Perpendicular magnetic anisotrophy free layers with iron insertion and oxide interfaces for spin transfer torque magnetic random access memory
View Patent ↗A method of making a spin-torque transfer magnetic random access memory device (STT MRAM) device includes forming a tunnel barrier layer on a reference layer; forming a free layer on the tunnel barrier layer, the free layer comprising a cobalt iron boron (CoFeB) alloy layer and an iron (Fe) layer; and performing a sputtering process to form a metal oxide layer on the Fe layer.
1. A method of making a spin-torque transfer magnetic random access memory device (STT MRAM) device, the method comprising:
forming a tunnel barrier layer on a reference layer;
forming a free layer on the tunnel barrier layer, the free layer comprising a discrete cobalt iron boron (CoFeB) alloy layer and a discrete iron (Fe) layer arranged on the discrete CoFeB alloy layer, the Fe layer comprising at least 98 at. % Fe; and
performing a sputtering process to form a metal oxide layer on the Fe layer.
2. The method of claim 1 , wherein the Fe layer comprises at least 98 atomic % (at. %) Fe.
3. The method of claim 1 , wherein the Fe layer has a thickness in a range from about 0.2 to about 2 nanometers (nm).
4. The method of claim 1 , wherein the sputtering process is radiofrequency (RF) sputtering.
5. The method of claim 1 , wherein the tunnel barrier layer comprises magnesium oxide (MgO).
6. The method of claim 1 , wherein the metal oxide layer has a thickness in a range from about 0.2 to about 2 nm.
7. The method of claim 1 , wherein the CoFeB alloy layer has a thickness in a range from about 0.2 to about 2 nm.
8. The method of claim 1 , wherein the CoFeB alloy layer comprises boron (B) in an amount in a range from about 20 to about 30 at. %.
9. The method of claim 1 , wherein the CoFeB alloy layer comprises Fe in an amount in a range from about 20 to about 60 at. %.
10. The method of claim 1 , wherein the CoFeB alloy layer comprises cobalt (Co) in an amount in a range from about 20 to about 40 at. %.
11. The method of claim 2 , wherein the Fe layer comprises substantially pure Fe.
12. The method of claim 1 , wherein the sputtering process is RF sputtering.
13. The method of claim 1 , wherein the sputtering process comprises sputtering a metal oxide onto the Fe layer under a pressure in a range from about 0.1 to about 10 milli-Torr (mTorr).
14. The method of claim 1 , wherein the Fe layer comprises at least 99 at. % Fe.
15. The method of claim 1 , wherein the sputtering process comprises RF sputtering from an oxide target.
16. The method of claim 1 , wherein the discrete CoFeB alloy layer and the discrete Fe layer are ferromagnetically coupled and switch as a single entity under spin torqure currents.
17. The method of claim 12 , wherein the RF sputtering comprises sputtering a metal oxide onto the CoFeB alloy layer.
18. The method of claim 17 , wherein the metal oxide layer has a thickness in a range from about 0.2 to about 2 nm.
19. The method of claim 17 , wherein the metal oxide layer is MgO, tantalum oxide (TaOx), titanium oxide (TiOx), aluminum oxide (AlOx), magnesium titanium oxide (MgTiOx), or any combination thereof.