Radical nitridation of Al films for the barrier formation in ferromagnetic tunnel junctions

Abstract Nitridation process of Al films using microwave-excited plasma was investigated to realize highly qualified Al–N barrier for magnetic tunnel junctions (MTJs), in comparison with reactive deposition process of Al–N films. The MTJs fabricated by the plasma nitridation method with Kr+N 2 or Ar+N 2 mixed gas showed larger values of tunnel magnetoresistance (TMR) ratio and resistance–area product ( R × A ) than those of the MTJs fabricated with He+N 2 plasma. The MTJs with reactive-deposited Al–N showed relatively small values of TMR ratio and R × A . From the optical emission spectroscopy of the respective plasma, we concluded that N 2 ion in the plasma is a responsible factor for lowering the barrier height of Al–N and that radical nitridation process is suitable to form the barriers without inducing defects.