Effect of transient annealing on patterned CoFeB-based magnetic tunnel junctions

In this study, the transient annealing effect on the switching behavior of microstructured Co60Fe20B20-based magnetic tunnel junctions has been studied through magnetoresistance measurements (R-H loop). Elliptical shape of devices with long/short axis of 4/2 micrometers was patterned out of sheet film stack of: Ta(20)/PtMn(15)/CoFeB(3)/Al(0.7)-oxide/CoFeB(2)/Ru(8)/Ta(40) (thickness unit in nanometers) after a conventional long time field cooling annealing. The transient annealing was then executed by sample loading into a furnace with pre-set temperatures ranging from 100 to 400 C for only 5 minutes in the absence of any external magnetic field. The vortex-like reverse of free layer in as-etched MTJ evidently changes to single-domain-like reverser after 200∝250 C transient annealing. The magnetoresistance was found to increase with increasing annealing temperatures up to 265 C and then slowly decrease at higher annealing temperatures. The transient thermal annealing creates obvious efforts to repair magnetic properties of MTJ cell befor 265 C annealing and results in less damage at temperature of 350 C and 400 C. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)