Spin-transfer torque magnetic random access memory (STTMRAM) using a synthetic free layer
View Patent ↗A spin-torque transfer memory random access memory (STTMRAM) element, employed in a STTMRAM array, receives electric current for storage of digital information, the STTMRAM element has a magnetic tunnel junction (MTJ). The MTJ includes an anti-ferromagnetic (AF) layer, a fixed layer having a magnetization that is substantially fixed in one direction and that comprises a first magnetic layer, an AF coupling layer and a second magnetic layer, a barrier layer formed upon the fixed layer, and a free layer. The free layer is synthetic and has a high-polarization magnetic layer, a low-crystallization magnetic layer, a non-magnetic separation layer, and a magnetic layer, wherein during a write operation, a bidirectional electric current is applied across the STTMRAM element to switch the magnetization of the free layer between parallel and anti-parallel states relative to the magnetization of the fixed layer.
1. A spin-torque transfer memory random access memory (STTMRAM) element, employed in a STTMRAM array, where the STTMRAM element received electric current for storage of digital information, the STTMRAM element comprising:
a magnetic tunnel junction (MTJ) including,
an anti-ferromagnetic (AF) layer;
a fixed layer having a magnetization that is substantially fixed in one direction and that comprises a first magnetic layer, an AF coupling layer and a second magnetic layer;
a barrier layer formed upon the fixed layer;
a free layer is synthetic and comprised of a high-polarization magnetic layer, a low-crystallization magnetic layer, a non-magnetic separation layer, and a magnetic layer;
wherein during a write operation, a bidirectional electric current is applied across the STTMRAM element to switch the magnetization of the free layer between parallel and anti-parallel states relative to the magnetization of the fixed layer.
2. The STTMRAM element, as recited in claim 1 , wherein the high-polarization magnetic layer is made from CoFeB.
3. The STTMRAM element, as recited in claim 1 , wherein the high-polarization magnetic layer has a thickness greater than 0.4 nano meters.
4. The STTMRAM element, as recited in claim 1 , wherein the low crystallization layer is comprised of a magnetic alloy of a composition of CoxFe(1-x)ByZ wherein x is between 20-80 atomic percent, and y is between 10-30 atomic percentage, and Z is less than 25 atomic percent of one or more of titanium, yttrium, zirconium, and vanadium.
5. The STTMRAM element, as recited in claim 1 , wherein the non-magnetic separation layer is conducting or non-conducting.
6. The STTMRAM element, as recited in claim 1 , wherein the non-magnetic separation layer is a conductor metal made from copper, tantalum, or ruthenium.
7. The STTMRAM element, as recited in claim 1 , wherein the non-magnetic separation layer is made of an insulating material comprising: magnesium oxide, titanium dioxide, zirconium oxide, or ruthenium oxide or strontium oxide.
8. The STTMRAM element, as recited in claim 1 , wherein the non-magnetic separation layer has a thickness between 0.5 and 5.0 nano meters.
9. The STTMRAM element, as recited in claim 1 , wherein the magnetic layer is made from CoFeB.
10. The STTMRAM element, as recited in claim 1 , wherein the low-crystallization magnetic layer and the magnetic layer of the free layer each have a magnetization and further wherein, the magnetization of the low-crystallization magnetic layer of the free layer is opposite to that of the magnetic layer of the free layer.
11. The STTMRAM element, as recited in claim 1 , wherein the low-crystallization magnetic layer has a composition of Co30Fe40B20Ti10 atomic percent.
12. The STTMRAM element, as recited in claim 1 , wherein the low-crystallization magnetic layer has a composition of Co45Fe25B20Ti10 atomic percent.
13. The STTMRAM element, as recited in claim 1 , wherein the barrier layer has a thickness between 0.5 and 2.0 nano meters.
14. The STTMRAM element, as recited in claim 1 , wherein the barrier layer is made of a material comprising: magnesium oxide, ruthenium oxide, strontium oxide, zinc oxide, aluminum oxide, or titanium oxide.
15. A spin-torque transfer memory random access memory (STTMRAM) element, employed in a STTMRAM array, where the STTMRAM element received electric current for storage of digital information, the STTMRAM element comprising:
a magnetic tunnel junction (MTJ) including,
an anti-ferromagnetic (AF) layer;
a fixed layer having a magnetization that is substantially fixed in one direction and that comprises a first magnetic layer, an AF coupling layer and a second magnetic layer;
a barrier layer formed upon the fixed layer;
a free layer is comprised of a low-crystallization magnetic layer, a non-magnetic layer, and a magnetic layer;
wherein during a write operation, a bidirectional electric current is applied across the STTMRAM element to switch the magnetization of the free layer between parallel and anti-parallel states relative to the magnetization of the fixed layer.
16. The STTMRAM element, as recited in claim 15 , wherein the non-magnetic layer is made of material comprising: Ta, Ti, Mo, Cr, or V.
17. The STTMRAM element, as recited in claim 15 , wherein the non-magnetic layer is made of material comprising: oxides or nitrides from aluminum oxide (Al2O3), titanium oxide (TiO2), tantalum oxide (Ta2O5), hafnium oxide (HfO2), zirconium oxide (ZrO2), tungsten oxide (WO), niobium oxide (Nb2O5), chromium oxide (Cr2O3), silicon oxide (SiO2), yitrium oxide (Y2O3), vanadium oxide (VO2), Ruthenium oxide (RuO), Strontium oxide (SrO), Zinc oxide (ZnO), Magnesium oxide (MgO), titanium nitride (TiN), tantalum nitride (TaN), aluminum nitride (AlN), or silicon nitride (SiN).
18. The STTMRAM element, as recited in claim 15 , wherein the non-magnetic layer has a thickness below 1 nano meters.
19. The STTMRAM element, as recited in claim 18 , wherein the non-magnetic layer has a thickness below 0.1-0.5 nano meters.
20. A spin-torque transfer memory random access memory (STTMRAM) element, employed in a STTMRAM array, where the STTMRAM element received electric current for storage of digital information, the STTMRAM element comprising:
a magnetic tunnel junction (MTJ) including,
an anti-ferromagnetic (AF) layer;
a fixed layer having a magnetization that is substantially fixed in one direction and that comprises a first magnetic layer, an AF coupling layer and a second magnetic layer;
a barrier layer formed upon the fixed layer;
a free layer comprised of a low-crystallization temperature magnetization layer made of a magnetic alloy of composition CoxFe (1-x)ByZ, where ‘x’ is between 20-80 atomic percent, and ‘y’ is between 10-30 atomic percent, and ‘Z’ is less than 25 atomic percept of one or more of the following materials: titanium, yttrium, zirconium, and vanadium, the free layer having a magnetization that is switchable;
wherein during a write operation, a bidirectional electric current is applied across the STTMRAM element to switch the magnetization of the free layer between parallel and anti-parallel states relative to the magnetization of the fixed layer.
21. The STTMRAM element of claim 20 , wherein the low-crystallization temperature magnetization layer has a composition of Co30Fe40B20Ti10.
22. The STTMRAM element, as recited in claim 1 , wherein the low-crystallization magnetic layer has a composition of Co45Fe25B20Ti10 atomic percent.