CN113620232A

CN113620232A - Piezoelectric actuator with deformable structure having improved mechanical properties and method for manufacturing same

Info

Publication number: CN113620232A
Application number: CN202110489899.8A
Authority: CN
Inventors: D·朱斯蒂; M·费雷拉; C·L·佩瑞里尼
Original assignee: STMicroelectronics SRL
Current assignee: STMicroelectronics SRL
Priority date: 2020-05-07
Filing date: 2021-05-06
Publication date: 2021-11-09
Also published as: CN215974953U

Abstract

Embodiments of the present disclosure relate to a piezoelectric actuator of a deformable structure with improved mechanical properties and a method of manufacturing the same. The MEMS actuator is formed of a body surrounding a cavity and a deformable structure suspended over the cavity and formed of a movable portion and a plurality of deformable elements. The deformable elements are arranged in succession to each other, connecting the movable portion to the body, and each deformable element is subjected to deformation. The MEMS actuator further includes at least one set of a plurality of actuation structures supported by the deformable elements and configured such that the translation of the movable portion is greater than the deformation of each deformable element. Each actuation structure has a respective first piezoelectric region.

Description

Piezoelectric actuator with deformable structure having improved mechanical properties and method for manufacturing same

Technical Field

The present disclosure relates to a piezoelectric actuator of a deformable structure with improved mechanical properties and a method of manufacturing the same. In particular, reference is made to piezoelectric actuators manufactured using MEMS (micro electro mechanical systems) technology, such as liquid flow control valves, micro springs for loudspeakers, micro mirrors, microtools such as micro tweezers or micro scissors.

Background

As is known, a MEMS actuator is an electronic device, typically made from a wafer of semiconductor material (e.g. silicon), which is capable of causing deformation of a movable element, such as a diaphragm or a cantilever.

MEMS actuators can operate according to different actuation principles, including electrostatic, electromagnetic, and piezoelectric actuation. In detail, MEMS actuators operating according to the piezoelectric actuation principle differ in high energy efficiency and high deformation accuracy of the movable element; for this reason, piezoelectric MEMS actuators are becoming increasingly popular.

Furthermore, actuators with piezoelectric actuation systems are known for manufacturing devices such as microfluidic valves used in flow regulating devices, micro mirrors and precision surgical tools.

In the following, reference will be made to a flow regulator by way of example. A flow regulator is a device that allows control of the amount of fluid flowing within a fluid channel, and may be used, for example, at the industrial level to control process parameters of a machine used to manufacture semiconductor devices.

Generally, a flow regulator includes a fluid passage having an inlet and an outlet, a valve that regulates an amount of fluid flowing in the fluid passage, a flow meter that measures a fluid flow rate in the fluid passage, and a control unit.

Disclosure of Invention

The present disclosure discloses a piezoelectric actuator that overcomes the limitations of the known solutions, in particular, that allows for a reduced size and a lower bias voltage relative to the known solutions.

According to the present disclosure, a piezoelectric actuator and a method of manufacturing the same are provided.

At least one embodiment of a MEMS actuator of the present disclosure is directed to a MEMS actuator comprising a body surrounding a cavity. A deformable structure on the cavity, the deformable structure comprising a movable portion and a plurality of deformable elements arranged in series. A plurality of deformable elements connect the movable portion to the body. The deformable structure further includes a plurality of arms coupling the movable portion, the plurality of deformable elements, and the body together. The deformable structure also includes a plurality of reinforcing structures, a respective one of the plurality of reinforcing structures being integrated with a respective one of the plurality of arms. The MEMS actuator further includes at least one set of a plurality of actuation structures on the deformable element.

At least one embodiment of a flow regulator of the present disclosure is directed to a flow regulator including a channel body, a fluid channel in the channel body and having an end portion, and a passage cross-section adjacent the end portion. The flow regulator also includes a micro-electromechanical system (MEMS) actuator having a cavity, a body surrounding the cavity, and a deformable structure aligned with the cavity. The deformable structure comprises a movable portion having a surface facing the end portion and configured to vary a passage section arranged between the end portion and the movable portion. The deformable structure further includes a plurality of deformable elements surrounding the movable portion, at least one plurality of actuation structures on the plurality of deformable elements, and at least one detection structure on the plurality of deformable elements. The flow regulator also includes a control unit coupled to the MEMS actuator, the control unit configured to provide a bias voltage to the at least one plurality of actuation structures and receive a sense voltage from the at least one sensing structure.

At least one embodiment of a speaker of the present disclosure is directed to the speaker including a housing defining a first cavity, a diaphragm attached to the housing and over the cavity, and a MEMS actuator. The MEMS actuator includes a second cavity, a body surrounding the second cavity, and a deformable structure coupled to the diaphragm and configured to cause deformation of the diaphragm. The deformable structure includes a movable portion coupled to the diaphragm, a plurality of deformable elements surrounding the movable portion, at least one set of a plurality of actuation structures on the plurality of deformable elements, and at least one detection structure on the plurality of deformable elements. The speaker further includes a control unit coupled to the MEMS actuator and configured to: providing a bias voltage to the at least one plurality of actuation structures and receiving a detection voltage from the at least one detection structure.

At least one embodiment of a method of the present disclosure is directed to fabricating a MEMS actuator that includes forming at least one plurality of actuation structures on a first surface of a substrate opposite a second surface of the substrate. Forming a deformable structure includes forming a movable portion, forming a plurality of deformable elements arranged consecutively with respect to each other and connecting one of the plurality of deformable elements to the movable portion, and forming a frame and connecting the frame to one of the plurality of deformable elements by forming a cavity extending into the second surface of the substrate.

Drawings

For a better understanding of the present disclosure, embodiments thereof will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-section of a known flow regulator;

fig. 2A is a perspective view from above of an embodiment of the piezoelectric actuator of the present invention;

FIG. 2B is a cross-section of the deformation sensor of the piezoelectric actuator of FIG. 2A taken along section line IIA-IIA of FIG. 4A when at rest;

fig. 3 is a perspective view from below of the piezoelectric actuator of fig. 2A;

FIG. 4A is a top view of the piezoelectric actuator of FIG. 2A;

FIG. 4B is a cross-section of the actuating element of the piezoelectric actuator of FIG. 2A taken along section line IVA-IVA of FIG. 4A when at rest;

FIG. 4C is a cross-section of the actuating element of FIG. 4B in a deformed condition taken along section line IVA-IVA of FIG. 4A;

FIG. 5 is a perspective view of the piezoelectric actuator of FIG. 2A in use, according to a first mode of use;

FIG. 6 is a perspective view of the piezoelectric actuator of FIG. 2A in use, according to a second mode of use;

FIG. 7 is a schematic cross-section of a flow regulator incorporating the piezoelectric actuator of FIG. 2A at rest;

FIG. 8 shows the flow regulator of FIG. 7 under different operating conditions;

FIG. 9 is a schematic cross-section of a different flow regulator incorporating the piezoelectric actuator of FIG. 2A at rest;

FIG. 10 shows the flow regulator of FIG. 9 in a different operating condition;

FIG. 11 is a schematic cross-section of a flow regulator incorporating another embodiment of a piezoelectric actuator of the present invention at rest;

FIG. 12 is a simplified perspective view of a speaker incorporating a piezoelectric actuator of the present invention; and

fig. 13A to 21A and 13B to 21B show cross sections of the piezoelectric actuator of fig. 2A taken along section lines XIIIA to XIIIA and XIIIB to XIIIB of fig. 4A, respectively, in successive manufacturing steps.

Detailed Description

The present disclosure relates to at least one embodiment of a piezoelectric actuator and at least one embodiment of a method of manufacturing the same. The details of which will be discussed in further detail herein.

Fig. 1 shows the construction of a known flow regulator 10, for example using piezoelectric actuation. The flow regulator 10 comprises a body 11; a fluid channel 12 extending into the body 11 and having an inlet 13 and an outlet 14; a valve 15; a flow meter 16; and a control unit 20.

The fluid channel 12 here comprises a first and a second

horizontal portion

21A, 21B, which are continuously coupled to each other to the inlet 13 and the outlet 14 by a first vertical portion 22, a passage 23 and a second vertical portion 24, respectively. Based on the orientation of the flow regulator 10 in fig. 1, the

portions

21A, 21B of the fluid channel 12 are depicted as horizontal and the

portions

22, 24 are depicted as vertical.

The first vertical portion 22 here extends between the first horizontal portion 21A and the surface 11A of the body 11 at the region of the valve 15, as explained below; the second vertical section 24 here extends in the region of the valve 15 between the surface 11A of the body 11 and the second horizontal section 21B and is separated from the first vertical section 22 by a wall 25 of the body 11.

The flow meter 16 is coupled to the first horizontal portion 21A of the fluid passage 12 and the control unit 20. The flow meter 16 is configured to measure a quantity associated with the quantity of fluid flowing in the fluid passage 12. For example, the flow meter 16 may include a resistor (not shown in FIG. 1) disposed along the fluid channel 12 in a known manner and having a resistance associated with the existing flow.

The valve 15 comprises a support 27 coupled to the body 11, a diaphragm 26 coupled to the support 27, and a piezoelectric actuation system 28 carried by the diaphragm 26.

In detail, the membrane 26 is formed, for example, of a metallic material, is constrained to the body 11 by means of a support 27, and is suspended on and facing the first and second

vertical portions

22, 24 and the wall 25, so as to form, together with said wall, the passage 23 of the fluid channel 12.

The piezoelectric actuation system 28 is coupled to the control unit 20 and varies the distance of the diaphragm 26 from the wall 25 to vary the flow.

In use, an amount of fluid passes through the fluid channel 12, which amount may be a selected amount. In this regard, the control unit 20 applies a bias voltage to the piezoelectric actuation system 28, thereby causing deformation of the diaphragm 26. Accordingly, the cross section of the passage 23 is changed, thereby changing the amount of fluid flowing in the fluid channel 12.

In particular the distance between the membrane 26 and the wall 25, can be continuously adjusted by modulating the bias voltage applied to the piezoelectric actuation system 28; thus, the valve 15 can assume a plurality of operating states ranging from the fully closed state to the fully open state, respectively corresponding to a quantity of fluid of zero and maximum value proportional to the value of the bias voltage.

Meanwhile, the control unit 20 measures the flow rate of the fluid in the fluid passage 12, and may control the opening degree of the valve 15 based on the measured flow rate.

However, the flow regulator 10 as shown in fig. 1 has disadvantages.

For example, the flow regulator 10 has a large size relative to embodiments of the flow regulator of the present disclosure. In fact, the flow meter 16 is placed at a distance from the valve 15.

Furthermore, the piezoelectric actuation system 28 has a large size. For example, a piezoelectric mass manufactured using bulk techniques may have a thickness of even a few millimeters. Accordingly, the actuation system 28 is not suitable for applications where a high degree of miniaturization is beneficial.

Furthermore, the piezoelectric actuation system 28 comprises a high bias voltage of even a few hundred volts to obtain deformations of tens of microns. Such high bias voltages may use complex and expensive integration processes in the above-described devices and may pose a risk to users of the flow regulator 10.

In addition, the flow regulator 10 has low energy efficiency because the flow meter 16 performs active detection of fluid flow, i.e., through a current path. Therefore, the demand regulator consumes a large amount of energy.

The present disclosure relates to embodiments of piezoelectric actuators fabricated using piezoelectric film MEMS (micro-electro-mechanical systems) technology described herein. For example, the piezoelectric actuator 50 is fabricated using piezoelectric film MEMS technology as described herein.

As shown in fig. 2A, 3 and 4A, the piezoelectric actuator 50 is formed in a body 51 having a first face or surface 51A and a second face or surface 51B, and includes a substrate 57 of a semiconductor material (e.g., silicon), and a surface layer 58 covering the substrate 57, the surface layer being formed, for example, of a plurality of monolayers, for example, a layer of a semiconductor material (such as polysilicon), and at least one layer of an insulating material, for example, Tetraethylorthosilicate (TEOS).

A cavity 52, for example cylindrical, extends from the second face 51B to the inside of the body 51 and passes completely through the body 51. Thus, the substrate 57 and the portion of the surface layer 58 above the substrate form a frame 53 surrounding the deformable structure 54, which frame is here formed of the same material as the material forming the surface layer 58 and suspended over the cavity 52.

The surface layer 58 is much thinner than the substrate 57 and the horizontally extending portions of the deformable structure 54 that are substantially parallel to the first face 51A of the body 51.

Thus, the deformable structure 54 is substantially planar.

The deformable structure 54 has symmetry in plan view, for example circular symmetry with a center O or polygonal with a large number of sides, and comprises a plurality of deformable rings 55 concentric with each other, and a movable central portion 56 surrounded by the deformable rings 55 and having a circular cross-section in plan view.

In particular, in this embodiment, the deformable structure 54 is formed of three deformable rings, including first, second and third deformable rings 55A-55C.

The first ring 55A is coupled to the frame 53 by a plurality of first connection portions 60. Each first connection portion 60 is suspended on and overlaps the cavity 52, and each first connection portion 60 extends between the frame 53 and the first deformable ring 55A, forming a single piece (or unitary) therewith.

In detail, there are three first connection portions 60, spaced 120 ° from each other along the circumference of the first deformable ring 55A.

The second deformable ring 55B is disposed internally relative to the first deformable ring 55A such that the first deformable ring 55A surrounds the second deformable ring 55B. The second deformable ring 55B is coupled to the first deformable ring 55A by a plurality of second connection portions 65. Each second connecting portion 65 is suspended from and overlaps the cavity 52, and each second connecting portion 65 extends between the first and second deformable rings 55A, 55B, forming a single piece therewith.

In detail, there are three second connection portions 65 spaced 120 ° from each other along the circumference of the second deformable ring 55B and having in this embodiment an offset of 60 ° with respect to the first connection portions 60.

The third deformable ring 55C is disposed internally with respect to the second deformable ring 55B and is coupled to the second deformable ring 55B by a plurality of third connecting portions 70. Each third connecting portion 70 is suspended from and overlaps the cavity 52 and extends between the second and third deformable rings 55B, 55C, forming a single piece therewith.

In detail, there are three third connection portions 70 spaced 120 ° from each other along the circumference of the third deformable ring 55C and having, in this embodiment, an offset of 60 ° with respect to the second connection portions 65. In other words, the third connection portion 70 has a zero offset with respect to and is radially aligned with a corresponding one of the first connection portions 60.

The third deformable ring 55C is also coupled to the movable center portion 56 by a plurality of fourth connecting portions 75. Each fourth connecting portion 75 is suspended on the cavity 52 and extends between the third deformable ring 55C and the movable central portion 56, forming a single piece therewith.

In detail, there are three fourth connecting portions 75, which are spaced 120 ° apart from each other along the circumference of the third ring 55C and which in this embodiment have an offset of 60 ° with respect to the third connecting portion 70. In other words, the fourth connection portion 75 has a zero offset with respect to a corresponding one of the second connection portions 65 and is radially aligned with a corresponding one of the second connection portions 65.

The first, second and third deformable rings 55A-55C carry a respective plurality of actuating structures 80 equal in number to one another, having the shape of curved bands, operatively divided into first and second sets of actuating

structures

80A, 80B and placed at a distance from one another.

Each actuation structure 80 (see fig. 4B for the first set of actuation structures 80A) is formed by a stack comprising a lower actuation electrode 81 made of an electrically conductive material, for example platinum; the piezoelectric actuation zone 82 is, for example, made of a single crystal ceramic material with a high relative permittivity (e.g. greater than 100), such as lead zirconate titanate (PZT), BaTiO₃KNN (potassium sodium niobate), PbTiO₂Or PbNb₂O₆(ii) a And an upper actuation electrode 83, and,the upper actuation electrode is made of an electrically conductive material, such as platinum, iridium oxide, yttrium, or a titanium tungsten alloy. The piezoelectric actuation area 82 is arranged between the upper actuation electrode 83 and the lower actuation electrode 81 so as to form a capacitor structure.

In detail, here, the lower actuation electrodes 81 of all the actuation structures 80 are formed by a single conductive area (not visible in fig. 2A) comprising a connection portion 87 (only partially visible here) for connection to a lower electrode pad 88, for electrical connection to an external bias circuit (not shown), for example to a reference potential (ground).

The upper actuation electrodes 83 of the first set of actuation structures 80A are connected to respective first set of upper electrode pads 90A by first conductive connection tracks 89A (only partially visible here) for electrical connection to an external bias circuit.

The upper actuation electrodes 83 of the second set of actuation structures 80B are connected to respective second set of upper electrode pads 90B by second conductive connection tracks 89B (only partially visible here) for electrical connection to an external bias circuit.

In this embodiment, the first, second and third deformable rings 55A-55C each carry six actuating structures 80. The bending straps forming the actuation structure 80 each cover a substantially equal circumferential arc and have a center C lying on a midline, defined here by a circular arc based on the orientation of the piezoelectric actuator 50 in fig. 4A and indicated in fig. 4A by a dashed line passing through the center C near the left-hand side of fig. 4A. The center C of each actuation structure 80 is equidistant from the center C of the respective adjacent actuation structure 80. In other words, the centers C of the actuating structures 80 are spaced 60 apart from each other along the circumference of the respective deformable ring 55, and the actuating structures 80 of each deformable ring 55A-55C are of equal length and are radially aligned with the actuating structures 80 of the adjacent deformable ring 55A-55C.

The first and second sets of actuating

structures

80A, 80B are alternately arranged in succession in each deformable ring 55A-55C; in particular, the centers C of the second set of actuating structures 80B are spaced 120 ° apart from one another along the circumference of the respective deformable ring 55 and have an offset of 60 ° with respect to the centers C of the respective adjacent first set of actuating structures 80A of the same deformable ring 55.

Furthermore, the center C of the first set of actuating structures 80A of the first deformable ring 55A has an offset of 60 ° with respect to the center C of the first set of actuating structures 80A of the second deformable ring 55B and has a zero offset with respect to (in other words, they are radially aligned with) the center C of the first set of actuating structures 80A of the third deformable ring 55C.

In addition, the deformable rings 55A-55C carry a plurality of reinforcing structures 85 (fig. 3 and 4A) that extend from the underside of the deformable ring 55 toward the interior of the cavity 52. A reinforcing structure 85 (one for each first set of actuating structures 80A) extends radially, each reinforcing structure being aligned with the centre C of a respective first set of actuating structures 80A and on the underside of a respective connecting portion; thus, the width of each reinforcing structure 85 in the radial direction is substantially equal to the sum of the widths of the respective deformable ring 55 and the respective connecting portion.

The reinforcing structure 85 is a single piece (or unitary) with the respective connecting portions (as explained below with reference to the manufacturing method) and is therefore integrated with the respective connecting portions.

In fact, the reinforcing structure 85 and the respective connecting portions operate as a pivoting structure in use, as explained in detail below.

In this embodiment, the deformable rings 55A-55C each carry three reinforcing structures 85 that are spaced 120 apart from each other along the circumference of the respective deformable ring 55. In detail, with respect to the first deformable ring 55A, each reinforcing structure 85 is integral with a respective first connection portion 60; with respect to the second deformable ring 55B, each reinforcing structure 85 is integral with the respective second connection portion 65; and with respect to the third deformable ring 55C, each reinforcing structure 85 is integral with a respective third connecting portion 70.

Furthermore, the movable central portion 56 carries a shutter structure 86 (fig. 3 and 4A), here formed in the same layer as the reinforcing structure 85, extending below the movable central portion 56 towards the inside of the cavity 52. Here, the shutter structure 86 has a circular cross-section in plan view, with a diameter smaller than or substantially equal to the cross-section of the movable central portion 56. The shutter structure 86 has a region that projects from the movable central portion 56 towards and into the cavity 52. The movable center portion 56 may be a platform suspended above and overlapping the cavity 52.

The deformable structure 54 also houses a plurality of deformation sensors, three of which 91 are shown in fig. 2A. The deformation sensor 91 may be a sensing structure or some other similar or analogous sensor.

The deformation sensors 91 are each carried by a respective deformable ring 55 and are each arranged between two adjacent actuating structures 80. In particular, in this embodiment, the deformable rings 55A-55C each carry one deformation sensor 91.

The deformation sensors 91 are each formed by a respective stack comprising a lower detection electrode 92 made of an electrically conductive material, such as platinum, a piezoelectric detection area 93, for example made of: having a low relative dielectric constant, for example, of the order of less than or substantially equal to 10, and having a loss tangent, for example, of less than 0.05, in particular substantially equal to 0.002, such as aluminum nitride, zinc oxide or polyvinylidene fluoride (PVDF) (here aluminum nitride). The piezoelectric sensing region 93 is disposed between the upper sensing electrode 94 and the lower sensing electrode 92 to form a capacitor structure, as shown in fig. 2B.

In this embodiment, the lower detection electrode 92 of each deformation sensor 91 is formed by the same single conductive region that forms the lower actuation electrodes 81 of all actuation structures 80. Further, a third conductive connection track 95, only partially shown here, connects the upper detection electrode 94 to a detection pad 96 (see fig. 2A) for electrical connection to an external measurement circuit (not shown).

The deformable structure 54 may form a shutter, for example, of a normally closed or normally open valve configuration, which is controlled to be fully open or fully closed or in flow modulation, as explained in detail below.

Specifically, in use, in the absence of a bias, the piezoelectric actuator 50 is in the position shown in figures 2A, 3 and 4A, in which the upper surface of the movable central portion 56 is flush with the first face 51A of the body 51. In other words, when the piezoelectric actuator 50 is at rest, the upper surfaces of the movable central portion 56, the

deformable elements

55A, 55B, 55C of the deformable structure 55 and the body 51 are substantially coplanar with one another in a plane such that the upper surfaces are aligned with one another.

To move the movable central portion 56 away from or towards the cavity 52, a bias voltage is selectively applied between the upper and

lower electrodes

83, 81 of the actuation structure 80, respectively, as explained below. In particular, the bias voltage causes deformation of the piezoelectric actuation regions 82, for example as shown in fig. 4C for the first set of actuation structures 80A. In fact, regardless of the bias voltage polarity, the piezoelectric actuation regions 82 experience equal buckling deformation, wherein the central portion of the actuation structure 80 is lowered relative to the side portions of the same actuation structure 80.

However, the different positions of the first set of actuating structures 80A (the central portions of the first set of actuating structures being constrained by the first, second and third connecting

portions

60, 65 and 70 and by the reinforcing structure 85) relative to the second set of actuating structures 80B determines the different deformations of the deformable ring 55 depending on whether the first set of actuating structures 80A or the second set of actuating structures 80B are biased, as described in detail below.

In fig. 5, a bias voltage V1, particularly a positive unipolar bias voltage of, for example, 40V, is applied to the first set of actuation structures 80A, while the second set of actuation structures 80B is unbiased (V2 ═ 0V).

In this biased condition, each first set of actuation structures 80A deforms approximately as shown for the first deformable ring 55A in fig. 4C.

As indicated, in the first deformable ring 55A, the central portion of the first set of actuating structures 80A is constrained to the frame 53 by the first connecting portion 60 and the respective reinforcing structure 85, thus remaining hardly deformed; instead, the end portions of the first set of actuating structures 80A are lifted upward.

Lifting the end portions of the first set of actuating structures 80A also results in lifting of the adjacent second set of actuating structures 80B of the first deformable ring 55A.

Furthermore, since the central portions of the actuating structures 80A of the first group of the second deformable ring 55B are constrained to the central portions of the actuating structures 80B of the second group of the first deformable ring 55A (by means of the second connecting portions 65 and the respective reinforcing structures 85), they are lifted, thus lifting for this reason the inner deformable rings (the second and third deformable rings 55B, 55C). In addition, the first set of actuating structures 80A of the second deformable ring 55B deforms similar to that described above, causing further lifting of the second set of actuating structures 80B of the second deformable ring 55B and thus of the third deformable ring 55C.

Similarly, the first set of actuating structures 80A of the third deformable ring 55C deforms and causes further lifting of the second set of actuating structures 80B of the third deformable ring 55C and thus of the movable central portion 56, as shown in fig. 5, wherein the piezoelectric actuator 50 is represented in grayscale, wherein the darker portions are the portions that are deformed more relative to the rest position.

In fig. 6, a bias voltage, particularly a positive unipolar as previously described, is applied to the second set of actuation structures 80B. Here, the piezoelectric actuator 50 is again represented in grayscale, wherein darker shading corresponds to greater deformation relative to the rest position.

In this case, the second set of actuating structures 80B of the first deformable ring 55A deforms, as shown in fig. 4C, and causes a downward displacement of its central portion towards the inside of the cavity 52 with respect to its end portions, which are constrained to the adjacent first set of actuating structures 80A, which are not deformed by being unbiased and in turn are constrained to the frame 53 by the first connecting portions 60 and the respective reinforcing structures 85.

The first set of actuating structures 80A of the second deformable ring 55B, which are not biased and constrained to the second set of actuating structures 80B of the first deformable ring 55A (by the second connecting portion 65 and the respective reinforcing structure 85), also move downwards (towards the inside of the cavity 52). Furthermore, the deformation of the second set of actuating structures 80B of the second deformable ring 55B causes a further downward displacement of the respective end portion and hence of the third deformable ring 55C towards the interior of the cavity 52.

Similarly, deformation of the second set of actuation structures 80B of the third deformable ring 55C causes the movable central portion 56 to lower further toward the interior of the cavity 52.

In fact, the deformable structure 54 allows a high translation of the movable central portion 56 with respect to the rest position, which is greater than the deformation of each deformable ring 55 caused by the respective actuating structure 80, both moving towards the inside of the cavity 52 and away from the cavity 52. High displacement can be achieved by applying a low bias voltage.

The maximum deformation of the deformable structure 54 depends on a number of factors, including the number of deformable rings 55, the thickness and diameter of the deformable structure 54 and the movable central portion 56, the thickness of the reinforcing structure 85 and the shutter structure 86, and the maximum applicable voltage; these factors are parameters that can be modified during the design step depending on the particular application.

For example, in simulations performed by the applicant, it has been verified that the movable central part can translate up to 80 μm (40 μm in each of the two directions) with a bias voltage of 40V.

The deformation of the deformable structure 54 is such that it allows a vertical displacement of the movable central portion 56, while keeping the shutter structure 86 substantially parallel with respect to the rest position, a feature that can be used for specific applications.

Further, referring again to fig. 2A, in use, deformation of the deformable structure 54 generates mechanical stress in the deformable ring 55. The mechanical stress generates a detection voltage between the lower detection electrode 92 and the upper detection electrode 94 of each deformation sensor 91 in the piezoelectric detection region 93 (fig. 2B). In a known manner, the detection voltage can be measured and converted by a measuring circuit (for example shown in fig. 7) into a deformation value of the deformable structure 54 and, consequently, into a displacement value of the movable central portion 56 with respect to the rest position.

Thus, the measurement of the detection voltage allows controlling the state of the piezoelectric actuator 50 through a closed-loop control system and in real time.

Furthermore, the size of the piezoelectric actuator 50 is significantly reduced, since both the actuation structure 80 and the deformation sensor 91 are integrated in the same die.

Furthermore, since the deformation sensor 91 is of a piezoelectric type, the measurement of the detection voltage is a passive detection, i.e., does not imply the passage of a current, thus making the piezoelectric actuator 50 energy-efficient.

As shown in fig. 7, the piezoelectric actuator 50 may be integrated into the flow regulator 200. In addition to the piezoelectric actuator 50, the flow regulator 200 includes a body 205 and a fluid channel 210 having an inlet portion 210A and an outlet portion 210B.

The body 205 is made of a semiconductor material, for example silicon, and is formed by: a horizontal portion 206, a tubular projection 207 extending transversely to the horizontal portion from the horizontal portion 206, and a through hole 208 having a mouth forming an inlet portion 210A of the fluid channel 210 and passing through the tubular projection 207.

The horizontal portion 206 of the body 205 is joined to the substrate 57 of the piezoelectric actuator 50 by means of a joining region 215, so that the horizontal portion 206 of the body 205 faces the cavity 52 and the tubular projection 207 is aligned with the shutter structure 86. In particular, in this embodiment, the height of the tubular projection 207 is such that, at rest, the shutter structure 86 is in contact with one end of the tubular projection 207.

Furthermore, the flow regulator 200 comprises a control unit 220 coupled to the piezoelectric actuator 50, in particular to the actuation structure 80 and the deformation sensor 91, through the

contact pads

88, 90A, 90B and 96 of fig. 2A (as schematically shown in fig. 7), for exchanging signals and electrical quantities for controlling the flow regulator 200.

To this end, the control unit 220 comprises input/

output ports

221, 222 for receiving control signals and sending detection signals to the outside (e.g. towards the user), a control stage 223 (e.g. a CPU) for processing the signals provided for control, and a drive stage 224 for controlling the flow regulator 200. The control stage 223 may, for example, store a conversion table between nominal flow values and corresponding bias voltage values to be supplied to the piezoelectric actuator 50.

In use, a user may set a nominal flow value of the fluid within the fluid channel 210 through the input port 221. Based on the stored table, the control unit 220 applies bias voltages of appropriate values to the first set of actuation structures 80A. As previously described and as shown in fig. 8, the deformable structure 54 is deformed and the movable central portion 56 (which thus forms here a cap element) moves the shutter structure 86 away from the end of the tubular projection 207, thus creating a passage 230 of the fluid channel 210 and reciprocally separating the deformable ring 55 and the movable central portion 56 from each other, so as to form an outlet portion 210B of the fluid channel 210. Thus, in the deformed position of fig. 8, the passageway 230 connects the inlet portion 210A to the outlet portion 210B through the through-hole 208 and thus allows the flow of liquid or gas (e.g., fluid) supplied to the inlet portion 210A.

Meanwhile, as previously described, the deformation sensor 91 (not shown here) detects the stress generated by the deformation of the deformable structure 54, and supplies a corresponding detection voltage to the control unit 220.

The control unit 220 may then compare the value of the detected voltage (or a quantity related thereto) with a suitable calibration parameter corresponding to the flow value and verify in real time that the fluid flow meets the nominal value. If not, the control unit 220 may modify the bias voltage in order to bring the flow to the nominal value.

Fig. 9 and 10 show another embodiment of a flow regulator similar to the flow regulator 200, here indicated at 250, and therefore common elements will be indicated with the same reference numerals.

In detail, the flow regulator 250 includes a piezoelectric actuator 50, a body 255, and a fluid channel 260 having an inlet portion 260A and an outlet portion 260B. Unlike the flow regulator 200 of fig. 7, the tubular projection 207 has a height such that its end is at a distance from the shutter structure 86 when at rest, and the fluid passage 260 of the flow regulator 250 forms a passage 265 delimited by the shutter structure 86 and the tubular projection 207 when at rest.

In this manner, fluid may flow between the inlet portion 260A and the outlet portion 260B of the fluid channel 260 without a bias voltage.

In use, when flow through the fluid channel 260 is altered or blocked, a bias voltage is applied to the actuation structure 80 to set the nominal flow value. In this embodiment, a bias voltage is applied to the second set of actuation structures 80B causing downward displacement of the deformable structure 54 and causing the shutter structure 86 to move closer to the tubular projection 207 as shown in fig. 10. In this way, the cross section of the passage 265 is reduced and therefore the flow rate is reduced; with the passageway 265 fully closed, flow may also be completely interrupted.

FIG. 11 illustrates a flow regulator 270 incorporating a piezoelectric actuator of the present invention, hereinafter referred to as piezoelectric actuator 280, in accordance with another embodiment. The flow regulator 270 and the piezoelectric actuator 280 have similar structures as the flow regulator 250 and the piezoelectric actuator 50, respectively, and therefore common elements are identified by the same reference numerals.

In particular, here, the movable central portion 56 directly faces the tubular projection 207 and, at rest, is at a distance from the tubular projection 207, forming a passage 285. In use, the bias voltage may move the movable central portion 56 closer to or away from the tubular protrusion 207, thereby changing the cross-section of the passage 285, as previously explained. In fact, here, the passage 285 is delimited by the tubular projection 207 and the movable central portion 56, and the shutter structure 86 is absent.

According to another embodiment, the

piezoelectric actuator

50, 280 may be integrated into a speaker.

In particular, in fig. 12, the speaker 300 includes the piezoelectric actuator 50. However, it will be apparent to those skilled in the art that piezoelectric actuator 280 may also be integrated into speaker 300 in a similar manner.

The speaker 300 includes a housing 303 defining a cavity 305; a support 307 attached to the housing 303; and a diaphragm 306 carried by a support 307 and suspended over the cavity 305.

The housing 303 is approximately a hemispherical or dome-shaped housing; the support 307 and the diaphragm 306 enclose the housing at the back.

The loudspeaker 300 further comprises an actuator 50 and a control unit 320 arranged inside the cavity 305. Alternatively, the control unit 320 may be made outside the housing 303.

The control unit 320 is coupled to the piezoelectric actuator 50, in particular to the actuation structure 80, as has been described for example with reference to fig. 7.

The movable center portion 56 and the shutter structure 86 of the piezoelectric actuator 50 are mechanically coupled to the diaphragm 306, e.g., the movable center portion and the shutter structure are bonded to the diaphragm.

In use, the control unit 320 applies a bias voltage of suitable frequency to the first and/or second set of

actuation structures

80A, 80B, causing a displacement of the movable central portion 56 (as described previously) and thus a deformation of the diaphragm 306, which thus oscillates back and forth (i.e. towards the inside and outside of the cavity 305) relative to a plane perpendicular to the plane of the drawing. Thus, the deformation of the diaphragm 306 generates sound waves that may propagate outside the speaker 300.

Accordingly, the speaker 300 may have a reduced size and high energy efficiency due to the characteristics of the piezoelectric actuator 50 described previously.

The manufacturing steps leading to the piezoelectric MEMS actuator 50 shown in fig. 2A will be described below.

In particular, fig. 13A-21A illustrate a method of manufacturing the piezoelectric MEMS actuator 50 at the actuation structure 80, the deformation sensor 91, and a portion of the deformable structure 54 in circumferential cross-sections taken along the deformable ring 55; fig. 13B-21B illustrate a method of manufacturing the piezoelectric MEMS actuator 50 at the actuating structure 80 and portions of the deformable structure 54 and the frame 53 in radial cross-sections taken through different adjacent deformable rings 55.

Fig. 13A and 13B show a wafer 400 that has undergone a first processing step. In detail, the wafer 400 comprises a working substrate 405 made of a semiconductor material, for example silicon, having a first and a

second surface

405A, 405B arranged on the front and back side of the wafer 400, respectively. A first shaping layer 406, for example made of deposited tetraethyl orthosilicate (TEOS), having a thickness of, for example, at least 1 μm, here 1 μm, extends over the first surface 405A of the working substrate 405.

Subsequently, as shown in fig. 14A and 14B, the first shaping layer 406 is patterned by selective etching to form a plurality of first lower shaping regions 407 and second lower shaping regions 408, wherein it is desired to subsequently form a plurality of reinforcement structures 85 and shutter structures 86, respectively, as described in detail below.

Furthermore, a stiffening layer 409 made of a semiconductor material, for example polysilicon, is formed, for example epitaxially grown, on the first surface 405A of the work substrate 405, on the plurality of first lower shaping regions 407 and on the second lower shaping region 408; then, the reinforcing layer 409 is subjected to Chemical Mechanical Polishing (CMP) to form a flat upper surface. The stiffening layer 409 has a thickness greater than the first shaping layer 406, which in this embodiment is, for example, 25 μm.

Subsequently, a first insulating layer 410, for example made of Tetraethylorthosilicate (TEOS) and here having a thickness comparable to the first shaping layer 406, for example 1 μm, is deposited on the stiffening layer 409.

In fig. 15A and 15B, a structural layer 411 made of a semiconductor material such as polysilicon is deposited on the first insulating layer 410. The structural layer 411 has a thickness selected based on the desired mechanical properties, for example, in this embodiment, the structural layer has a thickness of 10 μm.

A second insulating layer 412, for example made of tetraethyl orthosilicate (TEOS) and here having a thickness of, for example, 0.5 μm, is deposited on the structural layer 411.

Subsequently, in fig. 16A and 16B, a first conductive layer 420 made of, for example, platinum is deposited on the second insulating layer 412; an actuation layer 421 of a single crystal piezoelectric material having a high relative permittivity (for example greater than 100), such as lead zirconate titanate (PZT), BaTiO, etc., and having a thickness in the range 1 μm to 3 μm, for example, in particular, 2 μm, is deposited on the first conductive layer 420₃KNN (potassium sodium niobate) and PbTiO₂Or PbNb₂O₆(ii) a A second conductive layer 422, for example made of tungsten titanium alloy, platinum, yttrium or iridium oxide, is deposited on the actuation layer 421, forming a stack of layers.

The stack of layers thus obtained is patterned by photolithography and selective etching steps known to the person skilled in the art, such that the first conductive layer 420 forms the lower electrode region 415, the actuation layer 421 forms the plurality of first piezoelectric regions 416, and the second conductive layer 422 forms the plurality of upper electrode regions 417.

In particular, the plurality of upper electrode regions 417 and the plurality of first piezoelectric regions 416 are patterned in the first etching step, and thus have the same shape; the lower electrode region 415 is patterned in a separate etching step, for example, after patterning the plurality of upper electrode regions 417 and the first piezoelectric region 416, and includes a plurality of actuating parts 415A, a plurality of detecting parts 415B (a single detecting part is visible in fig. 16A), and a plurality of electrical connection parts 415C. In detail, each of the plurality of actuating portions 415A is substantially below the respective upper electrode region 417 and first piezoelectric region 416; each detection section 415B extends laterally with respect to the plurality of upper electrode regions 417 and the first piezoelectric region 416 only on one side, particularly rightward in fig. 16A; and each electrical connection portion 415C extends laterally with respect to the plurality of upper electrode regions 417 and the first piezoelectric region 416, particularly on both sides in fig. 16A.

Each actuation portion 415A, each first piezoelectric region 416, and each upper electrode region 417 of lower electrode region 415 form lower actuation electrode 81, piezoelectric actuation region 82, and upper actuation electrode 83, respectively, of each actuation structure 80.

In particular, fig. 16A and 16B show a first set of actuation structures 80A (at respective first lower forming regions 407), and fig. 16B shows two second sets of actuation structures 80B adjacent to the first set of actuation structures 80A in a radial direction of the actuator 50 of fig. 4A.

Subsequently, in fig. 17A and 17B, a piezoelectric layer 423, for example made of aluminum nitride (AlN) and having a thickness in the range of 0.5-3 μm, in particular 1 μm, is deposited on the front side of the wafer 400 and patterned by means of photolithography and selective etching, so as to form a plurality of second piezoelectric regions 430 (only one visible in fig. 17A) and a plurality of passivation regions 431.

The passivation regions 431 each surround the corresponding actuation structure 80, extend over a portion of the electrical connection portion 415C (fig. 17A) of the lower electrode region 415 and a portion of the second insulating layer 412 (fig. 17B), and form a plurality of first openings 432 each covering a corresponding upper electrode region 417.

The second piezoelectric regions 430 each extend over a respective detection portion 415B of the lower electrode region 415 at a distance from a respective passivation region 431.

Subsequently, in fig. 18A and 18B, a third conductive layer 424 made of, for example, molybdenum, platinum, yttrium or iridium oxide is deposited and patterned on the wafer 400 (on the front side of the wafer 400) to form first, second and third

conductive connection regions

435 and 437 and an upper detection electrode region 438, as described below.

In detail, first and second

conductive connection regions

435, 436 extend over first and second sets of

actuation structures

80A, 80B, respectively, within the plurality of first openings 432, are in contact with respective upper electrode regions 417, and extend over respective passivation regions 431.

Furthermore, in this embodiment, portions of the first and second

conductive connection regions

435, 436 extend to the sides of each actuation structure 80 (fig. 18B) on the second insulating layer 412, forming first and second

conductive tracks

89A, 89B, respectively, of the piezoelectric actuator 50 (fig. 2A). In particular, first conductive connection regions 435 interconnect a first set of actuation structures 80A and connect to a first set of upper electrode pads 90A, and second conductive connection regions 436 interconnect a second set of actuation structures 80B and connect to a second set of upper electrode pads 90B of piezoelectric actuator 50.

The upper detection electrode region 438 extends over each second piezoelectric region 430 and is in direct electrical contact with a third conductive connection region 437 corresponding to the third conductive track 95 of fig. 2A and extending over the second insulating layer 412 so as to be electrically connected to the corresponding detection pad 96 shown in fig. 2A.

In practice, each of the detection portions 415B of the lower electrode region 415, each of the second piezoelectric regions 430, and each of the upper detection electrode regions 438 form the lower detection electrode 92, the piezoelectric detection region 93, and the upper detection electrode 94 of each of the deformation sensors 91, respectively (here, one deformation sensor per each of the deformable rings 55, as described above).

Subsequently, in fig. 19A and 19B, the wafer 400 is selectively etched at the front side to form a trench 445 extending through the second insulating layer 412 and the structural layer 411. In particular, in fig. 19B, two trenches 445 can be seen, which extend to the left of the first set of actuation structures 80A, between the first and second sets of

actuation structures

80A, 80B, and to the right of the second set of actuation structures 80B.

In detail, the grooves 445 may be used to separate the deformable rings 55 from each other and from the movable center portion 56 (fig. 2A), as described below.

Further, referring again to fig. 19A and 19B, a second shaping layer 450 is deposited on the second surface 405B of the work substrate 405 and lithographically patterned to form a window 451 on the backside of the wafer 400, below the actuation structure 80, the deformation sensor 91 and the second lower shaping region 408.

Subsequently, in fig. 20A and 20B, the wafer 400 is selectively etched, starting from the second surface 405B of the work substrate 405, for example by dry chemical etching, removing the semiconductor material in the wafer at the window 451. Further, portions of the reinforcing layer 409 not covered by the first lower forming region 407 and the plurality of second lower forming regions 408 are removed. A working cavity 452 is thus formed corresponding to the cavity 52 of the piezoelectric actuator 50. Accordingly, the support portion 405 'corresponding to the substrate 57 of the piezoelectric actuator 50 remains from the work substrate 405, and the central portion 409' and the plurality of connecting portions 409 ″ remain from the reinforcing layer 409.

Then, using the second shaping layer 450 again as an etching mask, portions of the first lower shaping region 407, the plurality of second lower shaping regions 408, and the first insulating layer 410, which are on the sides of the central portion 409' of the reinforcing layer 409 and the plurality of connecting portions 409 ″, are removed. In this manner, trench 445 becomes a through trench, fig. 21B.

The second shaping layer 450 is then removed.

As shown in fig. 21A and 21B, the central portion 409 'of the reinforcement layer 409 and the remaining portion (denoted by 410') of the first insulating layer 410 form the shutter structure 86; the plurality of connection portions 409 "of the reinforcement layer 409 and the remaining portion (denoted by 410") of the first insulating layer 410 form the reinforcement structure 85. Furthermore, the structural layer 411 and the second insulating layer 412 on the sides of the working cavity 452 form the frame 53 together with the support portion 405' of the substrate 405, and the connecting

portions

60, 65, 70, 75, the movable central portion 56 and the deformable rings 55A-55C, identified with dashed lines in fig. 21B, are formed above the working cavity 452.

Finally, the wafer 400 is diced and after the usual electrical connection and packaging steps, each die forms the piezoelectric actuator 50 shown in fig. 2A.

In the process, the passivation region 431 is made of, for example, aluminum nitride. In fact, aluminum nitride has excellent electrical insulating properties and is chemically stable at high temperatures (even up to 1077 ℃) in oxidizing environments such as air and humidity. Thus, the passivation region 431 allows for passivation of the piezoelectric actuator 50 by depositing and patterning a single layer of material, thereby reducing the manufacturing steps and cost of the piezoelectric actuator 50 itself.

Finally, it is clear that modifications and variations can be made to the

piezoelectric actuators

50, 280 and to the manufacturing method described and illustrated herein without thereby departing from the scope of protection of the present disclosure, as defined in the annexed claims.

For example, the manufacturing method described herein may be adapted to manufacture the piezoelectric actuator 280 in a manner that will be apparent to a person skilled in the art, for example by forming only the lower shaping region, which may be used to obtain the stiffening structure 85, starting from the first shaping layer 406.

It will be apparent that the number of deformable rings, actuation structures and deformation sensors may be modified based on the particular application.

Further, the deformation sensor may be arranged on one or more deformable rings.

The layers forming deformable structure 54 may have different thicknesses depending on the deformation and the desired application.

Furthermore, the fluid channels may have different shapes.

For example, the biasing and measurement circuitry may be formed in the same die as the piezoelectric actuator.

The

control unit

220, 320 may be integrated in the

piezoelectric actuator

50, 280 or in the body 205, or formed by a separate device, for example an ASIC.

Further, the lower actuation electrode and the lower detection electrode may be formed of different conductive regions.

At least one embodiment of the present disclosure is directed to a MEMS actuator (50; 280) comprising: a body (51) surrounding a cavity (52); a deformable structure (54) suspended over the cavity and comprising a movable portion (56) and a plurality of deformable elements (55) arranged in succession to each other, which connect the movable portion to the body and each undergo deformation; and at least one set of a plurality of actuation structures (80A, 80B) supported by the deformable elements (55) and configured such that the translation of the movable portion is greater than the deformation of each deformable element (55), the actuation structures each comprising a respective first piezoelectric region (82).

In some embodiments, the deformable structure (54) is monolithic, substantially planar, and comprises a layer of semiconductor material (411), and wherein the movable portion (56) and the deformable element (55) are adjacent structures, having an upper surface that lies in one plane when at rest.

In some embodiments, the deformable element (55) has a substantially annular shape and surrounds the movable portion (56); the at least one set of multiple actuation structures is a first plurality of actuation structures (80A) configured to deform the deformable structure (54) and move the movable portion (56) in a first direction; the actuator further includes a second plurality of actuation structures (80B), actuation structures of the second plurality each including a respective piezoelectric region equal to the first piezoelectric region (83), the second plurality of actuation structures configured to deform the deformable structure (54) and move the movable portion (56) along a second direction.

In some embodiments, actuation structures of the first and second plurality of actuation structures (80A, 80B) are alternately arranged in succession in each deformable element (55), and wherein the deformable structure (54) comprises a plurality of arms (60, 65, 70, 75); a first arm (60) of the plurality of arms extending between the body (51) and the plurality of deformable elements; a second arm (65, 70) of the plurality of arms extends between adjacent deformable elements of the plurality of deformable elements; and a third arm (75) of the plurality of arms extends between the plurality of deformable elements and the movable portion (56), wherein the second arm (65, 70) couples an actuation structure of the first plurality of actuation structures on the deformable element to an actuation structure of the second plurality of actuation structures on an adjacent deformable element.

In some embodiments, the deformable structure further comprises a plurality of reinforcing structures (85) supported by the deformable element (55) on opposite sides with respect to actuation structures of the first plurality of actuation structures (80A), each reinforcing structure being arranged at a central portion of a respective actuation structure of the first plurality of actuation structures (80A) and being integral with a respective arm of the plurality of arms.

In some embodiments, the plurality of deformable elements (55) comprises a plurality of concentric rings, the actuating structures of the first and second plurality of actuating structures (80A, 80B) being formed by piezo strips extending annularly at a uniform distance from each other on each deformable element, each piezo strip defining a curved midline having a center (C), wherein each arm (60, 65, 70, 75) is radially aligned with a center of an actuation structure of the second plurality of actuation structures (80B) placed on a first deformable element of the plurality of deformable elements (55) and with a center of an actuation structure of the first plurality of actuation structures (80A) placed on a second deformable element of the plurality of deformable elements, the second deformable element is adjacent to and interior to the first deformable element.

In some embodiments, the movable portion (56) is formed by a platform, and the deformable structure (54) includes a shutter structure (86) formed by a region protruding from the movable portion (56).

In some embodiments, at least one detection structure (91) is supported by the deformable structure (54) and configured to detect deformation of the deformable structure, each detection structure comprising a respective second piezoelectric region (93).

In some embodiments, the actuation structures of the at least one plurality of actuation structures (80A, 80B) each comprise a respective first region stack comprising a lower actuation electrode (81), the first piezoelectric region (82) and an upper actuation electrode (83), and the at least one detection structure (91) comprises a respective second region stack comprising a lower detection electrode (92), the second piezoelectric region (93) and an upper detection electrode (94), wherein the lower detection electrode (92) of each detection structure (91) and the lower actuation electrode (81) of each actuation structure are formed by a single conductive region.

In some embodiments, a plurality of passivation regions (431), each passivation region surrounding a respective actuation structure of the at least one plurality of actuation structures (80A, 80B) and formed of the same material as the second piezoelectric region (93).

At least one embodiment of the present disclosure is directed to a flow regulator actuator 200; 250 of (a); 270) the method comprises the following steps: a channel body (205; 255); a fluid channel (210; 260) extending within the channel body and having an end portion; the MEMS actuator according to any of claims 8-10, wherein the movable portion (56) faces the end portion and is configured to change a passage cross-section arranged between the end portion and the movable portion; a control unit (220) coupled to the MEMS actuator and configured to provide a bias voltage to the at least one plurality of actuation structures (80A, 80B) and receive a detection voltage from the at least one detection structure (91).

In some embodiments, an end portion of the fluid channel is in contact with the movable portion (56) when at rest.

In some embodiments, an end portion of the fluid channel is at a distance from the movable portion (56) and forms a fluid passage (265; 285) with the movable portion when at rest.

At least one embodiment of the present disclosure is directed to a speaker (300) comprising: a housing (303) defining a cavity (305); a diaphragm (306) attached to the housing and suspended over the cavity; the MEMS actuator according to any one of claims 8-10, wherein the deformable structure (54) is coupled to the diaphragm and configured to cause deformation of the diaphragm; a control unit (320) coupled to the MEMS actuator and configured to provide a bias voltage to the at least one plurality of actuation structures (80A, 80B) and receive a detection voltage from the at least one detection structure (91).

At least one embodiment of the invention is directed to a method for actuating an embodiment of a MEMS actuator of the present disclosure, comprising the steps of: providing, by a control unit, a first bias voltage to the first plurality of actuation structures (80A) and no bias voltage to the second plurality of actuation structures (80B) so as to cause local deformation of a portion of the deformable element (55) supporting an actuation structure of the first plurality of actuation structures and translation of the movable portion (56) along a first direction; providing, by the control unit, a second bias voltage to the second plurality of actuation structures (80B) and no bias voltage to the first plurality of actuation structures (80A) so as to cause local deformation of a portion of the deformable element (55) and translation of the movable portion in a second direction opposite the first direction, the portion supporting an actuation structure of the second plurality of actuation structures.

At least one embodiment of the present disclosure is directed to a method of manufacturing an embodiment of a MEMS actuator of the present disclosure, comprising the steps of: forming a cavity (452, 52) in a working substrate (405) of a wafer (400) of semiconductor material to define a deformable structure (54) suspended over the cavity and a frame portion (53) surrounding the suspended structure; defining the deformable structure (54) to form a movable portion (56) and a plurality of deformable elements (55) arranged in succession to each other and connecting the movable portion to the frame portion and each subjected to deformation; and forming at least one plurality of actuating structures (80A, 80B) on the deformable element (55), the actuating structures each comprising a respective first piezoelectric region (82).

In some embodiments of methods of manufacturing embodiments of MEMS actuators of the present disclosure, may include forming a cavity in a working substrate, including the steps of: forming a plurality of shaped regions (407, 408) on a first surface (405A) of the working substrate (405); forming a reinforcing layer (409) and a structural layer (411) over the plurality of forming areas; forming a plurality of trenches (445) in the structural layer; and selectively removing the substrate from a second surface (405B) opposite the first surface as far as the structural layer, thereby forming the cavity, a plurality of reinforcing structures (85), the deformable structure (54) and a shutter structure (86) protruding from the structural layer towards the cavity.

In some embodiments of methods of manufacturing embodiments of MEMS actuators of the present disclosure, a step of forming at least one detection structure (91) over the deformable element, the at least one detection structure each comprising a respective second piezoelectric region (93) may be included.

In some embodiments of methods of fabricating embodiments of MEMS actuators of the present disclosure, may include forming at least one set of a plurality of actuation structures, including: forming a plurality of lower actuation electrode regions (81) from the first conductive layer (420); forming a plurality of first piezoelectric regions (82) from the first piezoelectric layer (421), each first piezoelectric region being on a respective lower actuation electrode region; and forming a plurality of upper actuation electrode regions (83) from the second conductive layer (422), each upper actuation electrode region being on a respective first piezoelectric region; and forming the at least one detection structure comprises: forming at least one lower detection electrode region (92) from the first conductive layer (420); forming, from the second piezoelectric layer (423), respective second piezoelectric regions (93) on the at least one lower detection electrode region; at least one upper sensing electrode area (94) is formed from the third conductive layer (424), each upper sensing electrode area being on a respective second piezoelectric area.

In some embodiments of methods of manufacturing embodiments of MEMS actuators of the present disclosure, may include forming respective second piezoelectric regions, including depositing a second piezoelectric layer (423) and patterning the second piezoelectric layer, forming respective second piezoelectric regions (93), and forming a plurality of passivation regions (431), each passivation region surrounding a respective actuation structure (80A, 80B) belonging to the at least one set of the plurality of actuation structures.

The various embodiments described above can be combined to provide further embodiments. Aspects of the embodiments can be modified, if necessary, to employ concepts of the various patents, applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.

Claims

1. A MEMS actuator comprising:

a body surrounding the cavity;

a deformable structure on the cavity, the deformable structure comprising:

a movable portion;

a plurality of deformable elements arranged in series connecting the movable portion to the body;

a plurality of arms coupling the movable portion, the plurality of deformable elements, and the body together; and

a plurality of reinforcing structures, a respective one of the plurality of reinforcing structures being integral with a respective one of the plurality of arms;

at least one plurality of actuation structures on the deformable element.

2. The actuator of claim 1, wherein:

the at least one set of a plurality of actuation structures configured to cause a translation of the movable portion to be greater than a deformation of each of the plurality of deformable elements, each of the actuation structures comprising a respective first piezoelectric region;

the deformable structure is monolithic, substantially planar, and comprises a layer of semiconductor material;

the movable portion is adjacent to the plurality of deformable elements; and

the movable portion includes a first surface and each of the plurality of deformable elements includes a second surface, and the first surface and the second surface are aligned in a plane when the movable portion and the plurality of deformable portions are at rest.

3. The actuator of claim 1, wherein:

the deformable element has a generally annular shape and surrounds the movable portion;

the at least one set of multiple actuation structures is a first plurality of actuation structures configured to deform the deformable structure and move the movable portion in a first direction; and

the actuator further includes a second plurality of actuation structures, each of the actuation structures in the second plurality of actuation structures including a second piezoelectric region, the second plurality of actuation structures configured to deform the deformable structure and move the movable portion in a second direction.

4. The actuator of claim 3, wherein:

actuating structures of the first and second pluralities of actuating structures are successively alternately arranged on each of the deformable elements; and

the plurality of arms includes:

a first arm extending between the body and one of the plurality of deformable elements;

a second arm extending between adjacent ones of the plurality of deformable elements, the second arm coupling one of the first plurality of actuation structures on one of the plurality of deformable elements to one of the second plurality of actuation structures on an adjacent one of the plurality of deformable elements; and

a third arm extending between one of the plurality of deformable elements and the movable portion.

5. The actuator of claim 4, wherein the plurality of reinforcing structures are supported by the deformable element on opposite sides relative to actuation structures of the first plurality of actuation structures, each reinforcing structure being disposed at a central portion of a respective actuation structure of the first plurality of actuation structures.

6. The actuator of claim 4, wherein:

the plurality of deformable elements comprises a plurality of concentric rings; and

actuating structures of the first and second pluralities of actuating structures are formed by piezo strips extending annularly at a uniform distance from each other on each deformable element, each piezo strip defining a curved midline having a center; and

each arm of the plurality of arms is radially aligned with a center of one of the second plurality of actuation structures disposed on a first deformable element of the plurality of deformable elements and radially aligned with a center of one of the first plurality of actuation structures disposed on a second deformable element of the plurality of deformable elements adjacent to and surrounded by the first deformable element.

7. The actuator of claim 1, wherein:

the movable portion is a platform on and overlapping the cavity; and

the deformable structure comprises a shutter structure having a region protruding from the movable portion.

8. The actuator of claim 1, further comprising at least one detection structure on the deformable structure, and wherein the at least one detection structure is configured to detect the deformation of the deformable structure, and the at least one detection structure comprises a respective second piezoelectric region.

9. The actuator of claim 8, wherein:

each actuation structure of the at least one plurality of actuation structures comprises a respective first region stack comprising a lower actuation electrode, a first piezoelectric region, and an upper actuation electrode; and

the at least one detection structure includes a respective second area stack including a lower detection electrode, a second piezoelectric area, and an upper detection electrode.

10. The actuator of claim 9, further comprising a plurality of passivation regions, each passivation region surrounding a respective actuation structure of the at least one plurality of actuation structures.

11. A flow regulator, comprising:

a channel body;

a fluid channel in the channel body and having an end portion;

a passage section adjacent to the end portion;

a microelectromechanical system (MEMS) actuator having a cavity, a body surrounding the cavity, and a deformable structure aligned with the cavity, the deformable structure comprising:

a movable portion having a surface facing the end portion and configured to change the passage cross-section arranged between the end portion and the movable portion;

a plurality of deformable elements surrounding the movable portion;

at least one plurality of actuating structures on the plurality of deformable elements; and

at least one detection structure on the plurality of deformable elements;

a control unit coupled to the MEMS actuator, the control unit configured to provide a bias voltage to the at least one plurality of actuation structures and receive a detection voltage from the at least one detection structure.

12. The flow regulator of claim 11, wherein the end portion of the fluid channel is in contact with the movable portion when the movable portion is in a rest position.

13. A flow regulator according to claim 11, wherein the end portion of the fluid channel is spaced from the movable portion by a fluid passage when the movable portion is in a rest position.

14. A loudspeaker, comprising:

a housing defining a first cavity;

a diaphragm attached to the housing and over the cavity;

a MEMS actuator comprising a second cavity, a body surrounding the second cavity, and a deformable structure coupled to the diaphragm and configured to cause deformation of the diaphragm, the deformable structure comprising:

a movable portion coupled to the diaphragm;

a plurality of deformable elements surrounding the movable portion;

at least one detection structure on the plurality of deformable elements;

a control unit coupled to the MEMS actuator and configured to provide a bias voltage to the at least one plurality of actuation structures and receive a detection voltage from the at least one detection structure.

15. The loudspeaker of claim 14, wherein the plurality of deformable elements are arranged in series, surrounding the movable portion, and connecting the movable portion to the body.

16. A method of manufacturing a MEMS actuator, comprising:

forming at least one plurality of actuation structures on a first surface of a substrate opposite a second surface of the substrate; and

forming the deformable structure includes:

forming a movable portion, forming a plurality of deformable elements arranged consecutively with respect to each other and connecting one of the plurality of deformable elements to the movable portion, and forming a frame and connecting the frame to one of the plurality of deformable elements by forming a cavity extending into the second surface of the substrate.

17. The method of manufacturing of claim 16, wherein forming the cavity further comprises:

forming a plurality of shaped regions on the first surface of the substrate;

forming a reinforcing layer and a structural layer over the plurality of forming areas;

forming a plurality of trenches in the structural layer; and

selectively removing a portion extending from the second surface of the substrate to the structural layer, wherein selectively removing the portion forms the cavity, a plurality of reinforcing structures, the deformable structure, and a shutter structure protruding from the structural layer towards the cavity.

18. The method of manufacturing of claim 16, further comprising forming at least one detection structure on the deformable element, the at least one detection structure comprising a respective second piezoelectric region.

19. The manufacturing method according to claim 18, wherein:

forming the at least one plurality of actuation structures comprises:

forming a plurality of lower actuation electrode regions from the first conductive layer;

forming a plurality of first piezoelectric regions from a first piezoelectric layer, the plurality of first piezoelectric regions being on a respective one of the lower actuator electrode regions; and

forming a plurality of upper actuator electrode regions from a second electrically conductive layer, the plurality of upper actuator electrode regions being on respective ones of the first piezoelectric regions; and

forming at least one detection structure comprises:

forming a lower detection electrode region from the first conductive layer;

forming respective second piezoelectric regions from a second piezoelectric layer, the second piezoelectric regions being on the lower detection electrode region; and

forming upper detection electrode regions from a third conductive layer, the upper detection electrode regions being on the respective second piezoelectric regions.

20. The method of manufacturing of claim 19, wherein forming each actuation structure of the plurality of actuation structures comprises:

depositing and patterning the second piezoelectric layer to form the respective second piezoelectric regions; and

surrounding a respective actuation structure of the at least one plurality of actuation structures with a respective passivation region by forming the respective passivation region on a corresponding one of the respective second piezoelectric regions.