Non-uniform threshold voltage adjustment in flash eproms through gate work function alteration
US5888867A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 13, 1998 |
| Grant date | Mar 30, 1999 |
| Priority date | — |
| Expiry date | Feb 13, 2018 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D64/667
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
Aspects for forming a Flash EPROM cell with an adjustable threshold voltage are described. In a method aspect, the method includes forming a substrate structure to establish a foundation for cell formation, and forming a gate structure with a floating gate layer comprising polysilicon-germanium (poly-SiGe) of a non-uniform Ge concentration on the substrate structure. The method further includes forming source and drain regions within the substrate structure, the drain region having a different threshold voltage than the source region. In a further aspect, a Flash EPROM cell with an adjustable threshold voltage includes a substrate structure as a foundation for the cell. The cell further includes a gate structure on the substrate structure, the gate structure comprising a floating gate layer of polysilicon-germanium (poly-SiGe) of non-uniform Ge concentration. Additionally, source and drain regions are included in the substrate structure bordering the gate structure, the drain region having a differing threshold voltage than the source region.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.