UNIPOLAR-SWITCHING PERPENDICULAR MRAM AND METHOD FOR USING SAME

摘要

MRAM devices that are switched by unipolar electron flow are described. Embodiments use arrays of cells that include a diode or transistor with a pMTJ. The switching between the high and low resistance states of the pMTJ is achieved by electron flow in the same direction, i.e. a unipolar flow. Embodiments of the invention include methods of operating unipolar MRAM devices that include a read step after a write step to verify the operation. Embodiments also include methods of operating unipolar MRAM devices that include an iterative stepped-voltage write process that includes a plurality of write-read steps that begin with a selected voltage for the write pulse for the first iteration and gradually increase the voltage for the write pulse for the next iteration until a successful read operation occurs.

主权项

1. An MRAM device with a memory cell that includes a Magnetic Tunnel Junction (MTJ) coupled to a selecting device, including:
said MTJ having at least one reference layer (RL) with a fixed perpendicular magnetization, at least one free layer (FL) with a switchable perpendicular magnetization, and a junction layer between the reference layer and the free layer, including: a bit line connected to an electrode of the MTJ; and a word line connected to the selecting device; and wherein a first write process switches the free layer magnetization from anti-parallel to the reference layer magnetization to parallel to the reference layer magnetization by applying a first voltage pulse having a first amplitude between the bit line and the word line; and wherein a second write process switches the free layer magnetization from parallel to the reference layer magnetization to anti-parallel to the reference layer magnetization by applying a second voltage pulse having a second amplitude between the bit line and the word line; the first and second voltage pulses inducing electrons to move from the reference layer to the free layer, and the second amplitude being higher than the first amplitude.