Flash-to-ROM conversion
US8999785B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Sep 27, 2011 |
| Grant date | Apr 7, 2015 |
| Priority date | — |
| Expiry date | Jun 10, 2033 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D64/035
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Flash-to-ROM conversion is performed by converting single transistor flash memory cells to single transistor ROM cells. An S-Flash memory cell is converted to a programmed ROM cell by introducing a threshold voltage implant into the channel region of the S-Flash memory cell. Alternately, an S-Flash memory cell is converted to a programmed ROM cell by introducing a threshold voltage implant into a substrate region in alignment with an edge of the gate electrode of the S-Flash memory cell. The width of the mask through which this threshold voltage implant is performed can be varied, such that the threshold voltage implant region can have different dopant concentrations, thereby allowing multiple bits to be represented by the programmed ROM cell. In another embodiment, a Y-flash memory cell is converted to a programmed ROM cell by adjusting the length of a floating gate extension region of the Y-Flash memory cell.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.