Ultrasonic transducer and preparation method thereof, ultrasonic fingerprint module and electronic equipment

Abstract

The embodiment of the invention provides an ultrasonic transducer, a preparation method of the ultrasonic transducer, an ultrasonic fingerprint module and electronic equipment. The preparation method of the ultrasonic transducer comprises the following steps: forming a bottom electrode on the upper surface of a substrate, and forming a piezoelectric layer covering the bottom electrode above the substrate; at least forming a seed metal layer on the upper surface of the piezoelectric layer; a first enclosure structure is formed above the substrate, and a containing space used for preparing a top electrode is defined above the piezoelectric layer through the first enclosure structure; and electrifying the seed metal layer, and electroplating at least the seed metal layer in the accommodating space to obtain a top electrode so as to obtain the ultrasonic transducer. According to the technical scheme provided by the embodiment of the invention, the ultrasonic transducer with relatively good performance can be prepared.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of ultrasonic transducers, and in particular to an ultrasonic transducer and a method for preparing the same, an ultrasonic fingerprint module, and an electronic device. Background Art

[0002] Ultrasonic transducers use the mechanical-electrical conversion characteristics of piezoelectric materials. On the one hand, they emit ultrasonic signals through the voltage excitation output by the driving circuit, and on the other hand, they convert the ultrasonic signals reflected from the outside world into electrical signals, thereby obtaining external sensing surface information. They can be widely used in areas including but not limited to biometric identification (for example, an example application can be used in ultrasonic fingerprint modules to collect fingerprint information for fingerprint identification). The performance of ultrasonic sensors obtained by existing preparation processes is poor. Therefore, it is necessary to improve the preparation process of ultrasonic transducers to improve the performance of the prepared ultrasonic transducers. Summary of the invention

[0003] The embodiments of the present application provide an ultrasonic transducer and a method for manufacturing the same, an ultrasonic fingerprint module, and an electronic device.

[0004] According to a first aspect of an embodiment of the present application, a method for preparing an ultrasonic transducer is provided, comprising: forming a bottom electrode on the upper surface of a substrate, and forming a piezoelectric layer covering the bottom electrode above the substrate; forming a seed metal layer on at least the upper surface of the piezoelectric layer; forming a first enclosure structure above the substrate, and using the first enclosure structure to enclose a receiving space above the piezoelectric layer for preparing a top electrode; energizing the seed metal layer, and electroplating the seed metal layer at least in the receiving space to obtain a top electrode, so as to obtain the ultrasonic transducer.

[0005] In some optional embodiments, the angle between at least one inner side wall of the first enclosure structure and the normal to the substrate is less than or equal to 45°, the angle between at least one outer side wall of the top electrode and the normal to the substrate is less than or equal to 45°, and the thickness of the first enclosure structure is not less than the thickness of the top electrode.

[0006] In some optional embodiments, the angle between at least one inner side wall of the first enclosure structure and the normal to the substrate is less than or equal to 5°, and the angle between at least one outer side wall of the top electrode and the normal to the substrate is less than or equal to 5°.

[0007] In some optional embodiments, forming a seed metal layer at least on the upper surface of the piezoelectric layer includes: using a low-temperature sputtering method to cover the upper surface and the outer wall of the piezoelectric layer with the seed metal layer, wherein the temperature of the low-temperature sputtering is controlled below 135°C.

[0008] In some optional embodiments, before forming the seed metal layer at least on the upper surface of the piezoelectric layer, the method further includes: forming a pad area on the upper surface of the substrate for electrical connection to an external circuit; forming the seed metal layer at least on the upper surface of the piezoelectric layer further includes: forming a whole layer of the seed metal layer on the upper surface of the substrate so that the pad area is covered by the seed metal layer; after obtaining the top electrode, the method further includes: at least partially removing the seed metal layer covering the pad area through an etching process to expose at least a portion of the pad area.

[0009] In some optional embodiments, the method further comprises: after obtaining the top electrode, at least partially removing the first enclosure structure.

[0010] In some optional embodiments, forming a first enclosure structure above the substrate includes: disposing a first photoresist above the substrate, and patterning and curing the first photoresist to form the first enclosure structure, wherein the curing temperature of the first photoresist during curing is controlled to be below 135°C; wherein patterning and curing the first photoresist includes: patterning the first photoresist to enclose a receiving space for preparing a top electrode above the piezoelectric layer, and then curing.

[0011] In some optional embodiments, before forming the piezoelectric layer, the method further includes: forming a second enclosing structure in the peripheral area of ​​the bottom electrode on the upper surface of the substrate, and allowing the second enclosing structure to expose the bottom electrode; forming the piezoelectric layer covering the bottom electrode above the substrate includes: preparing the piezoelectric layer above the bottom electrode exposed by the second enclosing structure.

[0012] In some optional embodiments, the prepared piezoelectric layer at least partially covers the upper surface of the second enclosure structure.

[0013] In some optional embodiments, forming a second enclosure structure in the peripheral area of ​​the bottom electrode on the upper surface of the substrate includes: setting a second photoresist on the upper surface of the substrate, and patterning and curing the second photoresist to form the second enclosure structure in the peripheral area of ​​the bottom electrode on the upper surface of the substrate; wherein patterning and curing the second photoresist includes: patterning the second photoresist to expose the bottom electrode, and then curing.

[0014] In some optional embodiments, forming a first enclosure structure above the substrate includes: forming a portion of the first enclosure structure on the upper surface of a second enclosure structure above the substrate, and there is a gap between the first enclosure structure formed on the upper surface of the second enclosure structure and the piezoelectric layer.

[0015] In some optional embodiments, after forming a piezoelectric layer covering the bottom electrode above the substrate, the method further includes: forming a second enclosing structure in a peripheral area of ​​the piezoelectric layer on the upper surface of the substrate, and allowing the second enclosing structure to expose at least a portion of the upper surface of the piezoelectric layer; forming a first enclosing structure above the substrate includes: forming a portion of the first enclosing structure on the upper surface of the second enclosing structure above the substrate.

[0016] In some optional embodiments, the second enclosure structure is formed in the peripheral area of ​​the piezoelectric layer on the upper surface of the substrate, including: setting a second photoresist on the upper surface of the substrate, and patterning and curing the second photoresist to form the second enclosure structure in the peripheral area of ​​the piezoelectric layer on the upper surface of the substrate, wherein the curing temperature of the second photoresist is controlled to be below 135°C during curing; wherein patterning and curing the second photoresist includes: patterning the second photoresist to expose at least part of the upper surface of the piezoelectric layer, and then curing.

[0017] In some optional embodiments, the first enclosure structure and / or the second enclosure structure uses at least one of the following materials: polyimide, poly(p-phenylene benzobisoxazole), epoxy resin, acrylic resin, and organic silicone composite material.

[0018] In some optional embodiments, the method further comprises: preparing a protective layer covering at least a portion of the top electrode.

[0019] In some optional embodiments, the metal material used for electroplating includes at least one of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead; or, the metal material used for electroplating includes an alloy material of at least two of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead.

[0020] In some optional embodiments, the method further includes: forming an excitation electrode on the upper surface of the substrate that is not in contact with the bottom electrode; forming a first enclosure structure above the substrate includes: forming a first enclosure structure above the substrate that is in contact with the excitation electrode; obtaining the top electrode includes: obtaining a top electrode that is at least partially connected to the excitation electrode, or obtaining a top electrode directly connected to an external circuit.

[0021] In some optional embodiments, the step of energizing the seed metal layer and electroplating the seed metal layer at least in the accommodation space includes: energizing the seed metal layer with a current not exceeding 50 amperes, electroplating the seed metal layer at least in the accommodation space for N steps, and the current density of the electroplating on the seed metal layer in the first step of the N steps is less than or equal to 2 amperes per square decimeter, and the current density of the electroplating on the seed metal layer in the second to N steps of the N steps is less than 8 amperes per square decimeter, wherein N ≥ 2 and is an integer.

[0022] According to a second aspect of an embodiment of the present application, an ultrasonic transducer is provided, which is prepared by the method for preparing an ultrasonic transducer as described in any one of the first aspects, and the ultrasonic transducer comprises: a substrate, a bottom electrode, a piezoelectric layer and a top electrode; the bottom electrode is located on the upper surface of the substrate, the piezoelectric layer is located above the substrate and covers the bottom electrode, and at least a portion of the top electrode is located above the piezoelectric layer; the top electrode is used to be applied with an excitation signal to excite the piezoelectric layer to emit an ultrasonic signal, and the bottom electrode is used to receive an ultrasonic detection signal generated between the top electrode and the bottom electrode when the returned ultrasonic signal acts on the piezoelectric layer.

[0023] According to a third aspect of the embodiments of the present application, an ultrasonic fingerprint module is provided, comprising: the ultrasonic transducer provided in the aforementioned second aspect.

[0024] According to a fourth aspect of the embodiments of the present application, an electronic device is provided, comprising: the ultrasonic transducer provided by the second aspect, or the ultrasonic fingerprint module provided by the third aspect.

[0025] The preparation scheme of the ultrasonic transducer in the embodiment of the present application, on the one hand, can form a piezoelectric layer covering the bottom electrode above the substrate, and form a seed metal layer at least on the upper surface of the piezoelectric layer, and form a first enclosure structure above the substrate, and the first enclosure structure is used to enclose a storage space for preparing the top electrode above the piezoelectric layer, and then the seed metal layer is energized, so that the seed metal layer at least in the storage space can be electroplated to obtain the top electrode, thereby effectively preparing an ultrasonic transducer including a substrate, a bottom electrode, a piezoelectric layer and a top electrode; on the other hand, since the present scheme prepares the top electrode of the ultrasonic transducer by electroplating on the seed metal layer, the electroplating method can be used to better control the preparation of the top electrode to achieve the required thickness, so that the preparation of the ultrasonic transducer The process is simpler and easier to control, and the thickness tolerance of the prepared top electrode is smaller, so that the quality stability of the top electrode is better, which can effectively improve the performance of the prepared ultrasonic transducer; on the other hand, since the present solution can electroplate the top electrode in the accommodating space surrounded by the first enclosure structure, it can more accurately ensure that the prepared top electrode is in a predetermined position, reduce the position error of the top electrode, and further improve the quality stability of the top electrode, and improve the performance of the prepared ultrasonic transducer; on the other hand, compared with the solution of preparing the top electrode by multi-layer silk screen printing in the related technology, the electroplating method in the present solution can also reduce the number of operating steps to reach the required thickness, which can effectively reduce the process difficulty and time cycle, and reduce the probability of production abnormalities. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0027] Figure 1 A schematic diagram of a preparation process of an ultrasonic transducer according to an example of the related art is shown.

[0028] Figure 2A A schematic diagram of an ultrasonic transducer according to an example of the present application is shown.

[0029] Figure 2B A schematic diagram showing another example of an ultrasonic transducer in the present application.

[0030] Figure 2C A schematic diagram of an ultrasonic transducer according to another example of the present application is shown.

[0031] Figure 2D Shows Figure 2AA schematic plan view of the ultrasonic transducer shown in FIG.

[0032] Figure 2E Shows Figure 2B A schematic plan view of the ultrasonic transducer shown in FIG.

[0033] Figure 2F A schematic diagram showing the angle between the outer sidewall of the top electrode and the normal line of the substrate in an example of the present application is shown.

[0034] Figure 2G A schematic diagram showing the angle between the outer sidewall of the top electrode and the normal line of the substrate of another example in the present application.

[0035] Figure 3 A flow chart of a method for preparing an ultrasonic transducer according to an example of the present application is shown.

[0036] Figure 4A The preparation method shown in this application Figure 2A Schematic diagram of an example preparation process of an ultrasonic transducer.

[0037] Figure 4B The preparation method shown in this application Figure 2B Schematic diagram of an example preparation process of an ultrasonic transducer.

[0038] Figure 4C The preparation method shown in this application Figure 2C Schematic diagram of an example preparation process of an ultrasonic transducer.

[0039] Figure 5 A schematic block diagram of an example ultrasonic fingerprint module in the present application is shown.

[0040] Fig. 6A A schematic block diagram of an electronic device according to an example of the present application is shown.

[0041] Figure 6B A schematic block diagram of another example electronic device in the present application is shown.

[0042] Figure 7 A schematic diagram showing an example of an ultrasonic transducer bonded under a screen of an electronic device in the present application.

[0043] Description of reference numerals:

[0044] 100, ultrasonic transducer; 10, substrate; 20, bottom electrode; 30, piezoelectric layer; 40, top electrode; 50, seed metal layer; 60, excitation electrode; 70, protective layer; 81, first enclosure structure; 82, second enclosure structure; 90, pad area; 200, ultrasonic fingerprint module; 300, electronic device; 310, adhesive layer; 320, screen. DETAILED DESCRIPTION

[0045] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments in the embodiments of the present application should fall within the scope of protection of the embodiments of the present application.

[0046] Ultrasonic transducers use the mechanical-electric conversion characteristics of piezoelectric materials. On the one hand, they emit ultrasonic signals through the voltage excitation output by the driving circuit, and on the other hand, they convert the ultrasonic signals reflected from the outside world into electrical signals, thereby obtaining information about the external sensing surface. They can be widely used in fields including but not limited to biometric identification (for example, an example application can be used in ultrasonic fingerprint modules, which can collect fingerprint information for fingerprint identification). For example, ultrasonic transducers are applied to ultrasonic fingerprint modules and set in specific areas of the screens of electronic devices including but not limited to smartphones. They can be used for fingerprint identification, and the distribution information of the peaks and valleys of fingerprints can be obtained. Through the difference in the strength of the reflected ultrasonic signals corresponding to the peaks and valleys, signal processing is performed to obtain fingerprint images and realize user identity authentication. The fingerprint identification system based on ultrasonic transducer sensing technology has the advantage that it is not only relatively insensitive to interference from wet, dry or dirty fingers, but also can pass through thick glass screens and other materials, such as screen protectors. Therefore, ultrasonic transducers provide more design freedom for electronic devices and can enhance the anti-interference and safety of products. In some exemplary ultrasonic transducer structures, there are circuit structures for transmitting ultrasonic excitation signals and processing ultrasonic echo signals, as well as a piezoelectric material layer with a high piezoelectric coefficient, that is, generally composed of a bottom electrode, a piezoelectric layer, and a top electrode. The performance of ultrasonic sensors obtained by the existing preparation process is poor, so it is necessary to improve the preparation process of ultrasonic transducers to improve the performance of the prepared ultrasonic transducers.

[0047] Combine the following Figure 1 The schematic diagram of the preparation process shown in FIG. 1 introduces a preparation process of an ultrasonic transducer in the related art. It should be understood that Figure 1 The related technologies shown in the preparation process are not necessarily prior art. Figure 1As shown, first, a bottom electrode 20' and a piezoelectric layer 30' covering the bottom electrode 20' are formed on the upper surface of the substrate 10'; then, a top electrode 40' can be prepared on the piezoelectric layer 30' by screen printing (abbreviated as silk screen printing) using silver paste as the top electrode material. According to the thickness requirement of the top electrode 40', limited by the technical characteristics and process capabilities of the silk screen printing process, a single printing usually cannot make the top electrode 40' reach the required thickness, so it is necessary to stack multiple layers of silk screen printing to achieve the required target thickness (for example, 3 to 5 layers of silk screen printing can be used as an example). After the top electrode 40' is prepared, an ultrasonic transducer can be obtained. Figure 1 In the example shown, the top electrode 40' is prepared by at least 4 layers of screen printing. Figure 1 As shown, in the process of preparing the ultrasonic transducer, an excitation electrode 60' and a pad area 90' can also be formed on the substrate 10', wherein the pad area 90' is used to connect to an external circuit, and the excitation electrode 60' is electrically connected to the pad area 90' and the top electrode 40', so as to obtain the excitation signal emitted by the external circuit through the pad area 90' and transmit it to the top electrode 40', so as to control the piezoelectric layer 30'. The pad area 90' may include a plurality of pads, and the excitation electrode 60' may be connected to a part of the pads, and the other pads of the pad area 90' may be used for the lead-out and access of other electrical signals, etc. For example, the specific steps of multi-layer silk screen printing are generally: firstly, the first layer of silk screen printing is performed to print the first layer of silver paste, and after the silver paste is baked and cured, the second layer of silk screen printing is performed, and then the baking and curing is performed, and then the third, fourth or more layers of silk screen printing are performed in sequence and the silver paste is baked and cured, until the target thickness required for the top electrode 40' is reached. As shown Figure 1 The preparation process shown in the figure has too many operation steps to achieve the required target thickness by preparing the top electrode 40' through multi-layer silk screen printing, and the silk screen screens used for each layer of silk screen printing are mostly of different screen designs, resulting in the need to switch screen production for each silk screen printing. Therefore, the process is more difficult, the time cycle is longer, and the probability of production abnormalities is higher.

[0048] about Figure 1The multi-layer screen printing method for preparing the top electrode of the ultrasonic transducer is shown in the figure. The technical characteristics of the screen printing process determine its process capabilities. For example: 1. The screen printing material needs to have a certain fluidity, so that the screen printing material can smoothly pass through the mesh of the screen printing screen and be printed on the substrate to be printed. If the viscosity is too high, printing will be difficult, and if the viscosity is too low, the material will easily overflow and controllable printing patterns cannot be achieved; 2. The screen printing screen has different mesh counts (mesh count definition: mesh count is the number of mesh holes per inch area, indicating the density between the silk threads). The higher the mesh count, the denser the screen, the smaller the mesh, the worse the passability of the screen printing material, the thinner the printing thickness obtained by a single printing, but the smaller the printing roughness, the smoother the surface of the material obtained by the screen printing, on the contrary, if the mesh is larger, the passability of the screen printing material is better, the printing thickness obtained by a single printing is thicker, but the greater the printing roughness, the more uneven the surface of the material obtained by the screen printing. Based on the above characteristics, if you want to obtain a top electrode 40' that meets product requirements, you need to comprehensively consider the viscosity of the screen printing material (such as silver paste), the mesh number of the screen, and the number of printings. If you want to obtain a lower material roughness for the top electrode 40', the mesh number of the screen printing plate cannot be too low, but the thickness obtained by a single printing will be limited, that is, the roughness and thickness of the material obtained by screen printing are usually mutually restrained; it is difficult for the top electrode 40' to achieve the required target thickness in a single printing, so Figure 1 The solution of the related art shown is generally to achieve a balance between roughness and thickness by combining screen printing plates of different mesh sizes and performing multiple screen printing. Obviously, the processing process of the above multiple printings is relatively cumbersome, the processing cycle is long, the steps are cumbersome, and the probability of production abnormalities is increased.

[0049] In addition, the cleanliness of different layers of silk-screened materials needs to be controlled, and foreign matter introduced in each layer may reduce the use effect of the ultrasonic transducer (for example, if the ultrasonic transducer is applied to the ultrasonic fingerprint module, the foreign matter introduced in each layer may cause the image recognition to fail, resulting in poor fingerprint recognition effect). The boundary position of different layers of silk-screened materials is misaligned due to the alignment deviation, and the fluctuation of the viscosity of the superimposed material itself and the flow in the physical state are easy to make the boundary position unfixed and irregular, which will directly lead to the appearance of the ultrasonic transducer. Failure. Furthermore, if the edge of the uncured material overflows to the electrically sensitive area on the substrate, it will cause a short circuit or discharge breakdown, which is easy to directly cause the acoustic performance of the piezoelectric layer of the ultrasonic transducer to fail. In addition, due to the technical characteristics of the multi-layer silk-screen printing process, the silver paste at the boundary of the top electrode presents a gentle slope morphology after leveling. This boundary morphology will produce a wider diffraction echo for the transmission of the ultrasonic signal, which will interfere with the use effect of the ultrasonic transducer to a certain extent (for example, if the ultrasonic transducer is applied to the ultrasonic fingerprint module, it can interfere with the fingerprint image quality to a certain extent and affect the accuracy of fingerprint recognition). Moreover, the more silk-screen layers there are, the greater the overall thickness tolerance of the top electrode. The thickness fluctuation will affect the frequency change when the ultrasonic transducer is used (for example, if the ultrasonic transducer is applied to an ultrasonic fingerprint module, it can be ultrasonic fingerprint recognition), which is not conducive to controlling within the required target frequency range, thereby reducing the use effect. The above-mentioned appearance and performance failures will have a significant impact on the processing yield of the ultrasonic transducer and affect the production cost of the ultrasonic transducer.

[0050] It should be understood that the ultrasonic transducer manufacturing method of the present invention does not adopt the method of preparing the top electrode by multi-layer screen printing, but prepares the top electrode by electroplating through a series of innovative steps, which can at least partially avoid the above Figure 1 The defects of the preparation scheme shown are eliminated, and the performance of the produced ultrasonic transducer is effectively improved, and the difficulty of the preparation process of the ultrasonic transducer is reduced.

[0051] The specific implementation of the technical solution of the embodiment of the present application is described below in conjunction with the accompanying drawings. It should be noted that for the convenience of illustration in each of the drawings, each structure may not be drawn according to the actual scale. Each of the drawings does not serve as any limitation to the embodiment of the present application.

[0052] Here, the structure of the ultrasonic transducer prepared in the embodiment of the present application is briefly introduced, so as to facilitate the specific description of its preparation method below. Figure 2A , Figure 2B , Figure 2CIn the example shown, an ultrasonic transducer 100 prepared by the preparation method of the first aspect in the embodiment of the present application comprises: a substrate 10, a bottom electrode 20, a piezoelectric layer 30 and a top electrode 40; the bottom electrode 20 is located on the upper surface of the substrate 10, the piezoelectric layer 30 is located above the substrate 10 and covers the bottom electrode 20, and at least a portion of the top electrode 40 is located above the piezoelectric layer 30; the top electrode 40 is used to be applied with an excitation signal to excite the piezoelectric layer 30 to emit an ultrasonic signal, and the bottom electrode 20 is used to receive an ultrasonic detection signal generated between the top electrode 40 and the bottom electrode 20 when the returned ultrasonic signal acts on the piezoelectric layer 30.

[0053] Optionally, the excitation signal may be an alternating current signal. Optionally, when the ultrasonic transducer 100 is used in an ultrasonic fingerprint module, the ultrasonic detection signal may be used to obtain a fingerprint image of a finger.

[0054] Figure 3 A flowchart of a method for preparing an ultrasonic transducer according to an example of the present application is shown. Figure 3 As shown, the method for preparing the ultrasonic transducer includes steps S102, S104, S106 and S108, specifically:

[0055] S102: forming a bottom electrode on the upper surface of the substrate, and forming a piezoelectric layer covering the bottom electrode above the substrate.

[0056] Optionally, the substrate 10 may be a silicon-based substrate or a TFT (Thin Film Transistor) substrate, or other types of substrates if required.

[0057] In the present application, the bottom electrode 20 may be formed on the upper surface of the substrate 10 by any suitable method, including but not limited to deposition, etching and the like.

[0058] Optionally, the piezoelectric layer 30 may include any piezoelectric material. For example, it may include at least one of PVDF (polyvinylidene difluoride) material, lead zirconate titanate material, and lithium niobate material. PVDF material may include PVDF, PVDF copolymer, etc. In the present application, the piezoelectric layer 30 may be formed above the substrate 10 in any suitable manner, which is not particularly limited herein. For example, it may be achieved by methods including but not limited to screen printing, coating, dry film lamination, etc., or it may be achieved by physical or chemical vapor deposition methods such as sputtering and evaporation.

[0059] In some optional embodiments, in the preparation Figure 2BWhen the ultrasonic transducer shown in , before forming the piezoelectric layer 30, the preparation method of the present application further includes: forming a second enclosure structure 82 in the peripheral area of ​​the bottom electrode 20 on the upper surface of the substrate 10, and making the second enclosure structure 82 expose the bottom electrode 20; in step S102, forming the piezoelectric layer 30 covering the bottom electrode 20 above the substrate 10 may include: preparing the piezoelectric layer 30 above the bottom electrode 20 exposed by the second enclosure structure 82. (For the convenience of reference below, this optional embodiment is recorded as "Optional Embodiment 1")

[0060] That is, in some optional embodiments, the second enclosure structure 82 may be prepared first, and then the piezoelectric layer 30 may be prepared (for example, the piezoelectric layer 30 may be combined with the piezoelectric layer 30). Figure 2B The ultrasonic transducer 100 and Figure 4B Schematic diagram of the preparation process for understanding).

[0061] Based on this, in the present application, during the preparation process of the ultrasonic transducer 100, by forming the second enclosure structure 82 in the peripheral area of ​​the bottom electrode 20 on the upper surface of the substrate 10, the piezoelectric layer 30 can be protected in the subsequent process, thereby preventing the subsequent preparation process from affecting the piezoelectric layer 30, improving the performance of the piezoelectric layer 30, and further improving the performance of the prepared ultrasonic transducer 100. For example, preventing the subsequent preparation process from affecting the piezoelectric layer 30 may include avoiding the use of solvents (such as, but not limited to, the solvents used in the etching process, the degumming process, etc. described in the optional embodiments below) and the like that affect the piezoelectric layer 30, etc.

[0062] In addition, if the top electrode 40 prepared subsequently can cover the second enclosure structure 82 while covering the piezoelectric layer 30, the top electrode 40 can pass through the second enclosure structure 82 instead of directly contacting the electrically sensitive area on the substrate 10, thereby avoiding short circuit or discharge breakdown. In addition, the second enclosure structure 82 can be used as a contact buffer between the piezoelectric layer 30 and the top electrode 40. The top electrode 40 can indirectly improve the structural stability between the piezoelectric layer 30 and the top electrode 40 by being located on the second enclosure structure 82, which is beneficial to improve the structural stability of the ultrasonic transducer 100 and improve the performance of the prepared ultrasonic transducer 100.

[0063] It can be seen that by providing and retaining the second enclosure structure 82 , better effects can be achieved for preparing the ultrasonic transducer 100 and improving the performance of the ultrasonic transducer 100 .

[0064] In some optional embodiments, referring to Figure 2B As shown, the prepared piezoelectric layer 30 at least partially covers the upper surface of the second enclosure structure 82. For example, Figure 2B As shown, a portion of both sides of the piezoelectric layer 30 covers the second enclosure structure 22 .

[0065] Optionally, when preparing the ultrasonic transducer 100, the second enclosure structure 82 can be retained, and when preparing the piezoelectric layer 30, the piezoelectric layer 30 can at least partially cover the upper surface of the second enclosure structure 82. Then, by covering the second enclosure structure 82, the structural stability between the piezoelectric layer 30 and the substrate 10 can be indirectly improved, which is beneficial to improve the structural reliability of the ultrasonic transducer 100 and improve the performance of the prepared ultrasonic transducer 100.

[0066] In some optional embodiments, forming a second enclosure structure 82 in the peripheral area of ​​the bottom electrode 20 on the upper surface of the substrate 10 may include: setting a second photoresist on the upper surface of the substrate 10, and patterning and curing the second photoresist to form the second enclosure structure 82 in the peripheral area of ​​the bottom electrode 20 on the upper surface of the substrate 10; wherein patterning and curing the second photoresist includes: patterning the second photoresist to expose the bottom electrode 20, and then curing it.

[0067] Optionally, the second photoresist is disposed on the upper surface of the substrate 10, which can be achieved by a series of coating methods such as spin coating, spray coating, roller coating, slit coating, etc., or by dry film lamination. Optionally, the second photoresist can be patterned and cured by any feasible method such as exposure and development, dry etching, wet etching, etc., which is not specifically limited here.

[0068] For example, taking spin coating as an example, in an optional method, a whole layer of second photoresist can be spin-coated on the upper surface of the substrate 10, and the second photoresist can be patterned and cured by exposure and development, so that the second photoresist is patterned to expose the bottom electrode 20, and then cured to form a second enclosure structure 82 in the peripheral area of ​​the bottom electrode 20 on the upper surface of the substrate 10.

[0069] It should be understood that the present application can effectively form a second enclosure structure 82 in the peripheral area of ​​the bottom electrode 20 on the upper surface of the substrate 10 by setting a second photoresist on the upper surface of the substrate 10 and patterning and curing the second photoresist, thereby facilitating the preparation of the ultrasonic transducer 100 and improving the performance of the ultrasonic transducer 100. In addition, the use of the second photoresist to form the second enclosure structure 82 is easy to process and manufacture, which can reduce the process difficulty of the ultrasonic transducer 100.

[0070] Optionally, for Figure 2B In the prepared ultrasonic transducer 100 shown, the second enclosure structure 82 may be a permanent structure retained in the ultrasonic transducer 100 .

[0071] In some other optional embodiments, different from the aforementioned "Optional Embodiment 1", the piezoelectric layer 30 may be prepared first and then the second enclosure structure 82 may be prepared (for example, it may be combined with Figure 2C The ultrasonic transducer 100 and Figure 4C That is, after "forming a piezoelectric layer covering the bottom electrode on the upper surface of the substrate" in step S102, the preparation method of the present application further includes: forming a second enclosure structure 82 in the peripheral area of ​​the piezoelectric layer 30 on the upper surface of the substrate 10, and making the second enclosure structure 82 expose at least part of the upper surface of the piezoelectric layer 30. (For ease of reference below, this optional embodiment is recorded as "Optional Embodiment 2")

[0072] Based on this, by forming a second enclosure structure 82 in the peripheral area of ​​the piezoelectric layer 30 on the upper surface of the substrate 10, the second enclosure structure 82 can subsequently form a protection for the piezoelectric layer 30, thereby preventing the subsequent preparation process from affecting the piezoelectric layer 30, improving the performance of the piezoelectric layer 30, and further improving the performance of the prepared ultrasonic transducer 100.

[0073] Optionally, forming a second enclosure structure 82 in the peripheral area of ​​the piezoelectric layer 30 on the upper surface of the substrate 10 may include: setting a second photoresist on the upper surface of the substrate 10, and patterning and curing the second photoresist to form the second enclosure structure 82 in the peripheral area of ​​the piezoelectric layer 30 on the upper surface of the substrate 10, wherein patterning and curing the second photoresist includes: patterning the second photoresist to expose at least part of the upper surface of the piezoelectric layer 30, and then curing; the curing temperature during the curing of the second photoresist is controlled to be below 135°C.

[0074] Optionally, the second photoresist is disposed on the upper surface of the substrate 10, which can be achieved by a series of coating methods such as spin coating, spray coating, roller coating, slit coating, etc., or by dry film lamination. Optionally, the second photoresist can be patterned and cured by any feasible method such as exposure and development, dry etching, wet etching, etc., which is not specifically limited here.

[0075] For example, taking spin coating as an example, in an optional method, a second photoresist can be spin-coated on the entire upper surface of the substrate 10, and the second photoresist can be patterned and cured by exposure and development, so that the second photoresist surrounds the outside of the piezoelectric layer 30 after curing, so as to form a second enclosure structure 82 in the peripheral area of ​​the piezoelectric layer 30 on the upper surface of the substrate 10.

[0076] It should be understood that the present application can effectively form a second enclosure structure 82 in the peripheral area of ​​the piezoelectric layer 30 on the upper surface of the substrate 10 by setting a second photoresist on the upper surface of the substrate 10 and patterning and curing the second photoresist, thereby facilitating the preparation of the ultrasonic transducer 100 and improving the performance of the ultrasonic transducer 100. In addition, the curing temperature of the second photoresist is controlled below 135°C during curing to effectively ensure the curing effect and avoid the risk of reduced piezoelectric performance or failure of the piezoelectric layer 30 due to high temperature, thereby ensuring the function of the piezoelectric layer 30. In addition, the use of the second photoresist to form the second enclosure structure 82 is easy to process and manufacture, which can reduce the process difficulty of the ultrasonic transducer 100.

[0077] Preferably, the curing temperature of the second photoresist is 70° C. to 110° C. Within this temperature range, the curing effect can be better ensured, and the risk of piezoelectric performance reduction or failure of the piezoelectric layer 30 due to high temperature can be better avoided, thereby better ensuring the function of the piezoelectric layer 30 .

[0078] Optionally, the second enclosure structure 82 may be a non-conductive material. Optionally, the second enclosure structure 82 may be made of an organic material, which may be, for example, at least one of the following materials: polyimide (PI), poly-p-phenylene benzobisoxazole (PBO), epoxy resin, acrylic resin and the like. The second enclosure structure 82 may also be made of an organic siloxane composite material. For example, an organic siloxane composite material may include, but is not limited to, an organic silicon ring, silicone rubber, silicone resin material and the like. It should be understood that in the present application, the second enclosure structure 82 may be effectively prepared by using the above-mentioned single material or a mixture of two different materials, so as to obtain an ultrasonic transducer with better performance.

[0079] S104: forming a seed metal layer at least on the upper surface of the piezoelectric layer.

[0080] In the present application, a seed metal layer 50 is formed at least on the upper surface of the piezoelectric layer 30. The seed metal layer 50 can serve as a cathode for electroplating (i.e., an electroplating substrate) to facilitate subsequent electroplating steps to obtain a top electrode 40, thereby realizing the preparation of an ultrasonic transducer 100.

[0081] Optionally, the thickness of the seed metal layer 50 is less than or equal to 2 um. The seed metal layer 50 in this thickness range is neither too thin nor too thick, has a relatively good step coverage capability on the undulating topography of the substrate, and can effectively meet the electroplating requirements.

[0082] The metal material type of the seed metal layer 50 is not specifically limited in the present application. Any metal material can be used as needed. Optionally, the seed metal layer 50 can be a single layer of metal. In some optional embodiments, the seed metal layer 50 can also be a double layer of metal, and the double layer of metal can be a first metal layer and a second metal layer, respectively. Optionally, the resistivity of the first metal layer is higher than the resistivity of the second metal layer. For example, the first metal layer can be made of titanium, titanium-tungsten alloy, and chromium, that is, the first metal layer can be at least one of a titanium layer, a titanium-tungsten alloy layer, and a chromium layer. The second metal layer can be made of copper, gold, and a nickel-vanadium alloy, that is, the second metal layer can be at least one of a copper layer, a gold layer, and a nickel-vanadium alloy layer. Optionally, when the seed metal layer 50 is formed on at least the upper surface of the piezoelectric layer 30 in step S104, a first metal layer can be formed on at least the upper surface of the piezoelectric layer 30, and then a second metal layer can be formed on the first metal layer, so that the first metal layer is located between the piezoelectric layer 30 and the second metal layer. In the subsequent step of electroplating, electroplating can be performed on the second metal layer.

[0083] In the present application, the benefit of using a double-layer metal layer for the seed metal layer 50 is: taking the first metal layer as a titanium layer, a titanium-tungsten alloy layer or a chromium layer, and the second metal layer as a copper layer, a gold layer or a nickel-vanadium alloy layer as an example, the second metal layer (such as a copper layer, a gold layer or a nickel-vanadium alloy layer) has a lower resistivity and better conductivity, thereby improving the electroplating effect and facilitating the stability of the electroplating process; and the first metal layer (such as a titanium layer, a titanium-tungsten alloy layer or a chromium layer) can improve the adhesion between the second metal layer and the upper surface of the substrate 10 including the piezoelectric layer 30, thereby improving the quality of the generated seed metal layer 50, and can serve as a barrier layer to prevent the metal material of the second metal layer from diffusing downward into the underlying material (such as the piezoelectric layer 30) during the preparation process, and the first metal layer can stably serve as the crystal nucleus for the growth of the second metal layer, promote the uniform deposition of the second metal layer, and further improve the quality of the seed metal layer 50, which is more conducive to the subsequent electroplating of the seed metal layer 50 to obtain a top electrode 40 with better performance, thereby improving the performance of the prepared ultrasonic transducer 100.

[0084] Optionally, when the seed metal layer includes a first metal layer and a second metal layer, the thickness of the first metal layer can be less than or equal to 1um, and the thickness of the second metal layer can be less than 2um. In this way, the first metal layer and the second metal layer within the thickness range are not too thin or too thick, and have a relatively good step coverage ability on the undulating terrain of the substrate, which can effectively meet the electroplating requirements.

[0085] Optionally, the sum of the thicknesses of the first metal layer and the second metal layer may be less than or equal to 2 um, so as to meet the requirement that the thickness of the seed metal layer 50 is less than 2 um in the aforementioned optional embodiment.

[0086] Optionally, the thickness of the first metal layer can be smaller than that of the second metal layer, so that the first metal layer can meet the requirement of blocking the metal material of the second metal layer from diffusing downward to the underlying material, and the second metal layer can also meet the thickness uniformity requirement when electroplating the top electrode.

[0087] In the present application, the above step S104 can be implemented in any manner to form the seed metal layer 50. For example, the seed metal layer 50 can be formed by screen printing or any optional manner. In some optional embodiments, step S104 includes: by low-temperature sputtering, the upper surface and the outer side wall of the piezoelectric layer 30 are covered by the seed metal layer 50, wherein the temperature of the low-temperature sputtering is controlled to be below 135°C.

[0088] Based on this, the seed metal layer 50 can be effectively prepared by low-temperature sputtering, and the temperature is controlled below 135°C. On the basis of ensuring the effect of the seed metal layer 50 prepared by low-temperature sputtering, the risk of piezoelectric performance degradation or failure of the piezoelectric layer 30 due to high temperature can be effectively avoided, thereby ensuring the function of the piezoelectric layer 30.

[0089] Preferably, the temperature of low-temperature sputtering is 70° C. to 110° C. Within this temperature range, the effect of low-temperature sputtering can be better ensured, and the risk of piezoelectric performance degradation or failure of the piezoelectric layer 30 due to high temperature can be better avoided, thereby better ensuring the function of the piezoelectric layer 30 .

[0090] Optionally, a whole layer of seed metal layer 50 can be formed on the upper surface of the substrate 10 (for example, by low-temperature sputtering), so that the upper surface and the outer side wall of the piezoelectric layer 30 are covered by the seed metal layer 50. It should be understood that by forming a whole layer of seed metal layer 50 on the upper surface of the substrate 10, the seed metal layer 50 can be formed on any existing structure on the upper surface of the substrate 10, which can reduce the difficulty of the process.

[0091] S106: forming a first enclosure structure above the substrate, and forming a receiving space for preparing a top electrode above the piezoelectric layer through the first enclosure structure.

[0092] The present application can form a first enclosure structure 81 above the substrate 10, and the first enclosure structure 81 can enclose a holding space above the piezoelectric layer 30. When the top electrode 40 is subsequently prepared, it can be used as an enclosure to ensure that the prepared top electrode 40 is in a predetermined position more accurately, reduce the position error of the top electrode 40, and further improve the quality stability of the top electrode 40, thereby improving the performance of the prepared ultrasonic transducer 100.

[0093] In some optional embodiments, before obtaining the ultrasonic transducer 100, the first enclosure structure 81 may be removed (which may be combined with the following related embodiments and Figure 4B), is not retained in the ultrasonic transducer 100, and is only used as a temporary structure for preparing the ultrasonic transducer 100.

[0094] In some optional embodiments, the angle between at least one inner side wall of the first enclosure structure 81 formed in step S106 and the normal to the substrate 10 is less than or equal to 45°, the angle between at least one outer side wall of the subsequently prepared top electrode 40 and the normal to the substrate 10 is less than or equal to 45°, and the thickness of the first enclosure structure 81 is not less than the thickness of the top electrode 40.

[0095] for Figure 1 As for the multi-layer silk-screen printing method for preparing the top electrode shown, due to the technical characteristics of the silk-screen printing process, the silver paste at the boundary of the top electrode presents a gentle slope after leveling. This boundary morphology will produce a wider diffraction echo for the transmission of the ultrasonic signal, which will interfere with the use effect of the ultrasonic transducer to a certain extent (for example, if the ultrasonic transducer is applied to the ultrasonic fingerprint module, it may interfere with the fingerprint image quality to a certain extent and affect the fingerprint recognition accuracy).

[0096] In the above optional implementation scheme of the present scheme, the angle between at least one inner side wall of the first enclosure structure 81 and the normal line of the substrate 10 is made less than or equal to 45° during preparation, so that the thickness of the first enclosure structure 81 is not less than the thickness of the top electrode 40, so that when the seed metal layer in the accommodation space is electroplated in the subsequent step, through the limitation of the first enclosure structure 81, at least one outer side wall of the electroplated top electrode 40 can have an angle less than or equal to 45° with the normal line of the substrate 10, thereby avoiding the disadvantages of the multi-layer screen printing scheme in the related art, and effectively reducing the diffraction echo of the ultrasonic signal caused by the boundary morphology of the top electrode 40, thereby reducing the interference to the prepared ultrasonic transducer 100 when in use, and improving the use effect of the ultrasonic transducer 100. For example, if the ultrasonic transducer 100 is applied to an ultrasonic fingerprint module, since the angle between at least one outer side wall of the top electrode 40 and the normal line of the substrate 10 is less than or equal to 45°, the diffraction echo is reduced, thereby reducing the interference to the fingerprint image quality, and effectively improving the fingerprint recognition accuracy. Furthermore, the above-mentioned angle range has low requirements on the manufacturing process, and it is relatively easy to form the first enclosure structure 81 and the top electrode 40, thereby reducing the difficulty of manufacturing the ultrasonic transducer.

[0097] Optionally, the normal line of the substrate 10 may be a straight line perpendicular to the upper surface of the substrate 10. Figure 2F and Figure 2G See the schematic diagram for understanding.

[0098] For example, you can combine Figure 4A and Figure 4BAs shown, the examples shown are all examples in which the thickness of the first enclosure structure 81 is greater than the thickness of the top electrode 40 .

[0099] In some optional embodiments, the angles between each inner side wall of the first enclosure structure 81 and the normal of the substrate 10 are all less than or equal to 45°. The angles between each outer side wall of the top electrode 40 obtained in the embodiment of the present application and the normal of the substrate 10 are all less than or equal to 45°. This is to better reduce the diffraction echo of the ultrasonic signal caused by the boundary morphology of the top electrode 40, thereby better reducing the interference to the prepared ultrasonic transducer 100 during use, and better improving the use effect of the ultrasonic transducer 100. In addition, the above-mentioned angle range has low requirements on the preparation process, and it is relatively easy to form the first enclosure structure 81 and the top electrode 40, thereby reducing the difficulty of preparing the ultrasonic transducer.

[0100] Preferably, the angle between at least one inner side wall of the first enclosure structure 81 and the normal of the substrate 10 is less than or equal to 5°. Preferably, the angle between at least one outer side wall of the top electrode 40 obtained in the embodiment of the present application and the normal of the substrate 10 is less than or equal to 5°. In this case, it can be basically considered that at least one outer side wall of the top electrode 40 is perpendicular to the substrate 10, which can better reduce the diffraction echo of the ultrasonic signal caused by the boundary morphology of the top electrode 40, thereby reducing the interference to the prepared ultrasonic transducer 100 during use, and improving the use effect of the ultrasonic transducer 100.

[0101] Preferably, the angles between each inner side wall of the first enclosure structure 81 and the normal of the substrate 10 are all less than or equal to 5°. Preferably, the angles between each outer side wall of the top electrode 40 obtained in the embodiment of the present application and the normal of the substrate 10 are all less than or equal to 5°. In this case, it can be basically considered that each outer side wall of the top electrode 40 is perpendicular to the substrate 10, so as to better reduce the diffraction echo of the ultrasonic signal caused by the boundary morphology of the top electrode 40, thereby better reducing the interference to the prepared ultrasonic transducer 100 during use, and better improving the use effect of the ultrasonic transducer 100.

[0102] Preferably, the angle between at least one inner sidewall of the first enclosure structure 81 and the normal line of the substrate 10 is equal to 0°. Preferably, the angle between at least one outer sidewall of the top electrode 40 and the normal line of the substrate 10 is equal to 0°.

[0103] Based on this, the diffraction echo of the ultrasonic signal caused by the boundary morphology of the top electrode 40 can be better reduced, thereby better reducing the interference to the ultrasonic transducer 100 during use, and better improving the use effect of the ultrasonic transducer 100.

[0104] Preferably, the angles between each inner sidewall of the first enclosure structure 81 and the normal line of the substrate 10 are all equal to 0°. Preferably, the angles between each outer sidewall of the top electrode 40 and the normal line of the substrate 10 are all equal to 0°.

[0105] It should be understood that the closer the angle between each inner side wall of the first enclosure structure 81 and the normal line of the substrate 10 is to 0°, the closer the angle between each outer side wall of the top electrode 40 prepared by electroplating and the normal line of the substrate 10 is to 0°. In addition, the closer the angle between each outer side wall of the top electrode 40 and the normal line of the substrate 10 is to 0°, the closer the outer side wall and the substrate 10 are to verticality, and the better the use effect of the ultrasonic transducer 100 is.

[0106] For example, see Figure 2F The schematic diagram shown shows the angle between the inner side wall of the first enclosure structure 81 and the normal line of the substrate 10, and the angle between the outer side wall of the top electrode 40 and the normal line of the substrate 10. Both angles are θ, and the angle θ is less than or equal to 45°. Preferably, the angle θ is less than or equal to 5°. Preferably, the angle θ is equal to 0°, that is, the inner side wall of the first enclosure structure 81 and the outer side wall of the top electrode 40 are perpendicular to the normal line of the substrate 10.

[0107] For example, refer to Figure 2G The schematic diagram shown shows the angle between the inner side wall of the first enclosure structure 81 and the normal line of the substrate 10 in another example, and the angle between the outer side wall of the top electrode 40 and the normal line of the substrate 10 in another example, both angles are θ, and the angle θ is less than or equal to 45°. Preferably, the angle θ is less than or equal to 5°. Preferably, the angle θ is equal to 0°, that is, the inner side wall of the first enclosure structure 81 and the outer side wall of the top electrode 40 are perpendicular to the normal line of the substrate 10.

[0108] For example, you can combine Figure 4A The preparation process, Figure 4B The preparation process, Figure 4C For understanding the preparation process in, it is shown that the angle θ is equal to 0°, and a similar example in which the inner side wall of the first enclosure structure 81 and the outer side wall of the top electrode 40 are perpendicular to the normal of the substrate 10.

[0109] It should be understood that the above figures are merely schematic diagrams for ease of understanding and are not intended to limit the embodiments of the present application.

[0110] The present application does not specifically limit the manner of forming the first enclosure structure 81. In some optional embodiments, in step S106, a first photoresist may be disposed on the substrate 10, and the first photoresist may be patterned and cured to form the first enclosure structure 81, wherein the curing temperature of the first photoresist during curing is controlled to be below 135°C; wherein patterning and curing the first photoresist includes: patterning the first photoresist to enclose a receiving space for preparing the top electrode 40 above the piezoelectric layer 30, and then curing.

[0111] Optionally, the first photoresist is disposed on the upper surface of the substrate 10, which can be achieved by a series of coating methods such as spin coating, spray coating, roller coating, slit coating, etc., or by dry film lamination. Optionally, the first photoresist can be patterned and cured by any feasible method such as exposure and development, dry etching, wet etching, etc., which is not specifically limited here.

[0112] For example, taking spin coating as an example, in an optional method, a whole layer of the first photoresist can be spin-coated on the upper surface of the substrate 10, and the first photoresist can be patterned and cured by exposure and development, so that the first photoresist is patterned above the piezoelectric layer 30 to form a receiving space for preparing the top electrode 40 and then cured to form a first enclosure structure 81.

[0113] It should be understood that the present application can effectively form a first enclosure structure 81 above the substrate that can enclose a storage space for preparing the top electrode 40 above the piezoelectric layer by setting a first photoresist above the substrate 10 and patterning and curing the first photoresist, thereby facilitating the preparation of the ultrasonic transducer 100 and improving the performance of the ultrasonic transducer 100. In addition, the curing temperature during the curing of the first photoresist is controlled below 135°C to effectively ensure the curing effect and avoid the risk of reduced piezoelectric performance or failure of the piezoelectric layer 30 due to high temperature, thereby ensuring the function of the piezoelectric layer 30.

[0114] Preferably, the curing temperature of the first photoresist is 70° C. to 110° C. Within this temperature range, the curing effect can be better guaranteed, and the risk of piezoelectric performance reduction or failure of the piezoelectric layer 30 due to high temperature can be better avoided, thereby better ensuring the function of the piezoelectric layer 30 .

[0115] Optionally, the first enclosure structure 81 may be a non-conductive material. Optionally, the first enclosure structure 81 may be made of an organic material, which may be, for example, at least one of the following materials: polyimide (PI), poly-p-phenylene benzobisoxazole (PBO), epoxy resin, acrylic resin and the like. The first enclosure structure 81 may also be made of an organic siloxane composite material. For example, an organic siloxane composite material may include, but is not limited to, an organic silicon ring, silicone rubber, silicone resin material and the like. It should be understood that in the present application, the first enclosure structure 81 may be effectively prepared by using the above-mentioned single material or a mixture of two different materials, so as to obtain an ultrasonic transducer with better performance.

[0116] For the optional embodiment (i.e., "optional embodiment 1") in which the second enclosure structure 82 is prepared first and then the piezoelectric layer 30 is prepared, optionally, step S106 of forming the first enclosure structure 81 above the substrate 10 may include: forming a portion of the first enclosure structure 81 on the upper surface of the second enclosure structure 82 above the substrate 10, and a gap exists between the first enclosure structure 81 formed on the upper surface of the second enclosure structure 82 and the piezoelectric layer 30. The existence of the gap allows a portion of the top electrode material to extend beyond the piezoelectric layer 30 after electroplating and to indirectly contact the second enclosure structure 82 through the seed metal layer 50, and such contact can enhance the bonding force.

[0117] It should be understood that the above optional embodiment of the present application forms a portion of the first enclosure structure 81 on the upper surface of the second enclosure structure 82 above the substrate 10, and a gap is formed between the first enclosure structure 81 formed on the upper surface of the second enclosure structure 82 and the piezoelectric layer 30, so that the subsequent electroplating of the top electrode 40 can be carried out within the gap, and the top electrode 40 can be located on the second enclosure structure 82, so that on the one hand, the electroplated top electrode 40 can be supported to exceed the piezoelectric layer 30, so that the electroplated top electrode 40 can be blocked by the second enclosure structure 82 while covering the piezoelectric layer 30 without being directly On the other hand, the second enclosure structure 82 can be used as a contact buffer between the piezoelectric layer 30 and the top electrode 40. The top electrode 40 can be located on the second enclosure structure 82 to indirectly improve the structural stability between the piezoelectric layer 30 and the top electrode 40, which is beneficial to improve the structural stability of the ultrasonic transducer 100 and the performance of the prepared ultrasonic transducer 100. On the other hand, the top electrode 40 obtained in this way can protect at least part of the piezoelectric layer 30 with the second enclosure structure 82 (see Figure 2BAs shown in the structure of the prepared ultrasonic transducer 100, the piezoelectric layer 30 can be prevented from being affected in the subsequent preparation process, the performance of the piezoelectric layer 30 can be improved, and the performance of the prepared ultrasonic transducer 100 can be further improved.

[0118] In addition, since the obtained top electrode 40 can protect at least part of the piezoelectric layer 30 together with the second enclosure structure 82, the process compatibility is improved, the process difficulty is reduced, and the range of materials that can be selected in the subsequent preparation process such as solvents (such as photoresist stripping liquid, metal etching liquid, etc.) used in the stripping process and etching process can be expanded.

[0119] For the optional embodiment (i.e., “optional embodiment two”) in which the piezoelectric layer 30 is first prepared and then the second enclosure structure 82 is prepared, optionally, step S106 forms the first enclosure structure 81 above the substrate 10, which may include: forming a portion of the first enclosure structure 81 on the upper surface of the second enclosure structure 82 above the substrate 10.

[0120] It should be understood that the above-mentioned optional embodiments in the present application form a portion of the first enclosure structure 81 on the upper surface of the second enclosure structure 82 above the substrate 10, so that the top electrode 40 obtained by subsequent electroplating can protect at least part of the piezoelectric layer 30 together with the second enclosure structure 82, thereby avoiding the piezoelectric layer 30 from being affected in the subsequent preparation process, improving the performance of the piezoelectric layer 30, and further improving the performance of the prepared ultrasonic transducer 100.

[0121] In some optional embodiments, the preparation method of the embodiment of the present application also includes: forming an excitation electrode 60 on the upper surface of the substrate 10 that is not in contact with the bottom electrode 20; on this basis, forming a first enclosure structure 81 above the substrate 10 in step S106, which may include: forming a first enclosure structure 81 in contact with the excitation electrode 60 above the substrate 10; and subsequently obtaining the top electrode 40, which may be a top electrode 40 that is at least partially connected to the excitation electrode 60.

[0122] Based on this, an excitation electrode 60 is formed on the upper surface of the substrate 10, and a first enclosure structure 81 in contact with the excitation electrode 60 is formed above the substrate 10, so that a top electrode 40 at least partially connected to the excitation electrode 60 can be electroplated in a subsequent step, and the excitation electrode 60 can obtain an excitation signal, thereby effectively transmitting the excitation signal to the top electrode 40 connected thereto, so that the prepared ultrasonic transducer 100 can achieve the corresponding function.

[0123] S108: electrify the seed metal layer, and electroplate the seed metal layer at least in the receiving space to obtain a top electrode, so as to obtain an ultrasonic transducer.

[0124] In the present application, the seed metal layer 50 can be used as a cathode for electroplating (i.e., an electroplating substrate). By energizing the seed metal layer 50, the seed metal layer 50 at least in the receiving space is electroplated to obtain a top electrode 40, and then the ultrasonic transducer 100 can be obtained.

[0125] Based on this, the embodiment of the present application, through the preparation method of the above steps S102 to S108, on the one hand, can form a piezoelectric layer covering the bottom electrode above the substrate, and form a seed metal layer on at least the upper surface of the piezoelectric layer, and form a first enclosure structure above the substrate, and the first enclosure structure is used to enclose a holding space for preparing the top electrode above the piezoelectric layer, and then the seed metal layer is energized, so that the seed metal layer in at least the holding space can be electroplated to obtain the top electrode, thereby effectively preparing an ultrasonic transducer including a substrate, a bottom electrode, a piezoelectric layer and a top electrode; on the other hand, since the present scheme prepares the top electrode of the ultrasonic transducer by electroplating on the seed metal layer, the electroplating method can be better controlled to prepare the top electrode to achieve the required thickness, so that the ultrasonic transducer The preparation process of the ultrasonic transducer is simpler and easier to control, and the thickness tolerance of the prepared top electrode is smaller, so that the quality stability of the top electrode is better, thereby effectively improving the performance of the prepared ultrasonic transducer; on the other hand, since the present scheme can obtain the top electrode by electroplating in the accommodating space surrounded by the first enclosure structure, it is possible to more accurately ensure that the prepared top electrode is in a predetermined position, reduce the position error of the top electrode, and further improve the quality stability of the top electrode, and improve the performance of the prepared ultrasonic transducer; on the other hand, compared with the scheme of preparing the top electrode by multi-layer silk screen printing in the related art, the electroplating method in the present scheme can also reduce the number of operating steps to reach the required thickness, which can effectively reduce the process difficulty and time cycle, and reduce the probability of production abnormalities.

[0126] In the present application, the top electrode 40 obtained by electroplating is realized based on the electrolysis principle. On the cathode of the electroplating (electroplating substrate, i.e., the seed metal layer 50), the metal cations accept electrons and are reduced to metal atoms and deposited to form a dense metal coating. The metal coating obtained by electroplating is dense inside and has no abnormalities such as stratification, holes, and resin agglomeration. It should be understood that the metal coating after the electroplating is completed is also the top electrode 40, so the performance of the top electrode 40 is better, which is conducive to improving the performance of the prepared ultrasonic transducer 100.

[0127] It should also be understood that Figure 1In the scheme of preparing the top electrode by multi-layer screen printing, the screen printing material is generally composed of silver (Ag) particles + resin + solvent + additives, etc. After screen printing, it is cured by baking to remove most of the solvent, and finally micron or nanometer-level silver particles and part of the resin are left. However, it is relatively easy to have internal air voids or resin agglomeration and other abnormalities, which will affect the product performance. The top electrode 40 obtained by electroplating in the above-mentioned scheme is dense and has no stratification, no holes, no resin agglomeration and other abnormalities. Compared with the multi-layer screen printing scheme in the related art, it can significantly improve the performance of the top electrode 40, and then improve the performance of the prepared ultrasonic transducer 100.

[0128] Optionally, in the present application, the prepared top electrode 40 can reach the required target thickness through a single electroplating operation, thereby eliminating the need for multiple operation steps.

[0129] Optionally, a single electroplating operation in the present application may include multiple electroplating steps, for example, 2-step electroplating or 3-step electroplating may be used. It should be understood that the specific implementation method of step S108 is not limited in the present application. In some optional embodiments, the electroplating method of step S108 may include: energizing the seed metal layer 50 with a current not exceeding 50 amperes, performing N steps of electroplating on the seed metal layer 50 in at least the accommodation space, and the current density of the electroplating in the first step of the N steps is less than or equal to 2 amperes per square decimeter (A / dm 2 , referred to as ASD), the current density of the electroplating of the 2nd to Nth steps in the N steps on the seed metal layer 50 is less than 8 amperes per square decimeter, where N≥2 and is an integer.

[0130] Based on this, in the present application, electroplating is performed through the above-mentioned optional method, which can effectively electroplate the seed metal layer 50 in the accommodating space to obtain the top electrode 40, and ensure the quality stability and performance of the top electrode 40, thereby effectively improving the performance of the prepared ultrasonic transducer.

[0131] For example, taking two-step electroplating as an example, the seed metal layer 50 can be energized with a current exceeding 50A, and at least the seed metal layer 50 in the receiving space is electroplated in two steps, and the current density of the first step of electroplating for the seed metal layer 50 is less than or equal to 2ASD, and the current density of the second step of electroplating for the seed metal layer 50 is less than 8ASD. Other situations can be deduced by analogy.

[0132] It should be understood that the specific values ​​of the above current being less than 50A, the current density of the electroplating in the first step being less than or equal to 2ASD, and the current density of the electroplating in the second to N steps being less than 8ASD can be selected as needed and are not limited here.

[0133] Optionally, the current density of the electroplating in the first step to energize the seed metal layer 50 may be less than or equal to 1 ASD, thereby better ensuring the quality stability and performance of the top electrode 40, and further more effectively improving the performance of the prepared ultrasonic transducer.

[0134] In some optional embodiments, the metal material used for electroplating in the present application includes at least one metal material of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead, or the metal material used for electroplating includes an alloy material of at least two of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead. Through the at least one material mentioned above, the top electrode 40 can be effectively electroplated, and the performance of the top electrode 40 can be guaranteed, thereby ensuring the performance of the prepared ultrasonic transducer.

[0135] Optionally, the top electrode 40 is obtained by electroplating at least one of the metal materials of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead, and may be at least one of a pure tin layer, a pure copper layer, a pure nickel layer, a pure gold layer, a pure silver layer, a pure indium layer, a pure chromium layer, a pure zinc layer, a pure titanium layer, and a pure lead layer. When the top electrode 40 is obtained by electroplating at least two of the metal materials of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead, that is, at least two of the pure tin layer, the pure copper layer, the pure nickel layer, the pure gold layer, the pure silver layer, the pure indium layer, the pure chromium layer, the pure zinc layer, the pure titanium layer, and the pure lead layer, the top electrode 40 may be a metal stack. For example, in one example, the top electrode 40 may be a stack of pure copper and pure tin, for example, the copper layer may be electroplated first and then the tin layer may be electroplated to obtain the top electrode 40. Alternatively, the top electrode 40 may be an alloy layer of at least two of pure tin, pure copper, pure nickel, pure gold, pure silver, pure indium, pure chromium, pure zinc, pure titanium, and pure lead. For example, an example of the alloy layer is a pure tin-pure silver alloy layer.

[0136] It should be noted that, except for some of the above-mentioned preferred technical solutions of the present application, there are no cases in the related art that use tin to form the top electrode. The reason why tin is used as the electroplating material to electroplate the top electrode 40 in some preferred embodiments of the present application is that: on the one hand, for ultrasonic transducers, the top electrode 40 can usually reach the required target thickness through a single electroplating operation, reducing the process difficulty and time cycle, and reducing the probability of production abnormalities; on the other hand, the internal quality of the electroplated tin metal material is better than that of silk-screen silver (Ag) paste, which is different from the silver paste used for silk-screen printing. The silver paste is generally composed of silver (Ag) particles + resin + solvent + additives, etc. After silk-screen printing, it is cured by baking to remove most of the solvent, and finally only micrometer or nanometer-sized silver particles remain. and some resins, but it is relatively easy to have abnormalities such as internal air voids or resin agglomeration, which will affect the product performance. If tin is used for electroplating, a top electrode 40 made of tin can be obtained, which is dense inside without stratification, holes, resin agglomeration and other abnormalities, and has a small thickness tolerance and better quality stability. Therefore, the performance of the top electrode 40 can be improved, and then the performance of the prepared ultrasonic transducer 100 can be improved; on the other hand, compared with the use of silver paste to prepare the top electrode in the related technology, the use of tin for electroplating to prepare the top electrode 40 has cheaper materials and can significantly reduce the preparation cost of the ultrasonic transducer 100.

[0137] Of course, the thickness of the top electrode 40 can be selected as needed. Figure 2A , Figure 2B , Figure 2C As shown, the thickness H of the top electrode 40 may refer to the distance between the upper surface of the top electrode 40 and the contact surface between the top electrode 40 and the upper surface of the seed metal layer 50. Optionally, the thickness H of the top electrode 40 is less than or equal to 60 um. The top electrode 40 in this thickness range will not be too thick, and can effectively meet the performance requirements of the ultrasonic transducer 100.

[0138] Preferably, the thickness of the top electrode 40 may be in the range of 10um to 40um. The top electrode 40 in this preferred thickness range will not be too thick or too thin, and can more effectively meet the performance requirements of the ultrasonic transducer 100. For example, within the range of 10um to 40um, the thickness of the top electrode may be 10um, 15um, 20um, 25um, 30um, 35um, 40um, etc., or may be other values.

[0139] Preferably, the thickness of the top electrode 40 may be in the range of 15 um to 40 um. The top electrode 40 in this preferred thickness range will not be too thick or too thin, and can more effectively meet the performance requirements of the ultrasonic transducer 100 .

[0140] In some optional embodiments, the elastic modulus of the metal material used for electroplating in step S108 of the present application is less than 130 GPa. The top electrode 40 is obtained by electroplating the metal material with the elastic modulus range of less than 130 GPa, which can adapt to the stress matching between the stacked materials of the ultrasonic transducer and achieve a smaller warpage performance. For example, such a material can be tin, silver, tin-silver alloy, etc.

[0141] In some optional embodiments, the acoustic impedance of the metal material used for electroplating in step S108 of the present application is less than 35 MRayl (i.e., MPa·s / m3, megapascal·seconds per cubic meter). Since the metal material used for electroplating needs to consider the acoustic impedance matching of the ultrasonic transducer laminated structure, a large acoustic impedance mismatch will lead to serious acoustic energy reflection, thereby leading to inefficient transmission of ultrasonic waves. In layman's terms, when ultrasonic waves propagate in a laminated structure, if the acoustic impedance of the dielectric material is relatively different, the sound intensity of the ultrasonic wave will be significantly consumed during the propagation process. Therefore, by electroplating the metal material with an acoustic impedance range of less than 35 MRayl, the top electrode 40 can be obtained, which can minimize the acoustic impedance difference between the material of the substrate 10 (for example, including but not limited to silicon Si material, etc.), the material of the enclosure structure that needs to be retained (for example, including but not limited to organic glue material, etc.), and the material of the piezoelectric layer 30, thereby improving the performance of the top electrode 40 and improving the acoustic performance of the ultrasonic transducer 100 prepared.

[0142] For example, the top electrode 40 may be made of at least one of tin, copper, nickel, gold, silver, chromium, zinc, titanium, and lead mentioned above, or a metal material that can meet the elastic modulus and acoustic impedance range conditions in an alloy of at least two of the above. The top electrode 40 may be at least one of a tin layer, a copper layer, a nickel layer, a gold layer, a silver layer, an indium layer, a chromium layer, a zinc layer, a titanium layer, and a lead layer. When the top electrode 40 may be at least two of a tin layer, a copper layer, a nickel layer, a gold layer, a silver layer, an indium layer, a chromium layer, a zinc layer, a titanium layer, and a lead layer, the top electrode is a metal stack. For example, the top electrode may be a stack of copper metal and tin metal. Alternatively, the top electrode 40 may be an alloy layer of at least two of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead. For example, an example of an alloy layer is a tin-silver alloy layer. Optionally, when the top electrode 40 is an electroplated metal layer, it may be at least one of a pure tin layer, a pure copper layer, a pure nickel layer, a pure gold layer, a pure silver layer, a pure indium layer, a pure chromium layer, a pure zinc layer, a pure titanium layer, and a pure lead layer; or, it may be a metal stack of at least two of the above pure metal layers (pure tin layer, pure copper layer, pure nickel layer, pure gold layer, pure silver layer, pure indium layer, pure chromium layer, pure zinc layer, pure titanium layer, and pure lead layer). For example, a stack of pure copper and pure tin; or, the top electrode 40 is an alloy layer of at least two of pure tin, pure copper, pure nickel, pure gold, pure silver, pure indium, pure chromium, pure zinc, pure titanium, and pure lead. For example, an example of the alloy layer is a pure tin and pure silver alloy layer.

[0143] In some optional embodiments, the surface roughness of the top electrode 40 obtained by electroplating in step S108 of the present application can satisfy the average roughness Ra (Roughness Average) on the reference length is less than 0.8um, and the maximum roughness Rz on the reference length is less than 3um. Based on this, the top electrode 40 can effectively have a better appearance and a smaller thickness tolerance, a smoother surface, no obvious undulations, less granularity, and less obvious wrinkles or orange peel phenomenon, which is conducive to improving the performance of the prepared ultrasonic transducer 100.

[0144] In addition to the optional embodiments described above, "obtaining the top electrode 40" in the present application may include obtaining a top electrode 40 at least partially connected to the excitation electrode 60. In some other optional embodiments, "obtaining the top electrode 40" in the present application may also include: obtaining a top electrode 40 directly connected to an external circuit. In this way, the top electrode 40 may also directly obtain an excitation signal from the external circuit. A suitable method may be selected as needed, and is not limited here.

[0145] In some optional embodiments, before the above-mentioned step S104, the preparation method of the embodiment of the present application also includes: forming a pad area 90 for electrical connection to an external circuit on the upper surface of the substrate 10; on this basis, step S104 also includes: forming a whole layer of seed metal layer 50 on the upper surface of the substrate 10, so that the pad area 90 is covered by the seed metal layer 50; after obtaining the top electrode 40 in step S108, the preparation method of the embodiment of the present application also includes: through an etching process, at least partially removing the seed metal layer 50 covering the pad area 90 to expose at least part of the pad area 90.

[0146] Based on this, in the preparation method of the present application, the seed metal layer 50 covering the pad area 90 formed on the substrate 10 is at least partially removed through an etching process to expose at least a portion of the pad area 90, which can facilitate the connection of the pad area 90 with an external circuit, so that the prepared ultrasonic transducer 100 can be connected to the external circuit that needs to be used, thereby effectively exerting the function of the ultrasonic transducer 100.

[0147] In the ultrasonic transducer 100 prepared in the present application, the excitation electrode 60 is electrically connected to the pad area 90 and the top electrode 40, so as to obtain the excitation signal emitted by the external circuit through the pad area 90 and transmit it to the top electrode 40 to control the piezoelectric layer 30. Based on this, the excitation signal can be effectively transmitted to the top electrode 40 connected thereto through the excitation electrode 60, so that the ultrasonic transducer 100 can achieve the corresponding function.

[0148] Optionally, the external circuit may be a circuit in an electronic device to which the ultrasonic transducer 100 is applied. The pad area 90 may be electrically connected to the external circuit.

[0149] Optionally, the pad area 90 may include a plurality of pads. Optionally, among the plurality of pads, a portion of the pads may be electrically connected to the top electrode 40, and a portion of the pads may be electrically connected to the bottom electrode 20. Optionally, other pads in the pad area 90 may be used for the lead-out and access of other electrical signals. For example, a portion of the plurality of pads may be connected to the internal circuit of the ultrasonic transducer 100. Optionally, the excitation electrode 60 may be connected to a portion of the pads, and other pads in the pad area 90 may be used for the lead-out and access of other electrical signals. Optionally, the pad area 90 may be formed on the upper surface of the substrate 10 by methods including, but not limited to, electroplating, etching after depositing a metal layer, physical vapor deposition, chemical vapor deposition, screen printing, and the like.

[0150] For example, a portion of the pads of the pad region 90 may be electrically connected to the excitation electrode 60 , thereby achieving electrical connection between the pad region 90 and the top electrode 40 through the excitation electrode 60 .

[0151] For example Figure 2D As shown, it shows Figure 2A FIG. 1 is a schematic plan view of an ultrasonic transducer 100 as shown in FIG. 1 , which schematically shows a pad area 90 including a plurality of pads 91 (it should be understood that Figure 2D Omitted Figure 2A The protective layer 70 in FIG. 1 is shown in FIG. 1 . Figure 2E As shown, it is shown Figure 2B FIG. 1 is a schematic plan view of an ultrasonic transducer 100 as shown in FIG. 1 , which schematically shows a pad area 90 including a plurality of pads 91 (it should be understood that Figure 2E Omitted Figure 2B It should be understood that the above schematic diagrams are not intended to limit the embodiments of the present application.

[0152] Optionally, the above-mentioned "at least partially removing the seed metal layer 50 covering the pad area 90 formed on the substrate 10 through an etching process" can be achieved by using a wet etching process, and the seed metal layer in the non-electroplated metal area can be dissolved and removed by using a specific solvent reaction. At the same time, the seed metal layer 50 covering the pad area 90 can be removed, while the seed metal layer 50 under the top electrode 40 that has been electroplated will not be dissolved by the wet etching solvent.

[0153] In the present application, the etching solvent for etching the seed metal layer 50 can be a solvent that the piezoelectric layer 30 can tolerate, and cannot dissolve the piezoelectric layer material while removing the seed metal layer 50. For example, an acidic or alkaline solution with oxidizing ability can be used, or other solvents that can meet the needs can be used.

[0154] In some optional embodiments, the preparation method of the embodiment of the present application further includes: after obtaining the top electrode 40 , at least partially removing the first enclosure structure 81 .

[0155] As mentioned above, the first enclosure structure 81 can be a temporary structure in the preparation process. After obtaining the top electrode 40, the first enclosure structure 81 can be at least partially removed, which can reduce the volume and weight of the ultrasonic transducer 100. Moreover, since the first enclosure structure 81 is used as a temporary structure in this optional embodiment, there is no need to consider too much about the limitation that the acoustic impedance of the material of the first enclosure structure 81 must match the acoustic impedance of the overall laminated structure of the ultrasonic transducer 100. Therefore, the material compatibility can be expanded and the range of material selection that can be used as the first enclosure structure 81 is expanded.

[0156] For example Figure 2A , Figure 2B , Figure 2C The structures of the ultrasonic transducers 100 obtained as shown do not have the first enclosure structure 81 , that is, the first enclosure structure 81 is removed from these optional ultrasonic transducers 100 before they are manufactured.

[0157] Optionally, the first enclosure structure 81 may be removed by any feasible method. For example, taking the first enclosure structure 81 as formed by patterning and curing the first photoresist as an example, a stripping process may be used. For example, a specific solvent may be used to dissolve the first enclosure structure 81 to remove the first enclosure structure 81, while other structures will not be dissolved by the specific solvent.

[0158] In some optional embodiments, the preparation method of the embodiment of the present application further includes: preparing a protective layer 70 covering at least a portion of the top electrode 40. Based on this, by preparing the protective layer 70 covering at least a portion of the top electrode 40, at least the top electrode 40 can be protected to at least ensure the performance of the top electrode 40, thereby improving the performance of the prepared ultrasonic transducer 100.

[0159] Optionally, the protective layer 70 can protect the various layers of the covered ultrasonic transducer 100, and can be an insulating layer that not only provides electrical insulation but also isolates the influence of external water, oxygen and other adverse environmental factors, thereby ensuring that the ultrasonic transducer 100 can work normally and effectively for a long time.

[0160] Optionally, “preparing a protective layer 70 covering at least a portion of the top electrode 40 ” in the present application may include: preparing a protective layer 70 covering at least a portion of the upper surface of the top electrode 40 .

[0161] Optionally, the term “preparing a protective layer 70 covering at least a portion of the top electrode 40” in the present application may include: preparing a protective layer 70 that completely covers the top electrode 40. For example, see Figure 2A , Figure 2B , Figure 2C The ultrasonic transducer 100 prepared as shown is understood. Obviously, in this way, more comprehensive protection can be achieved for the top electrode 40, the performance of the top electrode 40 can be better guaranteed, and the ultrasonic transducer 100 can be effectively and normally operated for a long time.

[0162] Optionally, “preparing a protective layer 70 covering at least a portion of the top electrode 40” in the present application may include: preparing a protective layer 70 that completely covers the top electrode 40 and the piezoelectric layer 30. For example, see Figure 2A and Figure 2B As shown, for example, refer to Figure 2A and Figure 2B Obviously, the protective layer 70 prepared in this way can provide more comprehensive protection for the top electrode 40 and the piezoelectric layer 30, better ensure the performance of the top electrode 40 and the piezoelectric layer 30, and ensure that the ultrasonic transducer 100 can work normally and effectively for a long time.

[0163] Optionally, the protective layer 70 may be prepared in any feasible manner, which is not limited herein. For example, it may be prepared by screen printing or exposure and development. Alternatively, it may be prepared by coating or dry film lamination. Optionally, when preparing the protective layer 70, avoid the protective layer 70 covering the pad area 90 to ensure that the pad area 90 can be exposed for subsequent electrical connection with an external circuit.

[0164] Optionally, through the preparation scheme of the present application, in the wafer-level preparation process of the ultrasonic transducer, effective electroplating can still be carried out when the electroplating area of ​​the wafer reaches 60% to 80%, while also ensuring that the warping of the wafer is appropriate and that the warping value of a single ultrasonic transducer chip after grinding and cutting does not exceed 30um.

[0165] It should be understood that the above description is merely some optional embodiments of the preparation scheme of the embodiments of the present application, and is not any limitation to the embodiments of the present application.

[0166] In order to facilitate a further understanding of the preparation scheme of the ultrasonic transducer of the application embodiment, Figure 4A , Figure 4B , Figure 4C The overall process of three optional preparation schemes is described.

[0167] <Optional Preparation Scheme 1>

[0168] Reference Figure 4AThe process schematic diagram of the preparation scheme of the ultrasonic transducer is shown, and the process can be used to prepare Figure 2A The ultrasonic transducer 100 shown in the figure, the preparation scheme includes the following steps:

[0169] Step 1: forming a bottom electrode 20 on the upper surface of the substrate 10, and forming a piezoelectric layer 30 covering the bottom electrode 20 on the substrate 10, and further preparing an excitation electrode 60 and a pad area 90 on the substrate 10;

[0170] Step 2: forming a whole layer of seed metal layer 50 on the upper surface of the substrate 10 by low-temperature sputtering, the seed metal layer 50 covers the upper surface and the outer side wall of the piezoelectric layer 30, and covers the excitation electrode 60 and the pad area 90, and the temperature of the low-temperature sputtering is controlled to be below 135° C.;

[0171] Step 3: a whole layer of first photoresist is disposed on the substrate 10 (for example, by spin coating), and the first photoresist is patterned and cured to form a first enclosure structure 81 above the piezoelectric layer 30 to enclose a space for preparing the top electrode 40. The curing temperature of the first photoresist is controlled to be below 135° C., and the inner side wall of the first enclosure structure 81 is made perpendicular to the substrate 10 as much as possible (that is, the angle between the inner side wall of the first enclosure structure 81 and the normal line of the substrate 10 is made as close to 0° as possible);

[0172] Step 4: energize the seed metal layer 50, and electroplate the seed metal layer 50 in the accommodation space (i.e., the area not covered by the first enclosure structure 81) to obtain the top electrode 40, and make the outer wall of the top electrode 40 perpendicular to the substrate 10 as much as possible (i.e., make the angle between the outer wall of the top electrode 40 and the normal line of the substrate 10 as close to 0° as possible);

[0173] Step 5: removing the first enclosure structure 81 formed by the first photoresist through a stripping process;

[0174] Step 6: removing the seed metal layer 50 in the non-electroplated metal area by an etching process, wherein at least the seed metal layer 50 covering the pad area 90 is removed to expose the pad area 90;

[0175] Step 7: Prepare a protective layer covering the top electrode 40 and the piezoelectric layer 30 to protect the top electrode 40 and the piezoelectric layer 30 to obtain the ultrasonic transducer 100 .

[0176] It should be understood that Figure 2A , Figure 4A The examples shown are not intended to limit the embodiments of the present application.

[0177] <Optional Preparation Scheme 2>

[0178] Reference Figure 4BThe process schematic diagram of the preparation scheme of the ultrasonic transducer is shown, and the process can be used to prepare Figure 2B The ultrasonic transducer 100 shown in the figure, the preparation scheme includes the following steps:

[0179] Step 1: forming a bottom electrode 20 on the upper surface of the substrate 10, and preparing an excitation electrode 60 and a pad area 90 on the substrate 10. In addition, a whole layer of second photoresist is disposed on the upper surface of the substrate 10 (for example, by spin coating), and the second photoresist is patterned and cured to form a second enclosure structure 82 in the peripheral area of ​​the bottom electrode 20 on the upper surface of the substrate 10, and the second enclosure structure 82 exposes the bottom electrode;

[0180] Step 2: preparing a piezoelectric layer 30 covering the bottom electrode 20 above the bottom electrode 20 exposed from the second enclosure structure 82, and the piezoelectric layer 30 at least partially covers the upper surface of the second enclosure structure 82;

[0181] Step 3: forming a whole layer of seed metal layer 50 on the upper surface of the substrate 10 by low-temperature sputtering, the seed metal layer 50 covers the upper surface and the outer side wall of the piezoelectric layer 30, and covers the excitation electrode 60 and the pad area 90, and the temperature of the low-temperature sputtering is controlled to be below 135° C.;

[0182] Step 4: a first photoresist layer is disposed on the substrate 10 (for example, by spin coating), and the first photoresist is patterned and cured to form a first enclosure structure 81 above the piezoelectric layer 30 to enclose a space for preparing the top electrode 40. The curing temperature of the first photoresist is controlled to be below 135° C., and the inner side wall of the first enclosure structure 81 is made perpendicular to the substrate 10 as much as possible (that is, the angle between the inner side wall of the first enclosure structure 81 and the normal line of the substrate 10 is made as close to 0° as possible);

[0183] Step 5: energize the seed metal layer 50, and electroplate the seed metal layer 50 in the accommodation space (i.e., the area not covered by the first enclosure structure 81) to obtain the top electrode 40, wherein the top electrode 40 is at least partially located on the upper surface of the second enclosure structure 82, and the outer sidewall of the top electrode 40 is as perpendicular to the substrate 10 as possible (i.e., the angle between the outer sidewall of the top electrode 40 and the normal line of the substrate 10 is as close to 0° as possible);

[0184] Step 6: removing the first enclosure structure 81 formed by the first photoresist through a stripping process;

[0185] Step 7: removing the seed metal layer 50 in the non-electroplated metal area by an etching process, wherein at least the seed metal layer 50 covering the pad area 90 is removed to expose the pad area 90;

[0186] Step 8: Prepare a protective layer covering the top electrode 40 and the piezoelectric layer 30 to protect the top electrode 40 and the piezoelectric layer 30 to obtain the ultrasonic transducer 100 .

[0187] It should be understood that Figure 2B , Figure 4B The examples shown are not intended to limit the embodiments of the present application.

[0188] <Optional Preparation Scheme 3>

[0189] Reference Figure 4C The process schematic diagram of the preparation scheme of the ultrasonic transducer is shown, and the process can be used to prepare Figure 2C The ultrasonic transducer 100 shown in the figure, the preparation scheme includes the following steps:

[0190] Step 1: forming a bottom electrode 20 on the upper surface of the substrate 10, and forming a piezoelectric layer 30 covering the bottom electrode 20 on the substrate 10, and further preparing an excitation electrode 60 and a pad area 90 on the substrate 10;

[0191] Step 2: a whole layer of second photoresist is disposed on the upper surface of the substrate 10 (for example, by spin coating), and the second photoresist is patterned and cured to form a second enclosure structure 82 in the peripheral area of ​​the piezoelectric layer 30 on the upper surface of the substrate 10, and the second enclosure structure 82 exposes at least part of the upper surface of the piezoelectric layer 30;

[0192] Step 3: forming a whole layer of seed metal layer 50 on the upper surface of substrate 10 by low temperature sputtering, the seed metal layer 50 covers the upper surface of piezoelectric layer 30, and covers excitation electrode 60 and pad area 90, and the temperature of low temperature sputtering is controlled below 135°C;

[0193] Step 4: a first photoresist layer is disposed on the substrate 10 (for example, by spin coating), and the first photoresist is patterned and cured to form a first enclosure structure 81 above the piezoelectric layer 30 to enclose a space for preparing the top electrode 40. The curing temperature of the first photoresist is controlled to be below 135° C., and the inner side wall of the first enclosure structure 81 is made perpendicular to the substrate 10 as much as possible (that is, the angle between the inner side wall of the first enclosure structure 81 and the normal line of the substrate 10 is made as close to 0° as possible);

[0194] Step 5: energize the seed metal layer 50, and electroplate the seed metal layer 50 in the accommodation space (i.e., the area not covered by the first enclosure structure 81) to obtain the top electrode 40, wherein the top electrode 40 is at least partially located on the upper surface of the second enclosure structure 82, and the outer sidewall of the top electrode 40 is as perpendicular to the substrate 10 as possible (i.e., the angle between the outer sidewall of the top electrode 40 and the normal line of the substrate 10 is as close to 0° as possible);

[0195] Step 6: removing the first enclosure structure 81 formed by the first photoresist through a stripping process;

[0196] Step 7: removing the seed metal layer 50 in the non-electroplated metal area by an etching process, wherein at least the seed metal layer 50 covering the pad area 90 is removed to expose the pad area 90;

[0197] Step 8: Prepare a protective layer covering the top electrode 40 and the piezoelectric layer 30 to protect the top electrode 40 and the piezoelectric layer 30 to obtain the ultrasonic transducer 100 .

[0198] It should be understood that Figure 2C , Figure 4C The examples shown are not intended to limit the embodiments of the present application.

[0199] It should be understood that the above optional preparation scheme 1, optional preparation scheme 2, and optional preparation scheme 3 are merely several optional examples of the embodiments of the present application, and they do not serve as any limitation to the embodiments of the present application. In addition, their introduction is relatively concise and can also be understood in conjunction with the relevant descriptions of the previous embodiments.

[0200] According to a second aspect of the embodiment of the present application, an ultrasonic transducer 100 is provided, which is prepared by any one of the preparation schemes of the ultrasonic transducer provided in the first aspect. Figure 2A , Figure 2B , Figure 2C As shown, the ultrasonic transducer 100 comprises at least: a substrate 10, a bottom electrode 20, a piezoelectric layer 30 and a top electrode 40; the bottom electrode 20 is located on the upper surface of the substrate 10, the piezoelectric layer 30 is located above the substrate 10 and covers the bottom electrode 20, and at least a portion of the top electrode 40 is located above the piezoelectric layer 30; the top electrode 40 is used to be applied with an excitation signal to excite the piezoelectric layer 30 to emit an ultrasonic signal, and the bottom electrode 20 is used to receive an ultrasonic detection signal generated between the top electrode 40 and the bottom electrode 20 when the returned ultrasonic signal acts on the piezoelectric layer 30.

[0201] Since the ultrasonic transducer 100 of the second aspect is prepared by the preparation method of the first aspect, it can have better performance.

[0202] According to the third aspect of the embodiment of the present application, referring to Figure 5 As shown, an ultrasonic fingerprint module 200 is provided, comprising: an ultrasonic transducer 100 as provided in the second aspect.

[0203] Since the ultrasonic fingerprint module 200 of the third aspect includes the ultrasonic transducer 100 of the second aspect, it has better performance and can better realize the ultrasonic fingerprint function.

[0204] According to the third aspect of the embodiment of the present application, referring to Fig. 6A , Figure 6B As shown, an electronic device 300 is provided, comprising: the ultrasonic transducer 100 provided in the second aspect, or the ultrasonic fingerprint module 200 provided in the third aspect.

[0205] Optionally, the electronic device 300 may be any electronic device, including but not limited to a mobile phone, a computer, etc. It should be understood that the present application does not limit the configuration of the ultrasonic transducer 100 or the ultrasonic fingerprint module 200 in the electronic device 300 .

[0206] As an example, taking the electronic device 300 as a mobile phone and including the ultrasonic transducer 100 as an example, refer to Figure 7 As shown, the ultrasonic transducer 100 can be bonded to the bottom of the screen 320 of the electronic device 300 through the adhesive layer 310 for under-screen ultrasonic biometric detection. It should be understood that Figure 7 In Figure 2B The optional ultrasonic transducer 100 is provided as an example for ease of understanding and is not intended to be a limitation to the present application. The same may be said for any other optional ultrasonic transducer of the embodiment and no additional examples will be given here for elaboration.

[0207] As another example, taking the electronic device 300 as a mobile phone and including the ultrasonic fingerprint module 200, the ultrasonic fingerprint module 200 can be bonded to the bottom of the mobile phone screen of the electronic device 300 through an adhesive layer to achieve under-screen ultrasonic fingerprint recognition.

[0208] It should be understood that the above is only an example application and does not constitute any limitation to the embodiments of the present application.

[0209] It can be understood that the above description of various aspects of the embodiments of the present application is merely some optional exemplary descriptions of the technical solutions of the embodiments of the present application, and does not constitute any limitation on the embodiments of the present application.

[0210] The optional implementation modes of the embodiments of the present application are described in detail above in conjunction with the accompanying drawings, but the embodiments of the present application are not limited thereto. It should be noted that, for the convenience of explaining the embodiments of the present application, the various drawings of the embodiments of the present application are not necessarily drawn according to the actual proportions, which are only used to facilitate the explanation of the technical solution and are not used for any restriction on the embodiments of the present application. Within the technical concept of the embodiments of the present application, the technical solutions of the embodiments of the present application can be subjected to a variety of simple modifications. The various technical features included in the various different embodiments of the embodiments of the present application can be combined in any suitable manner. In order to avoid unnecessary repetition, the embodiments of the present application will not be described separately for various possible combinations. However, these simple modifications and combinations should also be regarded as the contents disclosed in the embodiments of the present application, and all belong to the protection scope of the embodiments of the present application.

[0211] The term "including" and its variations used in this document are open inclusions, that is, "including but not limited to". The term "based on" means "based at least in part on". The term "one embodiment" means "at least one embodiment"; the term "another embodiment" means "at least one other embodiment"; the term "some embodiments" means "at least some embodiments". It should be noted that the concepts of "first", "second", etc. mentioned in this application are only used to distinguish different devices, modules or units, and are not used to limit the order or interdependence of the functions performed by these devices, modules or units. It should be noted that the modifications of "one" and "multiple" mentioned in this application are illustrative rather than restrictive. Those skilled in the art should understand that unless otherwise clearly indicated in the context, it should be understood as "one or more".

[0212] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing an ultrasonic transducer, comprising: forming a bottom electrode on the upper surface of the substrate, and forming a piezoelectric layer covering the bottom electrode above the substrate; forming a seed metal layer at least on the upper surface of the piezoelectric layer; forming a first enclosure structure above the substrate, and forming a receiving space for preparing a top electrode above the piezoelectric layer through the first enclosure structure; The seed metal layer is energized, and the seed metal layer at least in the receiving space is electroplated to obtain a top electrode, so as to obtain the ultrasonic transducer.

2. The method according to claim 1, wherein: The angle between at least one inner side wall of the first enclosure structure and the normal to the substrate is less than or equal to 45°, the angle between at least one outer side wall of the top electrode and the normal to the substrate is less than or equal to 45°, and the thickness of the first enclosure structure is not less than the thickness of the top electrode.

3. The method according to claim 2, wherein: The angle between at least one inner side wall of the first enclosure structure and the normal line of the substrate is less than or equal to 5°, and the angle between at least one outer side wall of the top electrode and the normal line of the substrate is less than or equal to 5°.

4. The method according to claim 1, wherein: The step of forming a seed metal layer at least on the upper surface of the piezoelectric layer comprises: The upper surface and the outer side wall of the piezoelectric layer are covered by the seed metal layer by a low-temperature sputtering method, wherein the temperature of the low-temperature sputtering is controlled below 135°C.

5. The method according to claim 4, wherein: Before forming the seed metal layer at least on the upper surface of the piezoelectric layer, the method further comprises: forming a pad area on the upper surface of the substrate for electrical connection with an external circuit; The step of forming a seed metal layer at least on the upper surface of the piezoelectric layer further comprises: forming a whole layer of the seed metal layer on the upper surface of the substrate so that the pad area is covered by the seed metal layer; After obtaining the top electrode, the method further includes: at least partially removing the seed metal layer covering the pad area through an etching process to expose at least a portion of the pad area.

6. The method according to claim 1, wherein: The method further includes: after obtaining the top electrode, at least partially removing the first enclosure structure.

7. The method according to any one of claims 1 to 6, wherein: The step of forming a first enclosure structure above the substrate comprises: Disposing a first photoresist on the substrate, and patterning and curing the first photoresist to form the first enclosure structure, wherein the curing temperature of the first photoresist during curing is controlled to be below 135° C.; The patterning and curing of the first photoresist includes: patterning the first photoresist to enclose a receiving space for preparing a top electrode above the piezoelectric layer, and then curing the first photoresist.

8. The method according to any one of claims 1 to 6, wherein: Before forming the piezoelectric layer, the method further includes: forming a second enclosure structure in a peripheral area of ​​the bottom electrode on the upper surface of the substrate, and making the second enclosure structure expose the bottom electrode; The forming of a piezoelectric layer covering the bottom electrode above the substrate includes: preparing the piezoelectric layer above the bottom electrode exposed by the second enclosure structure.

9. The method according to claim 8, wherein: The prepared piezoelectric layer at least partially covers the upper surface of the second enclosure structure.

10. The method according to claim 8, wherein: The second enclosure structure is formed in the peripheral area of ​​the bottom electrode on the upper surface of the substrate, comprising: Disposing a second photoresist on the upper surface of the substrate, and patterning and curing the second photoresist to form the second enclosure structure in the peripheral area of ​​the bottom electrode on the upper surface of the substrate; The patterning and curing of the second photoresist includes: patterning the second photoresist to expose the bottom electrode, and then curing.

11. The method according to claim 8, wherein: The step of forming a first enclosure structure above the substrate comprises: A portion of the first enclosure structure is formed on an upper surface of a second enclosure structure above the substrate, and a gap exists between the first enclosure structure formed on the upper surface of the second enclosure structure and the piezoelectric layer.

12. The method according to any one of claims 1 to 6, wherein: After forming the piezoelectric layer covering the bottom electrode above the substrate, the method further comprises: forming a second enclosure structure in a peripheral area of ​​the piezoelectric layer on the upper surface of the substrate, and making the second enclosure structure expose at least a portion of the upper surface of the piezoelectric layer; The forming of a first enclosure structure above the substrate comprises: forming a portion of the first enclosure structure on an upper surface of a second enclosure structure above the substrate.

13. The method according to claim 12, wherein: The second enclosure structure is formed in the peripheral area of ​​the piezoelectric layer on the upper surface of the substrate, comprising: Disposing a second photoresist on the upper surface of the substrate, and patterning and curing the second photoresist to form the second enclosure structure in the peripheral area of ​​the piezoelectric layer on the upper surface of the substrate, wherein the curing temperature of the second photoresist during curing is controlled to be below 135° C.; The patterning and curing of the second photoresist comprises: patterning the second photoresist to expose at least a portion of the upper surface of the piezoelectric layer, and then curing.

14. The method according to claim 12, wherein: The first enclosure structure and / or the second enclosure structure is made of at least one of the following materials: polyimide, poly(p-phenylene benzobisoxazole), epoxy resin, acrylic resin, and organic siloxane composite material.

15. The method according to any one of claims 1 to 6, wherein: The method further comprises: preparing a protection layer covering at least a portion of the top electrode.

16. The method according to any one of claims 1 to 6, wherein: The metal material used for electroplating includes at least one metal material selected from the group consisting of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead; or, the metal material used for electroplating includes an alloy material of at least two of the group consisting of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead.

17. The method according to any one of claims 1 to 6, wherein: The method further comprises: forming an excitation electrode on the upper surface of the substrate that is not in contact with the bottom electrode; The forming of a first enclosure structure above the substrate comprises: forming a first enclosure structure above the substrate in contact with the excitation electrode; The obtaining of the top electrode includes: obtaining a top electrode at least partially connected to the excitation electrode, or obtaining a top electrode directly connected to an external circuit.

18. The method according to any one of claims 1 to 6, wherein: The step of electrifying the seed metal layer and electroplating the seed metal layer at least in the receiving space comprises: The seed metal layer is energized with a current not exceeding 50 amperes, and the seed metal layer at least in the receiving space is electroplated for N steps, and the current density of the electroplating of the seed metal layer in the first step of the N steps is less than or equal to 2 amperes per square decimeter, and the current density of the electroplating of the seed metal layer in the second to N steps of the N steps is less than 8 amperes per square decimeter, wherein N ≥ 2 and is an integer.

19. An ultrasonic transducer, prepared by the method for preparing an ultrasonic transducer according to any one of claims 1 to 18, the ultrasonic transducer comprising: substrate, bottom electrode, piezoelectric layer and top electrode; The bottom electrode is located on the upper surface of the substrate, the piezoelectric layer is located above the substrate and covers the bottom electrode, and at least a portion of the top electrode is located above the piezoelectric layer; The top electrode is used to be applied with an excitation signal to excite the piezoelectric layer to emit an ultrasonic signal, and the bottom electrode is used to receive an ultrasonic detection signal generated between the top electrode and the bottom electrode when the returned ultrasonic signal acts on the piezoelectric layer.

20. An ultrasonic fingerprint module, comprising: The ultrasonic transducer as claimed in claim 19.

21. An electronic device, comprising: The ultrasonic transducer as claimed in claim 19, or the ultrasonic fingerprint module as claimed in claim 20.

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