Lifetime of magnetic tunnel junctions under voltage stress

Summary form only given. Magnetic tunnel junctions (MTJ) are being investigated for possible application in magnetic sensors and memories. Due to the thin tunnel barrier, the junctions are very sensitive to electrical breakdown and degradation. This paper describes the lifetime of junctions under voltage stress with extrapolation to use conditions assuming an exponential acceleration factor. The tunneling films were deposited with a DC magnetron sputtering system. The aluminum layer is plasma oxidized in an oxidation module to form an Al/sub 2/O/sub 3/ tunneling barrier. Aluminum thickness, oxidation times, and plasma powers were used to create barriers of different thickness. The film structure is NiFe/PtMn/CoFe/Ru/CoFe/AlO/CoFe/NiFe/Ta. The TMR response of the junction decreases with voltage resulting in a peak for the TMR signal versus voltage. The acceleration factor calculated in stress testing can be used to estimate the junction lifetime at the optimum operating voltage.