Integrated thin-film diaphragm; backside etch
US4784721A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 22, 1988 |
| Grant date | Nov 15, 1988 |
| Priority date | — |
| Expiry date | Feb 22, 2008 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10T29/49103
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A microbridge air flow sensor having a silicon nitride diaphragm formed on the surface of a single crystal silicon wafer. A rectangular 500 angstrom thick sacrificial layer was deposited on the silicon surface before the silicon nitride to define the exact position of the diaphragm. A series of etches from the backside of the wafer is performed to fabricate the device. A first silicon anisotropic etch from the backside is stopped at the sacrificial layer. A sacrificial layer selective etch is applied from the backside first pit to the sacrificial layer to remove all of the rectangular sacrificial layer. Anisotropic etch is again applied into the space created by the removed sacrificial layer whereby the second etch attacks the silicon exposed by the removal of the sacrificial layer and etches downward forming a second anisotropic etch pit. Thus all the etches are from the backside of the silicon wafer.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.