Memory cell with resistance-switching layers
View Patent ↗A memory device in a 3-D read and write memory includes memory cells. Each memory cell includes a resistance-switching memory element (RSME) in series with a steering element. The RSME has first and second resistance-switching layers on either side of a conductive intermediate layer, and first and second electrodes at either end of the RSME. The first and second resistance-switching layers can both have a bipolar or unipolar switching characteristic. In a set or reset operation of the memory cell, an electric field is applied across the first and second electrodes. An ionic current flows in the resistance-switching layers, contributing to a switching mechanism. An electron flow, which does not contribute to the switching mechanism, is reduced due to scattering by the conductive intermediate layer, to avoid damage to the steering element. Particular materials and combinations of materials for the different layers of the RSME are provided.
1. A resistance-switching memory cell, comprising:
first and second electrodes;
a conductive or semiconductive intermediate layer electrically between, and in series with, the first and second electrodes;
a first resistance-switching layer electrically between, and in series with, the first electrode and the conductive or semiconductive intermediate layer; and
a second resistance-switching layer electrically between, and in series with, the second electrode and the conductive or semiconductive intermediate layer, the first and second resistance-switching layers both have a bipolar switching characteristic or both have a unipolar switching characteristic, wherein the conductive or semiconductive intermediate layer is a scattering layer which scatters charge carriers which enter the conductive or semiconductive intermediate layer from at least one of the first or second resistance-switching layers when potentials are set at the first and second electrodes.
2. The resistance-switching memory cell of claim 1 , wherein:
the resistance-switching memory cell stores data in a first data state when a set process is performed for the first and second resistance-switching layers, and in a second data state when a reset process is performed for the first and second resistance-switching layers.
3. The resistance-switching memory cell of claim 1 , wherein:
the resistance-switching memory cell stores data in a first data state when a set process is performed for at least one of the first or second resistance-switching layers, and in a second data state when a reset process is performed for the at least one of the first and second resistance-switching layers.
4. The resistance-switching memory cell of claim 1 , further comprising:
a diode steering element in series with the first and second electrodes, the conductive or semiconductive intermediate layer, and the first and second resistance-switching layers.
5. The resistance-switching memory cell of claim 1 , wherein:
the first resistance-switching layer has a first I-V characteristic; and
the second resistance-switching layer has a different, second I-V characteristic.
6. The resistance-switching memory cell of claim 1 , wherein:
the first and second resistance-switching layers have different set voltages.
7. The resistance-switching memory cell of claim 1 , wherein:
the first and second resistance-switching layers have different reset voltages.
8. The resistance-switching memory cell of claim 1 , wherein:
the first and second resistance-switching layers have different switching characteristics.
9. The resistance-switching memory cell of claim 1 , wherein:
the conductive or semiconductive intermediate layer is one of a plurality of conductive or semiconductive intermediate layers electrically between, and in series with, the first and second electrodes, the plurality of conductive or semiconductive intermediate layers are of different types which have different scattering properties and work functions.
10. The resistance-switching memory cell of claim 1 , further comprising:
an additional resistance-switching layer electrically between, and in series with, the conductive or semiconductive intermediate layer and the second electrode; and
an additional conductive or semiconductive intermediate layer electrically between, and in series with, the additional resistance-switching layer and the second electrode, the conductive or semiconductive intermediate layers are of different types which have different scattering properties and work functions.
11. A resistance-switching memory cell, comprising:
a diode steering element; and
a resistance-switching memory element in series with the diode steering element, the resistance-switching memory element comprising:
first and second electrodes;
a conductive or semiconductive intermediate layer electrically between, and in series with, the first and second electrodes;
a first resistance-switching layer electrically between, and in series with, the first electrode and the conductive or semiconductive intermediate layer; and
a second resistance-switching layer electrically between, and in series with, the second electrode and the conductive or semiconductive intermediate layer, wherein the conductive or semiconductive intermediate layer is a scattering layer which scatters charge carriers which enter the conductive or semiconductive intermediate layer from at least one of the first and second resistance-switching layers when potentials are set at the first and second electrodes.
12. The resistance-switching memory cell of claim 11 , wherein:
the first and second resistance-switching layers both have a bipolar switching characteristic.
13. The resistance-switching memory cell of claim 11 , wherein:
the first and second resistance-switching layers both have a unipolar switching characteristic.
14. The resistance-switching memory cell of claim 11 , wherein:
the first resistance-switching layer has a first I-V characteristic; and
the second resistance-switching layer has a different, second I-V characteristic.
15. The resistance-switching memory cell of claim 14 , wherein:
the second I-V characteristic is opposite in polarity to the first I-V characteristic.
16. A memory device, comprising:
a memory array comprising a plurality of resistance-switching memory cells, each resistance-switching memory cell comprising a steering element in series with a resistance-switching memory element, each resistance-switching memory element comprising a respective intermediate layer electrically between respectivefirst and second resistance-switching layers;
a plurality of word lines and bit lines;
each resistance-switching memory cell having one end in communication with a respective bit line of the plurality of bit lines, and another end in communication with a respective word line of the plurality of word lines; and
control circuitry in communication with the plurality of word lines and bit lines, the control circuitry applies a voltage to at least one of the resistance-switching memory cells via the respective bit line and the word line thereof, to cause the at least one of the resistance-switching memory cells to switch from one resistance state to another resistance state, wherein for the at least one of the resistance-switching memory cells, the respective intermediate layer is a scattering layer which scatters charge carriers which enter the respective intermediate layer from at least one of the first or second respective resistance-switching layers when the voltage is set at the respective bit line and the word line thereof.
17. The memory device of claim 16 , wherein:
the control circuitry varies the voltage to switch the first and second resistance-switching layers of the at least one of the resistance-switching memory cells.
18. The memory device of claim 16 , wherein:
the respective first and second resistance-switching layers of the at least one of the resistance-switching memory cells both have a bipolar switching characteristic.
19. The memory device of claim 16 , wherein:
the respective first and second resistance-switching layers of the at least one of the resistance-switching memory cells both have a unipolar switching characteristic.
20. The memory device of claim 16 , wherein:
each steering element comprises a diode.