Shunted phase change memory
By using a resistive film as a shunt, the snapback exhibited when transitioning from the reset state or amorphous phase of a phase change material, may be reduced or avoided. The resistive film may be sufficiently resistive that it heats the phase change material and causes the appropriate phase transitions without requiring a dielectric breakdown of the phase change material.
1. A phase change memory comprising:
an upper electrode and a lower electrode;
a phase change material that includes at least a portion that transitions between amorphous and crystalline phases, said phase change material extending between said upper and lower electrodes; and
a resistive layer extending along said phase change material from said upper to said lower electrode to shunt the portion of the phase change material.
2. The memory of claim 1 including a pair of electrodes and said phase change material being positioned at least in part between said electrodes.
3. The memory of claim 2 wherein said resistive layer extends from one of said electrodes along said phase change material.
4. The memory of claim 3 wherein said resistive layer extends from one of said electrodes to another of said electrodes.
5. The memory of claim 2 wherein said electrodes are positioned one over another and an insulating film is located between said electrodes.
6. The memory of claim 5 including an opening in one of said electrodes, said phase change material extending into said opening.
7. The memory of claim 6 wherein said electrodes are separated by an insulating layer.
8. The memory of claim 1 wherein said resistive layer reduces snapback when transitioning the phase change material from the amorphous phase to the crystalline phase.
9. The memory of claim 1 wherein said resistive layer has a resistance and wherein the resistance of said resistive layer is higher than a set resistance of the phase change memory material.
10. The memory of claim 1 wherein said resistive layer has a resistance and wherein the resistance of said resistive layer is low enough so that when a voltage across the phase change material approaches a threshold voltage, the resistive layer heats up.
11. The memory of claim 9 wherein the resistive layer has a. resistance lower than a reset resistance of the phase change memory material and higher than the set resistance of the phase change memory material.