Non-volatile memory devices and methods of fabricating the same
View Patent ↗Non-volatile memory devices and methods of fabricating the same are disclosed. A disclosed non-volatile memory device includes: a tunnel oxide layer formed on a semiconductor substrate and having an energy bandgap; a storage oxide layer formed on the tunnel oxide layer and having an energy bandgap which is smaller than the energy bandgap of the tunnel oxide layer; a block oxide layer formed on the storage oxide layer and having an energy bandgap greater than the energy bandgap of the storage oxide layer; and a gate formed on the block oxide layer.
1. A non-volatile memory device comprising:
a tunnel oxide layer comprising a first tunnel oxide layer on a semiconductor substrate and a second tunnel oxide layer on the first tunnel oxide layer, the first tunnel oxide layer having an energy bandgap less than an energy bandgap of the second tunnel oxide layer,
a storage oxide layer on the tunnel oxide layer, the storage oxide layer having an energy bandgap which is smaller than the energy bandgap of the first tunnel oxide layer;
a block oxide layer on the storage oxide layer, the block oxide layer having an energy bandgap greater than the energy bandgap of the storage oxide layer, and
a gate on the block oxide layer.
2. A non-volatile memory device as defined in claim 1 , wherein each of the tunnel oxide layer and the block oxide layer has a conduction band, and the conduction bands of the tunnel oxide layer and the block oxide layer are greater than a conduction band of the storage oxide layer, such that an electric potential barrier between the tunnel oxide layer and the storage oxide layer and an electric potential barrier between the block oxide layer and the storage layer define an electric charge well.
3. A non-volatile memory device as defined in claim 2 , wherein electrons flow from the semiconductor substrate over the electric potential barrier between the semiconductor substrate and the tunnel oxide layer and are stored within the electric charge well by a hot carrier injection technique during a programming operation.
4. A non-volatile memory device as defined in claim 2 , wherein electrons tunnel through the tunnel oxide layer to flow from the electric charge well to the semiconductor substrate by a direct tunneling or an F-N tunneling technique during an erasing operation.
5. A non-volatile memory device as defined in claim 1 , wherein the tunnel oxide layer comprises one or more of SiO 2 , Al 2 O 3 , or Y 2 O 3 .
6. A non-volatile memory device as defined in claim 1 , wherein the storage oxide layer comprises one or more of HfO 2 , ZrO 2 , BaZrO 2 , BaTiO 3 , Ta 2 O 5 , CaO, SrO, BaO, La 2 O 3 , Ce 2 O 3 , Pr 2 O 3 , Nd 2 O 3 , Pm 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Tb 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 , or Lu 2 O 3 .
7. A non-volatile memory device as defined in claim 1 , wherein the block oxide layer comprises one or more of SiO 2 , Al 2 O 3 , or Y 2 O 3 .
8. A non-volatile memory device as defined in claim 1 , wherein the tunnel oxide layer has a thickness in a range of about 30–150 Å.
9. A non-volatile memory device as defined in claim 1 , wherein the storage oxide layer has a thickness in a range of about 40–500 Å.
10. A non-volatile memory device as defined in claim 1 , wherein the block oxide layer has a thickness in a range of about 40–200 Å.
11. A non-volatile memory device as defined in claim 1 , wherein the first tunnel oxide layer is thicker than the second tunnel oxide layer.
12. A non-volatile memory device as defined in claim 11 , wherein the first tunnel oxide layer has a thickness in a range of about 30–150 Å.
13. A non-volatile memory device as defined in claim 11 , wherein the second tunnel oxide layer has a thickness in a range of about 5–40 Å.
14. A non-volatile memory device as defined in claim 11 , wherein the first tunnel oxide layer comprises one or more of HfO 2 , ZrO 2 , BaZrO 2 , BaTiO 3 , Ta 2 O 5 , CaO, SrO, BaO, La 2 O 3 , Ce 2 O 3 , Pr 2 O 3 , Nd 2 O 3 , Pm 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Tb 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 , or Lu 2 O 3 .
15. A non-volatile memory device as defined in claim 11 , wherein the second tunnel oxide layer comprises one or more of SiO 2 , Al 2 O 3 , or Y 2 O 3 .
16. A non-volatile memory device as defined in claim 1 , wherein an electric potential barrier between the second tunnel oxide layer and the storage oxide layer is greater than an electric potential barrier formed between the first and second tunnel oxide layers.
17. A non-volatile memory device as defined in claim 11 , wherein each of the second tunnel oxide layer and the block oxide layer has a conduction band, and the conduction bands of the second tunnel oxide layer and the block oxide layer are higher than a conduction band of the storage oxide layer, such that an electric potential barrier between the first tunnel oxide layer and the storage oxide layer and an electric potential barrier between the block oxide layer and the storage oxide layer define an electric charge well.
18. A non-volatile memory device as defined in claim 1 , wherein the block oxide layer includes a first block oxide layer on the storage oxide layer and a second block oxide layer on the first block oxide layer, the second block oxide layer having an energy bandgap greater than the energy bandgap of the storage oxide layer and less than the energy bandgap of the first block oxide layer.
19. A non-volatile memory device as defined in claim 18 , wherein the second block oxide layer is thicker than the first block oxide layer.
20. A non-volatile memory device as defined in claim 18 , wherein the first block oxide layer has a thickness in a range of about 10–50 Å.
21. A non-volatile memory device as defined in claim 18 , wherein the second block oxide layer has thickness in a range of about 40–200 Å.
22. A non-volatile memory device as defined in claim 18 , wherein the first block oxide layer comprises one or more of SiO 2 , Al 2 O 3 , or Y 2 O 3 .
23. A non-volatile memory device as defined in claim 18 , wherein the second block oxide layer comprises one or more of HfO 2 , ZrO 2 , BaZrO 2 , BaTiO 3 , Ta 2 O 5 , CaO, SrO, BaO, La 2 O 3 , Ce 2 O 3 , Pr 2 O 3 , Nd 2 O 3 , Pm 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Tb 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 , or Lu 2 O 3 .
24. A non-volatile memory device as defined in claim 18 , wherein an electric potential barrier between the first block oxide layer and the storage layer is greater than an electric potential barrier between the first and second block oxide layers.
25. A non-volatile memory device as defined in claim 18 , wherein conduction bands of the tunnel oxide layer and the first block oxide layer are greater than a conduction band of the storage oxide layer such that an electric charge well is defined by electric potential barriers formed between the tunnel oxide layer and the storage oxide layer and between the first block oxide layer and the storage oxide layer.