Manufacturing method for pipe-shaped electrode phase change memory

1. A method for manufacturing a memory device, comprising:

forming a first electrode comprising a pipe-shaped member having an axis, a first end, a second end and sidewalls having thickness in a dimension orthogonal to the axis of the pipe-shaped member, having a ring-shaped surface at the second end, and a disc shaped member coupled to the first end of the pipe-shaped member, including

forming a first layer of electrode material;

forming a pillar on the first layer of electrode material, the pillar having a cylindrical outside surface;

depositing a conformal layer of electrode material over the cylindrical outside surface of the pillar and over the first layer of electrode material to form an electrode material covered pillar; and

removing electrode material from on top of the electrode material covered pillar to expose a top surface of the pillar and a ring-shaped top surface of the conformal layer of electrode material to form said pipe-shaped member and removing electrode material of the first layer to form said disc shaped member;

forming a layer of programmable resistive material in contact with the ring-shaped top surface of the pipe-shaped member; and

forming a second electrode in contact with the layer of programmable resistive material.

2. The method of claim 1 , wherein the first layer of electrode material comprises a first material, and the conformal layer of electrode material comprises a second material that is different than the first material.

3. The method of claim 1 , wherein the pillar comprises a thermal insulator inside the pipe-shaped member.

4. The method of claim 3 , wherein the programmable resistive material has an amorphous state, and the thermal insulator inside the pipe-shaped member having a thermal conductivity less than the programmable resistive material in the amorphous state.

5. The method of claim 1 , wherein the pipe-shaped member has a cylindrical inside surface and an outside surface, having a thickness between the inside surface and the outside surface less than 30 nm.

6. The method of claim 1 , wherein the pipe-shaped member has length along its axis of less than 150 nm.

7. The method of claim 1 , wherein the pipe-shaped member has a cylindrical inside surface having a diameter less than 50 nm.

8. The method of claim 1 , wherein the pipe-shaped member has a cylindrical inside surface and an outside surface, having a thickness between the inside surface and the outside surface, and wherein the thickness of the disc shaped member is greater than twice the thickness of the sidewalls between the inside surface and the outside surface.

9. The method of claim 1 , wherein the programmable resistive material comprises a chalcogenide.

10. The method of claim 1 , wherein the programmable resistive material has at least two solid phases which are reversibly inducible by a current.

11. The method of claim 1 , wherein the programmable resistive material has at least two solid phases which include a generally amorphous phase and a generally crystalline phase.

12. The method of claim 1 , wherein the programmable resistive material comprises Ge 2 Sb 2 Te 5 .

13. The method of claim 1 , wherein said disc shaped member comprises a first material, and said pipe-shaped member comprises a second material that has a higher resistivity than the first material.

14. A method for making a memory device comprising:

forming a memory cell access layer on a substrate, the memory cell access layer including an interlayer dielectric having an upper surface and contacts exposed on the upper surface;

depositing a first electrode layer on the upper surface contacting said contacts;

forming a pillar on the first electrode layer, the pillar having a cylindrical outside surface;

depositing a conformal layer of electrode material over the cylindrical outside surface of the pillar and over first electrode layer to form sidewalls of electrode material on the pillar leaving an electrode material covered pillar;

removing electrode material from on top of the electrode material covered pillar to expose a top surface of the pillar and a ring-shaped top surface of the conformal layer of electrode material, to form a pipe-shaped member comprising at least a portion of the sidewalls of electrode material, and removing exposed portions of the first electrode layer to form a disc shaped member coupled to the pipe-shaped member;

forming a layer of phase change material in contact with the top surface of the pipe- shaped member;

forming a layer of top electrode material in contact with the layer of phase change material; and

etching the layer of top electrode material and the layer of phase change material to define memory cell stacks contacting respective contacts on said upper surface of the memory cell access layer.

15. The method of claim 14 , wherein the pillar comprises a thermal insulator inside the pipe-shaped member.

16. The method of claim 15 , wherein the phase change material has an amorphous state, and the thermal insulator inside the pipe-shaped member has a thermal conductivity less than the phase change material in the amorphous state.

17. The method of claim 14 , wherein the pipe-shaped member has a cylindrical inside surface and an outside surface, having a thickness between the inside surface and the outside surface less than 30 nm.

18. The method of claim 14 , wherein the pipe-shaped member has a cylindrical inside surface having a diameter less than 50 nm.

19. The method of claim 14 , wherein the pipe-shaped member has a cylindrical inside surface and an outside surface, having a thickness between the inside surface and the outside surface, and wherein the thickness of the disc shaped member is greater than twice the thickness of the sidewalls between the inside surface and the outside surface.

20. The method of claim 14 , wherein the phase change material comprises a chalcogenide.

21. The method of claim 14 , wherein the phase change material comprises Ge 2 Sb 2 Te 5 .

22. The method of claim 14 , wherein the pipe-shaped member has length along its axis of less than 150 nm.