Method for erasing flash electrically erasable programmable read-only memory (EEPROM)
US5901090A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 27, 1998 |
| Grant date | May 4, 1999 |
| Priority date | — |
| Expiry date | May 27, 2018 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C16/16
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A flash Electrically-Erasable Programmable Read-Only Memory (EEPROM) includes a plurality of field effect transistor memory cells each having a source, drain, floating gate and control gate, and a power source for supplying a plurality of voltages to the cells. A controller controls the power source to apply at least one erase pulse to the cells. Then, at least one overerase correction or "soft programming" pulse is applied to the cells during which the source, drain and control gate voltages of the cells are such that the threshold voltages of overerased cells will be increased, but least erased cells will not be disturbed. The overerase correction pulses thereby tighten the threshold voltage distribution. A source to substrate bias voltage is applied for the duration of the overerase correction pulses which reduces the background leakage of the cells to a level at which the overerase correction operation can be effectively performed, even in applications with low supply voltages.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.