Switchable resistive memory with opposite polarity write pulses
A rewriteable nonvolatile memory includes a thin film transistor and a switchable resistor memory element in series. The switchable resistor element decreases resistance when subjected to a set voltage magnitude applied in a first direction, and increases resistance when subjected to a reset voltage magnitude applied in a second direction opposite the first. The memory cell is formed in an array, such as a monolithic three dimensional memory array in which multiple memory levels are formed above a single substrate. The thin film transistor and a switchable resistor memory element are electrically disposed between a data line and a reference line which are parallel. A select line extending perpendicular to the data line and the reference line controls the transistor.
1. A nonvolatile memory cell comprising:
a switchable resistor memory element; and
a thin film transistor having a channel region,
wherein both a reference line and a data line are disposed below the channel region of the thin film transistor,
wherein the switchable resistor memory element is disposed in series with the thin film transistor,
wherein the switchable resistor memory element decreases resistance when a set voltage magnitude is applied across the switchable resistor memory element, and
wherein the switchable resistor memory element increases resistance when a reset voltage magnitude is applied across the switchable resistor memory element, and wherein the polarity of the set voltage magnitude is opposite the polarity of the reset voltage magnitude.
2. The nonvolatile memory cell of claim 1 wherein the switchable resistor memory element comprises a perovskite material.
3. The nonvolatile memory cell of claim 1 wherein the switchable resistor memory element comprises amorphous silicon doped with an element selected from the group consisting of V, Co, Ni, Pd, Fe, and Mn.
4. The nonvolatile memory cell of claim 1 wherein the switchable resistor memory element comprises a carbon-polymer film.
5. The nonvolatile memory cell of claim 1 wherein the switchable resistor memory element comprises a solid electrolyte material.
6. The nonvolatile memory cell of claim 5 wherein the solid electrolyte material comprises chalcogenide glass having the formula A x B y ,
wherein A is selected from the group consisting of B, Al, Ga, In, Ti, C, Si, Ge, Sn, Pb, N, P, As, Sb, Bi, F, Cl, Br, I and At and
wherein B is Si, Se, Te, or alloys or compounds thereof.
7. The nonvolatile memory cell of claim 6 wherein the chalcogenide glass is doped with Ag, Au, Pt, Cu, Cd, Ir, Ru, Co, Cr, Mn or Ni.
8. The nonvolatile memory cell of claim 5 wherein a reservoir of mobile metal ions is in contact with the solid electrolyte material.
9. The nonvolatile memory cell of claim 1 wherein the transistor and switchable resistor memory element are electrically disposed between the data line and the reference line, the reference line substantially parallel to the data line.
10. The nonvolatile memory cell of claim 9 wherein the transistor is connected to a select line, the select line substantially perpendicular to the data line, wherein the select line controls the thin film transistor.
11. The nonvolatile memory cell of claim 10 wherein the channel region is not substantially vertical, and the data line and the reference line are substantially coplanar.
12. The nonvolatile memory cell of claim 11 wherein the switchable resistor memory element is disposed between the channel region and the data line.
13. The nonvolatile memory cell of claim 1 wherein the channel region comprises silicon, germanium or a germanium alloy.
14. The nonvolatile memory cell of claim 1 wherein the channel region is polycrystalline.
15. The nonvolatile memory cell of claim 1 wherein the set voltage magnitude is less than about 2 volts.
16. The nonvolatile memory cell of claim 1 wherein the reset voltage magnitude is less than about 2 volts.
17. The nonvolatile memory cell of claim 1 wherein the cell is a portion of a monolithic three dimensional memory array formed above a substrate.
18. The nonvolatile memory cell of claim 17 wherein the substrate comprises monocrystalline silicon.
19. The nonvolatile memory cell of claim 1 further comprising a select line extending perpendicular to the data line and to the reference line.
20. The nonvolatile memory cell of claim 19 wherein:
a gate electrode of the thin film transistor is electrically connected to or comprises a portion of the select line,
one of a source region or a drain region of the thin film transistor is formed directly on the data line and is electrically connected to the data line,
the switchable resistor memory element is electrically connected to the reference line and to the other one of the source region or the drain region of the thin film transistor, and
the data line extends parallel to the reference line.
21. The nonvolatile memory cell of claim 1 wherein the source region to the drain region direction in the thin film transistor is perpendicular to the direction of the data line and the reference line.
22. A nonvolatile memory cell comprising:
a switchable resistor memory element,
a thin film transistor having a channel region, a source region, a drain region and a gate electrode,
a select line,
a data line disposed below the channel region, and a reference line disposed below the channel region,
wherein:
the gate electrode of the thin film transistor is electrically connected to or comprises a portion of the select line,
one of the source region or the drain region of the thin film transistor is electrically connected to the data line,
the switchable resistor memory element is electrically connected to the reference line and to the other one of the source region or the drain region of the thin film transistor,
the select line extends perpendicular to the data line and to the reference line,
the data line extends parallel to the reference line,
the switchable resistor memory element is disposed in series with the thin film transistor,
the switchable resistor memory element decreases resistance when a set voltage magnitude is applied across the switchable resistor memory element, and
the switchable resistor memory element increases resistance when a reset voltage magnitude is applied across the switchable resistor memory element, and wherein the polarity of the set voltage magnitude is opposite the polarity of the reset voltage magnitude.
23. The nonvolatile memory cell of claim 22 wherein the switchable resistor memory element comprises a perovskite material.
24. The nonvolatile memory cell of claim 22 wherein the switchable resistor memory element comprises amorphous silicon doped with an element selected from the group consisting of V, Co, Ni, Pd, Fe, and Mn.
25. The nonvolatile memory cell of claim 22 wherein the switchable resistor memory element comprises a carbon-polymer film.
26. The nonvolatile memory cell of claim 22 wherein the switchable resistor memory element comprises a solid electrolyte material.
27. The nonvolatile memory cell of claim 26 wherein the solid electrolyte material comprises chalcogenide glass having the formula A x B y ,
wherein A is selected from the group consisting of B, Al, Ga, In, Ti, C, Si, Ge, Sn, Pb, N, P,As, Sb, Bi, F, Cl, Br, I and At,
wherein B is Si, Se, Te, or alloys or compounds thereof, and
wherein the chalcogenide glass is doped with Ag, Au, Pt, Cu, Cd, Ir, Ru, Co, Cr, Mn or Ni.
28. The nonvolatile memory cell of claim 26 wherein a reservoir of mobile metal ions is in contact with the solid electrolyte material.
29. The nonvolatile memory cell of claim 22 wherein the cell is a portion of a monolithic three dimensional memory array formed above a substrate.
30. The nonvolatile memory cell of claim 22 wherein the source region to the drain region direction in the thin film transistor is perpendicular to the direction of the data line and the reference line.
31. The nonvolatile memory cell of claim 22 wherein one of the source region or the drain region of the thin film transistor is formed directly on the data line.