Effect of inductively coupled plasma oxidation on properties of magnetic tunnel junctions

Abstract

Magnetic tunnel junctions consisting of Ta(50 Å)/NiFe(50 Å)/IrMn(150 Å)/CoFe(50 Å)/Al(13 Å) –O/CoFe(40 Å)/NiFe(400 Å)/Ta(50 Å) with a 100×100 μm2 junction area were prepared. The AlOx tunnel barrier was produced by oxidizing the 13 Å thick Al metal using inductively coupled plasma (ICP) for 30–360 s and the ensuing junction properties were characterized as a function of oxidation time. It was found that a junction oxidized for 80 sec exhibited the highest magnetoresistance ratio, 30.3%, at room temperature. It was also shown that the junctions with an ICP oxidized tunnel barrier maintained the tunneling magnetoresistance ratio over 15% even when the insulator layer was oxidized for a prolonged period, well beyond the optimal oxidation time. The large processing window for the insulator oxidation was attributed to the dense amorphous AlOx structure formed by the ICP oxidation.

Magnetotransport properties and thermal stability of magnetic tunnel junctions with wave resonance plasma oxidized barrier

“…It is typically formed by oxidizing an ultra-thin Al film in a directly coupled DC or RF oxygen glow discharge [6][7][8] and in an inductively coupled oxygen plasma [9,10], respectively, partly with admixtures of argon, too. These discharges are able to produce a significant dissociation of oxygen molecules resulting in an extremely high plasma reactivity.…”