Three terminal selectors for memory applications and their methods of fabrication
A memory device includes a first electrode, a non-volatile memory element having a first terminal and a second terminal, where the first terminal is coupled to the first electrode. The memory device further includes a selector having a first terminal, a second terminal and a sidewall between the first and second terminals, where the second terminal of the selector is coupled to the first terminal of the non-volatile memory element. A second electrode is coupled to the second terminal of the selector and a third electrode laterally adjacent to the sidewall of the selector.
1. A memory device comprising:
a first electrode;
a non-volatile memory element having a first terminal and a second terminal, wherein the first terminal is coupled to the first electrode;
a selector having a first terminal coupled to a second terminal through an insulator layer therebetween, wherein the first terminal of the selector is further coupled to the second terminal of the non-volatile memory element;
a second electrode coupled to the second terminal of the selector; and
a third electrode laterally adjacent to a sidewall of the insulator layer.
2. The memory device of claim 1 , wherein the selector comprises a metal-insulator-metal stack.
3. The memory device of claim 1 , wherein the insulator layer comprises oxygen and at least one of hafnium, tantalum, niobium and vanadium.
4. The memory device of claim 1 , wherein the insulator layer comprises a phase change material.
5. The memory device of claim 4 , wherein the phase change material comprises at least Ge and Te.
6. The memory device of claim 1 , wherein the insulator layer comprises a filament extending through at least a partial thickness of the insulator layer.
7. The memory device of claim 1 , wherein the insulator layer has a thickness between 1 nm and 50 nm.
8. The memory device of claim 2 , wherein the third electrode is laterally adjacent to a sidewall of the metal-insulator-metal stack.
9. The memory device of claim 1 , further comprising a dielectric layer between the third electrode and the sidewall of the insulator layer.
10. The memory device of claim 9 , wherein the dielectric layer comprises oxygen and one or more metals.
11. The memory device of claim 1 , wherein the non-volatile memory element comprises a magnetic tunnel junction (MTJ) device, the MTJ device comprising:
a fixed magnet;
a tunnel barrier above the fixed magnet; and
a free magnet above the tunnel barrier.
12. The memory device of claim 1 , wherein the non-volatile memory element comprises a resistive RAM device.
13. The memory device of claim 1 , wherein:
the selector comprises a first selector and the memory device further comprises a second selector and a third selector;
the first electrode and the second electrode are coupled to the first selector and to the second selector; and
the third electrode, extends in a direction orthogonal to the first and second electrodes and is coupled to the first selector and to the third selector.
14. A method to fabricate a memory device, comprising:
forming a first electrode;
forming a non-volatile memory element coupled to the first electrode;
forming a selector comprising a metal-insulator-metal (MIM) stack coupled to the non-volatile memory element;
depositing a second electrode adjacent to a sidewall of the selector; and
forming a third electrode coupled to the selector.
15. The method of claim 14 , wherein depositing the second electrode comprises depositing a conductive material laterally adjacent to a dielectric layer that is laterally adjacent to a sidewall of the MIM stack.
16. The method of claim 14 , wherein forming the selector further comprises depositing the MIM stack, and forming the sidewall of the selector by patterning the MIM stack.
17. The method of claim 14 , wherein forming the third electrode further comprises:
depositing a dielectric layer over the selector and the second electrode; and
landing a conductive via on a metal layer of the MIM stack.
18. The method of claim 14 , wherein forming the non-volatile memory element further comprises forming an MTJ memory device.
19. A method of operating a memory device, the method comprising:
applying a first voltage to a first terminal of a selector having a second terminal coupled to a non-volatile memory device, wherein the selector comprises a metal-insulator-metal (MIM) stack;
setting a threshold voltage of the selector by applying a second voltage to a third terminal of the selector;
sensing a state of the memory device by measuring a charge flow through the memory device.
20. The method of claim 19 , wherein the first voltage is between 0 and 50 mV, the second voltage is between 2V and 3V, and the threshold voltage is less than 50 my.