Phase change memory with a select device having a breakdown layer
View Patent ↗A select device may have its threshold current reduced relative to the threshold current of a phase change memory element by providing within the select device a breakdown layer. Because the breakdown layer forms a breakdown filament along its length, the relative area between layers may be reduced, reducing the threshold current of the select device relative to that of the memory element. In addition, a stack may be formed with the select device over the memory element. The select device may be arranged so that the position of the breakdown filament may be moved inwardly relative to the etched edge to also reduce leakage current. In one embodiment, sidewall spacers may be formed on a portion of the select device.
1. A method comprising:
providing a phase change memory including a select device and a memory element;
forming said select device of an upper conductive material, a switching material, and a lower conductive material;
forming said switching material of a material that is not programmable; and
providing a dielectric breakdown layer within said select device.
2. The method of claim 1 including forming said breakdown layer between said upper conductive material and said switching material.
3. The method of claim 1 including forming said breakdown layer between said lower conductive material and said switching material.
4. The method of claim 1 including forming said upper conductive material to have a smaller lateral extent than said switching material.
5. The method of claim 4 including providing sidewall spacers on the side of said upper conductive material.
6. The method of claim 1 including forming said breakdown layer of a material that adheres to a layer in contact with said breakdown layer.
7. The method of claim 6 including forming said breakdown layer of Al 2 O 3 .
8. The method of claim 1 including forming a stack including said select device over said memory element.
9. The method of claim 8 including forming said memory element beneath said select device.
10. A phase change memory comprising:
a phase change memory element including a chalcogenide; and
a select device for said memory element, said select device including a breakdown layer, wherein said select device includes an upper conductive material, a switching material, and a lower conductive material, and wherein said switching material is not programmable.
11. The memory of claim 10 wherein said breakdown layer is a dielectric.
12. The memory of claim 11 wherein said breakdown layer includes Al 2 O 3 .
13. The memory of claim 10 wherein said switching material is a chalcogenide.
14. The memory of claim 10 wherein said breakdown layer is between said upper conductive material and said switching material.
15. The memory of claim 10 wherein said breakdown layer is between said lower conductive material and said switching material.
16. The memory of claim 10 wherein said upper conductive material has a smaller lateral extent than said switching material.
17. The memory of claim 16 including sidewall spacers on the side of said upper conductive material.
18. The memory of claim 10 wherein said phase change memory element and said select device are formed as a stack having a common etched edge.
19. The memory of claim 18 wherein said memory element is below said select device.
20. The memory of claim 19 wherein said select device includes an upper conductive material, a switching material, and a lower conductive material and said upper conductive material has a smaller lateral extent than said lower conductive material.
21. A system comprising:
a processor;
a static random access memory coupled to said processor; and
a memory including a phase change memory element having a chalcogenide and a select device for said memory element, said select device including a breakdown layer, wherein said select device includes an upper conductive material, a switching material, and a lower conductive material and said upper conductive material has a smaller lateral extent than said lower conductive material.
22. The system of claim 21 wherein said breakdown layer is a dielectric.
23. The system of claim 21 wherein said breakdown layer includes Al 2 O 3 .
24. The system of claim 21 wherein said select device includes a chalcogenide material.
25. The system of claim 21 including sidewall spacers on said upper conductive material.
26. A phase change memory comprising:
a phase change memory element including a chalcogenide; and
a select device for said memory element, said select device including a breakdown layer, wherein said select device includes an upper conductive material, a switching material, and a lower conductive material and said upper conductive material has a smaller lateral extent than said switching material.
27. The memory of claim 26 wherein said breakdown layer is a dielectric.
28. The memory of claim 27 wherein said breakdown layer includes Al 2 O 3 .
29. The memory of claim 26 wherein said switching material is not programmable.
30. The memory of claim 29 wherein said switching material is a chalcogenide.
31. The memory of claim 26 wherein said breakdown layer is between said upper conductive material and said switching material.
32. The memory of claim 26 wherein said breakdown layer is between said lower conductive material and said switching material.
33. The memory of claim 26 including sidewall spacers on the side of said upper conductive material.
34. The memory of claim 26 wherein said phase change memory element and said select device are formed as a stack having a common etched edge.
35. The memory of claim 32 wherein said memory element is below said select device.
36. The memory of claim 35 wherein said select device includes an upper conductive material, a switching material, and a lower conductive material and said upper conductive material has a smaller lateral extent than said lower conductive material.