Electrode structure, ultrasonic transducer, ultrasonic transducer manufacturing process, and electronic device

Abstract

An electrode structure, an ultrasonic transducer, an ultrasonic transducer manufacturing process, and an electronic device. The electrode structure (1) comprises a metal layer (11) and an anti-oxidation protective layer (13) which are stacked, the protective layer (13) covers a first surface of the metal layer (11), and the protective layer (13) is in electrical contact with the metal layer (11); a connecting layer (15) is arranged between the protective layer (13) and the metal layer (11), the connecting layer (15) has conductivity; and an adhesive layer (12) is arranged on a second surface of the metal layer (11), the adhesive layer (12) has conductivity, and the second surface is arranged opposite to the first surface.

Description

Electrode structure, ultrasonic transducer, ultrasonic transducer manufacturing process and electronic equipment Technical Field

[0001] The present application relates to the technical field of ultrasonic transducers. More specifically, the present application relates to an electrode structure, an ultrasonic transducer, an ultrasonic transducer preparation process, and an electronic device. Background Art

[0002] Ultrasonic transducer sensors utilize the mechanical-electrical conversion characteristics of piezoelectric materials. They emit ultrasonic waves to the surface of the object under the action of voltage, and simultaneously detect the ultrasonic signals returning from the surface of the object. They can be applied to the field of biometric identification. Placing the ultrasonic transducer in a specific area of ​​the smartphone screen can achieve user identity authentication. The advantage of a fingerprint recognition system based on ultrasonic transducer sensing technology is that it is not only relatively insensitive to wet, dry, or dirty fingers, but can also penetrate thick glass screens and other materials such as screen protectors. Therefore, it provides smartphone manufacturers with more design freedom and can enhance the product's anti-interference and security.

[0003] Ultrasonic transducers generally consist of a bottom electrode, a piezoelectric layer, and a top electrode. In some scenarios, they also include a protective layer located above the top electrode to protect the sensor. The top electrode is located above the piezoelectric layer, and a portion of the top electrode is connected to the excitation electrode. In operating mode, the chip excitation electrode receives the excitation signal input by the external electrical connector and transmits the drive signal to the top electrode through the connection between the excitation electrode and the top electrode, thereby controlling the piezoelectric layer.

[0004] Due to the presence of a natural oxide layer on the metal surface of the excitation electrode, the connection with the top electrode often results in an open circuit, causing reliability issues. Therefore, how to solve the problem of the metal surface of the electrode being easily oxidized is a technical problem that technicians in this field urgently need to solve. Technical issues

[0005] The embodiments of the present application provide an electrode structure, an ultrasonic transducer, an ultrasonic transducer preparation process and an electronic device, in which an anti-oxidation protective layer is provided on the metal layer of the electrode structure, thereby solving the technical problem that the metal layer surface of the existing electrode structure is easily oxidized, resulting in electrical connection failure. Technical Solutions

[0006] To this end, the embodiments of the present application provide the following technical solutions:

[0007] In a first aspect, the present application discloses an electrode structure comprising: a metal layer and an anti-oxidation protective layer stacked in layers, wherein the protective layer covers a first surface of the metal layer and is in electrical contact with the metal layer;

[0008] A connecting layer is provided between the protective layer and the metal layer, and the connecting layer is conductive, and / or an adhesive layer is provided on the second surface of the metal layer, and the adhesive layer is conductive, and the second surface is arranged opposite to the first surface.

[0009] Furthermore, when a connection layer is provided between the protective layer and the metal layer, the protective layer and the connection layer contain the same metal element.

[0010] Furthermore, the protective layer comprises any one of tantalum nitride, titanium nitride, titanium aluminum nitride, titanium tungsten, and molybdenum nitride;

[0011] The connection layer includes any one of tantalum, titanium, chromium, titanium tungsten, molybdenum, gold, and silver.

[0012] Furthermore, when an adhesive layer is provided on the second surface of the metal layer, a barrier layer is provided between the adhesive layer and the metal layer, and the barrier layer is conductive and is made of an inert material.

[0013] A second aspect of the present application discloses an ultrasonic transducer comprising the above-mentioned electrode structure.

[0014] Furthermore, the ultrasonic transducer includes a substrate, an electrode is provided on the first surface of the substrate, the electrode includes an excitation electrode, the excitation electrode is composed of the electrode structure, the metal layer of the electrode structure is directly connected to the substrate, and / or the metal layer of the electrode structure is connected to the substrate through an adhesive layer.

[0015] Furthermore, the electrode further includes a pixel electrode and a metal pad, and the pixel electrode and the metal pad include a metal layer.

[0016] Furthermore, the pixel electrode and / or metal pad is composed of the electrode structure.

[0017] Furthermore, a passivation layer is provided on the first surface of the substrate, and a window is opened in the passivation layer at the location of the electrode to expose the electrode.

[0018] A portion of the passivation layer is covered with a piezoelectric layer, the pixel electrode is located under the piezoelectric layer, the piezoelectric layer is in electrical contact with the pixel electrode via the window, and the excitation electrode and the metal pad are located outside the region where the piezoelectric layer is located.

[0019] A top electrode is provided on the piezoelectric layer, and a portion of the top electrode is in electrical contact with the protective layer on the excitation electrode.

[0020] The third aspect of the present application discloses a preparation process of an ultrasonic transducer, including a wafer process, wherein the ultrasonic transducer is the above-mentioned ultrasonic transducer, and the wafer process includes an electrode etching process, wherein the electrode etching process includes:

[0021] covering a passivation layer on the substrate of the ultrasonic transducer;

[0022] Photoresist coating, so that the photoresist covers the passivation layer, and the photoresist is removed from the window area above the electrode;

[0023] Etching the window area above the electrode, with the etching endpoint being set on the protective layer on the electrode;

[0024] removing the photoresist on the surface of the passivation layer to form the electrode,

[0025] The electrodes include excitation electrodes.

[0026] Furthermore, the electrode further includes a pixel electrode and / or a metal pad.

[0027] A fourth aspect of the present application discloses a process for preparing an ultrasonic transducer, including a wafer process, wherein the ultrasonic transducer is the above-mentioned ultrasonic transducer, the wafer process includes an electrode etching process, the electrode includes an excitation electrode, a pixel electrode and a metal pad, and the electrode etching process includes:

[0028] covering a passivation layer on the substrate of the ultrasonic transducer;

[0029] Applying photoresist so that the photoresist covers the passivation layer, and removing the photoresist from the window area above the pixel electrode and the metal pad;

[0030] Etching the passivation layer in the window area, with the etching endpoints set at the metal layers of the pixel electrode and the metal pad, to form the pixel electrode and the metal pad;

[0031] removing the photoresist on the surface of the passivation layer;

[0032] Applying photoresist so that the photoresist covers the passivation layer, the pixel electrode, and the metal pad, and removing the photoresist from the window area above the excitation electrode;

[0033] Etching the passivation layer in the window area, with the etching endpoint being the protective layer on the electrode, to form the excitation electrode;

[0034] Remove the remaining photoresist.

[0035] The fifth aspect of the present application discloses an electronic device comprising the above-mentioned ultrasonic transducer.

[0036] Furthermore, the electronic device further includes a display screen, and the ultrasonic transducer is arranged below the display screen. Beneficial effects

[0037] The beneficial effects of this application are:

[0038] The present application covers the metal layer of the electrode structure with an anti-oxidation protective layer, which can prevent the metal layer from being corroded by external water vapor and oxygen, and prevent the formation of an oxide layer on the surface of the metal layer, thereby ensuring that the electrode structure always maintains good electrical contact with the electrode to which it is connected, avoiding the problem of open circuit, and ensuring the reliability of the ultrasonic transducer. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of each embodiment. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings in the specific description below of the present application without any creative work.

[0040] FIG1 shows a schematic structural diagram of an ultrasonic transducer in the prior art;

[0041] FIG2 is a schematic structural diagram of an excitation electrode in the prior art;

[0042] FIG3 is a schematic structural diagram of an electrode structure according to an embodiment of the present application;

[0043] FIG4 is a schematic structural diagram of an electrode structure according to an embodiment of the present application;

[0044] FIG5 is a schematic diagram showing the structure of an ultrasonic transducer according to an embodiment of the present application;

[0045] FIG6 shows a schematic structural diagram of an ultrasonic transducer according to an embodiment of the present application.

[0046] In the figure,

[0047] 1. Electrode structure; 11. Metal layer; 12. Adhesive layer; 13. Protective layer; 14. Barrier layer; 15. Connecting layer; 16. Oxide layer; 2. Substrate; 31. Excitation electrode; 32. Pixel electrode; 33. Metal pad; 4. Passivation layer; 5. Piezoelectric layer; 6. Top electrode; 7. Protective layer.

[0048] Implementation Methods of the Application

[0049] The following is a clear and complete description of the technical solutions of the electrode structure, ultrasonic transducer, and electronic device provided by this application, in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without making any creative efforts are within the scope of protection of this application.

[0050] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, features defined as "first", "second", and "third" may explicitly or implicitly include one or more features. In the description of the present application, "multiple" means two or more, unless otherwise clearly and specifically defined.

[0051] In this application, unless otherwise specified or limited, the terms "installed," "connected," "connect," "fixed," etc. should be understood in a broad sense. For example, they can refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. Those skilled in the art will understand the specific meanings of the above terms in this application based on specific circumstances.

[0052] In this application, the word "exemplary" is used to mean "serving as an example, illustration, or illustration." Any embodiment described in this application as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. The following description is given to enable any person skilled in the art to implement and use the present application. In the following description, the present application lists details for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present application can be implemented even without using these specific details. In other instances, well-known structures and processes are not elaborated in detail to avoid obscuring the description of the present application with unnecessary details. Therefore, the present application is not intended to be limited to the embodiments shown, but should be consistent with the widest scope consistent with the principles and features disclosed in this application.

[0053] A common ultrasonic transducer includes a silicon-based substrate containing multiple transistor units, such as N-type or P-type metal oxide semiconductor field effect transistors, and complementary metal oxide semiconductor field effect transistors (CMOS) composed of both. The silicon-based substrate also includes metal traces and interlayer vias for interconnection.

[0054] The transistor units of the silicon-based substrate are interconnected through metal wiring and through-holes, and contain multiple layers of metal, of which the top metal (Top metal) is laid on the surface of the silicon-based substrate, as shown in Figure 1, including an excitation electrode 31, a pixel electrode 32 and a metal pad 33. The excitation electrode 31 and the metal pad 33 are independent of each other, or the metal pad 33 or the excitation electrode 31 can be connected to each other by extension. The metal pad 33 is electrically connected to the external electrical connector of the ultrasonic transducer through a lead. The substrate 2 is covered with a passivation layer 4, and the passivation layer 4 is selectively opened according to design requirements to interact with the external circuit signal of the sensor. The pixel electrode 32 is located in the effective area of ​​the ultrasonic transducer, generally an array of pixel electrodes of n rows and m columns. This area is called the Active Area (hereinafter referred to as the AA area). It is covered with a piezoelectric layer 5, and the piezoelectric layer 5 is covered with a top electrode 6, and the top electrode 6 is covered with a protective layer 7. The piezoelectric layer 5 covers the AA area, while exposing the area outside the excitation electrode 31 (including the excitation electrode) for electrical connection with the top electrode or external electrical connector. A portion of the top electrode 6 extends downward along the edge of the piezoelectric layer 5 to the excitation electrode 31 and makes electrical contact with the excitation electrode 31 .

[0055] When the ultrasonic transducer is working, the external excitation signal is transmitted to the excitation electrode 31 through the metal pad 33. Since the excitation electrode 31 is electrically connected to the top electrode 6 of the transducer, the external excitation signal can be transmitted to the top electrode 6, forming a voltage difference between the top electrode 6 and the pixel electrode 32 of the ultrasonic transducer, thereby realizing control of the piezoelectric layer 5.

[0056] The longitudinal structure of the excitation electrode is shown in Figure 2, and includes a metal layer 11, an adhesive layer 12, and a barrier layer 14. The metal layer 11 is usually a composite metal of Al and Cu. During the transducer manufacturing process, product use process, or reliability testing scenario, due to the activity of Al and Cu metals, a natural oxide layer 16 is easily formed on it. The oxide layer 16 is generally an aluminum oxide layer with a thickness of several nanometers to tens of nanometers. Due to the high resistivity of aluminum oxide (generally in the range of 10^14 to 10^15 Ω·cm), an open circuit is easily formed at the top electrode-aluminum oxide-excitation electrode interface, affecting the electrical contact between the top electrode and the excitation electrode, causing reliability problems.

[0057] According to the first aspect of an embodiment of the present application, as shown in Figure 3, an electrode structure 1 is provided. In the embodiment of the present application, a protective layer 13 is arranged on the first surface of the metal layer 11 of the electrode structure 1. The protective layer 13 has conductive and antioxidant properties, which can prevent external water vapor and oxygen from corroding the metal layer 11 and prevent the formation of an oxide layer on the surface of the metal layer 11, thereby ensuring that the electrode structure 1 always maintains good electrical contact with the electrode to which it is connected, avoiding the problem of open circuit.

[0058] In some embodiments, the electrode structure 1 provided in the present application includes: a metal layer 11 and a protective layer 13 arranged in a stacked manner, wherein the protective layer 13 covers the first surface of the metal layer 11, and the protective layer 13 is in electrical contact with the metal layer 11, and is used to block the corrosion of the metal layer 11 by external water vapor and oxygen, and prevent the formation of an oxide layer on the surface of the metal layer 11. Optionally, the protective layer 13 is made of metal, metal alloy or metal nitride, for example, one of tantalum nitride (TaN), titanium nitride (TiN), titanium aluminum nitride (TiAlN), titanium tungsten (TiW), and molybdenum nitride (MoN) can be selected. Preferably, TaN is selected for the protective layer 13.

[0059] An adhesive layer 12 is provided on the second surface of the metal layer 11, which is disposed opposite the first surface. Adhesive layer 12 is attached to the second surface of the metal layer 11 to enhance mechanical adhesion between the materials and ensure adhesion between the metal layer 11 and other materials (e.g., dielectric layer, conductive layer).

[0060] In some embodiments, as shown in FIG4 , a connecting layer 15 is further disposed between the protective layer 13 and the metal layer 11. The connecting layer 15 is conductive and serves as an adhesive, bonding the protective layer 13 and the metal layer 11 together. Optionally, the connecting layer 15 can be made of one of tantalum (Ta), titanium (Ti), chromium (Cr), titanium tungsten (TiW), molybdenum (Mo), gold (Au), or silver (Ag). Preferably, Ta is used as the metal adhesion layer material for the connecting layer 15.

[0061] The protective layer 13 and the connecting layer 15 are composed of metal or a conductive metal-ceramic composite to ensure electrical conductivity with the metal layer 11. Optionally, the protective layer 13 and the connecting layer 15 are made of materials with similar material properties to optimize process compatibility, thermal expansion coefficient, corrosion resistance, and cost. In some embodiments, the protective layer 13 and the connecting layer 15 are composed of materials containing the same metallic element. Optionally, combinations of the following can be used: TaN for the protective layer 13 and Ta for the connecting layer 15; TiN for the protective layer 13 and Ti for the connecting layer 15; MoN for the protective layer 13 and Mo for the connecting layer 15; TiW for the protective layer 13 and Ti for the connecting layer 15.

[0062] In some embodiments, the coating process for the connecting layer 15 and the protective layer 13 is typically physical vapor deposition (PVD), such as sputtering or evaporation; chemical vapor deposition (CVD), such as plasma-enhanced chemical vapor deposition (PECVD), atmospheric pressure chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), metal organic chemical vapor deposition (MOCVD), etc. Atomic layer deposition (ALD) can also be used for film formation. Optionally, the thickness of the connecting layer 15 is typically between 2 nm and 60 nm; the thickness of the protective layer 13 is typically between 2 nm and 60 nm.

[0063] In some embodiments, a barrier layer 14 is provided between the bonding layer 12 and the metal layer 11. Optionally, the barrier layer 14 is made of an inert material and is used to control or limit the diffusion or reaction of substances between the metal layer 11 and other layers. The material characteristics thereof include high chemical stability, low permeability, thermal stability, and mechanical stability. Common materials for the barrier layer 14 include metals, metal compounds, intermetallic compounds, and the like, for example, metal oxides, nitrides, silicides, nitrogen silicon compounds, and the like. Alternatively, the barrier layer 14 may also be provided as a multilayer thin film structure. The bonding layer 12 and the barrier layer 14 are conductive. Optionally, the bonding layer 12 may be made of the same material as the connecting layer 15, and the barrier layer 14 may be made of the same material as the protective layer 13. Optionally, the coating process of the bonding layer 12 and the barrier layer 14 may also be the same as the coating process of the first protective layer 13 and the protective layer 13.

[0064] According to a second aspect of an embodiment of the present application, an ultrasonic transducer is provided, as shown in FIG5 , comprising a substrate 2, and a plurality of electrodes are provided on the first surface of the substrate 2. A passivation layer 4 is covered on the first surface of the substrate 2, and then windows are opened on the passivation layer 4 at positions corresponding to the electrodes to expose the electrodes. The plurality of electrodes include an excitation electrode 31, a pixel electrode 32, and a metal pad 33, wherein the pixel electrode 32 is located in the effective area of ​​the ultrasonic transducer, and is covered with a piezoelectric layer 5 above it, and a top electrode 6 is covered above the piezoelectric layer 5, and a protective layer 7 is covered above the top electrode 6. The excitation electrode 31 and the metal pad 33 are located outside the effective area, a portion of the excitation electrode 31 is in electrical contact with the top electrode 6, and a portion is electrically connected to the metal pad 33 through a conductive structure.

[0065] In some embodiments, the excitation electrode 31 is composed of the above-mentioned electrode structure 1, that is, the metal layer 11 of the excitation electrode 31 is covered with a protective layer 13, and the top electrode 6 is in electrical contact with the protective layer 13. In this embodiment, when the passivation layer 4 is opened, the etching of the excitation electrode 31 area is controlled, and the etching stop point is kept above the protective layer 13 of the excitation electrode 31, thereby preserving the protective layer 13. The protective layer 13 has both electrical conductivity and oxidation resistance. The presence of the protective layer 13 prevents the corrosion of the metal layer 11 by external water vapor and oxygen, and prevents the formation of an oxide layer on the surface of the metal layer 11. This ensures that there is always good electrical contact between the interface between the top electrode 6 and the excitation electrode 31 during the subsequent transducer manufacturing process and product use, thereby solving the open circuit problem. In addition, the module reliability test items of the ultrasonic transducer include high temperature and humidity (85℃ / 85%RH, 60℃ / 90%RH), low temperature (-40℃), hot and cold cycles (-40℃~85℃), etc., and the reliability test is required to meet at least 240 hours. The presence of the protective layer 13 also ensures that the metal layer 11 of the chip excitation electrode 31 and the transducer electrode will not be disconnected due to heat, water, and oxygen corrosion during reliability tests in high temperature and high humidity environments, thereby ensuring the reliability of the ultrasonic transducer.

[0066] In some embodiments, as shown in FIG6 , the metal pad 33 and the pixel electrode 32 may both be formed by the electrode structure 1 , that is, the pixel electrode 32 and the metal pad 33 are both provided with a protective layer 13 , so that the position of the excitation electrode 31 does not need to be selectively etched.

[0067] In some embodiments, the excitation electrode 31 and the metal pad 33 are composed of the above-mentioned electrode structure 1, that is, the excitation electrode 31 and the metal pad 33 are provided with a protective layer 13 to prevent oxidation. Since the pixel electrode 32 is covered by the piezoelectric layer 5, it is not easy to be oxidized, and the protective layer 13 may not be provided.

[0068] In a third aspect of the present application, a process for preparing an ultrasonic transducer is provided.

[0069] In some embodiments, only the excitation electrode 31 includes the protective layer 13, and a selective etching scheme is used to form different electrodes. The preparation process includes:

[0070] A passivation layer 4 is covered on the first surface of the substrate 2, and then a window is opened on the passivation layer 4. The window opening process of the passivation layer 4 includes:

[0071] First, the photoresist covers the entire surface of the passivation layer 4. Through exposure and development, the photoresist corresponding to the window area of ​​the passivation layer 4 above the pixel electrode 32 and the metal pad 33 is removed, exposing the window area of ​​the passivation layer 4 above the pixel electrode 32 and the metal pad 33. However, the photoresist of the passivation layer 4 above the excitation electrode 31 is retained. Then, the passivation layer 4 above the pixel electrode 32 and the metal pad 33 is etched, with the etching stop point set at the surface of the metal layer 11. Then, all photoresist above the passivation layer 4 is removed, forming the pixel electrode 32 and the metal pad 33.

[0072] Next, the photoresist coating, exposure, and development steps are repeated. During this process, only the photoresist in the windowed area of ​​the passivation layer 4 above the excitation electrode 31 is removed, while the photoresist in other areas remains. Next, the passivation layer 4 above the excitation electrode 31 is etched, with the etching stop point set at the surface of the protective layer 13. Finally, the photoresist on the surface of the passivation layer 4 is removed, forming the excitation electrode 31.

[0073] Through the above steps, the wafer surface structure shown in Figure 5 is achieved. Specifically, the passivation layer 4 above the pixel electrode 32, the excitation electrode 31, and the metal pad 33 is windowed. The surface of the pixel electrode 32 and the metal pad 33 is the metal layer 11, while the protective layer 13 is retained above the excitation electrode 31. During the subsequent manufacturing process of the ultrasonic transducer, the product usage process, and environmental reliability testing, the interface between the top electrode 6 and the excitation electrode 31 is protected by the protective layer 13, preventing the interface between the two from being oxidized, thereby ensuring the stability of the electrical connection between the two.

[0074] In a fourth aspect of the present application, a process for preparing an ultrasonic transducer is provided.

[0075] In some embodiments, as shown in FIG6 , the excitation electrode 31 , the metal pad 33 , and the pixel electrode 32 are all formed by the electrode structure 1 described above, that is, the excitation electrode 31 , the pixel electrode 32 , and the metal pad 33 are all provided with a protective layer 13 , so that selective etching of the position of the excitation electrode 31 is not required. The preparation process includes:

[0076] A passivation layer 4 is covered on the first surface of the substrate 2, and then a window is opened on the passivation layer 4. The window opening process on the passivation layer 4 includes:

[0077] First, the photoresist covers the entire surface of the passivation layer 4, and the photoresist corresponding to the window area of ​​the passivation layer 4 above the pixel electrode 32, the excitation electrode 31, and the metal pad 33 is removed by exposure and development, revealing the window area of ​​the passivation layer 4 above the pixel electrode 32, the excitation electrode 31, and the metal pad 33.

[0078] Then, the passivation layer 4 above the pixel electrode 32, the excitation electrode 31, and the metal pad 33 is etched, with the etching stop point set on the surface of the protective layer 13. Finally, the photoresist on the surface of the passivation layer 4 is removed, forming the pixel electrode 32, the excitation electrode 31, and the metal pad 33.

[0079] Through the above steps, the passivation layer 4 above the pixel electrode 32, the excitation electrode 31, and the metal pad 33 is completely windowed, and a protective layer 13 is formed on the surfaces of the pixel electrode 32, the excitation electrode 31, and the metal pad 33. During subsequent ultrasonic transducer manufacturing processes, product use, and environmental reliability testing, the interface between the top electrode 6 and the excitation electrode 31 is protected by the protective layer 13, preventing oxidation, thereby ensuring the stability of the electrical connection between the two.

[0080] In a fifth aspect of the embodiments of the present application, an electronic device is provided, comprising the ultrasonic transducer described above. Optionally, the electronic device comprises a smartphone, tablet computer, laptop computer, or other device, wherein the device comprises a display screen, and the ultrasonic transducer is disposed below the display screen. In other embodiments, the electronic device may also comprise a device with a fingerprint recognition function, such as a fingerprint lock or attendance time clock. In such a device, the ultrasonic transducer is disposed below a cover plate and does not need to be assembled with the display screen.

[0081] In this application, a protective layer 13 is provided at least at the metal connection interface between the ultrasonic transducer's top electrode 6 and the excitation electrode 31 to ensure uninterrupted electrical connection during manufacturing, product use, and reliability testing. This addresses the issue of poor electrical contact at the metal interface due to oxidation intolerance. Protective layer 13 is both conductive and resistant to oxidation, enhancing the reliability of the ultrasonic transducer.

[0082] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and simple improvements made to the essential content of the present application shall be included in the scope of protection of the present application. Industrial Applicability

[0083] The electrode structure provided in the present application is covered with an anti-oxidation protective layer on the metal layer, which can prevent the metal layer from being corroded by external water vapor and oxygen, and prevent the formation of an oxide layer on the surface of the metal layer, thereby ensuring that the electrode structure always maintains good electrical contact with the electrode to which it is connected, and solves the problem that the electrical connection of the electrode connection structure is easily open due to oxidation.

Claims

1. An electrode structure, wherein: The invention comprises a stacked arrangement of: a metal layer and an anti-oxidation protective layer, wherein the protective layer covers a first surface of the metal layer and is in electrical contact with the metal layer; A connecting layer is provided between the protective layer and the metal layer, and the connecting layer is conductive, and / or an adhesive layer is provided on the second surface of the metal layer, and the adhesive layer is conductive, and the second surface is arranged opposite to the first surface.

2. The electrode structure according to claim 1, wherein: The protective layer and the connecting layer contain the same metal element.

3. The electrode structure according to claim 1 or 2, wherein: The protective layer comprises any one of tantalum nitride, titanium nitride, titanium aluminum nitride, titanium tungsten, and molybdenum nitride; The connection layer includes any one of tantalum, titanium, chromium, titanium tungsten, molybdenum, gold, and silver.

4. The electrode structure according to claim 1, wherein When an adhesive layer is provided on the second surface of the metal layer, a barrier layer is provided between the adhesive layer and the metal layer. The barrier layer has conductivity and is made of an inert material.

5. An ultrasonic transducer, wherein: The electrode structure comprises the electrode structure according to any one of claims 1 to 4.

6. The ultrasonic transducer according to claim 5, wherein: The ultrasonic transducer includes a substrate, an electrode is provided on the first surface of the substrate, the electrode includes an excitation electrode, the excitation electrode is composed of the electrode structure, the metal layer of the electrode structure is directly connected to the substrate, and / or the metal layer of the electrode structure is connected to the substrate via an adhesive layer.

7. The ultrasonic transducer according to claim 6, wherein: The electrode further includes a pixel electrode and a metal pad, and the pixel electrode and the metal pad include a metal layer.

8. The ultrasonic transducer according to claim 7, wherein: The pixel electrode and / or metal pad is formed by the electrode structure.

9. The ultrasonic transducer according to claim 7 or 8, wherein: A passivation layer is provided on the first surface of the substrate, and a window is opened in the passivation layer at the location of the electrode to expose the electrode. A portion of the passivation layer is covered with a piezoelectric layer, and the pixel electrode is located on the piezoelectric layer. On the lower side of the piezoelectric layer, the piezoelectric layer is in electrical contact with the pixel electrode via the window, and the excitation electrode and the metal pad are located outside the area where the piezoelectric layer is located. A top electrode is provided on the piezoelectric layer, and a portion of the top electrode is in electrical contact with the protective layer on the excitation electrode.

10. A process for preparing an ultrasonic transducer, comprising a wafer process, wherein: The ultrasonic transducer is the ultrasonic transducer according to any one of claims 5 to 9, and the wafer manufacturing process includes an electrode etching process, and the electrode etching process includes: covering a passivation layer on the substrate of the ultrasonic transducer; Photoresist coating, so that the photoresist covers the passivation layer, and the photoresist is removed from the window area above the electrode; Etching the window area above the electrode, with the etching endpoint being set on the protective layer on the electrode; removing the photoresist on the surface of the passivation layer to form the electrode, The electrodes include excitation electrodes.

11. The process for preparing an ultrasonic transducer according to claim 10, wherein: The electrodes further include pixel electrodes and / or metal pads.

12. A process for preparing an ultrasonic transducer, comprising a wafer process, wherein: The ultrasonic transducer is the ultrasonic transducer according to any one of claims 5 to 9, the wafer manufacturing process includes an electrode etching process, the electrode includes an excitation electrode, a pixel electrode and a metal pad, and the electrode etching process includes: covering a passivation layer on the substrate of the ultrasonic transducer; Applying photoresist so that the photoresist covers the passivation layer, and removing the photoresist from the window area above the pixel electrode and the metal pad; Etching the passivation layer in the window area, with the etching endpoints set at the metal layers of the pixel electrode and the metal pad, to form the pixel electrode and the metal pad; removing the photoresist on the surface of the passivation layer; Applying photoresist so that the photoresist covers the passivation layer, the pixel electrode, and the metal pad, and removing the photoresist from the window area above the excitation electrode; Etching the passivation layer in the window area, with the etching endpoint being the protective layer on the electrode, to form the excitation electrode; Remove the remaining photoresist.

13. An electronic device, wherein: The ultrasonic transducer comprises the ultrasonic transducer according to any one of claims 5 to 9.

14. The electronic device according to claim 13, wherein: The electronic device further includes a display screen, and the ultrasonic transducer is arranged below the display screen.

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