Patent Description:
The embodiments of the present disclosure relate to a fingerprint identification module, a manufacturing method of the fingerprint identification module and an electronic device.

With the continuous development of science and technology, fingerprint identification technology has been gradually applied to people's daily life. Fingerprint identification technology can identify different fingerprints by comparing their detailed feature points, so as to achieve the function of identity recognition. Generally, fingerprint identification technology can be divided into optical fingerprint identification technology, silicon chip fingerprint identification technology and ultrasonic fingerprint identification technology.

At present, the ultrasonic fingerprint identification technology is a hot research direction of major manufacturers. An ultrasonic fingerprint identification structure is mainly a three-layer structure, which includes first driving electrodes, receiving electrodes and a piezoelectric layer between the first driving electrodes and the receiving electrodes. In the case that a driving voltage is applied to the first driving electrodes and the receiving electrodes, the piezoelectric layer is excited by the voltage to generate an inverse piezoelectric effect to send a first ultrasonic wave outward. The first ultrasonic wave contacts a finger and is reflected back by the finger to form second ultrasonic waves. Because the fingerprint includes valleys and ridges, vibration intensities of the second ultrasonic waves reflected by different positions of the fingerprint back to the piezoelectric layer are different. At this time, in the case that a fixed voltage is applied to the first driving electrodes, the piezoelectric layer can convert the second ultrasonic waves into voltage signals, which are transmitted to a fingerprint identification module through the receiving electrodes, and positions of the valleys and ridges in the fingerprint can be judged according to the voltage signals.

<CIT> discloses an acoustic fingerprint scanning device, in which an ultrasound transducer (XDC) emits an ultrasound wave that is reflected at the surface-finger interface and also from within the finger. The transducer can transmit an ultrasound signal having a frequency in a range from <NUM> to <NUM>. An acoustic fingerprint scanner scans the interface between the finger and the medium it touches. The medium can be rigid. Where the ridges of the finger touch the surface, part of the acoustic wave will enter the finger and less energy will be reflected via reflection. At locations where there is a valley of the finger, relatively more (for example, practically all of) the acoustic energy is reflected back to the ultrasound transducer as reflection. This contrast of reflection coefficients associated with ridges and valleys can be used by the device to scan the finger surface.

<CIT> discloses a semiconductor element provided in a semiconductor device includes a built-in contact sensor having a sensor region formed on a circuit forming surface. The connection terminal is provided in an area other than the sensor area. The wiring board is connected to the connection terminal of the semiconductor element so that the end face of the wiring board is located on the circuit formation surface. The protective resin partially covers the portion extending from the end face of the wiring board to the circuit formation surface, so as to protect the connection portion between the semiconductor element and the wiring board. When the semiconductor chip <NUM> is connected to the flexible board <NUM>, the amount of the anisotropic conductive resin <NUM> filled between the semiconductor chip <NUM> and the flexible board <NUM> is such that the anisotropic conductive resin <NUM> protrudes to cover the end face 6a of the base material <NUM> of the flexible board <NUM>. Thereby, the end of the flexible board <NUM> is reinforced by the anisotropic conductive resin <NUM>, which prevents the end of the flexible board <NUM> from being separated from the semiconductor chip <NUM>.

It is an object of the present invention to provide an advantageous fingerprint identification module, an advantageous manufacturing method of the fingerprint identification module, and an advantageous electronic device. The object is achieved by the features of the respective independent claims. Further embodiments are defined by the respective dependent claims.

In order to clearly illustrate the technical solution of the embodiments of the disclosure, the drawings of the embodiments will be briefly described in the following; it is obvious that the described drawings are only related to some embodiments of the disclosure and thus are not limitative of the disclosure.

Unless otherwise defined, all the technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. The terms "first," "second," etc., which are used in the description and the claims of the present application for disclosure, are not intended to indicate any sequence, amount or importance, but distinguish various components. The terms "comprise," "comprising," "include," "including," etc., are intended to specify that the elements or the objects stated before these terms encompass the elements or the objects and equivalents thereof listed after these terms, but do not preclude the other elements or objects. The phrases "connect", "connected", etc., are not intended to define a physical connection or mechanical connection, but may include an electrical connection, directly or indirectly. "On," "under," "right," "left" and the like are only used to indicate relative position relationship, and when the position of the object which is described is changed, the relative position relationship may be changed accordingly.

<FIG> is a schematic diagram showing that a fingerprint identification module sending an ultrasonic wave; <FIG> is a schematic diagram showing that the fingerprint identification module receives an ultrasonic wave. As shown in <FIG>, the fingerprint identification module includes an ultrasonic sensor <NUM>; the ultrasonic sensor <NUM> includes an upper electrode <NUM>, a lower electrode <NUM> and a piezoelectric layer <NUM> located between the upper electrode <NUM> and the lower electrode <NUM>. The piezoelectric layer <NUM> is made of piezoelectric material and can be excited by a voltage to produce inverse piezoelectric effect. As shown in <FIG>, in the case that an alternating voltage (AC voltage) is input to the upper electrode <NUM> and the lower electrode <NUM> (for example, the upper electrode <NUM> is grounded and an alternating square wave is applied to the lower electrode <NUM>), the piezoelectric layer <NUM> deforms due to the inverse piezoelectric effect or drives the films above and below the piezoelectric layer <NUM> to vibrate together, so that an ultrasonic wave can be generated and emitted outward. It should be noted that in the case that a cavity (e.g., an air cavity) is provided on the side of the upper electrode <NUM> away from the piezoelectric layer <NUM> or the side of the lower electrode <NUM> away from the piezoelectric layer <NUM>, the ultrasonic wave emitted by the ultrasonic sensor is enhanced, so that the ultrasonic wave can be better emitted.

As shown in <FIG>, the ultrasonic wave emitted by the ultrasonic sensor <NUM> is reflected by a fingerprint <NUM>, and the reflected ultrasonic wave is converted into an alternating voltage in the piezoelectric layer; at this time, the upper electrode <NUM> is grounded, and the lower electrode <NUM> can be used as a receiving electrode to receive the alternating voltage generated by the piezoelectric layer. The fingerprint <NUM> includes valleys <NUM> and ridges <NUM>, and the valley <NUM> and the ridge <NUM> have different reflection capabilities for the ultrasonic wave (the valley <NUM> has a stronger reflection capability for the ultrasonic wave), resulting in different intensities of the ultrasonic wave reflected by the valley <NUM> and the ultrasonic wave reflected by the ridge <NUM>. Therefore, it can be judged from the alternating voltage received by the receiving electrode whether the ultrasonic wave is reflected by the valley or the ridge.

<FIG> is a schematic diagram showing that fingerprint recognition is performed by the fingerprint identification module. As shown in <FIG>, the fingerprint identification module includes an upper electrode <NUM>, a plurality of lower electrodes <NUM>, a piezoelectric layer <NUM> between the upper electrode <NUM> and the plurality of lower electrodes <NUM>, a substrate <NUM> on one side of the upper electrode <NUM> away from the piezoelectric layer <NUM>, and a protective layer <NUM> on one side of the plurality of lower electrodes <NUM> away from the piezoelectric layer <NUM>. The ultrasonic sensor <NUM> formed by the plurality of lower electrodes <NUM>, the piezoelectric layer <NUM> and the upper electrode <NUM> can transmit and receive the ultrasonic wave, that is, the ultrasonic sensor <NUM> serves as both an ultrasonic transmitting sensor and an ultrasonic receiving sensor. In the case that the fingerprint is in contact with the substrate <NUM>, the ultrasonic wave transmitted by the ultrasonic sensor <NUM> is reflected by the fingerprint <NUM>, and the reflected ultrasonic wave is converted into an alternating voltage in the piezoelectric layer. At this time, the upper electrode <NUM> is grounded, and the plurality of lower electrodes <NUM> can be used as receiving electrodes, so that the alternating voltage generated by the piezoelectric layer can be received at different positions. The fingerprint <NUM> includes valleys <NUM> and ridges <NUM>, which have different reflection capabilities for the ultrasonic wave (the valleys <NUM> have stronger reflection capabilities for the ultrasonic wave), resulting in different intensities of ultrasonic waves reflected by the valleys <NUM> and the ridges <NUM>. Therefore, the position information of the valleys and the ridges in the fingerprint <NUM> can be obtained by the alternating voltage received by the plurality of lower electrodes <NUM>, so that fingerprint recognition can be realized.

<FIG> is a schematic structural diagram of the fingerprint identification module. As shown in <FIG>, the fingerprint identification module includes a substrate <NUM>, a CMOS (Complementary Metal Oxide Semiconductor) backplane <NUM>, a piezoelectric layer <NUM>, a plurality of first driving electrodes <NUM> and an acoustic wave reflection layer <NUM>. The CMOS backplane <NUM> may include the receiving electrodes and corresponding driving units. In the research, the inventor(s) of this application noticed that in a manufacturing process of the fingerprint identification module, it is necessary to form a conductive layer on the side of the piezoelectric layer away from the CMOS backplane, then form a photoresist pattern on the side of the conductive layer away from the piezoelectric layer, and finally etch the conductive layer with the photoresist pattern as a mask to form the plurality of first driving electrodes. <FIG> is a scanning electron microscope image of the piezoelectric layer in the fingerprint identification module; <FIG> is a scanning electron microscope image of the photoresist pattern on the conductive layer in the fingerprint identification module; <FIG> is a scanning electron microscope image of the plurality of first driving electrodes on the piezoelectric layer in the fingerprint identification module. As shown in <FIG>, because a slope of an edge of the piezoelectric layer is large (about <NUM> degrees), defects such as disconnection (PR (photoresist) disconnection) and photoresist residue (PR residue) are easily generated at the edge of the piezoelectric layer in the process (exposure and development processes) of forming the photoresist pattern. As shown in <FIG>, due to the large slope (about <NUM> degrees) of the edge of the piezoelectric layer and the defects such as the disconnection and the photoresist residue caused by the photoresist pattern, disconnection (Tx disconnection) of a plurality of strip-shaped driving electrodes formed by the conductive layer or residual conductive material formed by the conductive layer (Tx residue) may occur at the edge of the piezoelectric layer in the subsequent etching process, resulting in various defects.

Therefore, the embodiments of the disclosure provide a fingerprint identification module, a manufacturing method of the fingerprint identification module and an electronic device. The fingerprint identification module includes a substrate, a piezoelectric material layer, an auxiliary structure and a plurality of first driving electrodes; the piezoelectric material layer is located on the substrate, the auxiliary structure is at least partially located on the substrate, and the plurality of first driving electrodes are located on one side of the piezoelectric material layer and the auxiliary structure away from the substrate; each first driving electrode extends along a first direction and exceeds a first edge of the piezoelectric material layer in the first direction; the plurality of first driving electrodes are arranged at intervals along a second direction; the auxiliary structure is at least in contact with the first edge; the auxiliary structure includes a slope portion; a thickness of the slope portion in a direction perpendicular to the functional substrate gradually decreases in a direction from the first edge to a position away from a center of the piezoelectric material layer; and the second direction intersects with the first direction. In the fingerprint identification module, because the auxiliary structure is in contact with the first edge of the piezoelectric material layer and includes the slope portion, problems such as disconnection and conductive material residue can be avoided in the process of forming the plurality of first driving electrodes on the piezoelectric material layer, thereby improving the yield of products.

The fingerprint identification module, the manufacturing method of the fingerprint identification module and the electronic device provided by the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

An embodiment of the present disclosure provides a fingerprint identification module. <FIG> is a schematic cross-sectional view along the first direction of the fingerprint identification module according to an embodiment of the present disclosure; <FIG> is a schematic cross-sectional view along the second direction of the fingerprint identification module according to an embodiment of the present disclosure. As shown in <FIG>, the fingerprint identification module <NUM> includes the functional substrate <NUM>, the piezoelectric material layer <NUM>, the auxiliary structure <NUM> and the plurality of first driving electrodes <NUM>. The piezoelectric material layer <NUM> is located on the functional substrate <NUM>, and the auxiliary structure <NUM> is at least partially located on the functional substrate <NUM>. The plurality of first driving electrodes <NUM> are located on the side of the piezoelectric material layer <NUM> and the auxiliary structure <NUM> away from the functional substrate <NUM>. As shown in <FIG>, each first driving electrode <NUM> extends along the first direction and exceeds the first edge <NUM> of the piezoelectric material layer <NUM> in the first direction, that is, each first driving electrode <NUM> goes beyond the first edge <NUM> of the piezoelectric material layer <NUM> in the first direction; as shown in <FIG>, the plurality of first driving electrodes <NUM> are arranged at intervals along the second direction and insulated from each other. As shown in <FIG>, the auxiliary structure <NUM> is at least in contact with the first edge <NUM>, and includes a slope portion <NUM>; in the direction from the first edge <NUM> to a position away from the center of the piezoelectric material layer <NUM>, a thickness of the slope portion <NUM> in the direction perpendicular to the functional substrate <NUM> gradually decreases, and the second direction intersects with the first direction. It should be noted that the first edge of the piezoelectric material layer in the first direction means that an extending direction of the first edge intersects with the first direction, rather than that the extending direction of the first edge is parallel to the first direction.

In the fingerprint identification module provided by the embodiments of the present disclosure, because the auxiliary structure is at least in contact with the first edge, the first driving electrode extending in the first direction and exceeding the first edge extends from the piezoelectric material layer to the auxiliary structure instead of directly extending from the piezoelectric material layer to the functional substrate; in addition, the auxiliary structure includes the slope portion, and the thickness of the slope portion gradually decreases from the first edge to the direction away from the center of the piezoelectric material layer. Therefore, in the process of forming the plurality of first driving electrodes on the piezoelectric material layer, the photoresist can be fully exposed and developed at the first edge, so that the problem of disconnection of the conductive layer in the subsequent etching process can be effectively avoided, and the problem of residual conductive material can also be avoided, so that adjacent two first driving electrodes are prevented from being electrically connected, and the yield of products can be improved.

In some examples, the first direction and the second direction are perpendicular to each other. In some examples, as shown in <FIG>, a slope angle θ of the slope portion <NUM> is less than <NUM> degrees. With this arrangement, problems such as disconnection and conductive material residue in the process of forming the plurality of first driving electrodes can be better avoided.

In some examples, as shown in <FIG>, the auxiliary structure <NUM> includes a main body portion <NUM> and an overlapping portion <NUM>; the main body portion <NUM> is located on the functional substrate <NUM>, and the main body portion <NUM> is in the same layer as the piezoelectric material layer <NUM>. The overlapping portion <NUM> is connected to the main body portion <NUM> and is located on the side of the first edge <NUM> of the piezoelectric material layer <NUM> away from the functional substrate <NUM>. With this arrangement, the auxiliary structure can prevent the piezoelectric material layer from falling off in the manufacturing and using processes by fixing the piezoelectric material layer on the functional substrate through the overlapping portion while avoiding the problems such as disconnection and conductive material residue in the forming process of the first driving electrode.

In some examples, the material of the piezoelectric material layer includes polyvinylidene fluoride (PVDF). Because polyvinylidene fluoride is a fluorine-containing material, its adhesion to the functional substrate (such as a silicon nitride layer) is poor, which leads to the piezoelectric material layer falling off easily. Therefore, by arranging the overlapping portion, the fingerprint identification module can effectively avoid and prevent the piezoelectric material layer from falling off in the manufacturing and using processes. On the other hand, in the process of stripping the photoresist pattern (PR), compositions of a stripping liquid of the photoresist pattern usually include N-methyl formamide (NMF) and diethylene glycol monomethyl ether, and the polyvinylidene fluoride is dissolved in N-methyl formamide and ethers. Therefore, on the one hand, the above auxiliary structure can protect the edge of the piezoelectric material layer in the process of stripping the photoresist pattern (PR), preventing the stripping liquid of the photoresist pattern from corroding the piezoelectric material layer, thereby avoiding the falling off of the piezoelectric material layer; on the other hand, the overlapping portion of the auxiliary structure can fix the piezoelectric material layer on the functional substrate, thereby further preventing the piezoelectric material layer from falling off in the manufacturing and using processes.

For example, as shown in <FIG>, the main body portion <NUM> includes the slope portion <NUM> described above. That is, the slope portion <NUM> is a part of the main body portion <NUM>.

In some examples, a size of the overlapping portion <NUM> in the first direction is greater than <NUM> microns. According to experimental results, in the case that the size of the overlapping portion in the first direction is larger than <NUM> microns, the auxiliary structure can effectively prevent the piezoelectric material layer from falling off in the manufacturing and using processes. For example, the size of the overlapping portion in the first direction may be <NUM>, <NUM>, <NUM>, <NUM> or <NUM> microns.

In some examples, the material of the auxiliary structure includes curing adhesive. Therefore, in the process of forming the auxiliary structure, after coating the curing adhesive and before curing the auxiliary structure, the curing adhesive undergoes a leveling process due to its certain fluidity or ductility, thus naturally forming the above-mentioned slope portion, thus eliminating the need for an additional process step, thus reducing the manufacturing difficulty and cost. For example, in the case that the curing adhesive is used for the auxiliary structure, the slope angle of the formed slope portion is about <NUM> degrees.

In some examples, the material of the auxiliary structure includes an optical curing adhesive (OC adhesive). Therefore, the auxiliary structure can be directly patterned by an exposure process without using a mask process, thereby further reducing the manufacturing cost. For example, the material of the auxiliary structure may be an acrylate system material.

In some examples, as shown in <FIG>, the fingerprint identification module <NUM> further includes a first insulating layer <NUM> and an acoustic wave reflective layer <NUM>; the first insulating layer <NUM> is located on one side of the plurality of first driving electrodes <NUM> away from the functional substrate <NUM>. The acoustic wave reflective layer <NUM> is located on one side of the first insulating layer <NUM> away from the plurality of first driving electrodes <NUM>, and an orthographic projection of the acoustic wave reflective layer <NUM> on the functional substrate <NUM> is overlapped with an orthographic projection of the piezoelectric material layer <NUM> on the functional substrate <NUM>. With this arrangement, the acoustic wave reflective layer <NUM> can reflect the ultrasonic wave which is generated by the piezoelectric material layer <NUM> and which propagates to the acoustic wave reflective layer <NUM> to a position where the functional substrate <NUM> is located, thereby being beneficial to enhancing the intensity or energy of the transmitted ultrasonic wave.

For example, the acoustic wave reflective layer <NUM> may be made of silver (Ag), and the first insulating layer <NUM> may be made of silicon nitride (SiNx). Of course, the embodiments of the present disclosure include but are not limited to this. The acoustic wave reflective layer can also be made of other materials with the characteristic of reflecting the ultrasonic wave, and the first insulating layer can also be made of other insulating materials such as resin.

In some examples, as shown in <FIG>, the functional substrate <NUM> includes a receiving electrode layer <NUM>, a driving circuit layer <NUM> and a substrate <NUM>; the receiving electrode layer <NUM> is located on one side of the piezoelectric material layer <NUM> close to the substrate <NUM> and includes a plurality of receiving electrodes <NUM>. The driving circuit layer <NUM> is located on one side of the receiving electrode layer <NUM> close to the substrate <NUM> and includes a plurality of driving units <NUM>, the plurality of receiving electrodes <NUM> are arranged in one-to-one correspondence with the plurality of driving units <NUM> and the plurality of driving units <NUM> are configured to drive the plurality of receiving electrodes <NUM> to receive electrical signals generated by the piezoelectric material layer <NUM>. Orthographic projections of the plurality of receiving electrodes <NUM> on the substrate <NUM> at least partially overlap with the orthographic projection of the piezoelectric material layer <NUM> on the substrate <NUM>; the orthographic projections of the plurality of receiving electrodes <NUM> on the substrate <NUM> at least partially overlap with the orthographic projections of the plurality of first driving electrodes <NUM> on the substrate <NUM>, so that a plurality of ultrasonic receiving elements can be formed by the plurality of receiving electrodes <NUM>, the first driving electrodes <NUM> and the piezoelectric material layer <NUM>.

For example, as shown in <FIG>, an insulating layer is provided between the plurality of receiving electrodes <NUM> to ensure that the plurality of receiving electrodes <NUM> are mutual insulated from each other; similarly, an insulating layer is provided between the plurality of driving units <NUM> so that the plurality of driving units <NUM> are insulated from each other.

In the fingerprint identification module provided in this embodiment, the plurality of first driving electrodes arranged on the piezoelectric material layer, the piezoelectric material layer and the plurality of receiving electrodes may constitute a plurality of ultrasonic transmitting elements; the plurality of receiving electrodes, the piezoelectric material layer and the plurality of first driving electrodes may constitute a plurality of ultrasonic receiving elements. In the case that the fingerprint identification module is used for fingerprint identification, the plurality of receiving electrodes can be grounded, and then an alternating voltage is respectively applied to the plurality of first driving electrodes, and portions of the piezoelectric material layer which are respectively corresponding to the first driving electrodes are deformed or drive the films above and below the piezoelectric material layer to vibrate together due to the inverse piezoelectric effect, so that the ultrasonic wave can be generated and transmitted outwards. A first driving electrode layer of the fingerprint identification module includes the plurality of first driving electrodes, and the plurality of ultrasonic transmitting elements can be formed, so that ultrasonic focusing can be realized by respectively driving the plurality of first driving electrodes. On one hand, the intensity or energy of the transmitted ultrasonic wave in a specific region or a specific direction can be improved, thereby improving the fingerprint identification performance; on the other hand, the transmitted ultrasonic wave has better directionality, thereby reducing the crosstalk between valleys and ridges of the fingerprint, and further improving the fingerprint identification performance. In the case that the transmitted ultrasonic wave is reflected back to the fingerprint identification module by the fingerprint, the plurality of ultrasonic receiving elements corresponding to the plurality of receiving electrodes can receive the reflected ultrasonic wave and convert a signal of the ultrasonic wave into electrical signals, thereby realizing fingerprint identification. In addition, in the case that the fingerprint identification module improves the intensity or energy of the transmitted ultrasonic wave in a specific region or a specific direction by focusing the ultrasonic wave, the fingerprint identification module can not only realize fingerprint identification, but also can penetrate a finger to distinguish whether the fingerprint is real skin or not.

In some examples, as shown in <FIG>, the receiving electrode <NUM> may be in contact with the piezoelectric material layer <NUM> so as to better receive the electrical signals. Of course, embodiments of the present disclosure include but are not limited to this.

<FIG> is another schematic cross-sectional view along the second direction of the fingerprint identification module provided according to an embodiment of the present disclosure. As shown in <FIG>, the functional substrate <NUM> further includes a second insulating layer <NUM> located between the receiving electrode layer <NUM> and the piezoelectric material layer <NUM>. The second insulating layer <NUM> can reduce the influence that the leakage current generated by the piezoelectric material layer <NUM> during polarization has on the thin film transistor in the driving unit <NUM> connected to the receiving electrode <NUM>. For example, the second insulating layer can also be made of silicon nitride (SiNx).

In some examples, the substrate <NUM> includes a glass substrate.

In some examples, the substrate <NUM> includes a polyimide substrate. Therefore, the substrate <NUM> can be made thinner, and the thickness of the substrate <NUM> ranges from <NUM> to <NUM> microns. It should be noted that in the case that the substrate <NUM> is a polyimide substrate, a polyimide layer can be formed on the glass substrate first, then layer structures such as the receiving electrode layer, the piezoelectric material layer and the first driving electrode layer can be formed on the polyimide layer, and finally the glass substrate is removed, thus obtaining the fingerprint identification module described in this example.

<FIG> is a schematic plan view of the fingerprint identification module according to an embodiment of the present disclosure. As shown in <FIG>, the auxiliary structure <NUM> is arranged along the edge of the piezoelectric material layer <NUM>, and the auxiliary structure <NUM> is also in contact with a second edge <NUM> of the piezoelectric material layer <NUM> in the second direction. With this arrangement, the auxiliary structure can protect the edges of the piezoelectric material layer in all directions in the process of stripping off the photoresist pattern (PR), so as to better prevent the stripping liquid of the photoresist pattern from corroding the piezoelectric material layer, thereby better avoiding the falling off of the piezoelectric material layer. Of course, the embodiments of the present disclosure include but are not limited to this, and the auxiliary structure may also be provided only at the first edge of the piezoelectric material layer along the first direction. It should be noted that the second edge of the piezoelectric material layer in the second direction means that an extending direction of the second edge intersects with the second direction, rather than that the extending direction of the second edge is parallel to the second direction.

For example, as shown in <FIG>, the shape of the orthographic projection of the piezoelectric material layer <NUM> on the functional substrate <NUM> may include a rectangle, such as a square. The auxiliary structure <NUM> is disposed along four edges of the piezoelectric material layer <NUM>. Of course, the embodiments of this disclosure include but are not limited to this, and the shape of the piezoelectric material layer can be set according to actual needs; the auxiliary structure may also be provided only at the first edge of the piezoelectric material layer in the first direction.

<FIG> is another schematic structural diagram of the fingerprint identification module provided according to an embodiment of the present disclosure. As shown in <FIG>, each of the first driving electrodes <NUM> includes a metal layer <NUM> and a transparent metal oxide layer <NUM> which are sequentially stacked in the direction perpendicular to the functional substrate. The compositions of the stripping liquid of the photoresist pattern usually include N-methyl formamide (NMF) and diethylene glycol monomethyl ether, and polyvinylidene fluoride is dissolved in N-methyl formamide and ethers. Therefore, the transparent metal oxide layer can be used as a mask in the process of forming the first driving electrodes, thereby preventing the stripping liquid of the photoresist pattern from corroding the piezoelectric material layer. It should be noted that the common etching solution of the transparent metal oxide layer cannot etch the metal layer, and the etching solution of the metal layer cannot etch the transparent metal oxide layer, so the transparent metal oxide layer can be used as a mask to etch the metal layer.

Next, this will be explained through the specific manufacturing process of the first driving electrodes. For example, forming the plurality of first driving electrodes on the side of the piezoelectric material layer and the auxiliary structure away from the functional substrate includes the following steps: forming the metal layer on the side of the piezoelectric material layer and the auxiliary structure away from the functional substrate; forming the transparent metal oxide layer on the side of the metal layer away from the piezoelectric material layer; forming the photoresist pattern on the side of the transparent metal oxide layer away from the metal layer, and patterning the transparent metal oxide layer with the photoresist pattern as a mask to form the plurality of strip-shaped transparent metal oxides; stripping the photoresist pattern; and forming the plurality of first driving electrodes by etching the metal layer with the plurality of strip-shaped transparent metal oxides as a mask. It can be seen that in the above manufacturing process, in stripping the photoresist pattern, the metal layer still covers the piezoelectric material layer, and thus can avoid the contact between the stripping liquid and the piezoelectric material layer. Therefore, the stripping liquid of the photoresist pattern can be prevented from corroding the piezoelectric material layer.

For example, the transparent metal oxide may include indium tin oxide (ITO). Of course, the embodiments of the present disclosure include but are not limited to this, and the above-mentioned transparent metal oxide can also be other specific materials.

In some examples, the thickness of the transparent metal oxide layer ranges from <NUM> to <NUM>Å. Because the piezoelectric material layer is usually a porous material with rough surface, leading to a phenomenon that a surface of the metal layer is uneven, in this way, the transparent metal oxide layer can better cover the metal layer.

<FIG> is another schematic structural diagram of the fingerprint identification module provided according to an embodiment of the present disclosure. As shown in <FIG>, the fingerprint identification module <NUM> includes the functional substrate <NUM>, the piezoelectric material layer <NUM>, the auxiliary structure <NUM> and the plurality of first driving electrodes <NUM>. The piezoelectric material layer <NUM> is located on the functional substrate <NUM>, and the auxiliary structure <NUM> is at least partially located on the functional substrate <NUM>. The plurality of first driving electrodes <NUM> are located on the side of the piezoelectric material layer <NUM> and the auxiliary structure <NUM> away from the functional substrate <NUM>. Each first driving electrode <NUM> extends along the first direction and exceeds the first edge <NUM> of the piezoelectric material layer <NUM> in the first direction. The plurality of first driving electrodes <NUM> are arranged at intervals along the second direction, and the plurality of first driving electrodes <NUM> are insulated from each other. The auxiliary structure <NUM> is in contact with the first edge <NUM> and includes the slope portion <NUM>; in the direction from the first edge <NUM> to a position away from the center of the piezoelectric material layer <NUM>, the thickness of the slope portion <NUM> in the direction perpendicular to the functional substrate <NUM> gradually decreases. As shown in <FIG>, the auxiliary structure <NUM> only includes the main body portion <NUM> located on the functional substrate <NUM> and disposed in the same layer as the piezoelectric material layer <NUM>, and does not include the overlapping portion <NUM>. With this arrangement, the auxiliary structure can effectively avoid the problem of disconnection of the conductive layer in the subsequent etching process, and can also avoid the problem of residual conductive material, thereby avoiding the electrical connection between two adjacent first driving electrodes and improving the yield of products. In addition, although there is no overlapping portion, the auxiliary structure can protect the edge of the piezoelectric material layer in the process of stripping the photoresist pattern (PR), thus preventing the piezoelectric material layer from falling off.

An embodiment of the present disclosure provides a fingerprint identification module. <FIG> is another schematic cross-sectional view along the second direction of the fingerprint identification module provided according to an embodiment of the present disclosure; <FIG> is another schematic diagram of the positional relationship between the driving electrodes and the receiving electrodes in the fingerprint identification module according to an embodiment of the present disclosure. As shown in <FIG>, the fingerprint identification module <NUM> includes the functional substrate <NUM>, the piezoelectric material layer <NUM>, the auxiliary structure <NUM> and the plurality of first driving electrodes <NUM>. The piezoelectric material layer <NUM> is located on the functional substrate <NUM>, and the auxiliary structure <NUM> is at least partially located on the functional substrate <NUM>. The plurality of first driving electrodes <NUM> are located on the side of the piezoelectric material layer <NUM> and the auxiliary structure <NUM> away from the functional substrate <NUM>. The functional substrate <NUM> includes a substrate receiving electrode layer <NUM>, a driving circuit layer <NUM> and a substrate <NUM>; the receiving electrode layer <NUM> is located on a side of the piezoelectric material layer <NUM> close to the substrate <NUM> and includes the plurality of receiving electrodes <NUM>. The driving circuit layer <NUM> is located on a side of the receiving electrode layer <NUM> close to the substrate <NUM> and includes the plurality of driving units <NUM>, the plurality of driving units <NUM> are arranged in one-to-one correspondence with the plurality of driving units <NUM>, and the plurality of driving units <NUM> are configured to drive the plurality of receiving electrodes <NUM> to receive the electrical signals generated by the piezoelectric material layer <NUM>. The orthographic projections of the plurality of receiving electrodes <NUM> on the substrate <NUM> at least partially overlap with the orthographic projection of the piezoelectric material layer <NUM> on the substrate <NUM>.

As shown in <FIG>, the functional substrate <NUM> further includes a plurality of second driving electrodes <NUM> located between the receiving electrode layer <NUM> and the driving circuit layer <NUM>. The plurality of first driving electrodes <NUM> and the plurality of second driving electrodes <NUM> form a plurality of driving electrode pairs <NUM>, and orthographic projections of the first driving electrode <NUM> and the second driving electrode <NUM> which are in each driving electrode pair <NUM> on the piezoelectric material layer <NUM> at least partially overlap. With this arrangement, the first driving electrode and the second driving electrode which are in each driving electrode pair and the piezoelectric material layer can constitute one ultrasonic wave emitting element, thereby realizing ultrasonic wave emission. In addition, the fingerprint identification module can also apply a first driving voltage (for example, +50V) to the first driving electrode and apply a second driving voltage (for example, -50V) having a polarity that is opposite to that of the first driving voltage to the second driving electrode, thereby realizing high-voltage driving or high-voltage excitation of the piezoelectric material layer with lower driving voltage (absolute value). Therefore, the fingerprint identification module can realize high-voltage driving or high-voltage excitation of the piezoelectric material layer with a lower driving voltage (absolute value), which can greatly reduce the risk of breakdown of electronic components (such as thin film transistors) in the driving unit caused by high voltage, thereby improving the stability and durability of products, and which is beneficial to realize a large-sized fingerprint identification module on the other hand. It should be noted that because the receiving electrode is electrically connected with the driving unit, and the driving voltage cannot be directly applied to the receiving electrode, the fingerprint identification module provided in this example skillfully sets the plurality of second driving electrodes which form the plurality of driving electrode pairs with the plurality of first driving electrodes to realize high-voltage driving or high-voltage excitation of the piezoelectric material layer with a lower driving voltage (absolute value).

In some examples, as shown in <FIG>, the plurality of receiving electrodes <NUM> are arranged in an array along the first and second directions, the plurality of first driving electrodes <NUM> are arranged along the second direction, the plurality of second driving electrodes <NUM> are arranged along the second direction, and each first driving electrode <NUM> and each second driving electrode <NUM> are strip electrodes extending along the first direction.

In some examples, as shown in <FIG>, an orthographic projection of each second driving electrode <NUM> on the piezoelectric material layer <NUM> at least partially is overlapped with the orthographic projections of several receiving electrodes <NUM> arranged in the first direction on the piezoelectric material layer <NUM>. The fingerprint identification module <NUM> further includes a plurality of connecting electrodes <NUM>, each second driving electrode <NUM> includes a plurality of through holes <NUM>, and the plurality of connecting electrodes <NUM> are respectively arranged in the plurality of through holes <NUM> and electrically connect the plurality of receiving electrodes <NUM> with the plurality of driving units <NUM> respectively. With this arrangement, the receiving electrodes can better receive the electrical signals generated by the piezoelectric material layer due to receiving the ultrasonic wave, thereby improving the accuracy of fingerprint recognition.

An embodiment of the present disclosure also provides an electronic device. <FIG> is a structural diagram of the electronic device according to an embodiment of the present disclosure. As shown in <FIG>, the electronic device <NUM> includes the fingerprint identification module <NUM> described above. Therefore, the electronic device can realize the fingerprint identification function. In addition, because the fingerprint identification module included in the electronic device can effectively avoid the problems of disconnection of the conductive layer and residual conductive material in the subsequent etching process, the electronic device has better yield and performance.

For example, in some examples, as shown in <FIG>, the display device <NUM> further includes a display module <NUM>, and the area of the display module <NUM> is substantially the same as the area of the fingerprint identification module <NUM>, so that full-screen fingerprint recognition can be realized. At this time, the fingerprint identification module can also realize a touch function, so that an additional touch device, such as a capacitive touch panel, is not required, and the cost of the display device can be reduced. Of course, the embodiments of this disclosure include but are not limited to this. The area of the display module and the area of the fingerprint identification module may be not equal, and the fingerprint identification module may be arranged only in the area where fingerprint identification is required.

In some examples, the electronic device may be a display device. For example, the display device can be an electronic apparatus with display function such as a television, a mobile phone, a computer, a notebook computer, an electronic photo album, and a navigator.

An embodiment of the present disclosure also provides a manufacturing method of the fingerprint identification module. <FIG> is a flowchart of the manufacturing method of the fingerprint identification module according to an embodiment of the present disclosure. As shown in <FIG>, the manufacturing method of the fingerprint identification module includes the following steps S101-S104.

Step S101: providing the functional substrate.

Step S102: forming the piezoelectric material layer on the functional substrate. For example, the piezoelectric material layer can be made of a piezoelectric material with high piezoelectric voltage constant, such as polyvinylidene fluoride (PVDF).

Step S103: forming the auxiliary structure on the functional substrate formed with the piezoelectric material layer.

Step S104: forming the plurality of first driving electrodes on the side, away from the functional substrate, of the piezoelectric material layer and the auxiliary structure, so that each first driving electrode extends along the first direction and exceeds the first edge of the piezoelectric material layer in the first direction, the plurality of first driving electrodes are arranged at intervals along the second direction, the auxiliary structure is at least in contact with the first edge, and the auxiliary structure includes the slope portion, the thickness of the slope portion in the direction perpendicular to the functional substrate gradually decreases from the first edge to the direction away from the center of the piezoelectric material layer, and the second direction intersects with the first direction.

In the manufacturing method of the fingerprint identification module provided by the embodiments of the disclosure, because the auxiliary structure is at least in contact with the first edge, the first driving electrode extending in the first direction and exceeding the first edge extends from the piezoelectric material layer to the auxiliary structure instead of directly extending from the piezoelectric material layer to the functional substrate; in addition, the auxiliary structure includes the slope portion, and the thickness of the slope portion gradually decreases from the first edge to the direction away from the center of the piezoelectric material layer. Therefore, in the process of forming the plurality of first driving electrodes on the piezoelectric material layer, the photoresist can be fully exposed and developed at the first edge, so that the problem of disconnection of the conductive layer in the subsequent etching process can be effectively avoided, and the problem of residual conductive material can also be avoided, so that the adjacent two first driving electrodes are prevented from being electrically connected, and the yield of products can be improved.

In some examples, forming the auxiliary structure on the functional substrate formed with the piezoelectric material layer includes: coating a liquid curing adhesive on the functional substrate formed with the piezoelectric material layer; patterning the liquid curing adhesive to expose at least part of the piezoelectric material layer; and curing the liquid curing adhesive, so that the slope portion is formed by leveling and curing the liquid curing adhesive. Therefore, in the process of forming the auxiliary structure, the liquid curing adhesive has certain fluidity or ductility, the liquid curing adhesive undergoes a leveling process, so that the above-mentioned slope portion is naturally formed, thus no additional process step is needed, and the manufacturing difficulty and cost can be reduced.

For example, the first direction and the second direction may be perpendicular to each other.

In some examples, the material of the auxiliary structure includes optical curing adhesive (OC adhesive). Therefore, in the step of patterning the liquid curing adhesive to expose at least part of the piezoelectric material layer, the liquid curing adhesive can be directly patterned by the exposure process without using the mask process, thereby further reducing the manufacturing cost. For example, the material of the auxiliary structure may be an acrylate system material.

For example, the liquid curing adhesive can be cured by thermal curing. Of course, the embodiments of this disclosure include but are not limited to this, and other curing methods can be used to cure the liquid curing adhesive.

For example, the material of the auxiliary structure can be a low-temperature curable material; for example, the curing temperature is less than <NUM> degrees Celsius. With this arrangement, adverse effects of high temperature on other structures of the fingerprint identification module can be avoided.

In some examples, forming the auxiliary structure on the functional substrate formed with the piezoelectric material layer includes: patterning the liquid curing adhesive to expose at least part of the piezoelectric material layer to form the main body portion which is located on the functional substrate and arranged in the same layer as the piezoelectric material layer, and to form the overlapping portion connected with the main body portion and located at a side, away from the functional substrate, of the first edge of the piezoelectric material layer. With this arrangement, the auxiliary structure can prevent the piezoelectric material layer from falling off in the manufacturing and using processes by fixing the piezoelectric material layer on the functional substrate through the overlapping portion while avoiding the generation of the problems such as disconnection and conductive material residue in the forming process of the first driving electrodes.

In some examples, in the case that the material of the piezoelectric material layer includes polyvinylidene fluoride (PVDF), the adhesion between PVDF and the functional substrate (such as silicon nitride layer) is poor, which leads to the piezoelectric material layer falling off easily. Therefore, by forming the overlapping portion, the manufacturing method of the fingerprint identification module can effectively avoid and prevent the piezoelectric material layer from falling off in the manufacturing process. On the other hand, in the process of stripping the photoresist pattern (PR), the compositions of the stripping liquid of the photoresist pattern usually include N-methyl formamide (NMF) and diethylene glycol monomethyl ether, and polyvinylidene fluoride is dissolved in N-methyl formamide and ethers. Therefore, on the one hand, the above auxiliary structure can protect the edge of the piezoelectric material layer in the process of stripping the photoresist pattern (PR), preventing the stripping liquid of the photoresist pattern from corroding the piezoelectric material layer, thereby avoiding the falling off of the piezoelectric material layer; on the other hand, the overlapping portion of the auxiliary structure can fix the piezoelectric material layer on the functional substrate, thereby further preventing the piezoelectric material layer from falling off in the manufacturing process.

In some examples, the size of the overlapping portion in the first direction is greater than <NUM> microns. According to the experimental results, in the case that the size of the overlapping portion in the first direction is larger than <NUM> microns, the auxiliary structure can effectively prevent the piezoelectric material layer from falling off in the processes of manufacturing and using. For example, the size of the overlapping portion in the first direction may be <NUM>, <NUM>, <NUM>, <NUM> or <NUM> microns.

In some examples, forming the plurality of first driving electrodes on the side of the piezoelectric material layer and the auxiliary structure away from the functional substrate includes: forming the metal layer on the side of the piezoelectric material layer and the auxiliary structure away from the functional substrate; forming the transparent metal oxide layer on the side of the metal layer away from the piezoelectric material layer; patterning the transparent metal oxide layer to form the plurality of strip-shaped transparent metal oxides; and etching the metal layer with the plurality of strip-shaped transparent metal oxides as a mask to form the plurality of first driving electrodes. Therefore, in stripping the photoresist pattern, the metal layer still covers the piezoelectric material layer, so that the stripping liquid of the photoresist pattern can be prevented from corroding the piezoelectric material layer.

For example, patterning the transparent metal oxide layer to form the plurality of strip-shaped transparent metal oxides includes: forming the photoresist pattern on the side of the transparent metal oxide layer away from the metal layer; patterning the transparent metal oxide layer with the photoresist pattern as a mask to form the plurality of strip-shaped transparent metal oxides; and stripping the photoresist pattern. It can be seen that in the above manufacturing process, in stripping the photoresist pattern, the metal layer still covers the piezoelectric material layer, so that the stripping liquid of the photoresist pattern can be prevented from corroding the piezoelectric material layer.

For example, the transparent metal oxide may include indium tin oxide (ITO).

In some examples, the thickness of the transparent metal oxide layer ranges from <NUM> to <NUM>Å. Because the piezoelectric material layer is usually a porous material with rough surface, the surface of the metal layer is uneven, in this way, the transparent metal oxide layer can better cover the metal layer.

In some examples, forming the piezoelectric material layer on the functional substrate includes: coating and crystallizing a piezoelectric material on the functional substrate; forming a hard mask on the crystallized piezoelectric material; and etching the crystallized piezoelectric material by using the hard mask as a mask to form the piezoelectric material layer. A material of the hard mask includes at least one selected from the group consisting of molybdenum, aluminum, titanium, niobium and indium tin oxide. Therefore, by using the hard mask, the stripping liquid of photoresist pattern can be prevented from corroding the piezoelectric material layer to a certain extent, so as to improve the quality of the piezoelectric material layer and improve the performance of the fingerprint identification module.

Claim 1:
A fingerprint identification module (<NUM>), comprising:
a functional substrate (<NUM>);
a piezoelectric material layer (<NUM>) on the functional substrate (<NUM>);
an auxiliary structure (<NUM>) at least partially located on the functional substrate (<NUM>);
a plurality of first driving electrodes (<NUM>) at a side, away from the functional substrate (<NUM>), of the piezoelectric material layer (<NUM>) and the auxiliary structure (<NUM>),
wherein each of the first driving electrodes (<NUM>) extends along a first direction, the piezoelectric material layer (<NUM>) comprises a first edge (<NUM>) extending along a second direction, and each of the first driving electrodes (<NUM>) exceeds the first edge (<NUM>) of the piezoelectric material layer (<NUM>) in the first direction, the second direction is perpendicular to the first direction;
the plurality of first driving electrodes (<NUM>) are arranged at intervals along the second direction; the auxiliary structure (<NUM>) is at least in contact with the first edge (<NUM>) of the piezoelectric material layer (<NUM>); the auxiliary structure (<NUM>) comprises a slope portion (<NUM>); a thickness of the slope portion (<NUM>) in a direction perpendicular to the functional substrate (<NUM>) gradually decreases in a direction from the first edge (<NUM>) to a position away from a center of the piezoelectric material layer (<NUM>);
which is characterized in that the fingerprint identification module (<NUM>) further comprises:
a first insulating layer (<NUM>) at a side, away from the functional substrate (<NUM>), of the plurality of first driving electrodes (<NUM>);
an acoustic wave reflective layer (<NUM>) at a side, away from the plurality of first driving electrodes (<NUM>), of the first insulating layer (<NUM>),
wherein an orthographic projection of the acoustic wave reflective layer (<NUM>) on the functional substrate (<NUM>) is overlapped with an orthographic projection of the piezoelectric material layer (<NUM>) on the functional substrate (<NUM>).