Flexural plate wave sensor and array
AssigneeThe Charles Stark Draper Laboratory, Inc.
InventorBrian T. Cunningham
Life of this patent
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Abstract
A method for manufacturing a flexural plate wave sensor includes the steps of depositing an etch-stop layer over a substrate, depositing a membrane layer over the etch stop layer, depositing a piezoelectric layer over the membrane layer, forming a first transducer on the piezoelectric layer and forming a second transducer on the piezoelectric layer, spaced from the first transducer. The method further includes the steps of etching a cavity through the substrate, the cavity having substantially parallel interior walls, removing the portion of the etch stop layer between the cavity and the membrane layer to expose a portion of the membrane layer, and depositing an absorptive coating on the exposed portion of the membrane layer.
Claims18
A method for manufacturing a flexural plate wave sensor comprising the steps of:
- depositing a sacrificial material layer over a silicon substrate;
- depositing a membrane layer over the sacrificial material layer with said membrane layer covering said sacrificial material layer and contacting said silicon substrate;
- depositing a piezoelectric layer over said membrane layer;
- forming a first transducer on said piezoelectric layer;
- forming a second transducer on said piezoelectric layer, spaced from said first transducer;
- removing said sacrificial material layer to expose a portion of said membrane layer;
- and
- depositing an absorptive costing on said exposed portion of said membrane layer.
A flexural plate wave sensor comprising:
- a substrate;
- a membrane layer disposed on said substrate, said membrane layer having legs in contact with said substrate and a body portion spanning between said legs, wherein said substrate, a lower surface of said body portion and interior surfaces of said legs define a cavity between said substrate and said body portion;
- an absorptive coating disposed on the lower surface of said body portion of said membrane layer;
- a piezoelectric layer disposed over an upper surface of said membrane layer;
- a first transducer disposed on said piezoelectric layer, and a second transducer disposed on said piezoelectric layer, spaced from said first transducer.
A method for manufacturing a flexural plate wave sensor comprising the steps of:
- depositing a membrane layer on a substrate having a concave upper surface, thereby forming a cavity between an exposed portion of the membrane layer and the substrate;
- depositing a piezoelectric layer on the membrane layer;
- forming a first transducer on said piezoelectric layer;
- forming a second transducer on said piezoelectric layer, spaced from said first transducer;
- and
- depositing an absorptive coating on the exposed portion of said membrane layer within said cavity.
A flexural plate wave sensor comprising:
- a substrate having a recess disposed in an upper surface thereof;
- a membrane layer disposed on the upper surface of said substrate;
- a cavity disposed between a portion of said membrane layer and said recess in said substrate;
- a piezoelectric layer disposed on said membrane layer;
- a first transducer disposed on said piezoelectric layer;
- a second transducer disposed on said piezoelectric layer, spaced from said first transducer;
- and
- an absorptive coating disposed on said portion of said membrane layer within said cavity.
A flexural plate wave sensor array comprising:
- a substrate;
- a plurality of flexural plate wave sensors, each sensor including a cavity formed in the substrate, a thin film membrane layer spanning the cavity, a piezoelectric layer disposed on the thin film membrane layer, a transducer disposed on the piezoelectric layer and an absorbtive coating disposed on said thin film membrane layer within said cavity;
- a reference flexural plate wave sensor including a cavity formed in the substrate, a thin film membrane layer spanning the cavity, a piezoelectric layer disposed on the thin film membrane layer and a transducer disposed on the piezoelectric layer;
- and
- a microprocessor electrically connected to each of the plurality of flexural plate wave sensors and said reference flexural plate wave sensor, for monitoring resonant frequency characteristics of the sensors.
A flexural plate wave sensor array comprising:
- a substrate;
- a plurality of flexural plate wave sensors, each sensor including a cavity formed in the substrate, a thin film membrane layer spanning the cavity, a piezoelectric layer disposed on the thin film membrane layer, a transducer disposed on the piezoelectric layer and an absorptive coating disposed on said thin film membrane layer within said cavity;
- a drive amplifier which receives a drive input and outputs an amplified drive output;
- a multiplexer which receives said amplified drive output and a selection signal, for driving one of said plurality of flexural plate wave sensors;
- and
- an output amplifier which senses an output from said one of said plurality of flexural plate sensors and outputs an amplified sensed signal.
Dependencies are inferred from the claim text.