Piezoelectric micromechanical ultrasonic transducer, ultrasonic cleaning device and application thereof

Abstract

The invention discloses a piezoelectric micromechanical ultrasonic transducer, an ultrasonic cleaning device and application of the piezoelectric micromechanical ultrasonic transducer and the ultrasonic cleaning device, and belongs to the technical field of actuator application. The piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device comprises a piezoelectric micromechanical ultrasonic transducer array, a phase control circuit board, a display screen, a control button, a power source and a shell, and meanwhile, the invention further provides a piezoelectric micromechanical ultrasonic transducer unit structure and a piezoelectric micromechanical ultrasonic transducer array used for the piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device. Phase control of the piezoelectric micromechanical ultrasonic transducer array unit is achieved through the phase control circuit board, ultrasonic sound gathering is achieved, and therefore cleaning work is achieved in a focused area. The ultrasonic cleaning device for the piezoelectric micro-mechanical ultrasonic transducer can achieve local cleaning of a micron-order area and protect the structure of a non-cleaning area, and is particularly suitable for the field of micro-nano manufacturing.

Description

Technical Field

[0001] The present invention particularly relates to a piezoelectric micromechanical ultrasonic transducer, an ultrasonic cleaning device and applications thereof, and belongs to the technical field of actuator application. Background Art

[0002] The core of the transducer of the existing ultrasonic cleaning device is a bulk piezoelectric ultrasonic transducer made of bulk piezoelectric material. Bulk piezoelectric ultrasonic transducers have a large volume and are usually used for cleaning the entire part. It is difficult to achieve local cleaning, including cleaning of micron-level areas. For example, there is dirt on a small area of ​​the wafer, but the surrounding area is difficult to withstand the cavitation effect of ultrasonic waves, which requires an ultrasonic cleaning device that can achieve local small area cleaning.

[0003] Piezoelectric micromachined ultrasonic transducers (PMUT) are ultrasonic transmitting devices developed from micro-electromechanical systems and micro-nano processing technologies. They have great advantages such as small size, high integration, low power consumption, low driving voltage, and the ability to achieve high frequencies. Piezoelectric micromachined ultrasonic transducers can be designed in the form of arrays, which can not only increase the output sound pressure of the piezoelectric micromachined ultrasonic transducer, but also achieve line focusing and point focusing of the emitted sound waves by controlling the phase of different units, so that the focused area can obtain higher sound intensity. Summary of the invention

[0004] The main purpose of the present invention is to provide a piezoelectric micromechanical ultrasonic transducer, an ultrasonic cleaning device and applications thereof, so as to overcome the deficiencies in the prior art.

[0005] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0006] A first aspect of an embodiment of the present invention provides a piezoelectric micromechanical ultrasonic transducer, comprising a substrate and a piezoelectric film, wherein the substrate has a resonant cavity, the piezoelectric film is arranged on the substrate along the z direction and covers the resonant cavity, and a stress release hole structure is also provided on the outer peripheral edge of the piezoelectric film, and the stress release hole structure is connected to the resonant cavity.

[0007] The second aspect of the embodiment of the present invention provides a piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device for ultrasonic cleaning of micron-sized surfaces. The piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device includes: a piezoelectric micromechanical ultrasonic transducer probe and a phase-controlled circuit board. The piezoelectric micromechanical ultrasonic transducer probe includes a plurality of the piezoelectric micromechanical ultrasonic transducers, and the plurality of the piezoelectric micromechanical ultrasonic transducers are arranged in an array. The plurality of the piezoelectric micromechanical ultrasonic transducers are connected to the phase-controlled circuit board through a multi-channel electrical signal. The piezoelectric micromechanical ultrasonic transducer probe cooperates with the phase-controlled circuit board to achieve focusing of sound waves through phase control.

[0008] A third aspect of an embodiment of the present invention provides a method for ultrasonic cleaning of a micron-sized surface, comprising:

[0009] The product to be cleaned is placed in the cleaning liquid, and the acoustic focus of the piezoelectric micromechanical ultrasonic transducer is controlled on the surface of the area to be cleaned of the product to be cleaned, and the surface of the area to be cleaned of the product to be cleaned is cleaned, wherein the area to be cleaned is of micron size.

[0010] Compared with the prior art, the advantages of the present invention include:

[0011] 1) A piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device provided in an embodiment of the present invention can achieve local cleaning of the object to be cleaned, thereby protecting other parts from being affected by ultrasonic waves;

[0012] 2) A piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device provided in an embodiment of the present invention can focus ultrasonic waves in a micrometer-level area to achieve cleaning work in a small area;

[0013] 3) A piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device provided in an embodiment of the present invention has the characteristics of small size, portability and built-in power supply, and can support handheld operation and bracket-fixed operation;

[0014] 4) An embodiment of the present invention provides a piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device, wherein the actuator piezoelectric micromechanical ultrasonic transducer is a regular quadrilateral structure with a high filling factor, which effectively reduces the required probe volume, and by providing stress release holes to improve the film amplitude sensitivity of the piezoelectric micromechanical ultrasonic transducer, it is possible to achieve a higher emission sound pressure and achieve excellent cleaning efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 , Figure 2 It is a schematic diagram of the assembly of a piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device provided in a typical implementation case of the present invention;

[0016] Figure 3 It is a schematic diagram of a planar structure of a piezoelectric micromechanical ultrasonic transducer probe provided in a typical implementation case of the present invention;

[0017] Figure 4 It is a schematic diagram of the array arrangement details of a piezoelectric micromechanical ultrasonic transducer probe provided in a typical implementation case of the present invention;

[0018] Figure 5 is a top view of a piezoelectric micromechanical ultrasonic transducer provided in a typical implementation case of the present invention;

[0019] Figure 6 is a cross-sectional view of a piezoelectric micromechanical ultrasonic transducer provided in a typical implementation case of the present invention;

[0020] Figure 7 It is a schematic diagram of a framework of a phase-controlled circuit board provided in a typical implementation case of the present invention;

[0021] Figure 8 It is a schematic diagram of the principle of achieving acoustic focusing by phase control provided in a typical implementation case of the present invention;

[0022] Fig. 9 is a graph showing the relationship between the resonant frequency and characteristic dimensions of a piezoelectric micromechanical ultrasonic transducer provided in a typical implementation case of the present invention;

[0023] Fig.10 This is a comparison diagram of the amplitude sensitivity of a piezoelectric micromechanical ultrasonic transducer with a stress release hole and a traditional square piezoelectric micromechanical ultrasonic transducer without a stress release hole provided in a typical implementation case of the present invention;

[0024] Fig.11 It is a schematic diagram of cleaning a sample using a piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device provided in a typical implementation case of the present invention. DETAILED DESCRIPTION

[0025] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0026] A first aspect of an embodiment of the present invention provides a piezoelectric micromechanical ultrasonic transducer, comprising a substrate and a piezoelectric film, wherein the substrate has a resonant cavity, the piezoelectric film is arranged on the substrate along the z direction and covers the resonant cavity, and a stress release hole structure is also provided on the outer peripheral edge of the piezoelectric film, and the stress release hole structure is connected to the resonant cavity.

[0027] Furthermore, the stress release hole structure is arranged on the outer peripheral edge of the square piezoelectric film.

[0028] Furthermore, the resonant cavity and the piezoelectric film are both regular quadrilateral structures, the stress release hole structure includes four stress release holes, and the four stress release holes are respectively arranged on the four sides of the piezoelectric film. It can be understood that the orthographic projection figures formed by the resonant cavity and the piezoelectric film along the z direction are both regular quadrilaterals.

[0029] Furthermore, the stress release hole is arranged in a middle area of ​​an edge of the piezoelectric film where the stress release hole is located.

[0030] Furthermore, the stress release hole is a rectangular hole.

[0031] Furthermore, in the orthographic projection figure formed along the z direction, the geometric center of any of the stress release holes is located on the midline of the edge of the piezoelectric film where the stress release hole is located.

[0032] Furthermore, the long side of the rectangular stress release hole is parallel to the side of the piezoelectric film where the rectangular stress release hole is located.

[0033] Furthermore, the stress release hole structure is a rotationally symmetrical structure.

[0034] Furthermore, the piezoelectric film includes a top electrode, a piezoelectric layer, a bottom electrode and an elastic layer which are stacked in sequence along the z direction, the elastic layer is stacked on the substrate, the geometric centers of the orthographic projection figures of the top electrode, the piezoelectric layer, the bottom electrode, the elastic layer and the resonant cavity along the z direction coincide with each other, the orthographic projection areas of the piezoelectric layer and the bottom electrode along the z direction are equal, the orthographic projection area of ​​the elastic layer along the z direction is greater than the orthographic projection area of ​​the resonant cavity along the z direction, the orthographic projection areas of the piezoelectric layer and the electrode layer along the z direction are greater than the orthographic projection area of ​​the top electrode along the z direction.

[0035] Unless otherwise specified, the shapes and characteristic relationships of the piezoelectric micromechanical ultrasonic transducer, piezoelectric film, and the various structural layers, stress release holes, etc. contained in the piezoelectric film in the embodiments of the present invention are all defined in the orthographic projection figures formed along the z direction, which is the z-axis direction of the three-dimensional coordinate system.

[0036] The second aspect of the embodiment of the present invention provides a piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device for ultrasonic cleaning of micron-sized surfaces. The piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device includes: a piezoelectric micromechanical ultrasonic transducer probe and a phase-controlled circuit board. The piezoelectric micromechanical ultrasonic transducer probe includes a plurality of the piezoelectric micromechanical ultrasonic transducers, and the plurality of the piezoelectric micromechanical ultrasonic transducers are arranged in an array. The plurality of the piezoelectric micromechanical ultrasonic transducers are connected to the phase-controlled circuit board through a multi-channel electrical signal. The piezoelectric micromechanical ultrasonic transducer probe cooperates with the phase-controlled circuit board to achieve focusing of sound waves through phase control.

[0037] Furthermore, the phase-controlled circuit board includes a control circuit, an oscillation circuit, a phase-locked loop circuit, a power amplifier circuit, and a display circuit. The control circuit is connected to the oscillation circuit, the oscillation circuit is also connected to the phase-locked loop circuit, the phase-locked loop circuit is also connected to the power amplifier circuit, the display circuit is also connected to the control circuit, and the power amplifier circuit is connected to the piezoelectric micromechanical ultrasonic transducer.

[0038] In a more specific implementation, the piezoelectric micromechanical ultrasonic transducer also includes: a shell and an acoustic impedance matching structure, wherein the acoustic impedance matching structure, the piezoelectric micromechanical ultrasonic transducer probe and the phased circuit board are arranged inside the shell, the acoustic impedance matching structure, the piezoelectric micromechanical ultrasonic transducer probe and the phased circuit board are arranged in sequence along the z direction, and the acoustic impedance matching structure is formed of an acoustic impedance matching material.

[0039] Furthermore, a first surface of the acoustic impedance matching structure facing away from the piezoelectric micromechanical ultrasonic transducer probe is parallel to a second surface of the piezoelectric micromechanical ultrasonic transducer probe facing the acoustic impedance matching structure, and geometric centers of the first surface and the second surface coincide.

[0040] In a more specific implementation, the piezoelectric micromechanical ultrasonic transducer also includes a PCB packaging board, which is arranged between the piezoelectric micromechanical ultrasonic transducer probe and the phase-controlled circuit board, and the piezoelectric micromechanical ultrasonic transducer probe and the phase-controlled circuit board are connected via the PCB packaging board.

[0041] In a more specific implementation, the piezoelectric micromechanical ultrasonic transducer further includes a display screen and an operation button, and the display screen and the operation button are electrically connected to the phase-controlled circuit board.

[0042] A third aspect of an embodiment of the present invention provides a method for ultrasonic cleaning of a micron-sized surface, comprising:

[0043] The product to be cleaned is placed in the cleaning liquid, and the acoustic focus of the piezoelectric micromechanical ultrasonic transducer is controlled on the surface of the area to be cleaned of the product to be cleaned, and the surface of the area to be cleaned of the product to be cleaned is cleaned, wherein the area to be cleaned is of micron size.

[0044] Furthermore, the piezoelectric micromechanical ultrasonic transducer is controlled by the phase-controlled circuit board, and the phase-controlled delay time of each piezoelectric micromechanical ultrasonic transducer is determined by formula (1):

[0045]

[0046] A piezoelectric micromechanical ultrasonic transducer located at the geometric center of the XY plane in the piezoelectric micromechanical ultrasonic transducer array is set as a central unit, and its phase delay is 0,

[0047] The acoustic focusing point is set to be located at the z-direction center axis position of the central unit, d is the z-direction distance between the acoustic focusing point and the geometric center of the piezoelectric film of the central unit, s is the distance between the z-direction center axis of the remaining piezoelectric micromechanical ultrasonic transducers except the central unit and the z-direction center axis of the central unit, and v is the speed of sound in the cleaning fluid.

[0048] The technical solution, its implementation process and principles will be further explained as follows. Unless otherwise specified, the PCB packaging board, oscillation circuit, phase-locked loop circuit, power amplifier circuit, display circuit and control circuit involved in the embodiments of the present invention are all known in the art, and the circuit structure and specific configuration structure of each circuit are also known in the art. They can all be purchased commercially and their specific structures are not limited here. In addition, the materials and processing techniques of the top electrode, piezoelectric layer, bottom electrode, elastic layer, lead and pad involved in the embodiments of the present invention are also known in the art and are not specifically limited here.

[0049] In a more specific implementation, see Figure 1 and Figure 2A piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device comprises an acoustic impedance matching structure 1-1, a piezoelectric micromechanical ultrasonic transducer probe 1-2, a PCB packaging board 1-3, a phase-controlled circuit board 1-4, a display screen 1-5, a control button 1-6, a power supply 1-8 and a shell 1-7, wherein the acoustic impedance matching structure 1-1, the piezoelectric micromechanical ultrasonic transducer probe 1-2, the PCB packaging board 1-3, the phase-controlled circuit board 1-4 and the power supply 1-8 are assembled inside the shell 1-7, and the acoustic impedance matching structure 1-1, a piezoelectric micromechanical ultrasonic transducer probe 1-2, a PCB packaging board 1-3, a phase-controlled circuit board 1-4, and a power supply 1-8 are arranged in sequence along the z direction. The piezoelectric micromechanical ultrasonic transducer probe 1-2 is connected to the phase-controlled circuit board 1-4 via the PCB packaging board 1-3, and the phase-controlled circuit board 1-4 is also connected to the power supply 1-8. The display screen 1-5 and the control button 1-6 are assembled on the outer surface of the housing 1-7, and the display screen 1-5 and the control button 1-6 are also connected to the phase-controlled circuit board 1-4.

[0050] Specifically, the acoustic impedance matching structure 1-1 is assembled at the front end of the shell 1-7 and is located between the piezoelectric micromechanical ultrasonic transducer probe 1-2 and the shell 1-7. More specifically, the acoustic impedance matching structure 1-1 is formed by filling the acoustic impedance matching material between the piezoelectric micromechanical ultrasonic transducer probe 1-2 and the shell 1-7, and a part of the acoustic impedance matching structure 1-1 is also exposed from the front end face of the shell 1-7 and can directly contact the outside world. The acoustic impedance matching structure 1-1 can isolate the piezoelectric micromechanical ultrasonic transducer probe 1-2 from the external environment, while reducing the acoustic loss at the interface between the cleaning liquid and the acoustic impedance matching structure 1-1, and protecting the internal core transducer element. More specifically, the first surface of the acoustic impedance matching structure 1-1 facing away from the piezoelectric micromechanical ultrasonic transducer probe 1-2 (i.e., the plane where the acoustic impedance matching structure 1-1 is in direct contact with the outside world) needs to be parallel to the second surface of the piezoelectric micromechanical ultrasonic transducer probe 1-2 facing the acoustic impedance matching structure 1-1 (i.e., the positive (+z direction) surface of the piezoelectric micromechanical ultrasonic transducer probe 1-2), and the geometric centers of the positive projections of the first surface and the second surface along the z direction overlap.

[0051] Specifically, the phase-controlled circuit board 1-4 is mounted at the middle plane position of the housing 1-7, specifically at the plane position of y=0 in the housing, and the power supply 1-8 is mounted between the phase-controlled circuit board 1-4 and the housing 1-7 along the z direction. More specifically, the piezoelectric micromechanical ultrasonic transducer probe 1-2 is fixed to the PCB packaging board 1-3 by the pad located on its back side (-z direction) and establishes a multi-channel electrical signal connection. Such a packaging solution can reduce the volume of the PCB packaging board 1-3, and ultimately reduce the size of the required packaging housing.

[0052] Specifically, the piezoelectric micromechanical ultrasonic transducer probe 1-2 includes a plurality of piezoelectric micromechanical ultrasonic transducers 3-1, and the plurality of piezoelectric micromechanical ultrasonic transducers 3-1 are arranged in a regular quadrilateral array. The square piezoelectric micromechanical ultrasonic transducers are arranged to form a square array with a higher effective filling rate. The array can also be described as a regular quadrilateral array arrangement. The combined effect of the two constitutes a higher effective filling rate. Please refer to Figure 3 , Figure 4 The piezoelectric micromechanical ultrasonic transducer probe 1-2 is composed of piezoelectric micromechanical ultrasonic transducers 3-1 arranged in an array structure; the effective filling rate of the circular and square piezoelectric micromechanical ultrasonic transducers with a Pitch (center distance) of 250 μm and a Space (unit spacing) of 100 μm is shown in Table 1.

[0053] Table 1 Effective filling rate of circular and square piezoelectric micromechanical ultrasonic transducers

[0054]

[0055]

[0056] For details, please refer to Figure 5 and Figure 6 The piezoelectric micromechanical ultrasonic transducer includes a substrate 5-11, a piezoelectric film, a passivation layer 5-7, two groups of leads 5-1, 5-8, two groups of TSV through holes 5-9, 5-13 and two groups of pads 5-10, 5-14, wherein the piezoelectric film is arranged on the first surface (+z surface) of the substrate 5-11 along the z direction, the first surface of the substrate 5-11 has a resonant cavity 5-12, the piezoelectric film covers the resonant cavity, and the piezoelectric film is also provided with a stress release hole structure, and the stress release hole structure is connected to the resonant cavity 5-12. A passivation layer 5-7 is covered on the piezoelectric film, a passivation layer window is opened on the passivation layer 5-7, the leads 5-1 and 5-8 are electrically connected to the piezoelectric film through the passivation layer window, the pad 5-10 is arranged on the second surface (-z surface) of the substrate 5-11, two groups of pads 5-10 and 5-14 and two groups of leads 5-1 and 5-8 are electrically connected through two groups of TSV through holes 5-9 and 5-13 respectively, and the piezoelectric micromechanical ultrasonic transducer is fixed to the PCB packaging board 1-3 by the pads 5-10 and 5-14 at the bottom of the substrate 5-11 and establishes a multi-channel electrical signal connection.

[0057] Specifically, the piezoelectric film includes an elastic layer 5-2, a bottom electrode 5-3, a piezoelectric layer 5-5, and a top electrode 5-6 which are stacked in sequence on a substrate 5-11 along the z direction. Leads 5-1 and 5-8 respectively connect the bottom electrode 5-3 and the top electrode 5-6 to TSV through holes 5-9 and 5-13 through the passivation layer window. The TSV through holes 5-9 and 5-13 are located around the resonant cavity 5-12 and penetrate the substrate 5-11 along the z direction.

[0058] More specifically, the overall planar shape of the piezoelectric micromechanical ultrasonic transducer (the shape of the orthographic projection figure formed along the z direction) is a square, and the overall planar shapes (the shapes of the orthographic projection figures formed along the z direction) of the elastic layer 5-2, the bottom electrode 5-3, the piezoelectric layer 5-5, the top electrode 5-6 and the resonant cavity 5-12 are also squares. The geometric centers of the orthographic projection figures of the elastic layer 5-2, the bottom electrode 5-3, the piezoelectric layer 5-5, the top electrode 5-6 and the resonant cavity 5-12 along the z direction coincide with each other, the areas of the orthographic projection figures of the bottom electrode 5-3 and the piezoelectric layer 5-5 are equal, the area of ​​the orthographic projection figure of the elastic layer 5-2 is greater than the orthographic projection area of ​​the resonant cavity 5-12 along the z direction, the areas of the orthographic projection figures of the bottom electrode 5-3 and the piezoelectric layer 5-5 are greater than the orthographic projection area of ​​the top electrode 5-6 along the z direction, and the orthographic projection area of ​​the top electrode 5-6 is approximately 0.7 times the orthographic projection area of ​​the bottom electrode 5-3.

[0059] More specifically, the material of each layer of the piezoelectric micromechanical ultrasonic transducer is selected by considering comprehensive factors. Exemplarily, the material of the piezoelectric layer 5-5 is a piezoelectric material with piezoelectric properties, including at least one of PZT, AlN, AlScN, ZnO and KNN, wherein AlScN is compatible with the CMOS manufacturing process and has biocompatibility relative to the other piezoelectric materials, and is the preferred material for preparing the piezoelectric layer. The material of the top electrode 5-6 and the bottom electrode 5-3 can be at least one of Mo, Al, Au, Ti, Pt, Ni and TiN. The material of the leads 5-1 and 5-8 can be at least one of Au, Cu, Mo, Pt, Ni and TiN. The material of the substrate 5-11 can be Si, etc. The material of the TSV through holes 5-9 and 5-13 can be one of Cu, W, Al, Mo and Ag, and the thickness of the TSV through holes 5-9 and 5-13 is equal to the thickness of the substrate 5-11. The material of the pads 5-10 and 5-14 can be one of Al, Cu, Au, Mo and Ag. The material of the passivation layer 5-7 can be SiO 2 wait.

[0060] In a typical implementation case, the specific size parameters of the piezoelectric micromechanical ultrasonic transducer probe and the piezoelectric micromechanical ultrasonic transducer are shown in Table 2.

[0061] Table 2 Dimensional parameters of piezoelectric micromechanical ultrasonic transducer

[0062]

[0063] *Note: The characteristic dimensions are the side lengths of the plane figures of the structures described, and the array unit is a single piezoelectric micromechanical ultrasonic transducer.

[0064] Specifically, as mentioned above, the plane figure of the piezoelectric film is a square, and the stress release hole structure is arranged in the middle area (i.e., the middle section) of the four sides of the piezoelectric film. Preferably, the stress release hole structure includes four stress release holes (which can be referred to as release holes) 5-15, and the four stress release holes 5-15 are arranged one by one in the middle area (i.e., the middle section) of the four sides of the piezoelectric film, wherein the stress release holes 5-15 are preferably rectangular holes, and the geometric center of each stress release hole 5-15 is located on the midline of one side of the piezoelectric film corresponding to itself, and the long side of the stress release hole 5-15 is parallel to one side of the piezoelectric film corresponding to the stress release hole 5-15, and the length of the long side of the stress release hole 5-15 is less than 0.8a, where a is the side length of the resonant cavity. The stress release hole structure can greatly improve the amplitude sensitivity of the piezoelectric film under the premise of slightly changing the effective filling area by reducing the fixed stress constraint between the multilayer film and the substrate.

[0065] For details, please refer to Figure 7 The phase-controlled circuit board includes a control circuit, an oscillation circuit, a phase-locked loop circuit, a power amplifier circuit, and a display circuit. The control circuit is connected to the oscillation circuit, the oscillation circuit is also connected to the phase-locked loop circuit, the phase-locked loop circuit is also connected to the power amplifier circuit, the display circuit is also connected to the control circuit, the power amplifier circuit is connected to the piezoelectric micromechanical ultrasonic transducer, the display screen is connected to the display circuit, and the operation button is connected to the control circuit. The oscillation circuit is used to generate an electrical signal of a specific frequency, and then the phase-locked loop forms a phase difference, and the power amplifier improves the load capacity of the system. This process is controlled by the user through the display circuit and the control circuit.

[0066] See also Figure 8 , 10-1 in the figure is a piezoelectric micromechanical ultrasonic transducer array (which can be simply referred to as an ultrasonic transducer array), which includes multiple piezoelectric micromechanical ultrasonic transducers (which can be simply referred to as ultrasonic transducers), each array unit is driven by a pulse signal, each pulse signal is driven by a sinusoidal alternating current signal 10-3 of multiple cycles, the frequency of the sinusoidal alternating current signal 10-3 is the same as the resonant frequency of the piezoelectric micromechanical ultrasonic transducer, in addition, each output pulse signal has a time delay, which is controlled by a phase-controlled circuit board represented by 10-2, and the phase-controlled circuit board 10-2 is composed of Figure 7The modules in the system are used together to realize that when a pulse signal is given to the upper and lower electrodes of the piezoelectric micromechanical ultrasonic transducer, the piezoelectric film is driven to vibrate and emit ultrasonic waves. Multiple piezoelectric micromechanical ultrasonic transducers emit ultrasonic waves and sound superposition occurs at the position to be cleaned, thereby achieving sound energy focusing.

[0067] Specifically, the working process of an ultrasonic cleaning device provided by an embodiment of the present invention specifically includes: a power supply provides energy for the entire system (including a phase-controlled circuit board, a display screen, and a piezoelectric micromechanical ultrasonic transducer array), the phase-controlled circuit board realizes phase control of the piezoelectric micromechanical ultrasonic transducer array, and the device is controlled by an operation button that can be controlled by a user. The phase-controlled circuit board is designed based on the principle of phase-controlled acoustic focusing. The high-density array design and acoustic focusing can greatly improve the ultrasonic cleaning ability. In addition, the integrated design and the high-frequency ultrasonic design can greatly improve the convenience of the device. At the same time, the high-frequency ultrasonic wave will only produce a small cavitation effect around the local area to be cleaned, which can meet the protection of non-cleaning positions, especially in the cleaning field during micro-nano manufacturing.

[0068] Specifically, in combination with the above, the stress release hole structure is arranged in the middle of the four sides of the piezoelectric film in the square piezoelectric micromechanical ultrasonic transducer. The arrangement of the stress release hole structure can be compatible with the resonant cavity preparation process while effectively reducing the influence of the edge fixed constraint on the film vibration, thereby improving the transmission sensitivity of the piezoelectric micromechanical ultrasonic transducer. The resonant frequency of a piezoelectric micromechanical ultrasonic transducer provided in an embodiment of the present invention is between 0.5MHz and 3MHz. This operating frequency range can reduce the harm of cavitation and obtain suitable cleaning efficiency.

[0069] For details, please refer to Fig. 9 and Fig.10 , Fig. 9 The characteristic dimension a in is the side length of the resonant cavity of the piezoelectric micromechanical ultrasonic transducer. After testing, it is known that the resonant frequency of a piezoelectric micromechanical ultrasonic transducer with a stress release hole structure is about 960kHz, and the highest amplitude is obtained at the resonant frequency. Moreover, after comparative testing, it is also found that the square piezoelectric micromechanical ultrasonic transducer with a stress release hole structure has a higher amplitude sensitivity than the square piezoelectric micromechanical ultrasonic transducer without a stress release hole structure, which means that it can emit higher ultrasonic energy. A piezoelectric micromechanical ultrasonic transducer with a stress release hole structure provided by an embodiment of the present invention has a sound intensity of 6.5W / m^2 at a vertical distance of 5mm and a sound intensity of 1.4W / m^2 at a vertical distance of 10mm under the drive of 1Vpp.

[0070] For details, please refer to Fig.11The specific operation of ultrasonic cleaning by a piezoelectric micromechanical ultrasonic transducer cleaning device is as follows: put a glass vessel 6-2 on the stage, add a cleaning solution (acetone) 6-3 into the glass vessel 6-2, put the object 6-5 to be cleaned into the cleaning solution 6-3, vertically place the ultrasonic cleaning device 6-1, and control its acoustic focus point to the cleaning area 6-4 of the object 6-5 to be cleaned, turn on the switch to start cleaning, and adjust the cleaning time according to the difficulty of cleaning. Figure 8 The piezoelectric micromechanical ultrasonic transducer is controlled by the phase-controlled circuit board 10-2, and the phase-controlled delay time of each piezoelectric micromechanical ultrasonic transducer is determined by formula (1):

[0071]

[0072] A piezoelectric micromechanical ultrasonic transducer located at the geometric center of the XY plane in the piezoelectric micromechanical ultrasonic transducer array 10-1 is set as a central unit, and its phase delay is 0.

[0073] The acoustic focusing point 10-4 is set to be located at the z-direction center axis position of the central unit, d is the z-direction distance between the acoustic focusing point 10-4 and the geometric center of the piezoelectric film of the central unit, s is the distance between the z-direction center axis of the remaining piezoelectric micromechanical ultrasonic transducers except the central unit and the z-direction center axis of the central unit, and v is the speed of sound in the cleaning fluid.

[0074] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A piezoelectric micromechanical ultrasonic transducer, comprising a substrate and a piezoelectric film, wherein the substrate has a resonant cavity, and the piezoelectric film is arranged on the substrate along the z direction and covers the resonant cavity, characterized in that: A stress release hole structure is also provided on the outer peripheral edge of the piezoelectric film, and the stress release hole structure is connected to the resonant cavity.

2. The piezoelectric micromechanical ultrasonic transducer according to claim 1, characterized in that: The resonant cavity and the piezoelectric film are both regular quadrilateral structures, and the stress release hole structure includes four stress release holes, which are respectively arranged on four sides of the piezoelectric film.

3. The piezoelectric micromechanical ultrasonic transducer according to claim 2, characterized in that: The stress release hole is arranged in the middle area of ​​one side of the piezoelectric film where the stress release hole is located; Preferably, the stress release hole is a rectangular hole; Preferably, in the orthographic projection figure formed along the z direction, the geometric center of any of the stress release holes is located on the midline of the edge of the piezoelectric film where the stress release hole is located. Preferably, the long side of the rectangular stress release hole is parallel to the side of the piezoelectric film where the rectangular stress release hole is located.

4. The piezoelectric micromechanical ultrasonic transducer according to claim 2, characterized in that: The stress release hole structure is a rotationally symmetrical structure.

5. The piezoelectric micromechanical ultrasonic transducer according to claim 2, characterized in that: The piezoelectric film includes a top electrode, a piezoelectric layer, a bottom electrode and an elastic layer which are stacked in sequence along the z direction, the elastic layer is stacked on the substrate, the geometric centers of the orthographic projection figures of the top electrode, the piezoelectric layer, the bottom electrode, the elastic layer and the resonant cavity along the z direction coincide with each other, the orthographic projection areas of the piezoelectric layer and the bottom electrode along the z direction are equal, the orthographic projection area of ​​the elastic layer along the z direction is greater than the orthographic projection area of ​​the resonant cavity along the z direction, the orthographic projection areas of the piezoelectric layer and the electrode layer along the z direction are greater than the orthographic projection area of ​​the top electrode along the z direction.

6. A piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device for ultrasonic cleaning of micrometer-sized surfaces, characterized in that: The piezoelectric micromechanical ultrasonic transducer ultrasonic cleaning device includes: a piezoelectric micromechanical ultrasonic transducer probe and a phase-controlled circuit board. The piezoelectric micromechanical ultrasonic transducer probe includes a plurality of piezoelectric micromechanical ultrasonic transducers described in any one of claims 1 to 5. The plurality of piezoelectric micromechanical ultrasonic transducers are arranged in an array. The plurality of piezoelectric micromechanical ultrasonic transducers are connected to the phase-controlled circuit board through a multi-channel electrical signal. The piezoelectric micromechanical ultrasonic transducer probe cooperates with the phase-controlled circuit board to achieve focusing of sound waves through phase control.

7. The piezoelectric micromechanical ultrasonic transducer according to claim 6, characterized in that: The phase-controlled circuit board includes a control circuit, an oscillation circuit, a phase-locked loop circuit, a power amplifier circuit, and a display circuit. The control circuit is connected to the oscillation circuit, the oscillation circuit is also connected to the phase-locked loop circuit, the phase-locked loop circuit is also connected to the power amplifier circuit, the display circuit is also connected to the control circuit, and the power amplifier circuit is connected to the piezoelectric micromechanical ultrasonic transducer.

8. The piezoelectric micromechanical ultrasonic transducer according to claim 7, characterized in that: Also includes: A housing and an acoustic impedance matching structure, wherein the acoustic impedance matching structure, the piezoelectric micromechanical ultrasonic transducer probe and the phased circuit board are arranged inside the housing, the acoustic impedance matching structure, the piezoelectric micromechanical ultrasonic transducer probe and the phased circuit board are arranged in sequence along the z direction, and the acoustic impedance matching structure is formed of an acoustic impedance matching material Preferably, a first surface of the acoustic impedance matching structure facing away from the piezoelectric micromechanical ultrasonic transducer probe is parallel to a second surface of the piezoelectric micromechanical ultrasonic transducer probe facing the acoustic impedance matching structure, and geometric centers of the first surface and the second surface coincide.

9. The piezoelectric micromechanical ultrasonic transducer according to claim 8, characterized in that: Also includes: A PCB packaging board, wherein the PCB packaging board is arranged between the piezoelectric micromechanical ultrasonic transducer probe and the phase-controlled circuit board, and the piezoelectric micromechanical ultrasonic transducer probe and the phase-controlled circuit board are connected via the PCB packaging board; Preferably, the piezoelectric micromechanical ultrasonic transducer further includes a display screen and an operation button, and the display screen and the operation button are electrically connected to the phase-controlled circuit board.

10. A method for ultrasonic cleaning of a micrometer-sized surface, characterized in that: include: The product to be cleaned is placed in a cleaning liquid, and the acoustic focus of the piezoelectric micromechanical ultrasonic transducer according to any one of claims 6 to 9 is controlled on the surface of the area to be cleaned of the product to be cleaned, and the surface of the area to be cleaned of the product to be cleaned is cleaned, wherein the area to be cleaned is of micrometer size; Preferably, the piezoelectric micromechanical ultrasonic transducer is controlled by the phase-controlled circuit board, and the phase-controlled delay time of each piezoelectric micromechanical ultrasonic transducer is determined by formula (1): A piezoelectric micromechanical ultrasonic transducer located at the geometric center of the XY plane in the piezoelectric micromechanical ultrasonic transducer array is set as a central unit, and its phase delay is 0, The acoustic focusing point is set to be located at the z-direction center axis position of the central unit, d is the z-direction distance between the acoustic focusing point and the geometric center of the piezoelectric film of the central unit, s is the distance between the z-direction center axis of the remaining piezoelectric micromechanical ultrasonic transducers except the central unit and the z-direction center axis of the central unit, and v is the speed of sound in the cleaning fluid.

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