Enhanced reliability of magnetic tunnel junctions with thermal annealing

Abstract

Time-dependent dielectric breakdown (TDDB) of magnetic tunnel junctions (MTJs) under a constant Voltage stress, tunneling magnetoresistance (TMR), and barrier properties, e.g. effective barrier height and thickness, were investigated as a function of thermal annealing temperatures. A Weibull failure distribution function was plotted in terms of time to breakdown (T-BD) of MTJs. The T-BD when 63% fraction of as-fabricated MTJs cumulatively failed increased significantly after thermal annealing at 210 degreesC while the TMR also increased from 8.85% to 14.22% before and after thermal annealing at 210 degreesC, respectively. We believe that the enhanced reliability of the MTJs is due to healing effect of bulk defects in the barrier during the annealing process, likely leading to the reduction of defect trap density. The reduction of bulk defects in the barrier was also confirmed by the lowered 1/f noise power spectral density from voltage fluctuation measurements. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.