Micromachined thermal mass flow sensor with self-cleaning capability and methods of making the same
US7878056B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Dec 19, 2007 |
| Grant date | Feb 1, 2011 |
| Priority date | — |
| Expiry date | Dec 19, 2027 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01F15/006
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
The current invention generally relates to Micro Electro Mechanical Systems (MEMS) thermal mass flow sensors for measuring the flow rate of a flowing fluid (gas/liquid) and the methods of manufacturing on single crystal silicon wafers. The said mass flow sensors have self-cleaning capability that is achieved via the modulation of the cavity of which the sensing elements locate on the top of the cavity that is made of a silicon nitride film; alternatively the sensing elements are fabricated on top of a binary silicon nitride/conductive polycrystalline silicon film under which is a porous silicon layer selective formed in a silicon substrate. Using polycrystalline silicon or the sensing elements as electrodes, an acoustic wave can be generated across the porous silicon layer which is also used for the thermal isolation of the sensing elements. The vibration or acoustic energy is effective to remove foreign materials deposited on top surface of the sensing elements that ensure the accuracy and enhance repeatability of the thermal mass flow sensing.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.