Capacitive surface micromachined differential pressure sensor
First Claim
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1. 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, andremoving 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.
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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.
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Citations
18 Claims
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1. A method for fabricating a micromachined capacitive differential pressure sensor on a substrate, comprising the steps of:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A surface micromachined differential pressure sensor comprising:
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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. - View Dependent Claims (15, 16, 17, 18)
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Specification