Piezoelectric MEMS transducer and electrical product

Abstract

The invention provides a piezoelectric MEMS transducer and an electrical product. The piezoelectric MEMS transducer comprises a first electrode layer, a second electrode layer and a single crystal piezoelectric film, the first electrode layer and the second electrode layer are correspondingly attached to the surfaces of the two sides of the single crystal piezoelectric film respectively. The single-crystal piezoelectric film is a single-crystal lithium niobate film or a single-crystal lithium tantalate film, and the single-crystal piezoelectric film has a determined cutting type of a target Euler angle, so that the piezoelectric coupling coefficient of the single-crystal piezoelectric film is not less than 6.4% or the absolute value of an e33 coefficient in a piezoelectric constant matrix is not less than 1.55; wherein the piezoelectric MEMS transducer works in a thickness expansion and contraction mode.

Description

Technical Field

[0001] The present application relates to the fields of materials and semiconductors, and in particular to a piezoelectric MEMS transducer and an electrical product. Background Art

[0002] Devices based on piezoelectric materials have penetrated into all aspects of modern society. Traditional piezoelectric devices are mainly based on bulk materials such as quartz or ceramics. They are not only bulky and expensive, but also difficult to manufacture in a continuous production mode. Therefore, they are limited to some special applications or high-end applications. With the continuous development of advanced materials and semiconductor technology, the integration of piezoelectric thin film material deposition technology and MEMS / CMOS manufacturing processes has become increasingly high, opening up a new path for transducers based on piezoelectric films. For piezoelectric MEMS ultrasonic transducers, an important performance indicator is the material's electromechanical coupling coefficient K. 2 , this coupling coefficient characterizes the mutual conversion efficiency of electrical energy and acoustic energy in the device, usually K 2 Devices with higher values ​​have better key performance indicators because of their higher energy utilization and conversion efficiency. The electromechanical coupling coefficient of piezoelectric MEMS ultrasonic transducers is largely determined by the piezoelectric material used. Lithium niobate (LiNbO 3 Abbreviated as LN) or lithium tantalate (LiTaO 3 LT) single crystal thin film can significantly improve the performance of the above devices due to its excellent properties such as large electromechanical coupling coefficient and small propagation loss. The LN or LT single crystal piezoelectric film material with a piezoelectric coefficient can significantly improve the transmission and reception efficiency of the piezoelectric MEMS ultrasonic transducer. Another important performance indicator is the piezoelectric coefficient e of the piezoelectric material. 33 . Usually, piezoelectric MEMS ultrasonic transducers work in bending vibration mode. However, due to the low piezoelectric material coefficients K31 and e31 used in such piezoelectric MEMS ultrasonic transducers, their transmission and reception efficiency is low. If the piezoelectric MEMS ultrasonic transducer works in thickness stretching vibration mode, using higher piezoelectric material coefficients K33 and e33, the transmission and reception efficiency of the piezoelectric MEMS ultrasonic transducer can be significantly improved.

[0003] In actual work, Euler angles are usually used to represent LN and LT cuts. There are many ways to use Euler angles, and the following is the most common one. For a reference system in three-dimensional space, the orientation of any coordinate system can be expressed by three Euler angles. The reference system is stationary, and the commonly used reference system is the right-handed coordinate system (such as Figure 1A The xyz coordinate system shown in the figure can be considered as the crystal axis coordinate system in the crystal. The Euler transformation coordinate system (such as Figure 1AThe XYZ coordinate system shown in the figure is fixed to the rigid body and can be considered as a certain section or cut in the crystal. The Euler transformation coordinate system rotates with the rotation of the section. In the present application, the Z axis of the Euler transformation coordinate system is set to be perpendicular to the target section, that is, along the thickness direction of the section, and the XY axis is located in the section. The English letter (N) represents the intersection of the xy plane and the XY plane. The Euler angles are defined in the order of rotation around the zxz axis as (α (precession angle), β (nutation angle), γ (rotation angle)), where α is the angle of the first rotation around the z axis (when looking from the positive end of the axis to the origin, the counterclockwise rotation direction is the positive rotation angle, and the clockwise direction is the negative rotation angle), and α also corresponds to the angle between the x axis and the intersection line N; β is the angle of rotation around the x axis, which also corresponds to the angle between the z axis and the Z axis; γ is the angle of the second rotation around the z axis, which also corresponds to the angle between the intersection line N and the X axis. Summary of the invention

[0004] The purpose of the present application is to provide a piezoelectric MEMS transducer and electrical product, which can improve the transmission and reception efficiency of an ultrasonic transducer device using the single crystal piezoelectric material by selecting appropriate Euler angles to meet the target electromechanical coupling coefficient or piezoelectric constant matrix.

[0005] To achieve the above purpose, the piezoelectric MEMS transducer provided by the present application comprises a first electrode layer, a second electrode layer and a single crystal piezoelectric film; the first electrode layer and the second electrode layer are respectively attached to the two side surfaces of the single crystal piezoelectric film; the single crystal piezoelectric film is a single crystal lithium niobate film or a single crystal lithium tantalate film, and the single crystal piezoelectric film has a definite cut of the target Euler angle, so that the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 6.4% or the absolute value of the e33 coefficient in the piezoelectric constant matrix is ​​not less than 1.55. The piezoelectric MEMS transducer provided by the present application works in a thickness expansion mode.

[0006] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and nutation angle of the target Euler angle are within one cycle, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is 31.8%, the target Euler angle is (0°, 121°, 0°), (60°, 59°, 0°) or (120°, 121°, 0°).

[0007] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium niobate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 14.8%, the target Euler angle is (30°~90°, 34°~83°, 0°), (90°~150°, 97°~146°, 0°) or (-30°~30°, 97°~146°, 0°).

[0008] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium niobate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 6.4%, the target Euler angle is (0°, 26°~48°, 0°) or (0°, 89°~159°, 0°).

[0009] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and nutation angle of the target Euler angle are within one period, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.9 times of 31.8%, the target Euler angle is (50°~70°, 50°~68°, 0°), (110°~130°, 112°~130°, 0°) or (-10°~10°, 112°~130°, 0°); when the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.8 times of 31.8%, the target Euler angle is (45°~75°, 46°~72°, 0°), (105°~135°, 108°~134°, 0°) or (-15°~15°, 108°~134°, 0°).

[0010] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium tantalate film, the precession angle and nutation angle of the target Euler angle are within one cycle, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is 11%, the target Euler angle is (0°, 121°, 0°), (60°, 59°, 0°) or (120°, 121°, 0°); when the piezoelectric coupling coefficient is not less than 6.4%, the target Euler angle is (29°~91°, 31°~80°, 0°), (89°~151°, 100°~149°, 0°) or (-31°~31°, 100°~149°, 0°).

[0011] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium niobate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.9 times of 11%, the target Euler angle is (49°~71°, 48°~69°, 0°), (109°~131°, 111°~132°, 0°) or (-11°~11°, 111°~132°, 0°); when the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.8 times of 11%, the target Euler angle is (43°~77°, 42°~73°, 0°), (103°~137°, 107°~138°, 0°) or (-17°~17°, 107°~138°, 0°).

[0012] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and nutation angle of the target Euler angle are within one period, and the absolute value of the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is 4.64, the maximum value of the target Euler angle is (60°, 61°, 0°) or (180°, 61°, 0°), and the minimum value is (0°, 119°, 0°) or (120°, 119°, 0°); when the e33 coefficient in the piezoelectric constant matrix is ​​not less than 1.55, the target Euler angle is (0°, 14°~58°, 0°) or (0°, 84°~168°, 0°); when the e33 coefficient in the piezoelectric constant matrix is ​​not less than 2.16, the target Euler angle is (0°, 30°~48°, 0°) or (0°, 68°~157°, 0°).

[0013] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium niobate film, and the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.9 times of 4.64, the target Euler angle is (46°~74°, 48°~61°, 0°), (106°~134°, 106°~132°, 0°) or (-14°~14°, 106°~132°, 0°); when the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.8 times of 4.64, the target Euler angle is (38°~82°, 41°~79°, 0°), (98°~142°, 101°~139°, 0°) or (-22°~22°, 101°~139°, 0°).

[0014] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium tantalate film, the precession angle and the nutation angle of the target Euler angle are in one cycle, and the absolute value of the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is 3.27, the maximum value of the target Euler angle is (60°, 57°, 0°) or (180°, 57°, 0°), and the minimum value is (0°, 123°, 0°) or (120°, 123 °, 0°); when the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 1.55, the target Euler angle is (0°, 0°~54°, 0°) or (0°, 90°~180°, 0°); when the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 2.16, the target Euler angle is (0°, 29°~34°, 0°) or (0°, 97°~161°, 0°).

[0015] In one embodiment of the present application, optionally, when the single crystal piezoelectric film is a single crystal lithium tantalate film, and the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.9 times of 3.27, the target Euler angle is (43°~77°, 41°~71°, 0°), (103°~137°, 109°~139°, 0°) or (-17°~17°, 109°~139°, 0°); when the single crystal piezoelectric film is not less than 0.8 times of 3.27, the target Euler angle is (33°~87°, 32°~77°, 0°), (93°~147°, 103°~148°, 0°) or (-27°~27°, 103°~148°, 0°).

[0016] In one embodiment of the present application, optionally, the transducer further includes a substrate; the substrate is in contact with a surface of one side of the single crystal piezoelectric film, and the substrate is made of silicon.

[0017] In one embodiment of the present application, optionally, a cavity is included between the substrate and the single crystal piezoelectric film, and the second electrode layer is at least partially disposed in the cavity.

[0018] In one embodiment of the present application, optionally, the transducer further includes a dielectric layer; the substrate is connected to one side surface of the single crystal piezoelectric film through the dielectric layer.

[0019] In one embodiment of the present application, optionally, the dielectric layer and the single crystal piezoelectric film contacting side include a cavity, and the second electrode layer is at least partially disposed in the cavity.

[0020] In one embodiment of the present application, optionally, the cavity is partially or completely filled with a sound loss layer.

[0021] In one embodiment of the present application, optionally, the transducer further includes an acoustic impedance matching layer, and the acoustic impedance matching layer is attached to the first electrode layer side of the single crystal piezoelectric film and covers the first electrode layer.

[0022] The present application also provides an electrical product, which has the piezoelectric micromechanical ultrasonic transducer as described above.

[0023] The beneficial technical effect of the present application is that the appropriate Euler angle is determined by the electromechanical coupling coefficient, the piezoelectric constant matrix and the type of single crystal piezoelectric material, thereby improving the performance during the application of the single crystal piezoelectric film, reducing unnecessary electrical losses, and improving energy utilization and conversion efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings described herein are used to provide a further understanding of the present application, constitute a part of the present application, and do not constitute a limitation of the present application. In the drawings:

[0025] Figure 1A A schematic diagram of the principle of Euler angles provided in one embodiment of the present application;

[0026] Figure 1B A schematic diagram of a flow chart of a method for selecting a single crystal piezoelectric material cutting pattern provided in one embodiment of the present application;

[0027] FIG. 2A to FIG. 2D A schematic diagram of the cutting type selection of LN material under different piezoelectric coupling coefficient restriction conditions provided in an embodiment of the present application;

[0028] Figure 3 A schematic diagram of a curve showing a change in the piezoelectric coupling coefficient with the nutation angle in the LN material provided in one embodiment of the present application;

[0029] FIG. 4A to FIG. 4C A schematic diagram of the cutting selection of LT materials under different piezoelectric coupling coefficient restriction conditions provided in an embodiment of the present application;

[0030] Figure 5 A schematic diagram of a curve showing a change in piezoelectric coupling coefficient with nutation angle in a LT material provided in an embodiment of the present application;

[0031] FIG. 6A to FIG. 6D A schematic diagram of the cutting type selection of LN material under different piezoelectric constant matrix restriction conditions provided in an embodiment of the present application;

[0032] Figure 7 A schematic diagram of a curve showing the change of the piezoelectric constant matrix with the nutation angle in the LN material provided in one embodiment of the present application;

[0033] FIG. 8A to FIG. 8D A schematic diagram of the cutting selection of LT materials under different piezoelectric constant matrix constraints provided in an embodiment of the present application;

[0034] Fig. 9 A schematic diagram of a curve showing the variation of the piezoelectric constant matrix with the nutation angle in the LT material provided in one embodiment of the present application;

[0035] FIG. 10A to FIG. 10G A schematic structural diagram of a piezoelectric micromechanical ultrasonic transducer device including a single-crystal piezoelectric film provided in one embodiment of the present application. DETAILED DESCRIPTION

[0036] The following will describe the implementation methods of the present application in detail in conjunction with the accompanying drawings and embodiments, so that the implementation process of how the present application applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly. It should be noted that as long as there is no conflict, the various embodiments in the present application and the various features in the embodiments can be combined with each other, and the technical solutions formed are all within the protection scope of the present application.

[0037] In addition, the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be performed in an order different from that shown here.

[0038] The present application provides a piezoelectric MEMS ultrasonic transducer, the device comprising a first electrode layer, a second electrode layer and a single crystal piezoelectric film; the first electrode layer and the second electrode layer are respectively and correspondingly attached to the two side surfaces of the single crystal piezoelectric film; the single crystal piezoelectric film is a single crystal lithium niobate film or a single crystal lithium tantalate film, and the single crystal piezoelectric film has a definite cut of a target Euler angle, so that the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 6.4% or the absolute value of the e33 coefficient in the piezoelectric constant matrix is ​​not less than 1.55, wherein the piezoelectric MEMS transducer operates in a thickness expansion mode.

[0039] Please refer to Figure 1B As shown, the method for selecting the single crystal piezoelectric film specifically includes:

[0040] S101 determines adjustment parameters according to the functional relationship among the piezoelectric coupling coefficient, the piezoelectric constant matrix, the elastic coefficient matrix and the dielectric constant matrix;

[0041] S102: determining the type of the single crystal piezoelectric material according to the adjustment parameter, and obtaining the adjustment interval of the adjustment parameter according to the type of the single crystal piezoelectric material;

[0042] S103 obtains a corresponding cut of the single crystal piezoelectric material type through the Euler angle according to the adjustment interval.

[0043] The adjustment parameters include piezoelectric coupling coefficient and piezoelectric constant matrix, and the single crystal piezoelectric material types include lithium niobate and lithium tantalate. Specifically, in LN or LT film, the piezoelectric coupling coefficient It represents the intensity of the mutual conversion between mechanical energy and electrical energy when the electric field in the z direction excites the vibration in the z direction, where the z direction is defined as the thickness direction of the piezoelectric film and is represented by the number 3. The relationship between the piezoelectric coupling coefficient and the material parameters is as follows:

[0044]

[0045] Among them, c 33 is the elastic coefficient matrix of the piezoelectric material, is the piezoelectric constant matrix of the piezoelectric material, ε 33 is the dielectric constant matrix of the piezoelectric material.

[0046] LN and LT crystals belong to the trigonal system and have a wide variety of cuts. The piezoelectric properties of different cuts vary greatly. Currently, the commonly used piezoelectric film materials are AlN piezoelectric films and ScAlN piezoelectric films with different Sc doping concentrations. 6.4%, ScAlN (Sc doping concentration is 20%) When the Sc doping concentration is lower than 20%, It is between 6.4% and 14.8%. However, the higher the doping concentration, the more and larger defects the sputtered film will have, which will increase the electrical loss of the film and deteriorate the performance of the device using the piezoelectric film (such as Q value and noise, etc.). In contrast, LN and LT are single crystal materials. The films obtained by ion beam stripping technology or grinding and thinning technology still maintain single crystal characteristics, so the dielectric loss is small, and by selecting the appropriate cutting type (Euler angle) of LN and LT, the LN or LT piezoelectric film can be made The coefficient is larger than that of aluminum nitride or doped aluminum nitride. The patent of this invention mainly protects the cut type (Euler angle) that meets the above range, and the devices manufactured using the corresponding cut type. For some application scenarios, more attention is paid to e 33 Parameters, e of AlN 33 is 1.55, and the e of ScAlN (Sc doping concentration is 20%) 33 By selecting the appropriate cut type (Euler angle) of LN and LT, the e of LN or LT piezoelectric film can be 33 The coefficient is larger than that of aluminum nitride or doped aluminum nitride. This application determines the cut type (Euler angle) that meets the above range through the above process, and the specific selection process can be referred to the subsequent embodiments.

[0047] In one embodiment of the present application, when the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and the nutation angle of the target Euler angle are within one cycle, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is 31.8%, the target Euler angle is (0°, 121°, 0°), (60°, 59°, 0°) or (120°, 121°, 0°); when the single crystal piezoelectric film is a single crystal lithium niobate film, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 14 .8%, the target Euler angle is (30°~90°, 34°~83°, 0°), (90°~150°, 97°~146°, 0°) or (-30°~30°, 97°~146°, 0°); when the single crystal piezoelectric film is a single crystal lithium niobate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 6.4%, the target Euler angle is (0°, 26°~48°, 0°) or (0°, 89°~159°, 0°).

[0048] Specifically, for LN materials, The maximum value is 31.8%. When α and β are determined, γ is obtained from 0° to 180°. are the same, so when describing the cut type, we only use γ as 0° to represent the corresponding Euler angle. When α and β are in one cycle, that is, 0°≤α≤180°, 0°≤β≤180°, there are 4 groups of Euler angles corresponding to their maximum values, namely (0°, 121°, 0°), (60°, 59°, 0°), (120°, 121°, 0°), (180°, 59°, 0°). Among them, (0°, 121°, 0°) and (180°, 59°, 0°) correspond to the same cut type, and are the cut types that can be mass-produced with current technology, that is, the 31° Y-cut cut type, but it is not a commonly used cut type. At this time, let The distribution of α and β can be obtained as Figure 2A As shown. The distribution of α and β can be obtained as Figure 2B At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle ranges are as follows: (0°~30°, 97°~146°, 0°), (30°~90°, 34°~83°, 0°), (90°~150°, 97°~146°, 0°), (150°~180°, 34°~83°, 0°), wherein the first and fourth ranges can be combined into one range (-30°~30°, 97°~146°, 0°).

[0049] In another embodiment of the present application, when the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and nutation angle of the target Euler angle are within one period, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.9 times of 31.8%, the target Euler angle is (50°~70°, 50°~68°, 0°), (110°~130°, 112°~130°, 0°) or (-10°~10°, 112°~130°, 0°); when the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.8 times of 31.8%, the target Euler angle is (45°~75°, 46°~72°, 0°), (105°~135°, 108°~134°, 0°) or (-15°~15°, 108°~134°, 0°).

[0050] Specifically, (i.e. 0.9 times the maximum value), we can get the distribution of α and β as Figure 2CAs shown. At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle range is as follows: (0°~10°, 112°~130°, 0°), (50°~70°, 50°~68°, 0°), (110°~130°, 112°~130°, 0°), (170°~180°, 50°~68°, 0°), among which the first and fourth ranges can be combined into one range (-10°~10°, 112°~130°, 0°). Let (i.e. 0.8 times the maximum value), we can get the distribution of α and β as Figure 2D At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle ranges are as follows: (0°~15°, 108°~134°, 0°), (45°~75°, 46°~72°, 0°), (105°~135°, 108°~134°, 0°), (165°~180°, 46°~72°, 0°), wherein the first and fourth ranges can be combined into one range (-15°~15°, 108°~134°, 0°).

[0051] In summary, the common commercial cutting types include X-cut, Z-cut, and rotary Y-cut (including Y-cut). 0, Z-cut is 2.7%, so it is not suitable for implementation Corresponding vibration mode. For the cut type of rotating Y-cut (including Y-cut), the corresponding Euler angle is (0°, β, 0°), where β varies in the range of 0° to 180°. The curve with β changes is as follows Figure 3 When the Euler angle is (0°, 121°, 0°), The maximum value is 31.8%. Then the range of Euler angles is (0°, 26°~48°, 0°), (0°, 89°~159°, 0°). Then the range of Euler angles is (0°, 97°~146°, 0°). (i.e. 0.9 times the maximum value), then the range of Euler angles is (0°, 112° to 130°, 0°). (That is, 0.8 times the maximum value), then the range of the Euler angle is (0°, 108°~134°, 0°).

[0052] In one embodiment of the present application, when the single crystal piezoelectric film is a single crystal lithium tantalate film, the precession angle and nutation angle of the target Euler angle are within one cycle, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is 11%, the target Euler angle is (0°, 121°, 0°), (60°, 59°, 0°) or (120°, 121°, 0°); when the piezoelectric coupling coefficient is not less than 6.4%, the target Euler angle is (29°~91°, 31°~80°, 0°), (89°~151°, 100°~149°, 0°) or (-31°~31°, 100°~149°, 0°).

[0053] Specifically, for LT materials, The maximum value of is 11%. When α and β are in one cycle, that is, 0°≤α≤180°, 0°≤β≤180°, there are 4 groups of Euler angles corresponding to its maximum value, namely (0°, 121°, 0°), (60°, 59°, 0°), (120°, 121°, 0°), (180°, 59°, 0°). Among them, (180°, 59°, 0°) corresponds to the same cut type as (0°, 121°, 0°), and it is a cut type that can be mass-produced with current technology, that is, 31° Y-cut cut type, but it is not a commonly used cut type. At this time, let The distribution of α and β can be obtained as Figure 4A At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle ranges are as follows: (0°~31°, 100°~149°, 0°), (29°~91°, 31°~80°, 0°), (89°~151°, 100°~149°, 0°), (149°~180°, 31°~80°, 0°), wherein the first and fourth ranges can be combined into one range (-31°~31°, 100°~149°, 0°).

[0054] In another embodiment of the present application, when the single crystal piezoelectric film is a single crystal lithium tantalate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.9 times of 11%, the target Euler angle is (49°~71°, 48°~69°, 0°), (109°~131°, 111°~132°, 0°) or (-11°~11°, 111°~132°, 0°); when the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.8 times of 11%, the target Euler angle is (43°~77°, 42°~73°, 0°), (103°~137°, 107°~138°, 0°) or (-17°~17°, 107°~138°, 0°).

[0055] Specifically, (i.e. 0.9 times the maximum value), we can get the distribution of α and β as Figure 4B As shown. At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle range is as follows: (0°~11°, 111°~132°, 0°), (49°~71°, 48°~69°, 0°), (109°~131°, 111°~132°, 0°), (169°~180°, 48°~69°, 0°), among which the first and fourth ranges can be combined into one range (-11°~11°, 111°~132°, 0°). Let (i.e. 0.8 times the maximum value), we can get the distribution of α and β as Figure 4C At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle ranges are as follows: (0°~17°, 107°~138°, 0°), (43°~77°, 42°~73°, 0°), (103°~137°, 107°~138°, 0°), (163°~180°, 42°~73°, 0°), wherein the first and fourth ranges can be combined into one range (-17°~17°, 107°~138°, 0°).

[0056] In summary, the common commercial cutting types include X-cut, Z-cut, and rotary Y-cut (including Y-cut). 0, Z-cut is 3.35%, so neither is suitable for implementation Corresponding vibration mode. For the cut type of rotating Y-cut (including Y-cut), the corresponding Euler angle is (0°, β, 0°), where β varies in the range of 0° to 180°. The curve with β changes is as follows Figure 5 When the Euler angle is (0°, 121°, 0°), reaches a maximum value of 11%. Then the range of Euler angles is (0°, 100°~149°, 0°). (i.e. 0.9 times the maximum value), then the range of Euler angles is (0°, 111° to 132°, 0°). (That is, 0.8 times the maximum value), then the range of the Euler angle is (0°, 107°~138°, 0°).

[0057] In one embodiment of the present application, when the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and nutation angle of the target Euler angle are within one period, and the absolute value of the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is 4.64, the maximum value of the target Euler angle is (60°, 61°, 0°) or (180°, 61°, 0°), and the minimum value is (0°, 119°, 0°) or (120°, 119°, 0°); when the e33 coefficient in the piezoelectric constant matrix is ​​not less than 1.55, the target Euler angle is (0°, 14°~58°, 0°) or (0°, 84°~168°, 0°); when the e33 coefficient in the piezoelectric constant matrix is ​​not less than 2.16, the target Euler angle is (0°, 30°~48°, 0°) or (0°, 68°~157°, 0°).

[0058] Specifically, for LN materials, e 33 The maximum value is 4.64, and the minimum value is -4.64, both of which correspond to the maximum absolute value. When α and β are within a cycle, that is, 0°≤α≤180°, 0°≤β≤180°, the maximum value corresponds to the Euler angle of (60°, 61°, 0°), (180°, 61°, 0°), and the minimum value corresponds to the Euler angle of (0°, 119°, 0°), (120°, 119°, 0°). Among them, (0°, 119°, 0°) and (180°, 61°, 0°) correspond to the same cut type, and are the cut types that can be mass-produced with current technology, that is, the 29° Y-cut cut type, but it is not a commonly used cut type. At this time, let |e 33 |≥1.55, we can get the distribution of α and β as follows Fig. 6A As shown. Let |e 33 |≥2.16, we can get the distribution of α and β as follows Figure 6B shown.

[0059] In another embodiment of the present application,

[0060] When the single crystal piezoelectric film is a single crystal lithium niobate film, and the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.9 times of 4.64, the target Euler angle is (46°~74°, 48°~61°, 0°), (106°~134°, 106°~132°, 0°) or (-14°~14°, 106°~132°, 0°); when the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.8 times of 4.64, the target Euler angle is (38°~82°, 41°~79°, 0°), (98°~142°, 101°~139°, 0°) or (-22°~22°, 101°~139°, 0°).

[0061] Specifically, let |e 33|≥4.64×0.9 (i.e. 0.9 times the maximum value), we can get the distribution of α and β as follows Figure 6C As shown. At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle range is as follows: (0°~14°, 106°~132°, 0°), (46°~74°, 48°~61°, 0°), (106°~134°, 106°~132°, 0°), (166°~180°, 48°~61°, 0°), among which the first and fourth ranges can be combined into one range (-14°~14°, 106°~132°, 0°). Let |e 33 |≥4.64×0.8 (i.e. 0.8 times the maximum value), we can get the distribution of α and β as follows Fig.6D At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle ranges are as follows: (0°~22°, 101°~139°, 0°), (38°~82°, 41°~79°, 0°), (98°~142°, 101°~139°, 0°), (158°~180°, 41°~79°, 0°), wherein the first and fourth ranges can be combined into one range (-22°~22°, 101°~139°, 0°).

[0062] In summary, the common commercial cutting types include X-cut, Z-cut, and rotary Y-cut (including Y-cut). 33 is 0, Z-cut 33 is 1.3, which is smaller than the e of AlN 33 Therefore, these two types of cuts cannot be used. For the cut of the rotating Y-cut (including the Y-cut), the corresponding Euler angle is (0°, β, 0°), where β varies in the range of 0° to 180°. 33 The curve with β changes is as follows Figure 7 When the Euler angle is (0°, 119°, 0°), e 33 reaches the minimum value. Let |e 33 |≥1.55, then the range of Euler angles is (0°, 14°~58°, 0°), (0°, 84°~168°, 0°). Let |e 33 |≥2.16, then the range of Euler angles is (0°, 30°~48°, 0°), (0°, 68°~157°, 0°). Let |e 33 |≥4.64×0.9 (i.e. 0.9 times the maximum value), then the range of Euler angles is (0°, 106°~132°, 0°). Let |e 33 |≥4.64×0.8 (i.e. 0.8 times the maximum value), then the range of the Euler angle is (0°, 101°~139°, 0°).

[0063] In one embodiment of the present application, when the single crystal piezoelectric film is a single crystal lithium tantalate film, the precession angle and the nutation angle of the target Euler angle are in one cycle, and the absolute value of the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is 3.27, the maximum value of the target Euler angle is (60°, 57°, 0°) or (180°, 57°, 0°), and the minimum value is (0°, 123°, 0°) or (120°, 123° , 0°); when the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 1.55, the target Euler angle is (0°, 0°~54°, 0°) or (0°, 90°~180°, 0°); when the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 2.16, the target Euler angle is (0°, 29°~34°, 0°) or (0°, 97°~161°, 0°).

[0064] Specifically, for LT materials, e 33 The maximum value is 3.27, and the minimum value is -3.27, both corresponding to the maximum absolute value. When α and β are within a cycle, that is, 0°≤α≤180°, 0°≤β≤180°, the maximum value corresponds to the Euler angle of (60°, 57°, 0°), (180°, 57°, 0°), and the minimum value corresponds to the Euler angle of (0°, 123°, 0°), (120°, 123°, 0°). Among them, (0°, 123°, 0°) and (180°, 57°, 0°) correspond to the same cut type, and are the cut types that can be mass-produced with current technology, that is, the 33° Y-cut cut type, but it is not a commonly used cut type. At this time, let |e 33 |≥1.55, we can get the distribution of α and β as follows Fig. 8A As shown. Let |e 33 |≥2.16, we can get the distribution of α and β as follows Figure 8B shown.

[0065] In another embodiment of the present application, when the single crystal piezoelectric film is a single crystal lithium tantalate film, and the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.9 times of 3.27, the target Euler angle is (43°~77°, 41°~71°, 0°), (103°~137°, 109°~139°, 0°) or (-17°~17°, 109°~139°, 0°); when the single crystal piezoelectric film is not less than 0.8 times of 3.27, the target Euler angle is (33°~87°, 32°~77°, 0°), (93°~147°, 103°~148°, 0°) or (-27°~27°, 103°~148°, 0°).

[0066] Specifically, let |e 33|≥3.27×0.9 (i.e. 0.9 times the maximum value), we can get the distribution of α and β as follows Figure 8C As shown. At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle range is as follows: (0°~17°, 109°~139°, 0°), (43°~77°, 41°~71°, 0°), (103°~137°, 109°~139°, 0°), (163°~180°, 48°~61°, 0°), among which the first and fourth ranges can be combined into one range (-17°~17°, 109°~139°, 0°). Let |e 33 |≥3.27×0.8 (i.e. 0.8 times the maximum value), we can get the distribution of α and β as follows Fig.8D At this time, according to the maximum and minimum values ​​of each interval α and β, the preferred Euler angle ranges are as follows: (0°~27°, 103°~148°, 0°), (33°~87°, 32°~77°, 0°), (93°~147°, 103°~148°, 0°), (153°~180°, 32°~77°, 0°), wherein the first and fourth ranges can be combined into one range (-27°~27°, 103°~148°, 0°).

[0067] In summary, the common commercial cutting types include X-cut, Z-cut, and rotary Y-cut (including Y-cut). 33 is 0, Z-cut 33 is 1.88, which is smaller than the e of AlN 33 Therefore, these two types of cuts cannot be used. For the cut of the rotating Y-cut (including the Y-cut), the corresponding Euler angle is (0°, β, 0°), where β varies in the range of 0° to 180°. 33 The curve with β changes is as follows Fig. 9 When the Euler angle is (0°, 123°, 0°), e 33 reaches the minimum value. Let |e 33 |≥1.55, then the range of Euler angles is (0°, 0°~54°, 0°), (0°, 90°~180°, 0°). Let |e 33 |≥2.16, then the range of Euler angles is (0°, 29°~34°, 0°), (0°, 97°~161°, 0°). Let |e 33 |≥3.27×0.9 (i.e. 0.9 times the maximum value), then the range of Euler angles is (0°, 109°~139°, 0°). Let |e 33 |≥3.27×0.8 (i.e. 0.8 times the maximum value), then the range of the Euler angle is (0°, 103°~148°, 0°).

[0068] The present application also provides a piezoelectric micromechanical ultrasonic transducer device, the device further comprising a substrate; the substrate is connected to one side surface of the single crystal piezoelectric film, and the substrate is made of silicon. Further, the device further comprises a dielectric layer; the substrate is connected to one side surface of the single crystal piezoelectric film through the dielectric layer.

[0069] For details, please refer to Fig. 10A As shown in FIG. 1 , it is the entire structure of the piezoelectric micromechanical ultrasonic transducer device PMUT in actual application. Fig. 10B for Fig. 10A AA' cross-sectional view. Among them, the core functional part of the device includes a LN or LT single crystal piezoelectric film 120 using the aforementioned crystal orientation, the thickness of the single crystal piezoelectric film 120 is 0.1 micron to 100 microns, and the preferred thickness range is 0.5 micron to 10 microns; electrode layers 130a and 140a attached to the upper and lower surfaces of 120. The remaining structural components also include electrode connecting parts 130c / 140c, electrode buses 130b / 140b, substrate 100, dielectric layer 110, cavity 150 located under electrode 140a, etc. The resonant frequency of the PMUT device is in the ultrasonic frequency band (20kHZ to 200MHz); it can be used for ultrasonic transmission and reception. The substrate 100 is made of silicon, and the dielectric layer 110 can also be omitted. Furthermore, according to application requirements and actual process conditions, the above-mentioned PMUT structure can undergo several changes. For example, it can be as follows Fig. 10C As shown, during the processing, the dielectric layer 110 and the substrate 100 below the functional part of the device are completely removed by etching and other processes.

[0070] In another embodiment of the present application, the dielectric layer and the single crystal piezoelectric film contact side comprises a cavity, and the second electrode layer is at least partially disposed in the cavity. The cavity is partially or completely filled with an acoustic loss layer. For details, please refer to Fig. 10B and Fig. 10D As shown, the cavity 150 may be filled with an acoustic loss layer 151, thereby increasing the propagation of acoustic waves into the medium 110 and the substrate 100, thereby reducing the Q value of the device and increasing the bandwidth of the device. The acoustic loss layer may completely or partially fill the cavity; the acoustic loss layer may be made of a polymer material.

[0071] For further information, please refer to Fig.10E As shown, the cavity 150 or the filling material 151 is omitted, so that the dielectric layer 110 is in direct contact with the lower electrode 140a of the functional area, and it can also reach part of the Fig. 10D Alternatively, the dielectric layer 110 may be further omitted, so that the lower electrode 140a is in contact with the substrate 100.

[0072] In one embodiment of the present application, the device further comprises an acoustic impedance matching layer, which is attached to the first electrode layer side of the single crystal piezoelectric film and covers the first electrode layer. Specifically, in order to enhance the ability of the device to transmit / receive sound waves to / from its surrounding medium (such as air), it can be like Fig.10F In this way, an acoustic impedance matching layer 160 is deposited on the surface of the upper electrode 130a of the PMUT device and the piezoelectric single crystal film 120, and the propagation / reception of sound waves to / from the environmental medium is optimized by impedance matching between the acoustic impedance matching layer 160 and the environmental medium. Generally, the acoustic impedance matching layer 160 can be made of a metal material different from that of the electrode 130a, or a dielectric material and a polymer material, or a combination of the above materials. In addition, the acoustic impedance matching layer 160 can also have other detailed structures such as thickness changes generated by patterning.

[0073] In order to perform beamforming or increase the acoustic wave transmission power, it is also possible to Fig. 10A The cells shown in are replicated in an array in certain directions within the plane. For example, Figure 10G In this way, the functional unit is expanded horizontally to obtain a functional unit including units C1, C2...C N-1 ,C N Array structure.

[0074] The present application also provides an electrical product, which has the piezoelectric micromechanical ultrasonic transducer as described above.

[0075] The beneficial technical effect of the present application is that the appropriate Euler angle is determined by the electromechanical coupling coefficient, the piezoelectric constant matrix and the type of single crystal piezoelectric material, thereby improving the performance during the application of the single crystal piezoelectric film, reducing unnecessary electrical losses, and improving energy utilization and conversion efficiency.

[0076] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the term "include", "comprise" or any other variant thereof is intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or equipment. In the absence of more restrictions, the elements defined by the sentence "including one..." do not exclude the existence of other identical elements in the process, method, article or equipment including the elements. The orientation or positional relationship indicated by the terms "upper", "lower", etc. is based on the orientation or positional relationship shown in the accompanying drawings, only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0077] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In the description of this specification, the description of reference terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiments of this specification. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0078] Specific embodiments are used in this application to illustrate the principles and implementation methods of this application. The description of the above embodiments is only used to help understand the method and core idea of ​​this application. At the same time, for those skilled in the art, according to the idea of ​​this application, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as a limitation on this application.

Claims

1. A piezoelectric MEMS transducer, characterized in that: The transducer comprises a first electrode layer, a second electrode layer and a single crystal piezoelectric film; The first electrode layer and the second electrode layer are respectively and correspondingly attached to the two side surfaces of the single crystal piezoelectric film; The single crystal piezoelectric film is a single crystal lithium niobate film or a single crystal lithium tantalate film, and the single crystal piezoelectric film has a determined cut of a target Euler angle, so that the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 6.4% or the absolute value of the e33 coefficient in the piezoelectric constant matrix is ​​not less than 1.55; Wherein, the piezoelectric MEMS transducer works in a thickness expansion mode.

2. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and nutation angle of the target Euler angle are within one period, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is 31.8%, the target Euler angle is (0°, 121°, 0°), (60°, 59°, 0°) or (120°, 121°, 0°).

3. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium niobate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 14.8%, the target Euler angle is (30°~90°, 34°~83°, 0°), (90°~150°, 97°~146°, 0°) or (-30°~30°, 97°~146°, 0°).

4. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium niobate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 6.4%, the target Euler angle is (0°, 26°~48°, 0°) or (0°, 89°~159°, 0°).

5. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and the nutation angle of the target Euler angle are within one period, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.9 times of 31.8%, the target Euler angle is (50°-70°, 50°-68°, 0°), (110°-130°, 112°-130°, 0°) or (-10°-10°, 112°-130°, 0°); When the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.8 times of 31.8%, the target Euler angle is (45°~75°, 46°~72°, 0°), (105°~135°, 108°~134°, 0°) or (-15°~15°, 108°~134°, 0°).

6. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium tantalate film, the precession angle and the nutation angle of the target Euler angle are within one cycle, and the piezoelectric coupling coefficient of the single crystal piezoelectric film is 11%, the target Euler angle is (0°, 121°, 0°), (60°, 59°, 0°) or (120°, 121°, 0°); When the piezoelectric coupling coefficient is not less than 6.4%, the target Euler angle is (29°~91°, 31°~80°, 0°), (89°~151°, 100°~149°, 0°) or (-31°~31°, 100°~149°, 0°).

7. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium tantalate film and the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.9 times of 11%, the target Euler angle is (49° to 71°, 48° to 69°, 0°), (109° to 131°, 111° to 132°, 0°) or (-11° to 11°, 111° to 132°, 0°); When the piezoelectric coupling coefficient of the single crystal piezoelectric film is not less than 0.8 times of 11%, the target Euler angle is (43°~77°, 42°~73°, 0°), (103°~137°, 107°~138°, 0°) or (-17°~17°, 107°~138°, 0°).

8. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium niobate film, the precession angle and the nutation angle of the target Euler angle are within one period, and the absolute value of the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is 4.64, the maximum value of the target Euler angle is (60°, 61°, 0°) or (180°, 61°, 0°), and the minimum value is (0°, 119°, 0°) or (120°, 119°, 0°); When the e33 coefficient in the piezoelectric constant matrix is ​​not less than 1.55, the target Euler angle is (0°, 14°-58°, 0°) or (0°, 84°-168°, 0°); When the e33 coefficient in the piezoelectric constant matrix is ​​not less than 2.16, the target Euler angle is (0°, 30°~48°, 0°) or (0°, 68°~157°, 0°).

9. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium niobate film, and the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.9 times of 4.64, the target Euler angle is (46° to 74°, 48° to 61°, 0°), (106° to 134°, 106° to 132°, 0°) or (-14° to 14°, 106° to 132°, 0°); When the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.8 times of 4.64, the target Euler angle is (38°~82°, 41°~79°, 0°), (98°~142°, 101°~139°, 0°) or (-22°~22°, 101°~139°, 0°).

10. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium tantalate film, the precession angle and the nutation angle of the target Euler angle are within one period, and the absolute value of the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is 3.27, the maximum value of the target Euler angle is (60°, 57°, 0°) or (180°, 57°, 0°), and the minimum value is (0°, 123°, 0°) or (120°, 123°, 0°); When the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 1.55, the target Euler angle is (0°, 0° to 54°, 0°) or (0°, 90° to 180°, 0°); When the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 2.16, the target Euler angle is (0°, 29°~34°, 0°) or (0°, 97°~161°, 0°).

11. The piezoelectric MEMS transducer according to claim 1, characterized in that: When the single crystal piezoelectric film is a single crystal lithium tantalate film, and the e33 coefficient in the piezoelectric constant matrix of the single crystal piezoelectric film is not less than 0.9 times of 3.27, the target Euler angle is (43° to 77°, 41° to 71°, 0°), (103° to 137°, 109° to 139°, 0°) or (-17° to 17°, 109° to 139°, 0°); When the single crystal piezoelectric film is not less than 0.8 times of 3.27, the target Euler angle is (33°~87°, 32°~77°, 0°), (93°~147°, 103°~148°, 0°) or (-27°~27°, 103°~148°, 0°).

12. The piezoelectric MEMS transducer according to claim 1, characterized in that: The transducer also includes a substrate; The substrate is in contact with one side surface of the single crystal piezoelectric film, and the substrate is made of silicon.

13. The piezoelectric MEMS transducer according to claim 12, characterized in that: A cavity is included between the substrate and the single crystal piezoelectric film, and the second electrode layer is at least partially disposed in the cavity.

14. The piezoelectric MEMS transducer according to claim 12, characterized in that: The transducer further comprises a dielectric layer; the substrate is connected to one side surface of the single crystal piezoelectric film through the dielectric layer.

15. The piezoelectric MEMS transducer according to claim 14, characterized in that: The side of the dielectric layer that is in contact with the single crystal piezoelectric film comprises a cavity, and the second electrode layer is at least partially disposed in the cavity.

16. The piezoelectric MEMS transducer according to claim 15, characterized in that: The cavity is partially or completely filled with an acoustic loss layer.

17. The piezoelectric MEMS transducer according to claim 12, characterized in that: The transducer further includes an acoustic impedance matching layer, which is attached to the first electrode layer side of the single crystal piezoelectric film and covers the first electrode layer.

18. An electrical product, characterized in that: The electrical product comprises the piezoelectric MEMS transducer according to any one of claims 1 to 17.

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