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

In this study, the transient annealing effect on the switching behavior of microstructured Co 60 Fe 20 B 20 ‐based magnetic tunnel junctions has been studied through magnetoresistacne 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. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)