Efficient reprogramming method for tightening a threshold voltage distribution in a memory device
US9165659B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | May 8, 2014 |
| Grant date | Oct 20, 2015 |
| Priority date | — |
| Expiry date | May 18, 2034 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C16/0483
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Techniques are provided for programming memory cells while reducing the effects of detrapping which cause a downshift in the threshold voltage distribution. Detrapping is particularly problematic for charge-trapping memory cells such as in a 3D stacked non-volatile memory device. During programming, a temporary lockout mode is provided for memory cells which pass a verify test. During a checkpoint program-verify iteration, all memory cells of a target data state are subject to the verify test. The memory cells in the temporary lockout mode are therefore subject to the verify test a second time. Memory cells that fail the verify test in the checkpoint program-verify iteration are programmed further. A normal or slow programming mode is used for a memory cell depending on whether it had reached the temporary lockout mode. Threshold voltage distributions are narrowed by reprogramming some of the memory cells.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.