Electrical breakdown of the magnetic tunneling junction with an AlOx barrier formed by radical oxidation

Abstract

In this work, the dielectric breakdown in magnetic tunnel junctions (MTJs) was studied. The MTJ structure is $\mathrm{Ta50/NiFe100/Co20/AlO}\mathrm{x/}\mathrm{Co30/RuRhMn100/Ta50}$ with the bottom lead of Ta50/Cu500/Ta50 and the top lead of Cu2000/Ta50 (in Å), where the tunneling barrier was formed by 2–20 min radical oxygen oxidation of a 10 Å-thick Al layer. The junctions with area from $\text{2×2}$ to $\text{20×20\hspace{0.05em}μ}{\mathrm{m}}^{\mathrm{2}}$ were patterned using the photolithography process, leading to tunneling magnetoresistance up to 17.2% and resistance-area product ranging from 350 Ω μm² to 200 kΩ μm². The junctions studied show dc breakdown voltage from 0.7 to 1.3 V, depending on the junction area and the oxidation time. Long oxidation time up to 14 min and a small junction area results in a large dc breakdown voltage. The electrostatic discharge (ESD) of MTJs was tested by using a human body model. The ESD breakdown voltage increases with decreasing junction resistance. These results are discussed in terms of the E-model based on the field-induced distortion of atomic bonds in the oxide barrier.