Piezoelectric accelerometer with wake function
A sensor device that senses proper acceleration. The sensor device includes a substrate, a spacer layer supported over a first surface of the substrate, at least a first cantilever beam element having a base and a tip, the base attached to the spacer layer, and which is supported over and spaced from the substrate by the spacer layer. The at least first cantilever beam element further including at least a first layer comprised of a piezoelectric material, a pair of electrically conductive layers disposed on opposing surfaces of the first layer, and a mass supported at the tip portion of the at least first cantilever beam element.
1 . A sensor device, comprising:
a substrate;
a spacer layer supported over a first surface of the substrate;
a first cantilever beam element having a base and a tip, the base attached to the spacer layer, and which the first cantilever beam element is supported over and spaced from the substrate by the spacer layer, with the first cantilever beam element having a substantially constant width from a base portion to a tip portion, and with the first cantilever beam element further comprising:
a first layer comprised of a piezoelectric material;
a pair of electrically conductive layers disposed on opposing surfaces of the first layer; and
a mass element supported at the tip portion of the first cantilever beam element, wherein the mass element is supported on an electrically inactive portion of the first cantilever beam element.
2 . The sensor device of claim 1 wherein the piezoelectric material is aluminum nitride or lead zirconate titanate or scandium-doped aluminum nitride.
3 . The sensor device of claim 1 wherein the substrate comprises a silicon, the spacer layer comprises a silicon dioxide and the pair of electrically conductive layers are comprised of a refractory metal.
4 . The sensor device of claim 1 wherein the first layer of the piezoelectric material and the pair of electrically conductive layers comprise a plurality of layers of piezoelectric material and a plurality of electrically conductive layers disposed on opposing surfaces of the plurality of layers of piezoelectric material.
5 . The sensor device of claim 1 wherein the first cantilever beam element is configured to have an electrical discontinuity in the pair of electrically conductive layers to provide an electrically active portion of the first cantilever beam element and the electrically inactive portion of the first cantilever beam element.
6 . The sensor device of claim 1 further comprising:
a plurality of cantilever beam elements that includes the first cantilever beam element, wherein a respective cantilever beam element includes a respective mass element supported at a respective tip portion, and wherein the respective mass element is supported on an electrically inactive portion of the respective cantilever beam element.
7 . The sensor device of claim 1 wherein the first cantilever beam element is a plurality of cantilever beam elements arranged in a close-packed area by interdigitating the plurality of cantilever beam elements.
8 . The sensor device of claim 7 wherein each of the plurality of cantilever beam elements has an electrical discontinuity in at least one of the pair of electrically conductive layers to provide an electrically active portion and an electrically inactive portion.
9 . The sensor device of claim 8 wherein each of the plurality of cantilever beam elements has a mass element, with the mass element supported on the electrically inactive portion of the first cantilever beam element.
10 . The sensor device of claim 1 wherein the sensor device further comprises:
plural cantilever beam elements that includes the first cantilever beam element; and
a single mass supported on the electrically inactive portion of the plural cantilever beam elements.
11 . The sensor device of claim 1 , further comprises:
a plurality of cantilever beam elements including the first cantilever beam element, with the plurality of cantilever beam elements arranged in a close-packed area, and with each of the plurality of cantilever beam elements comprising the piezoelectric material, the pair of electrically conductive layers, and a respective mass element supported at the tip portion of each of the plurality of cantilever beam elements.
12 . The sensor device of claim 7 wherein the plurality of cantilever beam elements are electrically connected in series with each.
13 . A sensor device, comprising:
a substrate;
a spacer layer supported over a first surface of the substrate;
a plurality of cantilever beam elements arranged in a close-packed area by interdigitating the plurality of cantilever beam elements, a first cantilever beam element of the plurality of cantilever beam elements having a base and a tip, the base attached to the spacer layer, and which the first cantilever beam element is supported over and spaced from the substrate by the spacer layer, with the first cantilever beam element having a substantially constant width from a base portion to a tip portion, and with the first cantilever beam element further comprising:
a first layer comprised of a piezoelectric material; and
a pair of electrically conductive layers disposed on opposing surfaces of the first layer, wherein each of the plurality of cantilever beam elements has an electrical discontinuity in at least one of the pair of electrically conductive layers to provide an electrically active portion and an electrically inactive portion.
14 . A packaged micro electromechanical system (MEMS) device comprising:
a MEMS device including a package having a compartment; and
a MEMS die disposed in the compartment, the MEMS die supporting a MEMS accelerometer and a MEMS microphone, wherein the MEMS accelerometer includes a sensor device configured to produce an output signal,
wherein the sensor device comprises:
a substrate;
a spacer layer supported over a first surface of the substrate;
a first cantilever beam element having a base and a tip, the base attached to the spacer layer, and wherein the first cantilever beam element is supported over and spaced from the substrate by the spacer layer, with the first cantilever beam element having a substantially constant width from a base portion to a tip portion, and with the first cantilever beam element further comprising:
a first layer comprised of a piezoelectric material;
a pair of electrically conductive layers disposed on opposing surfaces of the first layer; and
a mass element supported at the tip portion of the first cantilever beam element, wherein the mass element is supported on an electrically inactive portion of the first cantilever beam element.