Spin-transfer torque magnetic random access memory (STTMRAM) with perpendicular laminated free layer
View Patent ↗A perpendicular spin transfer torque magnetic random access memory (STTMRAM) element includes a fixed layer having a magnetization that is substantially fixed in one direction and a barrier layer formed on top of the fixed layer and a free layer. The free layer has a number of alternating laminates, each laminate being made of a magnetic layer and an insulating layer. The magnetic layer is switchable and formed on top of the barrier layer. The free layer is capable of switching its magnetization to a parallel or an anti-parallel state relative to the magnetization of the fixed layer during a write operation when bidirectional electric current is applied across the STTMRAM element. Magnetic layers of the laminates are ferromagnetically coupled to switch together as a single domain during the write operation and the magnetization of the fixed and free layers and the magnetic layers of the laminates have perpendicular anisotropy.
1. A spin-torque transfer memory random access memory (STTMRAM) element formed on a substrate comprising:
a fixed layer having a magnetic orientation that is perpendicular relative to the substrate, the fixed layer having a perpendicular magnetic layer on top of which is formed a magnetic layer;
a barrier layer formed on top of the fixed layer;
a free layer, the free layer having a magnetic orientation that is perpendicular relative to the substrate further having ‘n’ number of alternating laminates, ‘n’ being greater than one, a laminate made of a magnetic layer and an insulating layer, the magnetic layer being switchable and formed on top of the barrier layer, the free layer capable of switching its magnetization to a parallel or an anti-parallel state relative to the magnetization of the fixed layer during a write operation when bidirectional electric current is applied across the STTMRAM element, the free layer further including a perpendicular magnetic layer formed on top of the ‘n’ number of alternating laminates.
2. The STTMRAM element, as recited in claim 1 , further including an underlayer on top of which is formed the fixed layer.
3. The STTMRAM element, as recited in claim 2 , further including a seed layer on top of which is formed the underlayer.
4. The STTMRAM element, as recited in claim 1 , wherein the magnetic layer of at least one of the laminates is made of an alloy of cobolt iron boron (CoxFe(1-x)Bz) where x is greater than 10 atomic percent, and z is greater than 12 at %.
5. The STTMRAM element, as recited in claim 4 , wherein the magnetic layers of each of the laminates other than the at least one of the laminates is made of one or more of CoFeY, Nickel Iron (NiFeY) or CoFeNiY where Y is chosen from one or more of boron (B), phosphorus (P), carbon (C), nitrogen (N), chromium (Cr), tantalum (Ta), titanium (Ti), niobium (Nb), Zirconium (Zr), tungsten (W), silicon (Si), copper (Cu), Rhodium (Rh), or hafnium (Hf).
6. The STTMRAM element, as recited in claim 4 , wherein the magnetic layers of each of the laminates other than the at least one of the laminates is made of a CoFe-based alloy.
7. The STTMRAM element, as recited in claim 4 , wherein the magnetic layers of each of the laminates other than the at least one of the laminates is made of alloys comprising: cobolt iron tantalum (CoFeTa), cobolt iron zirconium (CoFeZr), or cobolt iron hafnium (CoFeHf).
8. The STTMRAM element, as recited in claim 1 , wherein at least one of the magnetic layers of the laminates has a thickness of between 0.2 to 1.5 nano meters.
9. The STTMRAM element, as recited in claim 1 , wherein the insulating layer of each of the laminates is made of Magnesium oxide (MgO) and the magnetic layers of each of the laminates is made of CoFeB.
10. The STTMRAM element, as recited in claim 1 , wherein at least one of the magnetic layers of the laminates has a thickness between 0.4 to 1.2 nano meters.
11. The STTMRAM element, as recited in claim 1 , wherein the free layer further includes a perpendicular magnetic layer formed on top of the laminates.
12. The STTMRAM element, as recited in claim 11 , wherein the perpendicular magnetic layer of the fixed layer and the perpendicular magnetic layer of the free layer are each comprised of multi-layers of Co and Pt or Pd.
13. The STTMRAM element, as recited in claim 11 , wherein the perpendicular magnetic layer of the fixed layer and the perpendicular magnetic layer of the free layer is comprised of FePtCuB.
14. A spin-torque transfer memory random access memory (STTMRAM) element formed on a substrate comprising:
a fixed layer having a magnetization that is substantially fixed in one direction, the fixed layer having a magnetic orientation that is perpendicular relative to the substrate, the fixed layer having a perpendicular magnetic layer on top of which is formed a magnetic layer with the magnetic layer having an in-plane magnetic anisotropy with the strong perpendicular anisotropy of the perpendicular magnetic layer causing the magnetic layer it to be oriented perpendicular to the substrate;
a barrier layer formed on top of the fixed layer;
a free layer, the free layer having a magnetic orientation that is perpendicular relative to the substrate further having ‘n’ number of alternating laminates, ‘n’ being greater than one, a laminate made of a magnetic layer and an insulating layer, the magnetic layer being switchable and formed on top of the barrier layer, the free layer capable of switching its magnetization to a parallel or an anti-parallel state relative to the magnetization of the fixed layer during a write operation when bidirectional electric current is applied across the STTMRAM element, the free layer further including a perpendicular magnetic layer formed on top of the ‘n’ number of alternating laminates.
15. The STTMRAM element, as recited in claim 14 , further including an underlayer on top of which is formed the fixed layer.
16. The STTMRAM element, as recited in claim 14 , further including a seed layer on top of which is formed the underlayer.
17. The STTMRAM element, as recited in claim 14 , wherein the magnetic layer of at least one of the laminates is made of an alloy of cobolt iron boron (CoxFe(1-x)Bz) where x is greater than 10 atomic percent, and z is greater than 12 at %.
18. The STTMRAM element, as recited in claim 17 , wherein the magnetic layers of each of the laminates other than the at least one of the laminates is made of one or more of CoFeY, Nickel Iron (NiFeY) or CoFeNiY where Y is chosen from one or more of boron (B), phosphorus (P), carbon (C), nitrogen (N), chromium (Cr), tantalum (Ta), titanium (Ti), niobium (Nb), Zirconium (Zr), tungsten (W), silicon (Si), copper (Cu), Rhodium (Rh), or hafnium (Hf).
19. The STTMRAM element, as recited in claim 17 , wherein the magnetic layers of each of the laminates other than the at least one of the laminates is made of a CoFe-based alloy.
20. The STTMRAM element, as recited in claim 17 , wherein the magnetic layers of each of the laminates other than the at least one of the laminates is made of alloys comprising: cobolt iron tantalum (CoFeTa), cobolt iron zirconium (CoFeZr), or cobolt iron hafnium (CoFeHf).
21. The STTMRAM element, as recited in claim 14 , wherein at least one of the magnetic layers of the laminates has a thickness of between 0.2 to 1.5 nano meters.
22. The STTMRAM element, as recited in claim 14 , wherein the insulating layer of each of the laminates is made of Magnesium oxide (MgO) and the magnetic layers of each of the laminates is made of CoFeB.
23. The STTMRAM element, as recited in claim 14 , wherein at least one of the magnetic layers of the laminates has a thickness between 0.4 to 1.2 nano meters.
24. The STTMRAM element, as recited in claim 14 , wherein the free layer further includes a perpendicular magnetic layer formed on top of the laminates.
25. The STTMRAM element, as recited in claim 24 , wherein the perpendicular magnetic layer of the fixed layer and the perpendicular magnetic layer of the free layer are each comprised of multi-layers of Co and Pt or Pd.
26. The STTMRAM element, as recited in claim 24 , wherein the perpendicular magnetic layer of the fixed layer and the perpendicular magnetic layer of the free layer is comprised of FePtCuB.