Dual floating gate EEPROM cell array with steering gates shared by adjacent cells
US6151248A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 30, 1999 |
| Grant date | Nov 21, 2000 |
| Priority date | — |
| Expiry date | Jun 30, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG11C2211/5612
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
An EEPROM system having an array of memory cells that individually include two floating gates, bit line source and drain diffusions extending along columns, steering gates also extending along columns and select gates forming word lines along rows of floating gates. The dual gate cell increases the density of data that can be stored. Rather than providing a separate steering gate for each column of floating gates, an individual steering gate is shared by two adjacent columns of floating gates that have a diffusion between them. The steering gate is thus shared by two floating gates of different but adjacent memory cells. In one array embodiment, the floating gates are formed on the surface of the substrate, where the added width of the steering gates makes them easier to form, removes them as a limitation upon scaling the array smaller, require fewer electrical contacts along their length because of increased conductance, are easier to contact, and reduces the number of conductive traces that are needed to connect with them. In arrays that erase the floating gates to the select gates, rather than to the substrate, the wider steering gates advantageously uncouple the diffusions they…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.