Memory element with a reactive metal layer
View Patent ↗A memory cell including conductive oxide electrodes is disclosed. The memory cell includes a memory element operative to store data as a plurality of resistive states. The memory element includes a layer of a conductive metal oxide (CMO) (e.g., a perovskite) in contact with an electrode that may comprise one or more layers of material. At least one of those layers of material can be a conductive oxide (e.g., a perovskite such as LaSrCoO 3 -LSCoO or LaNiO 3 -LNO) that is in contact with the CMO. The conductive oxide layer can be selected as a seed layer operative to provide a good lattice match with and/or a lower crystallization temperature for the CMO. The conductive oxide layer may also be in contact with a metal layer (e.g., Pt). The memory cell additionally exhibits non-linear IV characteristics, which can be favorable in certain arrays, such as non-volatile two-terminal cross-point memory arrays.
1. A method, comprising:
forming a memory element (ME) having exactly two terminals, the forming including:
depositing a bottom electrode (BE) operative as a first terminal of the ME;
depositing a first layer after depositing the BE, the first layer comprising a conductive metal oxide (CMO) second layer and a Tantalum-based third layer in direct contact with the CMO second layer, the first layer operative to store at least one bit of data as a plurality of resistive states;
depositing a top electrode (TE) operative as a second terminal of the ME after depositing the first layer;
wherein the CMO second layer and the Tantalum-based third layer are electrically in series with each other and with the first and second terminals;
wherein the ME is reversibly switchable between a plurality of different resistive states by applying a write voltage across the first and second terminals, the plurality of different resistive states are retained in the absence of electrical power, and the ME has a first non-linear I-V characteristic for all values of the plurality of different resistive states.
2. The method of claim 1 , wherein the Tantalum-based third layer comprises Ta 2 O 2 :Cr.
3. The method of claim 1 , wherein the CMO second layer comprises a perovskite.
4. The method of claim 1 , wherein the TE, the BE, or both comprise Pt.
5. The method of claim 1 , further comprising annealing the Tantalum-based third layer.
6. The method of claim 5 , wherein the annealing occurs in a non-reactive ambient.
7. The method of claim 1 , further comprising:
providing a substrate including active circuitry, wherein the active circuitry is fabricated front-end-of-the-line (FEOL) on the substrate, and
wherein the forming occurs after the providing so that the ME is fabricated post FEOL directly above the active circuitry and at least a portion of the active circuitry is electrically coupled with the first and second terminals of the ME.
8. The method of claim 1 , further comprising:
forming a non-ohmic device (NOD) that is electrically in series with the ME, wherein the forming of the NOD occurs after the depositing of the BE, and the NOD including a second non-linear I-V characteristic that is different than the first non-linear I-V characteristic.
9. The method of claim 8 , wherein the forming of the NOD further comprises:
depositing an insulating material; and
depositing a conductive material such that the NOD comprises a metal-insulator-metal (MIM) structure.
10. The method of claim 8 , wherein the forming of the NOD is prior to the depositing of the TE.
11. The method of claim 8 , wherein the forming of the NOD is after the depositing of the TE.
12. The method of claim 1 , wherein the plurality of different resistive states are non-destructively determinable by applying a read voltage across the first and second terminals of the ME.
13. The method of claim 1 , further comprising removing an unreacted portion of the first layer.
14. The method of claim 13 , wherein the removed portion corresponds to the Tantalum-based third layer.
15. The method of claim 1 , further comprising:
improving a switching characteristic of the ME by treating at least a portion of the first layer before depositing the TE,
wherein the treating is operative to form an integrated non-ohmic device (NOD) that is electrically in series with the ME, the integrated NOD including a second non-linear I-V characteristic that is different than the first non-linear I-V characteristic.