Semiconductor phase change memory using multiple phase change layers
View Patent ↗In accordance with some embodiments, a phase change memory may be formed in which the thermal conductivity in the region outside the programmed volume of phase change material is reduced. This may reduce the power consumption of the resulting phase change memory. The reduction in power consumption may be achieved by forming distinct layers of phase change material that have little or no mixing between them outside the programmed volume. For example, in one embodiment, a diffusion barrier layer may be maintained between the two distinct phase change layers. In another embodiment, a face centered cubic chalcogenide structure may be utilized.
1. A phase change memory comprising:
a first electrode;
a second electrode;
a first phase change layer formed between said first and second electrodes;
a second phase change layer formed between said first and second electrodes; and
a diffusion barrier formed between said first and second phase change layers, wherein said first phase change layer contacts said first electrode and said second electrode.
2. The memory of claim 1 wherein said diffusion barrier comprises oxygen or nitrogen.
3. The memory of claim 1 wherein said first phase change layer includes hexagonal close packed chalcogenide.
4. The memory of claim 1 wherein said first phase change layer has a thickness of less than its phonon mean free path.
5. The memory of claim 1 wherein said first and second phase change layers are substantially planar.
6. The memory of claim 1 wherein said first and second phase change layers are substantially non-planar.
7. The memory of claim 6 wherein said first and second phase change layers are U-shaped.
8. The memory of claim 1 wherein said first phase change layer includes a horizontal portion and a non-horizontal portion.
9. The memory of claim 8 wherein said non-horizontal portion is a vertical portion.
10. The memory of claim 1 further including an ovonic threshold switch coupled to said memory element.
11. The memory of claim 1 wherein said second phase change layer contacts said first electrode and does not contact said second electrode.
12. The memory of claim 1 wherein said first phase change layer completely covers said first electrode.
13. The memory of claim 1 further including an insulator formed between said first and second electrodes and a pore formed in said insulator, said first and second phase change layers being formed in said pore.
14. The memory of claim 13 wherein said first phase change layer lines said pore.
15. The memory of claim 14 wherein said second phase change layer lines said first layer.
16. The memory of claim 1 further comprising a third phase change layer between said first and second electrodes.
17. The memory of claim 16 further comprising a second diffusion barrier between said second and third phase change layers.
18. The memory of claim 1 further comprising a processor coupled to said phase change memory and a static random access memory coupled to said processor.