Ferromagnetic coupling field reduction in CoFeB tunnel junctions deposited by Ion Beam

In this work, junctions with reduced Hf coupling were fabricated by ion beam deposition and oxidation, using CoFeB electrodes. The CoFeB layer has a strong (110) texture that can be the origin of lower Hf and coercivity when compared with CoFe. Junctions processed down to 2x4 um2 with 40Å thick CoFeB bottom electrodes have 42% of tunneling magnetoresistance (TMR), (R x A ~400 Ohm um2), Hc of ~10 Oe and Hf of ~2 Oe. CoFe-based junctions (R x A ~500W Ohm um2) have lower TMR (~35%) and larger Hf (~5-6 Oe) and Hc (~12-14 Oe). Local chemical composition analysis of the cross section indicated Fe-O segregation without Co grown on top of the barrier for CoFe-based junctions and not for CoFeB ones.