Quad+bit storage in trap based flash design using single program and erase entity as logical cell
View Patent ↗Flash memory systems and methodologies are provided herein for facilitating single logical cell erasure and quad or more bit storage in a flash device. The single logical cell erasure can be accomplished by employing a single program and erase entity as a single logical cell. The single program and erase entity is a combination of neighboring drain/source regions of two adjacent physical memory cells. By mapping two adjacent physical cells as a single logical cell, the flash memory device can be programmed and erased on a single bit or variable bit length basis. The memory cells can contain four or more data states, and each of the two adjacent memory cells in the single program and erase entity can be programmed independently from each other. As a result, the single program and erase entity can store four or more bits.
1. A method of operating a flash device comprising,
programming a portion of or an entire of the flash device on a basis of a single program and erase entity, the single program and erase entity comprising two adjacent dual bit physical memory cells of the flash device as a single logical cell, the memory cells comprising four or more data states; and
erasing the portion of or the entire of the flash device on the basis of the single program and erase entity.
2. The method of claim 1 , wherein programming the flash device on the basis of the single program and erase entity comprises:
programming each of the two adjacent dual bit physical memory cells in the single program and erase entity independently from each other.
3. The method of claim 1 , wherein programming the flash device on a basis of a single program and erase entity comprises:
applying a program pulse to the portion of or the entire of the flash memory on the basis of the single program and erase entity.
4. The method of claim 1 , wherein programming the flash device on a basis of a single program and erase entity comprises:
applying a program gate voltage to a gate, applying a program bitline voltage to a common bitline of the single program and erase entity that is shared by the two adjacent dual bit physical memory cells, and connecting at least one of two non-common bitlines of the single program and erase entity that are not shared by the two adjacent dual bit physical memory cells to ground.
5. The method of claim 4 , wherein the program gate voltage comprises a hot-electron-injection gate voltage and the program bitline voltage comprises a hot-electron-injection bitline voltage.
6. The method of claim 1 , wherein erasing the flash device on the basis of the single program and erase entity comprises:
applying an erase pulse to the portion of or the entire of the flash memory on the basis of the single program and erase entity.
7. The method of claim 1 , wherein erasing the flash device on the basis of the single program and erase entity comprises:
applying a erase gate voltage to a gate, applying a erase bitline voltage to a common bitline is shared by the two adjacent dual bit physical memory cells, and allowing at least one of non-common bitlines that are not shared by the two adjacent dual bit physical memory cells to float.
8. The method of claim 7 , wherein the erase gate voltage comprises a hot-hole-injection gate voltage and the erase bitline voltage comprises a hot-hole-injection bitline voltage.
9. The method of claim 1 , wherein the portion of or the entire of the flash device is erased on the basis of the single program and erase entity with the proviso that a sector erase is not performed in the portion of or the entire of the flash memory.
10. The method of claim 1 , wherein the portion of or the entire of the flash device is erased on the basis of the single program and erase entity with the proviso that an erase pulse is not sequentially applied to two or more consecutive bitlines in the portion of or the entire of the flash memory.
11. A method of operating a flash device comprising a plurality of dual bit memory cells, the memory cells comprising four or more data states, the method comprising;
mapping two adjacent physical memory cells as a single program and erase entity;
programming a portion of or an entire of the flash memory on a basis of the single program and erase entity by applying a program gate voltage to a gate, applying a program bitline voltage to a common bitline of the single program and erase entity that is shared by the two adjacent dual bit physical memory cells, and connecting at least one of two non-common bitlines of the single program and erase entity that are not shared by the two adjacent dual bit physical memory cells to ground; and
erasing the portion of or the entire of the flash memory on the basis of the single program and erase entity.
12. The method of claim 11 , wherein the program gate voltage comprises a hot-electron-injection gate voltage and the program bitline voltage comprises a hot-electron-injection bitline voltage.
13. The method of claim 11 , wherein erasing the portion of or the entire of the flash memory on the basis of the single program and erase entity comprises:
applying an erase pulse to the portion of or the entire of the flash memory on the basis of the single program and erase entity.
14. The method of claim 11 , wherein the erasing the portion of or the entire of the flash memory on the basis of the single program and erase entity comprises:
applying a erase gate voltage to a gate, applying a erase bitline voltage to a common bitline that is shared by the two adjacent dual bit physical memory cells, and allowing the non-common bitlines that are not shared by the two adjacent dual bit physical memory cells to float.
15. The method of claim 14 , wherein the erase gate voltage comprises a hot-hole-injection gate voltage and the erase bitline voltage comprises a hot-hole-injection bitline voltage.
16. A flash device comprising a plurality of dual bit memory cells, comprising;
a plurality of single program and erase entities comprising two adjacent dual bit physical memory cells, the bit memory cells comprising four or more data states; and
one or more decoders, that select at least one of the two adjacent dual bit physical memory cells for programming the flash device and select one or more single program and erase entities for erasing the flash device.
17. The flash device of claim 16 , wherein the four or more data states comprise one erased state and three or more programmed states.
18. The flash device of claim 16 , wherein the decoders comprises one or more bitline decoders that facilitate erasing a portion of or an entire of the flash device on the basis of the single program and erase entity with the proviso that a sector erase is not performed in the portion of or the entire of the flash memory.
19. The flash device of claim 16 , wherein the decoders comprises one or more bitline decoders that facilitate erasing a portion of or an entire of the flash device on the basis of the single program and erase entity with the proviso that an erase pulse is not sequentially applied to two or more consecutive bitlines in the portion of or the entire of the flash memory.
20. The flash device of claim 16 , wherein the single program and erase entity comprises sixteen or more data states.