Method for forming a PCRAM with low reset current
Phase-change memory structures are formed with ultra-thin heater liners and ultra-thin phase-change layers, thereby increasing heating capacities and lowering reset currents. Embodiments include forming a first interlayer dielectric (ILD) over a bottom electrode, removing a portion of the first ILD, forming a cell area, forming a u-shaped heater liner within the cell area, forming an interlayer dielectric structure within the u-shaped heater liner, the interlayer dielectric structure including a protruding portion extending above a top surface of the first ILD, forming a phase-change layer on side surfaces of the protruding portion and/or on the first ILD surrounding the protruding portion, and forming a dielectric spacer surrounding the protruding portion.
1. A device comprising:
a bottom electrode;
a u-shaped heater liner;
an interlayer dielectric (ILD) on the bottom electrode, surrounding the u-shaped heater liner;
an interlayer dielectric structure surrounded by the u-shaped heater liner and including a protrusion extending above the u-shaped heater liner and a top surface of the ILD;
a phase-change layer on the ILD, surrounding the interlayer dielectric structure;
a dielectric spacer above the ILD and surrounding the protrusion; and
a top electrode covering the ILD, the protrusion, and the dielectric spacer.
2. A device according to claim 1 , comprising the dielectric spacer being on the phase-change layer.
3. A device according to claim 1 , comprising:
a top surface of the phase-change layer being level with a top surface of an exposed portion of the u-shaped heater liner above the ILD; and
the phase-change layer surrounding the exposed portion of the u-shaped heater liner.
4. A device according to claim 1 , further comprising the phase-change layer on side surfaces of the protrusion between the dielectric spacer and the protrusion.
5. A device according to claim 4 , comprising the phase-change layer on the side surfaces of the protrusion being contiguous and aligned with vertical portions of the u-shaped heater liner.
6. A device according to claim 4 , wherein a height of the phase-change layer on the side surfaces of the protrusion and a height of the protrusion are substantially the same.
7. A device according to claim 6 , comprising the top surface of the phase-change layer on the side surfaces of the protrusion extending above a top surface of the dielectric spacer.
8. A device according to claim 1 , wherein a thickness of a heater liner layer forming the u-shaped heater liner is the same as a thickness of the phase-change layer.
9. A device comprising:
a bottom electrode;
a u-shaped heater liner;
an interlayer dielectric (ILD) on the bottom electrode, surrounding the u-shaped heater liner;
an interlayer dielectric structure surrounded by the u-shaped heater liner and including a protrusion extending above the u-shaped heater liner and a top surface of the ILD;
a phase-change layer on side surfaces of the protrusion;
a dielectric spacer above the ILD and surrounding the protrusion; and
a top electrode covering the ILD, the protrusion, and the dielectric spacer.
10. A device according to claim 9 , comprising the phase-change layer being contiguous and aligned with vertical portions of the u-shaped heater liner.
11. A device according to claim 9 , wherein a height of the phase-change layer and a height of the protrusion are substantially the same.
12. A device according to claim 9 , comprising the top surface of the phase-change layer extending above a top surface of the dielectric spacer.
13. A device according to claim 9 , wherein a thickness of a heater liner layer forming the u-shaped heater liner is the same as a thickness of the phase-change layer.
14. A device comprising:
a bottom electrode;
a u-shaped heater liner;
an interlayer dielectric (ILD) on the bottom electrode, surrounding the u-shaped heater liner;
an interlayer dielectric structure surrounded by the u-shaped heater liner and including a protrusion extending above the u-shaped heater liner and a top surface of the ILD;
a phase-change layer, formed to substantially the same thickness as the u-shaped heater liner, the phase-change layer being on the ILD surrounding the interlayer dielectric structure and level with a top surface of an exposed portion of the u-shaped heater liner and/or the phase-change layer being on side surfaces of the protrusion to the same height as the protrusion;
a dielectric spacer above the ILD and surrounding the protrusion; and
a top electrode covering the ILD, the protrusion, and the dielectric spacer.
15. A device according to claim 14 , wherein the phase-change layer is on side surfaces of the protrusion, contiguous and aligned with vertical portions of the u-shaped heater liner.
16. A device according to claim 15 , wherein a top surface of the phase-change layer extends above a top surface of the dielectric spacer.
17. A device according to claim 14 , wherein the phase-change layer comprises Ge 2 Sb 2 Te 5 (GST) or silver and indium doped Sb 2 Te (AIST) and is formed to a thickness of 10 to 50 angstroms (Å).
18. A device according to claim 14 , wherein the heater liner comprises tungsten (W), titanium (Ti), or titanium nitride (TiN) and is formed to a thickness of 10 to 50 Å.
19. A device according to claim 14 , wherein the interlayer dielectric structure comprises silicon dioxide (SiO 2 ), silicon oxynitride (SiON), silicon nitride (Si 3 N 4 ), or fluorine doped SiO 2 .
20. A device according to claim 14 , wherein the bottom and top electrodes comprise aluminum (Al), platinum (Pt), titanium nitride (TiN), titanium nitride and titanium (TiN/Ti), ruthenium (Ru), nickel (Ni), or polysilicon.