Ferromagnetic coupling field reduction in CoFeB tunnel junctions deposited by ion beam

In this paper, junctions with reduced [H.sub.f] coupling were fabricated by ion beam deposition and oxidation, using CoFeB electrodes. The CoFeB layer has a strong (111) texture that can be the origin of lower [H.sub.f] and coercivity when compared with CoFe. Junctions processed down to 2 x 4/[micro][m.sup.2] with 40-[Angstrom]-thick CoFeB bottom eiectrodes have 42% of tunneling magnetoresistance (TMR), (R x A ~ 400 [OMEGA]x[micro][m.sup.2]), [H.sub.c] of ~10 Oe and [H.sub.f] of ~2 Oe. CoFe-based junctions (R x A ~ 500 [OMEGA]x[micro][m.sup.2]) have lower TMR (~35%) and larger [H.sub.f] (~5-6 Oe) and [H.sub.c] (~12-14 Oe). Local chemical composition analysis of the cross section indicated Fe-O segregation with very little Co grown on top of the barrier for CoFe-based junctions and not for CoFeB ones. Index Terms--CoFeB electrodes, ion beam deposition, low ferromagnetic coupling, tunnel junctions.