Piezoelectric actuator with deformation sensor and manufacturing method thereof

Abstract

The MEMS actuator is formed by the following components: a substrate surrounding a cavity; a deformable structure suspended on the cavity; an actuating structure formed by a first piezoelectric region of a first piezoelectric material, supported by the deformable structure and configured to cause deformation of the deformable structure; and a detection structure formed by a second piezoelectric region of a second piezoelectric material, supported by the deformable structure and configured to detect deformation of the deformable structure.

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric actuator with a deformation sensor and a method for manufacturing the same. In particular, reference will be made hereinafter to a piezoelectric actuator made using thin piezoelectric film MEMS (Micro Electro Mechanical System) technology. Background Art

[0002] As is known, a MEMS actuator is an electronic device typically made from a wafer of semiconductor material, such as silicon, and capable of causing deformation of a movable element, such as a membrane or a cantilever.

[0003] MEMS actuators can operate according to various actuation principles, including electrostatic, electromagnetic, and piezoelectric. Specifically, MEMS actuators operating according to the piezoelectric principle are characterized by high energy efficiency and high deformation precision of the movable element; for this reason, they are increasingly popular. In particular, thin piezoelectric film MEMS actuators are currently used to implement microfluidic valves, camera devices for focusing, and print cartridges.

[0004] Figure 1 There is shown a cross section of a known piezoelectric MEMS actuator, hereinafter also referred to as actuator 10. The actuator 10 comprises an active actuating structure 15 and a deformable structure 16 suspended over a cavity 12 formed in a body 11 of semiconductor material, such as silicon.

[0005] The deformable structure 16 is arranged below the active actuation structure 15 and is formed of a movable region 17 of a semiconductor material, such as polysilicon, and an insulating region 18, such as silicon oxide. The insulating region 18 is arranged above the movable region 17 to electrically insulate it from the active actuation structure 15.

[0006] The active actuating structure 15 is formed by a piezoelectric region 20 , a lower electrode 21 and an upper electrode 22 .

[0007] The lower electrode 21 is made of a metal material such as platinum, and extends on the deformable structure 16 and contacts the insulating region 18 .

[0008] The piezoelectric region 20 is formed of a piezoelectric material (eg, PZT (lead zirconate titanate), BaTiO 3 , KNN (potassium sodium niobate), PbTiO 2 , or PbNb 2 O 6 ).

[0009] For example, the piezoelectric region 20 has a thickness of several micrometers, for example in the range of 1 μm to 3 μm, and extends on the lower electrode 21 .

[0010] The upper electrode 22 is made of a metal material (eg, titanium-tungsten alloy) and extends over the piezoelectric region 20 .

[0011] The actuator 10 further comprises a passivation region 25 and an upper connection region 26 .

[0012] The passivation region 25 is here formed by a stack of insulating layers, for example, three insulating layers, including: a first insulating layer 25A, for example, aluminum oxide, arranged on the active actuating structure 15 and the deformable structure 16; a second insulating layer 25B, for example, undoped silicon glass (USG), arranged on the first insulating layer 25A; and a third insulating layer 25C, for example, silicon nitride.

[0013] The upper connection region 26 is formed of a conductive layer (e.g., aluminum, AlCu, copper, or gold) that extends over at least a portion of the second insulating layer 25B and forms a protrusion that extends through the first insulating layer 25A and the second insulating layer 25A and is in direct electrical contact with the upper electrode 22. The upper connection region 26 allows the upper electrode 22 to be electrically connected to a contact pad (not shown) for biasing. Similar to the upper connection region 26, the lower connection region (not shown) allows the lower electrode 21 to be biased to a suitable potential, such as ground.

[0014] The third insulating layer 25C extends over the second insulating layer 25B and the upper connection region 26 .

[0015] The passivation region 25 allows the actuator 10 to be electrically isolated and protected from external contaminants.

[0016] In use, application of a bias voltage between the lower electrode 21 and the upper electrode 22 causes deformation of the piezoelectric region 20 and hence deformation of the deformable structure 16 integral therewith.

[0017] In some applications, it is important to monitor or control the degree of deformation of the deformable structure 16 to detect changes or verify that the deformation meets the requirements. In particular, to control the deformation, closed-loop control systems are frequently provided, allowing the deformation of the deformable structure 16 to be controlled in real time.

[0018] Thus, the actuator 10 may be provided with a deformation sensor of the deformable structure 16, for example made using a piezoelectric structure formed from the same layer forming the piezoelectric area 20 or using a piezoresistive structure. However, these solutions are not optimal.

[0019] In reality, PZT is a ferroelectric material characterized by hysteresis and a high relative dielectric constant. As a result, it generates a low detection voltage in the presence of mechanical stress, making stress measurements noisy and inaccurate.

[0020] A piezoresistor is a device that undergoes a change in resistance in the presence of mechanical stress and thus allows the deformation of a deformable structure to be detected by voltage or current detection. However, this detection is active and therefore involves the passage of an electric current with high energy consumption. Summary of the Invention

[0021] The present disclosure relates to a microelectromechanical structure (MEMS) actuator having a substrate surrounding a cavity. The MEMS actuator includes a deformable structure suspended above the cavity. The actuating structure includes a first piezoelectric region of a first piezoelectric material, the first piezoelectric region being supported by the deformable structure and configured to cause deformation of the deformable structure. The detecting structure includes a second piezoelectric region of a second piezoelectric material, the second piezoelectric region being supported by the deformable structure and configured to detect deformation of the deformable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] For a better understanding of the present disclosure, embodiments thereof will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

[0023] Figure 1 is a cross section of a known piezoelectric MEMS actuator;

[0024] Figures 2 to 5A shows cross sections of the present piezoelectric MEMS actuator in successive manufacturing steps;

[0025] Figure 5B Shown in Figure 5A A top view of the present piezoelectric MEMS actuator during the manufacturing steps;

[0026] Figures 6 to 10 shows cross sections of the present piezoelectric MEMS actuator in successive manufacturing steps;

[0027] Figure 11 shows a cross-section of an embodiment of an actuation system incorporating the present piezoelectric MEMS actuator;

[0028] Figure 12 shows a cross section of an actuation system incorporating the present piezoelectric MEMS actuator according to another embodiment;

[0029] Figure 13 shows perspective views of different embodiments of the present piezoelectric MEMS actuator;

[0030] Figure 14 Shown along Figure 13 The section line XIV-XIV is taken Figure 13 Cross section of a piezoelectric MEMS actuator;

[0031] Figure 15 Shown along Figure 13 The section line XV-XV is taken Figure 13 Cross section of a piezoelectric MEMS actuator;

[0032] Figure 16shows top plan views of various embodiments of the present piezoelectric MEMS actuator;

[0033] Figure 17 shows top plan views of various embodiments of the present piezoelectric MEMS actuator;

[0034] Figure 18 shows top plan views of various embodiments of the present piezoelectric MEMS actuator;

[0035] Figure 19 shows cross sections of different embodiments of the present piezoelectric MEMS actuator;

[0036] Figures 20 to 27 Shown Figure 19 Cross-section of a piezoelectric MEMS actuator in successive fabrication steps;

[0037] Figure 28 Cross-sections of different embodiments of the present piezoelectric MEMS actuator are shown.

[0038] Figure 29 and Figure 30 Shown Figure 28 A cross section of a piezoelectric MEMS actuator at an intermediate manufacturing step; and

[0039] Figure 31 A cross section of another embodiment of the present piezoelectric MEMS actuator is shown. DETAILED DESCRIPTION

[0040] Figure 2 A cross section of a wafer 45 that has undergone a first processing step is shown. In detail, the wafer 45 comprises a substrate 50 of a semiconductor material, such as silicon, having a first surface 50A and a second surface 50B. A first shaped layer 51 of, for example, deposited tetraethyl orthosilicate (TEOS) extends over the first surface 50A of the substrate 50, the first shaped layer 51 having a thickness of, for example, at least 1 μm, here 1 μm.

[0041] Then, Figure 3 The first shaping layer 51 is patterned by selective etching in a manner known to those skilled in the art so as to form a lower shaping region 52 which can be used for the continuous formation of the constriction structure, as will be described in detail below.

[0042] Furthermore, a reinforcement layer 53 of a semiconductor material, such as polycrystalline silicon, is formed (e.g., epitaxially) on the first surface 50A of the substrate 50 and on the lower shaping region 52. The reinforcement layer 53 is then chemically and mechanically polished to form a flat upper surface. The thickness of the reinforcement layer 53 is greater than that of the first shaping layer 51. In this embodiment, the thickness of the reinforcement layer 53 is 25 μm.

[0043] Subsequently, a first insulating layer 54 of, for example, tetraethyl orthosilicate (TEOS) is deposited on the reinforcement layer 53 . The thickness of the first insulating layer 54 is comparable to the thickness of the first shaping layer 51 , such as at least 1 μm, here 1 μm.

[0044] exist Figure 4 In the embodiment, a structural layer 55 of a semiconductor material such as polysilicon is deposited on the first insulating layer 54. The structural layer 55 has a thickness selected based on the required mechanical properties, for example, in this embodiment it has a thickness of 10 μm and can be in the range of 8 μm to 18 μm.

[0045] A second insulating layer 56 , for example of tetraethyl orthosilicate (TEOS), which has a thickness of 0.5 μm in this case, is deposited on the structural layer 55 . The second insulating layer 56 is thinner than the structural layer 55 .

[0046] Then, Figure 5A A first conductive layer 70, such as platinum, is deposited on the second insulating layer 56. An actuation layer 71 of an amorphous or bimorphous piezoelectric material with a high relative permittivity (e.g., greater than 100) such as lead zirconate titanate (PZT), BaTiO3, KNN (potassium sodium niobate), PbTiO2, or PbNb2O6 is deposited on the first conductive layer 70. The actuation layer 71 has a thickness in the range of 1 μm to 3 μm, in particular 2 μm. A second conductive layer 72, such as tungsten-titanium alloy, platinum, yttrium, or iridium oxide, is deposited on the actuation layer 71 to form a layer stack.

[0047] Alternatively, the actuation layer 71 may be formed of a ceramic piezoelectric material.

[0048] The stack of layers thus obtained is patterned by photolithography and selective etching steps known to those skilled in the art, so that the first conductive layer 70 forms the lower electrode region 60 , the actuation layer 71 forms the piezoelectric actuation region 61 and the second conductive layer 72 forms the upper electrode region 62 .

[0049] In particular, as in Figure 5B As can be seen in the top plan view of the upper electrode region 62 and the piezoelectric actuation region 61 below (in Figure 5B The lower electrode region 60 (not visible in the figure) is patterned in a first etching step and thus has the same shape; the lower electrode region 60 is patterned in a separate etching step, for example, after the upper electrode 62 and the piezoelectric actuation region 61 are patterned, and includes an actuating portion 60A, a detecting portion 60B, and a connecting portion 60C. Specifically, the actuating portion 60A is approximately below the upper electrode 62 and the piezoelectric actuation region 61; the detecting portion 60B and the connecting portion 60C extend transversely to the upper electrode 62 and the piezoelectric actuation region 61.

[0050] The actuating portion 60A of the lower electrode region 60 , the piezoelectric actuating region 61 , and the upper electrode region 62 form an active actuating structure 65 .

[0051] Then, Figure 6 A piezoelectric layer 73, such as aluminum nitride (AlN), is deposited on the first surface 50A of the substrate 50, the piezoelectric layer 73 having a thickness in the range of 0.5 μm to 3 μm, in particular 1 μm, and the piezoelectric layer 73 is patterned by photolithography and selective etching to form a piezoelectric detection region 80 and a passivation region 81.

[0052] The passivation region 81 surrounds the active actuation structure 65 and is at least on a first side of the active actuation structure 65 (at Figure 6 The first insulating layer 56 extends over a portion of the second insulating layer 56 (on the left side in FIG), and forms a first opening 82 above the upper electrode region 62.

[0053] The piezoelectric detection region 80 extends over the detection portion 60B at a distance from the passivation region 81, here on the second side of the active actuation structure 65 (at Figure 6 on the right side of the ).

[0054] exist Figure 7 In the process, a third conductive layer 74 of, for example, molybdenum, platinum, yttrium or iridium oxide is deposited from above the wafer 45 .

[0055] Then, Figure 8 The third conductive layer 74 is patterned in a manner known to those skilled in the art so as to form a conductive connection region 85 and an upper detection electrode region 86 .

[0056] The conductive connection region 85 extends over the active actuating structure 65 , making contact with the upper electrode region 62 , and extends over the passivation region 81 and connects the upper electrode region 62 to a contact pad (not shown here).

[0057] An upper detection electrode region 86 extends over the piezoelectric detection region 80 and the second insulating layer 56 on a second side of the active actuation structure 65 .

[0058] The detection portion 60B of the lower electrode region 60 , the piezoelectric detection region 80 , and the upper detection electrode region 86 form a detection structure 90 .

[0059] exist Figure 9 In FIG. 4 , a second shaping layer 96 is deposited on the second surface 50B of the substrate 50 and is photolithographically patterned to form windows 97 on the backside of the wafer 45 below the active actuation structure 65 and the detection structure 90 , as discussed below.

[0060] A selective etch (e.g., dry chemical etch) is then performed starting from the second surface 50B of the substrate 50, removing the semiconductor material thereof at the windows 97 and at the portions of the stiffening layer 53 not covered by the lower formed region 52, and forming the cavity 100. Thus, the bearing portion 50' remains from the substrate 50, and the portion (indicated by 53') below the active actuation structure 65 remains from the stiffening layer 53.

[0061] exist Figure 10 In the embodiment shown in FIG. 5 , again using the second shaping layer 96 as an etching mask, the lower shaping region 52 and the portion of the first insulating layer 54 on the side of the portion 53 ′ of the reinforcement layer 53 are removed.

[0062] The portion 53 ′ of the reinforcement layer 53 and the remaining portion (indicated by 54 ′) of the first insulating layer 54 form the contracted structure 101 ; the structural layer 55 and the second insulating layer 56 now suspended over the cavity 100 form the deformable structure 105 .

[0063] In fact, here, the deformable structure 105 is a suspended membrane.

[0064] Finally, the second shaping layer 96 is removed, the wafer 45 is diced, and each die forms a piezoelectric MEMS actuator 150 after conventional electrical connection and packaging steps.

[0065] The piezoelectric MEMS actuator 150 thus obtained includes a lower electrode 110 (including Figure 5B an actuating portion 60A, a detecting portion 60B and a connecting portion 60C of the lower electrode region 60), an upper actuating electrode 111 (corresponding to the upper electrode region 62) and an upper detecting electrode 112 (corresponding to the upper detecting electrode region 86).

[0066] In use, a bias voltage applied in a known manner between the upper actuation electrode 111 and the lower electrode 110 causes deformation of the active actuation structure 65. Consequently, the deformable structure 105, which is integral with the active actuation structure 65 and suspended on the cavity 100, deforms. The deformation of the deformable structure 105 generates mechanical stress in the detection structure 90, which is arranged in a peripheral portion of the deformable structure 105 adjacent to the bearing portion 50', which peripheral portion represents a confinement area for the deformable structure 105.

[0067] In this way, in the presence of mechanical stress, the piezoelectric sensing region 80 generates a sensing voltage between the lower electrode 110 and the upper sensing electrode 112, which sensing voltage can be measured in a known manner and converted into a deformation value of the deformable structure 105. Thus, measurement of the sensing voltage allows the state of the piezoelectric MEMS actuator 150 to be controlled in real time by a closed-loop control system.

[0068] The measurement of the detection voltage is passive detection, ie, it does not require the passage of current and is therefore advantageous from a power point of view.

[0069] In order to obtain good detection sensitivity, it is desirable that the piezoelectric detection region 80 has linear, non-hysteresis characteristics and that the ratio between the detection voltage and the mechanical stress is high.

[0070] Therefore, piezoelectric materials having a low relative dielectric constant (eg, approximately less than or equal to 10) and a loss tangent, for example, less than 0.05 (particularly equal to 0.002) are preferred.

[0071] Alternatively, the piezoelectric material forming the piezoelectric detection region 80 may be a ceramic material.

[0072] The piezoelectric detection region 80 is here formed of aluminum nitride (AlN), which has a linear and high ratio dependence of the detection voltage / mechanical stress. However, other materials such as zinc oxide and polyvinylidene fluoride (PVDF) can be used.

[0073] Furthermore, passivation region 81 is also formed from aluminum nitride. This material has excellent electrical insulating properties and maintains chemical stability at high temperatures (even up to 1077°C) even in oxidizing environments such as air and moisture. Consequently, forming passivation region 81 allows piezoelectric MEMS actuator 150 to be passivated by depositing and patterning a single layer of material, thereby reducing the number of manufacturing steps and costs associated with piezoelectric MEMS actuator 150 itself.

[0074] Piezoelectric MEMS actuator 150 may be used in devices such as autofocus for cameras, microprojectors, and microfluidic valves.

[0075] Figure 11 The use of a piezoelectric MEMS actuator 150 is shown, for example, within a microfluidic valve 300 .

[0076] In detail, the microfluidic valve 300 includes a body 290 and a piezoelectric MEMS actuator 150 coupled to the body 290. The microfluidic valve 300 accommodates a fluid channel 310 having an inlet port IN and an outlet port OUT.

[0077] Specifically, the main body 290 includes a first channel body and a second channel body 301, 302. Typically, the first channel body and the second channel body 301, 302 are made of a semiconductor material such as silicon. Figure 11 are processed and joined together in invisible ways.

[0078] For example, the first channel body 301 has a substantially parallelepiped shape with first and second surfaces 301A, 301B. The first channel body 301 contains a horizontal channel portion 309 extending along the second surface 301B of the first channel body 301 and closed at the bottom by the second channel body 302.

[0079] A through opening 303 extends through the first channel body 301 between the first surface 301A and the horizontal channel portion 309 .

[0080] In this embodiment, second channel body 302 has a substantially parallelepiped shape with an upper surface 302A joined to second surface 301B of first channel body 301. Second channel body 302 has a protrusion 305 extending from upper surface 302A within through opening 303 of first channel body 301.

[0081] The bearing portion 50' of the piezoelectric MEMS actuator 150 is here bonded to the first surface 301A of the first channel body 301, so that the constriction 101 faces one end of the protrusion 305 at a certain distance and delimits therewith a passage 315 of the fluid channel 310. In practice, the protrusion 305 and the constriction 101 form the constriction 312 of the microfluidic valve 300.

[0082] Thus, the passage 315 , the through-opening 303 and the horizontal channel portion 309 form a fluid channel 310 .

[0083] In addition, the microfluidic valve 300 includes a control unit 320, which is coupled to the piezoelectric MEMS actuator 150 via contact pads not shown here, in particular to the active actuation structure 65 and the detection structure 90, for the exchange of signals and electrical quantities used to control the microfluidic valve 300 itself.

[0084] To this end, the control unit 320 includes: input ports / output ports 321 and 322 for receiving control signals and transmitting detection signals to the outside (e.g., to a user); a control stage 323 (e.g., a CPU) for processing the signals provided to the control; and a driver stage 324 for controlling the piezoelectric MEMS actuator 150. The control stage 323 may, for example, store a conversion table between a nominal flow rate (required) and an actuation bias voltage value to be provided to the piezoelectric MEMS actuator 150.

[0085] In use, a user can set a nominal flow rate value for the fluid in the fluid channel 310 via the input port 321. Based on the stored table, the control unit 320 applies a bias voltage of an appropriate value to the active actuation structure 65, causing it to deform. The deformable structure 105 then deforms based on the value of the bias voltage, moving the constriction structure 101 closer to the end of the protrusion 305 of the second channel body 302, thereby setting the passage section 315 of the fluid channel 310 and the flow rate.

[0086] At the same time and as explained above, the mechanical stress caused by the deformation of the deformable structure 105 generates a detection voltage in the detection structure 90 which is provided to the control unit 320 .

[0087] The control unit 320 compares the value of the detection voltage or a quantity related thereto with an appropriate calibration parameter corresponding to the flow value and verifies in real time that the fluid flow rate complies with the nominal value. If not, the control unit 320 can modify the bias voltage applied to the active actuation structure 65 to bring the flow rate into compliance with the nominal value.

[0088] Figure 12 Another embodiment of the present piezoelectric MEMS actuator is shown, hereinafter indicated by reference numeral 350, and is used within a microfluidic valve, here indicated by reference numeral 400. Piezoelectric MEMS actuator 350 and microfluidic valve 400 have similar basic structures and functions as piezoelectric MEMS actuator 150 and microfluidic valve 300, respectively; therefore, common elements are indicated by the same reference numerals.

[0089] In particular, here, the fluid channel 310 and the piezoelectric MEMS actuator 350 are formed within a body 390 of a semiconductor material, such as silicon.

[0090] In detail, here too, the active actuation structure 65 and the detection structure 90 are arranged on the deformable structure 105 .

[0091] Here, the deformable structure 105 is suspended on the cavity 410, and both the deformable structure 105 and the cavity 410 are formed by the body 390. In fact, here the through-opening no longer exists, and the protrusion 305 extends within the cavity 410. Thus, here, the constriction 312 is defined by the protrusion 305 and the deformable structure 105, which also forms the constriction structure of the piezoelectric MEMS actuator 350.

[0092] Reference below Figures 13 to 15 Another embodiment of the piezoelectric MEMS actuator will be described.

[0093] In detail, Figures 13 to 15A piezoelectric MEMS actuator 500 is shown formed in a die 505, comprising a bearing portion 510 surrounding a cavity 515 and a deformable structure 520 fixed to the bearing portion 510 and suspended on the cavity 515. Here, the piezoelectric MEMS actuator 500 has cylindrical symmetry; therefore, for clarity, the Figure 13 Only one quarter of the piezoelectric MEMS actuator 500 is shown.

[0094] Die 505 has a first surface 505A and a second surface 505B, and is formed from a multilayer structure 523. Here, multilayer structure 523 includes a base 525 of semiconductor material bounded downwardly by: second surface 505B of die 505; a first insulating layer 528, such as an oxide; a structural layer 530 of semiconductor material overlying first insulating layer 528; and a second insulating layer 533, such as an oxide, overlying structural layer 530 and bounded upwardly by first surface 505A of die 505.

[0095] The base 525 and the first insulating layer 528 have a cylindrical shape, surround the cavity 515 and form the bearing portion 510 .

[0096] The structural layer 530 has a thickness of, for example, between 3 μm and 150 μm, and has a first portion 530A extending on the first insulating layer 528 and a second portion 530B extending on the cavity 515 .

[0097] The cavity 515 , which is cylindrical here, has a diameter of, for example, between 20 μm and 3000 μm and extends from the second surface 505B of the die 505 through the die 505 as far as the second portion 530B of the structure layer 530 .

[0098] The structural layer 530 and the second insulating layer 533 form a deformable structure 520 having a movable portion 520A and a fixed portion 520B. The movable portion 520A defines a cavity 515 at the top and is thus suspended above the cavity 515. The fixed portion 520B is covered on the first insulating layer 528 and is thus fixed to the bearing portion 510.

[0099] The deformable structure 520 is much thinner than the bearing portion 510, and its thickness is much smaller than the diameter of the cavity 515. Thus, the deformable structure 520 is a suspended membrane.

[0100] The MEMS piezoelectric actuator 500 further includes an actuation structure 535 (corresponding to the active actuation structure 65 of the piezoelectric MEMS actuator 150 ) and a detection structure 536 , which are supported by the deformable structure 520 , in particular by the movable portion 520A.

[0101] The actuation structure 535 is arranged on the second insulating layer 533 at the center of the movable portion 520A of the deformable structure 520 and here has a cylindrical shape with a diameter smaller than the diameter of the cavity 515 (eg, approximately 70% of the diameter of the cavity 515 ).

[0102] The actuation structure 535 is formed by a corresponding stack including: a lower actuation electrode 537 made of a conductive material, such as platinum, extending over the second insulating layer 533; a piezoelectric actuation region 539 made of an amorphous or bimorphous piezoelectric material with a high relative dielectric constant (e.g., greater than 100) such as lead zirconate titanate (PZT), BaTiO3, KNN (potassium sodium niobate), PbTiO2, or PbNb2O6, having a thickness in the range of 1 μm to 5 μm, in particular 2 μm, extending over the lower actuation electrode 537; and an upper actuation electrode 541 made of a conductive material, extending over the piezoelectric actuation region 539. Here, the upper actuation electrode is formed by a first conductive layer 541A, such as tungsten-titanium alloy, platinum, yttrium, or iridium oxide, and a second conductive layer 541B, such as molybdenum, tungsten-titanium alloy, platinum, yttrium, or iridium oxide.

[0103] The detection structure 536 extends on the second insulating layer 533 at an edge of the movable portion 520A of the deformable structure 520 near the fixed portion 520B.

[0104] The detection structure 536 here includes a plurality of detection units 543 , which are arranged continuously and separately from each other along the outer circumference of the movable portion 520A of the deformable structure 520 .

[0105] Each detection unit 543 is a curved strip and is formed from a separate stack comprising a lower detection electrode 545 of conductive material, a piezoelectric detection region 547, and an upper detection electrode 549 of conductive material. Lower detection electrode 545 is, for example, platinum and extends over second insulating layer 533. Piezoelectric detection region 547 is made of piezoelectric material having a low relative permittivity, for example, less than or equal to 10, a loss tangent, for example, less than 0.05 (particularly equal to 0.002), and a thickness in the range of 0.5 μm to 3 μm (particularly 1 μm), and extends over second insulating layer 533 and lower detection electrode 545 on the sides of lower detection electrode 545. Upper detection electrode 549 is, for example, molybdenum, a tungsten-titanium alloy, platinum, yttrium, or iridium oxide and covers piezoelectric detection region 547.

[0106] Similar to the piezoelectric MEMS actuators 150 , 350 , the piezoelectric detection region 547 is here aluminum nitride (AlN), has linear and non-hysteretic characteristics, and has a high detection voltage / mechanical stress ratio.

[0107] However, the piezoelectric detection region 547 may be a different piezoelectric material, such as zinc oxide, polyvinylidene fluoride (PVDF), or a ceramic piezoelectric material.

[0108] Here, as Figure 15 As can be seen in FIG, the detection cells 543 are configured such that the upper detection electrode 549 of each detection cell 543 is in direct electrical contact with the lower detection electrode 545 of an adjacent detection cell 543. In other words, the detection cells 543 are electrically connected to each other in series.

[0109] The piezoelectric MEMS actuator 500 also includes a passivation region 550 ( Figure 14 ). Similar to the passivation region 81 of the piezoelectric MEMS actuator 150 , 350 , the passivation region 550 is here formed from the same piezoelectric material forming the piezoelectric detection region 547 , thus bringing the same advantages already described for the piezoelectric MEMS actuator 150 , 350 .

[0110] The piezoelectric MEMS actuator 500 also includes metallic tracks (not shown here) that allow the actuation structure 535 to be connected to a drive circuit for its biasing, and the detection structure 536 to be connected to a sensing circuit.

[0111] The drive circuitry and the sense circuitry may be integrated in die 505 , or in one or more separate dies, and may include one or more control units.

[0112] The lower detection electrode 545 (not shown here) of the first detection cell in the series of detection cells 543 is connected to a reference voltage (e.g., ground), and the upper detection electrode 549 (also not shown) of the last detection cell in the series of detection cells 543 is connected to a voltage readout device.

[0113] Thus, the piezoelectric MEMS actuator 500 may be used as a piezoelectric micromachined ultrasonic transducer (PMUT) to obtain, for example, a time-of-flight measurement device to, for example, measure the distance between the deformable structure 520 and an object or obstacle placed near the piezoelectric MEMS actuator 500 .

[0114] In use, the drive circuit applies a bias voltage between the upper actuation electrode 541 and the lower actuation electrode 537 so as to cause, in a manner known per se, deformation of the piezoelectric actuation region 539 and the movable portion 520A of the deformable structure 520. In particular, the bias voltage may have a high frequency, for example equal to the resonant frequency of the deformable structure 520, for example above 20 kHz.

[0115] Similar to what has been described above with respect to the piezoelectric actuators 150, 350, deformation of the deformable structure 520 generates mechanical stress in the detection structure 536. As described above, the detection structure 536 is arranged in a peripheral portion of the movable portion 520A of the deformable structure 520, adjacent to the fixed portion 520B of the deformable structure 520, which is integral with the bearing portion 510 and thus represents a constrained region for the deformable structure 520.

[0116] In the presence of mechanical stress, the piezoelectric detection region 547 generates a detection voltage between the lower detection electrode 545 and the upper detection electrode 549 , which can be sensed and measured by a sensing circuit in a known manner.

[0117] Furthermore, the deformation of the deformable structure 520 also generates pressure waves that propagate from the deformable structure 520 through the medium (eg, air, water, or other fluid) surrounding the piezoelectric MEMS actuator 500 .

[0118] If the pressure wave hits an obstacle, part of the pressure wave rebounds and reaches the piezoelectric MEMS actuator 500 again. The part of the pressure wave incident on the movable portion 520A of the deformable structure 520 modifies the degree of deformation of the deformable structure 520. Therefore, the mechanical stress changes, and therefore, the detection voltage also changes.

[0119] The change in detected voltage can be used by sensing circuitry. For example, the sensing circuitry can be configured to measure the time interval between the generation of a pressure wave and the detection of a portion of the pressure wave that rebounds and impinges on the piezoelectric MEMS actuator 500. The time interval is converted, for example using calibration parameters stored in memory, to calculate the distance between the deformable structure 520 and the obstacle.

[0120] Similar to what is described with respect to the detection structure 90 of the piezoelectric MEMS actuator 150 , the detection structure 536 of the piezoelectric MEMS actuator 500 can generate a high detection voltage; thus, the piezoelectric MEMS actuator 500 can have high sensitivity in monitoring the deformation of the deformable structure 520 .

[0121] Furthermore, the series connection of the detection cells 543 allows the detection voltage to have a high value, thus allowing also increasing the sensitivity of the piezoelectric MEMS actuator 500 in monitoring the deformation of the deformable structure 520 .

[0122] Figures 13 to 15 The piezoelectric MEMS actuator 500 can be connected to the reference Figures 2 to 10 The steps described for manufacturing the piezoelectric MEMS actuator 150 are obtained by similar manufacturing steps and are therefore not described further.

[0123] Figure 16 A different embodiment of the present piezoelectric MEMS actuator, indicated here by 600 , is shown having a similar basic structure and function to the piezoelectric MEMS actuator 500 ; therefore, common elements are designated with the same reference numerals.

[0124] In detail, the piezoelectric MEMS actuator 600 is also formed in the tube die 505, which here has a rectangular shape in a top plan view. Here too, the tube die 505 includes a bearing portion 510 and a deformable structure 520 surrounding a cavity 515 (not visible here).

[0125] Furthermore, the piezoelectric MEMS actuator 600 includes an actuation structure 535 and a detection structure 536. In this embodiment, the detection structure 536 includes a plurality of test detection structures 605 in addition to the plurality of detection units 543.

[0126] The test detection structures 605 are each formed from a corresponding stack (not shown here) similar to the stack forming the detection unit 536 , and extend over the actuation structure 535 .

[0127] In detail, here, in a top plan view, the test detection structures 605 have respective circular shapes and are concentric with each other, and may be connected in series in a manner similar to the detection units 543, or may be electrically separated from each other.

[0128] The test detection structure 605 is also connected to a sensing circuit (not shown).

[0129] Since the test detection structure 605 is arranged on the actuation structure 535 and is thus integral therewith, the test detection structure 605 is able to directly detect deformations of the actuation structure 535 , in particular deformations of the actuation piezoelectric region 539 .

[0130] Thus, the test detection structure 605 can be used to verify that the actuation structure 535 is correctly biased and actuated by the drive circuit. For example, the test detection structure 605 can be used as a diagnostic tool to verify the correct function of the piezoelectric MEMS actuator 600, thereby increasing its reliability.

[0131] Figure 17 Various embodiments of the present piezoelectric MEMS actuator (here indicated by 650) are shown. The piezoelectric MEMS actuator 650 is similar to Figure 16 The piezoelectric MEMS actuator 600, wherein the test detection structure indicated here by 655 is grid-shaped.

[0132] Figure 18A different embodiment of the present piezoelectric MEMS actuator, indicated here by 680, is shown. The piezoelectric MEMS actuator 680 has a similar basic structure as the piezoelectric MEMS actuators 600, 650; however, common elements are designated with the same reference numerals.

[0133] In detail, the die 505 here has a rectangular shape in a top plan view and comprises a deformable structure 685 having a movable portion 685A and a fixed portion 685B.

[0134] Here, through cavity 690 extends from and communicates with cavity 515 , through a central portion of movable portion 685A of deformable structure 685 , to first surface 505A of die 505 .

[0135] The actuation structure 535 of the piezoelectric MEMS actuator 680 extends over the movable portion 685A of the deformable structure 685 around a central portion of the movable portion 685A.

[0136] The detection structure 536 is formed by a plurality of detection units 543 and a test detection structure 695. In this embodiment, the test detection structures 695 have respective circular shapes and extend around and through the cavity 690 on the actuation structure 535. The test detection structures 695 can be connected in series similar to the detection structures 605 of the piezoelectric MEMS actuator 600, or can be electrically separated from each other.

[0137] Similar to what is described above, the piezoelectric MEMS actuator 680 can be used as a PMUT.The piezoelectric MEMS actuator 680 can be useful in certain applications where fluid communication between the upper and lower sides of the deformable structure 685 is desired.

[0138] Figure 19 Different embodiments of the present piezoelectric MEMS actuator, indicated here by 700, are shown. Piezoelectric MEMS actuator 700 has a similar basic structure to piezoelectric MEMS actuator 500; therefore, common elements are designated with the same reference numerals.

[0139] In detail, the piezoelectric MEMS actuator 700 also has cylindrical symmetry around the axis A and is formed in a tube core 705, which has a first surface 705A and a second surface 705B, and includes a bearing portion 710 surrounding a cavity 715, and a deformable structure 720, which has a movable portion 720A suspended on the cavity 715 and a fixed portion 720B fixed to the bearing portion 710.

[0140] The die 705 is formed of a multilayer structure 725 including a substrate 730 of semiconductor material, a first insulating layer 733 , such as an oxide, a structural layer 735 of semiconductor material, and a second insulating layer 738 , such as an oxide.

[0141] The base 730 is a hollow cylinder and is bounded downwardly by the second surface 705B of the die 705 and upwardly by the first upper surface 705A.

[0142] The first insulating layer 733 has a thickness of, for example, between 3 μm and 4 μm, and includes a first portion 734A extending on the substrate 730 , and a second portion 734B extending on the cavity 715 .

[0143] The structured layer 735 has a thickness of, for example, between 5 μm and 40 μm and extends over the first insulating layer 733 .

[0144] A second insulating layer 738 extends over the structural layer 735 and is bounded upwardly by the first surface 705A of the die 705 .

[0145] The cavity 715, which here is also cylindrical in shape, extends from the second surface 705B of the die 705 as far as the first insulating layer 733. The base 730 thus delimits the cavity 715 laterally, forming the bearing portion 710.

[0146] The first insulating layer 733 , the structural layer 735 and the second insulating layer 738 form a deformable structure 720 .

[0147] The MEMS piezoelectric actuator 700 further includes an actuating structure 740 and a detecting structure 745 , which are supported by the deformable structure 720 , in particular, by the movable portion 720A.

[0148] Similar to the actuation structure 535 of the piezoelectric MEMS actuator 500 , the actuation structure 740 extends over the second insulating layer 738 at the center of the movable portion 720A of the deformable structure 720 and is formed by a piezoelectric actuation region 741 sandwiched between a lower actuation electrode 742 and an upper actuation electrode 743 .

[0149] The detection structure 745 includes a plurality of detection units 750, each of which continuously extends at an edge of the movable portion 720A of the deformable structure 720 close to the fixed portion 720B (similar to the Figure 13 detection unit 536), but here it is buried in the deformable structure 720.

[0150] In detail, each detection unit 750 is formed of a lower detection electrode 752 , a piezoelectric detection region 754 , and an upper detection electrode 756 .

[0151] The lower detection electrode 752 includes a first doped region 752A and a first metal region 752B. The first doped region 752A extends through the thickness of the structural layer 735. The first metal region 752B, such as molybdenum, extends in the first insulating layer 733 and is in direct electrical contact with the first doped region 752A.

[0152] The piezoelectric detection region 754 is formed of the same piezoelectric material that forms the piezoelectric detection region 547 of the piezoelectric MEMS actuator 500 , such as aluminum nitride, and extends in the first insulating layer 733 over the first metal region 752B.

[0153] The upper detection electrode 756 is formed by: a second metal region 756A, such as molybdenum, extending in the first insulating layer 733 above the piezoelectric detection region 754; a second doped region 756B, extending through the thickness of the structural layer 735; and a conductive through hole 756C of conductive material, extending in the first insulating layer 733 between the second doped region 756B and the second metal region 756A and in direct electrical contact with the second doped region 756B and the second metal region 756A.

[0154] The piezoelectric MEMS actuator 700 has a passivation region 760 of, for example, 3 μm, which extends over the second insulating layer 738 and surrounds the actuation structure 740 .

[0155] The piezoelectric MEMS actuator 700 further includes a detection via 765 and an actuation via 770 of conductive material. The detection via 765 extends through the passivation region 760 and the second insulating layer 738 to the structural layer 735 and includes a first detection electrode via 765A that is in direct electrical contact with the first doped region 752A of the corresponding detection cell 750, and a second detection electrode via 765B that is in direct electrical contact with the second doped region 756B of the corresponding detection cell 750.

[0156] Actuation vias 770 extend through passivation region 760 and include a first actuation electrode via 770A in direct electrical contact with lower actuation electrode 742 and a second actuation electrode via 770B in direct electrical contact with upper actuation electrode 743 .

[0157] The detection vias 765 can be used to connect the detection units 750 in series and, together with the actuation vias 770 , to connect the actuation structure 740 with a drive circuit and to connect the detection structure 745 with a sensing circuit.

[0158] In use, piezoelectric MEMS actuator 700 has similar functionality to piezoelectric MEMS actuators 500, 600, 650, and 680. However, here, passivation region 760 is made of a single layer or multiple layers of oxide, such as TEOS, aluminum oxide, or undoped silicate glass (USG), which is less rigid than aluminum nitride, and is used to form passivation region 550 of piezoelectric MEMS actuator 500. Therefore, compared to actuation structure 535, at the same bias voltage, piezoelectric actuation region 741 is less constrained and more deformable, thereby improving the sensitivity of piezoelectric MEMS actuator 700.

[0159] Hereinafter, the fabrication of the piezoelectric MEMS actuator 700 is described according to an embodiment. For clarity, Figures 20 to 26 An enlarged cross section of one half of the piezoelectric MEMS actuator 700 is shown in successive fabrication steps. However, given the symmetry of the piezoelectric MEMS actuator 700 described above, fabrication of the entire piezoelectric MEMS actuator 700 will be clear to one skilled in the art.

[0160] Figure 20 A first wafer 800 of semiconductor material (intended to form the structural layer 735) having a first surface 800A and a second surface 800B is shown. In detail, first doped regions 752A and second doped regions 756B have been formed in the first wafer 800 and extend from the first surface 800A of the first wafer 800. For example, the first doped regions 752A and the second doped regions 756B are formed by implanting dopant ions through the first surface 800A. In this embodiment, the first doped regions 752A and the second doped regions 756B have the same thickness, for example, between 5 μm and 40 μm.

[0161] exist Figure 21 In the embodiment, the first metal region 752B, the piezoelectric detection region 754 and the second metal region 756A are formed on the first surface 800A of the first wafer 800 and on the first doped region 752A in a manner known per se.

[0162] Then, Figure 22 , for example, by photolithography, etching, and deposition steps, a conductive via 756C and a first insulating layer 733 are formed on the first surface 800A of the first wafer 800. Thus, the detection unit 750 is formed.

[0163] Then, Figure 23 , a second wafer 805 of semiconductor material (intended to form substrate 730 ) is bonded to first insulating layer 733 .

[0164] The first wafer 800 , the first insulating layer 733 and the second wafer 805 form a working structure 807 .

[0165] The working structure 807 is flipped upside down and thinned, for example, by grinding on the second surface 800B of the first wafer 800 to expose the first doped region 752A and the second doped region 756B. The remaining portion of the first wafer 800 forms the structural layer 735 .

[0166] exist Figure 24 In the embodiment, the second insulating layer 738 is deposited on the second surface 800B of the first wafer 800, and similarly to Figure 4 5 , a stack constituting an actuation structure 740 and including a lower actuation electrode 742 , a piezoelectric actuation region 741 , and an upper actuation electrode 743 is formed on the second insulating layer 738 .

[0167] Then, Figure 25 , a first conductive via region 810 is formed in the second insulating layer 738 and is in direct electrical contact with the first doped region 752A and the second doped region 756B.

[0168] exist Figure 26 , a passivation region 760 is formed and covers the second insulating layer 738, the first conductive via region 810, and the actuation structure 740. In addition, a second conductive via region 815 is formed through the passivation region 760 so as to contact the first conductive via region 810 (thus forming a detection via 765) or to contact the lower actuation electrode 742 and the upper actuation electrode 743 (thus forming an actuation via 770).

[0169] Then, Figure 27 The second wafer 805 is selectively etched from the exposed surface 805A down to the first insulating layer 733 , thereby forming the cavity 715 . The remaining portion of the second wafer 805 that laterally delimits the cavity 715 forms the base 730 .

[0170] The working structure 807 is then diced and each die forms a piezoelectric MEMS actuator 700 after conventional electrical connection and packaging steps.

[0171] With the help of Figures 20 to 27 In the manufacturing steps shown in , the actuating structure 740 and the detecting structure 745 are integrated on separate parts of the piezoelectric MEMS actuator 700. Therefore, the manufacturing steps taken to obtain the detecting structure 745 and the actuating structure 740 do not interfere with each other, thus allowing for better control and reliability of the entire manufacturing process.

[0172] Figure 28 A different embodiment of the present piezoelectric MEMS actuator is shown, here indicated by 850. Piezoelectric MEMS actuator 850 has a similar structure to piezoelectric MEMS actuator 800; therefore, common elements are designated with the same reference numerals.

[0173] In detail, the piezoelectric MEMS actuator 850 is also formed in the tube core 705, and the piezoelectric MEMS actuator 850 includes a bearing part 710 and a deformable structure 855, which is formed by a movable part 855A and a fixed part 855B, and the piezoelectric MEMS actuator 850 includes an actuating structure 740 and a detection structure 745.

[0174] The die 705 is formed of a multi-layer structure 860 including a substrate 730 surrounding the cavity 715 , a first insulating layer 865 , and a structural layer 735 .

[0175] The first insulating layer 865 has a first portion 866A extending on the substrate 730 and a second portion 866B extending on the cavity 715 .

[0176] The lightening cavity 870 extends from and communicates with the cavity 715 , through a central portion of the first insulating layer 865 , to the structural layer 735 beneath the actuation structure 740 .

[0177] The piezoelectric MEMS actuator 850 has improved reliability in use. In fact, in use, when the deformable structure 855 is deformed, there is no first insulating layer 865 under the actuating structure 740, avoiding the risk of delamination and / or cracking of the first insulating layer 865 that may be caused by mechanical stress.

[0178] The piezoelectric MEMS actuator 850 can be connected to Figures 20 to 27 , and are fabricated using steps similar to those shown in and described above for the piezoelectric MEMS actuator 700 .

[0179] In detail, the piezoelectric MEMS actuator 850 can be Figure 20 The first wafer 800 starts and executes Figure 21 and Figure 22 The steps shown in and described above are used to manufacture.

[0180] Then, Figure 29 , the first insulating layer 733 is selectively removed from the first surface 800A of the first wafer 800 so as to cover only the peripheral portion 900 of the first wafer 800 and the detection unit 750 and expose the central portion 901 of the first wafer 800 .

[0181] Then, Figure 30 , the second wafer 805 is bonded to the first insulating layer 865 to form a working structure 907 including a lightening cavity 870 .

[0182] The working structure 907 is then turned upside down and the first wafer 800 is thinned, similar to the reference Figure 23As described, a second insulating layer 738 and an actuation structure 740 are formed.

[0183] Final manufacturing steps are then performed to obtain the piezoelectric MEMS actuator 850 , similar to those described above for the piezoelectric MEMS actuator 700 .

[0184] Finally, it is clear that modifications and variations may be made to the piezoelectric MEMS actuators 150, 350, 500, 600, 850, 680, 700, 850, the microfluidic valves 300, 400, the methods for controlling microfluidic valves, and the manufacturing methods described and illustrated herein without departing from the scope of the present disclosure as defined in the appended claims.

[0185] For example, the different described embodiments may be combined to provide further solutions.

[0186] For example, the deformable structure 105 may be formed of a structure other than a membrane that is useful in a particular application, such as a cantilever, a diaphragm, or a structure having a special configuration.

[0187] The active actuation structure 65 may use a unimorph material having bimorph properties, as described, for example, in European patent application EP 3441358A1.

[0188] The layers forming the deformable and contracting structures may have different thicknesses depending on the desired deformation and the application.

[0189] Furthermore, the fluid channels may have different shapes.

[0190] The control unit 320 may be integrated in the piezoelectric MEMS actuator 150 or in the body 290; 390; or formed by a stand-alone device (eg an ASIC).

[0191] Furthermore, the lower actuation electrode and the lower detection electrode of the piezoelectric MEMS actuator 150 , 350 may be formed from unique conductive regions.

[0192] For example, it is clear that the manufacturing process of the piezoelectric MEMS actuators 700, 850 described above can be modified in a known manner to obtain different piezoelectric MEMS actuators, such as MEMS micromirrors, such as Figure 31 As shown in .

[0193] Here too, the deformable structure 855 of the piezoelectric MEMS actuator, indicated by 950 , comprises a movable structure 955 suspended in a through cavity 957 by means of a resilient structure (not shown here but known per se).

[0194] Removable structure 955 is formed in multi-layer structure 860 using portion 735A of structural layer 735 .

[0195] In this embodiment, the movable structure 955 includes a reinforcing strut 960 that extends in the cavity 715 and in the weight-reducing cavity 870 and is here formed by the joining portion 866C of the first insulating layer 865 and by the reinforcing portion 730A of the base 730 .

[0196] Piezoelectric MEMS actuator 950 also includes a reflective region 965 formed of, for example, metal (such as gold or aluminum) or a stack of dielectric materials, extending over portion 735A of structural layer 735, over movable structure 955, and configured to reflect a light beam incident thereon.

[0197] In use, in a known manner, a bias voltage can be applied to the actuating structure 740 to cause deformation of the deformable structure 855, as explained above, and thereby cause rotation of the movable structure 955, so that a light beam incident on the reflective region 960 can be reflected in a desired direction (e.g. unidirectionally or bidirectionally).

[0198] The various embodiments described above can be combined to provide additional embodiments. If it is necessary to adopt the concepts of various patents, applications and publications to provide yet further embodiments, the aspects of the embodiments can be modified. These and other changes can be made to the embodiments based on the above detailed description. Generally, in the following claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted as including all possible embodiments with the full range of equivalents enjoyed by the claim. Therefore, the claims are not limited by this disclosure.

Claims

1. A micro-electromechanical structure MEMS actuator, comprising: the base, surrounding the cavity; a deformable structure suspended on the cavity; An actuating structure comprising: a first piezoelectric region of a first piezoelectric material supported by the deformable structure and configured to cause deformation of the deformable structure; and A detection structure comprising: A second piezoelectric region of a second piezoelectric material is supported by the deformable structure and is configured to detect the deformation of the deformable structure, wherein the detection structure comprises a test detection structure on the actuation structure.

2. The actuator according to claim 1, further comprising: A passivation region surrounds the actuation structure and is formed of the second piezoelectric material.

3. The actuator of claim 1, wherein the first piezoelectric material is different from the second piezoelectric material.

4. An actuator according to claim 1, wherein the substrate includes a first side, the first side is separated from a second side by the cavity, and the deformable structure includes a support layer extending from the first side to the second side, the reinforcement layer is on a first surface of the support layer and the actuating structure is on a second surface of the support layer. 5 . The actuator of claim 1 , wherein the actuation structure comprises a lower actuation electrode, the first piezoelectric region, and an upper actuation electrode, and the detection structure comprises a lower detection electrode, the second piezoelectric region, and an upper detection electrode. 6 . The actuator of claim 5 , wherein the lower actuation electrode and the lower detection electrode are a single conductive region.

7. An actuator according to claim 1, wherein the deformable structure has a first surface and a second surface opposite to each other, the actuating structure is arranged on the first surface, and the actuator includes a contraction structure formed by a protruding area, and the protruding area is arranged on the second surface.

8. The actuator of claim 7, wherein the constriction structure extends into the cavity.

9. The actuator of claim 1, wherein the through cavity extends through a central portion of the deformable structure.

10. The actuator of claim 1, wherein the detection structure is buried in the deformable structure.

11. An actuator according to claim 10, wherein the deformable structure includes an insulating layer and a structural layer, the structural layer is a semiconductor material on the insulating layer, and a weight-reducing cavity extends from the cavity through the deformable structure to the structural layer, and the weight-reducing cavity is laterally bounded by the insulating layer.

12. A microfluidic valve comprising: main body; a fluid passageway within the body having a constriction defining a passageway having a passageway segment; Micro-electromechanical structure MEMS actuators, including: the base, surrounding the cavity; a deformable structure suspended on the cavity; a first piezoelectrically actuated region of a first piezoelectric material supported by the deformable structure and configured to cause deformation of the deformable structure, the first piezoelectrically actuated region coupled to the constriction and configured to modify the pathway segment; and a second piezoelectric sensing region of a second piezoelectric material supported by the deformable structure and configured to sense the deformation of the deformable structure; and A control unit is coupled to the MEMS actuator and configured to provide a bias voltage to the first piezoelectric actuation region and receive a detection voltage from the second piezoelectric detection region.

13. A microfluidic valve according to claim 12, wherein the fluid channel includes an inlet portion and an outlet portion, the contraction portion is arranged between the inlet portion and the outlet portion, and the contraction element in the contraction portion is coupled to the second piezoelectric detection region and is configured to modify the passage section in response to deformation of the second piezoelectric detection region.

14. A microfluidic valve according to claim 12, wherein the fluid channel further comprises an opening, the opening extending laterally to an inlet portion, the inlet portion being separated from the outlet portion by the constriction element, and a protrusion of the constriction element extending from the wall of the fluid channel through the opening and having an end facing the first piezoelectric actuation area at a certain distance to form the passage.

15. A microfluidic valve according to claim 14, wherein the body has a bonding surface; the MEMS actuator is bonded to the bonding surface of the body; the opening extends from the inlet portion and the outlet portion of the fluid channel to the bonding surface; the cavity of the MEMS actuator faces the opening and is fluidically connected to the opening.

16. A method comprising: controlling a microfluidic valve, the microfluidic valve comprising: a fluid channel having a constriction including a passageway; a microelectromechanical structure (MEMS) actuator having a first piezoelectric actuation region of a first piezoelectric material and a second piezoelectric detection region of a second piezoelectric material, the first piezoelectric actuation region being coupled to the constriction and being configured to modify the passageway segment; and a control unit coupled to the MEMS actuator; providing a bias voltage to the first piezoelectric actuation region via the control unit, the bias voltage generating a nominal flow rate in the fluid channel; providing a detection voltage between the lower detection electrode and the upper detection electrode to the control unit through the second piezoelectric detection region, the detection voltage corresponding to the measured flow amount; comparing the amount of electricity corresponding to the detection voltage with a value corresponding to the amount of the nominal flow rate; and A new bias voltage is applied in response to the measured flow quantity being different from the nominal flow quantity.

17. A method of manufacturing a MEMS actuator, comprising: forming a cavity and a deformable structure in a substrate of a semiconductor material wafer; forming an actuation structure comprising a first piezoelectric region of a first piezoelectric material supported by the deformable structure; forming a sensing structure comprising a second piezoelectric region of a second piezoelectric material supported by the deformable structure; as well as A test detection structure is formed on the actuation structure.

18. The manufacturing method according to claim 17, wherein: Forming the actuating structure further includes: forming a lower actuation electrode region from a first conductive layer; forming the first piezoelectric region on the lower actuating electrode region from a first piezoelectric layer; and forming an upper actuation electrode region on the first piezoelectric region from a second conductive layer; and Forming the detection structure further includes: forming a lower detection electrode region from the first conductive layer; forming the second piezoelectric region on the lower detection electrode region from a second piezoelectric layer; and An upper detection electrode region is formed on the second piezoelectric region from a third conductive layer. 19 . The manufacturing method of claim 18 , wherein forming the second piezoelectric region comprises depositing the second piezoelectric layer and defining the second piezoelectric layer to form the second piezoelectric region and a passivation region surrounding the actuation structure.

20. The manufacturing method according to claim 17, wherein forming the cavity in the substrate further comprises: forming a shaped region on the first surface of the substrate; forming a reinforcement region on the shaped region; forming a structural layer on the reinforced area; as well as A constriction structure protruding from the structural layer toward the cavity is formed by selectively removing the substrate from a second surface to the shaped area, the second surface being opposite to the first surface.

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