Initialization process for magnetic random access memory (MRAM) production
地域：
Hsinchu
摘要
An initialization process is disclosed for a perpendicular magnetic tunnel junction (p-MTJ) wherein the switching error rate is reduced from a typical range of 30-100 ppm to less than 10 ppm. In one embodiment, an in-plane magnetic field is applied after a final anneal step is performed during memory device fabrication such that all magnetizations in the free layer, and AP1 and AP2 pinned layers are temporarily aligned “in-plane”. After the applied field is removed, interfacial perpendicular magnetic anisotropy (PMA) at a tunnel barrier/AP1 interface induces a single AP1 magnetic domain with a magnetization in a first vertical direction. Interfacial PMA at a FL/tunnel barrier interface affords a single FL domain with magnetization in the first direction or opposite thereto. AP2 magnetization is opposite to the first direction as a result of antiferromagnetic coupling with the AP1 layer. Alternatively, a perpendicular-to-plane magnetic field may be applied for initialization.
說明書
The present application is a continuation application of U.S. patent application Ser. No. 15/818,148 filed Nov. 20, 2017, which is hereby incorporated by reference in its entirety.
This application is related to Ser. No. 15/668,113, filed on Aug. 3, 2017; and Ser. No. 16/056,791, filed Aug. 7, 2018; which are herein incorporated by reference in their entirety.
The present disclosure relates to a method of establishing a single domain in the pinned layer of a magnetic tunnel junction (MTJ) thereby providing a lower switching error rate of an adjacent free layer during a write process, and leading to lower power consumption with longer device lifetimes.
Perpendicularly magnetized magnetic tunnel junctions (p-MTJs) are a major emerging technology for use in embedded MRAM applications, in standalone MRAM applications, and in spin-torque transfer (STT)-MRAM. STT-MRAM is a p-MTJ technology using spin-torque for writing of memory bits that was described by C. Slonezewski in “Current driven excitation of magnetic multilayers”, J. Magn. Magn. Mater. V 159, L1-L7 (1996). P-MTJ technologies that have a high operating speed, low power consumption, excellent endurance, non-volatility, and scalability are highly competitive with existing semiconductor memory technologies such as SRAM, DRAM, and flash.
權利要求
What is claimed is:1. A method comprising:providing a magnetic tunnel junction (MTJ) cell on a substrate, wherein the MTJ cell includes a free layer (FL), a first pinned layer and a second pinned layer, wherein each of the FL, first pinned layer and second pinned layer have a first magnetization domain and a second magnetization domain such that the second magnetization domain is in a different direction than the first magnetization domain; applying a magnetic field in a direction such that the first magnetization domain and the second magnetization domain in each of the FL, first pinned layer, and second pinned layer are aligned in the direction of the applied magnetic field; and removing the applied magnetic field from the FL, the first pinned layer and the second pinned layer, and wherein after the removing of the applied magnetic field the first magnetization domain and the second magnetization domain in the first pinned layer have an equal probability of being aligned in a first direction or a second direction that is different from the first direction; wherein after the removing of the applied magnetic field the first magnetization domain and the second magnetization domain in the second pinned layer are both aligned in one of the first direction and the second direction to yield a single magnetic domain in the second pinned layer; and wherein after the removing of the applied magnetic field the first magnetization domain and the second magnetization domain in the FL layer are both aligned in one of the first direction and the second direction to yield a single magnetic domain in the Fl. 2. The method of claim 1 , wherein after the removing of the applied magnetic field the first magnetization domain and the second magnetization domain in the second pinned layer are both aligned in the first direction and the first magnetization domain and the second magnetization domain in the first pinned layer are both aligned in the second direction. 3. The method of claim 1 , wherein the first magnetization domain and the second magnetization domain in the FL layer have an equal probability of being aligned in the first direction or the second direction after the removing of the applied magnetic field. 4. The method of claim 1 , wherein the applying of the magnetic field in the direction includes applying the magnetic field in a third direction that is different than the first and second directions. 5. The method of claim 4 , wherein the third direction is substantially perpendicular to at least one of the first direction and the second direction. 6. The method of claim 1 , wherein all magnetization domains in the FL point in the same direction after the removing of the applied magnetic field,wherein all magnetization domains in the first pinned layer point in the same direction after the removing of the applied magnetic field, and wherein all magnetization domains in the second pinned layer point in the same direction after the removing of the applied magnetic field. 7. The method of claim 1 , wherein the magnetic field has a magnitude from about 1000 Oe to about 30000 Oe, and is applied at a temperature proximate to room temperature, and in the absence of an applied electrical current. 8. A method comprising:providing a magnetic tunnel junction (MTJ) cell on a substrate, wherein the MTJ cell includes a free layer (FL), a first pinned layer and a second pinned layer, wherein at least one of the FL, first pinned layer and second pinned layer has a first magnetization domain and a second magnetization domain such that the second magnetization domain is in a different direction than the first magnetization domain; applying a magnetic field in a direction such that the first magnetization domain and the second magnetization domain are aligned in the direction of the applied magnetic field; and removing the applied magnetic field to yield a single magnetic domain in each of the FL, the first pinned layer and the second pinned layer, and wherein the first magnetization domain and the second magnetization domain are both aligned in one of the first direction and the second direction. 9. The method of claim 8 , wherein the first magnetization domain and the second magnetization domain are in either the FL or the first pinned layer, andwherein the first magnetization domain and the second magnetization domain have an equal probability of being aligned in the first direction or the second direction after the removing of the applied magnetic field. 10. The method of claim 8 , wherein the applying of the magnetic field in the direction includes applying the magnetic field in one of the first direction and the second direction. 11. The method of claim 8 , wherein the applying of the magnetic field in the direction includes applying the magnetic field in a third direction that is different than the first and second directions. 12. The method of claim 8 , wherein the MTJ cell further includes:a seed layer interfacing with the second pinned layer; an antiferromagnetic layer interfacing with both the first pinned layer and the second pinned layer; a nonmagnetic spacer layer interfacing with both the first pinned layer and the FL; and a capping layer interfacing with the FL. 13. The method of claim 8 , wherein the MTJ cell further includes:a seed layer interfacing with the FL; an antiferromagnetic layer interfacing with both the first pinned layer and the second pinned layer; a nonmagnetic spacer layer interfacing with both the first pinned layer and the FL; and a capping layer interfacing with the second pinned layer. 14. The method of claim 8 , wherein the MTJ cell further includes a third pinned layer and a fourth pinned layer. 15. The method of claim 8 , further comprising forming an encapsulation layer on the MTJ cell to electrically insulate the MTJ cell from another MTJ cell, andwherein the applying of the magnetic field in the direction occurs either during the forming of the encapsulation layer or after the forming of the encapsulation layer. 16. A method comprising:providing a magnetic tunnel junction (MTJ) cell on a substrate, wherein the MTJ cell includes a free layer (FL), a first pinned layer, a second pinned layer, and an antiferromagnetic layer coupling the first and second pinned layers, wherein at least one of the FL, the first pinned layer and the second pinned layer includes multiple magnetic domains; applying a magnetic field in a direction such that all magnetic domains in the FL, the first pinned layer and the second pinned layer are aligned in the direction of the applied magnetic field; and removing the applied magnetic field to yield a single magnetic domain in each of the FL, the first pinned layer and the second pinned layer, and wherein the single magnetic domain of the first pinned layer is opposite the single magnetic domain of the second pinned layer. 17. The method of claim 16 , wherein the single magnetic domain of the first pinned layer has an equal probability of being in a first direction or a second direction that is different than the first direction after the removing of the applied magnetic field. 18. The method of claim 16 , wherein the single magnetic domain of the FL has an equal probability of being in a first direction or a second direction that is different than the first direction after the removing of the applied magnetic field. 19. The method of claim 16 , wherein the antiferromagnetic layer includes Ru having a thickness ranging from about 4 ? to about 9 ?. 20. The method of claim 16 , wherein the applying the magnetic field in the direction includes applying the magnetic field in the direction a plurality of times.
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