Technique for doping from a polysilicon transfer layer
US4569701A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 5, 1984 |
| Grant date | Feb 11, 1986 |
| Priority date | — |
| Expiry date | Apr 5, 2004 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S148/035
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
For trench isolation technology or trench capacitor type memory cells, it is necessary to controllably dope the steep sidewalls of the trench. Implantation is ineffective and chemical doping sacrifices control. A thin transfer layer of polysilicon is deposited in the trench to conformally coat the sidewalls as well as the bottom of the trench and the top surface surrounding the trench. An impurity is implanted into the polysilicon at the bottom of the trench and around the top surface. Upon heating that impurity diffuses rapidly along the polysilicon layer inwardly and downwardly along the sidewalls. It then may be diffused into the substrate. The polysilicon layer may be etched away, or may be oxidized to SiO.sub.2 and etched away, or left in place.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.