Spin dependent tunneling devices fabricated for magnetic random access memory applications using latching mode

Abstract

Spin dependent tunneling (SDT) devices were fabricated as building blocks for magnetic random access memory (MRAM) applications using latching electronics. The basic SDT structure was NiFeCo/Al2O3/CoFe/IrMn deposited using rf diode sputtering. The SDT structures and the word and torque coils were patterned using standard photolithography techniques. The junction magnetoresistance was 25.6%, the switching field was 12 Oe, the junction resistance-area product was 116 kΩ μm2, and the pinning field was 150 Oe. There were two legs of SDT resistors in a latch cell, with each leg consisting of at least one pair of junctions. The basic latching function of the devices was evaluated using external electronics. The two memory states per cell were demonstrated by passing a current of 22 mA with both polarities through the on-chip word coil. This translates to a field efficiency of about 1 Oe/mA for the word coil, which can be further improved by adding a magnetic keeper layer. The raw output voltage change was 21 mV for a SDT cell with four junctions and 4.5 kΩ resistance in each leg using a 50 μA sense current. These results show great potential for SDT materials to be used in high speed and low power MRAM applications with latching mode.