H. Kyung et al., Oxidation mechanism of the insulation layer in NiFe/Co/Al(Ta)-oxide/Co magnetic tunnel junctions, MAT SCI E B, 83(1-3), 2001, pp. 192-197
Ferromagnetic tunneling junctions with Al-oxide and Ta-oxide as the insulat
ing layer were fabricated using metal mask and Inductively Coupled Plasma (
ICP) sputtering system. To interpret growth mechanism of the insulating lay
er during plasma oxidation process, the microstructure of the oxide layers
was investigated with cross-sectional TEM. TEM analysis showed Al-oxide had
different microstructures depending on the thickness of the layer. At 13 A
ngstrom, the Al-oxide layer was flat while the Al-oxide layer became progre
ssively wavy with regular periodicity of 20 nm at increasing oxide thicknes
s. Ta-oxide layer was partially oxidized under equal oxidizing conditions.
but remained flat regardless of the thickness. Growth mechanism for the two
different oxide layers is proposed in terms of oxidation kinetics and oxyg
en plasma. (C) 2001 Elsevier Science B.V. All rights reserved.