Low temperature oxide layer over field implant mask
US5328866A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 21, 1992 |
| Grant date | Jul 12, 1994 |
| Priority date | — |
| Expiry date | Sep 21, 2012 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D84/0109
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
A thin base oxide is disposed over both an active area and also over a field area of a substrate. A thin silicon-nitride layer is then formed over the base oxide in the active area to protect the underlying substrate from oxygen and/or water vapor during a subsequent field oxidation step. This thin nitride layer is, however, insufficiently thick to serve as a field implant mask in a subsequent field implant step. An additional low temperature oxide (LTO) layer is therefore provided over the nitride layer in the active area. The field implant step is then performed using the base oxide, the thin nitride, and the overlying LTO as a field implant mask. The boundaries of the overlying LTO define a field implant boundary. After the field implant step but before the field oxidation step, the LTO layer is removed from the top of the thin nitride layer. As a result, only the base oxide and the thin nitride layer is disposed over the active area during field oxidation. Therefore, in comparison to previous methods using thicker nitride layers, the present invention employs a thin nitride layer during the field oxidation step, thereby reducing the amount of stress induced in the nitride layer…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.