CN115273156A

CN115273156A - Ultrasonic fingerprint identification device and ultrasonic fingerprint identification chip

Info

Publication number: CN115273156A
Application number: CN202110477203.XA
Authority: CN
Inventors: 吴清清; 黄景泽; 高传海; 周彬; 潘圣莹; 效烨辉; 谢詹奇; 许俊峰; 焉逢运
Original assignee: Silead Inc
Current assignee: Silead Inc
Priority date: 2021-04-29
Filing date: 2021-04-29
Publication date: 2022-11-01

Abstract

This specification discloses ultrasonic fingerprint identification device and ultrasonic fingerprint identification chip, the device includes: the ultrasonic sensor is used for transmitting and receiving ultrasonic signals and provided with two opposite sides, a first medium layer is arranged on one side, a second medium layer is arranged on the other side, and a third medium layer is arranged above the second medium layer and away from the ultrasonic sensor; the ultrasonic sensor forms a structure for ultrasonic resonance between the first medium layer and the second medium layer, and ultrasonic signals sent by the ultrasonic sensor can be transmitted out of the second medium layer and enter the third medium layer after being resonated, and then enter the ultrasonic sensor after being reflected by a target body above the third medium layer. The method and the device can enhance the sound wave intensity of the ultrasonic wave signal and improve the signal to noise ratio of the fingerprint image.

Description

Ultrasonic fingerprint identification device and ultrasonic fingerprint identification chip

Technical Field

The application relates to the technical field of fingerprint identification, in particular to an ultrasonic fingerprint identification device and an ultrasonic fingerprint identification chip.

Background

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

The information carrier of the ultrasonic fingerprint identification technology is ultrasonic waves which can penetrate through various media, so that the ultrasonic waves can penetrate through the epidermis layer and detect the three-dimensional details of the fingerprint, and the safety of the living fingerprint identification is enhanced. Meanwhile, the ultrasonic identification is not affected by the dirt possibly existing on the finger, so that the usability of the fingerprint identification is greatly improved.

When the ultrasonic fingerprint identification module is used, the ultrasonic fingerprint identification module needs to be placed below a detection area (usually a specific area on a display screen), the acoustic impedance of the ridge of the finger is different from the acoustic impedance of air of the valley of the finger, so that the reflectivity of the ultrasonic wave at the ridge of the finger is different from that of the valley of the finger, the reflected sound waves are different, and a fingerprint image containing the information of the ridge of the finger and the valley of the finger can be obtained after the circuit signal processing.

For an ultrasonic fingerprint identification module, the module currently comprises a detection part and a signal processing part, wherein the detection part and the signal processing part are two separate chips. With the pursuit of better experience of users, a detection part currently adopts a TFT large-area array fingerprint identification chip, the TFT large-area array fingerprint identification chip generally takes a glass substrate as a substrate layer, a TFT pixel circuit is manufactured on the glass substrate, and the manufactured chip and a chip of a signal processing part are respectively connected to a circuit board after the manufacturing is finished. This leads to the following problems:

1) The active layer is made of polycrystalline silicon by adopting a TFT circuit process, and the grain size is smaller than the CD size of the TFT pixel circuit, so that a grain boundary possibly exists at each thin film transistor channel, the grain boundary is a material defect, electrons can be captured randomly, and thus electrical noise is generated, and the signal-to-noise ratio of the ultrasonic fingerprint identification module is low;

2) The TFT circuit is limited by the CD size (the CD size is larger), the required pixel unit size is larger, and the resolution of module imaging is lower; meanwhile, the parasitic capacitance of the circuit is large due to the large size of the pixel unit, and the quantity of the acquired charge signals is reduced;

3) Since the detection part and the signal processing part are packaged respectively, a plurality of I/O interfaces are required to be reserved on the chips of the detection part and the signal processing part, and the packaging difficulty is increased.

It should be noted that the above background description is only for the convenience of clear and complete description of the technical solutions in the present specification and for the understanding of those skilled in the art. Such solutions are not considered to be known to the person skilled in the art merely because they have been set forth in the background section of the present specification.

Disclosure of Invention

In order to solve at least one technical problem that prior art exists, an object of this application is to provide an ultrasonic fingerprint identification device and ultrasonic fingerprint identification chip, can strengthen ultrasonic signal's sound wave intensity, improve the SNR of fingerprint image.

At least one purpose is achieved, and the technical scheme is as follows:

an ultrasonic fingerprint recognition device comprising:

the ultrasonic sensor is used for transmitting and receiving ultrasonic signals and provided with two opposite sides, a first medium layer is arranged on one side, a second medium layer is arranged on the other side, and a third medium layer is arranged above the second medium layer and away from the ultrasonic sensor;

the ultrasonic sensor forms a structure for ultrasonic resonance between the first medium layer and the second medium layer, and ultrasonic signals sent by the ultrasonic sensor can be transmitted from the second medium layer to the third medium layer after resonance, and enter the ultrasonic sensor after being reflected by a target body above the third medium layer.

In a preferred embodiment, the first dielectric layer is air.

As a preferred embodiment, the ultrasonic sensor has a first surface and a second surface opposite to each other, the first surface being in contact with the first medium layer, and the ultrasonic sensor includes: the ultrasonic sensor comprises a protective layer, an electrode layer and a piezoelectric layer which are sequentially stacked from the second surface to the second surface, wherein the acoustic impedances of the protective layer, the electrode layer and the piezoelectric layer are close to or equal to each other, and the thickness of the ultrasonic sensor in the stacking direction is an odd multiple of one quarter of the wavelength of the ultrasonic sensor.

In a preferred embodiment, the protective layer, the electrode layer, and the piezoelectric layer are formed of a polymer, and the acoustic impedance of the ultrasonic sensor is 1 to 10MRayls.

In a preferred embodiment, the electrode layer is made of metal, and the thickness of the electrode layer is less than 1 μm.

As a preferred embodiment, the second dielectric layer is a silicon-based substrate.

In a preferred embodiment, the substrate is rectangular and has a side length of 3 to 40mm.

As a preferred embodiment, the silicon-based substrate has a third surface and a fourth surface opposite to each other, the third surface faces the ultrasonic sensor, the third surface includes an identification region and a non-identification region, the identification region is used for arranging a CMOS pixel unit array and a bottom electrode for electrically coupling the CMOS pixel unit array and the ultrasonic sensor, the non-identification region is used for forming a signal processing circuit electrically connected to the CMOS pixel unit array and the ultrasonic sensor, and the signal processing circuit is used for providing a driving voltage for the ultrasonic sensor and processing an electrical signal emitted by the CMOS pixel unit array.

As a preferred implementation manner, a circuit film layer for forming a CMOS pixel unit array and the signal processing circuit is disposed on the third surface, an acoustic impedance of the circuit film layer is close to or equal to an acoustic impedance of the silicon-based substrate, and the acoustic impedance of the silicon-based substrate is 21-23MRayls.

As a preferred embodiment, the non-recognition area includes: the non-recognition area includes: and the I/0 interface area is used for connecting the FPC circuit board.

In a preferred embodiment, the third medium layer is a display screen.

In a preferred embodiment, the thickness of the third dielectric layer is greater than 300um.

As a preferred implementation manner, glue is disposed between the third dielectric layer and the second dielectric layer, and an acoustic impedance of the glue is between the third dielectric layer and the second dielectric layer.

As a preferred embodiment, the glue is a heat-curable epoxy or a UV-curable epoxy, the glue having a thickness of one quarter of its wavelength.

As a preferred embodiment, the glue is a composite film layer of a conductive material and an organic substance, the total thickness of the glue is 5-50 μm, and the thickness of the conductive material is 1-15 um.

As a preferred implementation manner, glue is disposed between the third dielectric layer and the second dielectric layer, and acoustic impedance of the glue is close to or equal to that of the third dielectric layer.

An ultrasonic fingerprint identification chip, comprising:

the ultrasonic sensor is used for transmitting and receiving ultrasonic signals and provided with two opposite sides, a first dielectric layer is arranged on one side, a silicon-based substrate is arranged on the other side, and a display screen is arranged above the silicon-based substrate, which deviates from the ultrasonic sensor;

forming an identification region and a non-identification region on the silicon-based substrate, wherein the identification region is used for forming a CMOS pixel unit array, and the non-identification region is used for forming a signal processing circuit;

the ultrasonic sensor forms a structure for ultrasonic resonance between the first medium layer and the silicon-based substrate, and ultrasonic signals sent by the ultrasonic sensor can be transmitted out of the silicon-based substrate and enter the display screen after being resonated, and then enter the ultrasonic sensor after being reflected by a target body above the display screen.

Has the advantages that:

according to the ultrasonic fingerprint identification device in the embodiment of the application, the first dielectric layer and the second dielectric layer are formed on the two sides of the ultrasonic sensor to form a structure for ultrasonic resonance, and ultrasonic signals sent by the ultrasonic sensor can be transmitted out of the second dielectric layer after being resonated and then enter the third dielectric layer. Wherein, ultrasonic wave can strengthen on the amplitude when resonance at every turn, shows to launch ripples and the reflection wave phase place that ultrasonic sensor both sides interface reflected back is the same or similar, so can superpose the reinforcing, consequently every reflection, the sound wave can strengthen once to amplitude constantly strengthens, makes the sound intensity improve. The filtering action through the second dielectric layer may filter out the frequency mismatched acoustic waves as the transmitted waves pass out of the second dielectric layer, thereby reducing noise. And the propagation of the sound wave in the third medium layer can increase the return time of the reflected wave, so that the echo signal is separated from the transmitted signal in time, and the received echo signal is purer. Therefore, ultrasonic signals emitted by the ultrasonic sensor reach the target body after sequentially passing through the resonance structure, the second medium layer and the third medium layer, sound waves are enhanced, filtered and delayed in the process, and the signal-to-noise ratio can be improved.

In addition, the ultrasonic fingerprint identification chip provided by the embodiment of the application adopts a silicon substrate, and an identification area and a non-identification area are formed on the silicon substrate, wherein the identification area is used for manufacturing a CMOS pixel unit array, and the non-identification area is used for manufacturing a signal processing circuit, so that the existing detection part and the existing signal processing part are integrated on the same chip, and the integration degree is higher.

Compared with the common TFT pixel circuit manufactured on a glass substrate, the active layer of the silicon substrate is monocrystalline silicon, the grain boundary defects are few, and therefore the noise is lower. Meanwhile, the size (CD) of a silicon-based CMOS (complementary metal oxide semiconductor) process is smaller, the minimum size of the current mass production process can reach 5nm, and the size of a pixel unit manufactured by the CMOS process is far smaller than that of a pixel unit manufactured by the TFT process, so that the size of the CMOS pixel unit is smaller, and the imaging resolution of a chip is higher.

Specific embodiments of the present invention are disclosed in detail with reference to the following description and drawings, indicating the manner in which the principles of the invention may be employed. It should be understood that the embodiments of the invention are not so limited in scope.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments, in combination with or instead of the features of the other embodiments.

It should be emphasized that the term "comprises/comprising" when used herein, is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.

Fig. 1 is a schematic view of an ultrasonic fingerprint identification device provided in an embodiment of the present application;

fig. 2 is a schematic top view of a circuit layout of an ultrasonic fingerprint identification device (ultrasonic sensor is not shown) according to an embodiment of the present application;

FIG. 3 isbase:Sub>A schematic cross-sectional view taken along A-A of FIG. 2;

FIG. 4 is a schematic cross-sectional view of FIG. 2 taken along the direction B-B;

FIG. 5 is a graph of a transmitted wave of an ultrasonic signal provided by an embodiment of the present application;

FIG. 6 is a graph of displacement versus time for

points

1 and 2 in FIG. 1;

FIG. 7 is a graph of displacement over time for

points

3 and 4 in FIG. 1;

fig. 8 is a graph showing voltage signal changes of the sensing unit 1 and the sensing unit 2 of fig. 1;

FIG. 9 is a plot of the thickness of the first stack of FIG. 1 versus the acoustic energy in the first stack;

fig. 10 is a circuit diagram of a CMOS pixel array according to an embodiment of the present disclosure;

FIG. 11 is a block diagram of an ultrasonic fingerprint identification chip according to an embodiment of the present disclosure;

fig. 12 is a schematic view of a package structure of an ultrasonic fingerprint identification chip according to an embodiment of the present disclosure.

Description of the reference numerals:

100. an ultrasonic fingerprint identification chip;

1. a second dielectric layer/silicon-based substrate; 10. identifying an area; 101. an array of CMOS pixel cells; 11. a non-recognition area; 111. a control module; 112. an RX module; 113. a data processing module; 114. an analog-to-digital conversion module; 115. a row selection driving module; 14. an I/O interface area; 15. a third surface; 16. a fourth surface; 17. a bottom electrode;

2. an ultrasonic sensor; 21. a first surface; 22. a second surface; 23. a protective layer; 24. an electrode layer; 25. a piezoelectric layer;

3. a third dielectric layer;

4. gluing;

5. an FPC board; 6. an anisotropic conductive adhesive; 7. reinforced steel plate

A. A first laminate; B. a second laminate; C. and a third stack.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.

It will be understood that when an element is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a single embodiment.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1 to 12, the present application provides an ultrasonic fingerprint identification device and an ultrasonic fingerprint identification chip. The ultrasonic fingerprint identification device and the ultrasonic fingerprint identification chip provided by the application specification can be used for electronic equipment such as mobile phones, intelligent watches, intelligent wearable equipment, intelligent earphones, notebook computers, panels and cameras. Meanwhile, the device can also be applied to other equipment such as automobiles, electronic switch devices, access control systems and the like.

It should be noted that the ultrasonic fingerprint identification device and the ultrasonic fingerprint identification chip provided in the present application are not limited to be used for detecting fingerprints of living bodies, and in an extensible application scenario, the device and the chip can also be used for palm print identification, heart rate detection, blood pressure detection, 3D imaging of superficial tissues of human bodies (such as eyes, ears, and nose). The present application is mainly described in the context of fingerprint recognition, but it should be understood that the scope of protection of the present application is not limited thereto.

As shown in fig. 1, the ultrasonic fingerprint identification device provided by the present application mainly includes an ultrasonic sensor 2, where the ultrasonic sensor 2 is used to transmit and receive ultrasonic signals, and the ultrasonic sensor 2 has two opposite sides, and a first dielectric layer is disposed on one side, and a second dielectric layer 1 is disposed on the other side.

The first dielectric layer and the second dielectric layer 1 are media which can be penetrated by sound waves, and may have a solid structure or have no solid structure. For example, the sound wave can penetrate through and propagate in air and water, and air and water do not have a solid structure, but air and water should also be regarded as a medium layer of the sound wave.

The ultrasonic sensor 2 has a first surface 21 and a second surface 22 opposite to each other, the first dielectric layer is in contact with the first surface 21, and the second dielectric layer 1 is in contact with the second surface 22, so that the ultrasonic sensor 2 can form a structure for ultrasonic resonance by selecting the first dielectric layer and the second dielectric layer 1 with acoustic impedances meeting predetermined requirements.

Specifically, according to a calculation formula of the acoustic wave reflectivity: r = (z)₁-z₂)²/(z₁+z₂)²，z₁Expressed as the acoustic impedance, z, of one of the two dielectric layers in contact₂Expressed as the acoustic impedance of the other of the two dielectric layers in contact, and r as the reflectivity at the interface of the two dielectric layers. From the above equation, the acoustic impedance (z) of the dielectric layer at the interface can be seen₁And z₂) The larger the phase difference, the larger the acoustic wave reflectivity at the interface, and the acoustic impedance (z) of the dielectric layer at the interface₁And z₂) The smaller the phase difference, the smaller the acoustic wave reflectivity at the interface. For making the ultrasonic sensor 2 resonantThe structure needs to ensure that the acoustic impedance difference between the ultrasonic sensor 2 and the first medium layer is as large as possible, so that when the ultrasonic wave propagates to the interface between the first medium layer and the ultrasonic sensor 2, the ultrasonic wave can approach to total reflection, and similarly, the acoustic impedance difference between the ultrasonic sensor 2 and the second medium layer 1 should also be as large as possible, for example, the interface acoustic wave reflectivity is greater than 0.4, so that when the acoustic wave propagates in the ultrasonic sensor 2, the acoustic wave can reflect back and forth at the interface between the first medium layer and the ultrasonic sensor 2 and the interface between the second medium layer 1 and the ultrasonic sensor 2 to form resonance, so as to increase the amplitude of the ultrasonic wave and improve the signal-to-noise ratio. In addition, the acoustic impedance difference between the ultrasonic sensor 2 and the second medium layer 1 cannot be set too large, for example, the interfacial acoustic wave reflectivity should be less than 0.9, so that the resonant acoustic wave can propagate from the interface between the ultrasonic sensor 2 and the second medium layer 1 to the second medium layer 1.

The principle that the signal-to-noise ratio can be improved by forming resonance in the ultrasonic sensor 2 is as follows: after the sound waves resonate in the ultrasonic sensor 2, when the phases of the transmitted waves and the reflected waves reflected by the interface of the adjacent dielectric layers are the same or close, the transmitted waves and the reflected waves can be superposed and enhanced, so that the sound waves can be enhanced once every time the reflected waves are reflected, and the amplitude is continuously enhanced. Meanwhile, only the acoustic wave component having the same thickness frequency as that of the ultrasonic sensor 2 is left, so that N in the signal-to-noise ratio SNR decreases, and when the acoustic wave is emitted to the target, the intensity of the obtained echo information also increases, so that S in the signal-to-noise ratio SNR increases, N decreases, and the signal-to-noise ratio SNR increases.

Further, the first dielectric layer is air, which has the smallest acoustic impedance, typically 411Rayls. The acoustic impedance of solid media tends to be large, reaching MRayls units relative to air, so z is₁And z₂And z is₁And z₂Approximately equal to the acoustic impedance of the ultrasonic sensor 2 itself, so that the acoustic wave reflectivity at the interface of the first dielectric layer and the ultrasonic sensor 2 is close to 1. In some possible embodiments, the first dielectric layer may be other materials with acoustic impedance lower than MRayls units, and may be other low impedance materials than air.

As shown in fig. 2, the second dielectric layer 1 is a substrate layer, and a circuit for manufacturing an ultrasonic detection portion may be a glass substrate or a silicon-based substrate, and is preferably a silicon-based substrate. The second dielectric layer 1 has a third surface 15 and a fourth surface 16 which are opposite to each other, the third surface 15 faces the second surface 22, the third surface 15 is provided with an identification region 10, the identification region 10 is used for arranging a pixel circuit for detecting an ultrasonic signal, and the pixel circuit is a pixel unit array and a bottom electrode 17 for electrically coupling the pixel unit array and the ultrasonic sensor 2.

Ultrasonic signals emitted by the ultrasonic sensor 2 can be transmitted out of the second medium layer 1 after being resonated. The second dielectric layer 1 is used for filtering the sound waves after resonance, so that the sound waves with unmatched frequencies are filtered out, and noise is further reduced.

The acoustic impedance of the second dielectric layer 1 is 21-23MRayls, and is set to be much larger than that of the ultrasonic sensor 2. Since the sound wave is half-wave lost when reflected at the interface between the silicon-based substrate and the ultrasonic sensor 2, when the transmitted wave (for example, the waveform is sin (ω t)) returns to the position of the transmitted wave through a path twice the wavelength of 1/4 and the half-wave loss, the transmitted wave just undergoes the phase change of one wavelength path, namely, the reflected wave (the waveform is a sin (ω t +2 π), a < 1) and the transmitted wave (the waveform is sin (ω t)) can be superimposed and enhanced, and the waveform of the superimposed resonance wave is (1 a) sin (ω t), namely, the amplitude can be increased by nearly one time after being reflected at the interface between the second dielectric layer 1 and the ultrasonic sensor 2.

In a preferred embodiment, the second dielectric layer 1 is a silicon-based substrate. The silicon-based substrate is monocrystalline silicon, and compared with a traditional glass substrate, the substrate material is more uniform. The roughness of the interface between the second medium layer 1 and the ultrasonic sensor 2 and the roughness of the interface between the second medium layer 1 and the glue 4 are small, the thickness uniformity is good, sound waves can be further filtered when penetrating through the second medium layer 1, sound waves with unmatched frequencies can be filtered, N in the SNR is further reduced, and the SNR is further improved.

In some possible embodiments, a glass substrate can be used for filtering, so that the device cost can be reduced. Meanwhile, because glass is an amorphous material and the material uniformity is poorer than that of monocrystalline silicon, the grinding process is more complicated and difficult, the surface roughness of the thinned wafer is poorer than that of the monocrystalline silicon, and the filtering effect is poorer.

As shown in fig. 1, the ultrasonic fingerprint recognition apparatus further includes: and the third medium layer 3 is arranged above the second medium layer 1 and departs from the ultrasonic sensor 2. Ultrasonic signals sent by the ultrasonic sensor 2 can be transmitted out of the second medium layer 1 and enter the third medium layer 3 after being resonated, and then enter the ultrasonic sensor 2 after being reflected by a target body above the third medium layer 3. Therefore, ultrasonic signals sent by the ultrasonic sensor 2 sequentially pass through the resonance structure, the second medium layer 1 and the third medium layer 3 to reach a target body, and in the process, the ultrasonic signals are enhanced, filtered and delayed, so that the signal-to-noise ratio is improved.

The third medium layer 3 may be a display screen for a user to press or touch with a finger. For different application scenarios, the third dielectric layer 3 may be made of one material such as plastic, glass, metal, or a laminated structure of multiple films made of several media. Particularly, for a common mobile phone OLED screen, the medium is a composite film layer composed of organic matters (PI, OCA and the like) and a glass cover plate.

Further, the third dielectric layer 3 faces the fourth surface 16 of the second dielectric layer 1, and is typically attached by glue 4. Therefore, in the ultrasonic fingerprint identification device provided by the embodiment of the application, the substrate layer is arranged between the display screen and the ultrasonic sensor 2. When the ultrasonic sensor is applied, a fingerprint identification chip consisting of the substrate layer and the ultrasonic sensor 2 can be attached to the lower part of the display screen in a reverse direction, so that a sound wave propagation path of the ultrasonic sensor can be formed.

It is common, ultrasonic sensor 2 sets up the scheme between display screen and the substrate layer, and fingerprint identification module forward pastes in the display screen below promptly. The interface between the ultrasonic sensor 2 and the adjacent two sides is the interface between the ultrasonic sensor 2 and the glue 4, and the interface between the ultrasonic sensor 2 and the substrate layer, respectively. And these two boundariesDielectric acoustic impedance (z) of both sides of the face₁And z₂) The phase difference is small, the acoustic wave reflectivity of the two interfaces is low, and the resonant structure is not favorably formed. In addition, fingerprint identification module is paste in the display screen below to, then the substrate layer will be located ultrasonic sensor 2's below, and the launching wave that ultrasonic sensor 2 produced can not wear out from the substrate layer, also can not reach the effect of filtering.

As shown in fig. 3 and 4, the ultrasonic sensor includes a protective layer 23, an electrode layer 24, and a piezoelectric layer 25, which are stacked, the protective layer 23 being in contact with the first dielectric layer, acoustic impedances of the protective layer 23, the electrode layer 24, and the piezoelectric layer 25 being close to or equal to each other, and a thickness of the ultrasonic sensor 2 in a stacking direction being an odd multiple of a quarter of a wavelength thereof.

The piezoelectric layer 25 is used for transmitting and receiving ultrasonic waves, and the working state of the piezoelectric layer is controlled by a timing signal sent by the signal processing circuit. The piezoelectric layer 25 is a piezoelectric film, and the material may be one or a combination of several of polyvinylidene fluoride (PVDF), polyvinyl chloride, poly-gamma-methyl-L-glutamate, polycarbonate, and polyvinylidene fluoride copolymer, and covers at least the identification region 10, and in consideration of edge effect, the edge distance of the edge is greater than 0.2mm from the edge of the identification region 10, and covers part of the non-identification region 11. The piezoelectric film is divided into a plurality of piezoelectric elements in the identification area 10, each piezoelectric element corresponding to one bottom electrode 17 and one pixel unit.

In addition, taking the direction shown in fig. 1 as an example, the piezoelectric layer 25 is disposed close to the substrate layer, the ultrasonic signal emitted by the piezoelectric layer 25 firstly propagates toward the protective layer 23, resonance is formed in the ultrasonic sensor 2, and after the amplitude of the acoustic wave is enhanced, the acoustic wave passes through the second medium layer 1 and the third medium layer 3 along the illustrated acoustic path, and reaches the target body above the third medium layer 3. After reflection by the target volume, an echo signal is formed which, when returning to the ultrasonic sensor 2 along the acoustic path shown, can directly reach the piezoelectric layer 25.

The electrode layer 24 is used to provide a given level for the piezoelectric film, typically a pulsed ac signal, with a peak-to-peak voltage of 30-300V during the transmit phase and a low level bias (< 10V) or ground during the receive phase. The electrode layer 24 is typically a metallized electrode made of a metal such as Ag, cu, ni, al, a mixture of a metal and a polymer, a conductive rubber, or the like, and covers the piezoelectric film.

In operation, the electrode layer 24 is connected to an ac voltage, and after receiving a TX driving signal of a pulsed ac, the piezoelectric layer 25 is triggered to vibrate to generate an ultrasonic signal of a corresponding frequency, thereby establishing an ultrasonic field of a corresponding pulse. When the transmitted wave target body is reflected to form an echo, each piezoelectric unit on the piezoelectric layer 25 can receive the echo, convert an echo sound signal into an electric signal through a piezoelectric effect, then couple the corresponding electric signal into the pixel circuit unit through the bottom electrode 17, and finally convert the echo signal into an electric signal with fingerprint information.

The protective layer 23 is used for protecting the device, and the material is usually organic matter such as ink, dry film, etc. and covers the electrode layer 24. Since the protective layer 23 is in contact with the first dielectric layer, the surface needs to be flat with a surface roughness < 20nm for better reflection of the ultrasonic signal at the interface, thereby reducing noise.

The ultrasonic sensor 2 with the protective layer 23, the electrode layer 24 and the piezoelectric layer 25 stacked is set to be a resonance structure, and when the device is designed, the acoustic impedances of the three layers of materials are close to each other as much as possible. In one particular embodiment, the protective layer 23, electrode layer 24, and piezoelectric layer 25 are formed of a polymer, have an acoustic impedance of 1 to 10MRayls, and have a thickness of 10 to 30 μm. Preferably, PVDF, silver paste and thermoplastic inks, have an acoustic impedance of about 5MRayls. Alternatively, in some possible embodiments, the electrode layer 24 may be made of metal, generally metal with a high acoustic impedance (> 10 MRayls), so that its thickness is set to be much smaller than its wavelength (typically, the wavelength is larger than 400um, and much smaller than, i.e., at least smaller than one tenth of the value), for example, smaller than 1um, so that the blocking effect of the high acoustic impedance layer on the acoustic wave is negligible.

In this specification, the "wavelength" refers to the wavelength of the sound wave when propagating in the corresponding medium, the "wavelength" corresponding to different medium materials is different, and the sound wave energy is different under different thicknesses of the same medium. As shown in fig. 9, the energy of the acoustic wave penetrating into the medium has a maximum value when the thickness of the ultrasonic sensor 2 is about one quarter of its wavelength or three quarters of its wavelength, and has a minimum value when the thickness of the ultrasonic sensor 2 is about two quarters of its wavelength or one wavelength.

Considering that a larger emission voltage is required as the piezoelectric layer 25 is thicker, and considering the coating process of the piezoelectric material, it is generally set to not more than 30um, specifically, 7um, 9um, 11um, 13um, 15um, and the like. On the other hand, the thicker the piezoelectric layer 25 is, the larger the proportion of the piezoelectric layer occupying the ultrasonic sensor 2 is, and the larger the voltage to be finally outputted is, and in combination with both of them, the total thickness of the ultrasonic sensor 2 is usually set to be one quarter of the wavelength thereof, which is about 10 to 100um. The thicker the electrode layer 24 is, the better the conductivity is, but the acoustic impedance is relatively large, the thickness cannot be set too large, and the protective layer 23 is used to supplement the thickness to make the total thickness of the ultrasonic sensor 2 reach a quarter wavelength.

In operation, a transmission signal as shown in fig. 5 is generated by the circuit, which generally has 1 to 8 cycles, and the peak-to-peak voltage value is generally 50 to 300V, specifically related to the voltage endurance capability of the material of the piezoelectric layer 25 and the voltage boosting capability of the circuit, here, the frequency of the transmission signal is 12MHz, which has 5 cycles, and Vpp =180V. The electrode layer 24 receives an alternating signal and the bottom electrode 17 is grounded or connected to a fixed low level (< 10V). After the piezoelectric unit is subjected to an alternating voltage, corresponding deformation is generated due to an inverse piezoelectric effect, and since the direction of an electric field is longitudinal and the polarization direction of the material of the piezoelectric layer 25 is also longitudinal (realized through a polarization process), the piezoelectric effect is in a d33 mode, and the piezoelectric layer 25 can be stretched and compressed in the thickness direction, so that plane waves propagating outwards are generated.

The fingerprint recognition device provided by the embodiment of the present application is divided into a first laminate a, a second laminate B and a third laminate C according to the acoustic impedance proximity of the materials by the propagation path shown in fig. 1. The first lamination A is of an integral structure of the ultrasonic sensor 2, the second lamination B mainly comprises a substrate layer, and the third lamination C comprises glue and a third medium layer 3.

The finger is divided into a point 1 representing a ridge and a point 2 representing a valley according to the texture of the surface of the finger. According to the different textures of the corresponding finger right above the ultrasonic sensor 2, the acoustic path can be divided into two acoustic paths, namely an acoustic path 1 facing the finger ridge and an acoustic path 2 facing the finger valley. In the ultrasonic wave emitting stage, the ultrasonic wave continuously resonates in the first lamination layer A to form standing waves, and then passes through the second lamination layer B, passes through the third lamination layer C and reaches the finger above the third medium layer 3. The acoustic impedance of the skin at the finger ridges (1.5-2 MRayls) is much different from the acoustic impedance of the air at the finger valleys (411 Rayls), so the reflectivity of the sound waves at the finger ridges and the finger valleys are different, and the reflected sound waves are different, specifically corresponding to the difference between the sound waves at point 1 and point 2. As shown in fig. 6, the amplitude of the acoustic wave at point 2 is larger.

The ultrasonic sensor 2 has a point 3 corresponding to the point 1 and a point 4 corresponding to the point 2, and the pixel cell array on the substrate layer has a sensing cell 1 coupled to the point 3 and a sensing cell 2 coupled to the point 4. When the sound wave with the amplitude difference is reflected along the acoustic path 1 and the acoustic path 2 again, the sound wave respectively reaches the point 3 and the point 4, the point 3 and the point 4 are changed differently due to the difference of the sound wave, and different electric signals are obtained through processing of the sensing unit 1 and the sensing unit 2.

As shown in fig. 7, when the time is less than 1.7us, the sound wave at the finger interface has not returned, and the displacement of the point 3 is the same as that of the point 4; when the time is greater than 1.7us, the acoustic wave at the finger interface returns to the first laminate a, and points 3 and 4 show different magnitudes of displacement. Due to the piezoelectric effect, the voltages generated by the

sensing units

1 and 2 are different, and as can be seen from the voltage signals generated by the

sensing units

1 and 2 shown in fig. 8, when the voltage is about 1.9us, the voltage difference between the valleys and the ridges reaches a maximum value of about 70mV, and the voltage value is read out by the pixel circuit and finally imaged through signal processing.

According to the embodiment of the application, the third dielectric layer 3 can increase the echo time of the reflected ultrasonic wave back to the ultrasonic sensor 2 after being reflected by the target body, so that the echo time is separated from the emission time, and the received echo signal is purer. This application is through setting up ultrasonic sensor 2 to the structure that supplies the ultrasonic resonance, so there is a section time of trailing, this moment at sound wave resonance in-process, the resonance echo signal that ultrasonic sensor 2 is continuous to receive the resonance after the resonance and reflects back (the resonance echo signal does not reach the target body, actually still is the launching wave signal), if not set up the delay layer above the substrate layer, then the echo signal that forms through the target body reflection can't distinguish with resonance echo signal (launching wave signal), consequently make the echo signal received purer through setting up the delay layer.

In a specific embodiment, the thickness of the third dielectric layer 3 is greater than 300um, so that the echo signal can be distinguished from the transmitted wave signal. Of course, the thickness of the third dielectric layer 3 is not limited to this thickness, and may be adjusted based on this thickness.

In one embodiment, the acoustic impedance of the glue 4 is between the third dielectric layer 3 and the second dielectric layer 1. Specifically, the glue 4 is a thermal curing epoxy resin or a UV curing epoxy resin, and the thickness of the glue 4 is one quarter of the wavelength of the glue, so as to ensure that the sound waves pass through the glue 4 with larger energy. Or the glue 4 is a composite film layer of a conductive material and an organic matter, the total thickness of the glue 4 is 5-50 μm, and the thickness of the conductive material is 1-15 um. The conductive film plays a role in conducting and supporting, such as copper foil adhesive, conductive carbon adhesive tape and the like, and the acoustic impedance of the conductive material is preferably more than 20MRayls.

In one embodiment, the acoustic impedance of the glue 4 is close to or equal to the acoustic impedance of the third dielectric layer 3. The thickness of the glue 4 can be considered together with the thickness of the third dielectric layer 3, the total thickness being set to an odd multiple (acoustic impedance between the second dielectric layer 1 and the skin) or an even multiple (acoustic impedance not between the second dielectric layer 1 and the skin) of a quarter wavelength of the third layer stack C. In particular, the medium to be penetrated consists of several film layers of different materials, and in this case, the glue is set according to the film layer material in contact with the glue.

In a specific application scenario, the acoustic impedance of the ultrasonic sensor 2 is 5MRayls, the first dielectric layer is air, the acoustic impedance of the second dielectric layer 1 is 22MRayls, and the acoustic impedance of the glue 4 is 10MRayls. Then, using the formula r = (z)₁-z₂)²/(z₁+z₂)²It can be calculated that the reflectivity between the first laminate a and the air is close to 1, and the reflectivity between the first laminate a and the second laminate B is about 0.4, so that when the sound wave is reflected between the first laminate a and the second laminate B, there is a half-wave loss, and when the transmitted wave (for example, the waveform is sin (ω t)) passes through a path twice the 1/4 wavelength and returns to the position of the transmitted wave, the phase change of just one wavelength path is experienced, that is, the reflected wave (the waveform is 0.4 × sin (ω t +2 π)) and the transmitted wave (the waveform is sin (ω t)) can be enhanced in a superposition manner, and the obtained harmonic wave waveform is 1.4 × sin (ω t), that is, the amplitude can be doubled by reflecting once at the interface between the second dielectric layer 1 and the ultrasonic sensor 2. The reflectivity between the second laminate B and the third laminate C is about 0.14, and it can be seen that most of the acoustic waves propagating from the second dielectric layer 1 enter the third dielectric layer 3 to be received by the target above the third dielectric layer 3.

In this specification, the second dielectric layer 1 is generally rectangular in configuration or other shape as a substrate layer for making a circuit of the ultrasonic detection section. In an embodiment of using a silicon-based substrate, an identification region 10 and a non-identification region 11 may be formed on a third surface 15 of the silicon-based substrate, as shown in fig. 2 and 11, where the identification region 10 is used to dispose a CMOS pixel unit array 101 and a bottom electrode 17 for electrically coupling the CMOS pixel unit array 101 with the ultrasonic sensor 2, and the non-identification region 11 is used to form a signal processing circuit electrically connected to the CMOS pixel unit array 101 and the ultrasonic sensor 2, and the signal processing circuit is used to provide a driving voltage for the ultrasonic sensor 2 and process an electrical signal emitted by the CMOS pixel unit array 101.

Therefore, the signal processing circuit part and the CMOS detection circuit part can be directly manufactured on the silicon substrate, can be integrated on the same chip, and are high in integration degree. Compared with the common TFT pixel circuit manufactured on a glass substrate, the active layer of the silicon substrate is monocrystalline silicon, so that the crystal boundary defects are fewer, and the noise is lower. Meanwhile, the silicon-based CMOS process size (CD) is smaller, the minimum size of the existing mass production process can reach 5nm (the minimum size of the TFT process is generally larger than 1 mu m), and the size of a pixel unit manufactured by the CMOS process is far smaller than that of the pixel unit manufactured by the TFT process, so that the size of the CMOS pixel unit is smaller, and the imaging resolution of a chip is higher.

In addition, as can be seen from the parasitic capacitance calculation formula C = epsilon S/d, the CMOS process size is small, and the silicon-based transistor area S is smaller. The materials of the active regions of the silicon-based transistor and the glass-based transistor are silicon, so that the dielectric constant epsilon is close, the thickness d is related to the junction depth, and the d of the two process circuits is close, so that compared with a glass substrate, the parasitic capacitance of a CMOS pixel unit array manufactured by the silicon-based transistor is smaller, the circuit noise is smaller, and the signal-to-noise ratio of a chip can be effectively improved.

On the third surface 15 of the second dielectric layer 1, the ultrasonic sensor 2 is arranged on the identification area 10, and the identification area 10 is also used for arranging a CMOS detection circuit for detecting an ultrasonic signal. The CMOS detection circuit, which is specifically the CMOS pixel cell array 101, and the signal processing circuit may be electrically coupled through a metal interconnection layer in an integrated circuit process, and detect an ultrasonic signal. The signal processing circuit is fabricated in the non-identification area 11 and is configured to control various aspects of fingerprint identification. Therefore, the signal processing part and the CMOS detection circuit can be integrated on the same substrate, so that a single chip is formed, the packaging structure is simple, and the integration degree is higher.

Further, the non-recognition area 11 is provided with an I/O interface area 14, the I/O interface area 14 is used for connecting with an external device and a signal processing circuit, and the external device can input signals to the chip or receive signals fed back by the chip through the I/O interface area 14. Preferably, as shown in fig. 12, the I/O interface area 14 is used for connecting the FPC board 5.

In a preferred embodiment, the FPC board 5 is located above the non-recognition area 11, and is projected along the thickness direction of the silicon-based substrate, and the projection of the FPC board 5 on the silicon-based substrate does not overlap with the projection of the ultrasonic sensor 2 on the silicon-based substrate. Therefore, the FPC circuit board 5 and the ultrasonic sensor 2 do not interfere with each other, on one hand, the material of the FPC circuit board 5 is saved, on the other hand, the FPC circuit board 5 is convenient to be electrically connected with the I/O interface area 14, and the process difficulty is reduced. In addition, because the FPC board 5 is made of a soft material, a reinforcing steel plate 7 may be disposed below the FPC board 5 to support the FPC board. In addition, by adopting the packaging structure, the flexible circuit board can be bent at will, thereby saving the internal space of the electronic equipment. Preferably, the FPC board 5 and the I/O interface area 14 are connected by an anisotropic conductive adhesive 6.

In a preferred embodiment, the identification area 10 is located in a central region of the third surface 15 and the non-identification area 11 is located in a peripheral region of the identification area 10. Generally, ultrasonic waves used for fingerprint identification have certain divergence when penetrating a medium and are difficult to be equivalent to plane wave emission, so that acoustic information obtained from the edge area of the substrate layer and the central area of the substrate layer is not equivalent, namely, an edge effect is generated. If the entire surface of the substrate is used to form the identification area 10 and to form the detection circuit, the fingerprint image obtained from some of the edge areas is usually discarded when the image is actually identified, resulting in the edge areas not being used properly.

In the embodiment, the identification region 10 is formed in the central region of the third surface 15 of the silicon-based substrate, and the non-identification region 11 is formed in the edge region of the third surface 15, so that the edge region of the chip is effectively utilized, and the effective use area of the chip is higher.

In a specific embodiment, the silicon-based substrate is rectangular, the size of the outer contour is 3-40 mm, the distance between each side of the rectangular identification area 10 and the edge of the chip is 0.2-10 mm, the side length of each pixel unit on the identification area 10 is usually 20-100 um, and the specific value is related to the required setting resolution of the device and the circuit process, and is typically 50um, 55um, 60um, 65um, 70um, 75um, 80um, 85um, 90um. The top of the CMOS detection circuit is a bottom electrode 17 which is arranged in an array, the material is metal such as Al, au, cu, pt, mo and the like, the thickness can be 0.01-20 um, the distance between electrode units is 1-20 um, and the CMOS detection circuit is connected with the ultrasonic sensor 2 above the electrode units.

In this embodiment, the size of the pixel unit manufactured on the silicon-based substrate based on the CMOS process is much smaller than that of the pixel unit manufactured by the TFT process, so that the size of the CMOS pixel unit is smaller, the imaging resolution of the chip is higher, and the overall size of the silicon-based substrate can be made smaller. Because the CMOS detection circuit and the signal processing circuit are both manufactured on the silicon substrate, the size of the silicon substrate can be equivalent to the size of the ultrasonic fingerprint identification chip 100, the size of the chip is 3-40 mm, and the size of the chip is far smaller than that of a fingerprint identification chip adopting a TFT large area array, and the manufacturing cost is favorably reduced.

In order to fabricate circuits on a silicon-based substrate, a circuit film layer for forming the CMOS pixel cell array 101 and the signal processing circuit is disposed on the third surface 15 of the substrate. And the acoustic impedance of the circuit film layer is close to or equal to that of the silicon-based substrate, so that the whole laminated layer formed by the silicon-based substrate and the circuit film layer is used as a filtering layer for filtering. The circuit film layer is generally thin, preferably < 10um, and is composed of inorganic substances such as silicon, silicon oxide, silicon nitride, etc., and has acoustic impedance close to that of single crystal silicon, so that it is equivalent to a silicon-based substrate as a single laminated layer.

In general, the acoustic impedance of the silicon substrate is about 22 mrays, which is set to be much larger than that of the ultrasonic sensor 1. The silicon-based substrate should be as thin as possible, such as 50um, 100um, 150um, or 200 um.

As shown in fig. 10 and 11, the CMOS detection circuit is a CMOS pixel cell array 101, which includes a plurality of CMOS pixel cells, the plurality of CMOS pixel cells may be arranged in a regular form of a plurality of rows and a plurality of columns, the circuit further includes a row selection line and a column selection line, when the row selection line is turned on row by row or interlaced, the CMOS pixel cells in the corresponding row are turned on, and the electrical signals stored in the CMOS pixel cells are read out through the corresponding column selection line.

In one specific embodiment, as shown in fig. 10, each pixel unit includes: piezoelectric unit, peak detection transistor M1, latch transistor M2, source follower transistor M3, capacitor C1, and readout transistor M4. The mutually independent control signals are provided by the control module 111: TX, bias, OD _1, OD _2, etc. In the pixel reading stage, the row selection switch controls the on of the reading transistor M4, the charge signal of the sensing unit is output from the out end, and the image is output after the amplification, the filtering, the analog-to-digital conversion and the digital processing of the charge amplifier.

Correspondingly, the signal processing circuit on the non-identification area 11 may include a control module 111 (bias driver, TX transmitter driver, driver 1 and driver 2), an RX module 112 (charge amplifier, filter), an analog-to-digital conversion module 114 and a data processing module 113. The control module 111 is configured to control the timing and TX waveform generation of the ultrasonic TX driver, the biasing of the sensing unit and peak detection transistor, row selection, driver timing control required by the detection circuitry, readout frame rate, signal filtering and analog-to-digital conversion, etc. The drivers required for the detection circuit include the driving of the OD 1 and OD 2 signals. The data processing module 113 receives data from the RX module 112, converts the digitized data to image data for a fingerprint, and then provides the I/O interface area 14 for further processing.

Specifically, the control module 111 generates a TX signal at regular time intervals, and transmits the TX signal to the ultrasonic sensor 2 via the TX driver, so as to drive the ultrasonic sensor 2 to generate ultrasonic waves. When the ultrasonic wave carrying the fingerprint information returns to the ultrasonic sensor 2, the control module 111 controls the bias driver, the driver 1 and the driver 2, and locks the charge information of each pixel unit after the receiving process of the ultrasonic receiver. The control module 111 further controls the row selection switch of the RX module 112 and the readout transistor M4 of the pixel module to perform row-by-row reading of signals. Upon reading of each row of pixel signals, the control module 111 may control the multiplexer of the RX module 112 to enable the reading of the signals. Further, the signal is subjected to signal amplification, filtering, analog-to-digital conversion, and digital processing, and finally transmitted through the I/O interface region 14.

Of course, the specific structure of the pixel unit is not limited to the above example, and correspondingly, the signal processing circuit on the non-recognition area 11 is not limited to the above list, and other modifications can be made by those skilled in the art within the spirit of the present application, and all that is needed is to cover the protection scope of the present application as long as the achieved function and the achieved effect are the same as or similar to those of the present application. However, the signal processing circuitry should include at least the processing to control the timing of the ultrasonic TX driver, the driver timing control required for the detection circuitry, and the readout signal.

In this specification, when the ultrasonic sensor 2 is formed on a silicon substrate, a circuit including a CMOS detection circuit and a signal processing circuit is first formed on a silicon wafer by a conventional integrated circuit process, a main film layer includes a doping layer, an insulating layer, a metal interconnection layer, a passivation layer, etc., a bottom electrode 17 and an I/O interface region 14 are respectively formed above the circuit, and a metal conductive layer may be disposed on the I/O interface region 14 so as to be connected to an external circuit board or other electronic devices.

Further, the solution with the piezoelectric copolymer may be coated on top of the CMOS detection circuit, or may be applied by spin coating, slit coating, screen printing, spraying, printing, laminating, or other coating methods. In particular, the seed layer solution may be pre-coated to modify the surface properties of the wafer before applying the piezoelectric copolymer, thereby obtaining a piezoelectric layer 25 with better piezoelectric properties. And then, baking the silicon wafer at a high temperature to volatilize the adhesion promoter in the film layer and crystallize the piezoelectric copolymer, wherein the temperature is higher than the Curie temperature of the copolymer and lower than the melting point. The piezoelectric copolymer is crystallized to form the piezoelectric layer 25, and after the crystallization, the piezoelectric layer 25 is placed in a strong electric field to be polarized in a direction along the thickness direction of the piezoelectric layer 25. Specifically, the method can be realized by in-situ polarization, a polarization electrode (not shown in the figure) of the piezoelectric film layer is grounded, then, an I/O interface region of the wafer is protected by an insulating fixture and is placed below the polarization equipment, under the action of an electric field, ambient gases between the piezoelectric film layer and the polarization equipment are ionized to form plasma, and the gases are gathered on the surface of the piezoelectric layer 25, so that an in-film electric field in the thickness direction is formed in the piezoelectric layer 25, and polarization of the piezoelectric layer 25 is realized. In addition, after the polarization is finished, the patterning of the piezoelectric film layer can be realized by a wet etching method or a dry etching method.

The electrode layer 24 is prepared by spin coating, screen printing, chemical vapor deposition, physical vapor deposition, plasma sputtering, and the like. In addition, the patterning can be realized by a wet etching method or a dry etching method. Finally, the protective layer 21 may be prepared in the same manner, thus completing the fabrication of the ultrasonic sensor on the identification area 10 to form a complete wafer for subsequent packaging with the circuit board 4.

Before packaging, the wafer needs to be thinned, diced, packaged, tested, etc. to form a module. Specifically, firstly, the silicon substrate is thinned to 50-200 um in a mechanical grinding or chemical corrosion mode, the thickness uniformity is controlled to be less than +/-5 um, and the surface roughness is less than 100nm; then forming a single chip in a laser or mechanical scribing way; finally, as shown in fig. 12, the module is formed by bonding the FPC board 5 to the FPC board 5 by means of the anisotropic conductive adhesive 6 and packaging.

The present specification also provides an ultrasonic fingerprint identification chip 100, as shown in fig. 1 to 4, including: the ultrasonic sensor 2 is used for transmitting and receiving ultrasonic signals, the ultrasonic sensor 2 is provided with two opposite sides, a first dielectric layer is arranged on one side, a silicon-based substrate 1 is arranged on the other side, and a display screen is arranged above the silicon-based substrate 1 and deviates from the ultrasonic sensor; forming an identification region 10 and a non-identification region 11 on the silicon-based substrate 1, wherein the identification region 10 is used for forming a CMOS pixel unit array 101, and the non-identification region 11 is used for forming a signal processing circuit; ultrasonic sensor 2 is in form the structure that supplies ultrasonic resonance between first dielectric layer and silicon-based substrate 1, ultrasonic signal that ultrasonic sensor 2 sent can follow after the resonance silica-based substrate 1 is spread out, is got into the display screen, get into after being reflected by the target body above the display screen ultrasonic sensor 2.

The ultrasonic fingerprint identification chip 100 can achieve the technical problems solved by the embodiments of the ultrasonic fingerprint identification device, and accordingly achieves the technical effects of the embodiments, which are not described herein again.

Any numerical value recited herein includes all values from the lower value to the upper value that are incremented by one unit, provided that there is a separation of at least two units between any lower value and any higher value. For example, if it is stated that the number of a component or a value of a process variable (e.g., temperature, pressure, time, etc.) is from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, it is intended that equivalents such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 are also expressly enumerated in this specification. For values less than 1, one unit is suitably considered to be 0.0001, 0.001, 0.01, 0.1. These are only examples of what is intended to be explicitly recited, and all possible combinations of numerical values between the lowest value and the highest value that are explicitly recited in the specification in a similar manner are to be considered.

Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. The use of "about" or "approximately" with a range applies to both endpoints of the range. Thus, "about 20 to about 30" is intended to cover "about 20 to about 30", including at least the endpoints specified.

All articles and references disclosed, including patent applications and publications, are incorporated by reference herein for all purposes. The term "consisting essentially of 8230comprises the elements, components or steps identified and other elements, components or steps which do not materially affect the basic novel characteristics of the combination. The use of the terms "comprising" or "including" to describe combinations of elements, components, or steps herein also contemplates embodiments that consist essentially of such elements, components, or steps. By using the term "may" herein, it is intended to indicate that any of the described attributes that "may" include are optional.

It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and many applications other than the examples provided would be apparent to those of skill in the art upon reading the above description. The scope of the present teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are hereby incorporated by reference for all purposes. The omission in the foregoing claims of any aspect of subject matter that is disclosed herein is not intended to forego such subject matter, nor should the inventors be construed as having contemplated such subject matter as being part of the disclosed subject matter.

Claims

1. An ultrasonic fingerprint identification device, comprising:

the ultrasonic sensor forms a structure for ultrasonic resonance between the first medium layer and the second medium layer, ultrasonic signals sent by the ultrasonic sensor can be transmitted out of the second medium layer and enter the third medium layer after resonance, and enter the ultrasonic sensor after being reflected by a target body above the third medium layer.

2. The ultrasonic fingerprint identification device of claim 1 wherein said first dielectric layer is air.

3. The ultrasonic fingerprint identification device of claim 1 wherein said ultrasonic sensor has first and second opposing surfaces, said first surface being in contact with said first dielectric layer, said ultrasonic sensor comprising: edge the second surface extremely protective layer, electrode layer and the piezoelectric layer that stacks gradually between the second surface, the protective layer the electrode layer with the acoustic impedance of piezoelectric layer is close or equals, ultrasonic sensor is along the odd number times of the quarter of its wavelength in the ascending thickness of direction of piling up.

4. The ultrasonic fingerprint identification device of claim 3 wherein said protective layer, said electrode layer and said piezoelectric layer are formed of a polymer, and wherein said ultrasonic sensor has an acoustic impedance of 1 to 10MRayls.

5. The ultrasonic fingerprint identification device of claim 3, wherein the electrode layer is made of metal, and the thickness of the electrode layer is less than 1 μm.

6. The ultrasonic fingerprint identification device of claim 1 wherein said second dielectric layer is a silicon-based substrate.

7. The ultrasonic fingerprint identification device of claim 6 wherein the substrate has an outer profile dimension of 3 to 40mm.

8. The ultrasonic fingerprint identification device of claim 6 wherein the silicon-based substrate has third and fourth opposing surfaces, the third surface facing the ultrasonic sensor, the third surface comprising an identification region for providing a CMOS pixel array and a bottom electrode for electrically coupling the CMOS pixel array to the ultrasonic sensor, and a non-identification region for forming a signal processing circuit electrically connected to the CMOS pixel array and the ultrasonic sensor, the signal processing circuit for providing a driving voltage to the ultrasonic sensor and processing an electrical signal from the CMOS pixel array.

9. The ultrasonic fingerprint identification device according to claim 8, wherein a circuit film layer for forming a CMOS pixel cell array and the signal processing circuit is disposed on the third surface, and an acoustic impedance of the circuit film layer is close to or equal to an acoustic impedance of the silicon-based substrate, and the acoustic impedance of the silicon-based substrate is 21-23MRayls.

10. The ultrasonic fingerprint recognition device of claim 8, wherein said non-recognition area comprises: and the I/0 interface area is used for connecting the FPC circuit board.

11. The ultrasonic fingerprint identification device of claim 1 wherein said third dielectric layer is a display screen.

12. The ultrasonic fingerprint device of claim 11, wherein the thickness of the third dielectric layer is greater than 300um.

13. The ultrasonic fingerprint identification device of claim 1, wherein a glue is disposed between the third dielectric layer and the second dielectric layer, and an acoustic impedance of the glue is between the third dielectric layer and the second dielectric layer.

14. The ultrasonic fingerprint device of claim 13, wherein the glue is a heat-curable epoxy or a UV-curable epoxy, and the glue has a thickness of one quarter of its wavelength.

15. The ultrasonic fingerprint identification device according to claim 13, wherein the glue is a composite film layer of a conductive material and an organic substance, the total thickness of the glue is 5-50 μm, and wherein the thickness of the conductive material is 1-15 um.

16. The ultrasonic fingerprint device of claim 1, wherein a glue is disposed between the third dielectric layer and the second dielectric layer, and an acoustic impedance of the glue is close to or equal to an acoustic impedance of the third dielectric layer.

17. An ultrasonic fingerprint identification chip, characterized by comprising:

the ultrasonic sensor is used for transmitting and receiving ultrasonic signals and provided with two opposite sides, a first medium layer is arranged on one side, a silicon-based substrate is arranged on the other side, and a display screen is arranged above the silicon-based substrate, which is far away from the ultrasonic sensor;