Capacitive surface micromachined differential pressure sensor
AssigneeFord Motor Company
InventorCarlos H. Mastrangelo
Life of this patent
Estimating the term…
Abstract
A surface layer and a sacrificial layer are deposited on a substrate. A conductive structural layer bridges over the sacrificial layer and is anchored to the surface layer for creating paired conductive areas. A backside opening is etched in the substrate for defining a flexible diaphragm layer of reduced thickness. The sacrificial layer is removed so that pressures exerted on the backside opening will cause a change in capacitance between the paired conductive areas. Temporary posts support the conductive structural layer as the sacrificial layer is removed.
Claims18
A method for fabricating a micromachined capacitive differential pressure sensor on a substrate, comprising the steps of:
- selectively implanting a doping material into the substrate so as to define a first etch-stop layer,
- depositing a surface layer of semiconductor material over the substrate so as to at least cover said first etch-stop layer for defining a diaphragm thereon,
- depositing a passivating conductive layer over said diaphragm to form a diaphragm electrode,
- selectively depositing a sacrificial layer over said diaphragm and said passivating conductive layer thereon,
- anchoring a conductive structural layer to said surface layer such that said sacrificial layer is located between the substrate and said structural layer so as to form a second electrode,
- selectively etching said substrate from the side opposite said structural layer so as to form an open backside aperture that terminates at said first etch-stop layer,
- selectively removing said first etch-stop layer such that such backside aperture couples to said diaphragm on the side opposite said structural layer,
- forming at least one temporary post extending through said structural layer toward said surface layer for reducing the deflection therebetween,
- removing said sacrificial layer so as to form a diaphragm cavity into which said diaphragm may deflect in response to the pressure to be measured, and
- removing said temporary posts,
- whereby pressure exerted through said backside aperture causes a deflection of said diaphragm and a corresponding change of the capacitance between said first and second electrodes.
A surface micromachined differential pressure sensor comprising:
- a substrate,
- a surface layer on one side of said substrate,
- a pair of first conductive areas laterally adjacent to each other in said surface layer,
- a pair Of bridging conductive layers, each coupled to said substrate and bridging over its corresponding one of said first conductive areas so as to form a capacitor therewith and a diaphragm cavity therebetween,
- a backside aperture opening from the side of said substrate opposite from said one side and communicating into said substrate so as to define a flexible diaphragm layer of reduced thickness juxtaposed with said first conductive area,
- whereby pressure exerted through said backside aperture results in a displacement of said flexible diaphragm causing a variation only in the capacitance between said bridging conductive layer and said first conductive area juxtaposed with said backside aperture.
Dependencies are inferred from the claim text.