Perpendicular magnetic tunnel junction (pMTJ) with in-plane magneto-static switching-enhancing layer
View Patent ↗An STTMRAM element includes a magnetic tunnel junction (MTJ) having a perpendicular magnetic orientation. The MTJ includes a barrier layer, a free layer formed on top of the barrier layer and having a magnetic orientation that is perpendicular and switchable relative to the magnetic orientation of the fixed layer. The magnetic orientation of the free layer switches when electrical current flows through the STTMRAM element. A switching-enhancing layer (SEL), separated from the free layer by a spacer layer, is formed on top of the free layer and has an in-plane magnetic orientation and generates magneto-static fields onto the free layer, causing the magnetic moments of the outer edges of the free layer to tilt with an in-plane component while minimally disturbing the magnetic moment at the center of the free layer to ease the switching of the free layer and to reduce the threshold voltage/current.
1. A spin transfer torque magnetic random access memory (STTMRAM) element comprising:
a magnetic free layer and a magnetic pinned layer in contact with a tunnel barrier layer interposed therebetween, said magnetic free layer having a variable perpendicular magnetic orientation, said magnetic pinned layer having an invariable perpendicular magnetic orientation; and
a switching-enhancing layer (SEL) separated from said magnetic free layer by a first non-magnetic spacer layer, said SEL having an invariable in-plane magnetic orientation.
2. The STTMRAM element of claim 1 , wherein said magnetic free layer includes multiple ferromagnetic layers.
3. The STTMRAM element of claim 1 , wherein said magnetic free layer comprises cobalt and iron.
4. The STTMRAM element of claim 1 , wherein said magnetic pinned layer includes multiple ferromagnetic layers.
5. The STTMRAM element of claim 1 , wherein said magnetic pinned layer comprises cobalt and iron.
6. The STTMRAM element of claim 1 , wherein said magnetic pinned layer includes two ferromagnetic layers separated by a second non-magnetic spacer layer, said two ferromagnetic layers having opposite perpendicular magnetization directions.
7. The STTMRAM element of claim 1 , wherein said SEL includes multiple ferromagnetic layers.
8. The STTMRAM element of claim 1 , wherein said SEL includes a ferromagnetic layer and an antiferromagnetic layer formed adjacent thereto.
9. The STTMRAM element of claim 1 , wherein said SEL comprises cobalt and iron.
10. The STTMRAM element of claim 1 , wherein said SEL includes a first switching-enhancing sublayer (SES) and a second SES separated by a third non-magnetic spacer layer with said first SES formed adjacent to said first non-magnetic spacer layer, said first and second switching-enhancing sublayers having opposite in-plane magnetization directions.
11. The STTMRAM element of claim 10 , wherein each of said first and second switching-enhancing sublayers further includes a ferromagnetic layer.
12. The STTMRAM element of claim 10 , wherein said second SES further includes a ferromagnetic layer and an antiferromagnetic layer formed adjacent thereto.
13. The STTMRAM element of claim 1 , wherein said first non-magnetic spacer layer comprises a metal layer and an insulator layer.
14. The STTMRAM element of claim 1 , wherein said first non-magnetic spacer layer is made of an insulator material.
15. The STTMRAM element of claim 1 , wherein said first non-magnetic spacer layer is made of a conductor material.
16. The STTMRAM element of claim 1 , wherein said first non-magnetic spacer layer is made of Ta, Ti, Ru, Ru, Pt, Cr, Cu, or Hf.
17. The STTMRAM element of claim 1 further comprising a cap layer formed adjacent to said SEL opposite said first non-magnetic spacer layer.
18. The STTMRAM element of claim 1 further comprising a seed layer formed adjacent to said SEL opposite said first non-magnetic spacer layer.