Abstract
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.
Highlights
The magnetic tunnel junction (MTJ) with two ferromagnetic (FM) metal layers sandwiched by a nanometer-thick insulating layer, displays a large tunneling magnetoresistance (TMR) effect at room temperature, making them attract a huge amount of interests in spintronics
The optical microscopy image of the final Magnetic tunnel junction (MTJ) device shown in Fig. 2(g) proves that it is easy to perform the 4-point probe measurement to circumvent the influence of the contact resistance
We have demonstrated the effect of re-deposition on the performance of MTJs with changing the ion beam etching angle
Summary
The magnetic tunnel junction (MTJ) with two ferromagnetic (FM) metal layers sandwiched by a nanometer-thick insulating layer, displays a large tunneling magnetoresistance (TMR) effect at room temperature, making them attract a huge amount of interests in spintronics. Nowadays, the applications of MTJ have been spread out in various fields, such as magnetoresistive sensors, magnetic random access memories (MRAM), non-volatile logic devices and microwave nano-oscillators. As a current-perpendicular-toplane (CPP) structure, the high-quality MTJ stack multilayer deposition and the highly controllable fabrication process is of crucial importance for the high-performance MTJ devices. The stack TMR is commonly examined by using current-in-plane tunneling (CIPT) technology.21 This method is limited by the fact that the current is hard to tunnel through the insulating barrier, which can result in a low TMR. The re-deposition effect induced by IBE was introduced and a simplified circuit model was established to explain the experimental results This model was used to fit the experimental data to obtain a newly defined material parameter α’ for the MTJ stacks, and the value is well consistent with the experimental results. This can provide a simple method to evaluate the performance of the MTJ stacks, which can eliminate the influence of the device fabrication process
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