Pre-program detection of threshold voltages of select gate transistors in a memory device
US9418751B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 24, 2015 |
| Grant date | Aug 16, 2016 |
| Priority date | — |
| Expiry date | Jul 24, 2035 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C11/34
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A memory device includes memory cells arranged in NAND strings between select gate transistors. A threshold voltage (Vth) distribution of the select gate transistors is evaluated, such as in response to a program, erase or read command involving a block or sub-block of memory cells. For example, a lower tail and an upper tail of the Vth distribution can be evaluated using read voltages. If the Vth is out-of-range, such as due to read disturb, data retention loss or defects in the memory device, the block or sub-block is marked as being bad and previously-programmed data in the block or sub-block can be copied to another location. If the Vth is in range, the command can be executed. Also, a control gate voltage for the select gate transistors can be set based on a Vth metric which is obtained from the evaluation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.