Large bit-per-cell three-dimensional mask-programmable read-only memory
View Patent ↗A large bit-per-cell three-dimensional mask-programmable read-only memory (3D-MPROM B ) is disclosed. It can achieve large bit-per-cell (e.g. 4-bpc or more). 3D-MPROM B can be realized by adding resistive layer(s) or resistive element(s) to the memory cells.
1. A three-dimensional mask-programmable read-only memory including a plurality of mask-programmable read-only memory levels stacked above and coupled to a semiconductor substrate, comprising:
a first memory cell comprising a first resistive layer;
a second memory cell comprising a second resistive layer;
a third memory cell comprising said first and second resistive layers;
wherein each of said first, second and third memory cells comprises a quasi-conduction layer, and said first, second and third memory cells have different current-voltage characteristics.
2. The three-dimensional mask-programmable read-only memory according to claim 1 , wherein selected one of said first and second resistive layers has a resistance comparable to or larger than said quasi-conduction layer at threshold current.
3. The three-dimensional mask-programmable read-only memory according to claim 1 , wherein selected one of said first and second resistive layers is above said quasi-conduction layer.
4. The three-dimensional mask-programmable read-only memory according to claim 1 , wherein selected one of said first and second resistive layers is in said quasi-conduction layer.
5. The three-dimensional mask-programmable read-only memory according to claim 1 , wherein selected one of said first and second resistive layers is below said quasi-conduction layer.
6. The three-dimensional mask-programmable read-only memory according to claim 1 , wherein selected one of said first and second resistive layers comprises at least one semiconductor layer.
7. The three-dimensional mask-programmable read-only memory according to claim 1 , wherein selected one of said first and second resistive layers comprises at least one dielectric layer.
8. A three-dimensional mask-programmable read-only memory including a plurality of mask-programmable read-only memory levels stacked above and coupled to a semiconductor substrate, comprising:
a first memory cell comprising a first quasi-conduction layer;
a second memory cell comprising a second quasi-conduction layer, said second quasi-conductor layer comprising more concentration of at least one resistive element than said first quasi-conductor layer;
wherein the memory cells in said memory have N (N>2) states, and memory cells in different states have different current-voltage characteristics.
9. The three-dimensional mask-programmable read-only memory according to claim 8 , wherein the material in said second quasi-conduction layer has a higher resistivity than the material in said first quasi-conduction layer.
10. The three-dimensional mask-programmable read-only memory according to claim 8 , wherein the material in said second quasi-conduction layer has a larger bandgap than the material in said first quasi-conduction layer.
11. The three-dimensional mask-programmable read-only memory according to claim 8 , wherein said resistive element is selected from a group of elements consisting of oxygen, nitrogen and carbon.
12. The three-dimensional mask-programmable read-only memory according to claim 8 , further comprising a third memory cell, wherein said third memory cell comprises at least a resistive layer.