Spin transfer torque cell for magnetic random access memory
Embodiments are directed to STT MRAM devices. One embodiment of an STT MRAM device includes a reference layer, a tunnel barrier layer, a free layer and one or more conductive vias. The reference layer is configured to have a fixed magnetic moment. In addition, the tunnel barrier layer is configured to enable electrons to tunnel between the reference layer and the free layer through the tunnel barrier layer. The free layer is disposed beneath the tunnel barrier layer and is configured to have an adaptable magnetic moment for the storage of data. The conductive via is disposed beneath the free layer and is connected to an electrode. Further, the conductive via has a width that is smaller than a width of the free layer such that a width of an active STT area for the storage of data in the free layer is defined by the width of the conductive via.
1. A spin transfer torque (STT) magnetic random access memory (MRAM) device comprising:
at least one conductive via formed over a first electrode;
a first insulator formed over the first electrode;
a second insulator formed over the first insulator, where the first and second insulators contact the at least one conductive via;
a magnetic tunnel junction (MTJ) stack including at least a free layer, the MTJ stack formed over the at least one conductive via and the second insulator; and
a seed layer formed directly between the at least one conductive via and the free layer of the MTJ stack, the free layer including an excess agent.
2. The device of claim 1 , wherein a second electrode is formed over the MTJ stack.
3. The device of claim 2 , wherein the MRAM device is annealed to cause the at least one conductive via to absorb the excess agent.
4. The device of claim 1 , wherein the second insulator delivers the excess agent to enable a chemical reaction between the free layer of the MTJ stack and the second insulator.
5. The device of claim 1 , wherein the first insulator has a first thickness and the second insulator has a second thickness, the first thickness being greater than the second thickness.
6. The device of claim 1 , wherein the seed layer contacts the second insulator.
7. The device of claim 1 , wherein the seed layer extends a length of the free layer of the MTJ stack.
8. The device of claim 1 , wherein the seed layer extends over an entire upper surface of the second insulator.
9. The device of claim 1 , wherein the excess agent is selected from the group consisting of elements from the thirteenth, fifteenth, sixteenth and seventeenth columns of the periodic table of elements.
10. The device of claim 1 , wherein annealing causes the excess agent to react with the free layer to increase a resistivity of portions of the free layer that are above the excess agent.
11. A spin transfer torque (STT) magnetic random access memory (MRAM) device comprising:
a first insulator formed over a first electrode;
a second insulator formed over the first insulator;
a magnetic tunnel junction (MTJ) stack including at least a free layer; and
a seed layer formed directly between at least one conductive via and the free layer of the MTJ stack, the free layer including an excess agent.
12. The device of claim 11 , wherein the at least one conductive via is formed over the first electrode.
13. The device of claim 12 , wherein the first and second insulators directly contact the at least one conductive via.
14. The device of claim 13 , wherein the MTJ stack is formed over the at least one conductive via and the second insulator.
15. The device of claim 14 , wherein a second electrode is formed over the MTJ stack.
16. The device of claim 15 , wherein the MRAM device is annealed to cause the at least one conductive via to absorb the excess agent.
17. The device of claim 11 , wherein the second insulator delivers the excess agent to enable a chemical reaction between the free layer of the MTJ stack and the second insulator.
18. The device of claim 11 , wherein the first insulator has a first thickness and the second insulator has a second thickness, the first thickness being greater than the second thickness.
19. The device of claim 11 , wherein the seed layer directly contacts the second insulator.
20. The device of claim 11 , wherein the seed layer extends a length of the free layer of the MTJ stack.