Ovonic threshold switch (OTS) driver/selector uses unselect bias to pre-charge memory chip circuit and reduces unacceptable false selects
The present disclosure generally relates to non-volatile memory arrays and memory devices in which a leakage current through an OTS is utilized to pre-charge a circuit of a memory chip. By running an additional wire on each side of a tile which is orthogonal to, above, or below the X and Y select wires, a high value resistance material, such as an OTS, may be deposited at the intersection. The OTS allows the word line or bit line to be selected without pulling excessive leakage to the select wire from the bias voltage, such as V/2. A thickness of the OTS is adjusted such that the V t of the OTS is greater than V/2, with margin, and the OTS does not turn on when the OTS is selected. A resistance is created between the V/2 wire and the word line select wire or the bit line select wire.
1. A memory device, comprising:
a word line;
a bit line disposed perpendicular to the word line;
a memory element disposed between the word line and the bit line;
a select element coupled to the memory element, wherein the select element is disposed adjacent to the bit line wherein the select element is selected from the group consisting of an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST);
a wire that at least partly overlaps the word line, the wire coupled with a voltage source providing a predefined unselect bias voltage; and
a connecting element comprising an undoped polysilicon material disposed between the word line and the wire wherein the connecting element comprises a second memory element and a second select element, wherein the second select element is constructed from one of a RRAM and a MRAM material.
2. The memory device of claim 1 , wherein the connecting element comprises an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST).
3. The memory device of claim 1 , wherein the second memory element comprises a Resistive Random Access Memory (RRAM) material, and wherein the second select element comprises an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST).
4. The memory device of claim 1 , wherein the memory element is in series with the select element.
5. The memory device of claim 1 , wherein the memory element is a Resistive Random Access Memory (RRAM) device or a Phase Change Memory (PCM) device.
6. The memory device of claim 1 ,
wherein the word line is disposed at a first conductive layer and the bit line is disposed at a different second conductive layer, and
wherein the wire is disposed at the second conductive layer.
7. The memory device of claim 6 ,
wherein the word line has a first longitudinal axis and the bit line has a second longitudinal axis that is perpendicular to the first longitudinal axis, and
wherein the wire is substantially parallel to the second longitudinal axis.
8. The memory device of claim 6 , wherein the connecting element comprises an ovonic threshold switch (OTS), wherein a thickness of the OTS between the first conductive layer and the second conductive layer is selected such that a threshold voltage of the OTS is greater than the predefined unselect bias voltage and such that the OTS does not turn on when the OTS is selected.
9. A memory device, comprising:
a word line;
a bit line disposed perpendicular to the word line;
a memory element disposed between the word line and the bit line;
a select element coupled to the memory element, wherein the select element is disposed adjacent to the bit line;
a wire that at least partly overlaps the word line, the wire coupled with a voltage source providing a predefined unselect bias voltage; and
a connecting element disposed between the word line and the wire wherein the connecting element comprises a second memory element and a second select element, wherein the second select element is constructed from one of a RRAM and a MRAM material wherein the connecting element comprises an undoped polysilicon material.
10. A memory device, comprising:
a word line;
a bit line disposed perpendicular to the word line;
a memory element disposed between the word line and the bit line;
a select element comprised of an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST), the select element coupled to the memory element, wherein the select element is disposed adjacent to the word line;
a wire that at least partly overlaps the bit line, the wire coupled with a voltage source providing a predefined unselect bias voltage; and
a connecting element wherein the connecting element comprises an undoped polysilicon material, the connecting element disposed between the bit line and the wire wherein the connecting element comprises a second memory element and a second select element wherein the second select element is constructed from one of a RRAM and a MRAM material.
11. The memory device of claim 10 , wherein the connecting element comprises an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST).
12. The memory device of claim 10 , wherein the second memory element comprises a Resistive Random Access Memory (RRAM) material, and wherein the second select element comprises an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST).
13. The memory device of claim 10 , wherein the memory element is in series with the select element.
14. The memory device of claim 10 , wherein the memory element is a Resistive Random Access Memory (RRAM) device or a Phase Change Memory (PCM) device.
15. A memory device, comprising:
a word line;
a bit line disposed perpendicular to the word line;
a memory element disposed between the word line and the bit line;
a select element coupled to the memory element, wherein the select element is disposed adjacent to the word line;
a wire that at least partly overlaps the bit line, the wire coupled with a voltage source providing a predefined unselect bias voltage; and
a connecting element disposed between the bit line and the wire wherein the connecting element comprises a second memory element and a second select element wherein the second select element is constructed from one of a RRAM and a MRAM material wherein the connecting element comprises an undoped polysilicon material.
16. A memory array, comprising:
a plurality of word lines;
a plurality of bit lines that are disposed perpendicular to the plurality of word lines wherein (i) each word line of the plurality of word lines or (ii) each bit line of the plurality of bit lines is connected with a respective connecting element of the plurality of connecting elements in the memory array;
a plurality of memory devices, each memory device of the plurality of memory devices disposed between a respective word line of the plurality of word lines and a respective bit line of the plurality of bit lines, each memory device respectively comprising:
a memory element; and
a select element coupled to the memory element, wherein the select element is disposed adjacent to the respective word line or to the respective bit line;
a wire that at least partly overlaps (i) each of the plurality of word lines or (ii) each of the plurality of bit lines, the wire coupled with a voltage source providing a predefined unselect bias voltage; and
a plurality of connecting elements, each connecting element of the plurality of connecting elements disposed between (i) the wire and a respective word line of the plurality of word lines or (ii) the wire and a respective bit line of the plurality of bit lines wherein each connecting element of the plurality of connecting elements respectively comprises a second memory element and a second select element wherein the second select element is constructed from one of a RRAM and a MRAM material wherein each connecting element of the plurality of connecting elements comprises an undoped polysilicon material.
17. The memory array of claim 16 , wherein the select element is an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST).
18. The memory array of claim 16 , wherein each connecting element of the plurality of connecting elements comprises an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST).
19. The memory array of claim 16 , wherein the second memory element comprises a Resistive Random Access Memory (RRAM) material, and wherein the second select element comprises an ovonic threshold switch (OTS), a doped chalcogenide alloy, a thin film silicon, a metal-metal oxide switch, or a Field Assisted Superlinear Threshold selector (FAST).
20. The memory array of claim 16 , wherein the memory element is in series with the select element.
21. The memory array of claim 16 , wherein the memory element is a Resistive Random Access Memory (RRAM) device or a Phase Change Memory (PCM) device.
22. A memory array, comprising:
a plurality of word lines;
a plurality of bit lines that are disposed perpendicular to the plurality of word lines;
a plurality of memory devices, each memory device of the plurality of memory devices disposed between a respective word line of the plurality of word lines and a respective bit line of the plurality of bit lines, each memory device respectively comprising:
a memory element; and
a select element coupled to the memory element, wherein the select element is disposed adjacent to the respective word line or to the respective bit line;
a wire that at least partly overlaps (i) each of the plurality of word lines or (ii) each of the plurality of bit lines, the wire coupled with a voltage source providing a predefined unselect bias voltage; and
a plurality of connecting elements, each connecting element of the plurality of connecting elements disposed between (i) the wire and a respective word line of the plurality of word lines or (ii) the wire and a respective bit line of the plurality of bit lines wherein each connecting element of the plurality of connecting elements respectively comprises a second memory element and a second select element wherein the second select element is constructed from one of a RRAM and a MRAM material wherein each connecting element of the plurality of connecting elements comprises an undoped polysilicon material.