Methods, structures, and devices for reducing operational energy in phase change memory
Methods of forming and operating phase change memory devices include adjusting an activation energy barrier between a metastable phase and a stable phase of a phase change material in a memory cell. In some embodiments, the activation energy barrier is adjusted by applying stress to the phase change material in the memory cell. Memory devices include a phase change memory cell and a material, structure, or device for applying stress to the phase change material in the memory cell. In some embodiments, a piezoelectric device may be used to apply stress to the phase change material. In additional embodiments, a material having a thermal expansion coefficient greater than that of the phase change material may be positioned to apply stress to the phase change material.
1. A memory device, comprising:
a phase change memory cell comprising:
a first electrode;
a second electrode; and
a phase change material disposed between the first electrode and the second electrode;
a piezoelectric device comprising:
a piezoelectric material; and
a field-generating device for providing an electrical field within the piezoelectric material;
wherein the piezoelectric material is located and oriented to cause the piezoelectric material to apply a stress to the phase change material when an electrical field is provided within the piezoelectric material by the field-generating device; and
a dielectric material between the piezoelectric material and the phase change material.
2. The memory device of claim 1 , wherein the phase change material comprises:
a first end surface proximate the first electrode of the phase change memory cell;
a second end surface proximate the second electrode; and
at least one lateral side surface extending between the first end surface and the second end surface.
3. The memory device of claim 2 , wherein the piezoelectric material at least partially surrounds the at least one lateral side surface.
4. The memory device of claim 3 , wherein the piezoelectric material extends entirely circumferentially around the phase change material.
5. The memory device of claim 1 , wherein the first electrode comprises a resistive heating element.
6. The memory device of claim 1 , wherein the field-generating device comprises an additional electrode pair located relative to the piezoelectric device such that an electrical field is provided in the piezoelectric material when a voltage is applied between electrodes of the additional electrode pair.
7. The memory device of claim 1 , wherein the piezoelectric material comprises at least one of quartz, gallium orthophosphate, barium titanate, lead titanate, lead zirconate titanate, and lithium tantalate.
8. The memory device of claim 1 , wherein the phase change material comprises at least one of GeSbTe (GST), GeTe, AgInSbTe, InSe, SbSe, SbTe, InSbSe, InSbTe, GeSbSe, and GeSbTeSe.