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| Voltage tunable schottky diode photoemissive infrared detector |
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| Lighting device |
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Ultrasonic image sensing array with acoustical backing
| Details |
Inventors: Carson, Paul L.; Fitting, Dale W.; Robinson, Andrew L.; Terry, Jr., Fred L.;
Assignee:
Primary Examiner: Budd; Mark O.
Assistant Examiner:
Attorney, Agent or Firm: Harness, Dickey & Pierce
An ultrasonic sensing array having ultrasonic transducer elements formed on a micromachined single-crystal semiconductor wafer provided with a deep recess under each transducer. Etch-altering dopants are diffused into the wafer to form rimmed support structures for dielectric stress-balanced elements. Composite dielectric layers are grown on both surfaces of the wafer. One composite layer serves as a diaphragm underlying the transducer elements. The other composite layer serves as a mask for etching away the substrate under each transducer element to form the deep recess while leaving the support structures and diaphragm layer. The resulting hollow or recess under each transducer element reduces the parasitic capacitance between the transducer and support substrate. The transducer elements are made by forming conductive bottom plates on the dielectric diaphragm layer, adding a piezoelectric polymer layer and thereafter forming the conductive top plates. The resulting ultrasonic sensors are capable of operation over a wide variety of frequencies with improved sensitivity and decreased acoustic crosstalk between sensor elements, Switching transistors may also be fabricated as part of the patterned semiconductor substrate. |
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DETAILED DESCRIPTION In order to achieve most if not all of the foregoing objects, there is provided in accordance with a first aspect of the present invention, an ultrasonic sensing array having a plurality of piezoelectric transducers, each of which is responsive to ultrasonic forces applied thereto.
The ultrasonic sensor array comprises: a micromachined support substrate; a diaphragm layer formed on one side of the substrate; and the plurality of piezoelectric transducers, which are preferably patterned so as to be separated acoustically in at least one lateral dimension from one another.
The plurality of transducers includes: a first plurality of electrically conductive plates laterally spaced from one another on a side of the diaphragm layer opposite the substrate, with each such plate being associated with a distinct one of the transducers; at least one layer of piezoelectric material bonded to the first plurality of electrically conductive plates; and a second plurality of electrically conductive plates laterally spaced from one another and bonded to a side of the piezoelectric material opposite the first plurality of electrically conductive plates.
Each such plate of the second plurality of plates may be associated with a distinct one of the transducers and a distinct one of the first plurality of electrically conductive plates.
Note that, if desired, the second plate may be substantially continuous, so that it forms a common electrode.
Similarly, the piezoelectric material may be substantially continuous.
The micromachined support substrate is preferably made of single-crystal semiconductor material, such as silicon semiconductor material.
One preferred support substrate features a stress-balanced (or stress-free) dielectric diaphragm layer upon which ultrasonic piezoelectric transducers are formed.
Micromachining, including wet and dry etches, is used to remove those portions of the single-crystal substrate which are under the transducer elements.
This significantly reduces the large parasitic capacitance which would otherwise be present if such transducer elements were supported with continuous conductive substrate
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MEMS 
