Ultrasonic transducer and preparation method thereof

Abstract

The invention discloses an ultrasonic transducer and a preparation method thereof, and relates to the technical field of ultrasonic transducers. The ultrasonic transducer comprises a piezoelectric layer, a substrate layer, a first conductive layer and a second conductive layer, the piezoelectric layer and the substrate layer are stacked in the thickness direction of the piezoelectric layer, the first conductive layer is arranged between the piezoelectric layer and the substrate layer, the second conductive layer is arranged on the side, away from the substrate layer, of the piezoelectric layer, the substrate layer is provided with a first cavity, and the first cavity is formed in the thickness direction of the piezoelectric layer. The first cavity corresponds to the second conductive layer, and the piezoelectric layer, the substrate layer, the first conductive layer and the second conductive layer are all made of transparent materials. Therefore, the piezoelectric layer, the substrate layer, the first conductive layer and the second conductive layer are all made of transparent materials, so that the ultrasonic transducer has light transmission, the ultrasonic transducer can be integrated in the fields of display screens, intelligent glass, optical imaging and the like, and ultrasonic detection functions such as under-screen fingerprint identification and the like can be realized; and the application range of the ultrasonic transducer can be expanded.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic transducers, and more particularly to an ultrasonic transducer and a method for manufacturing the same. Background Art

[0002] In related technologies, most of the materials used in piezoelectric micromachined ultrasonic transducers (pMUTs) do not have the property of transparency. For example, Au, Al, or Mo is generally used to make the conductive layer, PZT or AlN is used to make the piezoelectric layer, and Si or SiO2 is used to make the structural layer and the support layer. The piezoelectric micromachined ultrasonic transducer cannot transmit light, resulting in limitations in the applications of piezoelectric micromachined ultrasonic transducers in fields such as display screens, smart glass, photoacoustic imaging, and medical applications, severely restricting the applicable range of piezoelectric micromachined ultrasonic transducers. Therefore, there is an urgent need for a piezoelectric micromachined ultrasonic transducer with the property of transparency. Summary of the Invention

[0003] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, an object of the present invention is to provide an ultrasonic transducer that has good light transmittance.

[0004] The present invention further provides a method for manufacturing an ultrasonic transducer.

[0005] An ultrasonic transducer according to an embodiment of the present invention includes: a piezoelectric layer and a base layer. Along the thickness direction of the piezoelectric layer, the piezoelectric layer and the base layer are stacked; a first conductive layer and a second conductive layer. The first conductive layer is disposed between the piezoelectric layer and the base layer, and the second conductive layer is disposed on a side of the piezoelectric layer facing away from the base layer. The base layer has a first cavity, and along the thickness direction of the piezoelectric layer, the first cavity corresponds to the second conductive layer; the materials of the piezoelectric layer, the base layer, the first conductive layer, and the second conductive layer are all configured as transparent materials.

[0006] By configuring the materials of the piezoelectric layer, the base layer, the first conductive layer, and the second conductive layer as transparent materials, the ultrasonic transducer according to an embodiment of the present invention can have light transmittance, so that the ultrasonic transducer can be integrated into fields such as display screens, smart glass, and optical imaging, and can implement ultrasonic detection functions such as under-screen fingerprint recognition, which is beneficial to expanding the applicable range of the ultrasonic transducer.

[0007] According to some embodiments of the present invention, the ultrasonic transducer further includes: a bonding layer, which is connected between the base layer and the first conductive layer, and the material of the bonding layer is configured as a transparent material.

[0008] According to some embodiments of the present invention, one end of the first cavity facing the second conductive layer is open, or the first cavity penetrates through the base layer along the thickness direction of the piezoelectric layer.

[0009] According to some embodiments of the present invention, the central axis of the first cavity is coaxial with the central axis of the second conductive layer, the cross-sectional area of the first cavity is A, and the cross-sectional area of the second conductive layer is B, satisfying the relationship: 0.2 ≤ B / A ≤ 0.8.

[0010] According to some embodiments of the present invention, the cross-sectional shape of the first cavity is the same as the cross-sectional shape of the second conductive layer.

[0011] According to some embodiments of the present invention, the ultrasonic transducer further includes: a conductive part, the piezoelectric layer has a second cavity, the second cavity penetrates through the piezoelectric layer along the thickness direction of the piezoelectric layer, and a part of the conductive part is disposed in the second cavity and electrically connected to the first conductive layer.

[0012] According to some embodiments of the present invention, the material of the base layer is glass; and / or, the material of the bonding layer is a photo-curable adhesive; and / or, the material of the first conductive layer is indium tin oxide; and / or, the material of the second conductive layer is indium tin oxide; and / or, the material of the piezoelectric layer is lithium niobate or lithium tantalate.

[0013] According to some embodiments of the present invention, the thickness of the bonding layer is C, satisfying the relationship: 0.1 μm ≤ C ≤ 50 μm; and / or, the thickness of the first conductive layer is D, satisfying the relationship: 0.01 μm ≤ D ≤ 0.5 μm; and / or, the thickness of the second conductive layer is E, satisfying the relationship: 0.01 μm ≤ E ≤ 0.5 μm; and / or, the thickness of the piezoelectric layer is F, satisfying the relationship: 0.1 μm ≤ F ≤ 20 μm.

[0014] The method for manufacturing an ultrasonic transducer according to an embodiment of the present invention includes: etching a transparent substrate material to form a base layer having a first cavity; preparing a transparent conductive material on the surface of a transparent piezoelectric single crystal material wafer to form a stacked piezoelectric layer and a first conductive layer; bonding the base layer and the piezoelectric layer; thinning and polishing the piezoelectric layer; and preparing a second conductive layer on the surface of the piezoelectric layer facing away from the first conductive layer.

[0015] According to some embodiments of the present invention, the method for manufacturing an ultrasonic transducer further includes: etching the piezoelectric layer to form a second cavity penetrating through the piezoelectric layer; and preparing a conductive part partially disposed in the second cavity and electrically connected to the first conductive layer to lead out the first conductive layer.

[0016] The additional aspects and advantages of the present invention will be partially given in the following description, partially become obvious from the following description, or be understood through the practice of the present invention. Description of the Drawings

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and be readily understood from the following description of embodiments in conjunction with the accompanying drawings, in which:

[0018] Figure 1 is a schematic diagram of a piezoelectric material according to an embodiment of the present invention;

[0019] Figure 2 is a schematic diagram of a stacked piezoelectric layer and a first conductive layer according to an embodiment of the present invention;

[0020] Figure 3 is a schematic diagram of a base layer etched with a first cavity according to an embodiment of the present invention;

[0021] Figure 4 is a schematic diagram of a piezoelectric layer, a first conductive layer, and a bonding layer according to an embodiment of the present invention;

[0022] Figure 5 is Figure 3 and Figure 4 a schematic diagram of bonding;

[0023] Figure 6 is Figure 5 a schematic diagram of etching a second cavity;

[0024] Figure 7 is a schematic diagram of an ultrasonic transducer according to an embodiment of the present invention;

[0025] Figure 8 is a flowchart of a method for manufacturing an ultrasonic transducer according to an embodiment of the present invention;

[0026] Figure 9 is a schematic diagram of a specific embodiment of a method for manufacturing an ultrasonic transducer according to an embodiment of the present invention.

[0027] Reference numerals:

[0028] Piezoelectric layer 1; Second cavity 11;

[0029] Base layer 2; First cavity 21;

[0030] First conductive layer 3; Second conductive layer 4; Bonding layer 5; Conductive portion 6;

[0031] Ultrasonic transducer 10. Detailed Description of the Embodiment

[0032] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

[0033] Reference below Figures 1 - 9 An ultrasonic transducer 10 and a method for manufacturing the same according to an embodiment of the present invention are described.

[0034] like Figures 1 - 7 As shown, an ultrasonic transducer 10 according to an embodiment of the present invention includes: a piezoelectric layer 1, a substrate layer 2, a first conductive layer 3, and a second conductive layer 4. Along the thickness direction of the piezoelectric layer 1, the piezoelectric layer 1 and the substrate layer 2 are stacked, the first conductive layer 3 is arranged between the piezoelectric layer 1 and the substrate layer 2, the second conductive layer 4 is arranged on the side of the piezoelectric layer 1 away from the substrate layer 2, the substrate layer 2 has a first cavity 21, along the thickness direction of the piezoelectric layer 1, the first cavity 21 corresponds to the second conductive layer 4, and the materials of the piezoelectric layer 1, the substrate layer 2, the first conductive layer 3, and the second conductive layer 4 are all constructed as transparent materials.

[0035] Among them, the working principle of the ultrasonic transducer 10 relies on the piezoelectric effect, that is, certain materials will generate voltage when subjected to mechanical pressure, and the material will deform under the action of the electrical signal. The ultrasonic transducer 10 has a piezoelectric layer 1, a first conductive layer 3, and a second conductive layer 4. The first conductive layer 3 and the second conductive layer 4 can be used as two electrodes of the ultrasonic transducer 10. When the voltage signal acts on the piezoelectric layer 1 through one of the first conductive layer 3 and the second conductive layer 4, the piezoelectric layer 1 will deform, thereby generating ultrasonic waves. This process can convert the voltage signal into an ultrasonic signal. At the same time, when the ultrasonic signal acts on the piezoelectric layer 1, the piezoelectric layer 1 will generate a voltage signal. This process can convert the ultrasonic signal into an electrical signal for detecting ultrasonic waves.

[0036] Along the thickness direction of the piezoelectric layer 1, the piezoelectric layer 1 and the base layer 2 are stacked, the first conductive layer 3 is arranged between the piezoelectric layer 1 and the base layer 2, and the second conductive layer 4 is arranged on the side of the piezoelectric layer 1 away from the base layer 2. The piezoelectric layer 1, the base layer 2, the first conductive layer 3, and the second conductive layer 4 are stacked tightly, and the thickness of the piezoelectric layer 1, the base layer 2, the first conductive layer 3, and the second conductive layer 4 are all small, which can achieve the effect of miniaturization design.

[0037] The base layer 2 has a first cavity 21, which can be constructed as a blind hole or a through hole. The first cavity 21 can adjust the frequency, improve the signal strength, reduce the loss, enhance the sensitivity and optimize the propagation of sound waves. Along the thickness direction of the piezoelectric layer 1, the first cavity 21 corresponds to the second conductive layer 4 to reduce the reflection and scattering of the sound waves during the propagation process, thereby improving the acoustic performance of the ultrasonic transducer 10. Specifically, by reducing the interference of the sound waves on the propagation path, the sound waves can be more effectively propagated to the target area, thereby improving the directivity and sensitivity of the ultrasonic transducer 10.

[0038] The materials of the piezoelectric layer 1, the base layer 2, the first conductive layer 3, and the second conductive layer 4 are all configured as transparent materials to enhance the light transmittance of the ultrasonic transducer 10. The light-transmitting ultrasonic transducer 10 is beneficial to the display function of the device, enabling the ultrasonic transducer 10 to be integrated into devices such as display screens, touch screens, smart glass, and optical imaging, and capable of realizing ultrasonic detection functions such as under-screen fingerprint recognition, so as to expand the application scope of the ultrasonic transducer 10.

[0039] In the process of manufacturing the ultrasonic transducer 10, a transparent electrode material can be deposited on one side of a transparent layered piezoelectric material to form the non-thinned and polished piezoelectric layer 1 and the first conductive layer 3. A cavity is etched on the base material to form the base layer 2 with the first cavity 21, and then the base layer 2 and the first conductive layer 3 are bonded. After that, a thinning and polishing operation is performed on the non-thinned and polished piezoelectric layer 1 to obtain the thin-film piezoelectric layer 1. Finally, a layer of transparent electrode material is deposited on the side of the piezoelectric layer 1 facing away from the first conductive layer 3 and patterned to form the second conductive layer 4.

[0040] It can be understood that the piezoelectric layer 1, the base layer 2, the first conductive layer 3, and the second conductive layer 4 can all maintain high device performance to meet the requirements of efficient energy conversion, enabling the ultrasonic transducer 10 to be applied in fields such as transparent display and transparent ultrasonic imaging. Of course, the ultrasonic transducer 10 can also be applied to high-precision and high-integration sensor systems such as ultrasonic sensor arrays and micro-probes. This application does not limit this.

[0041] In the above embodiment, by configuring the materials of the piezoelectric layer 1, the base layer 2, the first conductive layer 3, and the second conductive layer 4 as transparent materials, the ultrasonic transducer 10 can have light transmittance, enabling the ultrasonic transducer 10 to be integrated into fields such as display screens, smart glass, and optical imaging, and capable of realizing ultrasonic detection functions such as under-screen fingerprint recognition, which is beneficial to expanding the application scope of the ultrasonic transducer 10.

[0042] In some embodiments of the present invention, as Figures 4 - 7 shown, the ultrasonic transducer 10 further includes: a bonding layer 5, the bonding layer 5 is connected between the base layer 2 and the first conductive layer 3, and the material of the bonding layer 5 is configured as a transparent material.

[0043] Among them, the bonding layer 5 can be used as the bonding material of the ultrasonic transducer 10. After obtaining the unthinned and polished piezoelectric layer 1 and the first conductive layer 3, the bonding layer 5 can be coated on the side of the first conductive layer 3 facing away from the unthinned and polished piezoelectric layer 1 by spin coating, and the base layer 2 and the bonding layer 5 are bonded together to bond the base layer 2 to the first conductive layer 3. After the bonding layer 5 is cured, the base layer 2 and the first conductive layer 3 become an integral body. The bonding layer 5 can also serve as the structural layer material of the ultrasonic transducer 10. The material of the bonding layer 5 can be constructed as a transparent material so that the ultrasonic transducer 10 has good light transmittance, making the application range of the ultrasonic transducer 10 wider.

[0044] In some embodiments of the present invention, as Figure 3 , Figures 5 - 7 shown, one end of the first cavity 21 facing the second conductive layer 4 is open, or the first cavity 21 penetrates through the base layer 2 along the thickness direction of the piezoelectric layer 1.

[0045] Among them, the first cavity 21 can be constructed as a blind hole, and the opening direction of the blind hole can face the second conductive layer 4. In other words, one end of the first cavity 21 facing the second conductive layer 4 is open. Or, the first cavity 21 can be constructed as a through hole, and the first cavity 21 penetrates through the base layer 2 along the thickness direction of the piezoelectric layer 1. Such a setting can further adjust the frequency, improve the signal strength, reduce the loss, and further enhance the sensitivity and optimize the sound wave propagation, and is convenient for the formation of the first cavity 21, reducing the manufacturing difficulty.

[0046] In some embodiments of the present invention, as Figure 7 shown, the center line of the first cavity 21 is coaxial with the center line of the second conductive layer 4, and the cross-sectional area of the first cavity 21 is A, and the cross-sectional area of the second conductive layer 4 is B, satisfying the relationship: 0.2 ≤ B / A ≤ 0.8.

[0047] Among them, the center line of the first cavity 21 can be coaxial with the center line of the second conductive layer 4 to reduce the reflection and scattering of sound waves during propagation, thereby improving the acoustic performance of the ultrasonic transducer 10. Specifically, by reducing the interference of sound waves on the propagation path, the sound waves can be more effectively propagated to the target area, thereby improving the directivity and sensitivity of the ultrasonic transducer 10.

[0048] The cross-sectional area of the first cavity 21 is A, and the cross-sectional area of the second conductive layer 4 is B. A and B can satisfy the relationship: 0.2 ≤ B / A ≤ 0.8. For example, B / A can be 0.2, 0.5, 0.8, etc. Such a setting can make the ratio of the cross-sectional area of the first cavity 21 to the cross-sectional area of the second conductive layer 4 reasonable, effectively improve the acoustic performance of the ultrasonic transducer 10, and further improve the directivity and sensitivity of the ultrasonic transducer 10.

[0049] In some embodiments of the present invention, the cross-sectional shape of the first cavity 21 is the same as the cross-sectional shape of the second conductive layer 4 .

[0050] Among them, the cross section of the first cavity 21 can be configured as a circle, a quadrilateral, a hexagon, etc., and the cross section of the second conductive layer 4 can be the same as the cross section of the first cavity 21. This arrangement can make the cross section of the first cavity 21 and the cross section of the second conductive layer 4 compatible, so that the acoustic performance of the ultrasonic transducer 10 can be more effectively improved, and the directivity and sensitivity of the ultrasonic transducer 10 can be further improved. In addition, it can be understood that the size of the first cavity 21 can be set according to the device frequency of the ultrasonic transducer 10.

[0051] In some embodiments of the present invention, Figure 7 As shown, the ultrasonic transducer 10 also includes: a conductive part 6 , the piezoelectric layer 1 has a second cavity 11 , the second cavity 11 penetrates the piezoelectric layer 1 along the thickness direction of the piezoelectric layer 1 , and part of the conductive part 6 is arranged in the second cavity 11 and electrically connected to the first conductive layer 3 .

[0052] Among them, the piezoelectric layer 1 can be etched with a second cavity 11, and the second cavity 11 penetrates the piezoelectric layer 1 along the thickness direction of the piezoelectric layer 1. The bottom wall of the second cavity 11 is the side of the first conductive layer 3 close to the piezoelectric layer 1. Part of the conductive part 6 is arranged in the second cavity 11, and the conductive part 6 is electrically connected to the first conductive layer 3, so as to lead the first conductive layer 3 to the side of the piezoelectric layer 1 away from the base layer 2 through the conductive part 6 (in short, the first conductive layer 3 can be led out through the conductive part 6), so as to facilitate the electrical connection of the first conductive layer 3 and the external power supply, so as to reduce the difficulty of electrically connecting the ultrasonic transducer 10 to the power supply, and such a setting structure is reasonable and the connection is reliable.

[0053] It should be noted that the material of the conductive part 6 can be the same as that of the first conductive layer 3 to reduce the difficulty of manufacturing the ultrasonic transducer 10 and to improve the conductivity between the conductive part 6 and the first conductive layer 3 .

[0054] As some embodiments of the present application, the material of the conductive portion 6 , the material of the first conductive layer 3 , and the material of the second conductive layer 4 are all the same, so as to significantly reduce the manufacturing difficulty of the ultrasonic transducer 10 .

[0055] In some embodiments of the present invention, the material of the base layer 2 is glass, and / or the material of the bonding layer 5 is photocurable adhesive, and / or the material of the first conductive layer 3 is tin-doped indium oxide (Indium Tin Oxide, ITO), and / or the material of the second conductive layer 4 is tin-doped indium oxide, and / or the material of the piezoelectric layer 1 is lithium niobate or lithium tantalate.

[0056] Among them, the material of the base layer 2 can be glass. Glass has good light transmittance, low cost, and good structural strength, so that the base layer 2 can be used as a support layer for the ultrasonic transducer 10 to support the ultrasonic transducer 10. The material of the first conductive layer 3 can be indium tin oxide. Indium tin oxide has good electrical conductivity, chemical stability, and light transmittance, so that the first conductive layer 3 can have good electrical conductivity, chemical stability, and light transmittance. The material of the second conductive layer 4 is indium tin oxide. Indium tin oxide has good electrical conductivity, chemical stability, and light transmittance, so that the second conductive layer 4 can have good electrical conductivity, chemical stability, and light transmittance.

[0057] The piezoelectric layer 1 can be constructed as a single crystal thin film material. The material of the piezoelectric layer 1 can be lithium niobate or lithium tantalate. Both lithium niobate and lithium tantalate have excellent piezoelectric properties. Lithium niobate has a large electro-optic coefficient, which can enable the piezoelectric layer 1 to process optical signals at high speed, and lithium niobate has good thermal stability. Lithium tantalate has a high Curie point temperature, good pyroelectric response, and piezoelectric properties. By using the above materials to prepare the ultrasonic transducer 10, the electrical conductivity and light transmittance of the ultrasonic transducer 10 can be comprehensively enhanced, so that the ultrasonic transducer 10 has excellent performance.

[0058] In some embodiments of the present invention, the thickness of the bonding layer 5 is C, satisfying the relationship: 0.1 μm ≤ C ≤ 50 μm, and / or, the thickness of the first conductive layer 3 is D, satisfying the relationship: 0.01 μm ≤ D ≤ 0.5 μm, and / or, the thickness of the second conductive layer 4 is E, satisfying the relationship: 0.01 μm ≤ E ≤ 0.5 μm, and / or, the thickness of the piezoelectric layer 1 is F, satisfying the relationship: 0.1 μm ≤ F ≤ 20 μm.

[0059] Among them, the thickness C of the bonding layer 5 satisfies the relationship: 0.1 μm ≤ C ≤ 50 μm. C can be 0.1 μm, 5 μm, 20 μm, 50 μm, etc. Such a setting can make the thickness of the bonding layer 5 reasonable, so that the bonding layer 5 can firmly bond the first conductive layer 3 and the base layer 2, and can also reduce the thickness of the bonding layer 5 to achieve the effect of miniaturized design.

[0060] The thickness D of the first conductive layer 3 satisfies the relationship: 0.01 μm ≤ D ≤ 0.5 μm. D can be 0.01 μm, 0.05 μm, 0.2 μm, 0.5 μm, etc. Such a setting can make the thickness of the first conductive layer 3 reasonable, so that the first conductive layer 3 has good electrical conductivity, and can also reduce the thickness of the first conductive layer 3 to achieve the effect of miniaturized design.

[0061] The thickness E of the second conductive layer 4 satisfies the relation: 0.01μm ≤ D ≤ 0.5μm. E can be 0.01μm, 0.05μm, 0.2μm, 0.5μm, etc. Such a setting can make the thickness of the second conductive layer 4 reasonable, so that the second conductive layer 4 has good electrical conductivity, and can also reduce the thickness of the second conductive layer 4 to achieve the effect of miniaturized design.

[0062] The thickness F of the piezoelectric layer 1 satisfies the relation: 0.1μm ≤ F ≤ 20μm. F can be 0.1μm, 1μm, 5μm, 20μm, etc. Such a setting can make the thickness of the piezoelectric layer 1 reasonable, so that the piezoelectric layer 1 can have good piezoelectric properties. By making the thicknesses of the bonding layer 5, the first conductive layer 3, the second conductive layer 4, and the piezoelectric layer 1 all conform to the above relations, the ultrasonic transducer 10 can have a small thickness dimension while having excellent performance, which is beneficial to the miniaturized design of the ultrasonic transducer 10.

[0063] Figure 8 FIG. is a flowchart of a method for manufacturing an ultrasonic transducer according to an embodiment of the present invention. The method for manufacturing an ultrasonic transducer includes the following steps:

[0064] S1, etching a transparent substrate material to form a base layer having a first cavity.

[0065] Among them, etching processes such as laser grooving, plasma etching, or wet etching can be used to etch blind holes or through holes on a transparent substrate material wafer as the back cavity of the base layer to form a base layer having a first cavity. The base layer can be used as the support layer of the ultrasonic transducer.

[0066] S2, preparing a transparent conductive material on the surface of a transparent piezoelectric single crystal material wafer to form a stacked piezoelectric layer and a first conductive layer.

[0067] Among them, a magnetron sputtering method can be used to deposit a transparent conductive material on one side surface of a transparent piezoelectric single crystal material wafer. The transparent conductive material can be ITO (conductive film layer material), etc., to form a stacked piezoelectric layer and a first conductive layer.

[0068] S3, bonding the base layer and the piezoelectric layer.

[0069] Among them, a spin coating method can be used to spin coat a transparent bonding material on the side of the piezoelectric layer facing away from the first conductive layer to form a bonding layer, and the base layer and the piezoelectric layer are bonded through the bonding layer to make the base layer and the piezoelectric layer an integral body. The bonding layer can also act as a structural layer after curing.

[0070] S4, thinning and polishing the piezoelectric layer.

[0071] Among them, a mechanical grinding, thinning, and polishing method can be adopted to perform a thinning and polishing operation on the unthinned and unpolished piezoelectric layer to obtain a thin-film piezoelectric layer.

[0072] S5. Prepare a second conductive layer on the surface of the piezoelectric layer facing away from the first conductive layer.

[0073] Among them, a Lift-off process can be adopted to prepare a second conductive layer on the surface of the piezoelectric layer facing away from the first conductive layer to complete the patterning of the second conductive layer.

[0074] Thus, through the preparation method of the present application, an ultrasonic transducer with light transmittance can be prepared, so that the ultrasonic transducer can be integrated into fields such as display screens, smart glass, and optical imaging, and can realize ultrasonic detection functions such as in-screen fingerprint recognition, so as to expand the application scope of the ultrasonic transducer.

[0075] In some embodiments of the present invention, the preparation method of the ultrasonic transducer further includes: etching the piezoelectric layer to form a second cavity penetrating the piezoelectric layer, and preparing a conductive portion partially disposed in the second cavity and electrically connected to the first conductive layer to lead out the first conductive layer.

[0076] Among them, a dry or wet etching method can be adopted to etch the piezoelectric layer to form a second cavity. Along the thickness direction of the piezoelectric layer, the second cavity penetrates the piezoelectric layer, so that a partial structure of the first conductive layer is exposed. The bottom wall of the second cavity is the side of the first conductive layer close to the piezoelectric layer, and a conductive portion partially disposed in the second cavity and electrically connected to the first conductive layer is prepared to lead out the first conductive layer. Specifically, a part of the conductive portion is disposed in the second cavity, and the conductive portion is electrically connected to the first conductive layer to lead the first conductive layer to the side of the piezoelectric layer facing away from the base layer (in short, the first conductive layer can be led out through the conductive portion), so as to facilitate the electrical connection between the first conductive layer and an external power supply.

[0077] Thus, the first conductive layer can be led out to facilitate the electrical connection between the first conductive layer and an external power supply, so as to reduce the difficulty of electrically connecting the ultrasonic transducer to the power supply. Moreover, the ultrasonic transducer prepared by the preparation method proposed in the present application can meet the application requirements of a light transmittance greater than 80% in the visible light band and has excellent light transmittance.

[0078] As Figure 9 shown, as a specific embodiment of the present invention, the above control method may include the following steps:

[0079] S01. Etch the transparent substrate material to form a base layer having a first cavity;

[0080] S02. Prepare a transparent conductive material on the surface of the transparent piezoelectric single crystal material wafer to form a stacked piezoelectric layer and a first conductive layer;

[0081] S03, Bond the base layer to the piezoelectric layer;

[0082] S04, Thinning and polishing the piezoelectric layer;

[0083] S05, Etch the piezoelectric layer to form a second cavity penetrating the piezoelectric layer;

[0084] S06, Prepare a second conductive layer on the surface of the piezoelectric layer facing away from the first conductive layer;

[0085] S07, Prepare a conductive part partially disposed in the second cavity and electrically connected to the first conductive layer to lead out the first conductive layer.

[0086] As a specific embodiment of the present invention, a specific embodiment of the preparation method of the ultrasonic transducer is introduced below, including the following steps:

[0087] Step 1: As Figure 1 shown, take a 6-inch transparent piezoelectric material lithium niobate or lithium tantalate material wafer, place the transparent piezoelectric material in an ultrasonic cleaning machine, and use acetone, ethanol, deionized water, etc. combined with ultrasonic cleaning at a power of 60w for 15min, then dry with nitrogen and vacuum dry at a temperature of 60°C to complete the pretreatment.

[0088] Step 2: As Figure 2 shown, adopt magnetron sputtering (PVD) technology to sputter transparent conductive material ITO on the surface of the pretreated lithium niobate or lithium tantalate bulk material wafer. The sputtering power is 300W, the sputtering time is 30min, the working gas is a mixed gas of argon and oxygen, the flow ratio of argon to oxygen is 20:1, the substrate temperature is 200°C, and the sputtering thickness of the transparent conductive material ITO is 150nm. After sputtering, an annealing operation is carried out, the annealing temperature is 300°C, and the annealing time is 30min. The above steps can improve the crystal structure of the first conductive layer, improve the conductivity and stability of the first conductive layer, reduce the internal stress of the first conductive layer, and ensure good adhesion between the first conductive layer and the substrate.

[0089] Step 3: As Figure 3 shown, select a 6-inch glass as the support layer material, and use glass through-hole (TGV) via formation technology (such as laser-induced deep etching technology (LIDE)) to prepare the first cavity. The diameter of the first cavity is 150μm, and the depth of the first cavity is 300μm. LIDE uses ultraviolet laser (355nm), the laser power is 5W, the pulse frequency is 100kHz, the pulse width is 20ns, and the scanning speed is 100mm / s. It is carried out in a nitrogen atmosphere at a temperature of 60°C. The etching rate is 3μm / min, and after 100min, the etching is completed. It is treated with deionized water combined with ultrasonic waves, dried with nitrogen, and the residues are removed to ensure the surface quality.

[0090] Step 4: As shown in Figure 4 , a bonding layer is prepared on the surface of the first conductive layer by spin-coating a photocurable adhesive. The bonding layer material is a photocurable adhesive. The thickness of the bonding layer is 5 μm, the spin-coating speed is 3000 rpm / min, and the spin-coating time is 60 s. After the photocurable adhesive is cured, it can be used as both the structural layer material and the bonding material. The first conductive layer structure and the base layer structure are bonded using the photocurable adhesive, and the bonding is carried out at room temperature through a photochemical reaction. After the bonding is completed, the transparent piezoelectric layer is mechanically thinned and polished to a thickness of 2 μm, and finally the structure shown in Figure 5 is formed.

[0091] Step 5: As shown in Figure 6 , the piezoelectric layer is dry-etched to expose part of the structure of the first conductive layer. Specifically, first, the piezoelectric layer is cleaned with acetone, isopropyl alcohol, and deionized water, and then a photoresist reversal resist (AZ4620) is spin-coated at a speed of 4000 rmp / min to obtain a photoresist with a thickness of 3 μm. Then, it is exposed for 7 s, secondarily exposed for 7 s, and developed for 60 s. Then, metal Cr is deposited with a deposition depth of 300 nm. Then, the excess pattern is stripped (i.e., the Lift-off process in the above embodiment), and the remaining metal serves as the mask layer for dry etching. Then, inductively coupled plasma (ICP) etching with a power of 1200 W and reactive ion (RIE) etching with a power of 150 W are used, the SF / H gas flow ratio is 6:1, the total gas flow is 12 sccm, and the reaction chamber pressure is 6 mTorr for etching until the first conductive layer is exposed. Then, the residual mask layer is removed by chemical mechanical polishing, and finally, ultrasonic cleaning is performed (as in Step 1).

[0092] Step 7: As shown in Figure 7 , finally, metal magnetron sputtering combined with the Lift-off process is used to complete the preparation of the second conductive layer and the lead-out of the first conductive layer. The specific parameters for magnetron sputtering the transparent conductive material ITO (150 nm) are as in (Lift-off in Step 5). Finally, the ultrasonic transducer proposed by the present invention is obtained.

[0093] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. They are only for the convenience of describing the present invention 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. Therefore, it should not be construed as a limitation of the present invention.

[0094] In the description of the present invention, the "first feature" and the "second feature" may include one or more of such features.

[0095] In the description of the present invention, the meaning of "a plurality of" is two or more.

[0096] In the description of the present invention, the first feature being "on" or "under" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween.

[0097] In the description of the present invention, the first feature being "on", "above", and "over" the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the first feature has a higher horizontal height than the second feature.

[0098] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0099] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the claims and their equivalents.

Claims

1. An ultrasonic transducer (10), characterized in that, include: A piezoelectric layer (1) and a base layer (2), wherein the piezoelectric layer (1) and the base layer (2) are stacked along a thickness direction of the piezoelectric layer (1); A first conductive layer (3) and a second conductive layer (4), wherein the first conductive layer (3) is arranged between the piezoelectric layer (1) and the base layer (2), and the second conductive layer (4) is arranged on a side of the piezoelectric layer (1) away from the base layer (2), and the base layer (2) has a first cavity (21), and along a thickness direction of the piezoelectric layer (1), the first cavity (21) corresponds to the second conductive layer (4); The piezoelectric layer (1), the base layer (2), the first conductive layer (3), and the second conductive layer (4) are all made of transparent materials.

2. The ultrasonic transducer (10) according to claim 1, characterized in that, Also includes: A bonding layer (5), the bonding layer (5) is connected between the base layer (2) and the first conductive layer (3), and the bonding layer (5) is made of a transparent material.

3. The ultrasonic transducer (10) according to claim 1, characterized in that, The first cavity (21) is open toward one end of the second conductive layer (4), or the first cavity (21) penetrates the base layer (2) along the thickness direction of the piezoelectric layer (1).

4. The ultrasonic transducer (10) according to claim 3, characterized in that, The center line of the first cavity (21) is coaxial with the center line of the second conductive layer (4), and the cross-sectional area of the first cavity (21) is A, and the cross-sectional area of the second conductive layer (4) is B, satisfying the relationship: 0.2≤B / A≤0.

8.

5. The ultrasonic transducer (10) according to claim 3, characterized in that, The cross-sectional shape of the first cavity (21) is the same as the cross-sectional shape of the second conductive layer (4).

6. The ultrasonic transducer (10) according to claim 1, wherein, Also includes: The piezoelectric layer (1) has a second cavity (11), the second cavity (11) penetrates the piezoelectric layer (1) along the thickness direction of the piezoelectric layer (1), and part of the conductive part (6) is arranged in the second cavity (11) and is electrically connected to the first conductive layer (3).

7. The ultrasonic transducer (10) according to claim 2, wherein The material of the base layer (2) is glass; And / or, the bonding layer (5) is made of light-curing adhesive; And / or, the material of the first conductive layer (3) is tin-doped indium oxide; And / or, the material of the second conductive layer (4) is tin-doped indium oxide; And / or, the material of the piezoelectric layer (1) is lithium niobate or lithium tantalate.

8. The ultrasonic transducer (10) according to claim 2, characterized in that, The thickness of the bonding layer (5) is C, which satisfies the relationship: 0.1 μm≤C≤50 μm; And / or, the thickness of the first conductive layer (3) is D, satisfying the relationship: 0.01 μm≤D≤0.5 μm; And / or, the thickness of the second conductive layer (4) is E, satisfying the relationship: 0.01 μm ≤ E ≤ 0.5 μm; And / or, the thickness of the piezoelectric layer (1) is F, satisfying the relationship: 0.1 μm≤F≤20 μm.

9. A method for preparing an ultrasonic transducer, characterized in that, include: Etching the transparent base material to form a base layer having a first cavity; Preparing a transparent conductive material on the surface of a transparent piezoelectric single crystal material wafer to form a stacked piezoelectric layer and a first conductive layer; bonding the substrate layer to the piezoelectric layer; Thinning and polishing the piezoelectric layer; A second conductive layer is formed on a surface of the piezoelectric layer facing away from the first conductive layer.

10. The preparation method of the ultrasonic transducer according to claim 9, characterized in that, Also includes: Etch the piezoelectric layer to form a second cavity penetrating the piezoelectric layer; Fabricate a conductive portion partially disposed in the second cavity and electrically connected to the first conductive layer to lead out the first conductive layer.

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