Mn diffusion in the plasma oxidized AlOx insulation layer in the magnetic tunnel junctions

The extent of Mn diffusion to the plasma-oxidized AlOx tunnel barrier in the magnetic tunnel junctions is explored using Rutherford backscattering spectroscopy (RBS) and Auger electron spectroscopy (AES). A thin film stack consisting of Ta/AlOx/CoFe/IrMn/NiFe/Ta is deposited with the AlOx layer treated under different plasma oxidation durations. When the film stack is annealed at 300 degreesC, RBS and AES analysis showed that the Mn diffusion to the AlOx layer progressively increased as the tunnel barrier layer is overoxidized. The Mn diffusion appears to be enhanced and controlled by the presence of the oxygen near the tunnel barrier due to the relatively high oxygen affinity of Mn. This observation implicates that the oxidation condition of the tunnel barrier not only determines the as-deposited state of the junction, but also has a large bearing on the thermal stability of the exchange-biased tunnel junctions. (C) 2002 American Institute of Physics.