Magnetic memory devices having a low switching voltage
AssigneeNorthwestern University
InventorPedram Khalili Amiri
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Abstract
A voltage-controlled magnetic anisotropy (VCMA) magnetic tunnel junction (MTJ) device includes a bottom electrode, a bottom CoFeB fixed layer disposed above and in electrical communication with the bottom electrode, a MgO layer disposed above the bottom CoFeB fixed layer, a top CoFeB free layer disposed above the MgO layer, a Mo capping layer disposed above the top CoFeB free layer, and a top electrode disposed above and in electrical communication with the Mo capping layer. A magnetization state of the top CoFeB free layer is switchable between an original state and an opposite state by applying a switching voltage across the MTJ device for a switching duration corresponding to a half period of a magnetic moment precession of the top CoFeB free layer.
Claims19
A magnetic tunnel junction (MTJ) device, comprising:
- a bottom electrode;
- a bottom CoFeB fixed layer disposed above and in electrical communication with the bottom electrode;
- a MgO layer disposed above the bottom CoFeB fixed layer;
- a top CoFeB free layer disposed above the MgO layer;
- a metal Mo capping layer disposed above the top CoFeB free layer;
- and
- a top electrode disposed above and in electrical communication with the metal Mo capping layer.
A method of fabricating a voltage-controlled magnetic anisotropy (VCMA) magnetic tunnel junction (MTJ) device, comprising:
- forming a plurality of layers in a perpendicularly rising sequence above a bottom electrode, the plurality of layers comprising a bottom CoFeB fixed layer disposed above and in electrical communication with the bottom electrode, a MgO layer disposed above the bottom CoFeB fixed layer, a top CoFeB free layer disposed above the MgO layer, a metal Mo capping layer disposed above the top CoFeB free layer, and a top electrode disposed above and in electrical communication with the metal Mo capping layer;
- performing thermal annealing;
- and
- patterning the plurality of layers into a circular pillar.
A method of switching a free-layer magnetization state of a voltage-controlled magnetic anisotropy (VCMA) magnetic tunnel junction (MTJ) device patterned as a circular pillar comprising a plurality of layers in arranged in a perpendicularly rising sequence above a bottom electrode, the plurality of layers including a bottom CoFeB fixed layer disposed above and in electrical communication with the bottom electrode, a MgO layer disposed above the bottom CoFeB fixed layer, a top CoFeB free layer disposed above the MgO layer, a metal Mo capping layer disposed above the top CoFeB free layer and in electrical communication with a top electrode thereabove, the method comprising:
- applying a magnetic field H across the top CoFeB free layer of the MTJ device along an axis;
- applying a switching voltage VSW between the top electrode and the bottom electrode of the MTJ device, where VSW=4tMgOEb(V=0)/(πξD2), tMgO is a thickness of the MgO layer, Eb is an energy barrier between two free-layer magnetization states, ξ is a VCMA coefficient, and D is a diameter of the MTJ device;
- and
- removing the switching voltage VSW after the switching voltage VSW has been applied for a switching time tSW corresponding to a half period of a magnetic moment precession of the top CoFeB free layer.
Dependencies are inferred from the claim text.