Piezoelectric MEMS microphone
AssigneeThe Regents of the University of Michigan
InventorsKarl Grosh, Robert J. Littrell
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Abstract
A piezoelectric MEMS microphone comprising a multi-layer sensor that includes at least one piezoelectric layer between two electrode layers, with the sensor being dimensioned such that it provides a near maximized ratio of output energy to sensor area, as determined by an optimization parameter that accounts for input pressure, bandwidth, and characteristics of the piezoelectric and electrode materials. The sensor can be formed from single or stacked cantilevered beams separated from each other by a small gap, or can be a stress-relieved diaphragm that is formed by deposition onto a silicon substrate, with the diaphragm then being stress relieved by substantial detachment of the diaphragm from the substrate, and then followed by reattachment of the now stress relieved diaphragm.
Claims6
A piezoelectric MEMS microphone, comprising:
- a substrate;
- and
- a multi-layer acoustic sensor comprising at least three layers including a first electrode layer, an intermediate layer of piezoelectric material deposited over said first electrode layer, and a second electrode layer deposited over said piezoelectric material;
- wherein said sensor is dimensioned such that an optimization parameter calculated according to the equation
- Optimization
-
-
- Parameter
- =
- V
- out
- 2
-
- C
- P
- 2
-
- A
-
-
- tan
-
- (
- δ
- )
- ·
- f
- res
- 2
- is at least 10% of the maximum obtainable optimization parameter for the sensor, where Vout is output voltage of the sensor, C is the capacitance of the sensor, P is the input pressure, A is the sensor area, tan(δ) is dielectric loss angle of the sensor at the sensor's first resonant frequency, and fres is the first resonant frequency;
- wherein said sensor comprises a plurality of beams each supported at one end by said substrate such that each beam is cantilevered and extends between a fixed end and a free end, each beam comprising said electrode and intermediate layers;
- and
- wherein at least two of said beams are positioned such that free ends of each beam face one another and are separated by a gap of no greater than 3 μm.
A piezoelectric MEMS microphone, comprising:
- a substrate;
- and
- a multi-layer acoustic sensor comprising at least three layers including a first electrode layer, an intermediate layer of piezoelectric material deposited over said first electrode layer, and a second electrode layer deposited over said piezoelectric material;
- wherein said sensor is dimensioned such that an optimization parameter calculated according to the equation
- Optimization
-
-
- Parameter
- =
- V
- out
- 2
-
- C
- P
- 2
-
- A
-
-
- tan
-
- (
- δ
- )
- ·
- f
- res
- 2
- is at least 10% of the maximum obtainable optimization parameter for the sensor, where Vout is output voltage of the sensor, C is the capacitance of the sensor, P is the input pressure, A is the sensor area, tan(δ) is dielectric loss angle of the sensor at the sensor's first resonant frequency, and fres is the first resonant frequency;
- wherein said sensor comprises a plurality of beams each supported at one end by said substrate such that each beam is cantilevered and extends between a fixed end and a free end, each beam comprising said electrode and intermediate layers;
- and
- wherein adjacent beams are separated by a gap that is no greater than 10 μm.
A piezoelectric MEMS microphone, comprising:
- a substrate;
- and a multilayer acoustic sensor comprising a plurality of cantilevered beams, each beam comprising a first electrode layer, an intermediate layer of piezoelectric material deposited over said first electrode layer, and a second electrode layer deposited over said piezoelectric material, wherein each beam is supported at a fixed end by said substrate and extends between said fixed end and a free end, and at least two of said free ends are separated by a gap and face one another across said gap, wherein adjacent beams are separated by a gap that is no greater than 10 microns.
Dependencies are inferred from the claim text.