Effect of Plasma Oxidation on Pre-Oxidized Magnetic Tunnel Junctions

The technique of pre-oxidation of the bottom CoFe electrode prior to deposition of Al₂O₃ was previously shown to be capable of suppressing intermixing at the ferromagnet/Al interface and removing partial shorts near Al grain boundaries. In this paper, we studied the influence of the plasma oxidation on the pre-oxidized magnetic tunnel junctions (MTJs). In general, the tunneling magnetoresistance (TMR) is independent of the plasma oxidation time whereas the resistance-area product (RA) increases with it. However, for the pre-oxidized MTJs with very thin Al₂O₃ (Al thickness < 0.7 nm prior to plasma oxidation), the TMR decreases with plasma oxidation while the RA increases with it.