16:30 〜 16:45
▼ [20p-B101-9] Fabrication and evaluation of BiSb topological insulator / perpendicular magnetization CoFeB multilayer film for SOT-MRAM application
キーワード：spintronics, topological insulator, spin current
With the processing of semiconductor getting into 2 nm recently, increasing the device performance by just scaling-down becomes physically infeasible. In addition, technologies such as AI (Artificial intelligence), IoT (Internet of Things), and cloud services have recently developed at a stretch, and the demand for data centers is also increasing rapidly. Power saving performance was more important than computing performance. In this context, MRAM (Magnetic Random Access Memory) has been studied as a very promising technology. In addition to being non-volatile, MRAM is capable of high-speed operation and has a long life because it can be read non-destructively. In recent years, a new MRAM structure has been proposed as a method to solve this problem, which is called SOT (Spin Orbit Torque)-MRAM. In this study, Bi1-xSbx, a material with high spin Hall angle and high conductivity, is treated as a spin current source, and the CoFeB / MgO vertically magnetized multilayer film is used for the MTJ free layer which has been inverted by the spin current successfully. First of all, we confirm that PMA can be stably realized in Ta / CoFeB / MgO, BiSb / Ta / CoFeB / MgO, MgO / CoFeB / Ta and Ti / CoFeB / MgO four kinds of structure with typical coercivity Hc (around 50 Oe) and anisotropic magnetic field Hk (about 1.7 kOe -2.7 kOe) Then, in structure of BiSb/buffer layer/CoFeB/MgO, we have found that spin hall angle gets largest when the total thickness of the buffer layer reaches around 4 nm. This special buffer layer thickness-spin Hall angle relationship reflects the overall effect of lattice distortion, surface roughness, and prevention of Sb diffusion. Comparing all the results, Ti/Ta buffer layer has shown a best performance as a spin current conduction layer with a spin hall angle about 1.4.