Fingerprint recognition unit and preparation method thereof, fingerprint recognition module and display device

Abstract

The present disclosure provides a fingerprint recognition unit, which includes: a receiving electrode layer, including a plurality of receiving electrodes, the plurality of receiving electrodes are arranged in an array along a first direction and a second direction, a piezoelectric material layer, arranged on one side of the receiving electrode layer; a driving electrode layer, arranged on a side of the piezoelectric material layer away from the receiving electrode layer, including: a plurality of driving electrodes arranged along the second direction, the driving electrodes are strip electrodes extending along the first direction and overlapping with the plurality of receiving electrodes arranged along the first direction; the material of the driving electrodes includes a metal material suitable for an electroplating process, and the thickness of the driving electrodes is configured so that the vibration node of the piezoelectric material layer is located inside the piezoelectric material layer. The embodiments of the present disclosure also provide a method for preparing a fingerprint recognition unit, a fingerprint recognition module, and a display device.

Description

Technical Field

[0001] The present invention relates to the field of fingerprint recognition technology, and in particular to a fingerprint recognition unit and a preparation method thereof, a fingerprint recognition module and a display device. Background Art

[0002] Ultrasonic fingerprint recognition technology is a new type of fingerprint recognition technology. Its main principle is: when the transmitted wave contacts an object (such as a finger), the vibration intensity of the reflected wave (also called echo) will be different due to the valleys and ridges of the fingerprint. Therefore, the position of the valleys and ridges can be determined by detecting the vibration intensity of the reflected wave, thereby realizing fingerprint recognition. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art, and proposes a fingerprint recognition unit and a preparation method thereof, a fingerprint recognition module and a display device.

[0004] In a first aspect, an embodiment of the present disclosure provides a fingerprint recognition unit, which includes:

[0005] The receiving electrode layer includes a plurality of receiving electrodes, wherein the plurality of receiving electrodes are arranged in an array along a first direction and a second direction.

[0006] A piezoelectric material layer, arranged on one side of the receiving electrode layer;

[0007] A driving electrode layer, arranged on a side of the piezoelectric material layer away from the receiving electrode layer, comprising: a plurality of driving electrodes arranged along the second direction, the driving electrodes being strip electrodes extending along the first direction and overlapping with the plurality of receiving electrodes arranged along the first direction;

[0008] The material of the driving electrode includes a metal material suitable for an electroplating process, and the thickness of the driving electrode is configured so that the vibration node surface of the piezoelectric material layer is located inside the piezoelectric material layer.

[0009] In some embodiments, the material of the driving electrode includes copper, and the thickness of the driving electrode includes 14 um to 45 um.

[0010] In some embodiments, it further includes: a base substrate and a fingerprint recognition circuit layer located on the base substrate, wherein the receiving electrode layer is located on a side of the fingerprint recognition circuit layer away from the base substrate;

[0011] The fingerprint recognition circuit includes a plurality of fingerprint recognition circuits corresponding to the receiving electrodes one by one, and the fingerprint recognition circuits are electrically connected to the corresponding receiving electrodes.

[0012] In some embodiments, a passivation layer is disposed between adjacent receiving electrodes and between the receiving electrodes and the piezoelectric material layer.

[0013] In some embodiments, a maximum distance between a surface of the substrate away from the piezoelectric material layer and a surface of the passivation layer close to the piezoelectric material layer is 80 um to 100 um.

[0014] In some embodiments, the material of the piezoelectric material layer includes: polyvinylidene fluoride;

[0015] The thickness of the piezoelectric material layer is 8um to 10um.

[0016] In some embodiments, it also includes: a packaging pattern, wherein the packaging pattern covers the side surface of the piezoelectric material layer.

[0017] In some embodiments, the side of the packaging pattern away from the piezoelectric material layer is a sloped surface, and the angle between the sloped surface and the plane where the side of the piezoelectric material layer is located is 30° to 60°.

[0018] In some embodiments, the method further includes: a protective layer, wherein the protective layer is located on a side of the driving electrode away from the piezoelectric material layer.

[0019] In some embodiments, the material of the protection layer includes an organic resin material, and the maximum thickness of the protection layer is greater than the thickness of the driving electrode.

[0020] In some embodiments, the width of the driving electrode includes: 65um-70um, and the spacing between adjacent driving electrodes includes: 8um-10um;

[0021] The receiving electrode is a rectangular electrode, the length of any side of the rectangular electrode is 65 to 70 um, and the spacing between adjacent rectangular electrodes is 8 to 10 um.

[0022] In a second aspect, an embodiment of the present disclosure further provides a fingerprint recognition module, which includes: a plurality of fingerprint recognition units arranged in an array, wherein the fingerprint recognition units are the fingerprint recognition units provided in the first aspect above.

[0023] In a third aspect, an embodiment of the present disclosure further provides a display device, which includes: the fingerprint recognition module provided in the second aspect above.

[0024] In a fourth aspect, the present disclosure also provides a method for preparing a fingerprint recognition unit, which can be used to prepare the fingerprint recognition unit in the first aspect, comprising:

[0025] A receiving electrode layer is formed on the base substrate, wherein the receiving electrode layer comprises a plurality of receiving electrodes, and the plurality of receiving electrodes are arranged in an array along a first direction and a second direction;

[0026] forming a piezoelectric material layer on a side of the receiving electrode layer away from the substrate;

[0027] A driving electrode layer with a certain thickness is formed on a side of the piezoelectric material layer away from the receiving electrode layer by a metal electroplating process, the driving electrode layer includes a plurality of driving electrodes arranged along a second direction, the driving electrodes are strip electrodes extending along the first direction and overlap with a plurality of receiving electrodes arranged along the first direction, and the thickness of the driving electrodes is configured so that the vibration node surface of the piezoelectric material layer is located inside the piezoelectric material layer.

[0028] In some embodiments, the step of forming a driving electrode layer having a certain thickness by a metal electroplating process on a side of the piezoelectric material layer away from the receiving electrode layer comprises:

[0029] A copper film is electroplated on the entire surface of the piezoelectric material layer away from the substrate substrate by an electroplating process to serve as a seed layer, wherein the thickness of the seed layer comprises:

[0030] forming a retaining wall layer on the seed layer, wherein the region of the retaining wall layer where the driving electrode is to be formed is a hollow structure, and the thickness of the retaining wall layer is greater than the thickness of the driving electrode to be formed;

[0031] Electroplating a copper film in the hollow structure by an electroplating process, wherein the copper film in the hollow structure is a growth layer pattern;

[0032] removing the retaining wall layer;

[0033] The growth layer patterns and the seed layer are thinned and etched simultaneously, the portion of the seed layer not covered by the growth layer pattern is completely removed, and the remaining portion of the growth layer pattern and the portion of the seed layer covered by the remaining portion constitute the driving electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic top view of a fingerprint recognition unit provided in an embodiment of the present disclosure;

[0035] Figure 2 for Figure 1 A-A' cross-section diagram;

[0036] Figure 3 for Figure 1 Schematic diagram of the cross section in the B-B' direction;

[0037] Figure 4A schematic top view of a fingerprint recognition module provided in an embodiment of the present disclosure;

[0038] Figure 5 A flowchart of a method for preparing a fingerprint recognition unit provided in an embodiment of the present disclosure;

[0039] Figure 6 A flowchart of another method for preparing a fingerprint recognition unit provided by an embodiment of the present disclosure;

[0040] Figures 7a to 7j To adopt Figure 6 A schematic diagram of the intermediate structure of a fingerprint recognition unit prepared by the preparation method shown;

[0041] Figure 8 The present invention is a flowchart of a specific method for forming a receiving electrode layer in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0042] In order to enable those skilled in the art to better understand the technical solution of the present invention, a fingerprint recognition unit and a preparation method thereof, a fingerprint recognition module and a display device provided by the present invention are described in detail below with reference to the accompanying drawings.

[0043] In the related art, the fingerprint recognition unit includes a driving electrode layer, a piezoelectric material layer and a receiving electrode layer, wherein the driving electrode in the driving electrode layer generally adopts a three-layer alloy structure of molybdenum-aluminum-molybdenum (Mo-Al-Mo), and specifically, a first layer of molybdenum film, an aluminum film and a second layer of molybdenum film are formed in sequence by a sputtering process, and then a pattern of the driving electrode layer is formed by a photolithography process. Among them, due to the limitation of the sputtering process, the thickness of the driving electrode layer with the Mo-Al-Mo structure is relatively thin (the overall thickness is 2.3mm). At this time, the vibration node surface of the piezoelectric material layer is located outside the piezoelectric material layer, and the difference in signals formed by the reflection of ultrasonic waves in the valley and ridge will be significantly reduced, which is not conducive to fingerprint imaging, that is, it does not meet the acoustic matching requirements.

[0044] In order to meet the acoustic matching requirements, an isolation layer and a metal reflective layer (also called an acoustic matching layer) are generally arranged on the side of the driving electrode layer away from the piezoelectric material layer. The material of the isolation layer is generally silicon nitride (SiNx), and the material of the metal reflective layer includes silver (Ag). The metal reflective layer is used to reflect the ultrasonic waves generated by the piezoelectric material layer to adjust the position of the vibration nodal surface of the piezoelectric material layer so that the vibration nodal surface of the piezoelectric material layer is located within the piezoelectric material layer to meet the acoustic matching requirements.

[0045] The technical solution of setting an isolation layer and a metal reflective layer has at least the following problems: First, the heat resistance temperature of the piezoelectric material layer is relatively low, and the isolation layer can only be prepared by the TFE process, which requires additional investment in new equipment during mass production; Second, after the driving electrode is energized, a parasitic capacitance is generated between the driving electrode and the metal reflective layer, which easily causes a breakdown short circuit between the driving electrode and the metal reflective layer, and the excitation voltage on the driving electrode cannot be increased, resulting in a decrease in the signal amount of the device, which ultimately affects the fingerprint recognition performance of the device.

[0046] In order to solve at least one of the technical problems existing in the related art, the embodiments of the present disclosure provide corresponding solutions, which will be described in detail below in conjunction with specific embodiments.

[0047] Figure 1 A top view schematic diagram of a fingerprint recognition unit provided in an embodiment of the present disclosure, Figure 2 for Figure 1 A-A' cross-section diagram, Figure 3 for Figure 1 The schematic diagram of the B-B' section is as follows: Figures 1 to 3 As shown, the fingerprint recognition unit includes: a receiving electrode layer, a piezoelectric material layer 2 and a driving electrode layer.

[0048] The receiving electrode layer includes a plurality of receiving electrodes 1, and the plurality of receiving electrodes 1 are arranged in an array along a first direction X and a second direction Y. Figure 1 The vertical direction in the second direction Y is Figure 1 The horizontal direction in is used as an example for an exemplary description. The piezoelectric material layer 2 is arranged on one side of the receiving electrode layer. The driving electrode layer is arranged on the side of the piezoelectric material layer 2 away from the receiving electrode layer, and the driving electrode layer includes: a plurality of driving electrodes 3 arranged along the second direction Y, the driving electrode 3 is a strip electrode extending along the first direction X and overlaps with a plurality of receiving electrodes 1 arranged along the first direction X; wherein the material of the driving electrode 3 includes a metal material suitable for an electroplating process, and the thickness of the driving electrode 3 is configured so that the vibration node plane of the piezoelectric material layer 2 (the plane where the amplitude is 0 when the piezoelectric material layer 2 emits an ultrasonic wave) is located inside the piezoelectric material layer 2.

[0049] The process of ultrasonic fingerprint recognition by the fingerprint recognition unit provided by the embodiment of the present disclosure is as follows: In the transmitting stage, a driving signal (for example, a sine wave signal) can be applied to the driving electrode 3, and a constant voltage can be applied to the receiving electrode 1 at the same time. Then, the piezoelectric component generates an inverse piezoelectric effect due to voltage excitation, and emits ultrasonic waves outward. When the emitted ultrasonic waves touch an object (for example, a finger), they are reflected and an echo is generated; since the fingerprints of fingers have valleys and ridges, the vibration intensity of the echo is different. In the sampling stage, the driving signal is stopped from being applied to the driving electrode 3 and a constant voltage is applied instead, and the constant voltage is stopped from being applied to the receiving electrode 1. The piezoelectric component is affected by the echo fed back by the finger. Due to the positive piezoelectric effect, an alternating current signal (a sine wave signal or a signal approximately equal to a sine wave signal) is generated on the receiving electrode 1. The alternating current signal can charge the sampling node. By measuring the amplitude (maximum voltage, also called the maximum peak voltage) of the signal at the sampling node, the valley position of the finger can be determined, thereby realizing ultrasonic fingerprint recognition.

[0050] In the embodiment of the present disclosure, the maximum thickness of the metal material film formed by the metal electroplating process can reach tens of microns or even nearly a hundred microns, which is much greater than the maximum thickness of the metal material film formed by the sputtering process. Therefore, the driving electrode 3 formed by the metal electroplating process can, on the one hand, play the role of loading signals to achieve fingerprint recognition drive, and on the other hand, the thickness can be designed so that the vibration node surface of the piezoelectric material layer 2 is located inside the piezoelectric material layer 2, thereby achieving the effect of acoustic matching, that is, the driving electrode 3 can play the role of the acoustic matching layer in the related technology.

[0051] Among them, metal materials suitable for electroplating process include: silver, copper, nickel, gold, etc. Considering factors such as production cost and difficulty of electroplating process, the material of the driving electrode 3 in the embodiment of the present disclosure is preferably copper.

[0052] Based on the above content, it can be seen that the driving electrode 3 in the technical solution of the present invention can not only realize the function of fingerprint recognition driving, but also play the role of an acoustic matching layer. Therefore, there is no need to additionally set an acoustic matching layer and an isolation layer in the fingerprint recognition unit provided by the present invention, thereby simplifying the device structure and effectively avoiding breakdown short circuit between the driving electrode 3 and the acoustic matching layer.

[0053] In some embodiments, the material of the piezoelectric material layer 2 includes polyvinylidene fluoride (PVDF for short); the thickness of the piezoelectric material layer 2 includes 8 um to 10 um.

[0054] In some embodiments, the width of the driving electrode 3 includes: 65um~70um, the spacing between adjacent driving electrodes 3 includes: 8um~10um, and the length of the driving electrode 3 is approximately equal to the length of the fingerprint recognition unit; the receiving electrode 1 is a rectangular electrode, and the length of any side of the rectangular electrode includes: 65~70um, and the spacing between adjacent rectangular electrodes includes: 8um~10um.

[0055] In some embodiments, the fingerprint recognition unit further includes: a substrate and a fingerprint recognition circuit layer (not shown) located on the substrate, the receiving electrode layer is located on a side of the fingerprint recognition circuit layer away from the substrate; the fingerprint recognition circuit includes a plurality of fingerprint recognition circuits corresponding to the receiving electrodes 1 one by one, and the fingerprint recognition circuits are electrically connected to the corresponding receiving electrodes 1. The fingerprint recognition circuit is used to provide a constant voltage to the receiving electrode 1 in the transmitting stage, and to receive the alternating current signal generated on the receiving electrode 1 in the sampling stage and provide it to an external processor for processing.

[0056] In some embodiments, a planarization layer (not shown) is provided between the fingerprint recognition circuit layer and the receiving electrode 1, and the receiving electrode 1 is electrically connected to the corresponding fingerprint recognition circuit layer through a via hole on the planarization layer. For the convenience of description, the structure composed of the base substrate, the fingerprint recognition circuit layer and the planarization layer is referred to as a carrier substrate 5.

[0057] It should be noted that the fingerprint recognition circuit is composed of electrical devices such as thin film transistors. The fingerprint recognition circuit in the embodiment of the present disclosure can adopt any conventional fingerprint recognition circuit, and the specific circuit structure of the fingerprint recognition circuit is not limited.

[0058] In some embodiments, a passivation layer 6 is provided between adjacent receiving electrodes 1 and between the receiving electrode 1 and the piezoelectric material layer 2. It should be noted that the provision of the passivation layer 6 can effectively prevent short circuits between adjacent receiving electrodes 1.

[0059] In some embodiments, the maximum distance between a surface of the substrate far from the piezoelectric material layer 2 and a surface of the passivation layer 6 close to the piezoelectric material layer 2 is 80 um to 100 um.

[0060] In some embodiments, the fingerprint recognition unit further includes: a packaging pattern 7, the packaging pattern 7 covers the side surface of the piezoelectric material layer 2; the packaging pattern 7 can play a role in protecting the fingerprint recognition unit.

[0061] In practical applications, each driving electrode 3 needs to be led out through a corresponding lead 4 so that an external signal can be written to the driving electrode 3. Since there is a certain step difference between the driving electrode 3 and the substrate, if the lead 4 is directly wired vertically, there is a greater risk of wire breakage. In some embodiments, preferably, the side of the package pattern 7 away from the piezoelectric material layer 2 is a slope surface, and the angle α between the slope surface and the plane where the side of the piezoelectric material layer 2 is located includes: 30° to 60°. At this time, the lead 4 can be smoothly wired along the slope surface, which can effectively reduce the risk of lead 4 breaking.

[0062] In some embodiments, the fingerprint recognition unit further includes: a protective layer 8 , which is located on a side of the driving electrode 3 away from the piezoelectric material layer 2 , and the protective layer 8 can be used to protect the driving electrode 3 .

[0063] In some embodiments, the material of the protective layer 8 includes an organic resin material, and the maximum thickness of the protective layer 8 is greater than the thickness of the driving electrode 3. In order to ensure the protective effect, the material of the protective layer 8 is an organic resin material with a relatively high viscosity. At this time, the organic resin material can be formed on the surface of the driving electrode 3 by using a screen printing technique. In order to ensure that the driving electrode 3 is completely covered by the organic resin material, the maximum thickness of the protective layer 8 needs to be greater than the thickness of the driving electrode 3.

[0064] The material and thickness selection of the driving electrode 3 in the embodiment of the present disclosure will be described in detail below with reference to specific examples.

[0065] Since the driving electrode 3 is used to load the signal, in order to avoid signal distortion, the square resistance of the driving electrode 3 is generally required to be less than 0.05Ω / □; in addition, for acoustic matching, the density of the driving electrode 3 is required to be greater than 5g / cm3. At this time, among the metal materials suitable for the electroplating process, silver, copper, and nickel meet the above requirements.

[0066] Taking the case where the material of the piezoelectric material layer 2 is PVDF and the thickness is about 9um, and the maximum distance between the surface of the substrate side away from the piezoelectric material layer 2 and the surface of the passivation layer 6 side close to the piezoelectric material layer 2 is about 90um as an example, when the fingerprint recognition unit works at 10MHZ, 11MHZ, 12MHZ, and 13MHZ, the driving electrode 3 is simulated by using the required thickness of different metal materials. The thickness of the driving electrode 3 can make the vibration node surface of the piezoelectric material layer 2 located within the piezoelectric material layer 2, as shown in Table 1 below.

[0067] Table 1. Corresponding film thickness required for driving electrodes of different materials at different operating frequencies

[0068]

[0069] Taking into consideration factors such as film forming process and production cost, the material of the driving electrode 3 is preferably copper, and the thickness is between 14 um and 45 um.

[0070] Figure 4 A top view schematic diagram of a fingerprint recognition module provided in an embodiment of the present disclosure, such as Figure 4 As shown, the fingerprint recognition module includes a plurality of fingerprint recognition units 9 arranged in an array, wherein the fingerprint recognition unit 9 adopts the fingerprint recognition unit provided in the above embodiment. The driving electrode in each fingerprint recognition unit 9 is connected to an external connection terminal (also called a pad, not shown) through a corresponding lead wire (not shown).

[0071] The embodiment of the present disclosure further provides a display device, which includes a fingerprint recognition module, wherein the fingerprint recognition module adopts the fingerprint recognition module provided in the above embodiment.

[0072] In some embodiments, the display device further comprises a display module, and the display module and the fingerprint recognition module are substantially the same size, so that full-screen fingerprint recognition can be achieved. In some embodiments, the fingerprint recognition module and the display module can be bonded and fixed by an adhesive layer.

[0073] The display device provided in the embodiments of the present disclosure may be an electronic device with a display function, such as a television, a mobile phone, a computer, a laptop computer, an electronic photo album, a navigator, etc.

[0074] Figure 5 A flowchart of a method for preparing a fingerprint recognition unit provided in an embodiment of the present disclosure is shown in FIG. Figure 5 As shown, the preparation method can be used to prepare the fingerprint recognition unit provided in the previous embodiment, comprising:

[0075] Step S101: forming a receiving electrode layer on a base substrate, wherein the receiving electrode layer comprises a plurality of receiving electrodes, and the plurality of receiving electrodes are arranged in an array along a first direction and a second direction.

[0076] In some embodiments, before forming the receiving electrode on the substrate, the method further includes: forming a fingerprint recognition circuit layer on the substrate. The fingerprint recognition circuit layer includes a thin film transistor, and the step of forming the fingerprint recognition circuit layer includes: forming a gate, forming an active layer, and forming a source / drain, which can be prepared by an existing thin film transistor preparation process.

[0077] In some embodiments, the thin film transistors in the fingerprint recognition circuit layer are complementary metal oxide semiconductor (CMOS) tubes. In this case, the fingerprint recognition circuit layer can be manufactured based on the CMOS tube manufacturing process.

[0078] It should be noted that after the preparation of the fingerprint recognition circuit layer is completed, a planarization layer can also be formed on the fingerprint recognition circuit layer to facilitate the preparation of subsequent structures. At this time, the receiving electrode is electrically connected to the corresponding fingerprint recognition circuit through the via hole on the planarization. For the convenience of description, the structure composed of the base substrate, the fingerprint recognition circuit layer and the planarization layer is called a carrier substrate.

[0079] Step S102: forming a piezoelectric material layer on a side of the receiving electrode away from the base substrate.

[0080] Step S103: forming a driving electrode layer with a certain thickness on a side of the piezoelectric material layer away from the receiving electrode layer by a metal electroplating process, wherein the driving electrode layer includes a plurality of driving electrodes arranged along a second direction, the driving electrodes are strip electrodes extending along a first direction and overlapping with a plurality of receiving electrodes arranged along the first direction, and the thickness of the driving electrodes is configured such that the vibration node surface of the piezoelectric material layer is located inside the piezoelectric material layer.

[0081] Based on the above steps S101 to S103, the fingerprint recognition unit provided in the previous embodiment can be prepared. In the technical solution disclosed in the present invention, the driving electrode can not only realize the function of fingerprint recognition driving, but also play the role of acoustic matching layer. Therefore, in the fingerprint recognition unit provided in the present invention, there is no need to additionally set an acoustic matching layer and an isolation layer, thereby simplifying the device structure and effectively avoiding breakdown short circuit between the driving electrode and the acoustic matching layer.

[0082] Figure 6 A flowchart of another method for preparing a fingerprint recognition unit provided in an embodiment of the present disclosure, Figures 7a to 7j To adopt Figure 6 The intermediate structure diagram of the fingerprint recognition unit prepared by the preparation method shown is as follows: Figures 6-7j As shown, the preparation method can be used to prepare the fingerprint recognition unit provided in the previous embodiment, comprising:

[0083] Step S201: prepare a carrier substrate.

[0084] See also Figure 7a As shown, for the specific description of preparing the carrier substrate 5, reference can be made to the corresponding content in the previous embodiment, which will not be repeated here.

[0085] Step S202: forming a receiving electrode layer on the carrier substrate.

[0086] See also Figure 7b As shown, the receiving electrode layer includes a plurality of receiving electrodes 1 , and the plurality of receiving electrodes 1 are arranged in an array along a first direction X and a second direction Y, and each receiving electrode 1 is electrically connected to a corresponding fingerprint recognition circuit in the carrier substrate 5 .

[0087] Step S203 : forming a passivation layer on a side of the receiving electrode layer away from the carrier substrate.

[0088] See also Figure 7c As shown, in step S203, a passivation material film is first formed by a deposition process, and the passivation material includes silicon nitride and / or silicon oxide; then the passivation material film is patterned to obtain a pattern of the passivation layer 6; wherein the passivation layer 6 is located between adjacent receiving electrodes 1 and on a side surface of the receiving electrode 1 away from the supporting substrate 5.

[0089] It should be noted that the patterning process in the present disclosure refers to a process that can form a desired pattern; wherein the patterning process generally includes a photolithography process, specifically including at least part of the processes of photoresist coating, exposure, masking, thin film etching, and photoresist stripping; of course, the patterning process may also include printing, printing and other processes.

[0090] Step S204 , forming a piezoelectric material layer on a side of the passivation layer away from the carrier substrate.

[0091] See also Figure 7d As shown, a piezoelectric material film is first formed; in some embodiments, the piezoelectric material includes PVDF; and then a patterning process is performed on the piezoelectric material film to obtain a pattern of the piezoelectric material layer 2.

[0092] In some embodiments, the pattern of the piezoelectric material layer 2 formed on the surface of the passivation layer 6 and the pattern of the passivation layer 6 have projections on the substrate that completely overlap, and the same mask plate can be used for both in the patterning process.

[0093] Step S205: forming a packaging pattern on the sides of the piezoelectric material layer and the passivation layer.

[0094] See also Figure 7e As shown, a packaging material film is first formed, wherein the packaging material includes photoresist; then the packaging material film is patterned to obtain a packaging pattern 7. In some embodiments, the packaging pattern 7 also covers the edge area of ​​the upper surface of the piezoelectric material layer 2 to achieve a better packaging effect.

[0095] In some embodiments, the side surface of the packaging pattern 7 away from the piezoelectric material layer 2 is a slope surface, and the angle between the slope surface and the plane where the side surface of the piezoelectric material layer 2 is located is 30° to 60°.

[0096] Step S206 , forming a driving electrode layer on a side of the piezoelectric material layer away from the carrier substrate.

[0097] Figure 8 FIG. 1 is a flow chart of a specific method for forming a driving electrode layer in an embodiment of the present disclosure. Figure 8 As shown, step S206 includes:

[0098] Step S2061 : electroplating a metal film as a seed layer on the entire surface of the side of the piezoelectric material layer away from the substrate through an electroplating process.

[0099] See also Figure 7f As shown, in some embodiments, the material of the seed layer 3a is copper, and the thickness of the seed layer 3a includes:

[0100] Step S2062: forming a barrier layer on the seed layer.

[0101] See also Figure 7g As shown, the area on the retaining wall layer 10 where the driving electrode 3 is to be formed is a hollow structure 11 .

[0102] In some embodiments, the width of the retaining wall layer between adjacent hollow structures 11 is less than or equal to the width between the pre-designed driving electrodes 3. Exemplarily, the width between the pre-designed driving electrodes 3 is 8um to 10um, and the width of the retaining wall layer between adjacent hollow structures is 1um to 7um. The thickness of the retaining wall layer is greater than the thickness of the driving electrode 3 to be formed.

[0103] Step S2063: electroplating a metal film in the hollow structure through an electroplating process, and the metal film in the hollow structure is a growth layer pattern.

[0104] See also Figure 7h As shown, the metal material electroplated in step S2063 is the same as the metal material electroplated in step S2061. In some embodiments, the metal materials electroplated in step S2063 and step S2061 are both copper. The thickness of the growth layer pattern 3b in step S2063 is determined by actual needs.

[0105] Step S2064, removing the retaining wall layer.

[0106] See also Figure 7i As shown, the solvent dissolves the barrier layer so that the area on the seed layer 3a not covered by the growth layer pattern 3b is exposed.

[0107] Step S2065: thinning and etching each growth layer pattern and the seed layer simultaneously.

[0108] See also Figure 7j As shown, the growth layer pattern and the seed layer are thinned and etched simultaneously by a dry etching process, the portion of the seed layer not covered by the growth layer pattern is completely removed, part of the material on the upper surface and side of the growth layer pattern is removed, and the retained portion of the growth layer pattern and the portion of the seed layer covered by the retained portion constitute the driving electrode 3.

[0109] It should be noted that, in the process of simultaneously thinning the growth layer pattern and the seed layer, since the side of the growth layer pattern will also be etched, the cross-sectional area of ​​the growth layer pattern will be reduced, and the spacing between adjacent growth layer patterns will be increased. Therefore, when designing the retaining wall layer 10 in step S2062 and the hollow structure 11 on the retaining wall layer 10, the area where the hollow structure is located can be made as large as possible as the area where the drive electrode 3 is to be formed, and the width of the retaining wall layer between adjacent hollow structures 11 is smaller than the width between the pre-designed drive electrodes 3, so as to reduce the error between the size of the product generated by the final production line and the designed size.

[0110] In some embodiments, the material of the driving electrode 3 is copper, and the thickness of the driving electrode 3 is between 14 um and 45 um.

[0111] Based on the above steps S2061 to S2065, the preparation of the driving electrode 3 can be completed. Of course, the step S103 in the previous embodiment can also be implemented by using the steps S2061 to S2065.

[0112] Step S207 , forming a protection layer on a side of the driving electrode layer away from the carrying substrate.

[0113] See also Figure 2 As shown, the protection layer 8 and the packaging pattern 7 can protect the fingerprint recognition unit.

[0114] Based on the above steps S201 to S207, the fingerprint recognition unit provided in the previous embodiment can be prepared. In the technical solution disclosed in the present invention, the driving electrode can not only realize the function of fingerprint recognition driving, but also play the role of acoustic matching layer. Therefore, in the fingerprint recognition unit provided in the present invention, there is no need to additionally set an acoustic matching layer and an isolation layer, thereby simplifying the device structure and effectively avoiding breakdown short circuit between the driving electrode and the acoustic matching layer.

[0115] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A fingerprint recognition unit, wherein: include: The receiving electrode layer includes a plurality of receiving electrodes, wherein the plurality of receiving electrodes are arranged in an array along a first direction and a second direction. A piezoelectric material layer, arranged on one side of the receiving electrode layer; A driving electrode layer, arranged on a side of the piezoelectric material layer away from the receiving electrode layer, comprising: a plurality of driving electrodes arranged along the second direction, the driving electrodes being strip electrodes extending along the first direction and overlapping with the plurality of receiving electrodes arranged along the first direction; The material of the driving electrode includes a metal material suitable for an electroplating process, and the thickness of the driving electrode is configured so that the vibration node surface of the piezoelectric material layer is located inside the piezoelectric material layer.

2. The fingerprint recognition unit according to claim 1, wherein: The material of the driving electrode includes copper, and the thickness of the driving electrode includes 14 um to 45 um.

3. The fingerprint recognition unit according to claim 1, wherein: Also includes: A base substrate and a fingerprint recognition circuit layer located on the base substrate, wherein the receiving electrode layer is located on a side of the fingerprint recognition circuit layer away from the base substrate; The fingerprint recognition circuit includes a plurality of fingerprint recognition circuits corresponding to the receiving electrodes one by one, and the fingerprint recognition circuits are electrically connected to the corresponding receiving electrodes.

4. The fingerprint recognition unit according to claim 3, wherein: A passivation layer is arranged between adjacent receiving electrodes and between the receiving electrodes and the piezoelectric material layer.

5. The fingerprint recognition unit according to claim 4, wherein: The maximum distance between a surface of the substrate far from the piezoelectric material layer and a surface of the passivation layer close to the piezoelectric material layer is 80 um to 100 um.

6. The fingerprint recognition unit according to claim 1, wherein: The material of the piezoelectric material layer includes: polyvinylidene fluoride; The thickness of the piezoelectric material layer is 8um to 10um.

7. The fingerprint recognition unit according to claim 1, wherein: Also includes: A packaging pattern covers the side surface of the piezoelectric material layer.

8. The fingerprint recognition unit according to claim 7, wherein: The side of the packaging pattern away from the piezoelectric material layer is a sloped surface, and the angle between the sloped surface and the plane where the side of the piezoelectric material layer is located is 30° to 60°.

9. The fingerprint recognition unit according to claim 1, wherein: Also includes: A protection layer is located on a side of the driving electrode away from the piezoelectric material layer.

10. The fingerprint recognition unit according to claim 9, wherein: The material of the protection layer includes an organic resin material, and the maximum thickness of the protection layer is greater than the thickness of the driving electrode.

11. The fingerprint recognition unit according to claim 1, wherein: The width of the driving electrode includes: 65um-70um, and the spacing between adjacent driving electrodes includes: 8um-10um; The receiving electrode is a rectangular electrode, the length of any side of the rectangular electrode is 65 to 70 um, and the spacing between adjacent rectangular electrodes is 8 to 10 um.

12. A fingerprint recognition module, wherein: include: A plurality of fingerprint recognition units are arranged in an array, wherein the fingerprint recognition unit is a fingerprint recognition unit as described in any one of claims 1 to 11.

13. A display device, wherein: include: A fingerprint recognition module as described in claim 12 above.

14. A method for preparing a fingerprint recognition unit as claimed in any one of claims 1 to 11, wherein: include: A receiving electrode layer is formed on the base substrate, wherein the receiving electrode layer comprises a plurality of receiving electrodes, and the plurality of receiving electrodes are arranged in an array along a first direction and a second direction; forming a piezoelectric material layer on a side of the receiving electrode layer away from the substrate; A driving electrode layer is formed on a side of the piezoelectric material layer away from the receiving electrode layer by a metal electroplating process, the driving electrode layer includes a plurality of driving electrodes arranged along a second direction, the driving electrodes are strip electrodes extending along the first direction and overlap with a plurality of receiving electrodes arranged along the first direction, and the thickness of the driving electrodes is configured so that the vibration node surface of the piezoelectric material layer is located inside the piezoelectric material layer.

15. The preparation method according to claim 14, wherein: The step of forming a driving electrode layer on a side of the piezoelectric material layer away from the receiving electrode layer by a metal electroplating process comprises: A copper film is electroplated on the entire surface of the piezoelectric material layer away from the substrate substrate by an electroplating process to serve as a seed layer, wherein the thickness of the seed layer comprises: forming a retaining wall layer on the seed layer, wherein the region of the retaining wall layer where the driving electrode is to be formed is a hollow structure, and the thickness of the retaining wall layer is greater than the thickness of the driving electrode to be formed; Electroplating a copper film in the hollow structure by an electroplating process, wherein the copper film in the hollow structure is a growth layer pattern; removing the retaining wall layer; The growth layer patterns and the seed layer are thinned and etched simultaneously, the portion of the seed layer not covered by the growth layer pattern is completely removed, and the remaining portion of the growth layer pattern and the portion of the seed layer covered by the remaining portion constitute the driving electrode.

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