Dependence of magnetic tunnel junction properties on tunnel barrier roughness

Abstract

Magnetic tunnel junctions (MTJs) consisting of Si/SiO(2)/Ta/Ru/IrMn/CoFe/Ru/CoFe/Al-O/CoFe/NiFe/Ru with different surface roughness of bottom electrode were prepared, and the dependence of tunneling magnetoresistance (TMR) ratio and resistance area product (RA) on surface roughness of tunnel barrier and the tunneling characteristics of these junction devices were investigated. The MTJ with rough tunnel barrier of 12 angstrom root mean square roughness (R(rms)) showed TMR ratio of 4% and RA of 2.2 k Omega mu m(2). In contrast, the MTJ with uniform tunnel barrier of R(rms) = 3 angstrom showed TMR ratio of 40% and RA of 14 k Omega mu m(2). As MTJs had more uniform tunnel barrier, TMR ratio and resistance were higher, while the interlayer coupling field decreased. It was confirmed that the smooth surface of bottom electrode was a basic requirement for MTJs. (C) 2006 Elsevier B.V. All rights reserved.