A piezoelectric micromechanical ultrasonic transducer

Abstract

This invention discloses a piezoelectric micromechanical ultrasonic transducer, belonging to the technical field of piezoelectric micromechanical ultrasonic transducers. It includes a substrate and a vibrating diaphragm supported on the substrate. The vibrating diaphragm includes a first region located in the center and a second region surrounding the first region. The first region has a planar structure; the second region has a corrugated structure with alternating undulations along the radial direction of the vibrating diaphragm. The corrugated structure is used to reduce the edge constraint stiffness of the vibrating diaphragm and disperse mechanical stress. A piezoelectric transducer component is disposed on the vibrating diaphragm, located within the first region. This piezoelectric micromechanical ultrasonic transducer aims to solve the problems of limited vibration amplitude and stress concentration in traditional planar thin-film structures of piezoelectric micromechanical ultrasonic transducers, thereby improving the reliability and transduction efficiency of the device.

Description

Technical Field

[0001] This invention belongs to the technical field of piezoelectric micromechanical ultrasonic transducers, and specifically relates to a piezoelectric micromechanical ultrasonic transducer. Background Technology

[0002] Piezoelectric micromechanical ultrasonic transducers (PMUTs), representing the next generation of ultrasonic sensing technology, possess a core advantage in perfectly combining the properties of piezoelectric materials with micro / nano fabrication processes, achieving miniaturization, low power consumption, and high integration. Traditional PMUTs typically employ planar thin-film structures as the vibration unit. This structure suffers from edge constraint effects during vibration, leading to uneven energy distribution and limited vibration amplitude in the central region. Furthermore, the fixed boundary conditions at the film edges cause significant stress concentration during vibration, especially at high frequencies, which significantly reduces device reliability and lifespan. While optimizing electrode patterns or introducing non-planar structures can improve sensitivity in existing technologies, this often comes at the cost of structural reliability, failing to fundamentally resolve the contradiction between stress concentration and increased vibration amplitude. Moreover, the insufficient matching between the piezoelectric functional layer and the vibrating diaphragm in traditional structures easily leads to interface delamination due to differences in thermal expansion coefficients, further restricting device performance. These problems severely limit the widespread use of PMUTs in high-precision applications such as medical ultrasound imaging and industrial non-destructive testing.

[0003] Therefore, existing technologies need to be improved and developed. Summary of the Invention

[0004] The purpose of this invention is to provide a piezoelectric micromechanical ultrasonic transducer, which aims to solve the problems of limited vibration amplitude and stress concentration in the planar thin film structure of traditional piezoelectric micromechanical ultrasonic transducers, thereby improving the reliability and transduction efficiency of the device.

[0005] In a first aspect, the present invention provides a piezoelectric micromechanical ultrasonic transducer, comprising a substrate and a vibrating diaphragm supported on the substrate. The vibrating diaphragm includes a first region located in the center and a second region disposed around the first region. The first region has a planar structure. The second region has a corrugated structure that is alternately undulating along the radial direction of the vibrating diaphragm. The corrugated structure is used to reduce the edge constraint stiffness of the vibrating diaphragm and disperse mechanical stress. A piezoelectric transducer is disposed on the vibrating diaphragm, and the piezoelectric transducer is disposed in the first region.

[0006] The piezoelectric micromechanical ultrasonic transducer of the present invention adopts a design that combines a central planar structure with a surrounding corrugated structure for the vibrating diaphragm. The corrugated structure can effectively reduce the edge constraint stiffness of the vibrating diaphragm and disperse mechanical stress, thereby improving the overall flexibility of the vibrating diaphragm, enhancing the vibration amplitude, and significantly reducing the risk of stress concentration. This solves the problems of limited vibration amplitude and stress concentration in traditional planar thin film structures, and improves the reliability and transduction efficiency of the device.

[0007] Furthermore, the vibrating diaphragm has a circular thin film structure.

[0008] Furthermore, the corrugated structure is a ring array structure arranged around the first region; the crests and troughs of the corrugated structure extend continuously along the circumference of the vibrating diaphragm in the second region, and the corrugated structure is centrally symmetrically distributed in the second region.

[0009] Furthermore, the piezoelectric transducer includes a piezoelectric layer, the projected area of ​​which on the vibrating diaphragm accounts for 50%-70% of the total area of ​​the vibrating diaphragm.

[0010] Furthermore, the thickness of the vibrating diaphragm is 3-8 μm.

[0011] Furthermore, the radius of the first region is 70%-95% of the radius of the vibrating diaphragm.

[0012] Furthermore, the width of the corrugated structure is 5%-30% of the radius length of the vibrating diaphragm.

[0013] Furthermore, the corrugated structure has a sinusoidal or trapezoidal cross-sectional shape in the radial direction of the vibrating diaphragm.

[0014] Furthermore, the substrate is provided with a cavity, and the entire first region is suspended above the cavity as a membrane.

[0015] Furthermore, the piezoelectric transducer also includes electrode layers disposed on the upper and lower sides of the piezoelectric layer.

[0016] As can be seen from the above, the piezoelectric micromechanical ultrasonic transducer of the present invention, by setting a first region with a central planar structure and a second region with a corrugated structure surrounding the first region on the vibrating diaphragm, and making the corrugated structure have the characteristic of alternating undulations along the radial direction of the vibrating diaphragm, can effectively reduce the edge constraint stiffness of the vibrating diaphragm and disperse mechanical stress. This design fundamentally solves the problem of limited vibration amplitude and stress concentration caused by the edge constraint effect of traditional planar thin film structures during vibration. Through the dispersion of mechanical stress by the corrugated structure, the stress concentration phenomenon under high-frequency operating conditions is significantly reduced, thereby improving the reliability and service life of the device. At the same time, the increased flexibility of the vibrating diaphragm allows the central region of the vibrating diaphragm to obtain a larger vibration amplitude, giving full play to the energy conversion efficiency of the piezoelectric material. In addition, the piezoelectric transducer component is set in the first region, ensuring effective electroacoustic conversion. In summary, the technical solution of this application overcomes the contradiction between stress concentration and vibration amplitude improvement in the prior art, and significantly improves the performance and reliability of the piezoelectric micromechanical ultrasonic transducer.

[0017] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing embodiments of the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the cross-sectional structure of a piezoelectric micromechanical ultrasonic transducer provided in an embodiment of the present invention.

[0019] Label Explanation: 100, Substrate; 200, Vibrating diaphragm; 210, First region; 220, Second region; 221, Corrugated structure; 300, Piezoelectric layer; 400, Electrode layer; 500, Cavity. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0025] In traditional piezoelectric micromechanical ultrasonic transducers, the vibration amplitude of the diaphragm directly affects the device's sensitivity, sound pressure output, and energy conversion efficiency. However, as the vibration amplitude increases, the mechanical stress at the diaphragm's edge also increases, leading to stress concentration. This stress concentration primarily occurs near the fixed boundary of the diaphragm, easily causing localized material fatigue damage and thus weakening the device's long-term reliability. Existing technologies, such as electrode pattern optimization or non-planar diaphragm structure design, while improving the vibration amplitude, struggle to effectively disperse mechanical stress and may even exacerbate stress concentration at the edge.

[0026] For example, in medical ultrasound imaging equipment, piezoelectric micromechanical ultrasonic transducers are used to acquire images of biological tissues. When the driving voltage is increased to enhance signal strength, the vibration amplitude of the diaphragm increases, but stress concentration in the edge regions leads to the formation of microcracks. These microcracks gradually propagate during continuous operation, eventually causing the diaphragm to rupture or its performance to degrade, resulting in image quality degradation, system interruption, and the need for maintenance.

[0027] If the above problems are not addressed, the reliability of piezoelectric micromechanical ultrasonic transducers will decrease, device lifespan will be shortened, and the continuous operation capability of the system will be affected. Fatigue accumulation in stress concentration areas will accelerate device failure. In critical applications, unexpected failure may lead to functional interruption, increasing maintenance requirements and operational risks.

[0028] For reference, see the appendix. Figure 1 The present invention provides a piezoelectric micromechanical ultrasonic transducer, including a substrate 100 and a vibrating diaphragm 200 supported on the substrate 100. The vibrating diaphragm 200 includes a first region 210 located in the middle and a second region 220 disposed around the first region 210. The first region 210 has a planar structure. The second region 220 has a corrugated structure 221 that is alternately distributed along the radial direction of the vibrating diaphragm 200. The corrugated structure 221 is used to reduce the edge constraint stiffness of the vibrating diaphragm 200 and disperse mechanical stress. A piezoelectric transducer is disposed on the vibrating diaphragm 200 and disposed within the first region 210.

[0029] For ease of understanding, the following explains some key terms in this embodiment: A piezoelectric micromechanical ultrasonic transducer is a miniature device that utilizes the piezoelectric effect to convert electrical energy into acoustic energy. Its core function is to generate or receive ultrasonic waves through the deformation of piezoelectric materials. These transducers are typically integrated onto silicon substrates and offer advantages such as small size, low power consumption, and ease of integration. They are widely used in fields such as medical imaging, fingerprint recognition, and non-destructive testing.

[0030] The substrate 100 is the basic support structure of the piezoelectric micromechanical ultrasonic transducer, and is typically made of silicon. Its main function is to provide a stable platform for subsequent microfabrication processes such as thin film deposition, patterning, and etching, and to support the vibrating diaphragm 200 and other functional layers. The material and structural characteristics of the substrate 100 directly affect the overall mechanical stability, thermal performance, and compatibility with external circuits of the device.

[0031] The vibrating diaphragm 200 is the core component of the piezoelectric micromechanical ultrasonic transducer, which transmits and receives ultrasonic waves through bending vibration. The vibrating diaphragm 200 is usually made of thin film materials such as polycrystalline silicon and silicon nitride. Its thickness, size, material properties, and structural design have a decisive influence on the transducer's resonant frequency, vibration amplitude, sensitivity, and sound pressure output.

[0032] The first region 210 is the central portion of the vibrating diaphragm 200 and is typically designed as a planar structure. This region primarily supports the piezoelectric transducer and converts electrical signals into acoustic signals, or vice versa, through its vibration. The planar nature of the first region 210 ensures stable operation and efficient energy conversion of the piezoelectric transducer.

[0033] The second region 220 is the edge portion of the vibrating diaphragm 200 surrounding the first region 210. This region has a corrugated structure 221 that is alternately undulating along the radial direction of the vibrating diaphragm 200. Its main function is to adjust the overall mechanical properties of the vibrating diaphragm 200, especially to reduce the edge constraint stiffness and disperse mechanical stress, thereby increasing the vibration amplitude and enhancing the reliability of the device.

[0034] The corrugated structure 221 is a characteristic structure of the second region 220, which is periodically undulating along the radial direction of the vibrating diaphragm 200. This structural design can effectively increase the flexibility of the vibrating diaphragm 200, reduce the edge stress concentration during vibration, and absorb and disperse mechanical stress through structural deformation, thereby extending the service life of the device while ensuring vibration performance.

[0035] The piezoelectric transducer is the core functional unit for realizing electroacoustic conversion, and it is usually composed of a piezoelectric layer 300 and upper and lower electrode layers 400. When an electric field is applied, the piezoelectric layer 300 deforms, driving the vibrating diaphragm 200 to vibrate and generate ultrasonic waves; conversely, when ultrasonic waves are received, the vibration of the vibrating diaphragm 200 will cause the piezoelectric layer 300 to generate charges, thereby realizing the reception of ultrasonic waves.

[0036] This application proposes a piezoelectric micromechanical ultrasonic transducer, aiming to solve the problem of stress concentration while increasing the vibration amplitude of the piezoelectric micromechanical ultrasonic transducer, thus achieving a balance between improved sensitivity and reliability. The transducer includes a substrate 100 and a vibrating diaphragm 200 supported on the substrate 100. The structural design of the vibrating diaphragm 200 is the core of this application, which is divided into a first region 210 located in the center and a second region 220 surrounding the first region 210.

[0037] Specifically, the first region 210 is designed as a planar structure. This planar structure facilitates the stable integration and efficient operation of the piezoelectric transducer. For example, the piezoelectric transducer can be directly deposited or bonded to the surface of the first region 210, ensuring effective conversion of electrical signals to mechanical vibrations. In practical applications, the size of the first region 210 can be adjusted according to the required resonant frequency and vibration amplitude. For example, when a higher resonant frequency is required, the size of the first region 210 can be relatively small; when a larger vibration amplitude is required, the size of the first region 210 can be relatively large.

[0038] The second region 220 has a corrugated structure 221 that alternately undulates radially along the diaphragm 200. This corrugated structure 221 is one of the key innovations of this application, and its main function is to reduce the edge constraint stiffness of the diaphragm 200 and disperse mechanical stress. By introducing the corrugated structure 221, the diaphragm 200 can achieve greater flexibility during vibration, thereby generating a larger vibration amplitude under the same driving voltage. At the same time, the corrugated structure 221 can uniformly distribute the mechanical stress generated during vibration throughout the second region 220, avoiding the problem of stress concentration at the edges of traditional planar diaphragms, and significantly improving the reliability and service life of the device. For example, the corrugated structure 221 can adopt a series of concentric ring-shaped alternating peaks and troughs, or a spiral undulating structure. These structures can effectively increase the effective length of the diaphragm, thereby reducing the overall stiffness.

[0039] A piezoelectric transducer is disposed on the vibrating diaphragm 200, and the piezoelectric transducer is disposed within the first region 210. Placing the piezoelectric transducer within the first region 210 of the planar structure ensures that the piezoelectric material can deform uniformly and effectively under the action of an electric field, thereby driving the entire vibrating diaphragm 200 to vibrate. At the same time, since the piezoelectric transducer is not directly located on the corrugated structure 221, the interference that the corrugated structure 221 may cause to the piezoelectric effect is avoided, ensuring the transducer efficiency. For example, the piezoelectric transducer can be composed of a piezoelectric thin film sandwiched between two layers of electrodes. By applying an AC voltage, the piezoelectric thin film is periodically stretched and contracted, thereby driving the vibrating diaphragm 200 to vibrate.

[0040] The following example will provide a more detailed explanation of the above technical solution: Suppose a piezoelectric micromechanical ultrasonic transducer (PMUT) is required for medical ultrasound imaging, demanding high sensitivity and long lifespan. Traditional PMUTs are prone to localized stress concentration when increasing vibration amplitude, affecting device reliability. To address this, this application proposes a piezoelectric micromechanical ultrasonic transducer with a circular thin-film diaphragm structure made of polycrystalline silicon, with a total thickness of 3-8 µm. The diaphragm is radially divided into a central region and an outer ring region, both integrally molded.

[0041] Specifically, the transducer includes a substrate 100 on which a circular vibrating diaphragm 200 is supported. The vibrating diaphragm 200 is designed with two main parts: a first region 210 located in the center and a second region 220 surrounding the first region 210. The first region 210 is designed as a planar structure, with its diameter accounting for 70%-95% of the total diameter of the vibrating diaphragm 200. This planar region serves as the core vibration region for ultrasonic transceiver, ensuring the stable operation of the piezoelectric transducer assembly. For example, a piezoelectric layer 300 can be deposited on the surface of the first region 210, and electrode layers 400 can be disposed on its upper and lower sides, respectively, to form the piezoelectric transducer assembly. When an electrical signal is applied, the piezoelectric layer 300 deforms, driving the first region 210 to produce bending vibration, thereby emitting ultrasonic waves.

[0042] The outer ring region surrounding the first region 210 is the second region 220, which is fabricated as a continuous ring array of corrugated structures 221. The crests and troughs of the corrugated structure 221 alternate radially along the vibrating diaphragm 200, and its width accounts for 5%-30% of the total diameter of the vibrating diaphragm 200. This corrugated structure 221 is fabricated by patterning the oxide layer and depositing polysilicon. For example, the corrugated structure 221 can be designed as a sinusoidal or trapezoidal wave shape to increase the flexibility of the vibrating diaphragm 200 and enhance the vibration amplitude. When the first region 210 begins to vibrate under the drive of the piezoelectric transducer, the corrugated structure 221 provides additional flexibility, significantly increasing the overall vibration amplitude of the vibrating diaphragm 200. Simultaneously, due to the presence of the corrugated structure 221, the mechanical stress generated during vibration is no longer concentrated at the edge of the vibrating diaphragm 200, but is uniformly distributed throughout the corrugated region. This stress dispersion mechanism effectively avoids the fatigue damage and cracking problems that traditional planar diaphragms are prone to under long-term high-intensity vibration, thereby significantly improving the reliability and service life of the device.

[0043] Through the above structural design, when the piezoelectric micromechanical ultrasonic transducer is in operation, the piezoelectric transducer component generates a driving force within the first region 210, causing the first region 210 to vibrate. Due to the additional flexibility provided by the corrugated structure 221 of the second region 220, the vibration amplitude of the first region 210 is significantly increased, thereby improving the ultrasonic wave transmission intensity and receiving sensitivity. Simultaneously, the corrugated structure 221 effectively disperses the mechanical stress generated during vibration, avoiding device failure caused by stress concentration and ensuring the stability of the transducer during long-term operation.

[0044] The technical concept of this application cleverly solves the stress concentration problem that is difficult to avoid in traditional piezoelectric micromechanical ultrasonic transducers when pursuing high vibration amplitude by introducing a corrugated structure 221 at the edge of the vibrating diaphragm 200. Compared with the existing technology that simply improves sensitivity by optimizing the electrode pattern or using a non-planar diaphragm structure, but which leads to local stress concentration, the innovation of this application lies in dividing the vibrating diaphragm 200 into a central plane first region 210 and an edge corrugated second region 220, thus achieving both improved sensitivity and stress relief.

[0045] Specifically, the planar structure of the first region 210 ensures the efficient operation of the piezoelectric transducer, while the corrugated structure 221 of the second region 220 significantly increases the overall vibration amplitude of the diaphragm 200 by reducing edge constraint stiffness, thereby improving the transducer's sensitivity. For example, in ultrasonic imaging applications, higher sensitivity means the ability to detect weaker ultrasonic signals, resulting in clearer and deeper image information. Simultaneously, the corrugated structure 221 effectively disperses mechanical stress, avoiding fatigue damage caused by stress concentration at the edges of traditional planar diaphragms and significantly extending the device's lifespan. This stress dispersion mechanism is difficult to achieve in existing technologies because traditional non-planar diaphragm structures often only change the overall shape of the diaphragm without fundamentally solving the stress concentration problem.

[0046] Therefore, the technical solution of this application not only achieves significant progress in improving the vibration amplitude of piezoelectric micromechanical ultrasonic transducers, but more importantly, it effectively alleviates mechanical stress concentration through a unique corrugated structure design, thereby greatly improving the reliability of the device while ensuring high performance. This technical solution, which balances sensitivity and reliability, provides a solid technical foundation for the widespread application of piezoelectric micromechanical ultrasonic transducers in medical, industrial, and other fields, and has significant technical contributions and creativity.

[0047] In some embodiments, the vibrating diaphragm 200 is a circular thin film structure; the corrugated structure 221 is a ring array structure arranged around the first region 210; the crests and troughs of the corrugated structure 221 extend continuously along the circumference of the vibrating diaphragm 200 within the second region 220, and the corrugated structure 221 is centrally symmetrically distributed within the second region 220; the radius of the first region 210 is 70%-95% of the radius of the vibrating diaphragm 200; and the width of the corrugated structure 221 is 5%-30% of the radius of the vibrating diaphragm 200.

[0048] The vibrating diaphragm 200 is a circular thin-film structure. As the core vibrating component of the piezoelectric micromechanical ultrasonic transducer, it is typically made of materials such as silicon, silicon nitride, or polycrystalline silicon. The circular structure itself possesses natural symmetry, providing a basis for achieving uniform ultrasonic wave transmission and reception. In some embodiments, the vibrating diaphragm 200 may be made of polycrystalline silicon and have a thickness of 3-8 micrometers to balance its flexibility and mechanical strength.

[0049] The corrugated structure 221 is designed as a ring array structure surrounding the first region 210. This structure effectively increases the flexibility of the vibrating diaphragm 200 by forming a series of concentric or nearly concentric corrugations within the second region 220 of the vibrating diaphragm 200. This ring array structure can be formed into a continuous undulating pattern in the outer ring region of the vibrating diaphragm 200 using microfabrication processes such as photolithography and etching. For example, this ring array can be formed by combining multilayer thin film deposition with patterned etching, or by deep etching of a single layer of material.

[0050] The crests and troughs of the corrugated structure 221 extend continuously along the circumference of the vibrating diaphragm 200 within the second region 220. This means that the undulations of the corrugations are uninterrupted in the direction surrounding the central region, forming a continuous loop or spiral path. This continuity helps to evenly distribute the mechanical stress generated during vibration throughout the entire second region 220, avoiding stress concentration at specific points or areas, thereby improving the fatigue life and reliability of the vibrating diaphragm 200. In terms of implementation, precise photolithographic mask design can ensure seamless connection of the corrugated pattern in the circumferential direction.

[0051] The corrugated structure 221 is centrally symmetrically distributed within the second region 220. This symmetry ensures that the diaphragm 200 exhibits consistent mechanical response in both the radial and circumferential directions, enabling the diaphragm 200 to vibrate uniformly and stably when excited. The centrally symmetrical corrugated design can be achieved through the use of masks and processes with high-precision alignment capabilities during manufacturing, for example, by employing rotationally symmetrical patterning in photolithography to ensure that the geometry and distribution of the corrugated structure 221 remain consistent in all directions.

[0052] The radius of the first region 210 is limited to 70%-95% of the radius of the vibrating diaphragm 200. This range is designed to optimize the balance between the effective vibrating area of ​​the diaphragm 200 and the stress dispersion area of ​​the corrugated structure 221. For example, when the radius of the first region 210 is close to 95%, the piezoelectric transducer can occupy a larger area to enhance the generation or reception efficiency of ultrasonic signals; while when its radius is close to 70%, it provides more space for the corrugated structure 221 to achieve a more significant increase in flexibility and stress dispersion effect. This dimensional parameter can be controlled through precise mask design and etching process.

[0053] The width of the corrugated structure 221 is limited to 5%-30% of the radius of the vibrating diaphragm 200. This width range complements the radius range of the first region 210, jointly determining the radial dimension of the second region 220. For example, a smaller width (e.g., 5%-15%) may be suitable for applications with relatively low requirements for flexibility enhancement but strict limitations on the overall device size; while a larger width (e.g., 20%-30%) provides stronger stress dispersion and more significant flexibility enhancement, suitable for applications requiring higher vibration amplitude or greater mechanical stress. This width parameter is also precisely controlled through fine micromachining processes.

[0054] The present application provides a basic symmetrical vibration framework for the piezoelectric micromechanical ultrasonic transducer by designing the vibrating diaphragm 200 as a circular thin-film structure and introducing a ring-shaped array of corrugated structures 221 surrounding the first region 210 within the second region 220. The crests and troughs of the corrugated structure 221 extend continuously along the circumference of the vibrating diaphragm 200 and are centrally symmetrically distributed, ensuring uniform distribution of mechanical stress and consistency of vibration response during vibration. Simultaneously, by precisely defining the radius of the first region 210 as 70%-95% of the radius of the vibrating diaphragm 200 and the width of the corrugated structure 221 as 5%-30% of the radius of the vibrating diaphragm 200, this application provides sufficient space for the corrugated structure 221 to fully utilize its function of reducing edge constraint stiffness and dispersing mechanical stress while ensuring the effective working area of ​​the piezoelectric transducer. This structural optimization allows the vibrating diaphragm 200 to maintain high sensitivity while effectively avoiding stress concentration, thereby improving the reliability and lifespan of the device.

[0055] In one specific implementation, the vibrating diaphragm 200 can be made of polycrystalline silicon and fabricated using microelectromechanical systems (MEMS) technology. First, a sacrificial layer is deposited on the substrate 100, and then a polycrystalline silicon layer is deposited on top to form the structural layer of the vibrating diaphragm 200. Using photolithography and dry etching processes, the vibrating diaphragm 200 is patterned into a circular thin-film structure, while simultaneously etching a ring-shaped array of corrugated structures 221 within the second region 220. The peaks and troughs of the corrugated structure 221 can be designed as sinusoidal or trapezoidal waveforms, ensuring circumferential continuity and overall central symmetry. For example, the radius of the first region 210 can be set to 80% of the radius of the vibrating diaphragm 200, while the width of the corrugated structure 221 is set to 20% of the radius of the vibrating diaphragm 200. Finally, by releasing the sacrificial layer, the vibrating diaphragm 200 is suspended above the cavity 500 on the substrate 100. The piezoelectric transducer is then integrated onto the surface of the first region 210.

[0056] Through the above technical solution, this application effectively solves the problem that the corrugated structure design in a circular thin film structure may be uneven or improperly sized, leading to insufficient reduction in edge constraint stiffness or uneven stress distribution. Specifically, the corrugated structure 221, with its annular array, continuous circumferential extension, and central symmetry distribution, combined with optimized size ratios, significantly reduces the edge constraint stiffness of the vibrating diaphragm 200 and achieves uniform dispersion of mechanical stress, thereby avoiding local stress concentration. This not only improves the vibration amplitude of the vibrating diaphragm 200 and enhances the sensitivity and performance of the piezoelectric micromechanical ultrasonic transducer, but also significantly improves the reliability and service life of the device.

[0057] In some embodiments, reference is made to the appendix. Figure 1 The piezoelectric transducer includes a piezoelectric layer 300 and electrode layers 400 disposed on the upper and lower sides of the piezoelectric layer 300. The orthogonal projection area of ​​the piezoelectric layer 300 on the vibrating diaphragm 200 accounts for 50%-70% of the total area of ​​the vibrating diaphragm 200, in order to reduce the residual stress between the piezoelectric layer 300 and the vibrating diaphragm 200 and reduce the risk of functional layer peeling.

[0058] The piezoelectric transducer is the core component for electroacoustic conversion, functioning to convert electrical signals into mechanical vibrations or vice versa. Specifically, the piezoelectric transducer can consist of a piezoelectric layer 300 and electrode layers 400 disposed on its upper and lower sides. Alternatively, the piezoelectric transducer can employ a structure with alternating layers of piezoelectric materials and electrodes to enhance the overall piezoelectric effect and transduction efficiency. The piezoelectric layer 300 is the functional core of the piezoelectric transducer, utilizing its piezoelectric effect to achieve energy conversion. The piezoelectric layer 300 can be fabricated from various piezoelectric materials, such as lead zirconate titanate (PZT) or aluminum nitride (AlN) piezoelectric ceramic thin film materials. Alternatively, piezoelectric polymer materials such as polyvinylidene fluoride (PVDF) can be used as the piezoelectric layer 300. The electrode layers 400 are used to apply a driving electric field to the piezoelectric layer 300 or to collect the charge signals generated by the piezoelectric layer 300. The electrode layer 400 is typically made of a conductive material, such as a thin film of metal like gold, platinum, aluminum, or copper, formed through microfabrication processes like sputtering, evaporation, or electroplating. Alternatively, the electrode layer 400 can also be made of a transparent conductive oxide material such as indium tin oxide (ITO). The proportion of the piezoelectric layer 300's projected area on the vibrating diaphragm 200 to 50%-70% of the total area of ​​the vibrating diaphragm 200 is designed to optimize the stress distribution between the piezoelectric layer 300 and the vibrating diaphragm 200, thereby reducing residual stress and lowering the risk of functional layer peeling. This area proportion can be precisely controlled during the deposition or etching process by precisely controlling the patterned mask size of the piezoelectric layer 300. For example, after the piezoelectric material is deposited, the lateral dimensions of the piezoelectric layer 300 are limited to the stated proportion using photolithography and etching processes.

[0059] The piezoelectric micromechanical ultrasonic transducer of this application comprises a vibrating diaphragm 200 including a first region 210 located in the center and a second region 220 surrounding it. The first region 210 has a planar structure, and the second region 220 has a corrugated structure 221 that alternately undulates radially along the vibrating diaphragm 200. A piezoelectric transducer assembly is disposed within the first region 210, and the assembly includes a piezoelectric layer 300 and electrode layers 400 disposed on the upper and lower sides of the piezoelectric layer 300. When an alternating electric field is applied between the electrode layers 400, the piezoelectric layer 300 undergoes the inverse piezoelectric effect, producing periodic deformation, which in turn drives the first region 210 it covers to produce bending vibration, thereby emitting ultrasonic waves into the surrounding medium. Conversely, when ultrasonic waves act on the vibrating diaphragm 200, causing the first region 210 to vibrate, the piezoelectric layer 300 undergoes the direct piezoelectric effect, generating charges. These charges are collected by the electrode layers 400 and converted into electrical signals. To address the risk of functional layer delamination due to excessive residual stress between the piezoelectric layer 300 and the vibrating diaphragm 200, this application proposes a solution that precisely controls the projected area of ​​the piezoelectric layer 300 on the vibrating diaphragm 200, ensuring it occupies 50%-70% of the total area of ​​the diaphragm 200. This specific area ratio aims to optimize the stress distribution between the piezoelectric layer 300 and the vibrating diaphragm 200. If the coverage area of ​​the piezoelectric layer 300 is too small, it may lead to insufficient ultrasonic transduction efficiency; if the coverage area is too large, it may cause excessive stress concentration at the interface between the piezoelectric layer 300 and the vibrating diaphragm 200. Especially during device operation, the edge region of the vibrating diaphragm 200 experiences higher stress, and an excessively large piezoelectric layer coverage area will exacerbate this stress, thereby increasing the risk of functional layer delamination. By limiting the coverage area of ​​the piezoelectric layer 300 to within the range of 50%-70%, this scheme effectively balances transduction efficiency and stress management, avoiding stress concentration problems caused by improper area, thereby significantly reducing the residual stress between the piezoelectric layer 300 and the vibrating diaphragm 200. Furthermore, the corrugated structure 221 of the second region 220 of the vibrating diaphragm 200 is used to reduce the edge constraint stiffness of the diaphragm 200 and disperse mechanical stress. Therefore, by optimizing the coverage area of ​​the piezoelectric layer 300 to reduce residual stress, combined with the stress-dispersing effect of the corrugated structure 221, a more comprehensive stress management mechanism is constructed. This combination enables the entire vibrating diaphragm 200 to withstand greater vibration amplitude during operation while maintaining structural stability, effectively improving the reliability and service life of the device.

[0060] In one specific implementation, the piezoelectric transducer can consist of a 0.5-micrometer-thick PZT thin film as the piezoelectric layer 300, with a 100-nanometer-thick platinum (Pt) thin film deposited on its upper and lower sides as electrode layers 400 using magnetron sputtering. This piezoelectric transducer is precisely integrated into the center of the first region 210 of the vibrating diaphragm 200. To ensure that the projected area of ​​the piezoelectric layer 300 on the vibrating diaphragm 200 accounts for 50%-70% of the total area of ​​the diaphragm 200, the pattern of the piezoelectric layer 300 can be defined using photolithography after PZT film deposition. Subsequently, unwanted PZT material can be precisely removed using reactive ion etching (RIE), thereby limiting the lateral dimensions of the piezoelectric layer 300 within a preset range. For example, if the total area of ​​the vibrating diaphragm 200 is 10,000 square micrometers, the area of ​​the piezoelectric layer 300 can be designed to be 6,000 square micrometers to ensure its coverage ratio is within the optimized range of 50%-70%.

[0061] Through the above technical solution, this application effectively solves the risk of functional layer delamination caused by excessive residual stress between the piezoelectric layer and the vibrating diaphragm. By controlling the orthogonal projection area of ​​the piezoelectric layer 300 on the vibrating diaphragm 200 within a specific range of 50%-70%, the stress distribution between the piezoelectric layer 300 and the vibrating diaphragm 200 can be significantly optimized, avoiding stress concentration and thus greatly reducing residual stress. This directly reduces the risk of functional layer delamination and improves the structural stability and reliability of the piezoelectric micromechanical ultrasonic transducer. In addition, this solution effectively extends the service life of the device while maintaining ultrasonic transduction performance. Combined with the mechanical stress dispersion capability provided by the corrugated structure 221 of the vibrating diaphragm 200, this solution further enhances the fatigue resistance and long-term stability of the entire device.

[0062] In some embodiments, the thickness of the vibrating diaphragm 200 is 3-8 μm.

[0063] The thickness of the vibrating diaphragm 200 is a key parameter for its mechanical properties. This thickness can be precisely controlled according to the specific manufacturing process. For example, the desired thickness can be achieved by controlling parameters in the thin film deposition process, such as the deposition time, temperature, and precursor flow rate in chemical vapor deposition (CVD) or atomic layer deposition (ALD). Alternatively, a thicker initial layer can be precisely thinned to the range of 3-8 μm using sophisticated etching techniques, such as deep reactive ion etching (DRIE) or wet etching. This thickness range is designed to balance the flexibility and mechanical strength of the vibrating diaphragm 200, enabling it to withstand the stresses generated during operation while achieving effective vibration.

[0064] The solution of this application achieves synergy with the structure of the aforementioned piezoelectric micromechanical ultrasonic transducer by limiting the thickness of the vibrating diaphragm 200 to the range of 3-8 μm. In the aforementioned piezoelectric micromechanical ultrasonic transducer, the vibrating diaphragm 200 includes a first region 210 with a planar structure located in the center and a second region 220 surrounding the first region 210, which has a corrugated structure 221 that is alternately undulating along the radial direction of the vibrating diaphragm 200. The piezoelectric transducer assembly is disposed within the first region 210 and drives the vibrating diaphragm 200 to vibrate through the piezoelectric effect. The corrugated structure 221 itself is used to reduce the edge constraint stiffness of the vibrating diaphragm 200 and disperse mechanical stress. Based on this, by optimizing the overall thickness of the vibrating diaphragm 200 to 3-8 μm, it is ensured that the vibrating diaphragm 200 maintains sufficient flexibility to achieve large amplitude vibration while also possessing sufficient mechanical strength to resist the dynamic stress generated during vibration. Too small a thickness may lead to insufficient diaphragm strength, making it prone to breakage or stress concentration; while too large a thickness will increase the stiffness of the diaphragm, suppress the vibration amplitude, and thus reduce the sensitivity of the transducer. Therefore, the setting of this thickness range allows the vibrating diaphragm 200 to achieve the best balance between high sensitivity and high reliability, effectively solving the problems of limited vibration amplitude and mechanical stress concentration.

[0065] In some embodiments, the corrugated structure 221 has a sinusoidal or trapezoidal cross-sectional shape in the radial direction of the vibrating diaphragm 200 to increase the flexibility of the vibrating diaphragm 200 and enhance the vibration amplitude.

[0066] Specifically, the cross-sectional shape of the corrugated structure 221 in the radial direction of the vibrating diaphragm 200 refers to the cross-sectional profile of the corrugated structure 221 perpendicular to its circumferential direction (i.e., along the radial direction of the vibrating diaphragm 200). This cross-sectional shape directly determines the geometric characteristics of the corrugation, thereby affecting its mechanical flexibility and stress distribution. Besides the sinusoidal or trapezoidal wave shape defined in this application, the radial cross-sectional shape of the corrugated structure can also be a triangular wave shape, a rectangular wave shape, or a composite wave shape, etc., but these shapes may not be as optimized as sinusoidal or trapezoidal waves in terms of flexibility enhancement and stress dispersion. A sinusoidal wave shape refers to the radial cross-sectional profile of the corrugated structure 221 exhibiting a continuous, smooth sinusoidal curve. This shape is characterized by a continuous change in curvature, without sharp corners, which helps avoid stress concentration and provides uniform flexibility. A trapezoidal wave shape refers to the radial cross-sectional profile of the corrugated structure 221 exhibiting a trapezoidal shape composed of a flat top, sloping sidewalls, and a flat bottom. This shape is characterized by relatively flat areas and sloping transition areas, which can provide a certain degree of flexibility while dispersing stress through the flat areas and providing a certain degree of structural support.

[0067] The solution of this application optimizes the mechanical properties of the corrugated structure 221 by defining the radial cross-sectional shape of the corrugated structure 221 in the second region 220 of the piezoelectric micromechanical ultrasonic transducer as a sinusoidal or trapezoidal wave shape. Driven by the piezoelectric transducer, the diaphragm 200 vibrates. As the edge portion of the diaphragm 200, the optimization of the cross-sectional shape of the corrugated structure 221 is crucial for improving overall vibration performance. When the corrugated structure 221 adopts a sinusoidal wave shape, its smooth and continuous curve characteristics allow the stress to be evenly distributed along the curved surface of the corrugations when the diaphragm 200 is bent under stress, avoiding stress concentration points that may occur in traditional corrugated structures, thereby effectively increasing the overall flexibility of the diaphragm 200. This increased flexibility allows the diaphragm 200 to produce greater deformation under the same driving force, thereby increasing the vibration amplitude. When the corrugated structure 221 adopts a trapezoidal wave shape, its flat and sloping transition regions work together. The flat regions help to disperse mechanical stress, while the sloping regions provide the necessary flexibility. This structural design allows the vibrating diaphragm 200 to achieve a significant increase in flexibility while maintaining a certain level of structural stability, which also helps to achieve a larger vibration amplitude. The piezoelectric micromechanical ultrasonic transducer described above includes a substrate 100 and a vibrating diaphragm 200 supported on the substrate 100. The vibrating diaphragm 200 includes a first region 210 located in the middle and a second region 220 arranged around the first region 210. The first region 210 has a planar structure, and the second region 220 has a corrugated structure 221 that is alternately distributed along the radial direction of the vibrating diaphragm 200. The corrugated structure 221 is used to reduce the edge constraint stiffness of the vibrating diaphragm 200 and disperse mechanical stress. A piezoelectric transducer assembly is disposed on the vibrating diaphragm 200, and the piezoelectric transducer assembly is disposed in the first region 210. In this application, by optimizing the cross-sectional shape of the corrugated structure 221, the corrugated structure 221 further enhances the flexibility of the vibrating diaphragm 200 on the basis of reducing the edge constraint stiffness and dispersing mechanical stress. This enhanced flexibility, combined with the original stress-dispersing function of the corrugated structure 221, enables the vibrating diaphragm 200 to achieve a larger vibration amplitude with less internal stress during operation. This effectively solves the problem of difficulty in balancing sensitivity improvement and stress concentration relief in the prior art, thereby improving the reliability of the device.

[0068] As a specific implementation, the cross-sectional shape of the aforementioned corrugated structure 221 in the radial direction of the vibrating diaphragm 200 can be designed as a sinusoidal wave shape. For example, in microfabrication processes, a series of smoothly transitioning peaks and troughs can be formed by precisely controlling the etching depth and sidewall profile, with a cross-sectional profile approximating a sine function curve. This sinusoidal corrugated structure 221 can be fabricated using polycrystalline silicon material through surface microfabrication techniques, for example, depositing polycrystalline silicon on a sacrificial layer, then releasing the sacrificial layer to form a suspended structure, and refining the corrugated shape through subsequent etching processes. Alternatively, the cross-sectional shape of the aforementioned corrugated structure 221 in the radial direction of the vibrating diaphragm 200 can also be designed as a trapezoidal wave shape. For example, during fabrication, a trapezoidal cross-section can be constructed by first forming sidewalls with a certain slope through two or more etching steps, and then forming flat platforms at the top and bottom. This trapezoidal wave corrugated structure 221 can also be fabricated using polycrystalline silicon material. For example, by anisotropically etching the silicon layer to form sidewalls with specific angles, and then by deposition and patterning processes to form flat structures at the top and bottom. The outer ring corrugations can be continuous ring array structures such as sine waves and trapezoidal waves.

[0069] By employing the aforementioned technical solution, the radial cross-sectional shape of the corrugated structure 221 is defined as either a sinusoidal or trapezoidal wave shape, significantly increasing the flexibility of the diaphragm 200. The smooth transition characteristic of the sinusoidal wave shape effectively reduces stress concentration points, while the trapezoidal wave shape better disperses mechanical stress through its flat areas and provides structural support. This optimized design not only further reduces the edge constraint stiffness of the diaphragm 200, but more importantly, while maintaining or improving stress dispersion capabilities, it significantly enhances the overall flexibility of the diaphragm 200. This allows the piezoelectric micromechanical ultrasonic transducer to generate a larger vibration amplitude under the same driving conditions, effectively overcoming the limitations of existing corrugated structures in improving flexibility and vibration amplitude. Consequently, it improves the device's sensitivity and energy conversion efficiency, while avoiding reliability risks caused by stress concentration and extending the device's service life.

[0070] In some embodiments, reference is made to the appendix. Figure 1 The substrate 100 is provided with a cavity 500, and the entire first region 210 is suspended above the cavity 500 as a suspended membrane.

[0071] Cavity 500 refers to a recess or through-structure of a specific shape formed inside or on the surface of substrate 100. The main function of cavity 500 is to provide a free vibration space without mechanical contact for the first region 210 of the vibrating diaphragm 200, thereby avoiding direct support and rigid constraint of the first region 210 by substrate 100. Cavity 500 can be formed using various microfabrication techniques. For example, anisotropic wet etching techniques can be used, such as selective etching of the silicon substrate using potassium hydroxide (KOH) or tetramethylammonium hydroxide (TMAH) solutions; or, deep reactive ion etching (DRIE) techniques can be used to precisely etch the cavity structure of the desired shape and depth onto the silicon substrate. Alternatively, a sacrificial layer etching process can be used, where a layer of selectively removable sacrificial material is first deposited on the substrate, followed by the deposition of substrate material, and finally the sacrificial layer is etched away to form the cavity.

[0072] "The entire first region 210 is suspended above the cavity 500" means that the entire first region 210 of the vibrating diaphragm 200 is completely detached from the direct mechanical support of the substrate 100, and instead floats above the cavity 500, forming an independent, freely bendable, and vibrating thin-film structure. This suspended configuration ensures that when the first region 210 is driven by the piezoelectric transducer, its vibration process is not mechanically hindered or constrained by the substrate 100, thereby enabling a larger vibration amplitude. Simultaneously, this structure also helps to evenly distribute the mechanical stress generated during vibration, avoiding localized stress concentration, thereby improving the reliability and lifespan of the device. The methods for achieving this suspended structure include, but are not limited to: forming a cavity 500 on the substrate 100 in advance through an etching process, and then growing or depositing the material of the vibrating diaphragm 200 above the cavity 500 through thin film deposition technology, so that the boundary of the first region 210 is precisely aligned with the edge of the cavity 500, thereby making the first region 210 completely cover and suspended above the cavity 500; or, a sacrificial layer can be deposited on the substrate 100 first, and then the material constituting the vibrating diaphragm 200 can be deposited on it to form the first region 210, and finally the sacrificial layer below can be removed by selective etching process, thereby forming the cavity 500 below the first region 210 and achieving its suspension.

[0073] This application addresses the issue of direct constraint from the substrate 100 on the first region 210 of the vibrating diaphragm 200 during vibration by optimizing the structural relationship between the substrate 100 and the vibrating diaphragm 200. Specifically, the substrate 100 is designed with a cavity 500, creating a specific open space within the substrate 100. The presence of this cavity 500 provides the necessary unconstrained environment for the first region 210 of the vibrating diaphragm 200, preventing mechanical contact with the substrate 100 during vibration and thus avoiding rigid constraints imposed by the substrate 100 on the first region 210. Furthermore, the entire first region 210 is cleverly suspended above the cavity 500 as a suspended membrane. This means that the first region 210, as a whole, is completely suspended above the cavity 500, forming an independent, freely movable thin-film structure. This suspended design significantly reduces the edge constraint stiffness of the first region 210, enabling the piezoelectric transducer to achieve bending vibrations with larger amplitudes when driving the first region 210. Meanwhile, since the first region 210 is no longer directly supported by the substrate 100, the mechanical stress generated during vibration is more effectively dispersed, avoiding local stress accumulation, thereby improving the device's sensitivity and long-term reliability. Combining the overall structure of the piezoelectric micromechanical ultrasonic transducer described above, the vibrating diaphragm 200 includes a planar first region 210 and a second region 220 with a corrugated structure 221, with the piezoelectric transducer assembly disposed within the first region 210. By suspending the first region 210 above the cavity 500, the piezoelectric transducer assembly can more efficiently convert electrical energy into mechanical vibration energy, driving the first region 210 to produce a larger displacement. Simultaneously, the corrugated structure 221 of the second region 220 itself has the function of reducing edge constraint stiffness and dispersing mechanical stress. When the first region 210 is suspended through the cavity 500, it works together with the second region 220 to further enhance the flexibility of the entire vibrating diaphragm 200. This allows the vibrating diaphragm 200 to vibrate with a larger amplitude and distributes the stress generated during vibration more evenly across the entire diaphragm structure. This improves ultrasonic transduction efficiency while effectively ensuring the structural integrity and operational stability of the device. This synergistic effect enables the piezoelectric micromechanical ultrasonic transducer to achieve high sensitivity and high sound pressure output while significantly reducing the risk of fatigue failure due to stress concentration.

[0074] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] The above descriptions are merely some embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A piezoelectric micromechanical ultrasonic transducer, comprising a substrate (100) and a vibrating diaphragm (200) supported on the substrate (100), characterized in that, The vibrating diaphragm (200) includes a first region (210) located in the middle and a second region (220) surrounding the first region (210); the first region (210) is a planar structure; the second region (220) has a corrugated structure (221) that is alternately distributed radially along the vibrating diaphragm (200); the corrugated structure (221) is used to reduce the edge constraint stiffness of the vibrating diaphragm (200) and disperse mechanical stress; a piezoelectric transducer is provided on the vibrating diaphragm (200), and the piezoelectric transducer is disposed in the first region (210).

2. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The vibrating diaphragm (200) is a circular thin film structure.

3. The piezoelectric micromechanical ultrasonic transducer according to claim 2, characterized in that, The corrugated structure (221) is a ring array structure arranged around the first region (210); the crests and troughs of the corrugated structure (221) extend continuously along the circumference of the vibrating diaphragm (200) in the second region (220), and the corrugated structure (221) is centrally symmetrically distributed in the second region (220).

4. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The piezoelectric transducer includes a piezoelectric layer (300), the orthogonal projection area of ​​the piezoelectric layer (300) on the vibrating diaphragm (200) accounts for 50%-70% of the total area of ​​the vibrating diaphragm (200).

5. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The thickness of the vibrating diaphragm (200) is 3-8 μm.

6. The piezoelectric micromechanical ultrasonic transducer according to claim 2, characterized in that, The radius of the first region (210) is 70%-95% of the radius of the vibrating diaphragm (200).

7. The piezoelectric micromechanical ultrasonic transducer according to claim 6, characterized in that, The width of the corrugated structure (221) is 5%-30% of the radius of the vibrating diaphragm (200).

8. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The corrugated structure (221) has a sinusoidal or trapezoidal cross-sectional shape in the radial direction of the vibrating diaphragm (200).

9. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that, The substrate (100) is provided with a cavity (500), and the entire first region (210) is suspended above the cavity (500) as a membrane.

10. The piezoelectric micromechanical ultrasonic transducer according to claim 4, characterized in that, The piezoelectric transducer also includes electrode layers (400) disposed on the upper and lower sides of the piezoelectric layer (300).

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