Ultrasonic fingerprint detection sensor and module

Abstract

The present invention provides an ultrasonic fingerprint detection sensor and module, the ultrasonic fingerprint detection sensor includes a glass substrate; an ultrasonic pixel array, arranged on the glass substrate, includes an ultrasonic pixel unit; the ultrasonic pixel unit includes an ultrasonic sensor and an ultrasonic fingerprint detection circuit, the ultrasonic fingerprint detection circuit includes a capacitor and at least four MOS tubes; the first MOS tube is connected to one end of the capacitor; the source and drain of the third and fourth MOS tubes are connected to form a common contact; in the receiving stage of the ultrasonic fingerprint detection circuit, the fourth MOS tube is turned on to form an electrical path between the gate of the first MOS tube and the common contact; and the third MOS tube is turned on by using a timing control signal to raise the common contact potential; in the reading stage, the second MOS tube is turned on to output the fingerprint signal stored in the gate of the first MOS tube. The ultrasonic fingerprint detection sensor made by the TFT process of the embodiment of the present invention can realize the reading of ultrasonic fingerprint signals.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrasonic fingerprint detection sensors, and in particular to an ultrasonic fingerprint detection sensor and a module using the ultrasonic fingerprint detection sensor. Background Art

[0002] Ultrasonic sensors are sensors that convert ultrasonic signals into other energy signals (usually electrical signals). They have the characteristics of high frequency, short wavelength, small diffraction, and especially good directionality, and can be directed as rays. Ultrasonic waves have great penetrating power for liquids and solids, especially for solids that are opaque to sunlight. Based on this characteristic of ultrasonic waves, ultrasonic sensors are widely used.

[0003] Unlike traditional optical or capacitive fingerprint recognition solutions, ultrasonic sensors used in under-screen fingerprint recognition are more popular because of their more flexible environmental application scenarios. Unlike optical fingerprint recognition sensors, which are restricted by the light path and cannot be too thin, ultrasonic sensors do not have this limitation, so under-screen fingerprint recognition sensors can be made thinner as electronic products become thinner. Ultrasonic sensors are also not easily affected by environmental humidity and their sensitivity like capacitive fingerprint sensors.

[0004] As users are increasingly pursuing better experience, they also hope that the area for fingerprint recognition will become larger and larger. Currently, they are pursuing large-array fingerprint recognition chips. The cost advantage of using CMOS technology to make large-array ultrasonic fingerprint chips is obviously weak.

[0005] At present, the domestic large-array under-screen ultrasonic fingerprint recognition module is still in the development stage, and such under-screen ultrasonic fingerprint recognition sensors have not appeared. Summary of the invention

[0006] In view of this, the present application provides an ultrasonic fingerprint detection sensor and module. The ultrasonic fingerprint detection sensor is manufactured using a TFT process, which can reduce the manufacturing cost of the sensor when manufacturing a large-array ultrasonic fingerprint detection sensor.

[0007] In order to achieve the above object, the present invention provides the following technical solutions.

[0008] An ultrasonic fingerprint detection sensor, comprising:

[0009] Glass substrate;

[0010] An ultrasonic pixel array is provided on the glass substrate, and includes a plurality of ultrasonic pixel units; each of the ultrasonic pixel units includes an ultrasonic sensor and an ultrasonic fingerprint detection circuit, and the ultrasonic fingerprint detection circuit includes a capacitor and at least four MOS tubes: a first MOS tube, a second MOS tube, a third MOS tube, and a fourth MOS tube; the ultrasonic fingerprint detection circuit receives at least four corresponding timing control signals: a first drive signal, a bias signal, a second drive signal, and a row selection signal, and the four timing control signals are independent of each other;

[0011] Wherein, the first MOS transistor is used as a source follower transistor, the gate of the first MOS transistor is connected to one end of the capacitor, the gate of the fourth MOS transistor receives the second drive signal, the gate of the third MOS transistor receives the first drive signal, and the source / drain of the third MOS transistor receives the bias signal; the source and drain of the third MOS transistor and the fourth MOS transistor are connected to form a common point, the common point is connected to the electrode corresponding to the ultrasonic sensor, and the gate of the second MOS transistor receives the row selection signal;

[0012] In the receiving stage of the ultrasonic fingerprint detection circuit, at least the second driving signal is used to turn on the fourth MOS tube, so that the gate of the first MOS tube forms an electrical path with the common contact; in the interval in which the common contact and the gate of the first MOS tube form an electrical path, the first driving signal and the bias signal are used to control the turning on of the third MOS tube to raise the potential of the common contact; in the reading stage after the receiving stage, the row selection signal is used to turn on the second MOS tube to output the ultrasonic fingerprint signal stored in the gate of the first MOS tube.

[0013] Preferably, a working cycle of the ultrasonic pixel unit also includes an excitation phase, the ultrasonic sensor receives an excitation signal, and the ultrasonic fingerprint detection circuit uses the first drive signal and the bias signal to control the third MOS tube to provide a steady-state DC potential for the common point.

[0014] Preferably, in the reading phase, the second driving signal controls the fourth MOS transistor to be turned off.

[0015] Preferably, in the receiving stage, the method further comprises using the second driving signal to control the fourth MOS transistor to be turned off, thereby blocking the electrical path between the common point and the gate of the first MOS transistor.

[0016] Preferably, in the receiving stage, the first driving signal has a first pulse signal with a first preset maintenance time, and the first pulse signal has a rising edge and a falling edge; the bias signal has a second pulse signal with a second preset maintenance time, and the second pulse signal has a rising edge and a falling edge, and the bias signal has three-state potentials in the receiving stage: a low potential, a high potential, and a third-state potential.

[0017] Preferably, the first preset holding time is equal to the second preset holding time, and rising edges and falling edges of the first pulse signal and the second pulse signal coincide with each other.

[0018] Preferably, when the second preset holding time is greater than the first preset holding time, the rising edge of the second pulse signal is earlier than the rising edge of the first pulse signal, and the falling edge of the second pulse signal is later than the falling edge of the first pulse signal.

[0019] Preferably, the ultrasonic fingerprint detection circuit further includes a reset stage, in which the gate of the first MOS tube is reset to a reset signal using the drive signal and the bias signal.

[0020] Preferably, in the reset phase, the second driving signal is used to control the fourth MOS transistor to be turned on, so that the common contact and the gate of the first MOS transistor form an electrical path.

[0021] Preferably, the ultrasonic fingerprint detection circuit further includes a second reading phase, using a row selection signal to control the conduction of the second MOS tube, and reading a reset signal of the gate of the first MOS tube in the reset phase.

[0022] Preferably, the capacitor includes at least one of a PIP capacitor, a metal plate capacitor, a PMOS tube capacitor and an NMOS tube capacitor.

[0023] An ultrasonic fingerprint detection module, comprising:

[0024] The ultrasonic fingerprint detection sensor as described in the above embodiment;

[0025] The integrated circuit dedicated chip communicates with the ultrasonic fingerprint detection sensor and is used to generate four timing control signals for the ultrasonic fingerprint detection sensor.

[0026] In summary, in the ultrasonic fingerprint detection sensor of the embodiment of the present invention, the ultrasonic fingerprint detection circuit in the ultrasonic pixel unit includes at least four MOS tubes and a capacitor, which cooperate with the signal given by the integrated circuit dedicated chip and the corresponding ultrasonic sensor to stimulate the ultrasonic sensor in the ultrasonic pixel unit to generate ultrasonic waves, and control the ultrasonic fingerprint detection circuit to receive the ultrasonic signal returned from the finger, and output it to the corresponding integrated circuit dedicated chip to process the fingerprint signal.

[0027] The ultrasonic fingerprint detection circuit in the ultrasonic pixel unit of the present application is manufactured using TFT technology, which can reduce the manufacturing cost of manufacturing a larger area ultrasonic pixel array. This large-area ultrasonic pixel array can provide a larger range of fingerprint detection areas, and the corresponding increased size can be flexibly adjusted according to the specifications of the applied electronic products to provide a corresponding larger range of fingerprint detection areas.

[0028] Based on the above description of the ultrasonic fingerprint detection circuit, the ultrasonic fingerprint detection circuit includes at least four MOS tubes, corresponding to at least four different timing control signals to control the ultrasonic fingerprint detection circuit to work in different stages. Relative to a working cycle of the ultrasonic fingerprint detection circuit, it will at least include a receiving stage and a reading stage. The fourth MOS tube can isolate the first MOS tube from the ultrasonic sensor to avoid interference from factors such as fingers or the outside world when the ultrasonic fingerprint signal stored in the gate of the first MOS tube is received or read, thereby improving the signal-to-noise ratio of the collected fingerprint signal.

[0029] In this application, many different embodiments of controlling the first drive signal and the bias signal of the third MOS tube are introduced. In these embodiments, the preferred implementation is the situation where the rising edge and the falling edge of the pulse signal in the first drive signal and the bias signal are not synchronized. When these timing signals come from the dedicated chip of the integrated circuit or the ultrasonic fingerprint detection sensor is required to convert the timing signal source provided by the dedicated chip of the integrated circuit, the rising edge and the falling edge of the pulse signal are completely synchronized, which puts forward more stringent requirements for the generation circuit of the timing control signal. A slight error in the timing will cause the ultrasonic fingerprint detection circuit to fail to work properly at a certain stage. The rising edge and the falling edge of these pulse signals are completely synchronized, which is not only related to the design of the circuit related to the generation of the timing signal, but also has a great relationship with the manufacturing process of the circuit. Therefore, reducing the pulse synchronization requirements for the first drive signal and the bias signal of the third MOS tube can reduce the design and process difficulty of the signal related to the timing signal generated by this dedicated chip of the integrated circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The drawings described herein are only for explanation purposes and are not intended to limit the scope of the present invention in any way. In addition, the shapes and proportional dimensions of the components in the drawings are only for illustration purposes and are used to help understand the present invention. They do not specifically limit the shapes and proportional dimensions of the components of the present invention. Under the guidance of the present invention, those skilled in the art can select various possible shapes and proportional dimensions to implement the present invention according to specific circumstances. In the drawings:

[0031] Figure 1 A schematic diagram of a top view of an ultrasonic fingerprint detection sensor according to a non-limiting embodiment of the present invention;

[0032] Figure 2 for Figure 1 A schematic cross-sectional structure diagram of an ultrasonic fingerprint detection sensor is shown;

[0033] Figure 3 A schematic structural diagram of an ultrasonic pixel unit included in an ultrasonic fingerprint detection sensor according to a non-limiting embodiment of the present invention;

[0034] Figure 4A is a circuit topology diagram of an ultrasonic fingerprint detection circuit in an ultrasonic fingerprint detection sensor according to a first non-limiting embodiment of the present invention;

[0035] FIG. 4B to FIG. 4E is a circuit topology diagram of an ultrasonic fingerprint detection circuit in an ultrasonic fingerprint detection sensor according to a second non-limiting embodiment of the present invention;

[0036] Figure 5 for Figure 4A The control timing diagram of the ultrasonic fingerprint detection circuit shown;

[0037] Figure 6 for FIG. 4B to FIG. 4D The control timing diagram of the ultrasonic fingerprint detection circuit shown;

[0038] Figure 7 for Figure 4B and 4D A control timing diagram of the ultrasonic fingerprint detection circuit shown;

[0039] Figure 8 for Figure 4B and 4D Another control timing diagram of the ultrasonic fingerprint detection circuit is shown. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0041] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only embodiment.

[0042] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0043] The embodiment of the present invention provides an ultrasonic fingerprint detection sensor and a method for performing fingerprint detection using the ultrasonic fingerprint detection sensor. The ultrasonic fingerprint detection sensor can be used in electronic devices including but not limited to mobile smart phones, tablet electronic devices, computers, GPS navigators, personal digital assistants, smart wearable devices, etc. for fingerprint recognition, and can realize fingerprint unlocking, user identity authentication, permission acquisition, etc.

[0044] For example, in a feasible implementation scenario, an ultrasonic fingerprint detection sensor is configured in a smartphone. The smartphone can obtain the user's fingerprint feature information based on the ultrasonic fingerprint detection sensor to match it with the stored fingerprint information to achieve identity authentication of the current user, thereby confirming whether he has the corresponding authority to perform screen unlocking, user identity authentication, permission acquisition and other related operations on the smartphone.

[0045] like Figures 1 to 3 As shown, the ultrasonic fingerprint detection sensor includes a glass substrate 1 and an ultrasonic pixel array 2 disposed on the glass substrate 1, and the ultrasonic pixel array 2 includes a plurality of ultrasonic pixel units 201. The plurality of ultrasonic pixel units 201 can be arranged in a regular form of multiple rows and columns on the glass substrate 1. The glass substrate 1 uses a TFT process to manufacture a large-area ultrasonic pixel array.

[0046] Furthermore, the ultrasonic fingerprint detection sensor is also provided with a pin 3 for connecting to an integrated circuit dedicated chip, and the integrated circuit dedicated chip provides a signal source for the ultrasonic fingerprint detection circuit to generate a timing control signal. When the ultrasonic fingerprint detection module composed of the ultrasonic fingerprint detection sensor and the integrated circuit dedicated chip is applied to the corresponding electronic device, the integrated circuit dedicated chip communicates with the core processing chip in the electronic device to realize the detection and identification of ultrasonic fingerprints.

[0047] like Figure 2 and Figure 3 As shown, the ultrasonic fingerprint detection sensor includes an ultrasonic pixel array. The ultrasonic pixel units 201 in the ultrasonic pixel array each include an ultrasonic sensor (Sensor) and an ultrasonic fingerprint detection circuit 201a electrically connected to the ultrasonic sensor. Figure 1 and Figure 2 As shown, the ultrasonic sensor may include a bottom electrode, a piezoelectric material 4, an electrode 5, a protective film 6 and a cover layer 7 stacked in sequence from bottom to top. The piezoelectric material 4 may be made of PVDF. Figure 2 The electrode 5 shown in the figure can be understood as a top electrode. The piezoelectric material 4 is disposed between the electrode 5 and the bottom electrode 201b. The cover layer 7 can be specifically a cover glass for pressing or touching by a user's finger. The protective film 6 isolates the electrode 5 from the cover layer 7, which can buffer the pressing or touching operation of the user's finger and protect the electrode 5 and the underlying piezoelectric material 4, the ultrasonic pixel array 2 and other structures.

[0048] The ultrasonic fingerprint detection circuit 201a is a part of the ultrasonic pixel unit. This ultrasonic fingerprint detection circuit 201a corresponds one-to-one with the patterned bottom electrode to form an array-type ultrasonic pixel array. Several ultrasonic pixel units 201 are independent of each other. The "independent of each other" means that there is no signal connection or signal sharing relationship between the several ultrasonic pixel units 201, and the ultrasonic fingerprint detection circuit 201a only receives the electrical signal transmitted from the bottom electrode of the ultrasonic sensor in the corresponding ultrasonic pixel unit. The ultrasonic sensor is electrically connected to the ultrasonic detection circuit in the ultrasonic pixel unit through the patterned bottom electrode. An excitation phase is included in a working cycle of the ultrasonic detection circuit. In the excitation phase, the electrode 5 receives an AC excitation voltage signal (Excitation Signal), and the ultrasonic detection circuit provides a stable DC low potential to the bottom electrode of the corresponding ultrasonic sensor in the excitation phase.

[0049] In the receiving stage, the ultrasonic fingerprint detection circuit receives the ultrasonic fingerprint signal of the ultrasonic sensor of the corresponding bottom electrode. Figure 3 Only a schematic diagram of the layout of the ultrasonic fingerprint detection circuit in an ultrasonic pixel unit is shown. Figure 3The layout diagram shown mainly refers to Figure 4A The ultrasonic fingerprint detection circuit is shown in FIG. 1 , and the layout of the ultrasonic fingerprint detection circuit in a specific single ultrasonic pixel unit is not limited thereto. Each ultrasonic fingerprint detection circuit 201a includes at least three MOS tubes. Figure 4A As shown, in a feasible embodiment, each ultrasonic fingerprint detection circuit 201a may include only three MOS transistors, namely, a first MOS transistor M1, a second MOS transistor M2 and a third MOS transistor M3. In another feasible embodiment, as FIG. 4B to FIG. 4D As shown, each ultrasonic fingerprint detection circuit 201a further includes a fourth MOS transistor M4 on the basis of the three MOS transistors in the above embodiment, that is, each ultrasonic fingerprint detection circuit 201a includes at least four MOS transistors.

[0050] In this embodiment, all MOS transistors are preferably MOS transistors of the same type, for example, all are N-type MOS transistors or all are P-type MOS transistors. Figure 4E The ultrasonic fingerprint detection circuit topology diagram shown is similar to Figure 4B The ultrasonic fingerprint detection circuit topology shown is roughly the same, only Figure 4B The NMOS tube in the ultrasonic fingerprint detection circuit is replaced by a PMOS tube. In a preferred implementation, the same type of MOS tube is used in the ultrasonic fingerprint detection circuit, which can reduce the complexity of the process of manufacturing the ultrasonic fingerprint detection circuit using the TFT process to a certain extent. Of course, in other feasible embodiments of the ultrasonic fingerprint detection circuit, some MOS tubes can be N-type MOS tubes and some MOS tubes can be P-type MOS tubes, and the present invention is not limited to this.

[0051] For MOS tubes made by TFT technology, for those skilled in the art, the source and drain of the MOS tube can be interchanged with each other. Therefore, in all technical solutions disclosed herein, when describing the connection relationship of the source of the MOS tube and the connection relationship of the corresponding drain, it can also be replaced by the connection relationship of the drain of the MOS tube and the connection relationship of the corresponding source. Here, no further description of the common technical knowledge known to those skilled in the art is given. This connection relationship between the source and the drain should be a mere change of the text of the description method of the technical solution disclosed in this application without changing the substantial function of the circuit.

[0052] The ultrasonic fingerprint detection circuit 201a receives at least three corresponding timing control signals respectively, and the at least three timing control signals are independent of each other to control at least three MOS tubes to realize different working stages of the ultrasonic fingerprint detection circuit. Among them, each ultrasonic fingerprint detection circuit 201a receives at least three corresponding timing control signals respectively, which can be: a first drive signal, a bias signal, and a row selection signal.

[0053] like Figure 4A As shown, in an embodiment including only three MOS transistors, there are also three timing control signals. In a specific feasible implementation scenario, the three timing control signals are: a row selection signal ROW connected to the gate of the second MOS transistor M2, a first drive signal OD_1 (OverDrive) connected to the gate and input terminal of the third MOS transistor M3, and a bias signal Bias.

[0054] In the three MOS tubes, Figure 4A In the illustrated embodiment of the N-type MOS tube, the drain of the second MOS tube M2 serves as an input electrode connected to the source of the first MOS tube M1, and the source serves as an output electrode. The source of the third MOS tube M3 receives the bias signal Bias, and the drain is connected to the gate of the first MOS tube M1. The connection relationship between the three MOS tubes and the ultrasonic sensor is: a common contact is formed between the patterned bottom electrode in the ultrasonic sensor and the gate of the first MOS tube M1 and the drain of the third MOS tube M3. Specifically, the gate of the first MOS tube M1 is connected to the drain of the ultrasonic sensor and the third MOS tube M3, the source is connected to the drain of the second MOS tube M2, and the drain is connected to a DC power supply Vcc with a constant voltage. The source of the second MOS tube M2 is used to output a signal Dn, which is the output end of this ultrasonic fingerprint detection circuit.

[0055] The voltage value of the constant voltage DC power supply Vcc can be set and selected according to the actual situation, for example, it can be selected from 6V-12V, and its function is to make the first MOS tube M1 always work in the saturation region, so that the first MOS tube M1 forms a source follower device (Source Follower). In this way, the signal stored in the gate of the first MOS tube M1 can be output from the source of the second MOS tube M2 when the second MOS tube M2 is turned on or turned on.

[0056] The above is the timing control signal input and structural connection relationship when all three MOS tubes are N-type MOS tubes, but this embodiment is not limited to this. When all three MOS tubes are P-type MOS tubes, the three timing control signals: the row selection signal ROW, the first drive signal OD_1 and the bias signal Bias, are respectively connected to the gate of the second MOS tube M2, the gate and the drain of the third MOS tube M3. The structural connection relationship is: the gate of the first MOS tube M1 is connected to the source of the ultrasonic sensor and the third MOS tube M3, the drain is connected to the source of the second MOS tube M2, and the source is connected to the DC power supply Vcc with a constant voltage. In the embodiment where all three MOS tubes are P-type MOS tubes, the source of the second MOS tube M2 is connected to the drain of the first MOS tube M1, and the drain serves as the output end of the ultrasonic fingerprint detection circuit. The drain of the third MOS tube M3 serves as the input electrode for receiving the bias signal Bias, and the source is connected to the gate of the first MOS tube M1. When Figure 4A The MOS tube in is replaced by a P-type MOS tube, and the corresponding control timing diagram is not given here. Figure 5 For Figure 4A The corresponding timing control diagram in the ultrasonic fingerprint detection circuit topology diagram is shown.

[0057] In another class of embodiments, for example, FIG. 4B to FIG. 4D In this type of embodiment, the ultrasonic fingerprint detection circuit includes four MOS tubes, and there are four timing control signals, namely: a row selection signal ROW connected to the gate of the second MOS tube M2, a first drive signal OD_1 and a bias signal Bias connected to the gate and input of the third MOS tube M3, and a second drive signal OD_2 connected to the gate of the fourth MOS tube M4.

[0058] Similarly, when the four MOS tubes are FIG. 4B to FIG. 4D In the illustrated embodiment of the N-type MOS tube, the drain of the second MOS tube M2 is connected to the source of the first MOS tube M1, and the source serves as the output end of the ultrasonic fingerprint detection circuit. The source of the third MOS tube M3 receives the bias signal Bias, and the drain is connected to the gate of the first MOS tube M1. Four timing control signals: row selection signal ROW, first drive signal OD_1, bias signal Bias, second drive signal OD_2, are respectively connected to the gate of the second MOS tube M2, the gate and source of the third MOS tube M3, and the gate of the fourth MOS tube M4. The connection relationship between the four MOS tubes and the ultrasonic sensor is as follows: on the basis of the above three MOS tubes, the fourth MOS tube M4 is arranged between the first MOS tube M1 and the ultrasonic sensor. The fourth MOS tube M4 is connected in series with the third MOS tube M3, and the ultrasonic sensor is connected between the third MOS tube M3 and the fourth MOS tube M4, and the three share a connection point. Specifically, the drain of the fourth MOS tube M4 is connected to the gate of the first MOS tube M1, and the source is connected to the drain of the ultrasonic sensor and the third MOS tube M3.

[0059] The four MOS tubes are as follows Figure 4EIn the illustrated embodiment of the P-type MOS tube, the source of the second MOS tube M2 is connected to the drain of the first MOS tube M1, and the drain serves as the output end of the ultrasonic fingerprint detection circuit. The drain of the third MOS tube M3 receives the bias signal Bias, and the source is connected to the drain of the fourth MOS tube M4; the gate of the fourth MOS tube is linked to the second drive signal OD_2. Four timing control signals: row selection signal ROW, first drive signal OD_1, bias signal Bias, second drive signal OD_2, are respectively connected to the gate of the second MOS tube M2, the gate and drain of the third MOS tube M3, and the gate of the fourth MOS tube M4. The connection relationship between the four MOS tubes and the ultrasonic sensor is: the gate of the first MOS tube M1 is connected to the source of the fourth MOS tube M4, the drain is connected to the source of the second MOS tube M2, and the source is connected to the DC power supply Vcc of the constant voltage. The drain of the fourth MOS tube M4 is connected to the ultrasonic sensor and the source of the third MOS tube M3.

[0060] exist Figure 4E In the figure, only the embodiments of ultrasonic fingerprint detection circuits of different types of MOS tubes are illustrated. As mentioned above, when a thin film transistor is manufactured by a TFT process, the positions of the drain and source of the MOS tube can be easily interchanged for those skilled in the art. For the interchange of the positions of the drain and source of the MOS tube, if the substantial function achieved by the position change combined with the timing control signal is consistent with the technical solution disclosed in this embodiment, it should be considered that such a deformed ultrasonic fingerprint detection circuit has also been disclosed by this application.

[0061] That is to say, in FIG. 4B to FIG. 4E In the illustrated embodiment including four MOS transistors, the first MOS transistor M1 serves as a source follower transistor; the gate of the second MOS transistor M2 receives the row selection signal ROW; the gate of the third MOS transistor M3 receives the first drive signal OD_1, and the source / drain receives the bias signal Bias (as mentioned above, whether the source receives the bias signal Bias or the drain receives the bias signal Bias depends on the type of the third MOS transistor M3); the gate of the fourth MOS transistor M4 receives the second drive signal OD_2; the source and drain of the third MOS transistor and the fourth MOS transistor are connected to form a common point, and the common point is electrically connected to an electrode of the ultrasonic sensor (Sensor).

[0062] Combination Figure 5 and Figure 3 As shown, corresponding to Figure 4AWhen the ultrasonic fingerprint detection circuit includes only three MOS tubes, the corresponding control timing can be only three. Under these three timing control signals, in one working cycle of the ultrasonic fingerprint detection circuit, the first MOS tube M1 stores the fingerprint peak signal output by the ultrasonic sensor in the receiving phase, the second MOS tube M2 outputs the fingerprint peak signal stored in the first MOS tube M1 in the reading phase, and the third MOS tube M3 resets the gate signal of the first MOS tube M1 in the reset phase.

[0063] Corresponding to, FIG. 4B to FIG. 4D middle, Figures 6 to 8 The timing control diagram for controlling the ultrasonic fingerprint detection circuit shown in the figure includes at least four timing control signals: the four timing control signals are respectively a row selection signal ROW connected to the gate of the second MOS tube M2, a first drive signal OD_1 and a bias signal Bias connected to the gate and input terminal of the third MOS tube M3, and a second drive signal OD_2 connected to the gate of the fourth MOS tube M4.

[0064] Among them, the timing control signal connected to the gate of the second MOS tube M2 - the row selection signal ROW can control the conduction or shutdown of the second MOS tube M2 to control whether the fingerprint signal stored in the gate of the first MOS tube M1 and the capacitor is output. Specifically, when the voltage of the row selection signal ROW is high, the second MOS tube M2 is turned on. When the voltage of the row selection signal ROW is low, the second MOS tube M2 is turned off.

[0065] It should be uniformly explained that, among the four timing control signals, the first driving signal OD_1, the second driving signal OD_2 and the row selection signal ROW are used to control the gates of the third MOS tube M3, the fourth MOS tube M4 and the second MOS tube M2 respectively. The high potential and the low potential of these three signals are the voltage thresholds for turning on and off the MOS tubes respectively. The specific values ​​of the high potential and the low potential can be set according to the threshold voltage of the MOS tube in the ultrasonic fingerprint detection circuit actually manufactured using the TFT process.

[0066] In combination with the above description, the ultrasonic fingerprint detection circuit 201a of the embodiment of the present invention only includes two electronic components, MOS tube and capacitor C1, and does not include other types of electronic components, such as diodes. The following describes the process of implementing fingerprint detection using the ultrasonic fingerprint detection sensor of the above embodiment of the present invention.

[0067] A working cycle of an ultrasonic pixel unit is described and illustrated by a control timing diagram of an ultrasonic pixel unit in an ultrasonic pixel unit and an ultrasonic fingerprint detection circuit therein. In the ultrasonic pixel unit, an ultrasonic sensor receives an ultrasonic fingerprint signal and converts it into an electrical signal, and the ultrasonic fingerprint detection circuit detects the electrical signal. This working cycle includes an excitation phase, a receiving phase, and a reading phase. In the receiving phase, the first MOS tube M1 and the capacitor store the fingerprint peak signal output by the ultrasonic sensor. In this receiving phase, since the voltage ΔV of the fingerprint peak signal is generally weak and difficult to be accurately detected, the potential of the common point, that is, the potential of the ultrasonic fingerprint signal transmitted by the sensor to the ultrasonic fingerprint detection circuit, can be increased by controlling the first driving signal and the bias signal connected to the third MOS tube, so as to facilitate the use of the first MOS tube gate of the TFT process to temporarily store the ultrasonic fingerprint signal. In the reading phase, the second MOS tube M2 is turned on and outputs the fingerprint peak signal stored in the gate of the first MOS tube M1. In the reading phase, the second MOS tube M2 is turned on by the row selection signal to output the fingerprint peak signal stored in the gate of the first MOS tube M1 and the capacitor.

[0068] The following first combines Figure 4A as well as Figure 5 The control timing diagram of Figure 4A The specific working state of the topology of the ultrasonic fingerprint detection circuit shown is described and illustrated.

[0069] like Figure 4A As shown in the figure, the ultrasonic fingerprint detection circuit only includes three MOS tubes. Figure 5 At this time, the bias signal Bias is at a stable DC voltage value (relative to the excitation signal, a stable low potential), and the first drive signal OD_1 is at a high level, so that the third MOS tube is in a fully conductive state. At this time, the ultrasonic sensor corresponding to this ultrasonic fingerprint detection circuit receives the excitation signal.

[0070] The receiving phase is Figure 5The time interval T2 in the first driving signal OD_1 and the bias signal Bias are synchronized as a whole, and the rising edge and the falling edge basically coincide. At this time, the third MOS tube M3 acts as a diode to provide the function of ultrasonic fingerprint peak detection. Specifically, the first driving signal OD_1 and the bias signal Bias each include a first boost pulse in the reading stage, and the starting time, maintenance time and voltage value of the two first boost pulses are the same, and the maintenance time of the first boost pulse is T0. Under the action of the first boost pulse, the third MOS tube M3 raises the voltage of the common point, and detects the fingerprint signal received by the ultrasonic sensor at this time during the duration of the first boost pulse of the first driving signal OD_1. In this receiving stage, if the DC potential of the fingerprint peak signal is small, it is not conducive to the subsequent detection and reading of the MOS tube using TFT. The first driving signal OD_1 and the bias signal Bias are used to control the third MOS tube M3 to work in a diode-like state in the receiving stage, raise the potential of the common point, so that the potential of the fingerprint signal output subsequently is higher. At the end of the receiving stage, in order to prevent the fingerprint signal from being lost over time due to leakage, the first driving signal OD_1 is at a low potential, and the bias signal Bias is raised to a high potential. In principle, the third MOS tube M3 is turned off to reduce its leakage.

[0071] In correspondence Figure 5 In the reading phase of the time interval T3, the row selection signal ROW is in a high potential state, and the second MOS tube M2 is turned on. The first drive signal OD_1 maintains a low level, and the bias signal Bias switches to the third state potential. Figure 4A The common point is directly connected to the capacitor and the gate of the first MOS tube, and the first MOS tube acts as a Source-Follower. The source of the first MOS tube will follow the fingerprint signal on the gate (i.e., the common point). Therefore, the fingerprint signal can be read by reading the potential of the source of the first MOS tube.

[0072] like FIG. 4B to FIG. 4D As shown, in the embodiment including four MOS transistors, each ultrasonic fingerprint detection circuit 201a receives four independent timing control signals. Further, in order to prevent external factors such as user's finger, external environment, etc. from affecting the gate of the first MOS transistor M1 and the fingerprint signal stored in the capacitor during the reading stage, the fourth MOS transistor M4 can be turned off before the reading stage to isolate the external interference to the ultrasonic fingerprint detection circuit.

[0073] Receiving phase correspondence Figure 6In the intervals T2 and T3 shown, after the gate of the first MOS tube completes receiving the ultrasonic fingerprint signal, the fourth MOS tube M4 is turned off at the end of the receiving phase (interval T3) to isolate the ultrasonic sensor from the first MOS tube M1, thereby preventing the noise signal generated by the ultrasonic sensor from being transmitted to the gate and capacitor of the first MOS tube M1 due to interference from the external environment, thereby improving the signal-to-noise ratio of the detected ultrasonic fingerprint signal.

[0074] exist Figure 6 As shown in the control timing diagram, FIG. 4B to FIG. 4D The ultrasonic fingerprint detection circuit shown also includes a reset phase T5. Figure 6 In the embodiment of the control timing diagram shown, the reset phase is after the read phase. In the reset phase T5, the second drive signal OD_2 controls the fourth MOS transistor to be turned on, and the first drive signal OD_1 and the bias signal correspondingly control the third MOS transistor to be turned on, resetting the gate of the first MOS transistor electrically connected to the common point to the expected reset potential.

[0075] correspond Figure 6 In the reset phase shown in FIG, a second reading phase (T6) is provided after the reset phase. In the second reading phase, the voltage value of the first driving signal OD_1 is less than the voltage value of the bias signal Bias. The row selection signal ROW is at a high level, and the second MOS transistor M2 is turned on, thereby reading the reset signal.

[0076] By resetting, the influence of other factors on the fingerprint signal during the detection process can be filtered out and the background noise can be reduced. This timing controls the working state of the four MOS tubes, allowing the ultrasonic fingerprint detection circuit to achieve fingerprint peak signal detection with a higher signal-to-noise ratio.

[0077] Figure 6 The T1 interval shown in corresponds to Figure 5 In the T1 interval shown in FIG. , the added second driving signal OD_2 controls the fourth MOS tube to turn on. Figure 6 T2 and T3 correspond to Figure 5 The receiving phase T2 shown in FIG. Figure 5 The differences have been described in the above content, so I will not repeat them here. Figure 5 The excitation phase and the receiving phase are basically the same, so they will not be repeated here.

[0078] like Figure 4B and Figure 4D As shown in FIG. 1 , several different connection methods of the second electrode of capacitor C1 are shown. Figure 4B and Figure 4D As shown, the second electrode of the capacitor C1 can be connected to the row selection signal ROW.

[0079] In addition, if Figure 4C As shown, in another feasible embodiment, the second electrode of the capacitor C1 can be connected to a timing control signal V2, and the potential of the gate of the first MOS transistor M1 can be directly raised to a preset potential value through the timing control signal V2.

[0080] like Figure 4D As shown, the second electrode of the capacitor C1 can also be grounded. In this embodiment, the capacitor C1 is grounded, so that the function of the capacitor C1 becomes pure and single. The capacitor C1 only holds the fingerprint signal stored in the gate of the first MOS tube M1, and the function of raising the gate potential of the first MOS tube M1 is completed by the third MOS tube M3. Figure 4B and Figure 4D The other end of the capacitor is connected in a relatively Figure 4C For example, one timing control signal (control signal V2) can be reduced to simplify the circuit structure for generating the timing control signal.

[0081] It should be particularly emphasized that the capacitor C1 in these embodiments is not the parasitic capacitance of the MOS tube in the ultrasonic fingerprint detection circuit or the parasitic capacitance in the structure formed by the entire ultrasonic fingerprint detection circuit using the TFT process. The capacitance value of this capacitor has a direct impact on the detection of ultrasonic signals in the ultrasonic fingerprint detection circuit. Whether it is the parasitic capacitance of the MOS tube or the parasitic capacitance of the structure in the ultrasonic fingerprint detection circuit, when the ultrasonic fingerprint detection circuit works normally, its parasitic capacitance value will not be very large, and with the fluctuation of the TFT manufacturing process, the parameters of the parasitic capacitance will also change, making it difficult to accurately or precisely control the capacitance value of the parasitic capacitance.

[0082] Therefore, in the embodiments of the ultrasonic fingerprint detection circuit described above, capacitor C1 is not a parasitic capacitor. The capacitor C1 in these embodiments can be manufactured using the TFT process to form a PIP capacitor or a metal plate capacitor. Alternatively, capacitor C1 can be manufactured using a PMOS tube capacitor and an NMOS tube manufactured using the TFT process. If capacitor C1 is manufactured using a PMOS tube capacitor and an NMOS tube capacitor, the body end (Body), source (Source), and drain (Drain) are connected together to form a two-terminal element, which is equivalent to a capacitor. In this way, the capacitance value of capacitor C1 is adjusted by changing the area of ​​W multiplied by L of the MOS tube to reach a preset capacitance value.

[0083] against FIG. 4B to FIG. 4D In the embodiment of the ultrasonic fingerprint detection circuit shown in , at least four MOS transistors are included: a first MOS transistor, a second MOS transistor, a third MOS transistor and a fourth MOS transistor. FIG. 4B to FIG. 4D Corresponding Figure 6 The timing control signal diagram shown in the figure is supplemented with Figure 7 and Figure 8 Two other timing control signal diagrams are shown.

[0084] like Figure 7 In the excitation phase TX shown, the ultrasonic fingerprint detection circuit operates through the timing signal and cooperates with the ultrasonic sensor to receive the excitation signal. In this phase, the first drive signal OD_1 and the second drive signal OD_2 respectively control the third MOS tube M3 and the fourth MOS tube M4 to be turned on. At this time, the common point is maintained at a stable low potential.

[0085] In the receiving stage of the ultrasonic fingerprint detection circuit ( Figure 7 and Figure 8 In the RX phase of the ultrasonic fingerprint detection circuit, the second driving signal OD_2 is at a high level, and the gate of the first MOS tube M1 forms an electrical path with the common contact. When the ultrasonic fingerprint detection circuit is receiving, the first driving signal OD_1 and the bias signal Bias are as follows: Figure 7 Specifically, the first driving signal OD_1 has a first pulse signal with a first preset holding time. The first pulse signal has a rising edge and a falling edge. The bias signal Bias has a second pulse signal with a second preset holding time in this receiving phase. The second pulse signal has a rising edge and a falling edge. Figure 7 In the control timing diagram shown, the second preset holding time of the second pulse signal is greater than the first preset holding time of the first pulse. In this receiving phase, the third MOS tube is controlled to work in a diode-like state, and the potential of the common point is raised during the first preset holding time. Figure 6 The difference is, Figure 6 The rising edge and falling edge of the second pulse signal in the bias signal in the first driving signal OD_1 need to completely coincide with the rising edge and falling edge of the first pulse signal in the first driving signal OD_2. Figure 7 In the timing embodiment shown, the second preset holding time of the second pulse signal is greater than the first preset holding time of the first pulse signal, and the rising edge of the second pulse signal is earlier than the rising edge of the first pulse signal, and the falling edge of the second pulse signal is later than the falling edge of the first pulse signal, so that the peak detection function can also be achieved. Such processing reduces the requirements for the coincidence of the rising edge or falling edge of the pulse signal between the first drive signal OD_1 and the bias signal. Specifically, in Figure 7In the timing diagram shown, in the receiving stage, the rising edge of the first pulse signal in the first drive signal OD_1 directly jumps from a low potential to a high potential. The rising edge of the second pulse signal included in the bias signal Bias rises from a low potential to a high potential, and the rising edge can be relatively slow. After the second pulse signal maintains the second preset maintenance time (greater than the first preset maintenance time of the first pulse signal of the first drive signal OD_1), its falling edge drops from a high potential to a third state potential. Among them, the rising edge of the second pulse signal must be earlier than the rising edge of the first pulse signal, and the falling edge must be later than the falling edge of the first pulse signal. In this way, the first pulse signal is located in the second pulse signal interval as a whole. Through the timing of the first drive signal OD_1 and the bias signal Bias, the third MOS tube M3 is controlled to perform peak detection, and the detected signal is fixed to the common point. At the same time, the second drive signal OD_2 is also at a high level, which controls the fourth MOS tube to be turned on. Therefore, the potential of the gate of the first MOS tube is also the potential on the common point.

[0086] Figure 7 The receiving stage RX shown in FIG. 1 is only an embodiment of the corresponding first driving signal OD_1 and the bias signal Bias, and is not limited thereto. In the receiving stage, the first MOS tube M1 and the capacitor C1 store the potential of the common point. In the reading stage ( Figure 7 and Figure 8 In the READ phase in the sensor, the row selection signal ROW is controlled to be high level, the second MOS tube M2 is turned on, and the fingerprint signal stored in the gate of the first MOS tube M1 and the capacitor C1 is read. While reading, the gate voltage of the first MOS tube M1 is raised through the potential at the other end of the capacitor C1, so that the first MOS tube M1 is in the saturation region. In this reading phase, the second drive signal OD_2 is low level, the fourth MOS tube M4 is turned off, and the first MOS tube M1 is isolated from the ultrasonic sensor to avoid the influence of noise caused by external factors.

[0087] Here Figure 7 The illustrated ultrasonic fingerprint detection circuit also includes a reset phase in one working cycle. The reset phase illustrated here is located after the reading phase. The second driving signal OD_2 is at a high potential, and the fourth MOS tube M4 is turned on. At this time, the fingerprint signal of the gate of the first MOS tube is cleared, that is, the potential on the gate is a reset signal.

[0088] Here Figure 7 A working cycle of the ultrasonic fingerprint detection circuit shown in the figure also includes a second reading phase after the reset phase described above. In the second reading phase, the row selection signal is turned on, the second MOS tube M2 is turned on, and the reset signal on the gate of the first MOS tube M1 in the reset phase is read.

[0089] exist Figure 7The control timing diagram shown is relative to Figure 5 and Figure 6 For the timing control embodiment shown, Figure 7 The timing control diagram shown does not require the rising edge and falling edge of the first pulse signal and the second pulse signal in the bias signal Bias and the first drive signal OD_1 to completely coincide with each other during the receiving stage. Instead, the rising edge of the second pulse signal is controlled to be earlier than the rising edge of the first pulse signal, and the falling edge is controlled to be later than the falling edge of the first pulse signal, thereby greatly reducing the accuracy requirements of the timing control signal and making the timing control simple and flexible.

[0090] To achieve the same or equivalent purpose as above, Figure 8 The timing control diagram shown is similar to Figure 7 The difference is that the two timing control signals for the third MOS tube: the first drive signal OD_1 and the bias signal Bias and Figure 7 The first driving signal OD_1 and the bias signal Bias for the third MOS transistor shown in FIG. 1 are slightly different. Figure 8 The first driving signal OD_1 and the bias signal Bias are shown in the receiving stage RX, and the bias signal Bias does not set the second pulse signal in the receiving stage RX.

[0091] Specifically, see Figure 8 In the receiving stage RX shown, the first driving signal OD_1 is provided with a first pulse signal of a first preset holding time. The first pulse signal has a rising edge and a falling edge. The bias signal Bias is a stable preset value potential, and the third MOS tube M3 works in the MOS tube state. In this embodiment, the preset value potential is lower than the high potential signal of the first pulse signal. In this way, when the first driving signal OD_1 generates a first pulse signal, the third MOS tube M3 is turned on and the gate potential of the first MOS tube M1 is raised (at this time, the fourth MOS tube M4 is in the on state). In the receiving stage, the level of the first driving signal OD_1 outside the first pulse is lower than the potential of the bias signal Bias, and the third MOS tube M3 is turned off.

[0092] Likewise, Figure 8 In the receiving stage shown in the figure, the bias signal Bias is a stable preset value potential and has no Figure 7 The second pulse signal shown in . Figure 8 The timing control diagram shown is relative to Figure 7 The control signal of the timing control diagram shown is simpler and has lower requirements on the accuracy of the timing control signal.

[0093] As described above Figures 6 to 8In the control timing diagram, a working cycle of the ultrasonic fingerprint detection circuit may also include a reset phase and a second reading phase. Here, the positions of the reset phase and the second reading phase relative to the receiving phase and the reading phase described above in a working cycle can be changed, and are not limited to the implementation examples given here. The main purpose of adding a reset phase and a second reading phase in a working cycle or several working cycles is to obtain the background noise and / or noise introduced by external factors when the ultrasonic fingerprint detection circuit itself is working, and to improve the signal-to-noise ratio of the ultrasonic fingerprint signal finally detected by the ultrasonic fingerprint detection sensor. Therefore, no further examples and explanations of the implementation examples of the reset phase and the second reading phase are given here. Other conventional adjustments and modifications of the reset phase and / or the second reading phase by other technicians in this field should be considered to be disclosed by the embodiments described herein.

[0094] contrast Figure 4A and FIG. 4B to FIG. 4D , a fourth MOS tube M4 is added in the topology diagram of the ultrasonic fingerprint detection circuit. As described above, combined with Figures 6 to 8 As shown in the control timing, the fourth MOS tube M4 can isolate the first MOS tube M1 from the ultrasonic sensor at the end of the receiving stage and the reading stage to avoid the influence of external factors. The receiving or reading process of the fingerprint signal is not affected by external noise factors such as the finger or the outside world, thereby improving the signal-to-noise ratio of the detected fingerprint signal.

[0095] The embodiment of the present invention also provides an ultrasonic fingerprint detection module, including the ultrasonic fingerprint detection sensor and an integrated circuit dedicated chip. The integrated circuit dedicated chip communicates with the ultrasonic fingerprint detection sensor and provides a signal for generating four timing control signals to the ultrasonic fingerprint detection sensor. When the ultrasonic fingerprint detection module is used in a corresponding electronic device, the integrated circuit dedicated chip in the ultrasonic fingerprint detection module communicates with the core processing chip of the electronic device. The integrated circuit dedicated chip receives the information from the core processing chip and controls the ultrasonic fingerprint detection sensor to detect and identify the fingerprint on the screen.

[0096] From the above, it can be seen that the ultrasonic fingerprint detection sensor of the embodiment of the present invention includes at least three MOS tubes or four or more MOS tubes in the ultrasonic fingerprint detection circuit 201a. In a specific embodiment, if the capacitor is also made of MOS tubes, the ultrasonic fingerprint detection circuit includes five MOS tubes. This ultrasonic fingerprint detection circuit is combined with the corresponding control timing, the corresponding ultrasonic sensor and the integrated circuit dedicated chip to complete the generation of ultrasonic signals and detect the ultrasonic fingerprint signal transmitted back through the finger on the screen. This ultrasonic fingerprint detection sensor is manufactured using TFT technology, which can produce large-array ultrasonic fingerprint detection sensors at a lower manufacturing cost.

[0097] It should be noted that, in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and to distinguish similar objects. There is no order of precedence between the two, and they cannot be understood as indicating or implying relative importance. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0098] Any numerical value cited herein includes all values ​​of lower and upper values ​​that increase by one unit from the lower limit to the upper limit, and there is at least a two-unit interval between any lower value and any higher value. For example, if the value of the quantity of a component or a process variable such as voltage is stated to be from 0 to 17, preferably from 0 to 15, the purpose is to illustrate that values ​​such as 0 to 14, 0.1 to 13, 1 to 12 are not explicitly listed in the specification. For values ​​less than 1, one unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1. These are merely examples that are intended to be clearly expressed, and it can be considered that all possible combinations of numerical values ​​listed between the lowest value and the highest value are clearly stated in the specification in a similar manner.

[0099] Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. "About" or "approximately" used with a range applies to both endpoints of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30", including at least the specified endpoints.

[0100] The above are only several embodiments of the present invention. Those skilled in the art may make various changes or modifications to the embodiments of the present invention based on the contents disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims

1. An ultrasonic fingerprint detection sensor, characterized in that: include: Glass substrate; An ultrasonic pixel array is provided on the glass substrate, and includes a plurality of ultrasonic pixel units; each of the ultrasonic pixel units includes an ultrasonic sensor and an ultrasonic fingerprint detection circuit, and the ultrasonic fingerprint detection circuit includes a capacitor and at least four MOS tubes: a first MOS tube, a second MOS tube, a third MOS tube, and a fourth MOS tube; the ultrasonic fingerprint detection circuit receives at least four corresponding timing control signals: a first drive signal, a bias signal, a second drive signal, and a row selection signal, and the four timing control signals are independent of each other; Wherein, the first MOS transistor is used as a source follower transistor, the gate of the first MOS transistor is connected to one end of the capacitor, the gate of the fourth MOS transistor receives the second drive signal, the gate of the third MOS transistor receives the first drive signal, and the source / drain of the third MOS transistor receives the bias signal; the source and drain of the third MOS transistor and the fourth MOS transistor are connected to form a common point, the common point is connected to the electrode corresponding to the ultrasonic sensor, and the gate of the second MOS transistor receives the row selection signal; In the receiving stage of the ultrasonic fingerprint detection circuit, at least the second driving signal is used to turn on the fourth MOS tube, so that the gate of the first MOS tube forms an electrical path with the common contact; in the interval in which the common contact and the gate of the first MOS tube form an electrical path, the first driving signal and the bias signal are used to control the turning on of the third MOS tube to raise the potential of the common contact; in the reading stage after the receiving stage, the row selection signal is used to turn on the second MOS tube to output the ultrasonic fingerprint signal stored in the gate of the first MOS tube.

2. The ultrasonic fingerprint detection sensor according to claim 1, characterized in that: A working cycle of the ultrasonic pixel unit also includes an excitation phase, the ultrasonic sensor receives an excitation signal, and the ultrasonic fingerprint detection circuit uses the first drive signal and the bias signal to control the third MOS tube to provide a steady-state DC potential for the common point.

3. The ultrasonic fingerprint detection sensor according to claim 1, characterized in that: In the reading phase, the second driving signal controls the fourth MOS transistor to be turned off.

4. The ultrasonic fingerprint detection sensor according to claim 1, characterized in that: In the receiving stage, the method further includes utilizing the second driving signal to control the fourth MOS transistor to be turned off, thereby blocking the electrical path between the common point and the gate of the first MOS transistor.

5. The ultrasonic fingerprint detection sensor as claimed in claim 4, characterized in that: In the receiving stage, the first driving signal has a first pulse signal with a first preset maintenance time, and the first pulse signal has a rising edge and a falling edge; The bias signal is a second pulse signal with a second preset holding time, the second pulse signal has a rising edge and a falling edge, and the bias signal has three-state potentials in the receiving phase: a low potential, a high potential, and a third-state potential.

6. The ultrasonic fingerprint detection sensor as claimed in claim 5, characterized in that: The first preset holding time is equal to the second preset holding time, and the rising edge and the falling edge of the first pulse signal and the second pulse signal coincide with each other.

7. The ultrasonic fingerprint detection sensor according to claim 5, characterized in that: The second preset holding time is greater than the first preset holding time; the rising edge of the second pulse signal is earlier than the rising edge of the first pulse signal, and the falling edge of the second pulse signal is later than the falling edge of the first pulse signal.

8. The ultrasonic fingerprint detection sensor according to claim 4, characterized in that: In the receiving stage, the bias signal is a stable preset potential, the first driving signal includes a first pulse signal, and the first pulse signal has a rising edge and a falling edge.

9. The ultrasonic fingerprint detection sensor according to claim 1, characterized in that: The ultrasonic fingerprint detection circuit also includes a reset phase. In the reset phase, the gate of the first MOS tube is reset to a reset signal using the drive signal and the bias signal.

10. The ultrasonic fingerprint detection sensor according to claim 9, characterized in that: In the reset phase, the second driving signal is used to control the fourth MOS transistor to be turned on, so that the common contact and the gate of the first MOS transistor form an electrical path.

11. The ultrasonic fingerprint detection sensor according to claim 9, characterized in that: The ultrasonic fingerprint detection circuit also includes a second reading phase, which uses a row selection signal to control the conduction of the second MOS tube and reads a reset signal of the gate of the first MOS tube in the reset phase.

12. The ultrasonic fingerprint detection sensor according to claim 1, characterized in that: The capacitor includes at least one of a PIP capacitor, a metal plate capacitor, a PMOS tube capacitor and an NMOS tube capacitor.

13. An ultrasonic fingerprint detection module, comprising: The ultrasonic fingerprint detection sensor as claimed in claim 1; The integrated circuit dedicated chip is electrically connected to the ultrasonic fingerprint detection sensor and is used to generate four timing control signals for the ultrasonic fingerprint detection sensor.

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