Magnetic tunnel junctions with a tunnel barrier formed by N2O plasma

Abstract

We investigated a magnetic tunnel junction (MTJ) with a tunnel barrier formed by N2O plasma. Compared with a MTJ with a tunnel barrier formed by conventional O-2 plasma, the MTJ fabricated with N2O plasma shows much lower specific junction resistance and a comparably high tunneling magnetoresistance ratio. In particular, it was found that N2O plasma oxidation is quite important in the junction with a thin tunnel barrier, for which O-2 plasma cannot be used. From x-ray photoelectron spectroscopy, we observed that N2O plasma oxidation leads to the slight nitridation of the Al2O3 layer and significantly reduces the oxidation of the bottom electrode, especially for a thin tunnel barrier. Thus, we conclude that the use of N2O plasma in forming the tunnel barrier is effective for achieving a low junction resistance and for minimizing the oxidation of the bottom electrode during plasma oxidation in MTJs. (C) 2003 American Institute of Physics.