Low-crystallization temperature MTJ for spin-transfer torque magnetic random access memory (STTMRAM)

• US 8,422,286 B2
• Filed: 04/02/2012
• Issued: 04/16/2013
• Est. Priority Date: 10/20/2009
• Status: Active Grant

• Current Assignee: Avalanche Technology Incorporated
• Original Assignee: Avalanche Technology Incorporated
• Inventors: Ranjan, Rajiv Yadav, Malmhall, Roger Klas
• Primary Examiner(s): Byrne, Harry W
• Application Number:
  US13/437,908
• Publication Number:
  US 20120188818A1
• Time in Patent Office: 379 Days
• Field of Search: 365/48, 365/55, 365/62, 365/66, 365/74, 365/78, 365 80- 93, 365/100, 365/130, 365/131, 365/148, 365/158, 365171-173, 365/209, 365/213, 365/225.5, 365/230.07, 365/232, 365/243.5, 216/22, 257/421, 257/E21.665, 438/3, 428810-816, 428817-8251, 428/826, 977933-935
• US Class Current: 365/171
• CPC Class Codes: G11C 11/161 details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• CPC Class Codes: Y10S 977/933 Spintronics or quantum computing

Abstract

A spin-torque transfer memory random access memory (STTMRAM) element is disclosed and has a fixed layer, a barrier layer formed upon the fixed layer, and a free layer comprised of a low-crystallization temperature alloy of CoFeB—Z where Z is below 25 atomic percent of one or more of titanium, (Ti), yittrium (Y), zirconium (Zr), and vanadium (V), 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.

Claims

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 comprised of a low-crystallization temperature magnetization layer made of an alloy of CoFeB—

Z where Z is made of one or more of titanium, (Ti), yittrium (Y), zirconium (Zr), and vanadium (V), 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.

2. The STTMRAM element, as recited in claim 1, further including a cap layer formed on top of the free layer of the MTJ.

3. The STTMRAM element, as recited in claim 2, further including an underlayer on top of which is formed the an anti-ferromagnetic (AF) coupling layer.

4. The STTMRAM element, as recited in claim 3, wherein the underlayer is made of tantalum (Ta).

5. The STTMRAM element, as recited in claim 3, wherein the AF coupling layer is made of platinum manganese (PtMn), iridium manganese (IrMn), nickel manganese (NiMn) or iron manganese (FeMn).

6. The STTMRAM element, as recited in claim 1, wherein the first and second magnetic layers of the fixed layer each have ferromagnetic characteristic and an anti-parallel magnetization orientation relative to each other.

7. The STTMRAM element, as recited in claim 1, wherein the first and second magnetic layers of the fixed layer are each ferromagnetic and separated from each other by ruthenium (Ru).

8. The STTMRAM element, as recited in claim 1, wherein the free layer further includes a third magnetic layer formed between the low-crystallization temperature magnetization layer and the barrier layer.

9. The STTMRAM element, as recited in claim 8, wherein the third magnetic layer is made of the alloy cobolt iron boron (CoFeB) and the low-crystallization temperature magnetization layer is made of titanium (Ti).

10. The STTMRAM element, as recited in claim 8, wherein the third magnetic layer and the low-crystallization temperature magnetization layer are made of the Co30Fe40B20Ti10.

11. The STTMRAM element, as recited in claim 8, wherein the low-crystallization temperature magnetization layer is made of Ti, Zr, V or Y.

12. The STTMRAM element, as recited in claim 8, wherein the fixed layer is synthetic.

13. The STTMRAM element, as recited in claim 12, wherein the fixed layer is made of cobolt iron/ruthenium/cobolt iron boron (CoFe/Ru/CoFeB) alloy.

14. The STTMRAM element, as recited in claim 1, wherein the barrier layer is made of one or more of the materials:

magnesium oxide, ruthenium oxide, strontium oxide, zinc oxide, aluminum oxide, and titanium oxide.

15. A system including a spin-torque transfer memory random access memory (STTMRAM) element, the 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 an alloy of CoFeB—

Z where Z is made of one or more of titanium, (Ti), yittrium (Y), zirconium (Zr), and vanadium (V), 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.

16. The system, as recited in claim 15, wherein the system is a hand-held consumer device.

17. The system, as recited in claim 15, wherein the system is a laptop.

18. The system, as recited in claim 15, wherein the system is a set-top-box.

19. The system, as recited in claim 15, wherein the system is a microprocessor.