Effect of nitrogen incorporation to oxidation process on the reliability of magnetic tunnel junctions

In this study, nitrogen atoms are added in a post-oxidation process of a thin Al metal layer to enhance the stability of magnetic tunnel junctions (MTJs). Al-N bonds in the tunnel barrier were detected by XPS measurements. The MTJs fabricated by an ultra-high vacuum magnetron sputtering system consisted of Si(100)/SiO₂/CoFeB(100 Å)/Cu(250 Å)/CoFe(50 Å)/AIO_x or AlO_xN_y(20 Å)/CoFe(25 Å)/IrMn(200 Å)/Cu(300 Å). The lifetimes of the two barriers were predicted in order to see the nitrogen effect on the reliability. Under the lifetime specification of 1 MTJ failure out of 10¹² junctions, the operating voltage of 0.24 V was obtained for the purely oxidized barriers while 0.42 V of operating voltages for the oxy-nitrided barriers.