Piezoelectric MEMS transducer, processing method thereof, packaging structure and electronic device

Abstract

The embodiment of the present application discloses a piezoelectric MEMS transducer, a processing method, a packaging structure and an electronic device. The piezoelectric MEMS transducer comprises a substrate and a diaphragm. The diaphragm comprises a piezoelectric layer. The piezoelectric layer comprises a first region and a second region. The second region is arranged on at least one side of the first region. The first region and the second region are arranged in a first direction. The first region and the second region are arranged in a second direction. The first direction is the height direction of the piezoelectric MEMS transducer. The second direction is perpendicular to the first direction. First electrode layers are arranged on the opposite surfaces of the first region. Second electrode layers are arranged on the opposite surfaces of the second region. One technical effect of the embodiment of the present application is that a diaphragm with a single piezoelectric layer and without a substrate is arranged, so that the voltage required for driving the piezoelectric MEMS transducer is greatly reduced.

Description

Technical Field

[0001] This application belongs to the field of semiconductor device technology. Specifically, this application relates to a piezoelectric MEMS transducer, its processing method, packaging structure, and electronic device. Background Technology

[0002] Piezoelectric MEMS transducers utilize the bending vibration of micro-thin films to emit and receive ultrasonic waves, and are a type of ultrasonic transducer based on the piezoelectric energy conversion mechanism.

[0003] In existing technologies, piezoelectric MEMS transducers generally include a substrate layer, a support layer, and a structural layer. The structural layer and the support layer form a vibrating thin film. After partial etching of the substrate layer, a back cavity corresponding to the vibrating thin film is formed below the support layer. The structural layer is supported by the support layer and suspended above the back cavity. The structural layer typically includes a substrate and a piezoelectric layer. In use, by applying a driving voltage to the piezoelectric layer, according to the inverse piezoelectric effect, the piezoelectric layer expands and contracts, causing the substrate to deform, thereby achieving overall vibration of the structural layer.

[0004] However, since the substrate is thicker and has higher mechanical strength than the piezoelectric layer, a larger voltage is required to drive the structural layer to vibrate, and most of the voltage is consumed on the substrate. Summary of the Invention

[0005] The purpose of this application is to provide a new technology solution for piezoelectric MEMS transducers, their processing methods, packaging structures, and electronic devices.

[0006] According to a first aspect of the embodiments of this application, a piezoelectric MEMS transducer is provided, including a substrate, wherein a back cavity is disposed on the substrate; and

[0007] A diaphragm, wherein the diaphragm is disposed on the substrate and covers the back cavity, the diaphragm comprising a piezoelectric layer;

[0008] The diaphragm includes a first region and a second region, the second region being disposed on at least one side of the first region, the first region and the second region being offset in a first direction, and the first region and the second region being spaced apart in a second direction, wherein the first direction is the height direction of the MEMS transducer, and the second direction is perpendicular to the first direction;

[0009] One end of the first region and one end of the second region are fixedly connected to the substrate, and the ends of the two regions away from the substrate are connected to each other;

[0010] A first electrode layer is provided on each of the two opposite surfaces of the first region, and a second electrode layer is provided on each of the two opposite surfaces of the second region.

[0011] Optionally, when a voltage is applied to the piezoelectric MEMS transducer, the expansion and contraction directions of the first region and the second region are opposite.

[0012] Optionally, the polarization directions of the first region and the second region are the same, and the voltages connected to the first electrode layer and the second electrode layer are opposite.

[0013] Optionally, a first gap is provided between the first region and the second region, the first gap penetrating the diaphragm and communicating with the back cavity.

[0014] Optionally, the diaphragm further includes a central region, through which the ends of the first region and the second region away from the substrate are connected.

[0015] Optionally, the diaphragm includes multiple diaphragm flaps, and a second gap is provided between any two adjacent diaphragm flaps, the second gap passing through the central region and communicating with the back cavity.

[0016] Optionally, the membrane flaps are configured to be four;

[0017] Each of the membrane flaps is triangular, and the four membrane flaps are arranged symmetrically in pairs to form a rectangular piezoelectric cantilever membrane; or,

[0018] Each of the membrane flaps is fan-shaped, and the four membrane flaps together form a circular piezoelectric cantilever membrane.

[0019] According to a second aspect of the embodiments of this application, a method for fabricating the piezoelectric MEMS transducer described in the first aspect is also provided, comprising the following steps:

[0020] A substrate is provided, with a first fabrication area formed around its periphery based on a central region, and a second fabrication area formed outside the first fabrication area; wherein the first fabrication area and the second fabrication area have different height positions on the same side of the substrate;

[0021] A sacrificial layer is formed on the substrate, and a first electrode layer and a second electrode layer are respectively fabricated on the surface of the sacrificial layer. The first electrode layer is located in a first fabrication area, and the second electrode layer is located in a second fabrication area.

[0022] A piezoelectric layer is formed on the sacrificial layer, the piezoelectric layer including a first region corresponding to the first fabrication region and a second region corresponding to the second fabrication region, and the first electrode layer is bonded to the first region and the second electrode layer is bonded to the second region;

[0023] Another first electrode layer is formed on the surface of the first region away from the sacrificial layer, and another second electrode layer is formed on the surface of the second region away from the sacrificial layer; the piezoelectric layer, the first electrode layer and the second electrode layer form a diaphragm, the diaphragm is etched to form a plurality of diaphragm flaps, and a first gap is formed between the first region and the second region of each diaphragm flap;

[0024] Pads are formed on the surfaces of the first electrode layer and the second electrode layer, respectively;

[0025] A back cavity is formed on the side of the substrate away from the diaphragm, and the sacrificial layer corresponding to the back cavity is removed to obtain a piezoelectric MEMS transducer.

[0026] According to a third aspect of the embodiments of this application, a packaging structure is also provided, including a backplane and a housing disposed on the backplane, and the piezoelectric MEMS transducer described in the first aspect; wherein,

[0027] The back plate has a back sound hole, which is connected to the back cavity.

[0028] Optionally, the outer casing is provided with a sound hole.

[0029] According to a fourth aspect of the embodiments of this application, an electronic device is also provided, including the packaging structure described in the third aspect.

[0030] One technical advantage of the embodiments of this application is that:

[0031] The piezoelectric MEMS transducer provided in this application omits the substrate in its diaphragm structure, and the diaphragm consists of only a single piezoelectric layer. This piezoelectric layer includes a first region and a second region with different heights along the height direction of the piezoelectric MEMS transducer. This application achieves the performance required by existing piezoelectric microphones using double-layer PE and triple-layer electrodes simply by setting a single-layer piezoelectric layer structure, and significantly reduces the voltage required to drive the piezoelectric MEMS transducer.

[0032] Other features and advantages of this application will become clear from the following detailed description of exemplary embodiments with reference to the accompanying drawings. Attached Figure Description

[0033] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments of the present application and, together with their description, serve to explain the principles of the present application.

[0034] Figure 1 This is one of the overall structural schematic diagrams of the piezoelectric MEMS transducer provided in the embodiments of this application;

[0035] Figure 2This is the second schematic diagram of the overall structure of the piezoelectric MEMS transducer provided in the embodiments of this application;

[0036] Figure 3 This is the third schematic diagram of the overall structure of the piezoelectric MEMS transducer provided in the embodiments of this application;

[0037] Figure 4 This is one of the overall structural schematic diagrams of the diaphragm provided in the embodiments of this application;

[0038] Figure 5 This is the second schematic diagram of the overall structure of the diaphragm provided in the embodiments of this application;

[0039] Figure 6 for Figure 4 A sectional view along the A-A' direction;

[0040] Figure 7 for Figure 4 A sectional view along the B-B' direction;

[0041] Figure 8 A side view of the diaphragm provided in an embodiment of this application;

[0042] Figure 9 This is a schematic diagram of the structure of the diaphragm after deformation, provided in an embodiment of this application.

[0043] Figure 10 This is a schematic diagram of the processing method provided in the embodiments of this application;

[0044] Figure 11 This is one of the schematic diagrams of the packaging structure provided in the embodiments of this application;

[0045] Figure 12 This is a second schematic diagram of the packaging structure provided in the embodiments of this application;

[0046] Figure 13 The third schematic diagram of the packaging structure provided in the embodiments of this application.

[0047] Explanation of reference numerals in the attached figures:

[0048] 1. Substrate; 11. Back cavity; 2. Diaphragm; 21. Piezoelectric layer; 210. Central region; 211. First region; 212. Second region; 213. First gap; 214. First fabrication area; 22. First electrode layer; 23. Second electrode layer; 24. Second gap; 3. Diaphragm flap; 4. Sacrificial layer; 5. Pad; 6. Piezoelectric MEMS transducer; 7. Backplate; 71. Back acoustic aperture; 8. Outer shell; 81. Acoustic aperture. Detailed Implementation

[0049] Various exemplary embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that, unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0050] The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the scope of this application and its application or use.

[0051] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and equipment should be considered part of the specification.

[0052] In all the examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0053] It should be noted that similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be discussed further in subsequent figures.

[0054] This application discloses a piezoelectric MEMS transducer, a type of MEMS device that uses the direct and inverse piezoelectric effects of piezoelectric materials to vibrate a diaphragm, thereby emitting or receiving ultrasonic signals. When used to emit ultrasonic waves, it functions as an actuator; when used to receive ultrasonic waves, it functions as a sensor. Examples of piezoelectric MEMS transducers include microphones, bulk acoustic wave filters (BAW filters), micro-speakers, and piezoelectric micromachined ultrasonic transducers (PMUTs).

[0055] Reference Figures 1-9 This application discloses a piezoelectric MEMS transducer, including a substrate 1 with a back cavity 11 disposed on the substrate 1; and a diaphragm 2 disposed on the substrate 1 and covering the back cavity 11, the diaphragm 2 including a piezoelectric layer 21;

[0056] The piezoelectric layer 21 includes a first region 211 and a second region 212. The second region 212 is disposed on at least one side of the first region. The first region 211 and the second region 212 are offset in a first direction and spaced apart in a second direction. The first direction is the height direction of the piezoelectric MEMS transducer, and the second direction is perpendicular to the first direction.

[0057] One end of the first region 211 and one end of the second region 212 are fixedly connected to the substrate 1, and the ends of the two regions away from the substrate 1 are connected to each other;

[0058] A first electrode layer 22 is provided on two opposite surfaces of the first region 211, and a second electrode layer is provided on two opposite surfaces of the second region 212.

[0059] Reference Figure 1 In this embodiment of the application, the piezoelectric MEMS transducer 6 includes a substrate 1 and a diaphragm 2. The central region 210 of the substrate 1 is partially etched to form a back cavity 11. The diaphragm 2 is suspended above the back cavity 11. The back cavity 11 is disposed below the diaphragm 2 and corresponds to the diaphragm 2, that is, the diaphragm 2 covers the back cavity 11.

[0060] Please continue to refer to Figure 1 The diaphragm 2 includes a piezoelectric layer 21, which includes a first region 211 and a second region 212. The second region 212 is disposed on at least one side of the first region 211. That is, the second region 212 can be disposed on one side of the first region 211, or it can be disposed on both sides of the first region 211.

[0061] One end of the first region 211 and the second region 212 are fixedly connected to the substrate 1, and the ends of the first region 211 and the second region 212 away from the substrate 1 are connected to each other. This ensures that the diaphragm 2 moves synchronously in the first region 211 and the second region 212.

[0062] Specifically, in one embodiment of this application, reference is made to Figures 2-3 The second region 212 is disposed on both sides of the first region 211. The left ends of the first region 211 and the second region 212 are connected to the substrate 1, and the left ends of the first region 211 and the second region 212 are fixed ends. The right ends of the first region 211 and the second region 212 are connected to each other, and the right ends of the first region 211 and the second region 212 are free ends.

[0063] In this embodiment, the first region 211 and the second region 212 are offset in a first direction, which is the height direction of the piezoelectric MEMS transducer. The height direction of the piezoelectric MEMS transducer is also the vibration direction of the diaphragm 2. Figure 1The vertical direction of the diaphragm 2. That is, in this direction, the first region 211 and the second region 212 have different heights. The first region 211 and the second region 212 are located on two separate planes in the vibration direction of the diaphragm 2. Specifically, the height of the first region 211 can be greater than the height of the second region 212, meaning the first region 211 can be a protruding structure. The height of the first region 211 can be less than the height of the second region 212, meaning the first region 211 can be a recessed structure.

[0064] In one embodiment of this application, reference is made to... Figures 4-8 The first region 211 is a recessed structure, and the height of the first region 211 in this direction is less than the height of the second region 212. In other words, the distance between the first region 211 and the substrate 1 is less than the distance between the second region 212 and the substrate 1.

[0065] In this embodiment, the first region 211 and the second region 212 are spaced apart in a second direction, where the first direction is the height direction of the piezoelectric MEMS transducer, and the second direction is perpendicular to the first direction. That is, the second direction can be any direction perpendicular to the vibration direction of the diaphragm 2. A gap is provided between the first region 211 and the second region 212 in the second direction. Of course, the size of this gap can be set according to actual needs.

[0066] Reference Figure 4 The projections of the first region 211 and the second region 212 onto the substrate 1 do not overlap. In other words, the position corresponding to the first region 211 on the plane containing the second region 212 is hollowed out. The diaphragm 2 structure provided in this application includes only one piezoelectric layer 21 at each location.

[0067] A first electrode layer 22 is provided on two opposite surfaces of the first region 211, and a second electrode layer 23 is provided on two opposite surfaces of the second region 212. That is, two first electrode layers 22 are provided, and the two first electrode layers 22 are formed on the two surfaces of the piezoelectric layer 21 and cover the first region 211. The second electrode layers 23 are formed on the two surfaces of the piezoelectric layer 21 and cover the second region 212.

[0068] In the prior art, the diaphragm 2 generally includes a substrate and a piezoelectric layer 21. However, since the substrate is thicker and has higher mechanical strength than the piezoelectric layer 21, when the piezoelectric MEMS transducer 6 is used as an actuator, driving the diaphragm 2 to vibrate requires a large voltage, and most of the voltage is consumed on the substrate.

[0069] The piezoelectric MEMS transducer 6 provided in this application, on the one hand, reduces the loss of driving voltage on the substrate by omitting the substrate, thereby reducing the driving voltage required to drive the diaphragm 2 to vibrate when the MEMS transducer is used as an actuator. This allows it to match the voltage that current ASIC chips can achieve, improving the competitiveness of the piezoelectric MEMS transducer 6 and reducing the limitations imposed by excessively large driving voltage on the development of the piezoelectric MEMS transducer 6.

[0070] Specifically, in actuators (such as miniature loudspeakers), existing chip drivers fabricate lead piezoelectric material (PZT) thin films, electrodes, and patterns on the substrate of the MEMS diaphragm (such as Si or PolySi). A driving ASIC of up to approximately 30V can achieve the sensitivity required for typical inner ear applications. However, in recent years, RoHS restrictions on lead-containing PZT materials have become increasingly stringent, and they also exhibit poor compatibility with IC / CMOS processes.

[0071] However, directly replacing PZT with AlN piezoelectric materials compatible with CMOS technology remains challenging. This is primarily because the piezoelectric coefficient d31 of AlN is too low, approximately two orders of magnitude lower than that of PZT (typical values: AlN: d31 = -3.5 pV / m, ∈33 = 10 ∈ 0; while PZT-5R type d31 = -200 pV / m, ∈33 = 2000 ∈ 0). Therefore, fabricating piezoelectric MEMS transducers using AlN piezoelectric materials requires higher driving voltages (e.g., exceeding several hundred volts, S11 = d31 * Vdrive / Tpe, where S11 is the in-plane strain, d31 is the piezoelectric coefficient, and Vdrive is the driving voltage along the piezoelectric layer thickness). The power consumption calculation formula is as follows:

[0072] P=πf*C*Vpp2

[0073] =πf*(∈33*Area / Tpe)*(S11*Tpe / d31)2

[0074] =πf*Area*Tpe*S112*∈33 / d312

[0075] Therefore, the driving voltage and power required for the piezoelectric MEMS transducer 6 provided in this application are significantly reduced. Thus, the piezoelectric layer 21 can be made of AlN piezoelectric material compatible with CMOS technology, which is expected to promote the industrialization of lead-free AlN.

[0076] On the other hand, compared to the two-layer structure of the diaphragm 2 in the prior art, the single-layer piezoelectric layer 21 structure provided in this application significantly reduces problems such as unevenness, inconsistent performance, and yield loss of the diaphragm 2 caused by stress and dispersion during the processing of a single-layer piezoelectric layer. In terms of sensors (such as microphones), the fabrication process of the single-layer piezoelectric layer 21 is simpler than that of the existing double-layer structure, and the stress gradient is easier to control, giving it a competitive advantage in terms of performance and consistency, and at a lower cost.

[0077] In addition, in existing technologies, the diaphragm consists of a substrate and a piezoelectric layer. Because the substrate and piezoelectric layer are made of different materials, they expand and contract differently with temperature changes, resulting in the diaphragm structure being significantly affected by temperature. In this application, the first region 211 and the second region 212 of the piezoelectric layer 21 are designed to be symmetrically distributed along the thickness direction of the piezoelectric layer 21, and both regions are made of the same material. Therefore, the structure of the piezoelectric layer 21 changes little when the ambient temperature changes; that is, the piezoelectric MEMS transducer 6 has low sensitivity to ambient temperature and can maintain structural stability even when the ambient temperature changes.

[0078] Optionally, when a voltage is applied to the piezoelectric MEMS transducer 6, the first region 211 and the second region 212 expand in opposite directions.

[0079] When a voltage is applied to the piezoelectric layer 21, the expansion and contraction directions of the first region 211 and the second region 212 are opposite. The expansion and contraction direction of the piezoelectric layer 21 depends on the polarization direction and the direction of the applied electric field. Specifically, to make the expansion and contraction directions of the first region 211 and the second region 212 of the piezoelectric layer 21 opposite, in one case, the polarization directions of the first region 211 and the second region 212 are the same, and the electric field directions applied to the first electrode layer 22 and the second electrode layer 23 are opposite. In another case, the polarization directions of the first region 211 and the second region 212 are opposite, and the electric field directions applied to the first electrode layer 22 and the second electrode layer 23 are the same.

[0080] In this embodiment of the application, the polarization directions of the first region 211 and the second region 212 are the same;

[0081] The voltages connected to the first electrode layer 22 and the second electrode layer 23 are opposite.

[0082] Reference Figures 6-8 ,in, Figure 6 and Figure 7 The arrow in the diagram indicates the direction of the applied voltage. Figure 8 The arrows in the diagram indicate the direction of movement of the piezoelectric layer 21 under voltage. As shown in the diagram, voltages in opposite directions are applied to the first electrode layer 22 and the second electrode layer 23.

[0083] Specifically Figure 6 The downward arrow within the first region 211 indicates that the first electrode layer 22 applies a negative voltage to the piezoelectric layer 21 of the first region 211, and the upward arrow within the second region 212 indicates that the second electrode layer 23 applies a positive voltage to the piezoelectric layer 21 of the second region 212. (Refer to...) Figure 8 In one embodiment of this application, the piezoelectric layers 21 of both the first region 211 and the second region 212 are made of materials with negative piezoelectric coefficients, such as AlN. The polarization directions of the piezoelectric layers 21 of the first region 211 and the second region 212 are controlled to be the same. Under voltage, the second region 212 contracts, that is, it moves in the direction indicated by the arrow within the second region 212. The first region 211 expands, that is, it expands along... Figure 8 The diaphragm 2 moves in the direction indicated by the arrow within the first region 211, causing the free end of the diaphragm 2 to move upwards. Here, the free end is a concept relative to the fixed end; the end of the diaphragm 2 that is fixedly connected to the substrate 1 is the fixed end, i.e. Figure 8 The left end is shown. Figure 8 The right end of the diaphragm 2 shown is the free end, and the diaphragm 2 at the free end is suspended.

[0084] It should be noted that the first electrode layer 22 and the second electrode layer 23 are electrically connected to an external power source, and the first electrode layer 22 and the second electrode layer 23 are independently connected to the power source. Compared with the prior art, where the electrodes of the two piezoelectric layers 21 are shared, the first electrode layer 22 and the second electrode layer 23 are relatively independent in this application. Therefore, they can be electrically connected to form a differential signal output to improve important performance characteristics of the piezoelectric MEMS transducer 6, such as sensitivity, signal-to-noise ratio (SNR), and acoustic overload point (AOP).

[0085] Figure 9 This is a simplified schematic diagram showing the deformation of diaphragm 2. (Refer to...) Figure 9 The amplitude of diaphragm 2 can be calculated using the following formula:

[0086] H = R(1 - cos(θ)) = Rθ 2 / 2;

[0087] θ = L1 / R = L2 / (R+d);

[0088] (R+d)θ-Rθ=L1∈;

[0089] R = d / ∈;

[0090] H = L12 ∈ / (2d).

[0091] Where: H is the deformation of the first region 211 of the piezoelectric layer, that is, the amplitude of the first region 211 of the piezoelectric layer;

[0092] R is the radius of curvature of the piezoelectric layer in the first region 211 after deformation;

[0093] d is the distance between the piezoelectric layers of the first region 211 and the second region 212;

[0094] θ is the curvature of the piezoelectric layer in the first region 211 / second region 212 after deformation;

[0095] ∈ represents the difference in piezoelectric layer strain between the first region 211 and the second region 212;

[0096] L1 is the length of the piezoelectric layer in the first region 211, and L2 is the length of the piezoelectric layer in the second region 212.

[0097] Specifically, for example, the piezoelectric layer 21 is made of PZT material, the applied voltage is ±2.5V / um, L1=200um, d=1um, ∈=1e-3, and H=20um.

[0098] For example, the piezoelectric layer 21 is made of AlN material, the applied voltage is ±15V / um, L1=300um, d=0.5um, ∈=1e-4, and H=9um.

[0099] In this embodiment of the application, a first gap 213 is provided between the first region 211 and the second region 212. The first gap 213 penetrates the diaphragm 2 and communicates with the back cavity 11.

[0100] Reference Figures 4-7 The first gap 213 is disposed between the first region 211 and the second region 212 to separate the first region 211 and the second region 212 of the piezoelectric layer 21, so that the fixed ends of the piezoelectric layer 21 in the first region 211 and the second region 212 (i.e., Figure 5 The left ends of the piezoelectric layers 21 of the first region 211 and the second region 212 are fixedly connected to the substrate 1, while the free ends of the piezoelectric layers 21 of the first region 211 and the second region 212 are fixedly connected to the substrate 1. Figure 5 The right end of the two are connected by the middle region 210.

[0101] Reference Figure 8 When the polarization directions of the piezoelectric layers 21 are the same, and voltages in opposite directions are applied to the first region 211 and the second region 212 of the piezoelectric layers 21, the first region 211 of the piezoelectric layers 21 expands, and the second region 212 of the piezoelectric layers 21 contracts. This application provides a first gap 213 between the first region 211 and the second region 212, which reduces the mutual reaction force between the first region 211 and the second region 212 of the piezoelectric layers 21 when they deform, allowing them to work together to achieve the free end of the piezoelectric layer 21. Figure 5The deformation of the right end of the diaphragm 2, i.e. the vibration of the diaphragm 2, improves the sensitivity and accuracy of the vibration of the diaphragm 2, thereby improving the sensitivity, signal-to-noise ratio (SNR), and acoustic overload point (AOP) of the piezoelectric MEMS transducer 6.

[0102] In this embodiment of the application, the diaphragm 2 further includes a central region 210, and the ends of the first region 211 and the second region 212 away from the substrate 1 are connected through the central region 210.

[0103] Among them, reference Figures 2-3 The central region 210 is the area corresponding to the center position of the diaphragm 2, and the size of the central region 210 can be adjusted according to actual needs. The first region 211 and the second region 212 are connected as a whole through the central region 210.

[0104] In this embodiment of the application, the diaphragm 2 includes a plurality of diaphragm flaps 3, and a second gap 24 is provided between any two adjacent diaphragm flaps 3. The second gap 24 passes through the central region 210 and communicates with the back cavity 11.

[0105] When the area of ​​the diaphragm 2 is too large, the in-plane stress of the entire diaphragm 2 is too high, which affects the vibration efficiency and sensitivity of the diaphragm 2. Therefore, the diaphragm 2 in this application includes multiple diaphragm flaps 3.

[0106] The diaphragm flap 3 is cut from the diaphragm 2. A second gap 24 is provided between any two adjacent diaphragm flaps 3. The second gap 24 passes through the central region 210 and communicates with the back cavity 11. The second gap 24 passes through the second electrode layer 23, the piezoelectric layer 21 and the first electrode layer 22.

[0107] In this embodiment of the application, four membrane flaps 3 are provided;

[0108] Each of the membrane flaps 3 is triangular, and the four membrane flaps 3 are arranged symmetrically in pairs to form a rectangular piezoelectric cantilever membrane; or,

[0109] Each of the membrane flaps 3 is fan-shaped, and the four membrane flaps 3 are arranged to form a circular piezoelectric cantilever membrane.

[0110] In other words, referencing Figure 2 The diaphragm 2 is set as a rectangle, and the diaphragm 2 includes four diaphragm flaps 3, each of which is triangular.

[0111] Or refer to Figure 3 The diaphragm 2 is circular in shape and includes four diaphragm flaps 3, each flap 3 being fan-shaped.

[0112] A second gap 24 is formed between adjacent membrane flaps 3, and a first gap 213 is formed between the first region 211 and the second region 212 of each membrane flap 3.

[0113] This application also discloses a fabrication method for the piezoelectric MEMS transducer described above, wherein... Figure 10 The main focus is on the processing of the first region 211. The processing method disclosed in this application includes the following steps:

[0114] S1, providing substrate 1, reference Figure 10 A first manufacturing area 214 is formed around the central region 210, and a second manufacturing area is formed outside the first manufacturing area 214. Figure 10 (Not shown in the image); wherein the first fabrication area 214 and the second fabrication area have different height positions on the same side of the substrate 1. Figure 10 As shown, the height of the first production area 214 is lower than the height of the second production area.

[0115] The substrate 1 is made of Si or PolySi. When forming the first region 211, RIE or wet etching can be used to embed it into the silicon, forming a recessed first fabrication region 214. A second fabrication region is formed on the outer side of the first fabrication region 214. Alternatively, a LOCOS process can be used, which involves localized oxidation on the substrate 1, masked by SiO2 / Si3N4, and then the SiO2 / Si3N4 is removed to form the recessed first fabrication region 214. The second fabrication region is formed on the outer side of the first fabrication region 214.

[0116] S2, a sacrificial layer 4 is formed on the substrate 1, and a first electrode layer 22 and a second electrode layer 23 are respectively fabricated on the surface of the sacrificial layer 4, wherein, as shown in the figure... Figure 10 As shown, the first electrode layer 22 is located within the first fabrication area 214. The second electrode layer 23 is located within the second fabrication area. Figure 10 (Not shown in the image). The sacrificial layer 4 can be, for example, SiO2.

[0117] S3, a piezoelectric layer 21 is formed on the sacrificial layer 4. The piezoelectric layer 21 includes a first region 211 corresponding to the first fabrication region 214 and a second region 212 corresponding to the second fabrication region. The first electrode layer 22 is bonded to the first region 211 and the second electrode layer 23 is bonded to the second region 212.

[0118] The piezoelectric layer 21 can be made of AlN or PZT material. The materials of the first electrode layer 22 and the second electrode layer 23 are selected according to the material of the piezoelectric layer 21.

[0119] For example, when the piezoelectric layer 21 is made of AlN, the first electrode layer 22 and the second electrode layer 23 are made of molybdenum; when the piezoelectric layer 21 is made of PZT material, the first electrode layer 22 and the second electrode layer 23 are made of platinum.

[0120] S4, another first electrode layer 22 is formed on the surface of the first region 211 opposite to the sacrificial layer 4, and another second electrode layer 23 is formed on the surface of the second region 212 opposite to the sacrificial layer 4. The piezoelectric layer 21, the two first electrode layers 22, and the second electrode layer 23 form a diaphragm 2. As needed, a plurality of second gaps 24 are etched on the diaphragm 2 to divide the diaphragm 2 into a plurality of diaphragm flaps 3. In addition, a first gap 213 is etched in each diaphragm flap 3 to form a first gap 213, which separates the first region 211 from the second region 212.

[0121] S5, pads are formed on the surfaces of the two first electrode layers 22. Simultaneously, as... Figure 10 As shown, pads 5 are formed on the surfaces of the two second electrode layers 23.

[0122] S6, a back cavity 11 is formed on the side of the substrate 1 away from the piezoelectric layer 21, and the sacrificial layer 4 corresponding to the back cavity 11 is removed to obtain the piezoelectric MEMS transducer 6.

[0123] The back cavity 11 can be obtained by photolithography and DRIE etching through the silicon substrate 1. The sacrificial layer 4 can be removed by RIE dry etching and wet etching.

[0124] This application also discloses a packaging structure, including a backplate 7 and a housing 8 disposed on the backplate 7, and a piezoelectric MEMS transducer 6 as described above; wherein,

[0125] The back plate 7 has a back sound hole 71, which is connected to the back cavity 11.

[0126] Reference Figures 11-13 The piezoelectric MEMS transducer 6 is placed on the back plate 7, which has a back sound hole 71 that communicates with the back cavity 11 to facilitate sound transmission. The outer shell 8 covers the outer periphery of the piezoelectric MEMS transducer 6 and is connected to the back plate 7 to protect the piezoelectric MEMS transducer 6.

[0127] In this embodiment of the application, the outer shell 8 is provided with a sound hole 81.

[0128] Reference Figure 11 The sound hole 81 can be located on the side of the housing 8 opposite to the first gap 213. Of course, referring to... Figure 12 The sound hole 81 can also be provided on the side wall of the housing 8. This application does not limit the location of the sound hole 81.

[0129] It should be noted that, referring to Figure 13In this embodiment of the application, two piezoelectric MEMS transducers 6 are provided, and the two piezoelectric MEMS transducers 6 are connected in parallel through electrical and acoustic means, which can improve the consistency among multiple piezoelectric MEMS transducers 6.

[0130] Of course, there can be three or more piezoelectric MEMS transducers 6. This application does not limit the number of piezoelectric MEMS transducers 6. Multiple piezoelectric MEMS transducers 6 can be connected in parallel in an electrical and acoustic manner.

[0131] This application also provides an electronic device including the packaging structure described above.

[0132] Among them, electronic devices can be head-mounted displays, smartwatches, mobile phones, etc.

[0133] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of this application. The scope of this application is defined by the appended claims.

Claims

1. A piezoelectric MEMS transducer, characterized in that, include: Substrate (1), on which a back cavity (11) is provided; as well as A diaphragm (2) is disposed on the substrate (1) and covers the back cavity (11), the diaphragm (2) includes a piezoelectric layer (21). The piezoelectric layer (21) includes a first region (211) and a second region (212). The second region (212) is disposed on at least one side of the first region (211). The first region (211) and the second region (212) are offset in a first direction and spaced apart in a second direction. The first direction is the height direction of the piezoelectric MEMS transducer, and the second direction is perpendicular to the first direction. One end of the first region (211) and the second region (212) are fixedly connected to the substrate (1), and the ends of the two regions away from the substrate (1) are connected to each other; A first electrode layer (22) is provided on two opposite surfaces of the first region (211), and a second electrode layer (23) is provided on two opposite surfaces of the second region (212). The diaphragm (2) further includes a central region (210), and the ends of the first region (211) and the second region (212) away from the substrate (1) are connected through the central region (210); The diaphragm (2) includes multiple diaphragm flaps (3), and a second gap (24) is provided between any two adjacent diaphragm flaps (3). The second gap (24) passes through the central region (210) and communicates with the back cavity (11).

2. The piezoelectric MEMS transducer according to claim 1, characterized in that, When a voltage is applied to the piezoelectric MEMS transducer (6), the first region (211) and the second region (212) expand in opposite directions.

3. The piezoelectric MEMS transducer according to claim 1, characterized in that, The polarization directions of the first region (211) and the second region (212) are the same; The voltages connected to the first electrode layer (22) and the second electrode layer (23) are opposite.

4. The piezoelectric MEMS transducer according to claim 1, characterized in that, A first gap (213) is provided between the first region (211) and the second region (212). The first gap (213) penetrates the diaphragm (2) along the thickness direction and communicates with the back cavity (11).

5. The piezoelectric MEMS transducer according to claim 1, characterized in that, The membrane flaps (3) are configured to be four; Each of the membrane flaps (3) is triangular, and the four membrane flaps (3) are arranged symmetrically in pairs to form a rectangular piezoelectric cantilever membrane; or, Each of the membrane flaps (3) is fan-shaped, and the four membrane flaps (3) are enclosed to form a circular piezoelectric cantilever membrane.

6. A method for fabricating a piezoelectric MEMS transducer, characterized in that, Includes the following steps: A substrate (1) is provided, and a first fabrication area (214) is formed on its periphery with reference to the central region (210), and a second fabrication area is formed on the outside of the first fabrication area (214); wherein the first fabrication area (214) and the second fabrication area have different height positions on the same side of the substrate (1); A sacrificial layer (4) is formed on the substrate (1), and a first electrode layer (22) and a second electrode layer (23) are respectively fabricated on the surface of the sacrificial layer (4). The first electrode layer (22) is located in the first fabrication area (214), and the second electrode layer (23) is located in the second fabrication area. A piezoelectric layer (21) is formed on the sacrificial layer (4). The piezoelectric layer (21) includes a first region (211) corresponding to the first fabrication region (214) and a second region (212) corresponding to the second fabrication region. The first electrode layer (22) is bonded to the first region (211) and the second electrode layer (23) is bonded to the second region (212). Another first electrode layer (22) is formed on the surface of the first region (211) away from the sacrificial layer (4), and another second electrode layer (23) is formed on the surface of the second region (212) away from the sacrificial layer (4). The piezoelectric layer (21), the first electrode layer (22) and the second electrode layer (23) form a diaphragm (2). The diaphragm (2) is etched to form a plurality of diaphragm flaps (3), and a first gap (213) is formed between the first region (211) and the second region (212) of each diaphragm flap (3). Pads (5) are formed on the surfaces of the first electrode layer (22) and the second electrode layer (23), respectively. A back cavity (11) is formed on the side of the substrate (1) away from the diaphragm (2), and the sacrificial layer (4) corresponding to the back cavity (11) is removed to obtain a piezoelectric MEMS transducer (6).

7. A packaging structure, characterized in that, The device includes a backplate (7) and a housing (8) disposed on the backplate (7), and a piezoelectric MEMS transducer (6) according to any one of claims 1-5; wherein, The back plate (7) has a back sound hole (71) which is connected to the back cavity (11).

8. The packaging structure according to claim 7, characterized in that, The outer shell (8) has a sound hole (81).

9. An electronic device, characterized in that, Includes the packaging structure described in any one of claims 7-8.

Images