Forming phase change memory arrays
View Patent ↗A phase change memory may be formed to have a dimension that is sub-lithographic in one embodiment by forming a surface feature over the phase change material, and coating the surface feature with a mask of sub-lithographic dimensions. The horizontal portions of the mask and the surface feature may then be removed and the remaining portions of the mask may be used to define a dimension of said phase change material. Another dimension of the phase change material may be defined using an upper electrode extending over said phase change material as a mask to etch the phase change material.
1. A method comprising:
forming, over a surface feature, a mask including two vertical and one non-vertical portions;
removing said surface feature and the non-vertical portion of said mask; and
using said vertical portions of said mask as a mask to etch a phase change material to define two cells in said phase change material at the same time.
2. The method of claim 1 including forming a layer of phase change material over a substrate, defining a feature over said phase change material, covering said feature with a deposited mask and removing a horizontal portion of said mask.
3. The method of claim 2 including forming a vertical portion on two opposed ends of said feature and using said vertical portions to define two cells in said phase change material.
4. The method of claim 3 including defining said cells at sublithographic feature size.
5. The method of claim 3 including forming said mask at a thickness less than a lithographic feature size.
6. The method of claim 1 including defining a phase change material stack including at least two opposed electrodes and an intervening layer of phase change material and etching said stack using said mask.
7. The method of claim 1 including covering said etched phase change material with an encapsulation layer.
8. The method of claim 1 including forming a first set of electrodes under said phase change material and forming a second set of electrodes extending transversely to said first set extending over said phase change material.
9. The method of claim 8 including using said second set of electrodes as a mask to etch said phase change material.