Perpendicular MTJ stacks with magnetic anisotropy enhancing layer and crystallization barrier layer
Magnetic tunnel junctions (MTJ) suitable for spin transfer torque memory (STTM) devices, include perpendicular magnetic layers and one or more anisotropy enhancing layer(s) separated from a free magnetic layer by a crystallization barrier layer. In embodiments, an anisotropy enhancing layer improves perpendicular orientation of the free magnetic layer while the crystallization barrier improves tunnel magnetoresistance (TMR) ratio with better alignment of crystalline texture of the free magnetic layer with that of a tunneling layer.
1. A perpendicular magnetic tunneling junction (MTJ), comprising:
a free magnetic layer having perpendicular magnetic anisotropy;
a fixed magnetic layer;
a tunneling layer disposed between the free magnetic layer and the fixed magnetic layer; a magnetic anisotropy enhancing layer disposed on a side of the free magnetic layer opposite the tunneling layer; and
a crystallization barrier layer disposed between the magnetic anisotropy enhancing layer and the free magnetic layer.
2. The MTJ of claim 1 , wherein the crystallization barrier layer is in direct contact with the free magnetic layer and has a different microstructure than that of the magnetic anisotropy enhancing layer.
3. The MTJ of claim 2 , wherein the free magnetic layer and tunneling layer has (001) crystal texture, wherein the magnetic anisotropy enhancing layer includes a material layer having (111) crystal texture, and wherein the crystallization barrier layer includes a material layer with amorphous microstructure, or (001) crystal texture, forming an interface with the free magnetic layer.
4. The MTJ of claim 3 , wherein the barrier layer comprises at least one of: Ta, Ru, W, V, Mo, Nb, or Cr.
5. The MTJ of claim 4 , wherein the barrier layer further comprises B.
6. The MTJ of claim 4 , wherein the thickness of the barrier layer is between 0.1 nm and 1.3 nm.
7. The MTJ of claim 1 , wherein the magnetic anisotropy enhancing layer comprises a stack of magnetic and non-magnetic material layers, and wherein a magnetic layer of the stack is more proximate to the free magnetic layer than is any non-magnetic material layer of the stack.
8. The MTJ of claim 7 , wherein the tunneling layer comprises MgO or AlOx, wherein the free magnetic layer comprises iron-rich CoFeB having a thickness over 1.0 nm, and wherein the non-magnetic material layers of the stack comprise at least one of Pd, Pt, Ru, Au, or Ir and wherein the magnetic material layers of the stack comprise at least one of Co, Ni, or Fe.
9. The MTJ of claim 3 , wherein the crystallization barrier layer further includes a second material layer with a composition other than that of the material layer forming the interface with the free magnetic layer.
10. A non-volatile memory device, comprising:
a first electrode; a fixed magnetic layer disposed over the first electrode;
a free magnetic layer comprising CoFeB disposed over the fixed magnetic layer, wherein the free magnetic layer has (001) crystal texture, and a thickness greater than 1.0 nm; a tunneling layer with (001) crystal texture disposed between the free magnetic layer and the fixed magnetic layer;
a magnetic anisotropy enhancing layer including a material layer having (111) crystal texture disposed on a side of the free magnetic layer opposite the tunneling layer; a crystallization barrier layer disposed between the magnetic anisotropy enhancing layer and the free magnetic layer, wherein the crystallization barrier layer includes a material layer with amorphous microstructure, or (001) crystal texture forming an interface with the free magnetic layer;
a second electrode disposed over the magnetic anisotropy enhancing layer; and
a transistor electrically connected to the first or the second electrode, a source line, and a word line.
11. The non-volatile memory device of claim 10 , wherein the magnetic anisotropy enhancing layer comprises a stack of magnetic and non-magnetic material layers, and wherein a magnetic layer of the stack is more proximate to the free magnetic layer than is any non-magnetic material layer of the stack.
12. The non-volatile memory device of claim 11 , wherein the barrier layer comprises at least one of: Ta, Ru, W, V, Mo, Nb, or Cr and has a thickness between 0.1 nm and 1.3 nm.
13. The non-volatile memory device of claim 12 , wherein the crystallization barrier layer comprises Ta and B and has a thickness less than 0.7 nm.
14. The non-volatile memory device of claim 12 wherein the crystallization barrier layer further includes a second material layer with a composition other than that of the material layer forming the interface with the free magnetic layer.
15. A mobile computing platform comprising: the non-volatile memory device of claim 10 , a display screen; and a wireless transceiver.