Brief rapid thermal treatment effect on patterned CoFeB-based magnetic tunneling junctions

The brief thermal treatment effects on the magnetoresistance of microstructured Co60 Fe20 B20 -based magnetic tunneling junctions have been studied. The elliptical shape of devices with long/short axis of 42 μm was patterned out of film stack of seed layer (20) PtMn (15) Co60 Fe20 B20 (3) Al (0.7) oxide C60 Fe20 B20 (20) capping layer (48) (thickness unit in nanometers) combining conventional lithography and inductively coupled plasma reactive ion beam etching technologies. The thermal annealing was carried out with device loading into a furnace with preset temperatures ranging from 100 to 400 °C for only 5 min in the absence of any external magnetic field. The magnetoresistance was found to increase with increasing annealing temperatures up to 250 °C and then decrease at higher annealing temperatures. In addition, the magnetoresistance ratio of around 35%, similar to that of as-fabricated devices, sustains up to annealing temperature of 350 °C. This survival of magnetoresistance at higher annealing temperature is due to boron conservation in the amorphous CoFeB ferromagnetic layer at higher annealing temperature for only a short time, which is manifested using x-ray diffractometer technique.