Method for fabricating an SOI substrate
US5866468A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 14, 1996 |
| Grant date | Feb 2, 1999 |
| Priority date | — |
| Expiry date | Aug 14, 2016 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH10D62/314
- WIPO fieldSemiconductors
- WIPO sectorElectrical engineering
Abstract
In the wafer-bonding method of fabricating an SOI (silicon-on-insulator) substrate, even if there exists thickness variation in the silicon layer, devices fabricated onto the silicon layer, in accordance with the present invention, have a decreased threshold voltage variation. According to the present invention, after bonding two wafers, the thickness of the thinned silicon layer atop the SOI substrate is measured to precisely determine the local thickness distribution. However, the fabricated devices' threshold voltage depends upon the doping concentration as well as the thickness of the silicon layer. Shielding masks of photoresist are thereafter formed selectively on a portion of the silicon that are thicker. Then, through the masks as shielding, impurities are implanted into the silicon layer to adjust the doping concentration therein. Accordingly, the doping concentration is varied corresponding to the thickness, with the result that the threshold voltage variation nearly approaches zero.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.