Patent Description:
The present disclosure relates to micro electromechanical systems (MEMS). More specifically, the present disclosure relates to MEMS with cantilevered structures.

MEMS cantilevers are devices constrained on one side and incorporate piezoelectric materials that can be used as sensors and actuators. Such devices can be tuned to a specific resonant frequency by using a specific mass attached to the cantilever. MEMS cantilevers can unintendedly sense secondary frequency modes that cause the cantilever to move in a twisting or rocking motion instead of the main vertical motion. Such movements in response to a secondary frequency mode are termed "parasitic sensing. " Parasitic sensing can interfere with the operation of MEMS devices and cause cantilever breakage. Cantilevers tuned to lower vibration frequencies require higher proof masses and are more prone to breakage. <CIT> describes an acoustic sensor with four disc-quadrant shaped suspended sections which work as cantilevers over a space and are all joined in the centre of the disc area by a constraint structure. The cantilever parts and the constraint structure are formed by cut-outs made in a piezoelectric diaphragm. <CIT> teaches a MEMS device
with piezoelectric bending actuators that set an adjustable part into oscillating motion.

A MEMS device is provided as defined by independent claim <NUM>.

A MEMS vibrometer is provided as defined by dependent claim <NUM>.

<FIG> is a perspective view of prior art MEMS cantilever <NUM> oriented in x-y-z coordinates. MEMS cantilever <NUM> includes support structure <NUM>, cantilever <NUM> with top layer <NUM> and bottom layer <NUM>, and proof mass <NUM>.

Support structure <NUM> is electrically and mechanically connected to one end of cantilever <NUM>. Top layer <NUM> of cantilever <NUM> is made of a piezoelectric material such as aluminum nitride or lead zirconate titanate (PZT). Bottom layer <NUM> of cantilever <NUM> is made of substrate material, such as silicon. At the opposite end of cantilever <NUM> from support structure <NUM>, bottom layer <NUM> of cantilever <NUM> connects to proof mass <NUM>. Support structure <NUM> lies substantially within the y-z plane, and cantilever <NUM> lies substantially within the x-y plane.

MEMS cantilever <NUM> senses vibrations by measuring the built-up electric charge in the piezoelectric material of top layer <NUM> of cantilever <NUM> in response to vibrational movement. Proof mass <NUM> can have different masses to tune MEMS cantilever <NUM> to sense a specific vibrational resonant frequency. Alternatively or additionally, the resonant frequency of MEMS cantilever <NUM> can be tuned depending upon the stiffness of bottom layer <NUM> which is thicker and stiffer than top layer <NUM>. Upon MEMS cantilever <NUM> sensing vibrational force in the z-direction at the specific resonant frequency, cantilever <NUM> will distort both ways along the z-axis. The mechanical movement of cantilever <NUM> will cause electric charge to build up in the piezoelectric material of top layer <NUM> of cantilever <NUM>. Charge will be conducted along top layer <NUM>.

MEMS cantilever <NUM> also responds to secondary resonance frequency modes. Such vibrations can cause parasitic sensing in cantilever <NUM>. Forces in the y-direction will cause twisting motions in cantilever <NUM>. Forces in the x-direction will induce a rotation moment of proof mass <NUM> and will cause rocking oscillation in the z-direction. This rocking oscillation will be similar to the main mode but in response to a different resonant frequency. These secondary resonant frequencies can be very close to the main frequency mode and interfere with the operation of the device. Excessive movements in the x-direction, y-direction, and z-direction can cause cantilever breakage.

<FIG> is a top view of MEMS vibrometer <NUM>. <FIG> is a cross-sectional view of MEMS vibrometer <NUM> taken along line <NUM>-<NUM> of <FIG> and <FIG> will be discussed together. MEMS vibrometer <NUM> includes MEMS device <NUM> and support frame <NUM>. MEMS device <NUM> includes top layer <NUM>, bottom layer <NUM>, electronic trace <NUM>, first mooring portion <NUM>, second mooring portion <NUM>, MEMS device body <NUM>, first margin <NUM>, first slot <NUM>, second margin <NUM>, and second slot <NUM>. Support frame <NUM> includes first sidewall <NUM>, second sidewall <NUM>, third sidewall <NUM>, fourth sidewall <NUM>, bonding material <NUM> with height H, support wafer <NUM>, and cavity <NUM>. Support frame <NUM> further includes first attachment site <NUM>, second attachment site <NUM>, third attachment site <NUM>, and fourth attachment site <NUM>. <FIG> also show first electrode <NUM>, second electrode <NUM>, first connecting wire 77A, and second connecting wire 77B. <FIG> also shows gap space GS.

MEMS device <NUM> and support frame <NUM> are attached to form MEMS vibrometer <NUM>. MEMS device <NUM> is manufactured as a single piece that includes top layer <NUM> and bottom layer <NUM>. Top layer <NUM> is a first layer made of a piezoelectric material like aluminum nitride or PZT. Bottom layer <NUM> is a second layer that made of a substrate material, like surface-doped silicon. Surface-doped silicon allows bottom layer <NUM> to conduct the charge developed in piezoelectric top layer <NUM>. Dopants include, but are not limited to, phosphorous or boron. Bottom layer <NUM> is stiffer and thicker than top layer <NUM>. Between top layer <NUM> and bottom layer <NUM> is electronic trace <NUM>. MEMS device <NUM> also includes first mooring portion <NUM> across from second mooring portion <NUM>. Electronic trace <NUM> is located between top layer <NUM> and bottom layer <NUM> and extends past first mooring portion <NUM> and second mooring portion <NUM>. MEMS device body <NUM> attaches on either side to first mooring portion <NUM> and second mooring portion <NUM>. First margin <NUM> runs alongside MEMS device body <NUM> and attaches to first mooring portion <NUM> and second mooring portion <NUM>. First slot <NUM> is positioned between device body <NUM> and first margin <NUM>. First slot <NUM> extends through top layer <NUM> and bottom layer <NUM>. Second margin <NUM> runs alongside MEMS device body <NUM> opposite first margin <NUM> and attaches to first mooring portion <NUM> and second mooring portion <NUM>. Second slot <NUM> is positioned between MEMS device body <NUM> and second margin <NUM>. Second slot <NUM> extends through top layer <NUM> and bottom layer <NUM> of MEMS device <NUM>.

Support frame <NUM> is configured so first sidewall <NUM> is across from second sidewall <NUM>. Third sidewall <NUM> attaches to first sidewall <NUM> and second sidewall <NUM>. Fourth sidewall <NUM> is across from third sidewall <NUM> and attaches to first sidewall <NUM> and second sidewall <NUM>. Bonding material <NUM> extends along a bottom of first sidewall <NUM>, a bottom of second sidewall <NUM>, a bottom of third sidewall <NUM>, and a bottom of fourth sidewall <NUM>. Bonding material <NUM> connects first sidewall <NUM>, second sidewall <NUM>, third sidewall <NUM>, and fourth sidewall <NUM> to support wafer <NUM>. Cavity <NUM> is defined by MEMS device <NUM>, first sidewall <NUM>, second sidewall <NUM>, third sidewall <NUM>, fourth sidewall <NUM>, bonding material <NUM>, and support wafer <NUM>. First attachment site <NUM> is a top of first sidewall <NUM>. Second attachment site <NUM> is a top of second sidewall <NUM>. Third attachment site <NUM> is a top of third sidewall <NUM>. Fourth attachment site <NUM> is a top of fourth sidewall <NUM>. First attachment site <NUM>, second attachment site <NUM>, third attachment site <NUM>, and fourth attachment site <NUM> are configured to attach MEMS device <NUM> to support frame <NUM>.

MEMS device <NUM> mechanically connects to support frame <NUM> in four places. First mooring portion <NUM> of MEMS device <NUM> and electronic trace <NUM> attach to first attachment site <NUM> on first sidewall <NUM>. Second mooring portion <NUM> of MEMS device <NUM> and electronic trace <NUM> attach to second attachment site <NUM> on second sidewall <NUM>. First margin <NUM> attaches to third sidewall <NUM> at third attachment site <NUM>. Second margin <NUM> attaches to fourth attachment site <NUM> on fourth sidewall <NUM>. Attaching MEMS device <NUM> to support frame <NUM> creates cavity <NUM> within MEMS vibrometer <NUM>. Cavity <NUM> provides space for MEMS device <NUM> to vibrate when attached to support frame <NUM>. First electrode <NUM> attaches to MEMS device <NUM> at the piezoelectric material of top layer <NUM> at second mooring position <NUM>. First connecting wire 77A attaches to first electrode <NUM>. Second electrode <NUM> attaches to MEMS device <NUM> at electronic trace <NUM>. Second connecting wire 77B connects to second electrode <NUM>. Anchoring support frame <NUM> to support wafer <NUM> with bonding material <NUM> creates gap space GS between a bottom of MEMS device <NUM> and support wafer <NUM>. Gap space GS is equivalent to height H of bonding material <NUM>. Controlling height H of bonding material <NUM> limits the possible distance of travel for MEMS device <NUM> and reduces device breakage.

When MEMS vibrometer <NUM> experiences vibrational force, MEMS device <NUM> vibrates. Mechanical motions in MEMS device body <NUM> create electrical charge in the piezoelectric material of top layer <NUM>. A top side of the piezoelectric material of top layer <NUM> accumulates charge opposite in sign of charge accumulated in a bottom side of the piezoelectric material of top layer <NUM>. Charge accumulated on the top side of top layer <NUM> is captured by first electrode <NUM> attached at second mooring portion <NUM> and conducted along first connecting wire 77A. Charge accumulated on the bottom side of top layer <NUM> is conducted along bottom layer <NUM> to electronic trace <NUM>, captured by second electrode <NUM>, and conducted along second connecting wire 77B. First mooring portion <NUM>, second mooring portion <NUM>, first margin <NUM>, and second margin <NUM> attach MEMS device <NUM> mechanically to support frame <NUM>. First slot <NUM> and second slot <NUM> allow MEMS device body <NUM> to move freely when MEMS vibrometer <NUM> senses vibrations. Support frame <NUM> provides a robust structure for MEMS device <NUM> and allows MEMS vibrometer <NUM> to be mounted on many types of surfaces. Upon modification, MEMS vibrometer <NUM> could also be used as a different type of sensor or actuator device.

<FIG> is a top view of MEMS device <NUM> including first cantilever <NUM> and second cantilever <NUM> connected with pivot spring <NUM>. <FIG> is a cross-sectional view of MEMS device <NUM> taken along line <NUM>-<NUM> of <FIG> and <FIG> will be discussed together. MEMS device <NUM> has top layer <NUM>, bottom layer <NUM>, first mooring portion <NUM>, second mooring portion <NUM>, MEMS device body <NUM>, first margin <NUM>, first slot <NUM>, second margin <NUM>, and second slot <NUM>. MEMS device body <NUM> includes first cantilever <NUM>, pivot spring <NUM>, second cantilever <NUM>, circuitous cuts <NUM>, first proof mass <NUM>, and second proof mass <NUM>.

MEMS device <NUM> is manufactured as a single piece. Top layer <NUM> of MEMS device <NUM> is a first layer made of a piezoelectric material such as aluminum nitride or PZT. Bottom layer <NUM> of MEMS device <NUM> is a second layer made of a substrate material such as surface-doped silicon. Bottom layer <NUM> is stiffer and thicker than top layer <NUM>. MEMS device <NUM> has first mooring portion <NUM> oriented across from second mooring portion <NUM>. First margin <NUM> runs alongside MEMS device body <NUM> and attaches to first mooring portion <NUM> and second mooring portion <NUM> at either end. First slot <NUM> is between MEMS device body <NUM> and first margin <NUM>. First slot <NUM> extends through top layer <NUM> and bottom layer <NUM>. Second margin <NUM> is alongside MEMS device body <NUM> opposite first margin <NUM>. Second margin <NUM> attaches to first mooring portion <NUM> and second mooring portion <NUM> of MEMS device <NUM>. Second slot <NUM> is between MEMS device body <NUM> and second margin <NUM>. Second slot <NUM> extends through top layer <NUM> and bottom layer <NUM>. <FIG> shows MEMS device <NUM> is oriented so first margin <NUM> is generally parallel to the x-axis and first mooring portion <NUM> is generally parallel to the y-axis. <FIG> shows MEMS device <NUM> is generally perpendicular to the z-axis.

MEMS device body <NUM> connects with first mooring portion <NUM> and second mooring portion <NUM> on opposite sides. MEMS device body <NUM> includes first cantilever <NUM>, pivot spring <NUM>, and second cantilever <NUM>. First cantilever <NUM> connects to first mooring portion <NUM> of MEMS device <NUM> on one side and pivot spring <NUM> on the other. Pivot spring <NUM> has circuitous cuts <NUM> that extend through top layer <NUM> and bottom layer <NUM> of MEMS device <NUM>. Circuitous cuts <NUM> can have a variety of patterns, one of which is shown in <FIG>. Circuitous cuts <NUM> connect to first slot <NUM> and second slot <NUM>. Second cantilever <NUM> connects to pivot spring <NUM> on the opposite side of first cantilever <NUM>. Second cantilever <NUM> connects to second mooring portion <NUM> of MEMS device <NUM> opposite pivot spring <NUM>. Pivot spring <NUM> is in operable communication with first cantilever <NUM> and second cantilever <NUM>. First cantilever <NUM> and second cantilever <NUM> are electrically connected in parallel with the bottom layer <NUM> of first cantilever <NUM> and second cantilever <NUM> electrically connected and the top layer <NUM> of first cantilever <NUM> and second cantilever <NUM> electrically connected. First proof mass <NUM> attaches to a bottom of bottom layer <NUM> of first cantilever <NUM>. Second proof mass <NUM> attaches to a bottom of bottom layer <NUM> of second cantilever <NUM>. First proof mass <NUM> and second proofmass <NUM> need not be additional mass and can be equivalent to the masses of first cantilever <NUM> and second cantilever <NUM>, respectively.

MEMS device <NUM> is tuned to respond to a specific resonant frequency dependent on first proof mass <NUM> and second proof mass <NUM>. Bottom layer <NUM> can also tune the resonance frequency of MEMS device <NUM> depending on the stiffness of bottom layer <NUM>. Upon sensing the specific resonance frequency in the z-direction, MEMS device body <NUM> vibrates in the z-direction with first cantilever <NUM> and second cantilever <NUM> moving in phase due to the connection through pivot spring <NUM>. Mechanical movement of first cantilever <NUM> and second cantilever <NUM> cause electrical charge to build in the piezoelectric material of top layer <NUM> of MEMS device <NUM>. A top of top layer <NUM> collects signed electric charge and a bottom of top layer <NUM> collects charge of the opposite sign. First slot <NUM> and second slot <NUM> allow MEMS device body <NUM> to move independently of first margin <NUM> and second margin <NUM>. First margin <NUM> and second margin <NUM> can act as anchoring points for MEMS device <NUM>.

The in-phase movements of electrically connected first cantilever <NUM> and second cantilever <NUM> allow for same-sign electrical current transmission across MEMS device <NUM>. Symmetric, sign-specific movements of first cantilever <NUM> and second cantilever <NUM> allow for the charge created by top layer <NUM> of MEMS device <NUM> to be additive and increase the signal-to-noise ratio of MEMS device <NUM>. Pivot spring <NUM> cancels opposite-sign electrical buildup at an inflection point of MEMS device body <NUM>.

The connection of first cantilever <NUM> to second cantilever <NUM> with pivot spring <NUM> helps reduce parasitic sensing from vibrations other than the primary resonant frequency. First, out-of-phase oscillations of first cantilever <NUM> and second cantilever <NUM> in the z-direction will be reduced to negligibly small amplitudes and very high frequencies that are separate from the primary resonant frequency. The charge generated by such movements will be cancelled out and net sensing will be zero. Second, linking first cantilever <NUM> and second cantilever <NUM> with pivot spring <NUM> cancels parasitic signals created by rocking movements caused by force in the x-direction. The motion will be restricted by pivot spring <NUM> to negligible amplitudes and very high frequencies different than the primary resonant frequency. The charge generated by first cantilever <NUM> and second cantilever <NUM> will have opposite signs and the net result electric signal will be zero. Third, rotational movement caused by force in the y-direction is limited because pivot spring <NUM> will cause first cantilever <NUM> and second cantilever <NUM> to twist in phase. In-phase twisting motions will induce symmetric tensile and compressive stress in both first cantilever <NUM> and second cantilever <NUM> that will cancel. The resulting net electric charge will be zero.

Further, mechanically linking first cantilever <NUM> with second cantilever <NUM> helps limit MEMS device body <NUM> movement in the z-direction preventing excessive travel that can lead to breakage. Circuitous cuts <NUM> define the stiffness in pivot spring <NUM> and reduce the size that pivot spring <NUM> takes up.

<FIG> is a perspective view of MEMS device <NUM> in a relaxed state. <FIG> is a perspective view of MEMS device <NUM> under flexion. <FIG> and <FIG> will be discussed together. MEMS device <NUM> includes top layer <NUM>, bottom layer <NUM>, first mooring portion <NUM>, second mooring portion <NUM>, MEMS device body <NUM>, first margin <NUM>, first slot <NUM>, second margin <NUM>, and second slot <NUM>. MEMS device body <NUM> includes first cantilever <NUM>, pivot spring <NUM>, second cantilever <NUM>, circuitous cuts <NUM>, first proof mass <NUM>, and second proof mass <NUM>.

MEMS device <NUM> is discussed above in reference to <FIG> and <FIG>. MEMS device body <NUM> is between first mooring portion <NUM>, second mooring portion <NUM>, first margin <NUM>, and second margin <NUM>. First slot <NUM> is between MEMS device body <NUM> and first margin <NUM> running from first mooring portion <NUM> to second mooring portion <NUM>. Second slot <NUM> is between first margin <NUM> and MEMS device body <NUM> running from first mooring portion <NUM> to second mooring portion <NUM>. MEMS device body <NUM> includes first cantilever <NUM>, pivot spring <NUM>, and second cantilever <NUM>. MEMS device body <NUM> attaches to first mooring portion <NUM> and second mooring portion <NUM> of MEMS device <NUM> by first cantilever <NUM> and second cantilever <NUM>, respectively. Pivot spring <NUM> is between first cantilever <NUM> and second cantilever <NUM>. Pivot spring <NUM> includes circuitous cuts <NUM> extending through top layer <NUM> and bottom layer <NUM>. First proof mass <NUM> attaches to a bottom of bottom layer <NUM> of first cantilever <NUM>. Second proof mass <NUM> attaches to a bottom of bottom layer <NUM> of second cantilever <NUM>. MEMS device <NUM> lies in an x-y-z-plane where the MEMS device body <NUM> is significantly in the x-y-plane when in the relaxed state, first margin <NUM> runs alongside the x-axis, and first mooring portion <NUM> runs alongside the y-axis.

Upon vibration in the z-direction, MEMS device body <NUM> will vibrate in the z-direction. <FIG> demonstrates how first cantilever <NUM> and second cantilever <NUM> bend together when connected by pivot spring <NUM> in response to force in the z-direction. This bending in the same direction causes mechanical stress in the piezoelectric material of top layer <NUM> of MEMS device <NUM>. First mooring portion <NUM>, second mooring portion <NUM>, first margin <NUM>, and second margin <NUM> all stay in place allowing MEMS device <NUM> to attach to a stable structure while MEMS device body <NUM> vibrates. First slot <NUM> and second slot <NUM> allow MEMS device body <NUM> to vibrate freely from first margin <NUM> and second margin <NUM>.

Connecting first cantilever <NUM> and second cantilever <NUM> with pivot spring <NUM> causes first cantilever <NUM> and second cantilever <NUM> to move in-phase. In-phase movement allows for the electrical signal in first cantilever <NUM> and second cantilever <NUM> to be the same sign. Pivot spring <NUM> eliminates the opposite charge at an inflection point of MEMS device body <NUM> during vibration and lowers signal loss in MEMS device <NUM>. Connecting first cantilever <NUM> with second cantilever <NUM> limits the z-direction movement in MEMS device <NUM> and lowers the occurrence of breakage. MEMS device <NUM> allows for limited net charge of parasitic rocking vibrations along the x-axis because stretching motion from first cantilever <NUM> will be cancelled from compressive motion in second cantilever <NUM>. Further, twisting motions caused by y-direction forces are lowered because first cantilever <NUM> and second cantilever <NUM> move symmetrically. This symmetrical motion will induce both tensile and compressive stress equally in both first cantilever <NUM> and second cantilever <NUM> so the net electric charge generated by each MEMS device <NUM> will be zero. First slot <NUM> and second slot <NUM> allow for MEMS device body <NUM> to move independently of first margin <NUM> and second margin <NUM>. This allows MEMS device <NUM> to be solidly anchored while MEMS device body <NUM> moves in response to vibrations.

<FIG> is a top view of an alternate example of MEMS device <NUM> including pivot spring <NUM> connecting first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM>. MEMS device <NUM> includes top layer <NUM>, bottom layer <NUM>, pivot spring <NUM>, first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, fourth cantilever <NUM>, and circuitous cuts <NUM>. MEMS device <NUM> further includes first mooring portion <NUM>, second mooring portion <NUM>, third mooring portion <NUM>, fourth mooring portion <NUM>, first proof mass <NUM>, second proof mass <NUM>, third proof mass <NUM>, fourth proof mass <NUM>, first cut <NUM>, second cut <NUM>, third cut <NUM>, and third cut <NUM>.

MEMS device <NUM> is manufactured as a single piece. Top layer <NUM> is a first layer made of a piezoelectric material, such as aluminum nitride or PZT. Bottom layer <NUM> is a second layer made of a substrate material, such as surface-doped silicon. Bottom layer <NUM> is stiffer than top layer <NUM>. Pivot spring <NUM> is located at a center of MEMS device <NUM> and connects first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM>. Circuitous cuts <NUM> in pivot spring <NUM> extend through top layer <NUM> and bottom layer <NUM>.

First cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM> are in operable communication with pivot spring <NUM>. Each of first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM> have a trapezoidal shape. First cantilever <NUM> is across from second cantilever <NUM>. Third cantilever <NUM> is positioned between first cantilever <NUM> and second cantilever <NUM>. Fourth cantilever <NUM> is across from third cantilever <NUM> and positioned between first cantilever <NUM> and second cantilever <NUM>. First cantilever <NUM> is connected to first mooring portion <NUM>. Second cantilever <NUM> is connected to second mooring portion <NUM>. Third cantilever <NUM> is connected to third mooring portion <NUM>. Fourth cantilever <NUM> is connected to fourth mooring portion <NUM>. MEMS device <NUM> can attach to support frame <NUM> shown in <FIG> by first mooring portion <NUM> attaching to first attachment site <NUM>, second mooring portion <NUM> attaching to second attachment site <NUM>, third mooring portion <NUM> attaching to third attachment site <NUM>, and fourth mooring portion <NUM> attaching to fourth attachment site <NUM>. First proof mass <NUM> is connected to a bottom of bottom layer <NUM> of first cantilever <NUM>. Second proof mass <NUM> is connected to a bottom of bottom layer <NUM> of second cantilever <NUM>. Third proof mass <NUM> is connected to a bottom of bottom layer <NUM> of third cantilever <NUM>. Fourth proof mass <NUM> is connected to a bottom of bottom layer <NUM> of fourth cantilever <NUM>. First cut <NUM> is between first cantilever <NUM> and fourth cantilever <NUM>. Second cut <NUM> is between second cantilever <NUM> and third cantilever <NUM>. Third cut <NUM> is between third cantilever <NUM> and first cantilever <NUM>. Fourth cut <NUM> is between fourth cantilever <NUM> and second cantilever <NUM>. First cut <NUM>, second cut <NUM>, third cut <NUM>, and fourth cut <NUM> extend through top layer <NUM> and bottom layer <NUM>.

When MEMS device <NUM> senses vibration, first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM> move together because of pivot spring <NUM>. The piezoelectric material of top layer <NUM> of MEMS device <NUM> creates charge due to the mechanical movements. First proof mass <NUM>, second proof mass <NUM>, third proof mass <NUM>, and fourth proof mass <NUM> can be adjusted to tune MEMS device <NUM> to detect a certain resonant frequency. MEMS device <NUM> can also be tuned to a specific resonance frequency depending on the stiffness of bottom layer <NUM>. First cut <NUM>, second cut <NUM>, third cut <NUM>, and fourth cut <NUM> allow first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM> to move independently.

The trapezoidal shape of first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM> of MEMS device <NUM> allows for maximized piezoelectric bending area on top layer <NUM>. The trapezoidal shape also minimizes the area occupied by pivot spring <NUM>. Linking first cantilever <NUM>, second cantilever <NUM>, third cantilever <NUM>, and fourth cantilever <NUM> by pivot spring <NUM> allows MEMS device <NUM> to move in a synchronized fashion that allows for the electrical signal to be additive across the whole surface. Further, parasitic vibrational mode sensing is minimized by a four-cantilever system because pivot spring <NUM> forces the system of cantilevers to operate in phase and reduces secondary vibrational modes as discussed regarding <FIG> and <FIG>. Pivot spring <NUM> limits the movement of MEMS device <NUM> and lowers the occurrence of breakage. Circuitous cuts <NUM> in pivot spring <NUM> define the stiffness in pivot spring <NUM> and reduce the size of pivot spring <NUM>.

Claim 1:
A MEMS device for a MEMS vibrometer, the MEMS device comprising:
a first layer (<NUM>, <NUM>) of the MEMS device;
a second layer (<NUM>, <NUM>) of the MEMS device connected to the first layer of the MEMS device;
a first mooring portion (<NUM>, <NUM>) at a first side of the MEMS device;
a second mooring portion (<NUM>, <NUM>) at a second side of the MEMS device opposite the first mooring portion; and
a MEMS device body (<NUM>) connected to the first mooring portion at a first side of the MEMS device and connected to the second mooring portion at a second side of the MEMS device opposite the first mooring portion, the MEMS device body comprising:
a first cantilever (<NUM>, <NUM>) attached to the first mooring portion at a first side of the first cantilever;
a second cantilever (<NUM>, <NUM>) attached to the second mooring portion at a first side of the second cantilever;
a spring (<NUM>, <NUM>) between the first cantilever and the second cantilever, the spring connected to the first cantilever at a second side of the first cantilever opposite the first mooring portion and connected to the second cantilever at a second side of the second cantilever opposite the second mooring portion;
wherein the MEMS device is manufactured as a single piece, the first cantilever, the second cantilever, and the spring being formed of the first layer and the second layer of the MEMS device ;
and characterized by:
a first proof mass (<NUM>, <NUM>) connected to a bottom of the second layer of the MEMS device on the first cantilever; and
a second proof mass (<NUM>, <NUM>) connected to a bottom of the second layer of the MEMS device on the second cantilever.