Transient heat assisted STTRAM cell for lower programming current
View Patent ↗A memory cell including magnetic materials and heating materials, and methods of programming the memory cell are provided. The memory cell includes a free region, a pinned region, and a heating region configured to generate and transfer heat to the free region when a programming current is directed to the cell. The heat transferred from the heating region increases the temperature of the free region, which decreases the magnetization and the critical switching current density of the free region. In some embodiments, the heating region may also provide a current path to the free region, and the magnetization of the free region may be switched according to the spin polarity of the programming current, programming the memory cell to a high resistance state or a low resistance state.
1. A method of operating a memory cell comprising:
heating a free region of a magnetic cell structure to increase the temperature of the free region, wherein heating the free region comprises decreasing a critical switching current density of the free region; and
programming the memory cell while the temperature of the free region is increased.
2. The method, as set forth in claim 1 , wherein heating the free region comprises transferring heat from a heater material to the free region.
3. The method, as set forth in claim 2 , wherein transferring heat from the heater material to the free region is facilitated by an electrical insulator.
4. The method, as set forth in claim 1 , wherein decreasing the critical switching current density of the free region comprises decreasing the critical switching current density of the free region to approximately 0.5 mA/cm 2 .
5. The method, as set forth in claim 1 , wherein heating the free region comprises directing a current to the free region.
6. The method, as set forth in claim 5 , wherein the current is directed in a current path, wherein the current path flows from a pinned region in the magnetic cell structure to the free region to the heater material.
7. The method, as set forth in claim 5 , wherein the current is directed in a current path, wherein the current path flows from the heater material to the free region.
8. The method, as set forth in claim 7 , wherein a portion of the current path through the heater material is in a direction perpendicular to the free region and a pinned region in the magnetic cell structure.
9. The method, as set forth in claim 5 , wherein the current is directed in one or more parallel current paths, wherein a first current path is through the heater material, and wherein a second current path is through the free region and a pinned region of the magnetic cell structure.
10. A magnetic cell structure comprising:
a free region;
a pinned region; and
a heater material configured to generate heat and transfer the heat to the free region when a programming current is directed to the magnetic cell structure, wherein a first orientation of the free region is crosswise to a second orientation of the heater material.
11. The magnetic cell structure, as set forth in claim 10 , comprising an electrical insulator to facilitate heat transfer from the heater material to the free region.
12. The magnetic cell structure, as set forth in claim 10 , wherein the free region and the pinned region comprise ferromagnetic materials.
13. The magnetic cell structure, as set forth in claim 10 , comprising a nonmagnetic region disposed between the free region and the pinned region.
14. The magnetic cell structure, as set forth in claim 10 , comprising an insulative region configured to insulate one or more regions of the magnetic cell structure from one or more of the programming current and the heat generated in the heater material.
15. The magnetic cell structure, as set forth in claim 10 , comprising an electrode coupled to the free region and the heater material, wherein the electrode is configured to carry the programming current to one or more regions of the magnetic cell structure.
16. The magnetic cell structure, as set forth in claim 10 , wherein the heater material comprises TiN, ZrN, HfN, VN, NbN, TaN, TiAlN, TiSiN, TaSiN, TiCN, TiC, ZrC, HfC, VC, NbC, TaC, Cr3C2, Mo2C, WC, SiC, B4C, TiB2, ZrB2, HfB2,VB2, NbB2, TaB2, CrB2, Mo2B5, W2B5, WSix, MoSi2, Sn 0 2 :Sb, carbon, niobium, tungsten, molybdenum, metal alloys, or any combination thereof.
17. The magnetic cell structure, as set forth in claim 16 , arranged such that during operation, the programming current is directed to the magnetic cell structure in parallel, wherein one path of the programming current is directed to the free region and the pinned region, and wherein another path of the programming current is directed to the perpendicularly arranged heater material.
18. The magnetic cell structure, as set forth in claim 16 , configured to provide a current path from the pinned region to the free region to a conductive region to the heater material.
19. The magnetic cell structure, as set forth in claim 10 , configured to provide a current path from the heater material to the free region to the pinned region.
20. The magnetic cell structure, as set forth in claim 10 , wherein a spin-torque transfer magnetic random access memory cell comprises the magnetic cell structure.
21. A method of operating a memory cell comprising:
decreasing a critical switching current density of a free region of a magnetic cell structure; and
programming the memory cell after decreasing the critical switching current density of a free region of a magnetic cell structure.
22. The method, as set forth in claim 21 , wherein decreasing the critical switching current comprises heating the free region.
23. The method, as set forth in claim 22 , wherein heating the free region comprises transferring heat from a heater material to the free region.
24. The method, as set forth in claim 23 , wherein transferring heat from the heater material to the free region is facilitated by an electrical insulator.
25. The method, as set forth in claim 21 , wherein decreasing the critical switching current density of the free region comprises decreasing the critical switching current density of the free region to approximately 0.5 mA/cm 2 .