Ultrasonic transducer, ultrasonic fingerprint module and electronic device

Abstract

Embodiments of the present application provide an ultrasonic transducer, an ultrasonic fingerprint module and an electronic device. 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 and has a spacing from 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 ultrasonic transducer in the present scheme has good performance.

Description

Technical Field

[0001] This application relates to the field of ultrasonic transducer technology, and more particularly to an ultrasonic transducer, an ultrasonic fingerprint module, and an electronic device. Background Technology

[0002] Ultrasonic transducers utilize the mechatronic-electroelectric conversion properties of piezoelectric materials. On one hand, they can be excited by a voltage output from a driving circuit to emit ultrasonic signals; on the other hand, they convert reflected ultrasonic signals back into electrical signals, thereby acquiring information about the external sensing surface. They can be widely used in fields including, but not limited to, biometric identification (for example, an example application could be an ultrasonic fingerprint module that can acquire fingerprint images for fingerprint recognition). However, existing ultrasonic transducers suffer from performance issues; therefore, it is necessary to provide new technical solutions to improve their performance. Utility Model Content

[0003] This application provides an ultrasonic transducer, an ultrasonic fingerprint module, and an electronic device.

[0004] According to a first aspect of the embodiments of this 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 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 has 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.

[0005] According to a second aspect of the embodiments of this application, an ultrasonic fingerprint module is provided, comprising: the ultrasonic transducer provided in the first aspect, wherein the excitation electrode is used to receive an excitation signal and apply the excitation signal to the top electrode 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 the ultrasonic detection signal generated between the top electrode and the bottom electrode when the returned ultrasonic signal acts on the piezoelectric layer for fingerprint recognition.

[0006] According to a third aspect of the embodiments of this application, an electronic device is provided, including an ultrasonic fingerprint module, a screen, a back panel, and a side frame provided in the second aspect above, wherein the ultrasonic fingerprint module is attached to the lower surface of the screen, or to the inner side of the back panel, or to the inner side of the side frame.

[0007] Based on this, the ultrasonic transducer in this application, on the one hand, through the design of the opening of the piezoelectric layer, allows the top electrode to form an electrical connection with the excitation electrode through the opening of the piezoelectric layer, thereby realizing 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, the top electrode does not need to be connected to the excitation electrode through a "top electrode tail" as in related technologies. Therefore, when designing the piezoelectric layer and the excitation electrode, it is not necessary to restrict "the excitation electrode to be partially exposed" or "the excitation electrode cannot be completely covered by the piezoelectric layer." Consequently, in the technical solution of this application, the piezoelectric layer can extend beyond the location of the excitation electrode, thus eliminating many of the limitations in related technologies. The limitations allow for more flexible fabrication methods for ultrasonic transducers. Furthermore, by removing these limitations, the piezoelectric layer of the ultrasonic transducer can be further expanded relative to the effective working area (i.e., the AA region) (for example, it can be expanded beyond the excitation electrode). The top electrode can also be expanded along with the piezoelectric layer. This allows the ultrasonic reflection interface of the piezoelectric layer and the top electrode 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, enhancing the response consistency of the ultrasonic transducer, and resulting in higher image flatness of the image obtained by the ultrasonic transducer. This effectively improves the performance of the ultrasonic transducer. Attached Figure Description

[0008] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0009] Figure 1A A schematic diagram of an ultrasonic transducer in the related art is shown.

[0010] Figure 1B It shows Figure 1A A top-view planar schematic diagram of an ultrasonic transducer in related technologies.

[0011] Figure 2A A schematic diagram of an example ultrasonic transducer of this application is shown.

[0012] Figure 2B It shows Figure 2A The example ultrasonic transducer is shown in plan view from a top angle.

[0013] Figure 3A A schematic diagram of another example of an ultrasonic transducer in this application is shown.

[0014] Figure 3B It shows Figure 3A The example ultrasonic transducer is shown in plan view from a top angle.

[0015] Figure 3C A schematic diagram of another example of an ultrasonic transducer in this application is shown.

[0016] Figure 3D It shows Figure 3C The example ultrasonic transducer is shown in plan view from a top angle.

[0017] Figure 4 A flowchart illustrating a method for fabricating an example ultrasonic transducer according to this application is shown.

[0018] Figure 5 A flowchart illustrating one alternative method for forming the top electrode in this application is shown.

[0019] Figure 6A The preparation method in this application is shown. Figure 2A A schematic diagram illustrating the fabrication process of an example ultrasonic transducer.

[0020] Figure 6B The preparation method in this application is shown. Figure 3A A schematic diagram illustrating the fabrication process of an example ultrasonic transducer.

[0021] Figure 7 A schematic block diagram of an example ultrasonic fingerprint module of this application is shown.

[0022] Figure 8A A schematic block diagram of an example electronic device according to this application is shown.

[0023] Figure 8B A schematic block diagram of another example of an electronic device in this application is shown.

[0024] Figure 9 A schematic diagram of an example ultrasonic transducer attached to the underside of an electronic device screen is shown.

[0025] Explanation of reference numerals in the attached figures: 100, Ultrasonic transducer; 10, Substrate; 20, Bottom electrode; 30, Piezoelectric layer; 31, Opening; 311, Opening; 40, Top electrode; 50, Seed metal layer; 60, Excitation electrode; 70, Protective layer; 80, Enclosure structure; 81, Accommodation space; 90, Pad area; 91, Pad; 200, Ultrasonic fingerprint module; 300, Electronic device; 310, Adhesive layer; 320, Screen. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0027] Applying ultrasonic transducers to ultrasonic fingerprint modules, placed in specific areas of the screens of electronic devices including but not limited to smartphones, allows for fingerprint recognition. It acquires information about the peaks and troughs of the fingerprint, and by analyzing the differences in the strength of the reflected ultrasonic signals corresponding to the peaks and troughs, it processes the signals to obtain a fingerprint image, thus achieving user authentication. Fingerprint recognition systems based on ultrasonic transducer sensing technology have the advantage of being relatively insensitive to interference from wet, dry, or dirty fingers, and can penetrate thick glass screens and other materials, such as screen protectors. Therefore, ultrasonic transducers provide more design freedom for electronic devices and can enhance the product's anti-interference capabilities and security. Some example ultrasonic transducer structures include circuitry for emitting ultrasonic excitation signals and processing ultrasonic echo signals, as well as a piezoelectric material layer with a high voltage coefficient, typically consisting of a bottom electrode, a piezoelectric layer, and a top electrode. However, existing ultrasonic transducers suffer from performance issues; therefore, it is necessary to provide new technical solutions to improve their performance.

[0028] For example, Figure 1A Schematic diagrams of some types of ultrasonic transducers in related technologies are shown. Figure 1B It shows Figure 1A A plan view of the ultrasonic transducer 100' in the relevant technology. (See diagram below.) Figure 1A and Figure 1B As shown, 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'. Figure 1A and Figure 1B As shown, the coverage area of ​​the piezoelectric layer 30' avoids the area where the pad area 90' is located. Furthermore, a portion of the edge of the piezoelectric layer 30' is designed not to extend beyond the excitation electrode 60', allowing the excitation electrode 60' to be partially or completely exposed by the piezoelectric layer 30'. The top electrode 40' of the ultrasonic transducer 100' may include a top electrode body 41' and a top electrode tail 42' (the boundary between these two is exemplarily shown as a dashed line). The top electrode tail 42' extends beyond the edge of the piezoelectric layer 30' and is electrically connected to the excitation electrode 60'. Figure 1A and Figure 1BIt is evident that a portion of the top electrode tail 42' extending beyond the piezoelectric layer 30' protrudes from the top electrode body 41' and connects to the excitation electrode 60'. This protruding shape leads to at least the following drawbacks: the design of the top electrode tail 42' in related technologies restricts the excitation electrode 60' to be partially exposed and not completely covered by the piezoelectric layer 30'. This prevents a portion of the piezoelectric layer 30' from extending beyond the location of the excitation electrode 60', directly limiting the outward expansion distance of the piezoelectric layer 30' relative to the effective working area (Active Area, i.e., AA area) of the ultrasonic transducer 100'. Consequently, the ultrasonic reflection interface cannot move as far away from the AA area boundary as possible, resulting in stronger noise and interference. This directly affects the performance of the ultrasonic transducer 100' (e.g., easily reduced signal-to-noise ratio, low response consistency, poor image flatness), leading to poor performance of the ultrasonic transducer 100'.

[0029] Therefore, ultrasonic transducers in related technologies suffer from poor performance and other problems, making it necessary to provide some new technical solutions to improve the performance of ultrasonic transducers.

[0030] It should be understood that the embodiments of this application provide some technical solutions that differ from related technologies, which can avoid the above-mentioned... Figure 1A and Figure 1B This addresses at least some of the defects present in the ultrasonic transducer, thereby effectively improving its performance.

[0031] The specific implementation of the technical solutions of the embodiments of this application is described below with reference to the accompanying drawings. It should be noted that, for ease of illustration, the structures in the various drawings are not necessarily drawn to scale. The various drawings are not intended to limit the embodiments of this application.

[0032] Reference Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3DAs shown, according to a first aspect of the embodiments of this application, an ultrasonic transducer 100 is provided, comprising: 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 the upper surface of the substrate 10, the piezoelectric layer 30 is located above the substrate 10 and covers the bottom electrode 20, and at least a portion of the top electrode 40 is located above the piezoelectric layer 30; the excitation electrode 60 is located on the upper surface of the substrate 10 and has a gap between it and the bottom electrode 20, the piezoelectric layer 30 is provided with an opening 31, and the top electrode 40 is electrically connected to the excitation electrode 60 through the opening 31. Optionally, the excitation electrode 60 can be used to receive an excitation signal and apply the excitation signal to the top electrode 40, so that an electric field is formed 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 used to receive the 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.

[0033] Based on this, the ultrasonic transducer 100 in this application, on the one hand, through the design of the opening 31 of the piezoelectric layer 30, allows the top electrode 40 to form an electrical connection with the excitation electrode 60 through the opening 31 of the piezoelectric layer 30, so as to realize the function of the ultrasonic transducer 100; for example, the top electrode 40 can be subjected to an excitation signal by the excitation electrode 60, so that 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 ultrasonic signals, and the bottom electrode 20 can also effectively receive the 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 31, the top electrode 40 does not need to be connected through a "top electrode tail" (such as in related technologies) Figure 1A and Figure 1B(As shown in the example) connected to the excitation electrode 60, therefore, when designing the piezoelectric layer 30 and the excitation electrode 60, it is not necessary to restrict "the excitation electrode must be partially exposed" or "the excitation electrode cannot be completely covered by the piezoelectric layer". Consequently, in the technical solution of this application, the piezoelectric layer 30 can extend beyond the location of the excitation electrode 60, thus eliminating many restrictions in related technologies. This allows for more flexible fabrication methods for the ultrasonic transducer 100. Furthermore, due to the elimination of these restrictions in related technologies, the piezoelectric layer 30 of the ultrasonic transducer 100 is relatively effective. The working area (i.e., the AA area) can be further expanded (for example, it can be expanded beyond the excitation electrode 60), and the top electrode 40 can also be expanded 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 area, 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.

[0034] It should be understood that the ultrasonic transducer 100 in this embodiment has good performance and therefore good application value. For example, if the ultrasonic transducer 100 in this embodiment is applied to an ultrasonic fingerprint module, it can reduce noise and interference, thereby reducing the adverse effects of noise and interference on the image quality of the ultrasonic fingerprint image, and thus effectively improving the accuracy of fingerprint recognition. This enhances the user experience of the fingerprint recognition function and has good application value.

[0035] Optionally, in this application, the substrate 10 can be a silicon-based substrate or a TFT (Thin Film Transistor) substrate. Other types of substrates may also be used depending on the requirements.

[0036] Optionally, the piezoelectric layer 30 may comprise any piezoelectric material. For example, it may comprise at least one of PVDF (polyvinylidene difluoride), lead zirconate titanate, and lithium niobate. The PVDF material may comprise PVDF, PVDF copolymers, etc.

[0037] Optionally, the opening 31 provided on the piezoelectric layer 30 can penetrate the piezoelectric layer 30, thereby exposing the excitation electrode 60 to form an electrical connection with the top electrode 40. Optionally, the opening 31 can be formed by patterning on the piezoelectric layer 30 in any way during the fabrication of the piezoelectric layer 30.

[0038] For example, in some alternative embodiments, refer 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] Based on this, such an optional structure allows the piezoelectric layer 30 to extend beyond 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 improving the image flatness of the image obtained by the ultrasonic transducer 100, thus effectively improving the performance of the ultrasonic transducer 100.

[0043] In some alternative embodiments, refer to Figure 3C and Figure 3D As shown, the entire excitation electrode 60 is located inside the opening 31, so that the top electrode 40 is electrically connected to the excitation electrode 60 through the opening 31.

[0044] Based on this, in this optional implementation, the piezoelectric layer 30 may not cover the excitation electrode 60, meaning the excitation electrode 60 can be directly and entirely located within the opening 31. The top electrode 40 can then effectively form an electrical connection with the excitation electrode 60 through the opening 31. Since the excitation electrode 60 can be electrically connected to the top electrode 40 over a larger area, the stability of the electrical connection is also better. The larger opening 31 is also easier to fabricate. Furthermore, this structure allows the piezoelectric layer 30 to extend beyond the excitation electrode 60, and the top electrode 40 can also extend outwards 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, and enhancing the response consistency of the ultrasonic transducer 100. The image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thus effectively improving the performance of the ultrasonic transducer 100.

[0045] For example, if the opening 31 includes an opening 311 that is the same size as or larger than the excitation electrode 60 (as can be understood below), then the excitation electrode 60 can be entirely located within the opening 31.

[0046] In some alternative embodiments, refer to Figure 3C and Figure 3D As shown, the area of ​​the first vertical projection of the excitation electrode 60 toward the substrate 10 is equal to the area of ​​the first side of the opening 31, wherein the first side of the opening 31 is the side of the opening 31 that is close to the substrate 10 along the thickness direction of the piezoelectric layer 30.

[0047] Based on this, with such an optional structure, the excitation electrode 60 can be located entirely within the opening 31, so that the top electrode 40 can effectively form an electrical connection with the excitation electrode 60 through the opening 31. The electrical connection has good stability and is easier to process. Furthermore, when the top electrode 40 is connected to the excitation electrode 60 through the opening 31, the part of the top electrode 40 located within the opening 31 can be prevented from contacting the substrate 10, thereby avoiding short circuits or discharge breakdowns in this area, which is beneficial to improving the performance of the ultrasonic transducer 100.

[0048] In some alternative embodiments, the area of ​​the excitation electrode 60 projected vertically toward the substrate 10 is smaller than the area of ​​the first side of the opening 31. Optionally, based on this, no other circuit structures other than the excitation electrode 60 are provided on the upper surface of the substrate 10 located within the opening 31.

[0049] Therefore, with this optional structure, the excitation electrode 60 can be located entirely within the opening 31, so that the top electrode 40 can effectively form an electrical connection with the excitation electrode 60 through the opening 31. The electrical connection has good stability and is easier to process. Furthermore, since no other circuit structures other than the excitation electrode 60 are provided on the upper surface of the substrate 10 located within the opening 31, the risk of short circuit or discharge breakdown in the area of ​​the top electrode 40 within the opening 31 is reduced when it comes into contact with the substrate 10.

[0050] 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 outer contour of the second vertical projection of the piezoelectric layer 30 toward the substrate 10.

[0051] Based on this, such an optional 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 improving the image flatness of the image obtained by the ultrasonic transducer 100, thus effectively improving the performance of the ultrasonic transducer 100.

[0052] 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, 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] It should be noted that, as Figure 1A and Figure 1BThe example of the ultrasonic transducer 100' shown in the related technology also has the following second defect: the design of the top electrode tail 42' in the related technology will form ultrasonic reflection points at the corners. For example, if the top electrode tail 42' is a protruding cube, ultrasonic reflection points can be formed at the four corners (such as the four 90° corners of a protruding cube). 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 effective working area (Active Area, i.e., AA area) of the ultrasonic transducer 100', the stronger the interference. In addition, even if the protruding top electrode tail 42' is designed to be a shape other than a protruding cube (such as a semi-circle), reflection will inevitably form at the corner where the top electrode tail 42' and the top electrode body 41' meet. This will directly affect the performance of the ultrasonic transducer 100' (such as easily reducing the signal-to-noise ratio), resulting in poor performance of the ultrasonic transducer 100'.

[0057] In some alternative embodiments, combined with Figure 2A and Figure 2B Understandably, in the ultrasonic transducer 100 of this application embodiment, the third vertical projection of the top electrode 40 toward the substrate 10 can be located within the outer contour of the second vertical projection of the piezoelectric layer 30 toward the substrate 10.

[0058] like Figure 2A and Figure 2B As shown in the above optional embodiments of this application, the top electrode 40 has no "top electrode tail", that is, the top electrode 40 may not extend beyond the piezoelectric layer 30, and except for the part located inside the opening 31, the other parts are all located above the piezoelectric layer 30.

[0059] It should be understood that, in the above optional structure, the third vertical projection of the top electrode 40 toward the substrate 10 is located within the outer contour of the second vertical projection of the piezoelectric layer 30 toward the substrate 10, which eliminates the "top electrode tail" of the top electrode 40. This effectively reduces the corners or bends of the top electrode 40, thereby reducing the number of high-intensity ultrasonic reflection points. This effectively reduces the ultrasonic reflection echoes formed by the ultrasonic reflection points, thereby reducing this part of the noise and spurious signals. As a result, the signal-to-noise ratio of the ultrasonic transducer 100 can be improved, as can the response consistency of the ultrasonic transducer 100. Furthermore, the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, which can effectively improve the performance of the ultrasonic transducer 100.

[0060] In some alternative embodiments, combined with Figure 3A and Figure 3B , Figure 3C and Figure 3DIt is understood that the third vertical projection of the top electrode 40 toward the substrate 10 can partially overlap with the pattern enclosed by the outer contour of the second vertical projection of the piezoelectric layer 30 toward the substrate 10.

[0061] like Figure 3A and Figure 3B As shown in the above optional embodiments of this application, the top electrode 40 can extend beyond the piezoelectric layer 30, so that the pattern enclosed by the outer contours of the third vertical projection and the second vertical projection partially overlaps. This structure is easier to fabricate, reducing the manufacturing difficulty and process complexity of the ultrasonic transducer 100. Furthermore, the expansion of the top electrode 40 beyond the piezoelectric layer 30 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, and enhancing the response consistency of the ultrasonic transducer 100. The image flatness of the image obtained by the ultrasonic transducer 100 is also higher, thus effectively improving the performance of the ultrasonic transducer 100.

[0062] In this embodiment, the specific structure of the opening 31 is not limited. (Refer to...) Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D As shown, in some alternative embodiments, the opening 31 includes at least one opening 311, wherein the at least one opening 311 is located inside the piezoelectric layer 30 and is spaced from the sidewall of the piezoelectric layer 30.

[0063] It should be understood that at least one opening 311 of the opening 31 of the ultrasonic transducer 100 in this application is disposed inside the piezoelectric layer 30 and is spaced from the sidewall of the piezoelectric layer 30. This makes the sidewall morphology of the piezoelectric layer 30 more complete and flat, reduces the corners on the sidewall of the piezoelectric layer 30, thereby reducing 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 improving 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, thus improving the performance of the ultrasonic transducer 100.

[0064] For example, such as Figure 2A and Figure 2B , Figure 3A and Figure 3B For example, opening 31 may include two openings 311, while... Figure 3C and Figure 3D For example, opening 31 may include an opening 311.

[0065] In some alternative embodiments, refer 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.

[0066] 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.

[0067] The specific number of openings 311 is not limited in the embodiments of this application; 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Therefore, when the excitation electrode 60 protrudes from the upper surface of the substrate 10, the top electrode 40 can achieve electrical connection with the excitation electrode 60 through the opening 311 with a small depth. Furthermore, since the excitation electrode 60 can be exposed by opening the piezoelectric layer 30 with a small depth 311, it is convenient to connect with the top electrode 40, which is also convenient in terms of process.

[0072] In some alternative embodiments, the depth of at least one opening 311 may be equal to the thickness of the piezoelectric layer 30.

[0073] The specific shape of the opening 311 is not limited in the embodiments of this application. Any regular or irregular shape can be adopted as long as the requirements are met. For example, in some optional implementations, the shape of the target cross section of at least one opening 311 may 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.

[0074] It should be understood that the openings 311 of the above cross-sectional shapes can all ensure effective electrical connection between the top electrode 40 and the excitation electrode 60 through the openings 311. In addition, compared with the "top electrode tail" in related technologies, the use of some optional shapes of openings 311 makes the reflected echo of the ultrasonic signal smaller for the inner wall of the opening of the piezoelectric layer 30 and the part of the top electrode 40 located in the opening 311 in this embodiment, 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, thereby effectively improving the performance of the ultrasonic transducer 100.

[0075] It should be noted that, as Figure 1A and Figure 1B The example of the ultrasonic transducer 100' shown in the related technology also has the aforementioned second part of the defect (refer to the above description). However, some optional embodiments in this application use an opening 311 with a circular or elliptical cross section, so that 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 can also be circular or elliptical, with fewer corners or bends. Therefore, it reduces the number of ultrasonic reflection points with high intensity, which can effectively reduce the ultrasonic reflection echo formed by the ultrasonic reflection points, thereby reducing this part of the noise and spurious sound. Thus, it can improve the signal-to-noise ratio of the ultrasonic transducer 100 and improve the response consistency of the ultrasonic transducer 100. Moreover, the image flatness of the image obtained by the ultrasonic transducer 100 is also higher, which can effectively improve the performance of the ultrasonic transducer 100.

[0076] Optionally, when the opening 311 is octagonal, it is preferably a regular octagon, or other irregular octagons may be used. Optionally, when the opening 311 is quadrilateral, it is preferably a rectangle including squares, or other irregular quadrilaterals may be used.

[0077] In this embodiment, the specific size of the opening 311 is not limited. For example, optionally, the minimum circumscribed circle diameter of at least one first side of the opening 311 can be greater than or equal to 20 μm, wherein the first side of the opening 311 is the side of the opening 311 closest to the substrate 10 along the thickness direction of the piezoelectric layer 30. Optionally, along the axial direction of the opening 311, the minimum circumscribed circle diameter at each point of the opening 311 is greater than or equal to 20 μm. For example, if the first side of the opening 311 is circular, then the minimum circumscribed circle diameter of the first side of the opening 311 can be equal to the diameter of the circle; if the first side of the opening 311 is elliptical, then the minimum circumscribed circle diameter of the first side of the opening 311 can be equal to the major axis of the ellipse; if the first side of the opening 311 is rectangular (including square), then the minimum circumscribed circle diameter of the first side of the opening 311 can be equal to the diagonal length of the rectangle.

[0078] It should be understood that, on the one hand, an opening 311 of this size is easy to manufacture and can effectively meet the requirement of a 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 related technologies, using an opening 311 of this size makes the inner wall of the opening of the piezoelectric layer 30 in this embodiment, as well as the part of the top electrode 40 located in the opening 311, smaller for the reflected 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.

[0079] For example, the minimum circumscribed circle diameter of the first side of the opening 311 can be in the range of 20µm to 30µm. The preferred range of 20µm to 30µm makes the opening 311 easy to manufacture and effectively meets the requirement of a stable electrical connection between the top electrode 40 and the excitation electrode 60 through the opening 311. On the other hand, it also prevents the opening 311 from being too large, resulting in a smaller reflected echo of the ultrasonic signal, which helps to ensure the performance of the ultrasonic transducer 100.

[0080] You can choose the appropriate size as needed. For example, you can choose sizes including 20um, 21um, 22um, 23um, 24um, 25um, 26um, 27um, 28um, 29um, 30um, etc.

[0081] Of course, if the requirements can be met, the minimum circumscribed circle diameter of the first side of the opening 311 can also be greater than 30 μm. There is no unique limitation in this embodiment of the application.

[0082] In this embodiment of the application, the opening 311 may include a first side and a second side. The first side of the opening 311 is the side of the opening 311 closest 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 furthest from the substrate 10 along the thickness direction of the piezoelectric layer 30.

[0083] In some alternative 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 electrical connection between the top electrode 40 and the excitation electrode 60.

[0084] Optionally, the cross-sections of the opening 311 parallel to the substrate 10 along the direction from away from the substrate 10 to near the substrate 10 can have the same shape and area.

[0085] In some alternative embodiments, the area of ​​the second side of at least one opening 311 is larger than the area of ​​the first side of the opening 311. Using such an opening 311 can improve the fabrication flexibility of the ultrasonic transducer 100 while reducing manufacturing difficulty, provided the requirements are met.

[0086] Optionally, along the direction from away from substrate 10 to near substrate 10, the cross-sections of opening 311 parallel to substrate 10 can have the same shape and gradually increase in area. For example, the area of ​​some openings 311 on the second side away from substrate 10 can be larger than the area of ​​openings 311 on the first side near substrate 10. For example, the interior of opening 311 can be in the shape of an inverted frustum, an inverted trapezoid, or a funnel, then the area of ​​the cross-sections of opening 311 parallel to substrate 10 along the direction from away from substrate 10 to near substrate 10 can vary gradually.

[0087] It should be understood that, under certain process characteristics, it is relatively difficult to fabricate an opening 311 with the same area on both the first and second sides. Furthermore, not only is the fabrication process more difficult, but the stress on the top electrode 40 portion within such an opening 311 is also greater, making it prone to cracking during reliability testing. In some optional embodiments of this application, the opening 311 can be fabricated as an opening that is larger at the top and smaller at the bottom (i.e., the area on the second side is larger than the area on the first side), such as an inverted frustum, an inverted trapezoid, or a funnel shape. This allows the technical solution of this application to adapt to the characteristics of these processes, thereby effectively reducing the manufacturing difficulty of the ultrasonic transducer 100, reducing process complexity, reducing stress impact, and reducing the risk of cracking of the top electrode 40 during reliability testing. In some optional embodiments, the axis of at least one opening 311 is perpendicular to the substrate 10. Such an opening 311 is easier to fabricate (e.g., it can be easily obtained through patterning when preparing the piezoelectric layer 30), therefore, using such an opening 311 can reduce the manufacturing difficulty and process complexity of the ultrasonic transducer 100.

[0088] It should be noted that, except for vertical projection, the verticality mentioned elsewhere in this application can be taken as 90°±5°, and can be considered vertical within this range.

[0089] In some alternative embodiments, at least one inner wall surface of at least one opening 311 is perpendicular to the substrate 10. Such an opening 311 is easier to fabricate (e.g., it can be easily obtained through patterning during the fabrication of the piezoelectric layer 30), thus employing such an opening 311 can reduce the manufacturing difficulty and process complexity of the ultrasonic transducer 100. For example, referring to… Figure 2A and Figure 2B , Figure 3A and Figure 3B As shown, the target cross-sections of the openings 311 are all circular, the axes of the openings 311 are all perpendicular to the substrate 10, and the inner wall surface of the opening 311 is a cylindrical surface, which is perpendicular to the substrate 10. For example, if the target cross-section of the opening 311 includes, but is not limited to, a square or rectangular shape (such as...) Figure 3C and Figure 3D As shown), the opening 311 can have 4 inner wall surfaces. If the axis of the opening 311 is perpendicular to the substrate 10, then the 4 inner wall surfaces can be perpendicular to the substrate 10.

[0090] In some optional embodiments, at least one inner wall of at least one opening 311 has an inclined angle with the substrate 10. This allows the area of ​​the opening 311 on the side away from the substrate 10 along the thickness direction of the piezoelectric layer 30 (i.e., the second side of the opening 311) to be larger than the area of ​​the opening 311 on the side closer to the substrate 10 along the thickness direction of the piezoelectric layer 30 (i.e., the first side of the opening 311). Using such an opening 311 can improve the fabrication flexibility of the ultrasonic transducer 100 and reduce manufacturing difficulty while meeting requirements. For example, if the interior of the opening 311 is an inverted frustum shape, then the inner wall surface of the opening 311 is an inverted frustum surface, which has an inclined angle with the substrate 10. As another example, if the interior of the opening 311 is an inverted trapezoidal frustum shape, then the opening 311 can have four inner wall surfaces, and all four inner wall surfaces can have inclined angles with the substrate 10.

[0091] Optionally, the top electrode 40 can be used to apply an excitation signal, thereby creating an electric field between the top electrode 40 and the bottom electrode 20 (i.e., a voltage difference across the piezoelectric layer 30 in the thickness direction), which excites the piezoelectric layer 30 to emit ultrasonic signals. The bottom electrode 20 can be used to receive the 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 can be used to generate an image. Specifically, after the top electrode 40 is excited by an excitation signal, an electric field can be formed between it and the bottom electrode 20, creating a voltage difference across the piezoelectric layer 30 in the thickness direction, thereby exciting the piezoelectric layer 30 to vibrate and emit ultrasonic signals. In this process, the piezoelectric layer 30 converts the electrical signal into an ultrasonic signal (i.e., mechanical vibration) based on the piezoelectric effect. The bottom electrode 20 can receive the ultrasonic detection signal (electrical signal) obtained by the ultrasonic signal converted and returned by the piezoelectric layer 30, which can be used to generate an image. Optionally, when the ultrasonic transducer 100 is used in an ultrasonic fingerprint module, the ultrasonic detection signal can be used to acquire a fingerprint image of the finger.

[0092] It should be noted that, for the ultrasonic transducer 100, if the fourth vertical projection of the bottom electrode 20 toward the substrate 10 is located within the vertical projection of the piezoelectric layer 30 toward the substrate 10 (i.e., the second vertical projection) and also within the vertical projection of the top electrode 40 toward 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 where the smallest outer rectangle of the fourth vertical projection is located.

[0093] In some optional embodiments, the angle between at least one outer wall of the top electrode 40 and the normal to the substrate 10 is less than or equal to 45°. The normal to the substrate 10 can be a straight line perpendicular to the upper surface of the substrate 10. This optional structure results in less diffraction echo of the ultrasonic signal due to the boundary morphology of the top electrode 40, thereby better reducing interference to the ultrasonic transducer 100 during use and improving the performance of the ultrasonic transducer 100. Furthermore, the aforementioned angle range has lower requirements for the fabrication process, making it easier to form the top electrode 40, thus reducing the fabrication difficulty of the ultrasonic transducer.

[0094] Preferably, in this embodiment, the angle between at least one outer wall of the top electrode 40 and the normal of the substrate 10 is less than or equal to 5°. In this case, it can be considered that at least one outer wall of the top electrode 40 is perpendicular to the substrate 10. This optional structure makes the diffraction echo of the ultrasonic signal caused by the boundary morphology of the top electrode 40 smaller, thereby reducing the interference to the ultrasonic transducer 100 during use and improving the performance of the ultrasonic transducer 100.

[0095] Preferably, in this embodiment, the angle between each outer wall of the top electrode 40 and the normal to the substrate 10 is less than or equal to 5°. In this case, it can be considered that each outer wall of the top electrode 40 is perpendicular to the substrate 10. This optional structure results in smaller diffraction echoes of the ultrasonic signal due to the boundary morphology of the top electrode 40, thereby better reducing the interference to the ultrasonic transducer 100 during use and improving the performance of the ultrasonic transducer 100.

[0096] Preferably, the angle between at least one outer wall of the top electrode 40 and the normal of the substrate 10 is 0°.

[0097] Based on this, the angle between at least one outer wall of the top electrode 40 and the normal of the substrate 10 is equal to 0°. This optional structure makes the diffraction echo of the ultrasonic signal caused by the boundary morphology of the top electrode 40 smaller, thereby better reducing the interference to the ultrasonic transducer 100 during use and better improving the performance of the ultrasonic transducer 100.

[0098] Preferably, the angle between each outer wall of the top electrode 40 and the normal of the substrate 10 is 0°.

[0099] It should be understood that the closer the angle between each outer wall of the top electrode 40 and the normal of the substrate 10 is to 0°, the closer the outer wall is to the substrate 10, and the better the performance of the ultrasonic transducer 100.

[0100] In some alternative embodiments, the junction between the outer wall of the top electrode 40 and the upper surface of the top electrode 40 is arc-shaped.

[0101] Based on this, the arc-shaped design at the junction between the outer wall of the top electrode 40 and the upper surface of the top electrode 40 in this application makes the reflection performance of the ultrasonic signal at the junction between the outer wall of the top electrode 40 and the upper surface of the top electrode 40 more consistent, so that some places reflect too much and some places reflect too little, thereby improving the performance of the ultrasonic transducer 100.

[0102] In some alternative embodiments, such as Figure 2A and Figure 2B , Figure 3A and Figure 3B , Figure 3C and Figure 3D As shown, at least one sidewall of the top electrode 40 does not extend beyond the edge of the piezoelectric layer 30. Wherein, as... Figure 2A and Figure 2B In the example shown, none of the sidewalls of the top electrode 40 extend beyond the edge of the piezoelectric layer 30; as Figure 3A and Figure 3B ,or Figure 3C and Figure 3D In the example shown, the multiple sidewalls of the top electrode 40 do not extend beyond the edge of the piezoelectric layer 30.

[0103] It should be understood that in this embodiment, at least one sidewall of the top electrode 40 does not extend beyond the edge of the piezoelectric layer 30, so that at least a portion of the top electrode 40 can pass through the blockage of the piezoelectric layer 30 without directly contacting the electrically sensitive area on the substrate 10, thus avoiding short circuits or discharge breakdowns, which is beneficial to improving the performance of the ultrasonic transducer 100.

[0104] The excitation electrode 60 can be used to receive excitation signals from an external circuit and apply excitation signals to the top electrode 40, which is electrically connected to the excitation electrode 60. Optionally, the excitation signal can be an alternating current signal or a pulse signal.

[0105] The excitation electrode 60 is located on the upper surface of the substrate 10 and is spaced apart from the bottom electrode 20 to prevent the top electrode 40 from forming an electrical connection with the bottom electrode 20 through the excitation electrode 60.

[0106] In some alternative embodiments, refer 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.

[0107] 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.

[0108] 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.

[0109] 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.

[0110] 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 3CThe 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 3D The middle part is omitted Figure 3C (Protective layer 70 in the diagram). It should be understood that the above schematic diagrams are not intended to limit the embodiments of this application.

[0111] In this application, the excitation electrode 60 is electrically connected to the pad area 90 and the top electrode 40 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 connected top electrode 40 through the excitation electrode 60, enabling the ultrasonic transducer 100 to perform the corresponding functions.

[0112] For example, a portion of the pads in the pad area 90 can be electrically connected to the excitation electrode 60, thereby enabling the pad area 90 to be electrically connected to the top electrode 40 through the excitation electrode 60.

[0113] Optionally, in addition to being connected to the excitation electrode 60, in some other optional embodiments, the top electrode 40 can also be directly connected to an external circuit, so that the top electrode 40 can also directly obtain an excitation signal from the external circuit. Appropriate methods can be selected as needed, and no limitations are imposed here.

[0114] In some alternative embodiments, refer to Figure 2A , Figure 3A , Figure 3C As shown, 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 a portion of the top electrode 40.

[0115] Based on this, at least a portion of the top electrode 40 can be protected by a protective layer 70 covering at least the upper surface of the top electrode 40, thereby ensuring the performance of the top electrode 40 and improving the performance of the ultrasonic transducer 100.

[0116] 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.

[0117] Optionally, refer to Figure 2A , Figure 3A , Figure 3CAs shown, the protective layer 70 completely covers the top electrode 40. Obviously, this provides more comprehensive protection for the top electrode 40, better guarantees its performance, improves the performance of the ultrasonic transducer 100, and ensures that the ultrasonic transducer 100 can operate normally and effectively for a long time.

[0118] Optionally, refer 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 provide more comprehensive protection for the top electrode 40 and the piezoelectric layer 30, better ensure the performance of the top electrode 40 and the piezoelectric layer 30, improve the performance of the ultrasonic transducer 100, and ensure that the ultrasonic transducer 100 can work normally and effectively for a long time.

[0119] It should be understood that the shape of the protective layer 70 can be arbitrarily set according to requirements. Figure 2A , Figure 3A , Figure 3C The illustrations show only some examples of the styles of the protective layer 70, some of which are substantially the same and some are different, but none of them are intended to limit the embodiments of this application.

[0120] Optionally, the protective layer 70 does not cover the pad area 90 to ensure that the pad area 90 can be exposed for subsequent electrical connection with external circuitry.

[0121] Optionally, the top electrode 40 in this 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 this application has a simple and easy-to-control manufacturing process, smaller thickness tolerance, and better quality stability, which can effectively improve the performance of the ultrasonic transducer. Compared with other types of top electrodes, its manufacturing process is less difficult and time-consuming, and it is less prone to production abnormalities, thus resulting in a higher product yield of the ultrasonic transducer.

[0122] Optionally, the junction between the outer wall of the top electrode 40 and the upper surface of the top electrode 40 is arc-shaped, which may be formed by electroplating. That is, the arc-shaped junction may be a special shape feature of the top electrode 40 in the form of an electroplated metal layer, which may have better advantages.

[0123] Optionally, the top electrode 40 may be an electroplated metal layer formed on the upper surface of the seed metal layer 50. In some optional embodiments, refer to... Figure 2AAs shown, the ultrasonic transducer 100 further includes a seed metal layer 50, which is located between the piezoelectric layer 30 and the top electrode 40. The thickness of the seed metal layer 50 is less than the thickness of the top electrode 40. Optionally, within the opening 31, the top electrode 40 is electrically connected to the excitation electrode 60 through a portion of the seed metal layer 50.

[0124] It should be understood that in this application, the seed metal layer 50 facilitates the formation of the top electrode 40 in the form of an electroplated metal layer, resulting in a top electrode 40 with better performance. Furthermore, the top electrode 40 and the excitation electrode 60 can be effectively electrically connected through the seed metal layer 50 located within the opening 31 of the piezoelectric layer 30, thereby improving the performance of the ultrasonic transducer 100. Moreover, the ultrasonic transducer 100 provided by this solution has a simple structure, thus its manufacturing process is simple and cost-effective.

[0125] The thickness of the seed metal layer 50 is not specifically limited in this application 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 μm. Such a thickness range of seed metal layer 50 is neither too thin nor too thick, and has good step coverage ability on the undulating terrain of the substrate, which can effectively meet the electroplating requirements and facilitate the performance of the top electrode 40 in the form of an electroplated metal layer.

[0126] This application does not specifically limit the type of metal material used for the seed metal layer 50. Any metal material can be used as needed.

[0127] Optionally, the seed metal layer 50 can be a single layer of metal. Alternatively, the seed metal layer 50 can also be a multi-layered metal. The setting can be chosen according to requirements, and no restrictions are imposed here.

[0128] In some alternative embodiments, the seed metal layer 50 employs a double-layer metal. Optionally, the seed metal layer 50 includes a first metal layer and a second metal layer, with the first metal layer located between the piezoelectric layer 30 and the second metal layer, and the second metal layer located between the first metal layer and the top electrode 40. Optionally, the resistivity of the first metal layer is higher than that of the second metal layer.

[0129] The first and second metal layers can be made of any feasible metal layers. For example, the first metal layer can be made of titanium, titanium-tungsten alloy, or chromium; that is, the first metal layer can be at least one of titanium, titanium-tungsten alloy, and chromium. For example, the second metal layer can be made of copper, gold, or nickel-vanadium alloy; that is, the second metal layer can be at least one of copper, gold, and nickel-vanadium alloy. When fabricating the seed metal layer 50, the first metal layer can be formed at least on the upper surface of the piezoelectric layer 30 first, and then the second metal layer can be formed on the first metal layer. When forming the top electrode 40, it can be formed on the second metal layer, such that 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.

[0130] In this application, the advantage of using a double-layer metal layer for the seed metal layer 50 is that, taking a titanium layer or a titanium-tungsten alloy layer as the first metal layer and a copper layer as the second metal layer, the second metal layer (e.g., a copper layer, a gold layer, or a nickel-vanadium alloy layer) has a lower resistivity and better conductivity. Therefore, the effect of forming the top electrode 40 in the form of an electroplated metal layer on the second metal layer is better, which is also beneficial to the stability of the electroplating process. The top electrode 40 in the form of an electroplated metal layer also has better performance. The first metal layer (e.g., a titanium layer, a titanium-tungsten alloy layer, or a chromium layer) can improve the interaction between the second metal layer and the pressure plate. The adhesion between the upper surface of the substrate 10, including the piezoelectric layer 30, can improve the quality of the seed metal layer 50 and act as a barrier layer to prevent the metal material of the second metal layer from diffusing downward into the lower material (e.g., the piezoelectric layer 30). The first metal layer can stably serve as the nucleus for the growth of the second metal layer, promoting the uniform deposition of the second metal layer and further improving the quality of the seed metal layer 50. Thus, the top electrode 40 in the form of an electroplated metal layer formed in the seed metal layer 50 has better performance, which can effectively improve the performance of the ultrasonic transducer 100.

[0131] Optionally, the thickness of the first metal layer is less than or equal to 1 μm, and the thickness of the second metal layer is less than 2 μm. This thickness range ensures that the first and second metal layers are neither too thin nor too thick, providing good step coverage on the undulating terrain of the substrate. This effectively meets the electroplating requirements and facilitates the performance of the top electrode 40 in the form of electroplated metal layers.

[0132] Optionally, the sum of the thicknesses of the first metal layer and the second metal layer can be less than or equal to 2 μm to meet the requirement that the thickness of the seed metal layer 50 in the aforementioned optional embodiment is less than 2 μm.

[0133] Optionally, the thickness of the first metal layer can be smaller than the thickness of the second metal layer. In this way, the first metal layer can meet the requirement of preventing the metal material of the second metal layer from diffusing downwards to the lower layer material, and the second metal layer can also meet the requirement of thickness uniformity when electroplating the top electrode 40.

[0134] 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.

[0135] 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.

[0136] This application also provides a method for fabricating an ultrasonic transducer, which can fabricate 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.

[0137] In this application, the bottom electrode 20 can be formed on the upper surface of the substrate 10 by any suitable method. For example, it can be achieved by methods including but not limited to deposition and etching.

[0138] In this application, the excitation electrode 60 can be formed on the upper surface of the substrate 10 by any suitable method. For example, it can be achieved by methods including but not limited to deposition and etching.

[0139] In some optional embodiments, the fabrication method further includes forming a pad region 90 on the upper surface of the substrate, wherein the pad region 90 is electrically connected to the excitation electrode 60 and the bottom electrode 20, respectively. The bottom electrode 20, the excitation electrode 60, and the pad region 90 have been described previously and can be understood by referring to the preceding text; they will not be repeated here.

[0140] S104: 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 part of the excitation electrode.

[0141] Optionally, the piezoelectric layer 30 may comprise any piezoelectric material. For example, it may comprise at least one of PVDF, lead zirconate titanate, and lithium niobate. The PVDF material may comprise PVDF, PVDF copolymers, etc. In this application, the piezoelectric layer 30 can be formed on the substrate 10 by any suitable method, without particular limitation. For example, it can be achieved by methods including but not limited to screen printing, coating, dry film lamination, etc., or by physical or chemical vapor deposition methods such as sputtering and evaporation.

[0142] Optionally, the piezoelectric layer 30 can be patterned to form an opening 31, through which at least a portion of the excitation electrode 60 is exposed. It should be understood that details regarding the piezoelectric layer 30 and the opening 31 have been described in detail in the preceding embodiment of the ultrasonic transducer 100, and can be understood by referring to the preceding text, and will not be repeated here.

[0143] The patterning method can be selected as needed. For example, in some embodiments, the piezoelectric layer 30 can be patterned by coating, exposure and development and dry etching, so that the piezoelectric layer 30 can form an opening 31 that exposes at least a portion of the excitation electrode 60.

[0144] For example, some optional implementation processes of step S104 can be understood with reference to the following description: First, a full-layer piezoelectric layer 30 is formed on the substrate 10. Then, a full-layer photoresist is formed on the piezoelectric layer 30 by a coating process (such as spin coating). By exposing and developing the photoresist, at least the photoresist covering the target portion of the piezoelectric layer 30 that needs to be removed to form the opening 31 is removed to expose the target portion, while the photoresist covering the other portions of the piezoelectric layer 30 that need to be retained is retained. Then, the target portion is removed by dry etching to form the opening 31. Finally, the remaining photoresist is removed, thereby realizing step S104. It is understood that the above implementation process is only an example process, and other optional methods can also be used to implement it. No unique limitation is made here.

[0145] S106: 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 an ultrasonic transducer.

[0146] An ultrasonic transducer 100 can be fabricated by forming a top electrode 40 above the piezoelectric layer 30 in any manner and making the top electrode 40 electrically connected to the excitation electrode 60 through the opening 31.

[0147] Based on this, the ultrasonic transducer 100 is fabricated using the optional fabrication method of steps S102 to S106 of this application. The top electrode 40 of the fabricated ultrasonic transducer 100 can be electrically connected to the excitation electrode 60 through the opening 31. This allows the top electrode 40 to avoid the need for a "top electrode tail" (as described in related technologies) Figure 1A and Figure 1B (As shown in the example) connected to the excitation electrode 60, therefore, when fabricating the piezoelectric layer 30 and the excitation electrode 60, it is not necessary to restrict "the excitation electrode must be partially exposed" or "the excitation electrode cannot be completely covered by the piezoelectric layer". Consequently, the piezoelectric layer 30 fabricated in the technical solution of this application can extend beyond the location of the excitation electrode 60, thus eliminating many restrictions in related technologies. This allows for more flexible fabrication methods for the ultrasonic transducer 100. Furthermore, because these restrictions in related technologies have been eliminated, the piezoelectric layer 30 of the fabricated ultrasonic transducer 100 is relatively effective. The working area (i.e., the AA area) can be further expanded (for example, it can be expanded beyond the excitation electrode 60), and the top electrode 40 can also be expanded 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 area, 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 prepared ultrasonic transducer 100.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] Preferably, the temperature for cryogenic sputtering is 70°C to 110°C. Within this temperature range, the effect of cryogenic sputtering can be better guaranteed, and the risk of piezoelectric layer 30 deteriorating or failing due to high temperature can be better avoided, thus better ensuring the function of piezoelectric layer 30.

[0156] Optionally, a full-layer seed metal layer 50 can be formed on the substrate 10 (e.g., by cryogenic sputtering) so that 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 are all covered by the seed metal layer 50. It should be understood that forming a full-layer seed metal layer 50 on the substrate 10 allows the seed metal layer 50 to be formed on any existing structure on the substrate 10, thus reducing the complexity of the process.

[0157] S1064: A barrier structure is formed above the substrate to create a space above the piezoelectric layer for fabricating the top electrode.

[0158] This application can form a barrier structure 80 above the substrate 10. The barrier structure 80 forms a receiving space 81 above the piezoelectric layer 30. It can be used as a barrier when the top electrode 40 is subsequently fabricated to ensure that the fabricated top electrode 40 is in a predetermined position more accurately, reduce the positional error of the top electrode 40, thereby improving the quality stability of the top electrode 40 and improving the performance of the fabricated ultrasonic transducer 100.

[0159] Optionally, the enclosure structure 80 can be removed after use and is not retained in the ultrasonic transducer 100, but is used only as a temporary structure for the fabrication of the ultrasonic transducer 100.

[0160] In some optional embodiments, the angle between at least one inner sidewall of the enclosure structure 80 formed in step S1064 and the normal of the substrate 10 is less than or equal to 45°, and the angle between at least one outer sidewall of the subsequently fabricated top electrode 40 and the normal of the substrate 10 is less than or equal to 45°. Furthermore, the thickness of the enclosure structure 80 is not less than the thickness of the top electrode 40. With such an enclosure structure 80, during the subsequent electroplating of the seed metal layer in the accommodating space, the enclosure structure 80 limits the angle between at least one outer sidewall of the electroplated top electrode 40 and the normal of the substrate 10 to be less than or equal to 45°. This optional structure results in a smaller diffraction echo of the ultrasonic signal due to the boundary morphology of the top electrode 40, thereby better reducing interference to the ultrasonic transducer 100 during use and improving the performance of the ultrasonic transducer 100. Moreover, the aforementioned angle range has lower requirements for the fabrication process, making the formation of the top electrode 40 easier, thus reducing the fabrication difficulty of the ultrasonic transducer.

[0161] In some optional embodiments, the angle between each inner sidewall of the enclosure structure 80 and the normal to the substrate 10 is less than or equal to 45°. In the embodiments of this application, the angle between each outer sidewall of the top electrode 40 and the normal to the substrate 10 is less than or equal to 45°.

[0162] Preferably, the angle between at least one inner wall of the enclosure structure 80 and the normal to the substrate 10 is less than or equal to 5°. Preferably, the angle between at least one outer wall of the top electrode 40 obtained in this embodiment and the normal to the substrate 10 is less than or equal to 5°.

[0163] Preferably, the angle between each inner sidewall of the enclosure structure 80 and the normal to the substrate 10 is less than or equal to 5°. Preferably, the angle between each outer sidewall of the top electrode 40 obtained in this embodiment and the normal to the substrate 10 is less than or equal to 5°.

[0164] Preferably, the angle between at least one inner wall of the enclosure structure 80 and the normal to the substrate 10 is 0°. Preferably, the angle between at least one outer wall of the top electrode 40 and the normal to the substrate 10 is 0°.

[0165] Preferably, the angle between each inner sidewall of the enclosure structure 80 and the normal to the substrate 10 is 0°. Preferably, the angle between each outer sidewall of the top electrode 40 and the normal to the substrate 10 is 0°.

[0166] This application does not limit the specific implementation of step S1064. In some optional embodiments, step S1064 may include: forming a photoresist layer above the substrate 10, and patterning and curing the photoresist layer to form a enclosure structure 80; wherein, patterning and curing the photoresist layer includes: patterning the photoresist layer to enclose a receiving space 81 for fabricating the top electrode 40, and then curing it.

[0167] Optionally, a photoresist layer can be formed on the upper surface of the substrate 10, which can be achieved by a series of coating methods such as spin coating, spray coating, roll coating, and slot coating, or by dry film lamination. Optionally, the patterning and curing of the photoresist layer can be achieved by any feasible method such as exposure and development, dry etching, or wet etching, without specific limitations.

[0168] For example, taking spin coating as an example, in one optional method, a full layer of photoresist can be spin-coated onto the upper surface of the substrate 10, and the photoresist layer can be patterned and cured by exposure and development, so that the patterned photoresist layer forms a receiving space 81 for fabricating the top electrode 40 above the piezoelectric layer 30, and then cured to form the enclosure structure 80. The opening 31 communicates with the receiving space 81.

[0169] Optionally, the curing temperature during photoresist curing is controlled below 135°C to effectively ensure the curing effect and avoid the risk of reduced piezoelectric performance or failure of the piezoelectric layer 30 due to high temperature, thus ensuring the function of the piezoelectric layer 30. Preferably, the temperature can be 70°C to 110°C.

[0170] Optionally, the enclosure structure 80 can be made of a non-conductive material. Optionally, the enclosure structure 80 can be made of an organic material, such as at least one of the following: polyimide (PI), poly-p-phenylene benzobisoxazole (PBO), epoxy resin, acrylic resin, etc. The enclosure structure 80 can also be made of organosiloxane composite materials. For example, organosiloxane composite materials can include, but are not limited to, organosilicon cyclic compounds, silicone rubber, silicone resin, etc. It should be understood that in this application, the enclosure structure 80 can be effectively prepared using a single material or a mixture of two different materials to obtain an ultrasonic transducer with better performance.

[0171] S1066: The seed metal layer is energized, and the seed metal layer in 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.

[0172] In this application, the seed metal layer 50 can be used as the cathode (i.e., the electroplating substrate) for electroplating. The top electrode 40 is obtained by passing an electric current through the seed metal layer 50, at least in the accommodating space, to electroplat the seed metal layer 50.

[0173] In this application, the top electrode 40 is obtained by electroplating based on the principle of electrolysis. On the cathode (electroplating substrate, i.e., seed metal layer 50) of the electroplating, metal cations accept electrons and are reduced to metal atoms, which are then deposited to form a dense metal coating. The metal coating obtained by electroplating is dense and free from delamination, pores, resin agglomeration, and other abnormalities. It should be understood that the metal coating after electroplating is also the top electrode 40. Therefore, the top electrode 40 has good performance, which is beneficial to improving the performance of the prepared ultrasonic transducer 100.

[0174] In some optional embodiments, the metal material used for electroplating in this application includes at least one metal material selected from tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead; or, the metal material used for electroplating includes an alloy of at least two of tin, copper, nickel, gold, silver, indium, chromium, zinc, titanium, and lead. Using at least one of the above materials, the top electrode 40 can be effectively electroplated, and the performance of the top electrode 40 can be guaranteed, thereby ensuring the performance of the prepared ultrasonic transducer.

[0175] Based on this, the top electrode 40 prepared by steps S1062-S1064 in this application can effectively achieve electrical connection with the excitation electrode 60 through the seed metal layer 50 in the opening 31 of the piezoelectric layer 30. Furthermore, by preparing the top electrode 40 of the ultrasonic transducer 100 through electroplating of the seed metal layer, the required thickness of the top electrode 40 can be better controlled through electroplating, making the fabrication process of the ultrasonic transducer 100 simpler and easier to manage. Moreover, the thickness tolerance of the prepared top electrode 40 is smaller, resulting in better quality stability of the top electrode 40. This method can effectively improve the performance of the prepared ultrasonic transducer 100. On the other hand, since the top electrode 40 can be obtained by electroplating in the enclosure space formed by the enclosure structure 80, the prepared top electrode 40 can be more accurately positioned, reducing the positional error of the top electrode 40, thereby further improving the quality stability of the top electrode 40 and improving the performance of the prepared ultrasonic transducer 100. Furthermore, the method of preparing the top electrode 40 to the required thickness by electroplating has fewer steps, which can effectively reduce the process difficulty and time cycle, and reduce the probability of production abnormalities.

[0176] It should be understood that the specific electroplating process can be carried out in any suitable manner, and will not be elaborated here.

[0177] Alternatively, after the top electrode is fabricated, the enclosure structure 80 can be removed. For example, taking the enclosure structure 80 made of photoresist layer as an example, the enclosure structure 80 can be removed by a photoresist stripping process (e.g., a dissolution photoresist stripping process to dissolve the enclosure structure 80 and remove it).

[0178] Optionally, after the top electrode is fabricated, the excess portion (i.e. the portion where the top electrode 40 is not electroplated) in the non-electroplated metal area of ​​the seed metal layer 50 can be etched to remove it.

[0179] In some alternative embodiments, the method of preparing the top electrode in step S106 may include: placing a top electrode paste on top of the piezoelectric layer 30, allowing the top electrode paste to enter the opening 31 and contact the excitation electrode 60, and forming a top electrode 40 after the top electrode paste is cured, so that the top electrode 40 forms an electrical connection with the excitation electrode 60 through the opening 31.

[0180] For example, a printing process can be used to deposit the top electrode paste above the piezoelectric layer 30. Alternatively, a spraying process can be used to deposit the top electrode paste above the piezoelectric layer 30. Taking the printing process as an example, the printing process can be screen printing or stencil printing. When printing the top electrode paste above the piezoelectric layer 30, the fluidity of the printed top electrode paste allows it to enter the opening 31 and contact the excitation electrode 60 exposed within the opening 31. The top electrode paste then solidifies to form the top electrode 40, which is electrically connected to the excitation electrode 60. It is understood that this printing method can effectively fabricate the top electrode 40 and effectively allow the top electrode 40 to form an electrical connection with the excitation electrode 60 through the opening 31.

[0181] Alternatively, when fabricating the top electrode 40 using a method such as screen printing to apply the top electrode paste, the top electrode 40 may partially extend beyond the edge of the piezoelectric layer 30 (which can be combined with...). Figure 6B Process examples Figure 3A and Figure 3B (As shown in the diagram). It should be understood that, since the process precision of processes such as screen printing is generally lower than that of electroplating, if the top electrode 40 is to be kept within the edge of the piezoelectric layer 30, a larger chip area is required as a buffer space, and a larger piezoelectric layer 30 needs to be fabricated. This may not meet the miniaturization requirements of the ultrasonic transducer 100 in some cases. Furthermore, 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, it is more suitable for the process precision of processes such as screen printing, and can better ensure that the printed top electrode paste can fill the opening 31 of the piezoelectric layer 30. This allows the fabricated top electrode 40 to be more stably electrically connected to the excitation electrode 60, thereby ensuring the performance of the ultrasonic transducer 100.

[0182] Of course, when the top electrode 40 is prepared by means of setting the top electrode paste, such as screen printing, the top electrode 40 may not extend beyond the edge of the piezoelectric layer 30, as long as the requirements are met. There is no unique limitation in this application.

[0183] It should be understood that, in addition to the electroplating and printing processes mentioned above, other alternative methods can be used to fabricate the top electrode 40, and no restrictions are imposed here.

[0184] In some optional embodiments, the preparation method of this application embodiment further includes: preparing a protective layer 70 covering at least a portion of the top electrode 40.

[0185] Based on this, by preparing a protective layer 70 covering at least part of the top electrode 40, the top electrode 40 can be protected at least to ensure the performance of the top electrode 40 and improve the performance of the prepared ultrasonic transducer 100.

[0186] 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.

[0187] 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.

[0188] 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.

[0189] <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: Apply electricity to the seed metal layer 50 and electroplate the seed metal layer 50 in the accommodating space (i.e., the area not covered by the enclosure structure 80) to obtain the top electrode 40. Try to make the outer wall of the top electrode 40 perpendicular to the substrate 10 (i.e., try to make the angle between the outer wall of the top electrode 40 and the normal of the substrate 10 close to 0°). Step 5: Remove the barrier structure 80 formed by photoresist through a photoresist removal process; Step 6: Remove the seed metal layer 50 of the non-electroplated metal area by 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 the 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, thus obtaining the ultrasonic transducer 100.

[0190] It should be understood that Figure 2A , Figure 6A The examples shown are not intended to limit the embodiments of this application.

[0191] <Optional Preparation Scheme 2> Reference Figure 6B The schematic diagram of the fabrication process of the ultrasonic transducer is shown. This process can be used to fabricate transducers such as… Figure 6B 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: Using a screen printing process, brush the top electrode paste on top of the piezoelectric layer 30, so that the top electrode paste enters the opening 31 and contacts the excitation electrode 60. After the top electrode paste is cured, the top electrode 40 is formed, so that the top electrode 40 forms an electrical connection with the excitation electrode 60 through the opening 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, thus obtaining the ultrasonic transducer 100.

[0192] It should be understood that Figure 3A , Figure 6B The examples shown are not intended to limit the embodiments of this application. Furthermore, as... Figure 3A The example of the ultrasonic transducer 100 shown can also be fabricated using the process of optional fabrication scheme 2.

[0193] 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 this application, and they are not intended to limit the embodiments of this application in any way. In addition, the descriptions are relatively concise and can be understood in conjunction with the relevant descriptions of the preceding embodiments.

[0194] It should be noted that the preparation method of the ultrasonic transducer 100 described above can also be understood by referring to the embodiments of the ultrasonic transducer 100 in the first aspect above. Furthermore, the above description is only some optional embodiments of the ultrasonic transducer scheme of this application, and is not intended to limit the embodiments of this application in any way.

[0195] According to a second aspect of the embodiments of this application, referring to... Figure 7 As shown, an ultrasonic fingerprint module 200 is provided, including: an ultrasonic transducer 100 as provided in the first aspect; wherein, an excitation electrode 60 is used to receive an excitation signal and apply an excitation signal to a top electrode 40 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 used to receive the 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 for fingerprint recognition.

[0196] Since the ultrasonic fingerprint module 200 of the second aspect includes the ultrasonic transducer 100 of the first aspect, it has better performance and can better realize the ultrasonic fingerprint function.

[0197] In some alternative embodiments, the ultrasonic fingerprint module 200 further includes an adhesive layer for bonding the ultrasonic transducer 100 of the ultrasonic fingerprint module 200 to an electronic device.

[0198] According to the third aspect of the embodiments of this application, referring to Figure 8A , Figure 8B As shown, an electronic device 300 is provided, including: the ultrasonic transducer 100 provided in the first aspect above, or the ultrasonic fingerprint module 200 provided in the second aspect above.

[0199] In some alternative embodiments, the electronic device 300 also includes a screen 320, a back panel, and a side bezel.

[0200] Optionally, when the electronic device 300 includes an ultrasonic transducer 100, the ultrasonic transducer 100 may 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.

[0201] 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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] It should be understood that the above are merely illustrative applications and are not intended to limit the embodiments of this application.

[0206] 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.

[0207] The optional embodiments of the present application have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present application are not limited thereto. It should be noted that, for the convenience of explaining the embodiments of the present application, the various drawings of the embodiments of the present application are not necessarily drawn to scale, and are only used to facilitate the explanation of the technical solution, and are not intended to limit the embodiments of the present application in any way. Within the scope of the technical concept of the embodiments of the present application, various simple modifications can be made to the technical solutions of the embodiments of the present application. The various technical features included in the different embodiments of the present application can be separated and / or combined in any suitable manner. In order to avoid unnecessary repetition, the embodiments of the present application will not describe the various possible combinations separately. However, these simple modifications and combinations should also be regarded as the content disclosed in the embodiments of the present application, and all fall within the protection scope of the embodiments of the present application.

[0208] The term "comprising" and its variations as used herein are open-ended, meaning "including but not limited to". The term "based on" means "at least partially based 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 of "first", "second", etc., mentioned in this application are only used to distinguish different devices, modules, or units, and are not intended to limit the order of functions performed by these devices, modules, or units or their interdependencies. It should be noted that the modifications "a" and "a plurality" mentioned in this application are illustrative rather than restrictive, and those skilled in the art should understand that, unless explicitly indicated in the context, they should be understood as "one or more".

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of this application, and are not intended to limit them; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this 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 has a gap between it and the bottom electrode. The piezoelectric layer has an opening, and the top electrode is electrically connected to the excitation electrode through the opening.

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. An ultrasonic fingerprint module, characterized in that, include: The ultrasonic transducer as described in any one of claims 1-13, wherein the excitation electrode is used to receive an excitation signal and apply the excitation signal to the top electrode 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 the ultrasonic detection signal generated between the top electrode and the bottom electrode when the returned ultrasonic signal acts on the piezoelectric layer for fingerprint recognition.

15. An electronic device, characterized in that, include: The ultrasonic fingerprint module, screen, back panel, and side frame as described in claim 14, 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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