Study on the effect of re-deposition induced by ion beam etching on MTJ performances

Magnetic tunnel junction (MTJ) as a key spintronics device can be used for the high-sensitivity magnetic field sensor and high-density non-volatile magnetic random access memory (MRAM). To obtain a high tunneling magnetoresistance (TMR), precise control of the etching process for MTJs is an essential step. In order to investigate the effect of the etching angle on the performance of MTJ devices, a series of MTJ pillars are fabricated by etching with the incidence angle of 10°, 20° and 30°. The prepared samples are characterized by the optical microscopy and SEM, and the R-H curves are also measured and then statistically analyzed. The results reveal that the performance of the MTJ is strongly affected by the IBE process, displaying the uniformity of the pillars edge and MTJ performance will improve as well with the increase of the etching angle. Then, a simplified model based on the re-deposition effect of the etching process is established to explain the experimental phenomena. Furthermore, a newly defined material parameter is introduced in this model and obtained with fitting the experimental results. This proves a valuable way to evaluate the quality of the MTJ stack film without the interference of the device fabrication process.