(The) effect of capping layer on tunneling magnetoresistance in CoFeB/MgO/CoFeB based magnetic tunnel junction

Abstract

Magnetic tunnel junction (MTJ) consisting of ferromagnet/tunnel barrier/ferromagnet structures has been extensively studied because of its large tunnel magnetoresistance (TMR), which can be harnessed for information storage in magnetic random-access memories (MRAM). In particular, the MgO-based MTJs have received much attention due to their large TMR originating from spin-dependent tunneling through (001)-textured MgO tunnel barrier. In addition, CoFeB is widely utilized as ferromagnetic electrodes, which helps the crystallization of the MgO tunnel barrier during the post annealing process. It was shown that a heat treatment changes as-deposited amorphous CoFeB to BCC structure via B diffusion to the adjacent tunnel barrier and capping layer. Therefore, the capping layer is expected to modify the annealing effect on the crystallization of the CoFeB/MgO tunnel junction and associated TMR. In this study, In the in-plane magnetic tunnel junction structure based on the Pt capping layer, the limitations and problems of the Pt capping layer were investigated through TMR by annealing temperature and CoFeB thickness of the free layer, and the case of Ta and W capping layers were investigated from a perspective of the resistance of annealing temperature and TMR.