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 ultrasonic transducer comprises a substrate, a bottom electrode, a piezoelectric layer, a top electrode and an excitation 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 part of the top electrode is located above the piezoelectric layer; the excitation electrode is located on the upper surface of the substrate, a distance exists between the excitation electrode and the bottom electrode, the piezoelectric layer is provided with an opening part, and the top electrode is electrically connected with the excitation electrode through the opening part; the excitation electrode is used for receiving an excitation signal and applying the excitation signal to the top electrode, so that an electric field is formed between the top electrode and the bottom electrode to excite the piezoelectric layer to emit an ultrasonic signal, and the bottom electrode is used for receiving an ultrasonic detection signal generated between the top electrode and the bottom electrode when the returned ultrasonic signal acts on the piezoelectric layer. The performance of the ultrasonic transducer in the scheme is good.

Description

TECHNICAL FIELD

[0001] Embodiments of the present application relate to the technical field of ultrasonic transducers, and particularly relate to an ultrasonic transducer, a preparation method thereof, an ultrasonic fingerprint module, and an electronic device. BACKGROUND

[0002] The ultrasonic transducer utilizes the mechanical-electric conversion characteristics of piezoelectric material, and can emit ultrasonic signals to the outside by the voltage output by the driving circuit, and convert the ultrasonic signals reflected from the outside into electric signals, so as to obtain the information of the sensing surface of the outside, and can be widely applied to the field of biological feature recognition (for example, one example of the application can be an ultrasonic fingerprint module, which can collect fingerprint images to realize fingerprint recognition). The ultrasonic transducer in the related art has the problem of poor performance, and therefore, it is necessary to provide some new technical solutions of the ultrasonic transducer to improve the performance of the ultrasonic transducer. SUMMARY

[0003] Embodiments of the present application provide an ultrasonic transducer, a preparation method thereof, an ultrasonic fingerprint module, and an electronic device.

[0004] According to a first aspect of embodiments of the present application, an ultrasonic transducer is provided, comprising: a substrate, a bottom electrode, a piezoelectric layer, a top electrode, and an excitation 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 part of the top electrode is located above the piezoelectric layer; the excitation electrode is located on the upper surface of the substrate and has a spacing with the bottom electrode, the piezoelectric layer is provided with an opening part, and the top electrode forms an electrical connection with the excitation electrode through the opening part; the excitation electrode is used to receive an excitation signal and apply the excitation signal to the top electrode, so as to form an electric field between the top electrode and the bottom electrode, 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.

[0005] According to a second aspect of embodiments of the present application, a preparation method of an ultrasonic transducer is provided, comprising: forming a bottom electrode and an excitation electrode on the upper surface of a substrate, wherein the excitation electrode has a spacing with the bottom electrode; forming a piezoelectric layer above the substrate, which covers the bottom electrode and at least partially covers the excitation electrode, and forming an opening part in the piezoelectric layer, so as to expose at least part of the excitation electrode through the opening part; forming a top electrode above the piezoelectric layer, and making the top electrode form an electrical connection with the excitation electrode through the opening part, to prepare the ultrasonic transducer.

[0006] 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 first aspect.

[0007] According to a fourth aspect of the embodiments of the present application, an electronic device is provided, comprising the ultrasonic fingerprint module provided in the third aspect, a screen, a back plate and a side frame, the ultrasonic fingerprint module is attached to the lower surface of the screen or the inner side of the back plate or the inner side of the side frame.

[0008] Based on this, the ultrasonic transducer in the present application, on the one hand, through the design of the opening part of the piezoelectric layer, the top electrode can form an electrical connection with the excitation electrode through the opening part of the piezoelectric layer, so that the top electrode can be excited by the excitation electrode to apply an excitation signal, so that an electric field can be formed between the top electrode 40 and the bottom electrode 20 to effectively excite the piezoelectric layer to emit an ultrasonic signal, and the bottom electrode can also effectively receive the returned ultrasonic signal to generate an ultrasonic detection signal between the top electrode and the bottom electrode when the piezoelectric layer is acted upon, so as to effectively realize the function of the ultrasonic transducer; on the other hand, since the top electrode forms an electrical connection with the excitation electrode through the opening part, the top electrode can not be connected with the excitation electrode through the "top electrode tail" in the related art, so that when designing the piezoelectric layer and the excitation electrode, it is no longer necessary to limit "the excitation electrode must be partially exposed" and "the excitation electrode cannot be completely covered by the piezoelectric layer", and then in the technical solution of the present application, the piezoelectric layer can exceed the position of the excitation electrode, thus canceling the many limitations in the related art, so that the ultrasonic transducer can have more possible flexible preparation modes, and since the limitations in the related art are canceled, the piezoelectric layer of the ultrasonic transducer can be further expanded (for example, it can be expanded to exceed the excitation electrode), and the top electrode can also be expanded with the piezoelectric layer, so that the ultrasonic reflection interface of the piezoelectric layer and the top electrode can be further away from the AA area boundary, so as to reduce noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer and improve the response consistency of the ultrasonic transducer, and the image flatness of the image obtained by the ultrasonic transducer is also high, thereby effectively improving the performance of the ultrasonic transducer. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments described in the embodiments of the present application, and other drawings can also be obtained by those skilled in the art based on these drawings.

[0010] Figure 1AA schematic diagram of an ultrasonic transducer in the related art is shown.

[0011] Figure 1B A schematic diagram of an ultrasonic transducer in the related art is shown. Figure 1A A plan view of the ultrasonic transducer in the related art is shown.

[0012] Figure 2A A schematic diagram of an example ultrasonic transducer in the present application is shown.

[0013] Figure 2B A schematic diagram of an example ultrasonic transducer in the present application is shown. Figure 2A A plan view of the example ultrasonic transducer in the present application is shown.

[0014] Figure 3A A schematic diagram of another example ultrasonic transducer in the present application is shown.

[0015] Figure 3B A schematic diagram of another example ultrasonic transducer in the present application is shown. Figure 3A A plan view of the example ultrasonic transducer in the present application is shown.

[0016] Figure 3C A schematic diagram of yet another example ultrasonic transducer in the present application is shown.

[0017] Figure 3D A schematic diagram of yet another example ultrasonic transducer in the present application is shown. Figure 3C A plan view of the example ultrasonic transducer in the present application is shown.

[0018] Figure 4 A flow chart of a method of manufacturing an example ultrasonic transducer in the present application is shown.

[0019] Figure 5 A flow chart of an optional way of forming a top electrode in the present application is shown.

[0020] Figure 6A A schematic diagram of a manufacturing process of an example ultrasonic transducer in the present application is shown. Figure 2A

[0021] A schematic diagram of a manufacturing process of an example ultrasonic transducer in the present application is shown. Figure 6B Figure 3A A schematic block diagram of an example ultrasonic fingerprint module in the present application is shown.

[0022] Figure 7 A schematic block diagram of an example electronic device in the present application is shown.

[0023] Figure 8A A schematic block diagram of an example electronic device in the present application is shown.

[0024] Figure 8B ​A schematic block diagram of another example electronic device in the present application is shown.

[0025] Figure 9 A schematic diagram showing an ultrasonic transducer adhered under a screen of an electronic device in one example of the present application is shown.

[0026] Legend of reference signs: 100, ultrasonic transducer; 10, substrate; 20, bottom electrode; 30, piezoelectric layer; 31, opening portion; 311, opening; 40, top electrode; 50, seed metal layer; 60, excitation electrode; 70, protective layer; 80, containment structure; 81, accommodation space; 90, pad region; 91, pad; 200, ultrasonic fingerprint module; 300, electronic device; 310, adhesive layer; 320, screen. DETAILED DESCRIPTION

[0027] In order for 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 described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present application should belong to the scope of protection of the present application.

[0028] The ultrasonic transducer is applied to an ultrasonic fingerprint module and is arranged in a specific area of a screen of an electronic device including but not limited to a smart phone, which can be used for fingerprint identification, can obtain peak and valley distribution information of a fingerprint, and can obtain a fingerprint image through signal processing based on the difference in reflected ultrasonic signal strength corresponding to the peaks and valleys, so as to realize user identity authentication. The fingerprint identification system based on the ultrasonic transducer sensing technology has the advantages that it is relatively insensitive to the interference of wet, dry or dirty fingers, and can pass through thick glass screens and other materials such as screen protection films. Therefore, the ultrasonic transducer provides more design freedom for electronic devices and can enhance the anti-interference and security of products. In some example ultrasonic transducer structures, there is a circuit structure for transmitting ultrasonic excitation signals and processing ultrasonic echo signals, and a piezoelectric material layer with a high piezoelectric coefficient, i.e., generally composed of a bottom electrode, a piezoelectric layer and a top electrode. The ultrasonic transducer in the related art has problems such as poor performance, and therefore it is necessary to provide some new technical solutions to improve the performance of the ultrasonic transducer.

[0029] For example, Figure 1A A schematic diagram showing some types of ultrasonic transducers in the related art is shown. Figure 1B A schematic diagram showing Figure 1A A planar schematic diagram showing a top view of the ultrasonic transducer 100' in the related art in the present application. As shown in Figure 1A and Figure 1B As shown in FIG. 1, the ultrasonic transducer 100 includes a substrate 10, a bottom electrode 20, a piezoelectric layer 30, a top electrode 40, an excitation electrode 60, and a pad area 90. As shown in FIG. 2, the piezoelectric layer 30 covers the bottom electrode 20 and the top electrode 40, and the excitation electrode 60 is partially exposed by the piezoelectric layer 30. Figure 1A and Figure 1B As shown in FIG. 3, the piezoelectric layer 30' avoids the area where the pad area 90' is located, and part of the edge of the piezoelectric layer 30' is designed not to exceed the excitation electrode 60', so that the excitation electrode 60' can be partially or completely exposed by the piezoelectric layer 30'. The top electrode 40' of the ultrasonic transducer 100' can include a top electrode body 41' and a top electrode tail 42' (as exemplarily shown in FIG. 4, the boundary between the two is shown by a dashed line), and the top electrode tail 42' exceeds the edge of the piezoelectric layer 30' and is electrically connected with the excitation electrode 60'. Figure 1A and Figure 1B As can be seen from FIG. 5 and FIG. 6, part of the top electrode tail 42' exceeding the piezoelectric layer 30' is connected with the excitation electrode 60' in a convex shape compared with the top electrode body 41'. Such a convex shape at least brings the following defects: in the related art, the design of the top electrode tail 42' limits the excitation electrode 60' to be partially exposed and cannot be completely covered by the piezoelectric layer 30', so that part of the piezoelectric layer 30' cannot exceed the position where the excitation electrode 60' is located, which directly limits the expansion distance of the piezoelectric layer 30' of the ultrasonic transducer 100' relative to the active area (Active Area, i.e., AA area) of the ultrasonic transducer 100', so that the ultrasonic reflection interface cannot be as far away from the AA area boundary as possible, and relatively stronger noise and interference are generated, which directly affects the performance of the ultrasonic transducer 100' (such as easily reducing the signal-to-noise ratio, low response consistency, poor image flatness performance, etc.), so that the ultrasonic transducer 100' has poor performance.

[0030] Therefore, the ultrasonic transducer in the related art has the problem of poor performance, and it is necessary to provide some new technical solutions to improve the performance of the ultrasonic transducer.

[0031] It should be understood that the embodiments of the present application provide some technical solutions different from the related art, which can avoid at least part of the defects in the related art Figure 1A and Figure 1B , and can effectively improve the performance of the ultrasonic transducer.

[0032] The specific implementation of the technical solutions of the embodiments of the present application will be described below with reference to the accompanying drawings. It should be noted that in each of the drawings, each structure is not necessarily drawn according to the actual proportion for the sake of illustration. Each of the drawings is not as a limitation on any of the embodiments of the present application.

[0033] Referring to Figure 2A and Figure 2B , Figure 3A and Figure 3B 、 Figure 3C and Figure 3D As shown in FIGS. 1-3, according to a first aspect in embodiments of the present application, an ultrasonic transducer 100 is provided, which comprises a substrate 10, a bottom electrode 20, a piezoelectric layer 30, a top electrode 40 and an excitation electrode 60; the bottom electrode 20 is located on an 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 part of the top electrode 40 is located above the piezoelectric layer 30; the excitation electrode 60 is located on the upper surface of the substrate 10 and is spaced apart from the bottom electrode 20, the piezoelectric layer 30 is provided with an opening part 31, and the top electrode 40 forms an electrical connection with the excitation electrode 60 through the opening part 31; the excitation electrode 60 is configured to receive an excitation signal and apply the excitation signal to the top electrode 40, so as to form an electric field between the top electrode 40 and the bottom electrode 20, thereby exciting the piezoelectric layer 30 to emit an ultrasonic signal; and the bottom electrode 20 is configured 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.

[0034] Based on the above, the ultrasonic transducer 100 in the present application, on the one hand, through the design of the opening part 31 of the piezoelectric layer 30, the top electrode 40 can form an electrical connection with the excitation electrode 60 through the opening part 31 of the piezoelectric layer 30, so that the top electrode 40 can be applied with the excitation signal by the excitation electrode 60, thereby an electric field can be formed between the top electrode 40 and the bottom electrode 20 to effectively excite the piezoelectric layer 30 to emit an ultrasonic signal, and the bottom electrode 20 can also effectively 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, so as to effectively realize the function of the ultrasonic transducer 100; on the other hand, since the top electrode 40 forms an electrical connection with the excitation electrode 60 through the opening part 31, the top electrode 40 can not need to pass through the “top electrode tail” (such as Figure 1A and Figure 1BThe piezoelectric layer 30 and the excitation electrode 60 can be designed without the limitation that the excitation electrode must be partially exposed, and without the limitation that the excitation electrode cannot be completely covered by the piezoelectric layer, so that the piezoelectric layer 30 can extend beyond the position of the excitation electrode 60 in the technical solution of the present application, thereby canceling the many limitations in the related art, so that the ultrasonic transducer 100 can have more possible flexible preparation modes, and because the limitations in the related art are canceled, the relative effective working area (AA area) of the piezoelectric layer 30 of the ultrasonic transducer 100 can be further expanded outward (for example, can be expanded outward beyond the excitation electrode 60), and the top electrode 40 can also expand outward with the piezoelectric layer 30, so that the ultrasonic reflection interface of the piezoelectric layer 30 and the top electrode 40 can be further away from the AA area boundary, thereby reducing noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100, and improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also high, thereby effectively improving the performance of the ultrasonic transducer 100.

[0035] It should be understood that the ultrasonic transducer 100 in the embodiments of the present application has good performance and good application value. For example, if the ultrasonic transducer 100 in the embodiments of the present application is applied to an ultrasonic fingerprint module, because the noise and interference can be reduced, the adverse effects of noise and interference on the image quality of the ultrasonic fingerprint image can be reduced, thereby effectively improving the fingerprint recognition accuracy, improving the user experience of the fingerprint recognition function, and having good application value.

[0036] Optionally, in the present application, the substrate 10 can be a silicon substrate or a TFT (Thin Film Transistor, thin film transistor) substrate. If the demand is met, it can also be other types of substrates.

[0037] Optionally, the piezoelectric layer 30 can include any piezoelectric material. For example, it can include at least one of PVDF (polyvinylidene difluoride) material, lead zirconate titanate material, and lithium niobate material. The PVDF material can include PVDF, PVDF copolymer, etc.

[0038] Optionally, the opening part 31 provided on the piezoelectric layer 30 can penetrate the piezoelectric layer 30, so that the excitation electrode 60 can be exposed to form an electrical connection with the top electrode 40. Optionally, the opening part 31 can be patterned on the piezoelectric layer 30 by any means when the piezoelectric layer 30 is prepared.

[0039] For example, in some optional embodiments, with reference to Figure 2A and Figure 2B , Figure 3A and Figure 3B As shown, the piezoelectric layer 30 can partially cover the excitation electrode 60 and expose a portion of the excitation electrode 60 to the opening 31, so that the top electrode 40 forms an electrical connection with the excitation electrode 60 through the opening 31. Optionally, the minimum distance between the edge of the excitation electrode 60 and the inner wall of the opening 31 is greater than or equal to 10 μm.

[0040] Based on this, such an optional structure allows the top electrode 40 to effectively form an electrical connection with the excitation electrode 60 through the opening 31 of the piezoelectric layer 30. Furthermore, this structure allows the piezoelectric layer 30 to extend outward to cover and / or exceed the excitation electrode 60, and the top electrode 40 can also extend outward along with the piezoelectric layer 30. This allows the ultrasonic reflection interface of the piezoelectric layer 30 and the top electrode 40 to be further away from the boundary of the AA region, thereby reducing noise and interference, improving the signal-to-noise ratio of the ultrasonic transducer 100, improving the response consistency of the ultrasonic transducer 100, and also resulting in higher image flatness of the image obtained by the ultrasonic transducer 100, thus effectively improving the performance of the ultrasonic transducer 100.

[0041] It should also be understood that if the opening 31 is too close to the edge of the excitation electrode 60, it is easy for the opening 31 to extend beyond the excitation electrode 60 during processing. This would result in a smaller connection area between the excitation electrode 60 and the top electrode 40, increasing the likelihood of failure. Therefore, in this embodiment, the distance between the edges of the excitation electrode 60 and the inner wall of the opening 31 is greater than or equal to 10 μm. This ensures the stability of the connection between the excitation electrode 60 and the top electrode 40 while facilitating the manufacturing process, ensuring sufficient connection area between the excitation electrode 60 and the top electrode 40, and reducing the possibility of failure.

[0042] Optionally, refer to Figure 2A and Figure 2B , Figure 3A and Figure 3B As shown, except for the portion of the excitation electrode 60 exposed at the opening 31, the rest of the excitation electrode 60 can be completely covered by the piezoelectric layer 30.

[0043] Based on this, such optional structure can make the piezoelectric layer 30 able to expand outward beyond the excitation electrode 60, and the top electrode 40 can also expand outward with the piezoelectric layer 30, so that the ultrasonic wave reflection interface of the piezoelectric layer 30 and the top electrode 40 and the like can be more away from the AA area boundary, so as to reduce noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100, and improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0044] In some optional embodiments, referring to Figure 3C and Figure 3D , the whole excitation electrode 60 is located in the opening part 31, so that the top electrode 40 forms electrical connection with the excitation electrode 60 through the opening part 31.

[0045] Based on this, in this optional implementation, the piezoelectric layer 30 can not cover the excitation electrode 60, that is, the excitation electrode 60 can be directly located in the opening part 31 as a whole, and then the top electrode 40 can effectively form electrical connection with the excitation electrode 60 through the opening part 31, and because the excitation electrode 60 can be electrically connected with the top electrode 40 in a large area, the electrical connection stability of the two is also better, and the larger opening part 31 is also easier to process, and such structure makes the piezoelectric layer 30 able to expand outward beyond the excitation electrode 60, and the top electrode 40 can also expand outward with the piezoelectric layer 30, so that the ultrasonic wave reflection interface of the piezoelectric layer 30 and the top electrode 40 and the like can be more away from the AA area boundary, so as to reduce noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100, and improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0046] For example, the opening part 31 includes an opening 311 as large as or larger than the excitation electrode 60 (which can be understood below), and then the excitation electrode 60 can be located in the opening part 31 as a whole.

[0047] In some optional embodiments, referring to Figure 3C and Figure 3D , the area of the first vertical projection of the excitation electrode 60 towards the substrate 10 is equal to the area of the first side of the opening part 31, wherein the first side of the opening part 31 is the side of the opening part 31 close to the substrate 10 along the thickness direction of the piezoelectric layer 30.

[0048] Based on this, through such an optional structure, the excitation electrode 60 can be located entirely within the opening portion 31, so that the top electrode 40 can effectively form an electrical connection with the excitation electrode 60 through the opening portion 31, the electrical connection stability is good, and it is also easier to process, and when the top electrode 40 is connected to the excitation electrode 60 through the opening portion 31, the part of the top electrode 40 located in the opening portion 31 can avoid contacting the substrate 10, thereby avoiding short circuit or discharge breakdown in this area, thereby facilitating to improve the performance of the ultrasonic transducer 100.

[0049] In some optional embodiments, the area of the first vertical projection of the excitation electrode 60 towards the substrate 10 is smaller than the area of the first side of the opening portion 31. Optionally, on this basis, the upper surface of the substrate 10 located in the opening portion 31 is not provided with other circuit structures except the excitation electrode 60.

[0050] Thus, through such an optional structure, the excitation electrode 60 can be located entirely within the opening portion 31, so that the top electrode 40 can effectively form an electrical connection with the excitation electrode 60 through the opening portion 31, the electrical connection stability is good, and it is also easier to process, and since the upper surface of the substrate 10 located in the opening portion 31 is not provided with other circuit structures except the excitation electrode 60, the part of the top electrode 40 in the opening portion 31 can also reduce the risk of short circuit or discharge breakdown when contacting the substrate 10.

[0051] In some optional embodiments, in combination with Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D It is understood that the first vertical projection of the excitation electrode 60 towards the substrate 10 can be located within the second vertical projection of the piezoelectric layer 30 towards the substrate 10.

[0052] Based on this, such an optional structure enables the piezoelectric layer 30 to expand outward to cover and / or exceed the excitation electrode 60, and the top electrode 40 can also expand outward with the piezoelectric layer 30, so that the ultrasonic reflection interface of the piezoelectric layer 30 and the top electrode 40 can be more away from the AA area boundary, thereby reducing noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100, improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0053] For example, as Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D As shown, several ultrasonic transducers 100 are illustrated, each representing an example of an excitation electrode 60 with its first vertical projection toward the substrate 10, located within the smallest outer rectangle of a piezoelectric layer 30 with its second vertical projection toward the substrate 10. As can be seen from the examples in the figure, the piezoelectric layer 30 extends outward to cover and exceed the excitation electrode 60.

[0054] In some alternative embodiments, combined with Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D It is understood that the first vertical projection of the excitation electrode 60 toward the substrate 10 can be located within the third vertical projection of the top electrode 40 toward the substrate 10.

[0055] Based on this, such an optional structure allows the top electrode 40 to extend beyond the excitation electrode 60, which allows the ultrasonic reflection interface of the top electrode 40, etc., to be further away from the boundary of the AA region, thereby reducing noise and interference, improving the signal-to-noise ratio of the ultrasonic transducer 100, improving the response consistency of the ultrasonic transducer 100, and also improving the image flatness of the image obtained by the ultrasonic transducer 100, thus effectively improving the performance of the ultrasonic transducer 100.

[0056] For example, such as Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D As shown, several ultrasonic transducers 100 are illustrated, all of which are examples where the first vertical projection is located within the third vertical projection. From the two examples in the figure, it can be seen that the top electrode 40 extends beyond the excitation electrode 60.

[0057] It should be noted that, as Figure 1A and Figure 1BThe shown example of the related art ultrasonic transducer 100' also has the following second partial defect: the design of the top electrode tail 42' in the related art forms ultrasonic reflection points at the corners. For example, if the top electrode tail 42' is a protruding square, ultrasonic reflection points can be formed at the 4 corners (e.g. the 4 90° corners of a protruding square), and the echoes formed by these ultrasonic reflection points will be noise and interference for the ultrasonic signal, and the closer the ultrasonic reflection points are to the active area (Active Area, AA area) of the ultrasonic transducer 100', the stronger the interference generated. In addition, even if the protruding top electrode tail 42' is designed into other shapes (such as semicircular, etc.) other than a protruding square, it is inevitable that reflections will be formed at the junction corner of the top electrode tail 42' and the top electrode body 41', which will directly affect the performance of the ultrasonic transducer 100' (such as easily reducing the signal-to-noise ratio, etc.), making the ultrasonic transducer 100' perform poorly.

[0058] In some optional embodiments, in combination with Figure 2A and Figure 2B It is understood that the third vertical projection of the top electrode 40 towards the substrate 10 of the ultrasonic transducer 100 of the embodiments of the present application can be located within the outer contour of the second vertical projection of the piezoelectric layer 30 towards the substrate 10.

[0059] As Figure 2A and Figure 2B shown, in some optional embodiments of the present application, the top electrode 40 has no "top electrode tail", that is, the top electrode 40 can not protrude beyond the piezoelectric layer 30, except for the part located in the opening part 31, and the other parts are located above the piezoelectric layer 30.

[0060] It should be understood that, due to the above optional structure, the third vertical projection of the top electrode 40 towards the substrate 10 is located within the outer contour of the second vertical projection of the piezoelectric layer 30 towards the substrate 10, so that the top electrode 40 abandons the "top electrode tail", and thus effectively reduces the corners or corners of the top electrode 40, thereby reducing the ultrasonic reflection points with higher intensity, effectively reducing the ultrasonic reflection echoes formed by the ultrasonic reflection points, thereby reducing this part of noise and interference, so that the signal-to-noise ratio of the ultrasonic transducer 100 can be improved, and the response consistency of the ultrasonic transducer 100 is improved, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0061] In some optional embodiments, in combination with Figure 3A and Figure 3B , Figure 3C and Figure 3DIt is understood that the third vertical projection of the top electrode 40 towards the substrate 10 can be partially overlapped with the figure enclosed by the outer contour of the second vertical projection of the piezoelectric layer 30 towards the substrate 10.

[0062] As shown in Figure 3A and Figure 3B , in the above optional embodiments of the present application, the top electrode 40 can be extended beyond the piezoelectric layer 30, so that the third vertical projection is partially overlapped with the figure enclosed by the outer contour of the second vertical projection. Such a structure is relatively convenient to manufacture, which can reduce the manufacturing difficulty of the ultrasonic transducer 100, reduce the process complexity, and the extension of the top electrode 40 beyond the piezoelectric layer 30 can make the ultrasonic reflection interface of the top electrode 40 and the like farther away from the AA region boundary, thereby reducing noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100, improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0063] In the embodiments of the present application, the specific structure of the opening part 31 is not limited. Referring to Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D , in some optional embodiments, the opening part 31 includes at least one opening 311, wherein the at least one opening 311 is located inside the piezoelectric layer 30 and has a spacing from the side wall of the piezoelectric layer 30.

[0064] It is understood that in the present application, the at least one opening 311 of the opening part 31 of the ultrasonic transducer 100 is arranged inside the piezoelectric layer 30 and has a spacing from the side wall of the piezoelectric layer 30, so that the side wall topography of the piezoelectric layer 30 is more complete and flat, and the corners on the side wall of the piezoelectric layer 30 are reduced, thereby reducing the noise caused by the reflection of ultrasonic signals on the side wall of the piezoelectric layer 30, and improving the signal-to-noise ratio of the ultrasonic transducer 100, improving the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby improving the performance of the ultrasonic transducer 100.

[0065] For example, as shown in the examples of Figure 2A and Figure 2B , Figure 3A and Figure 3B , the opening part 31 can include two openings 311, and as shown in the examples of Figure 3C and Figure 3D , the opening part 31 can include one opening 311.

[0066] In some optional embodiments, referring to Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D As shown, all openings 311 of the opening 31 can be located inside the piezoelectric layer 30, and all are spaced from the sidewall of the piezoelectric layer 30.

[0067] Therefore, the sidewall morphology of the piezoelectric layer 30 can be made more complete and flat, reducing the corners on the sidewall of the piezoelectric layer 30. This can better reduce the noise formed by the reflection of ultrasonic signals by the sidewall of the piezoelectric layer 30, thereby improving the signal-to-noise ratio of the ultrasonic transducer 100 and the response consistency of the ultrasonic transducer 100. In addition, the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, which further improves the performance of the ultrasonic transducer 100.

[0068] The specific number of openings 311 in this embodiment is not limited; there may be one or more. In some optional embodiments, refer to... Figure 2A and Figure 2B , Figure 3A and Figure 3B As shown, the opening 31 may include a plurality of openings 311, and the top electrode 40 is electrically connected to the excitation electrode 60 through the plurality of openings 311.

[0069] Therefore, in this embodiment, the top electrode 40 forms an electrical connection with the excitation electrode 60 through multiple openings 311, making the electrical connection between the top electrode 40 and the excitation electrode 60 more stable. This avoids the failure of the electrical connection between the top electrode 40 and the excitation electrode 60 due to an abnormality in the electrical connection within a single opening 311, thereby helping to ensure the normal operation of the ultrasonic transducer 100 and improving its fault tolerance.

[0070] Optionally, refer to Figure 2B , Figure 3B As shown, multiple openings 311 can be spaced out at different positions on the piezoelectric layer 30, and the top electrode 40 can form an electrical connection with different positions on the excitation electrode 60 through the spaced-out openings 311. Figure 2B , Figure 3B The example shown includes two openings 311, but it is not limited to this and may have more in other embodiments.

[0071] In some alternative embodiments, refer to Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D As shown, the depth of at least one opening 311 is less than the thickness of the piezoelectric layer 30.

[0072] Thus, when the excitation electrode 60 protrudes from the upper surface of the substrate 10, the top electrode 40 can be electrically connected to the excitation electrode 60 through the opening 311 with a small depth, and the excitation electrode 60 can be exposed by opening the piezoelectric layer 30 with a small depth, so as to be electrically connected to the top electrode 40, which is convenient in the process.

[0073] In some optional embodiments, the depth of the at least one opening 311 can be equal to the thickness of the piezoelectric layer 30.

[0074] The specific shape of the opening 311 is not limited in the embodiments of the present application, and any regular or irregular shape can be used as long as the requirement is met. For example, in some optional implementations, the shape of the target cross section of the at least one opening 311 can include at least one of a circle, an ellipse, an octagon, and a quadrilateral, wherein the target cross section is a cross section of the opening 311 parallel to the substrate 10.

[0075] It should be understood that the above cross-sectional shape of the opening 311 can ensure effective electrical connection of the top electrode 40 to the excitation electrode 60 through the opening 311. In addition, compared with the "top electrode tail" in the related art, the use of the opening 311 with some optional shapes makes the inner wall of the opening of the piezoelectric layer 30 in the embodiments of the present application and the part of the top electrode 40 located in the opening 311 have smaller reflected waves of ultrasonic signals, thereby reducing noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100 and improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0076] It should be noted that, as shown in the examples of the ultrasonic transducer 100' of the related art in Figure 1A and Figure 1B , the above-mentioned second part of the defects (refer to the foregoing description) still exist, and the use of the opening 311 with a circular or elliptical cross section in some optional embodiments of the present application makes the inner wall of the opening 311 and the part of the top electrode 40 connected to the excitation electrode 60 through the opening 311 also circular or elliptical, which has fewer corners or angles, thereby reducing the ultrasonic reflection points with high intensity, effectively reducing the ultrasonic reflection waves formed by the ultrasonic reflection points, thereby reducing the noise and interference in this part, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100 and improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0077] Optionally, when the opening 311 is in the shape of an octagon, the octagon can be a regular octagon, or can be an irregular octagon.

[0078] The specific size of the opening 311 is not limited in the embodiments of the present application. For example, the minimum circumscribed circle diameter of the first side of the at least one opening 311 can be greater than or equal to 20 um, wherein the first side of the opening 311 is the side of the opening 311 close to the substrate 10 in the thickness direction of the piezoelectric layer 30. Optionally, the minimum circumscribed circle diameter of each part of the opening 311 in the axial direction of the opening 311 is greater than or equal to 20 um. For example, when the first side of the opening 311 is a circle, the minimum circumscribed circle diameter of the first side of the opening 311 can be equal to the diameter of the circle; when the first side of the opening 311 is an ellipse, the minimum circumscribed circle diameter of the first side of the opening 311 can be equal to the major axis of the ellipse; when the first side of the opening 311 is a rectangle (including a square), the minimum circumscribed circle diameter of the first side of the opening 311 can be equal to the diagonal length of the rectangle.

[0079] It should be understood that, on the one hand, the opening 311 of such a size is convenient to manufacture, and can effectively meet the need for stable electrical connection between the top electrode 40 and the excitation electrode 60 through the opening 311; on the other hand, compared with the "top electrode tail" in the related art, the use of the opening 311 of such a size makes the inner wall of the opening of the piezoelectric layer 30 in the embodiments of the present application, and the part of the top electrode 40 located in the opening 311, reflect less echo of the ultrasonic signal, thereby reducing noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100, and improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thereby effectively improving the performance of the ultrasonic transducer 100.

[0080] For example, the minimum circumscribed circle diameter of the first side of the opening 311 can be in the range of 20 um to 30 um. The above preferred range of 20 um to 30 um, on the one hand, can make the opening 311 convenient to manufacture, and effectively meet the need for stable electrical connection between the top electrode 40 and the excitation electrode 60 through the opening 311; on the other hand, the opening 311 will not be too large, so that the opening 311 reflects less echo of the ultrasonic signal, thereby being conducive to ensuring the performance of the ultrasonic transducer 100.

[0081] The appropriate size can be selected as needed. For example, 20 um, 21 um, 22 um, 23 um, 24 um, 25 um, 26 um, 27 um, 28 um, 29 um, 30 um, etc. can be selected.

[0082] Of course, the minimum circumscribed circle diameter of the first side of the opening 311 can also be greater than 30um in the case of meeting the requirements, which is not uniquely limited in the embodiments of the present application.

[0083] In the embodiments of the present application, the opening 311 can include a first side and a second side. The first side of the opening 311 is the side of the opening 311 close to the substrate 10 along the thickness direction of the piezoelectric layer 30. The second side of the opening 311 is the side of the opening 311 away from the substrate 10 along the thickness direction of the piezoelectric layer 30.

[0084] In some optional embodiments, the area of the second side of at least one opening 311 is equal to the area of the first side of the opening 311. Such an opening 311 can better meet the requirement of electrically connecting the top electrode 40 and the excitation electrode 60.

[0085] Optionally, along the direction from away from the substrate 10 to close to the substrate 10, the cross sections of the opening 311 parallel to the substrate 10 can be the same in shape and area.

[0086] In some optional embodiments, the area of the second side of at least one opening 311 is greater than the area of the first side of the opening 311. Using such an opening 311 can improve the preparation flexibility of the ultrasonic transducer 100 and reduce the manufacturing difficulty in the case of meeting the requirements.

[0087] Optionally, along the direction from away from the substrate 10 to close to the substrate 10, the cross sections of the opening 311 parallel to the substrate 10 can be the same in shape and gradually increasing in area. For example, the area of the second side of some openings 311 away from the substrate 10 can be greater than the area of the first side of the opening 311 close to the substrate 10. For example, the inside of the opening 311 can be a reverse circular truncated cone or a reverse ladder truncated cone or a funnel shape, and along the direction from away from the substrate 10 to close to the substrate 10, the area of the cross sections of the opening 311 parallel to the substrate 10 can be gradually changed.

[0088] It should be understood that, under the characteristics of certain processes, the openings 311 with the same area on the first side and the second side are relatively difficult to make, and not only are the openings 311 with the same area on the first side and the second side difficult to make, but the stress effect of the portion of the top electrode 40 in the openings 311 is also large, and the top electrode 40 is prone to cracking during reliability testing. In some optional embodiments of the embodiments of the present application, the openings 311 can be made into openings with a large area on the second side and a small area on the first side (i.e., openings with a larger area on the second side than on the first side), such as a rounded truncated cone or a reversed trapezoidal truncated cone or a funnel, and the like, so that the technical solution of the present application can adapt to the characteristics of these processes, thereby effectively reducing the manufacturing difficulty of the ultrasonic transducer 100, reducing the process complexity, and reducing the stress effect, and reducing the risk of cracking of the top electrode 40 during reliability testing. In some optional embodiments, the axis of the at least one opening 311 is perpendicular to the substrate 10. Such openings 311 are easier to make (e.g., can be conveniently obtained by patterning when the piezoelectric layer 30 is prepared), and therefore the use of such openings 311 can reduce the manufacturing difficulty of the ultrasonic transducer 100 and reduce the process complexity.

[0089] It should be noted that, in addition to the vertical projection, the vertical described elsewhere in the present application can be 90°±5°, and within this range it can be considered vertical.

[0090] In some optional embodiments, at least one inner wall surface of the at least one opening 311 is perpendicular to the substrate 10. Such openings 311 are easier to make (e.g., can be conveniently obtained by patterning when the piezoelectric layer 30 is prepared), and therefore the use of such openings 311 can reduce the manufacturing difficulty of the ultrasonic transducer 100 and reduce the process complexity. For example, referring to Figure 2A and Figure 2B , Figure 3A and Figure 3B , wherein the target cross sections of the openings 311 shown are circular, the axes of the openings 311 are perpendicular to the substrate 10, and the inner wall surfaces of the openings 311 are cylindrical surfaces that are perpendicular to the substrate 10. For another example, if the target cross section of the opening 311 includes but is not limited to a square rectangle (as shown in Figure 3C and Figure 3D ), the opening 311 can have four inner wall surfaces, and if the axes of the openings 311 are perpendicular to the substrate 10, the four inner wall surfaces can be perpendicular to the substrate 10.

[0091] In some optional embodiments, at least one inner wall of the at least one opening 311 has an inclined angle with the substrate 10. In this way, the area of the opening 311 on the side (i.e., the second side of the opening 311) away from the substrate 10 along the thickness direction of the piezoelectric layer 30 can be greater than the area of the opening 311 on the side (i.e., the first side of the opening 311) close to the substrate 10 along the thickness direction of the piezoelectric layer 30. The use of such an opening 311 can improve the manufacturing flexibility of the ultrasonic transducer 100 and reduce the manufacturing difficulty while meeting the requirements. For example, if the inner part of the opening 311 is a reverse circular truncated cone, the inner wall surface of the opening 311 is a reverse circular truncated cone surface, which has an inclined angle with the substrate 10. For another example, if the inner part of the opening 311 is a reverse ladder truncated cone, the opening 311 can have four inner wall surfaces, and the four inner wall surfaces can have an inclined angle with the substrate 10.

[0092] Optionally, the top electrode 40 can be used to apply an excitation signal so that an electric field is formed between the top electrode 40 and the bottom electrode 20 (i.e., a voltage difference is formed on both sides of the piezoelectric layer 30 in the thickness direction), thereby exciting the piezoelectric layer 30 to emit an ultrasonic signal. The bottom electrode 20 can be 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. The ultrasonic detection signal can be an electrical signal generated by the returned ultrasonic signal acting on the piezoelectric layer 30, and the ultrasonic detection signal can be used to generate an image. Specifically, after the top electrode 40 is applied with an excitation signal, an electric field is formed between the top electrode 40 and the bottom electrode 20, a voltage difference is formed on both sides of the piezoelectric layer 30 in the thickness direction, thereby exciting the piezoelectric layer 30 to generate vibration to emit an ultrasonic signal to the outside. In this process, the piezoelectric layer 30 converts an electrical signal into an ultrasonic signal (i.e., mechanical vibration) based on the piezoelectric effect, and the bottom electrode 20 can receive an ultrasonic detection signal (electrical signal) obtained by the returned ultrasonic signal converted by the piezoelectric layer 30 for generating an image. Optionally, when the ultrasonic transducer 100 is used in an ultrasonic fingerprint module, the ultrasonic detection signal can be used to obtain a fingerprint image of a finger.

[0093] It should be noted that for the ultrasonic transducer 100, if the fourth vertical projection of the bottom electrode 20 towards the substrate 10 is located within the vertical projection of the piezoelectric layer 30 towards the substrate 10 (i.e., the second vertical projection) and within the vertical projection of the top electrode 40 towards the substrate 10 (i.e., the third vertical projection), then the effective working area (i.e., the AA area) of the ultrasonic transducer 100 can be the area of the minimum circumscribed rectangle of the fourth vertical projection.

[0094] In some alternative embodiments, the angle between at least one outer sidewall of the top electrode 40 and the normal line of the substrate 10 is less than or equal to 45°. The normal line of the substrate 10 can be a straight line perpendicular to the upper surface of the substrate 10. Such an alternative structure makes the diffraction echo of the ultrasonic signal caused by the boundary profile of the top electrode 40 smaller, thereby better reducing the interference with the use of the ultrasonic transducer 100 and better improving the use effect of the ultrasonic transducer 100. Moreover, the above-mentioned angle range has low requirements on the preparation process, and it is easier to form the top electrode 40, thereby reducing the preparation difficulty of the ultrasonic transducer.

[0095] Preferably, the angle between at least one outer sidewall of the top electrode 40 and the normal line of the substrate 10 is less than or equal to 5°. In this case, it can be basically considered that the at least one outer sidewall of the top electrode 40 is perpendicular to the substrate 10. Such an alternative structure makes the diffraction echo of the ultrasonic signal caused by the boundary profile of the top electrode 40 smaller, thereby reducing the interference with the use of the ultrasonic transducer 100 and improving the use effect of the ultrasonic transducer 100.

[0096] Preferably, the angle between each outer sidewall of the top electrode 40 and the normal line of the substrate 10 is less than or equal to 5°. In this case, it can be basically considered that each outer sidewall of the top electrode 40 is perpendicular to the substrate 10. Such an alternative structure makes the diffraction echo of the ultrasonic signal caused by the boundary profile of the top electrode 40 smaller, thereby better reducing the interference with the use of the ultrasonic transducer 100 and better improving the use effect of the ultrasonic transducer 100.

[0097] 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°.

[0098] Based on this, 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° in the present application. Such an alternative structure makes the diffraction echo of the ultrasonic signal caused by the boundary profile of the top electrode 40 smaller, thereby better reducing the interference with the use of the ultrasonic transducer 100 and better improving the use effect of the ultrasonic transducer 100.

[0099] Preferably, the angle between each outer sidewall of the top electrode 40 and the normal line of the substrate 10 is equal to 0°.

[0100] It should be understood that the closer the angle between each outer sidewall of the top electrode 40 and the normal line of the substrate 10 is to 0°, the closer the outer sidewall is to the vertical of the substrate 10, and the better the use effect of the ultrasonic transducer 100.

[0101] In some alternative embodiments, the junction between the outer sidewall of the top electrode 40 and the upper surface of the top electrode 40 is arc-shaped.

[0102] Based on this, in the present application, the arc-shaped design at the joint between the outer sidewall of the top electrode 40 and the upper surface of the top electrode 40 makes the reflection performance of the ultrasonic signal passing through the joint between the outer sidewall of the top electrode 40 and the upper surface of the top electrode 40 more consistent, so as to avoid too much reflection in some places and too little reflection in some places, thereby facilitating the improvement of the performance of the ultrasonic transducer 100.

[0103] In some optional embodiments, as shown in Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D , at least one sidewall of the top electrode 40 does not exceed the edge of the piezoelectric layer 30. Among them, as shown in the examples of Figure 2A and Figure 2B , each sidewall of the top electrode 40 does not exceed the edge of the piezoelectric layer 30; as shown in the examples of Figure 3A and Figure 3B , or Figure 3C and Figure 3D , multiple sidewalls of the top electrode 40 do not exceed the edge of the piezoelectric layer 30.

[0104] It should be understood that in the embodiments of the present application, at least one sidewall of the top electrode 40 does not exceed the edge of the piezoelectric layer 30, so that at least part of the top electrode 40 can be blocked by the piezoelectric layer 30 without directly contacting the electrically sensitive area on the substrate 10, thereby avoiding short circuit or discharge breakdown, and thus facilitating the improvement of the performance of the ultrasonic transducer 100.

[0105] The excitation electrode 60 can be used to receive an excitation signal from an external circuit and apply the excitation signal to the top electrode 40 electrically connected with the excitation electrode 60. Optionally, the excitation signal can be an alternating current signal, or can also be a pulse signal.

[0106] The excitation electrode 60 is located on the upper surface of the substrate 10 and has a spacing from the bottom electrode 20, so as to avoid the top electrode 40 from being electrically connected between the excitation electrode 60 and the bottom electrode 20.

[0107] In some optional embodiments, referring to Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3DAs shown, the ultrasonic transducer 100 also includes a pad area 90 disposed on the substrate 10, and the pad area 90 can be electrically connected to the bottom electrode 20. Optionally, the pad area 90 can also be electrically connected to the excitation electrode 60, and through the excitation electrode 60, it can be electrically connected to the top electrode 40. In addition, the pad area 90 is also used for connection to external circuitry.

[0108] The pad area 90 is connected to an external circuit, which can transmit the excitation signal input from the external circuit to the excitation electrode 60, so that the excitation electrode 60 can receive the excitation signal and apply it to the top electrode 40. In this application, by setting the pad area 90, the ultrasonic transducer 100 can be easily connected to the external circuit that needs to be used, thereby effectively utilizing the function of the ultrasonic transducer 100.

[0109] Alternatively, the external circuitry can be the circuitry within the electronic device to which the ultrasonic transducer 100 is applied. The pad area 90 can be electrically connected to the external circuitry.

[0110] Optionally, refer to Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D As shown, the pad area 90 may include multiple pads 91. Optionally, some of the multiple pads 91 may be electrically connected to the excitation electrode 60, and some of the pads 91 may be electrically connected to the bottom electrode 20. Optionally, the other pads 91 of the pad area 90 may be used for the extraction and input of other electrical signals. For example, some of the multiple pads 91 may also be connected to the internal circuitry of the ultrasonic transducer 100. Optionally, when the pad area 90 is connected to an external circuit, it may be done through any electrical connection method, such as, but not limited to, soldering, conductive adhesive bonding, etc.

[0111] For example Figure 2B As shown, it illustrates Figure 2A The example ultrasonic transducer 100 is shown in a top-view plan view, schematically illustrating the pad area 90, which includes multiple pads 91 (it should be understood that...). Figure 2B The middle part is omitted Figure 2A (The protective layer 70 in the middle). For example, Figure 3B As shown, it illustrates Figure 3A The example ultrasonic transducer 100 is shown in a top-view plan view, schematically illustrating the pad area 90, which includes multiple pads 91 (it should be understood that...). Figure 3B The middle part is omitted Figure 3A (Protective layer 70 in the middle). For example, Figure 3D As shown, it illustrates Figure 3CFig. 2 is a plan view of the top perspective view of the ultrasonic transducer 100, which schematically shows the pad area 90, including a plurality of pads 91 (it should be understood that Figure 3D In Fig. 2, the protective layer 70 is omitted Figure 3C In Fig. 2, the protective layer 70 is omitted

[0112] In this application, the excitation electrode 60 is electrically connected with the pad area 90 and the top electrode 40, so as to obtain the excitation signal from 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 with the excitation electrode 60 through the excitation electrode 60, so that the ultrasonic transducer 100 can realize the corresponding function.

[0113] For example, a part of the pads of the pad area 90 can be electrically connected with the excitation electrode 60, so as to realize the electrical connection between the pad area 90 and the top electrode 40 through the excitation electrode 60.

[0114] Optionally, in addition to being connected with the excitation electrode 60, the top electrode 40 can also be directly connected with the external circuit in some optional embodiments, so that the top electrode 40 can also directly obtain the excitation signal from the external circuit. The appropriate mode can be selected as needed, which is not limited here.

[0115] In some optional embodiments, referring to Figure 2A 、 Figure 3A 、 Figure 3C The ultrasonic transducer 100 further includes a protective layer 70, which covers at least the upper surface of the top electrode 40, to protect at least part of the top electrode 40.

[0116] Based on this, the protective layer 70 covering at least the upper surface of the top electrode 40 can protect at least part of the top electrode 40, to at least ensure the performance of the top electrode 40, and improve the performance of the ultrasonic transducer 100.

[0117] Optionally, the protective layer 70 can protect the layers of the ultrasonic transducer 100 it covers, which can be an insulating layer, to insulate electricity while also insulating the influence of external water and oxygen and other environmental adverse factors, to ensure that the ultrasonic transducer 100 can work normally for a long time.

[0118] Optionally, referring to Figure 2A 、 Figure 3A 、 Figure 3CAs shown, the protective layer 70 completely covers the top electrode 40. Obviously, this can achieve more comprehensive protection for the top electrode 40, better ensure the performance of the top electrode 40, improve the performance of the ultrasonic transducer 100, and ensure that the ultrasonic transducer 100 can work effectively and normally for a long time.

[0119] Optionally, referring to Figure 2A 、 Figure 3A 、 Figure 3C As shown, the protective layer 70 covers the top electrode 40 and the piezoelectric layer 30. Obviously, the protective layer 70 prepared in this way can achieve 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, improve the performance of the ultrasonic transducer 100, and ensure that the ultrasonic transducer 100 can work effectively and normally for a long time.

[0120] It should be understood that the shape of the protective layer 70 can be set arbitrarily according to requirements, Figure 2A 、 Figure 3A 、 Figure 3C Only some example styles of the protective layer 70 are shown in the figures, in which there are both substantially the same styles and different styles, but none of which is intended to limit the embodiments of the present application.

[0121] Optionally, the protective layer 70 does not cover the pad area 90, so as to ensure that the pad area 90 can be exposed for subsequent electrical connection with external circuits.

[0122] Optionally, the top electrode 40 in the present application can be an electroplated metal layer. That is, the top electrode 40 can be an electroplated top electrode. The top electrode 40 in the form of an electroplated metal layer in the present application has a simple and easy-to-control process during preparation, a small thickness tolerance, and better quality stability, and can effectively improve the performance of the ultrasonic transducer. Compared with other forms of top electrodes, the process difficulty and time period for preparation are lower, and production abnormalities are less likely to occur, so that the product yield of the ultrasonic transducer is also higher.

[0123] Optionally, the junction between the outer sidewall of the top electrode 40 and the upper surface of the top electrode 40 is arc-shaped, which can be formed due to electroplating. That is, the junction is arc-shaped, which can be a special shape feature of the top electrode 40 in the form of an electroplated metal layer, and can have better beneficial effects.

[0124] Optionally, the top electrode 40 can be an electroplated metal layer formed on the upper surface of the seed metal layer 50. In some optional embodiments, referring to Figure 2AAs shown, the ultrasonic transducer 100 further comprises a seed metal layer 50, which is located between the piezoelectric layer 30 and the top electrode 40, and the thickness of the seed metal layer 50 is less than the thickness of the top electrode 40. Optionally, within the opening portion 31, the top electrode 40 forms an electrical connection with the excitation electrode 60 through a part of the seed metal layer 50.

[0125] It should be understood that, in the present application, the seed metal layer 50 can facilitate the formation of the top electrode 40 in the form of an electroplated metal layer, and obtain a top electrode 40 with good performance, and make the top electrode 40 and the excitation electrode 60 can be effectively electrically connected through the seed metal layer 50 located within the opening portion 31 of the piezoelectric layer 30, so as to improve the performance of the ultrasonic transducer 100. Moreover, the ultrasonic transducer 100 provided by the present application has a simple structure, and therefore, the manufacturing process is simple and the cost is low.

[0126] In the present application, the thickness of the seed metal layer 50 is not specifically limited and can be selected as needed. In some optional embodiments, the thickness of the seed metal layer 50 is less than or equal to 2 um. The seed metal layer 50 with such a thickness range is not too thin or too thick, and has good step coverage on the relief terrain of the substrate, which can effectively meet the electroplating requirements and facilitate to ensure the performance of the top electrode 40 in the form of an electroplated metal layer.

[0127] In the present application, the type of metal material of the seed metal layer 50 is not specifically limited. Any metal material can be used as needed.

[0128] Optionally, the seed metal layer 50 can be a single-layer metal. Optionally, the seed metal layer 50 can also be a multi-layer metal. The setting can be made as needed, and is not limited herein.

[0129] In some optional embodiments, the seed metal layer 50 is a double-layer metal. Optionally, the seed metal layer 50 comprises a first metal layer and a second metal layer, and the first metal layer is located between the piezoelectric layer 30 and the second metal layer, and the second metal layer is located between the first metal layer and the top electrode 40. Optionally, the resistivity of the first metal layer is higher than the resistivity of the second metal layer.

[0130] The first metal layer and the second metal layer can be any feasible metal layer. For example, the first metal layer can be made of titanium, titanium-tungsten alloy, chromium, i.e., the first metal layer can be at least one of a titanium layer, a titanium-tungsten alloy layer, and a chromium layer. For example, the second metal layer can be made of copper, gold, nickel-vanadium alloy, i.e., the second metal layer can be at least one of a copper layer, a gold layer, and a nickel-vanadium alloy layer. When the seed metal layer 50 is made, the first metal layer can be formed on at least the upper surface of the piezoelectric layer 30, and then the second metal layer is formed on the first metal layer. When the top electrode 40 is formed, the second metal layer is formed on the second metal layer, so that the first metal layer is between the piezoelectric layer 30 and the second metal layer, and the second metal layer is between the first metal layer and the top electrode 40.

[0131] In the present application, the seed metal layer 50 adopts a double-layer metal layer, which has the following advantages: taking the first metal layer as a titanium layer or a titanium-tungsten alloy layer and the second metal layer as a copper layer as an example, the second metal layer (for example, a copper layer, a gold layer, or a nickel-vanadium alloy layer) has a lower resistivity and better conductivity, so that the effect is better when the top electrode 40 in the form of an electroplated metal layer is formed on the second metal layer, which is also conducive to the stability of the electroplating process, and the top electrode 40 in the form of an electroplated metal layer has better performance. The first metal layer (for example, 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 act as a barrier layer to prevent the metal material of the second metal layer from diffusing downward into the lower layer material (for example, the piezoelectric layer 30), and the first metal layer can stably act as a 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, so that the top electrode 40 in the form of an electroplated metal layer formed by the seed metal layer 50 has better performance, which can effectively improve the performance of the ultrasonic transducer 100.

[0132] Optionally, the thickness of the first metal layer is less than or equal to 1 um, and the thickness of the second metal layer is less than 2 um. The first metal layer and the second metal layer with such thickness range are not too thin or too thick, have better step coverage on the relief terrain of the substrate, can effectively meet the electroplating requirements, and facilitate the performance of the top electrode 40 in the form of an electroplated metal layer.

[0133] Optionally, the sum of the thicknesses of the first metal layer and the second metal layer can be less than or equal to 2 um, to meet the requirement that the thickness of the seed metal layer 50 is less than 2 um in the foregoing optional embodiment.

[0134] Optionally, the thickness of the first metal layer can be less than the thickness of the second metal layer, so that the first metal layer can meet the requirement of preventing the metal material of the second metal layer from diffusing downward into the lower layer material, and the second metal layer can meet the requirement of thickness uniformity when electroplating the top electrode 40.

[0135] The structure of the top electrode 40 is not limited in the embodiments of this application. For example, the top electrode 40 can be a single metal layer, a multilayer metal stack, or an alloy layer. In some optional embodiments, the top electrode 40 can be made of any suitable metal material. For example, it can be at least one of tin, copper, nickel, gold, silver, chromium, zinc, titanium, and lead, or an alloy of at least two of tin, copper, nickel, gold, silver, chromium, zinc, titanium, and lead. That is, optionally, the top electrode 40 can 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, or the top electrode 40 can 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. It should be understood that the above-described forms of the top electrode 40 can effectively guarantee the performance of the top electrode 40, thereby guaranteeing the performance of the prepared ultrasonic transducer. In the optional embodiment where the top electrode 40 is an electroplated metal layer, due to the characteristics of electroplating, the top electrode 40 can be a pure metal layer. For example, the top electrode 40 may optionally 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, or a pure lead layer. When the top electrode 40 is obtained by electroplating at least two of the aforementioned metal materials such as tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead, that is, when it can be at least two of the following 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, or pure lead layer, then the top electrode 40 can be a metal stack. For example, in one example, the top electrode 40 can be a stack of pure copper and pure tin, for example, a copper layer can be electroplated first and then a tin layer can 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, one example of an alloy layer is a pure tin-silver alloy layer. It should be understood that the above-described form of the top electrode 40 effectively ensures its performance, thereby guaranteeing the performance of the fabricated ultrasonic transducer.

[0136] It should be understood that the above description is only some optional embodiments of the ultrasonic transducer scheme of this application, and is not a limitation on the embodiments of this application.

[0137] According to a second aspect of the embodiments of this application, a method for fabricating an ultrasonic transducer is provided, which is capable of fabricating the ultrasonic transducer 100 described in the first aspect above. (Refer to...) Figure 4 The flowchart shown illustrates that the preparation method includes steps S102-S106, specifically: S102: A bottom electrode and an excitation electrode are formed on the upper surface of the substrate, wherein there is a gap between the excitation electrode and the bottom electrode.

[0138] In the present application, the bottom electrode 20 can be formed on the upper surface of the substrate 10 by any suitable method. For example, the method can include, but is not limited to, deposition, etching, and the like.

[0139] In the present application, the excitation electrode 60 can be formed on the upper surface of the substrate 10 by any suitable method. For example, the method can include, but is not limited to, deposition, etching, and the like.

[0140] In some optional embodiments, the preparation method further includes forming a pad area 90 on the upper surface of the substrate, and the pad area 90 is electrically connected to the excitation electrode 60 and the bottom electrode 20, respectively. The foregoing description of the bottom electrode 20, the excitation electrode 60, the pad area 90, and the like is also described above, and can be understood with reference to the foregoing, which will not be repeated here.

[0141] S104: Forming a piezoelectric layer on the substrate, the piezoelectric layer covering the bottom electrode and at least partially covering the excitation electrode, and forming an opening portion in the piezoelectric layer, through which at least part of the excitation electrode is exposed.

[0142] Optionally, the piezoelectric layer 30 can include any piezoelectric material. For example, the piezoelectric material can include at least one of a PVDF material, a lead zirconate titanate material, and a lithium niobate material. The PVDF material can include PVDF, a PVDF copolymer, and the like. In the present application, the piezoelectric layer 30 can be formed on the substrate 10 by any suitable method, which is not particularly limited here. For example, the method can include, but is not limited to, screen printing, coating, dry film lamination, and the like. Alternatively, the method can include physical or chemical vapor deposition, such as sputtering, evaporation, and the like.

[0143] Optionally, the piezoelectric layer 30 can be patterned to form an opening portion 31, through which at least part of the excitation electrode 60 is exposed. It should be understood that the details of the piezoelectric layer 30 and the opening portion 31 have been described in detail in the ultrasonic transducer 100 embodiments described above, which can be understood with reference to the foregoing, and will not be repeated here.

[0144] The patterning method can be optional as needed. For example, in some embodiments, the piezoelectric layer 30 can be patterned by using a method of glue coating + exposure + dry etching, so that the piezoelectric layer 30 can form an opening portion 31 that exposes at least part of the excitation electrode 60.

[0145] For example, some optional implementation processes of step S104 can be understood with reference to the following description: first, form a whole piezoelectric layer 30 above the substrate 10, then form a whole photoresist layer above the piezoelectric layer 30 by a coating process (such as spin coating, etc.), expose and develop the photoresist layer, remove the photoresist layer covering at least the target part of the piezoelectric layer 30 which needs to be removed to form the opening part 31, so as to expose the target part, and the photoresist layer covering other parts of the piezoelectric layer 30 which need to be reserved is reserved, then remove the target part by dry etching to form the opening part 31, and then remove the remaining photoresist layer, so as to achieve step S104. It can be understood that the above implementation process is only an example process, and other optional ways can also be used for implementation, which is not uniquely limited here.

[0146] S106: Form a top electrode above the piezoelectric layer, and make the top electrode form an electrical connection with the excitation electrode through the opening part, to prepare an ultrasonic transducer.

[0147] The top electrode 40 can be formed above the piezoelectric layer 30 in any way, and the top electrode 40 can form an electrical connection with the excitation electrode 60 through the opening part 31, to prepare the ultrasonic transducer 100.

[0148] Based on this, the ultrasonic transducer 100 prepared by the optional preparation method of steps S102-S106 of the present application can make the top electrode 40 form an electrical connection with the excitation electrode 60 through the opening part 31, so that the top electrode 40 can not be connected with the excitation electrode 60 through the "top electrode tail" (such as the example shown in Figure 1A and Figure 1B Therefore, when preparing the piezoelectric layer 30 and the excitation electrode 60, it is not necessary to limit that "the excitation electrode must be partially exposed", and it is also not necessary to limit that "the excitation electrode cannot be completely covered by the piezoelectric layer", so that the piezoelectric layer 30 prepared in the technical solution of the present application can be outside the position of the excitation electrode 60, thus canceling many limitations in the related art, so that the ultrasonic transducer 100 can have more possible flexible preparation ways, and because the limitations in the related art are canceled, the relative effective working area (i.e. the AA area) of the piezoelectric layer 30 of the prepared ultrasonic transducer 100 can be further expanded (for example, it can be expanded to be outside the excitation electrode 60), and the top electrode 40 can also be expanded with the piezoelectric layer 30, so that the ultrasonic reflection interface of the piezoelectric layer 30 and the top electrode 40 can be more away from the AA area boundary, so as to reduce noise and interference, so as to improve the signal-to-noise ratio of the ultrasonic transducer 100, and improve the response consistency of the ultrasonic transducer 100, and the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, so as to effectively improve the performance of the prepared ultrasonic transducer 100.

[0149] The specific implementation of step S106 is not limited in this application, and a variety of optional methods can be used to make the top electrode connected to the excitation electrode 60 through the opening 31.

[0150] In some alternative embodiments, refer to Figure 5 The flowchart shown indicates that the method for preparing the top electrode in step S106 may include the following steps S1062~S1066, specifically: S1062: A seed metal layer is formed on the upper surface of the piezoelectric layer, and the seed metal layer covers the exposed excitation electrode through the opening.

[0151] Optionally, in the optional preparation methods of steps S1062 to S1066, the top electrode 40 in the form of an electroplated metal layer can be prepared by electroplating, which can prepare a top electrode 40 in the form of an electroplated metal layer. Figure 2A and Figure 2B The example shown is an ultrasonic transducer 100.

[0152] In this application, a seed metal layer 50 is formed on at least the upper surface of the piezoelectric layer 30. The seed metal layer 50 can serve as the cathode (i.e., the electroplating substrate) for electroplating, so that the top electrode 40 can be obtained in subsequent steps, thereby realizing the fabrication of the ultrasonic transducer 100.

[0153] Optionally, when forming a seed metal layer 50 on at least the upper surface of the piezoelectric layer 30 in step S104, a first metal layer can be formed first 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, such that the first metal layer is located between the piezoelectric layer 30 and the second metal layer. In the subsequent electroplating step, electroplating can be performed on the second metal layer.

[0154] In this application, a seed metal layer 50 can be formed. For example, the seed metal layer 50 can be formed by screen printing or any other optional method. In some optional embodiments, the upper surface of the piezoelectric layer 30, the inner wall surface of the opening 31, and the excitation electrode 60 within the opening 31 can all be covered by the seed metal layer 50 using a cryogenic sputtering method. Optionally, the cryogenic sputtering temperature is controlled below 135°C.

[0155] Based on this, the seed metal layer 50 can be effectively prepared by low-temperature sputtering, and the temperature is controlled below 135°C. While ensuring the effect of the seed metal layer 50 prepared by low-temperature sputtering, the risk of the piezoelectric layer 30 being reduced or failing due to high temperature can be effectively avoided, thus ensuring the function of the piezoelectric layer 30.

[0156] Preferably, the temperature of the low-temperature sputtering is 70-110°C. In this temperature range, the effect of the low-temperature sputtering can be better ensured, and the risk of the piezoelectric layer 30 being degraded or disabled due to high temperature can be better avoided, and the function of the piezoelectric layer 30 can be better ensured.

[0157] Optionally, a seed metal layer 50 can be formed on the substrate 10 (for example, by low-temperature sputtering), so that the upper surface of the piezoelectric layer 30, the inner wall surface of the opening portion 31, and the excitation electrode 60 in the opening portion 31 are all covered by the seed metal layer 50. It should be understood that forming the seed metal layer 50 on the substrate 10 can form the seed metal layer 50 on any existing structure on the substrate 10, which can reduce the process difficulty.

[0158] S1064: Form a containment structure above the substrate, and form a containing space for preparing the top electrode above the piezoelectric layer through the containment structure.

[0159] The present application can form a containment structure 80 above the substrate 10, and form a containing space 81 above the piezoelectric layer 30 through the containment structure 80, which can be used as a containment function when the top electrode 40 is subsequently prepared, so as to ensure that the top electrode 40 prepared can be more accurately ensured to be in a predetermined position, reduce the position error of the top electrode 40, and further improve the quality stability of the top electrode 40 and the performance of the ultrasonic transducer 100 prepared.

[0160] Optionally, the containment structure 80 can be removed after use and not retained in the ultrasonic transducer 100, but only used as a temporary structure for preparing the ultrasonic transducer 100.

[0161] In some optional embodiments, the angle between at least one inner side wall of the containment structure 80 formed in step S1064 and the normal line of the substrate 10 is less than or equal to 45°, the angle between at least one outer side wall of the top electrode 40 subsequently prepared and the normal line of the substrate 10 is less than or equal to 45°, and the thickness of the containment structure 80 is not less than the thickness of the top electrode 40. Through such a containment structure 80, when the seed metal layer in the containing space is electroplated in the subsequent step, the at least one outer side wall of the top electrode 40 electroplated can have an angle less than or equal to 45° between the at least one outer side wall and the normal line of the substrate 10 through the limiting of the containment structure 80. Such an optional structure can make the diffraction echo of the ultrasonic signal caused by the boundary topography of the top electrode 40 smaller, thereby better reducing the interference on the use of the ultrasonic transducer 100 and better improving the use effect of the ultrasonic transducer 100. Moreover, the above-mentioned angle range has low requirements on the preparation process, and the top electrode 40 is easier to form, thereby reducing the preparation difficulty of the ultrasonic transducer.

[0162] In some optional embodiments, the angle between each inner sidewall of the enclosing structure 80 and the normal line of the substrate 10 is less than or equal to 45°. In the embodiments of the present application, the angle between each outer sidewall of the top electrode 40 and the normal line of the substrate 10 is less than or equal to 45°.

[0163] Preferably, the angle between at least one inner sidewall of the enclosing structure 80 and the normal line of the substrate 10 is less than or equal to 5°. Preferably, the angle between at least one outer sidewall of the top electrode 40 and the normal line of the substrate 10 is less than or equal to 5°.

[0164] Preferably, the angle between each inner sidewall of the enclosing structure 80 and the normal line of the substrate 10 is less than or equal to 5°. Preferably, the angle between each outer sidewall of the top electrode 40 and the normal line of the substrate 10 is less than or equal to 5°.

[0165] Preferably, the angle between at least one inner sidewall of the enclosing structure 80 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°.

[0166] Preferably, the angle between each inner sidewall of the enclosing structure 80 and the normal line of the substrate 10 is equal to 0°. Preferably, the angle between each outer sidewall of the top electrode 40 and the normal line of the substrate 10 is equal to 0°.

[0167] The specific implementation of step S1064 is not limited in the present application. In some optional embodiments, step S1064 can include: disposing a photoresist layer above the substrate 10, and patterning and curing the photoresist layer to form the enclosing structure 80; wherein the patterning and curing of the photoresist layer includes: patterning the photoresist layer to enclose a containing space 81 for preparing the top electrode 40, and then curing.

[0168] Optionally, the disposing of the photoresist layer on the upper surface of the substrate 10 can be achieved by a series of coating methods such as spin coating, spray coating, roller coating, slot coating, etc., or by using a dry film lamination method. Optionally, the patterning and curing of the photoresist layer can be achieved by any feasible method such as exposure and development, dry etching, wet etching, etc., which is not specifically limited herein.

[0169] For example, taking spin coating as an example, in an optional manner, a whole layer of photoresist layer can be spin coated on the upper surface of the substrate 10, and the photoresist layer is patterned and cured by exposure and development, so that the photoresist layer is patterned to enclose a containing space 81 for preparing the top electrode 40 above the piezoelectric layer 30, and then cured to form the enclosing structure 80. The opening portion 31 is in communication with the containing space 81.

[0170] Optionally, the curing temperature of the photoresist during curing is controlled below 135°C, so as to effectively ensure the curing effect and avoid the risk of reducing or losing the piezoelectric performance of the piezoelectric layer 30 due to high temperature, and ensure the function of the piezoelectric layer 30. Preferably, it can be 70°C-110°C.

[0171] Optionally, the enclosing structure 80 can be a non-conductive material. Optionally, the enclosing structure 80 can be made of an organic material, which can be at least one of the following materials, for example: polyimide (PI), poly-p-phenylene benzobisoxazole (PBO), epoxy resin, acrylic resin, etc. The enclosing structure 80 can also be made of an organosiloxane composite material. For example, the organosiloxane composite material can include but is not limited to organosilicon ring, silicone rubber, silicone resin material, etc. It should be understood that the enclosing structure 80 can be effectively prepared by mixing the above-mentioned single material or two different materials in the present application, so as to obtain an ultrasonic transducer with better performance.

[0172] S1066: Power on the seed metal layer, and at least the seed metal layer in the containing space is electroplated to obtain a top electrode, so that the top electrode is electrically connected with the excitation electrode through the seed metal layer in the opening part.

[0173] In the present application, the seed metal layer 50 can be used as the cathode (i.e. the electroplating base) for electroplating, and the seed metal layer 50 is powered on to at least electroplate the seed metal layer 50 in the containing space to obtain the top electrode 40.

[0174] In the present application, the top electrode 40 is obtained by electroplating based on the electrolysis principle. On the cathode (electroplating base, i.e. the seed metal layer 50) for electroplating, metal cations are reduced to metal atoms by accepting electrons and deposited to form a dense metal plating layer. The metal plating layer obtained by electroplating is dense, without delamination, pores, resin agglomeration and other abnormalities. It should be understood that the metal plating layer after electroplating is the top electrode 40, and therefore the top electrode 40 has good performance, which is beneficial to improve the performance of the prepared ultrasonic transducer 100.

[0175] In some optional embodiments, the metal material used for electroplating in the present application includes at least one of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, lead, or an alloy material including at least two of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead. By using the above-mentioned at least one material, the top electrode 40 can be effectively electroplated and the performance of the top electrode 40 can be ensured, thereby ensuring the performance of the prepared ultrasonic transducer.

[0176] Based on this, the top electrode 40 prepared through the above steps S1062-S1064 in the present application can be effectively electrically connected with the seed metal layer 50 in the opening part 31 of the piezoelectric layer 30 and the excitation electrode 60, and the top electrode 40 of the ultrasonic transducer 100 is prepared by electroplating the seed metal layer, so that the thickness of the prepared top electrode 40 can be better controlled by electroplating to achieve the required thickness, so that the preparation process of the ultrasonic transducer 100 is simpler and easier to control, and the thickness tolerance of the prepared top electrode 40 is smaller, so that the quality stability of the top electrode 40 is better, and the performance of the prepared ultrasonic transducer 100 can be effectively improved. On the other hand, since the top electrode 40 can be obtained by electroplating in the containing space surrounded by the enclosing structure 80, the prepared top electrode 40 can be more accurately ensured to be in a predetermined position, the position error of the top electrode 40 is reduced, and the quality stability of the top electrode 40 is further improved, and the performance of the prepared ultrasonic transducer 100 is improved. On the other hand, the operation steps of the top electrode 40 prepared by electroplating to achieve the required thickness in the present application are less, which can effectively reduce the process difficulty and time period, and reduce the probability of production abnormalities.

[0177] It should be understood that the specific process steps of electroplating can be performed in any suitable manner, which will not be described here.

[0178] Optionally, after the top electrode is prepared, the enclosing structure 80 can be removed. For example, the enclosing structure 80 made of a photoresist layer can be removed by a photoresist removal process (for example, a photoresist removal process dissolves the enclosing structure 80 to remove it).

[0179] Optionally, after the top electrode is prepared, the excess part (i.e. the part not electroplated with the top electrode 40) in the non-electroplated metal region of the seed metal layer 50 can be etched to remove it.

[0180] In some other optional embodiments, the way of preparing the top electrode in step S106 can include: disposing a top electrode paste above the piezoelectric layer 30, so that the top electrode paste contacts the excitation electrode 60 through the opening part 31, and forming the top electrode 40 after the top electrode paste is solidified, so that the top electrode 40 is electrically connected with the excitation electrode 60 through the opening part 31.

[0181] For example, a printing process can be employed to dispose the top electrode paste over the piezoelectric layer 30. For another example, a spraying process can be employed to dispose the top electrode paste over the piezoelectric layer 30. Taking the printing process as an example, the printing process can be a silk screen printing process or a steel screen printing process. When printing the top electrode paste over the piezoelectric layer 30, the printed top electrode paste is relied on its fluidity to enter the opening portion 31 to contact the excitation electrode 60 exposed in the opening portion 31, and then the top electrode paste is solidified to form the top electrode 40 electrically connected with the excitation electrode 60. It can be understood that, by such printing, the top electrode 40 can be effectively prepared and the top electrode 40 can be effectively electrically connected with the excitation electrode 60 through the opening portion 31.

[0182] Optionally, when the top electrode 40 is prepared by disposing the top electrode paste in a manner such as silk screen printing, the top electrode 40 can partially extend beyond the edge of the piezoelectric layer 30 (which can be understood in combination with the process examples shown in Figure 6B , and Figure 3A , and Figure 3B It should be understood that, since the process precision of the silk screen printing process and the like is generally poorer than that of the electroplating process, if the top electrode 40 is required not to extend beyond the edge of the piezoelectric layer 30, a larger chip area is required as a buffer space, and a larger piezoelectric layer 30 is required to be prepared, which cannot meet the miniaturization size requirement of the ultrasonic transducer 100 in some cases. Moreover, when the size of the ultrasonic transducer 100 is fixed, if the top electrode 40 is allowed to extend beyond the edge of the piezoelectric layer 30, the process precision of the silk screen printing process and the like is more suitable, and the printed top electrode paste can be better filled in the opening portion 31 of the piezoelectric layer 30, so that the prepared top electrode 40 can be more stably electrically connected with the excitation electrode 60, thereby ensuring the performance of the ultrasonic transducer 100.

[0183] Of course, when the top electrode 40 is prepared by disposing the top electrode paste in a manner such as silk screen printing, the top electrode 40 can also not extend beyond the edge of the piezoelectric layer 30, as long as the requirement can be met, which is not uniquely limited in the present application.

[0184] It should be understood that, in addition to the electroplating and printing processes described above, other optional methods can also be employed to manufacture the top electrode 40, which are not limited herein.

[0185] In some optional embodiments, the preparation method of the embodiments of the present application further comprises: preparing a protective layer 70 covering at least part of the top electrode 40.

[0186] Based on this, by preparing the protective layer 70 covering at least part 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 and improve the performance of the prepared ultrasonic transducer 100.

[0187] Optionally, the protective layer 70 can protect each layer of the covered ultrasonic transducer 100. It can be an insulating layer that provides electrical insulation while also isolating the effects of external water, oxygen, and other adverse environmental factors, ensuring that the ultrasonic transducer 100 can operate normally and effectively for a long time.

[0188] Optionally, the protective layer 70 can be prepared in any feasible manner, without limitation. For example, it can be prepared by screen printing or exposure and development. Alternatively, it can be prepared by coating or dry film lamination. Optionally, when preparing the protective layer 70, the resulting protective layer 70 should be kept away from covering the pad area 90 to ensure that the pad area 90 is exposed for subsequent electrical connection with external circuits.

[0189] To facilitate a further understanding of the fabrication scheme of the ultrasonic transducer in the embodiments of the application, the following is combined with... Figure 6A , Figure 6B The overall process of several alternative preparation schemes is described.

[0190] <Optional Preparation Scheme 1> Reference Figure 6A The schematic diagram of the fabrication process of the ultrasonic transducer is shown. This process can be used to fabricate transducers such as… Figure 2A The ultrasonic transducer 100 shown is fabricated using the following steps: Step 1: A bottom electrode 20 and an excitation electrode 60 are formed on the upper surface of a substrate 10, and a piezoelectric layer 30 is formed above the substrate 10, covering the bottom electrode 20 and at least partially covering the excitation electrode 60. An opening 31 is formed in the piezoelectric layer 30, through which at least part of the excitation electrode 60 is exposed. There is a gap between the excitation electrode 60 and the bottom electrode 20. In addition, a pad area 90 is also prepared on the substrate 10. Step 2: A seed metal layer 50 is formed on the upper surface of the substrate 10 by low-temperature sputtering. The seed metal layer 50 covers the upper surface of the piezoelectric layer 30, the inner wall of the opening 31, and the excitation electrode 60 in the opening 31, and also covers the excitation electrode 60 and the pad area 90. The temperature of the low-temperature sputtering is controlled below 135°C. Step 3: A whole layer of photoresist is formed on the substrate 10 (e.g., by spin coating), and the photoresist is patterned and cured to form a barrier structure 80 that surrounds the space for preparing the top electrode 40 on the piezoelectric layer 30. The opening 31 is connected to the space 81. The curing temperature of the photoresist is controlled below 135°C. The inner sidewall of the barrier structure 80 can be made as perpendicular as possible to the substrate 10 (that is, the angle between the inner sidewall of the barrier structure 80 and the normal of the substrate 10 should be as close as possible to 0°). Step 4: power on the seed metal layer 50, and electroplate the seed metal layer 50 in the containing space (i.e. the area not covered by the blocking structure 80) to obtain the top electrode 40, and try to make the outer sidewall of the top electrode 40 perpendicular to the substrate 10 (i.e. try to make the included angle between the outer sidewall of the top electrode 40 and the normal line of the substrate 10 close to 0°); Step 5: remove the blocking structure 80 formed by the photoresist through a photoresist removal process; Step 6: remove the seed metal layer 50 in the non-electroplated metal area through an etching process, wherein at least the seed metal layer 50 covering the pad area 90 is removed to expose the pad area 90 so that the pad area 90 can be connected to an external circuit; 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, and obtain the ultrasonic transducer 100.

[0191] It should be understood that Figure 2A , Figure 6A the examples shown in the above are not intended to limit the embodiments of the present application in any way.

[0192] <Optional Preparation Scheme 2> Referring to the process schematic diagram of the preparation scheme of the ultrasonic transducer shown in Figure 6B , the ultrasonic transducer 100 shown in Figure 6B can be prepared through the process, and the preparation scheme includes the following steps: Step 1: form the bottom electrode 20 and the excitation electrode 60 on the upper surface of the substrate 10, and form the piezoelectric layer 30 covering the bottom electrode 20 and at least partially covering the excitation electrode 60 above the substrate 10, and form the opening part 31 in the piezoelectric layer 30 to expose at least part of the excitation electrode 60 through the opening part 31, and there is a spacing between the excitation electrode 60 and the bottom electrode 20, and further prepare the pad area 90 on the substrate 10; Step 2: brush the top electrode paste on the top of the piezoelectric layer 30 through a screen printing process, so that the top electrode paste enters the opening part 31 and contacts the excitation electrode 60, and after the top electrode paste is solidified, the top electrode 40 is formed to make the top electrode 40 form an electrical connection with the excitation electrode 60 through the opening part 31; Step 3: 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, and obtain the ultrasonic transducer 100.

[0193] It should be understood that Figure 3A , Figure 6B the examples shown in the above are not intended to limit the embodiments of the present application in any way. In addition, the example of the ultrasonic transducer 100 shown in Figure 3A can also be prepared by using the process of the optional preparation scheme 2.

[0194] It should also be understood that the above optional preparation scheme 1 and optional preparation scheme 2 are only a few optional examples of the embodiments of the present application, and do not serve as any limitation on the embodiments of the present application, and in addition, the introduction is relatively simple, and can also be understood in combination with the related description of the foregoing embodiments.

[0195] It should be noted that, as for the preparation method of the ultrasonic transducer 100 of the second aspect, the related content can also be understood with reference to the embodiments of the ultrasonic transducer 100 of the first aspect. In addition, the foregoing description is only some optional embodiments of the ultrasonic transducer scheme of the embodiments of the present application, and is not any limitation on the embodiments of the present application.

[0196] According to the third aspect of the embodiments of the present application, referring to Figure 7 , an ultrasonic fingerprint module 200 is provided, which comprises the ultrasonic transducer 100 provided in the first aspect.

[0197] Due to the ultrasonic fingerprint module 200 of the third aspect, which comprises the ultrasonic transducer 100 of the first aspect, the ultrasonic fingerprint module 200 has better performance and can better achieve the ultrasonic fingerprint function.

[0198] Optionally, in the ultrasonic fingerprint module 200, the excitation electrode 60 is configured to receive an excitation signal and apply the excitation signal to the top electrode 40, so as to form an electric field between the top electrode 40 and the bottom electrode 20, to excite the piezoelectric layer 30 to emit an ultrasonic signal, and the bottom electrode 20 is configured 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, to be used for realizing fingerprint identification.

[0199] In some optional embodiments, the ultrasonic fingerprint module 200 further comprises an adhesive layer, and the adhesive layer is configured to bond the ultrasonic transducer 100 of the ultrasonic fingerprint module 200 to an electronic device.

[0200] According to the fourth aspect of the embodiments of the present application, referring to Figure 8A , Figure 8B , an electronic device 300 is provided, which comprises the ultrasonic transducer 100 provided in the first aspect or the ultrasonic fingerprint module 200 provided in the third aspect.

[0201] In some optional embodiments, the electronic device 300 further comprises a screen 320, a back plate and a side frame.

[0202] Optionally, when the electronic device 300 comprises the ultrasonic transducer 100, the ultrasonic transducer 100 can be attached to the lower surface of the screen 320 or attached to the inner side of the back plate or attached to the inner side of the side frame.

[0203] Optionally, when the electronic device 300 includes an ultrasonic fingerprint module 200, the ultrasonic fingerprint module 200 can be attached to the lower surface of the screen 320, the inner side of the back panel, or the inner side of the side bezel. That is, the ultrasonic fingerprint module 200 can be an under-display ultrasonic fingerprint module, a rear ultrasonic fingerprint module, or a side ultrasonic fingerprint module of the electronic device 300. This enables under-display ultrasonic fingerprint recognition, rear ultrasonic fingerprint recognition, or side ultrasonic fingerprint recognition.

[0204] Optionally, the electronic device 300 can be any electronic device, including but not limited to mobile phones, computers, etc. It should be understood that this application does not limit the way the ultrasonic transducer 100 or the ultrasonic fingerprint module 200 is installed in the electronic device 300.

[0205] As an example, taking electronic device 300 as a mobile phone that includes ultrasonic transducer 100, refer to... Figure 9 As shown, the ultrasonic transducer 100 can be bonded to the underside of the screen 320 of the electronic device 300 via the adhesive layer 310 for under-screen ultrasonic biometric detection. It should be understood that... Figure 9 China is Figure 2A The optional ultrasonic transducer 100 is provided as an example for ease of understanding and is not intended to limit the scope of this application. The ultrasonic transducers of any other optional embodiments can be deduced by analogy, and no further examples will be given here.

[0206] As another example, taking an electronic device 300 as a mobile phone that includes an ultrasonic fingerprint module 200, the ultrasonic fingerprint module 200 can be bonded to the underside of the mobile phone screen of the electronic device 300 via an adhesive layer to achieve under-display ultrasonic fingerprint recognition. It should be understood that in optional embodiments where the ultrasonic fingerprint module 200 is a rear-mounted or side-mounted ultrasonic fingerprint module of the electronic device 300, the bonding can also be achieved via an adhesive layer.

[0207] It should be understood that the above are merely illustrative applications and are not intended to limit the embodiments of this application.

[0208] It is understood that the above descriptions of various aspects of the embodiments of this application are merely optional exemplary descriptions of the technical solutions of the embodiments of this application, and are not intended to limit the embodiments of this application in any way.

[0209] The optional implementation of the embodiments of the present application is described in detail above in combination with the 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 drawings of the embodiments of the present application are not necessarily drawn according to the actual proportion, which are only used for facilitating the explanation of the technical solutions and do not limit the embodiments of the present application in any way. Within the technical concept of the embodiments of the present application, the technical solutions of the embodiments of the present application can be modified in various simple ways. The various technical features included in each of the different embodiments of the present application can be disassembled and / or combined in any suitable way. In order to avoid unnecessary repetition, the various possible combinations are not described again in the embodiments of the present application. However, these simple modifications and combinations should also be regarded as the disclosure of the present application and fall within the protection scope of the embodiments of the present application.

[0210] The term "comprising" and its variants, as used herein, are open-ended, and mean "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 additional embodiment". The term "some embodiments" means "at least some embodiments". It should be noted that the concepts mentioned in the present application are merely used to distinguish different devices, modules or units, and are not intended to limit the functions performed by these devices, modules or units or the sequence or interdependence of these functions. It should be noted that the terms "one", "multiple" mentioned in the present application are illustrative and not limiting, and those skilled in the art should understand that, unless otherwise explicitly stated in the context, it should be understood as "one or more".

[0211] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An ultrasonic transducer, characterized in that, include: Substrate, bottom electrode, piezoelectric layer, top electrode, and excitation 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 excitation electrode is located on the upper surface of the substrate and there is a gap between it and the bottom electrode. The piezoelectric layer is provided with an opening, and the top electrode is electrically connected to the excitation electrode through the opening. The excitation electrode is used to receive the excitation signal and apply the excitation signal to the top electrode to form an electric field between the top electrode and the bottom electrode, so as to excite the piezoelectric layer to emit an ultrasonic signal. The bottom electrode is used to receive the ultrasonic detection signal generated between the top electrode and the bottom electrode when the returned ultrasonic signal acts on the piezoelectric layer.

2. The ultrasonic transducer according to claim 1, characterized in that, The piezoelectric layer partially covers the excitation electrode and exposes a portion of the excitation electrode to the opening, so that the top electrode forms an electrical connection with the excitation electrode through the opening; the minimum distance between the edge of the excitation electrode and the inner wall of the opening is greater than or equal to 10 μm.

3. The ultrasonic transducer according to claim 1, characterized in that, The entire excitation electrode is located within the opening, so that the top electrode forms an electrical connection with the excitation electrode through the opening.

4. The ultrasonic transducer according to claim 3, characterized in that, The area of ​​the first vertical projection of the excitation electrode toward the substrate is equal to the area of ​​the first side of the opening, wherein the first side of the opening is the side of the opening that is close to the substrate along the thickness direction of the piezoelectric layer.

5. The ultrasonic transducer according to any one of claims 2-4, characterized in that, The first vertical projection of the excitation electrode toward the substrate is located within the outer contour of the second vertical projection of the piezoelectric layer toward the substrate; And / or, The first vertical projection of the excitation electrode toward the substrate is located within the third vertical projection of the top electrode toward the substrate.

6. The ultrasonic transducer according to any one of claims 1-4, characterized in that, The third vertical projection of the top electrode toward the substrate is located within the outer contour of the second vertical projection of the piezoelectric layer toward the substrate; or, The third vertical projection of the top electrode toward the substrate partially overlaps with the outer contour of the second vertical projection of the piezoelectric layer toward the substrate.

7. The ultrasonic transducer according to any one of claims 1-4, characterized in that, The opening includes at least one opening, wherein, At least one of the openings is located inside the piezoelectric layer and is spaced from the sidewall of the piezoelectric layer.

8. The ultrasonic transducer according to claim 7, characterized in that, The opening includes multiple openings, and the top electrode is electrically connected to the excitation electrode through the multiple openings.

9. The ultrasonic transducer according to claim 7, characterized in that, The minimum circumscribed circle diameter of at least one of the openings on the first side is greater than or equal to 20 μm, wherein the first side of the opening is the side of the opening that is close to the substrate along the thickness direction of the piezoelectric layer.

10. The ultrasonic transducer according to claim 9, characterized in that, The minimum circumscribed circle diameter ranges from 20µm to 30µm.

11. The ultrasonic transducer according to claim 7, characterized in that, The opening includes a first side and a second side; the first side of the opening is the side of the opening closer to the substrate along the thickness direction of the piezoelectric layer; the second side of the opening is the side of the opening farther from the substrate along the thickness direction of the piezoelectric layer; wherein, The area of ​​the second side of at least one of the openings is equal to the area of ​​the first side of the opening; or, The area of ​​the second side of at least one of the openings is greater than the area of ​​the first side of the opening.

12. The ultrasonic transducer according to claim 7, characterized in that, The axis of the opening is perpendicular to the substrate; the depth of the opening is less than the thickness of the piezoelectric layer; the shape of the target cross-section of the opening includes at least one of a circle, an ellipse, an octagon, and a quadrilateral, wherein the target cross-section is a cross-section of the opening parallel to the substrate; At least one of the openings satisfies one of the following conditions: At least one inner wall surface of the opening is perpendicular to the substrate; At least one inner wall surface of the opening has an inclined angle with the substrate, such that the area of ​​the opening on the side away from the substrate along the thickness direction of the piezoelectric layer is greater than the area of ​​the opening on the side closer to the substrate along the thickness direction of the piezoelectric layer.

13. The ultrasonic transducer according to any one of claims 1-4, characterized in that, The ultrasonic transducer further includes a seed metal layer, which is located between the piezoelectric layer and the top electrode, and the thickness of the seed metal layer is less than the thickness of the top electrode. Within the opening, the top electrode is electrically connected to the excitation electrode through a portion of the seed metal layer, and the top electrode is an electroplated metal layer.

14. A method for manufacturing an ultrasonic transducer, characterized in that, include: A bottom electrode and an excitation electrode are formed on the upper surface of a substrate, wherein there is a gap between the excitation electrode and the bottom electrode; A piezoelectric layer is formed above the substrate, covering the bottom electrode and at least partially covering the excitation electrode, and an opening is formed in the piezoelectric layer to expose at least a portion of the excitation electrode. A top electrode is formed above the piezoelectric layer, and the top electrode is electrically connected to the excitation electrode through the opening to prepare the ultrasonic transducer.

15. The method according to claim 14, characterized in that, The step of forming a top electrode above the piezoelectric layer and electrically connecting the top electrode to the excitation electrode through the opening includes: A seed metal layer is formed on the upper surface of the piezoelectric layer, and the seed metal layer covers the exposed excitation electrode through the opening; A barrier structure is formed above the substrate, and the barrier structure forms a receiving space above the piezoelectric layer for fabricating the top electrode; The seed metal layer is energized, and the seed metal layer in at least the accommodating space is electroplated to obtain the top electrode, so that the top electrode forms an electrical connection with the excitation electrode through the seed metal layer in the opening.

16. The method according to claim 15, characterized in that, The step of forming a containment structure above the substrate, thereby creating a space above the piezoelectric layer for fabricating a top electrode, includes: A photoresist layer is disposed on the substrate, and the photoresist layer is patterned and cured to form the enclosure structure; The step of patterning and curing the photoresist layer includes: patterning the photoresist layer to form a receiving space for fabricating the top electrode, and then curing it.

17. The method according to claim 14, characterized in that, The step of forming a top electrode above the piezoelectric layer and electrically connecting the top electrode to the excitation electrode through the opening includes: A top electrode paste is disposed above the piezoelectric layer, allowing the top electrode paste to enter the opening and contact the excitation electrode. After the top electrode paste is cured, the top electrode is formed, so that the top electrode forms an electrical connection with the excitation electrode through the opening.

18. An ultrasonic fingerprint module, comprising: The ultrasonic transducer as described in any one of claims 1-13.

19. An electronic device comprising: The ultrasonic fingerprint module, screen, back panel, and side frame as described in claim 18, wherein the ultrasonic fingerprint module is attached to the lower surface of the screen, the inner side of the back panel, or the inner side of the side frame.

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