Evaluation of MR ratio and reliability of MTJ device having SiN sidewall by modifying reference layer thickness


 For high-performance magnetic tunnel junction (MTJ) devices, the ion beam etching (IBE) process is improved by including the fabrication of a SiN sidewall around the MgO tunnel barrier layer. This sidewall prevents the redeposition from lower metal layers on the edge of the MgO layer. The magnetoresistance (MR) ratio at an IBE angle of 20° is larger than that at 60°. Edge current by the redeposition is suppressed by the SiN sidewall, and etching damage is reduced by decreasing the IBE angle. The dependence of the MR ratio on the reference layer thickness is investigated using an FeB reference layer with thicknesses of 0.7, 0.9, and 1.05 nm. The MR ratio increases with the reference layer thickness, and an MR ratio of 180% is achieved at a layer thickness of 1.05 nm. A resistance variability of under 0.5% confirms the high resistance stability of the tested device.