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 quasi-conduction layer;
a second memory cell comprising a second quasi-conduction layer and a resistive layer, wherein said resistive layer is not an insulating layer;
a third memory cell comprising a third quasi-conduction layer different from said first quasi-conduction layer;
wherein 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 said third quasi-conduction layer comprises more concentration of at least one resistive element than said first quasi-conduction layer.
3. The three-dimensional mask-programmable read-only memory according to claim 2 , wherein said resistive element increases the resistance of said third quasi-conduction layer.
4. The three-dimensional mask-programmable read-only memory according to claim 2 , wherein said resistive element is selected from a group of elements consisting of oxygen, nitrogen and carbon.
5. The three-dimensional mask-programmable read-only memory according to claim 1 , wherein said resistive layer has a resistance comparable to said second quasi-conduction layer.
6. 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 and a resistive layer, wherein said resistive layer has a resistance comparable to said second quasi-conduction layer;
a third memory cell comprising a third quasi-conduction layer different from said first quasi-conduction layer;
wherein said first, second and third memory cells have different current-voltage characteristics.
7. The three-dimensional mask-programmable read-only memory according to claim 6 , wherein said third quasi-conduction layer comprises more concentration of at least one resistive element than said first quasi-conduction layer.
8. The three-dimensional mask-programmable read-only memory according to claim 7 , wherein said resistive element increases the resistance of said third quasi-conduction layer.
9. The three-dimensional mask-programmable read-only memory according to claim 7 , wherein said resistive element is selected from a group of elements consisting of oxygen, nitrogen and carbon.
10. The three-dimensional mask-programmable read-only memory according to claim 6 , wherein said resistive layer is not an insulating layer.