Low-current Spin Transfer Torque MRAM

To achieve low write current in high density Spin Transfer Torque Magnetic Random Access Memory (STT-MRAM) arrays, it is important to understand and co-optimize the different kinds of device switching currents, governed by different materials parameters. We demonstrate that double magnetic tunnel junctions (DMTJs) lower the switching current threshold Ic0 by a factor of two when compared to conventional single MTJs. In single MTJs, the overdrive required to reach a write-error rate (WER) of 1E-6 was reduced by materials optimization from 53% to 29% a write-error rate (WER) of 1E-6 by materials optimization. Ultra-low switching current of 8 μA at WER = 1E-9 was achieved in an 11 nm MTJ with 10 ns write pulses.