects of deposition rate and composition of CoFeB on the magnetic properties of CoFeB/MgO/CoFeB structures. We found that the asymmetry exists not only in different deposition stack sequences (bottom structure Ta/CoFeB/MgO and top structure MgO/CoFeB/Ta), but also in different compositions of CoFeB. Co₄₀Fe₄₀B₂₀ is more suitable for the bottom structure, while Co₂₀Fe₆₀B₂₀ has better perpendicular magnetic anisotropy for the top structure. Based on the results The full pMTJ stacks of structure Ta 5/Co₄₀Fe₄₀B 1.3/MgO 1/Co₂₀Fe₆₀B₂₀ 2.2/Top layer (nm unit) were fabricated with different deposition rates and annealing temperatures. We found that low deposition rate (0.03 nm/s) can prevent overlapping magnetization reversal of both free and fixed layer. The antiferromagnetic coupling between the free and fixed layer was found to increase with annealing temperature which can be identified as the consequence of orange-peel coupling.