Formation of Tunnel Barrier Using a New Pseudo-Atomic Layer Deposition Method and Its Application to Spin-Dependent Tunneling Junction

摘要

The tunneling barrier is crucial to the overall performance in magnetic tunnel junction. We have suggested a new formation method for the tunnel barrier, which has utilized pseudo atomic layer deposition with sputtering (PALDS). As is well known, all metallic thin films oxidize more or less under atmospheric conditions. With using this property of metallic thin films, we have prepared tunnel barrier by sputtering metallic thin film and exposing it to the oxygen ambience. From transmission electron microscopy (TEM) observation, the formed tunnel barrier has been confirmed to have clear and good interface between magnetic layers and tunnel barrier. From atomic force microscopy (AFM) observation, it has been also confirmed to have low surface roughness. The TMR MRAM cell manufactured using PALDS method has been shown to exhibit typical tunnel resistance of 86 kOMEGA centre dot mu m~2 and TMR ratio of about 40 percent. The 40 percent of MR is quite large. It is considered that this value is geometrically enhanced magnetoresistance due to the low junction resistance of MTJ.