Phase change memory cell having pillar bottom electrode with improved thermal insulation
A phase-change memory device includes a bottom electrode; a stack of alternating electrical conductor layers directly contacting a top surface of the bottom electrode; a metal pillar directly contacting a top surface of the stack; a phase change material element directly contacting a top surface of the metal pillar; and a top electrode on the phase change material element, wherein a lateral dimension of the metal pillar is smaller than that of the stack.
1. A phase-change memory device comprising:
a bottom electrode;
a stack of alternating electrical conductor layers stacked parallel to the bottom electrode and directly contacting a top surface of the bottom electrode, wherein the stack of alternating electrical conductor layers in turn comprises:
at least two titanium nitride (TiN) layers including a bottommost titanium nitride (TiN) layer; and
at least two tantalum nitride (TaN) layers including a topmost tantalum nitride (TaN) layer;
a metal pillar directly contacting a top surface of the topmost tantalum nitride (TaN) layer;
a phase change material element directly contacting a top surface of the metal pillar;
a thermally and electrically insulating spacer on the stack and surrounding the metal pillar under the phase change material element; and
a top electrode on the phase change material element,
wherein a lateral dimension of the metal pillar is smaller than that of the stack.
2. The phase-change memory device of claim 1 , further comprising:
an underlayer under the bottom electrode; and
an interlevel dielectric on the underlayer and surrounding the bottom electrode.
3. The phase-change memory device of claim 1 , wherein
the thermally and electrically insulating spacer has a width equal to a width of the stack.
4. The phase-change memory device of claim 1 , further comprising:
a first dielectric layer surrounding the stack;
an encapsulation layer formed over the phase change material and the first dielectric layer; and
a second dielectric layer formed on the encapsulation layer, wherein the top electrode is formed on the second dielectric layer, and the top electrode further comprising a top electrode contact electrically connecting the top electrode to the phase change material element.
5. The phase-change memory device of claim 4 , further comprising a top hardmask between the phase change material element and the top electrode contact.
6. The phase-change memory device of claim 4 , wherein the top electrode contact extends through the encapsulation layer.
7. The phase-change memory device of claim 1 , further comprising a top hardmask on the phase change material element having a same width as the phase change material element.
8. The phase-change memory device of claim 1 , wherein a thickness of the bottommost TiN layer is equal to a thickness of the topmost TaN layer.
9. The phase-change memory device of claim 1 , wherein a thickness of the bottommost TiN layer is greater than a thickness of any other layer of the stack.
10. The phase-change memory device of claim 1 , wherein the metal pillar is formed of a material other than TiN and TaN.
11. The phase-change memory device of claim 1 , wherein the metal pillar is formed of a material different than those of the stack of alternating electrical conductor layers.
12. The phase-change memory device of claim 1 , wherein the metal pillar is a heater.
13. The phase-change memory device of claim 1 , wherein the metal pillar is a heater configured to heat the phase change material element.