Cross-point memory cells, non-volatile memory arrays, methods of reading a memory cell, methods of programming a memory cell, methods of writing to and reading from a memory cell, and computer systems
Cross-point memory cells, non-volatile memory arrays, methods of reading a memory cell, methods of programming a memory cell, and methods of writing to and reading from a memory cell are described. In one embodiment, a cross-point memory cell includes a word line extending in a first direction, a bit line extending in a second direction different from the first direction, the bit line and the word line crossing without physically contacting each other, and a capacitor formed between the word line and the bit line where such cross. The capacitor comprises a dielectric material configured to prevent DC current from flowing from the word line to the bit line and from the bit line to the word line.
1. A memory cell comprising:
a first electrode;
a second electrode;
semiconductive material intermediate the first and second electrodes, the semiconductive material comprising a plurality of mobile dopants which move from a first region of the semiconductive material to a second region of the semiconductive material as a result of an application of a voltage across the first and second electrodes;
wherein a capacitance of the memory cell changes from a first capacitance corresponding to a first programmed state of the memory cell to a second capacitance corresponding to a second programmed state of the memory cell as a result of the movement of the mobile dopants; and
wherein the semiconductive material has different dielectric thicknesses when the memory cell is in the first and second programmed states.
2. The memory cell of claim 1 wherein the second region of the semiconductive material is electrically insulative when the memory cell is in the first programmed state and electrically conductive when the memory cell is in the second programmed state.
3. The memory cell of claim 1 wherein a concentration of the mobile dopants in the second region is increased as a result of the application of the voltage across the first and second electrodes.
4. The memory cell of claim 1 wherein the memory cell is configured to retain the second capacitance after the application of the voltage has been ceased.
5. A memory cell comprising:
a first electrode;
a second electrode;
semiconductive material intermediate the first and second electrodes, the semiconductive material comprising a plurality of mobile dopants which move from a first region of the semiconductive material to a second region of the semiconductive material as a result of an application of a voltage across the first and second electrodes;
a barrier material intermediate the semiconductive material and one of the first and second electrodes, and wherein the barrier material is impervious to movement of the mobile dopants from the semiconductive material to the barrier material; and
wherein a capacitance of the memory cell changes from a first capacitance corresponding to a first programmed state of the memory cell to a second capacitance corresponding to a second programmed state of the memory cell as a result of the movement of the mobile dopants.
6. The memory cell of claim 5 wherein the barrier material is adjacent to the second region of the semiconductive material.
7. The memory cell of claim 5 wherein the barrier material is electrically insulative.
8. The memory cell of claim 1 wherein the memory cell has an increased capacitance in the second programmed state compared with the first programmed state.
9. A memory cell comprising:
a capacitor configured to have at least two different capacitive states corresponding to different programmed states of the memory cell, the capacitor comprising:
a first electrode;
a second electrode; and
semiconductive material intermediate the first and second electrodes;
wherein a region of the semiconductive material is electrically insulative when the memory cell is in a first of the programmed states and electrically conductive when the memory cell is in a second of the programmed states;
wherein a plurality of mobile dopants move to the region of the semiconductive material as a result of an application of a voltage across the first and second electrodes, and the movement of the mobile dopants changes the region of the semiconductive material from being electrically insulative to electrically conductive; and
a barrier material intermediate the semiconductive material and one of the first and second electrodes, and wherein the barrier material is impervious to the movement of the mobile dopants.
10. The memory cell of claim 9 wherein the region of the semiconductive material is configured to remain electrically conductive after the application of the voltage across the first and second electrodes has been ceased.
11. The memory cell of claim 9 wherein the barrier material is adjacent to the region of the semiconductive material.
12. The memory cell of claim 9 wherein the barrier material is electrically insulative.
13. The memory cell of claim 9 wherein a concentration of the mobile dopants in the region of the semiconductive material is increased as a result of the application of the voltage across the first and second electrodes.
14. The memory cell of claim 9 wherein the capacitor has an increased capacitance when the memory cell is in the second programmed state compared with the first programmed state.
15. A memory cell comprising:
a capacitor configured to have at least two different capacitive states corresponding to different programmed states of the memory cell, the capacitor comprising:
a first electrode;
a second electrode; and
semiconductive material intermediate the first and second electrodes; and
wherein a region of the semiconductive material is electrically insulative when the memory cell is in a first of the programmed states and electrically conductive when the memory cell is in a second of the programmed states; and
wherein the semiconductive material has different dielectric thicknesses when the memory cell is in the first and second programmed states.
16. A memory cell comprising:
a capacitor configured to have different capacitive states corresponding to different programmed states of the memory cell, the capacitor comprising:
a first electrode;
a second electrode; and
semiconductive material intermediate the first and second electrodes;
wherein the capacitor is configured to change from a first capacitance corresponding to a first of the programmed states of the memory cell to a second capacitance corresponding to a second of the programmed states of the memory cell as a result of an application of a voltage across the first and second electrodes, and wherein the first and second capacitances are different;
wherein the semiconductive material comprises a plurality of mobile dopants which move from a first region of the semiconductive material to a second region of the semiconductive material as a result of the application of the voltage across the first and second electrodes; and
a barrier material intermediate the semiconductive material and one of the first and second electrodes, and wherein the barrier material is impervious to the movement of the mobile dopants.
17. The memory cell of claim 16 wherein a region of the semiconductive material is electrically insulative when the memory cell is in the first programmed state and electrically conductive when the memory cell is in the second programmed state.
18. The memory cell of claim 16 wherein the capacitor is configured to retain the second capacitance after the application of the voltage has been ceased.
19. The memory cell of claim 16 wherein a concentration of the mobile dopants in the second region increases as a result of the application of the voltage across the first and second electrodes.
20. The memory cell of claim 16 wherein the barrier material is adjacent to the second region of the semiconductive material.
21. The memory cell of claim 16 wherein the barrier material is electrically insulative.
22. A memory cell comprising:
a capacitor configured to have different capacitive states corresponding to different programmed states of the memory cell, the capacitor comprising:
a first electrode;
a second electrode; and
semiconductive material intermediate the first and second electrodes;
wherein the capacitor is configured to change from a first capacitance corresponding to a first of the programmed states of the memory cell to a second capacitance corresponding to a second of the programmed states of the memory cell as a result of an application of a voltage across the first and second electrodes, and wherein the first and second capacitances are different; and
wherein the semiconductive material has different dielectric thicknesses when the memory cell is in the first and second programmed states.
23. A memory cell programming method comprising:
first applying a first voltage across a memory cell comprising a first electrically conductive region, a second electrically conductive region, and an electrically insulative region between the first and second electrically conductive regions;
wherein the first applying increases a thickness of one of the first and second electrically conductive regions in a direction towards the other of the first and second electrically conductive regions and the first applying changes the memory cell from a first programmed state to a second programmed state;
second applying a second voltage across the memory cell after the first applying; and
wherein the second applying decreases the thickness of the one of the first and second electrically conductive regions and the second applying changes the memory cell from the second programmed state to the first programmed state.
24. The method of claim 23 wherein the first applying changes a region of semiconductive material between the first and second electrically conductive regions from being electrically insulative to electrically conductive.
25. The method of claim 23 wherein the first applying changes a dielectric thickness of a semiconductive material between the first and second electrically conductive regions.
26. The method of claim 23 wherein the first and second applyings individually cause a plurality of mobile dopants to move between different regions of semiconductive material between the first and second electrically conductive regions.
27. The method of claim 23 wherein the first applying changes a capacitance of the memory cell from a first capacitive state corresponding to the first programmed state to a second capacitive state corresponding to the second programmed state.
28. The method of claim 23 wherein the first and second applyings comprise applying the first and second voltages having opposite polarities across the memory cell.