Method for accessing a multilevel nonvolatile memory device of the flash NAND type
US7382660B2 · kind B2 · utility
Assignees
Inventors
Key dates
| Filing date | Jul 20, 2006 |
| Grant date | Jun 3, 2008 |
| Priority date | — |
| Expiry date | Jul 27, 2026 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C2211/5641
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Multi-level programming allows for writing a first and a second bit in selected cells by separately programming the first bit from the second bit. Programming of the first bit determines a shifting from a first threshold level to a second threshold level. Programming of the second bit requires a preliminary reading to detect whether the first bit has been modified, performing a first writing step to bring the cell to a third threshold voltage if the first bit has been modified and performing a second writing step to bring the selected cell to a fourth threshold voltage different from the third threshold level if the first bit has not been modified. For increasing reading and program reliability, during preliminary reading of the second portion a reading result is forced to correspond to the first threshold level.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.