Fingerprint detection circuit, fingerprint detection device and method for manufacturing fingerprint detection circuit

Abstract

The present application provides a fingerprint detection circuit, a fingerprint detection device and a method for manufacturing a fingerprint detection circuit, wherein the fingerprint detection circuit comprises: a pixel unit, comprising a first conductive layer, and a second conductive layer and a third conductive layer located on the same side of the first conductive layer, a first capacitor is formed between the first conductive layer and the finger, a second capacitor is formed between the second conductive layer and the first conductive layer, and a third capacitor is formed between the third conductive layer and the first conductive layer, the second capacitor and the third capacitor are used for charge distribution so that the pixel unit outputs a capacitance signal associated with the first capacitor, the area of ​​the third conductive layer is K times the area of ​​the second conductive layer, and K is a preset value not equal to 1; and an integration unit, used to convert the capacitance signal into a voltage signal, and the voltage signal is used to determine the fingerprint image of the finger. The fingerprint detection circuit has better fingerprint detection performance.

Description

Technical Field

[0001] Embodiments of the present application relate to the field of touch control technology, and more specifically, to a fingerprint detection circuit, a fingerprint detection device, and a method for manufacturing a fingerprint detection circuit. Background Art

[0002] The capacitive fingerprint detection system extracts fingerprint information by detecting the changes in the capacitance signal corresponding to the peaks and valleys of the fingerprint. The fingerprint detection system includes an array composed of multiple fingerprint detection circuits, each of which uses a metal electrode plate to sense the fingerprint path of the finger. Specifically, the fingerprint detection circuit can convert the capacitance signal between the metal electrode plate and the finger into a voltage signal to extract and identify the fingerprint information based on the voltage signal. However, the capacitance between the metal electrode plate and the finger is very small. If there is a significant difference between the output signals of multiple fingerprint detection circuits, the output signal consistency of the entire fingerprint detection circuit array is poor, which will reduce the signal-to-noise ratio of fingerprint detection and affect the fingerprint detection performance. Summary of the invention

[0003] The embodiments of the present application provide a fingerprint detection circuit, a fingerprint detection device, and a method for manufacturing a fingerprint detection circuit, wherein the fingerprint detection circuit has better fingerprint detection performance.

[0004] In a first aspect, a fingerprint detection circuit is provided, comprising: a pixel unit, comprising a first conductive layer, and a second conductive layer and a third conductive layer located on the same side of the first conductive layer, wherein a first capacitor is formed between the first conductive layer and the finger, a second capacitor is formed between the second conductive layer and the first conductive layer, and a third capacitor is formed between the third conductive layer and the first conductive layer, the second capacitor and the third capacitor are used for charge distribution so that the pixel unit outputs a capacitance signal associated with the first capacitor, the area of ​​the third conductive layer is K times the area of ​​the second conductive layer, and K is a preset value not equal to 1; and an integration unit, used to convert the capacitance signal into a voltage signal, and the voltage signal is used to determine the fingerprint image of the finger.

[0005] In this technical solution, each fingerprint detection circuit includes a pixel unit and an integration unit, and the pixel unit includes a first conductive layer, a second conductive layer and a third conductive layer. When a finger contacts the first conductive layer, a first capacitor is formed between the finger and the first conductive layer. At this time, the second capacitor formed between the second conductive layer and the first conductive layer, and the third capacitor formed between the third conductive layer and the first conductive layer, are used to distribute charge during the fingerprint detection process, so that the pixel unit outputs a capacitance signal associated with the first capacitor. The integration unit converts the capacitance signal into a voltage signal, and the fingerprint image of the finger can be determined based on the voltage signals output by multiple fingerprint detection circuits. Since the area of ​​the third conductive layer is K times the area of ​​the second conductive layer, by reasonably setting K, the size relationship between the second capacitor and the third capacitor can be adjusted, so that the second capacitor and the third capacitor can reasonably distribute charge during the fingerprint detection process, thereby reducing the manufacturing differences of the conductive layers in different fingerprint detection circuits, and the impact on the consistency of the voltage signal output by the integration circuit.

[0006] In one possible implementation, the integration unit includes an amplifier, a first input terminal of the amplifier is connected to one end of the first conductive layer, an integrating capacitor is connected between the output terminal of the amplifier and the first input terminal, the other end of the first conductive layer is connected to a first power supply, a second input terminal of the amplifier is connected to a reference voltage, and the second conductive layer is connected to a second power supply.

[0007] In a possible implementation manner, K is determined based on at least one of a voltage of the first power supply, a voltage of the second power supply, and the reference voltage.

[0008] In a possible implementation, K = (V R +V1-V2) / (V1-V R ), V R is the reference voltage, V1 is the voltage of the first power supply, and V2 is the voltage of the second power supply.

[0009] In a possible implementation manner, the voltage of the first power supply is equal to the voltage of the second power supply; or the voltage of the first power supply is not equal to the voltage of the second power supply.

[0010] In a possible implementation manner, a reset switch is further connected between the output end of the amplifier and the first input end, and the reset switch is used to reset the voltage signal output by the amplifier.

[0011] In a possible implementation, the second conductive layer is connected to the second power supply through a first switch, the second conductive layer is grounded through a second switch, the first conductive layer is connected to the first power supply through a third switch, and a fourth switch is connected between the first conductive layer and the integration unit. In the first period of the fingerprint detection cycle, the first switch and the third switch are turned on, and the second switch and the fourth switch are turned off, so as to charge the first capacitor and the second capacitor through the first power supply; in the second period of the fingerprint detection cycle, the second switch and the fourth switch are turned on, and the first switch and the third switch are turned off, so as to discharge the first capacitor and the second capacitor to the integration unit.

[0012] In a possible implementation manner, a dielectric layer is provided between the second conductive layer and the first conductive layer, and between the third conductive layer and the first conductive layer, and the dielectric layer is polished.

[0013] In a possible implementation, the thickness of the dielectric layer is between 1.5 microns and 1.9 microns.

[0014] In a second aspect, a fingerprint detection device is provided, comprising: a fingerprint detection circuit array, comprising multiple fingerprint detection circuits in the first aspect or any possible implementation of the first aspect; and a processing unit, used to determine a fingerprint image based on a voltage signal output by the fingerprint detection circuit array.

[0015] In a third aspect, a method for manufacturing a fingerprint detection circuit is provided, which is used to manufacture the fingerprint detection circuit in the first aspect or any possible implementation of the first aspect, and the method includes: manufacturing a second conductive layer and a third conductive layer in each pixel unit on a substrate; manufacturing a dielectric layer on the second conductive layer and the third conductive layer; polishing the dielectric layer; and manufacturing a first conductive layer on the polished dielectric layer.

[0016] In this technical solution, each fingerprint detection circuit includes a pixel unit and an integration unit, and the pixel unit includes a first conductive layer, a second conductive layer and a third conductive layer, wherein a dielectric layer is provided between the first conductive layer and the second conductive layer, and between the first conductive layer and the third conductive layer. Since the distance between two conductive layers affects the capacitance formed between the two conductive layers, by polishing the dielectric layer between the two conductive layers to improve its flatness, the thickness difference of the conductive layers in different fingerprint detection circuits can be reduced, thereby reducing the manufacturing difference of the conductive layers in different fingerprint detection circuits, and the influence on the consistency of the voltage signal output by the integration circuit.

[0017] In a possible implementation manner, the thickness of the dielectric layer after polishing is between 1.5 micrometers and 1.9 micrometers.

[0018] In a possible implementation, the polishing process includes chemical mechanical polishing (CMP).

[0019] In a possible implementation, the manufacturing of the second conductive layer and the third conductive layer in each pixel unit on the substrate includes: depositing a first metal layer on the substrate; and etching the first metal layer to form the second conductive layer and the third conductive layer.

[0020] In a possible implementation, the manufacturing of the first conductive layer on the polished dielectric layer includes: depositing a second metal layer on the polished dielectric layer; and etching the second metal layer to form the first conductive layer.

[0021] In a possible implementation manner, the method further includes: manufacturing a passivation layer on the first conductive layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic block diagram of a fingerprint detection circuit according to an embodiment of the present application.

[0023] Figure 2 yes Figure 1 A schematic diagram of a possible implementation of a fingerprint detection circuit is shown.

[0024] Figure 3 It is a schematic diagram of the normalized result of the data output by the fingerprint detection circuit array.

[0025] Figure 4 It is a schematic diagram of the areas of the second conductive layer and the third conductive layer.

[0026] Figure 5 It is a schematic block diagram of a fingerprint detection device according to an embodiment of the present application.

[0027] Figure 6 is a schematic flow chart of a method for manufacturing a fingerprint detection circuit according to an embodiment of the present application.

[0028] Figure 7 yes Figure 6 The schematic diagram of the specific process of the method for manufacturing a fingerprint detection circuit is shown. DETAILED DESCRIPTION

[0029] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0030] The capacitive fingerprint detection system extracts fingerprint information by detecting the changes in the capacitance signal corresponding to the peaks and valleys of the fingerprint. The fingerprint detection system includes an array composed of multiple fingerprint detection circuits, each of which uses a metal electrode plate to sense the fingerprint path of the finger. Specifically, the fingerprint detection circuit can convert the capacitance signal between the metal electrode plate and the finger into a voltage signal to extract and identify the fingerprint information based on the voltage signal.

[0031] The focus is usually on the detection performance of a single fingerprint detection circuit, while ignoring the differences between multiple fingerprint detection circuits in a fingerprint detection circuit array. In fact, due to manufacturing deviations, there are inherent differences between different fingerprint detection circuits, which affects the signal to noise ratio (SNR) of the fingerprint detection system.

[0032] To this end, the present application provides a fingerprint detection circuit, a fingerprint detection device and a method for manufacturing a fingerprint detection circuit, which improve the fingerprint detection performance without increasing the difficulty of the manufacturing process, and do not increase additional costs while improving the fingerprint detection performance.

[0033] Figure 1 FIG. 1 is a schematic block diagram of a fingerprint detection circuit according to an embodiment of the present application. Figure 1 As shown, the fingerprint detection circuit 100 includes a pixel unit 110 and an integration unit 120 .

[0034] The pixel unit 110 includes a first conductive layer 111, and a second conductive layer 112 and a third conductive layer 113 located on the same side of the first conductive layer 222. A first capacitor C is formed between the first conductive layer 111 and the finger to be tested 200. F A second capacitor C1 is formed between the second conductive layer 112 and the first conductive layer 111, and a third capacitor C2 is formed between the third conductive layer 113 and the first conductive layer 111. The second capacitor C1 and the third capacitor C2 are used for charge distribution so that the pixel unit 110 outputs a charge that is equal to the first capacitor C F associated capacitance signal.

[0035] The integration unit 120 is used to convert the capacitance signal output by the pixel unit 110 into a voltage signal, and the voltage signal is used to determine the fingerprint image of the finger 200 .

[0036] Specifically, the fingerprint detection device includes a fingerprint detection circuit array composed of a plurality of fingerprint detection circuits 100, wherein each fingerprint detection circuit 100 includes a pixel unit 110 and an integration unit 120, and the pixel unit 110 includes a first conductive layer 111, a second conductive layer 112, and a third conductive layer 113. When the finger 200 contacts the first conductive layer 111, a first capacitor C is formed between the finger 200 and the first conductive layer 111. FAt this time, the second capacitor C1 formed by coupling between the second conductive layer 112 and the first conductive layer 111, and the third capacitor C2 formed by coupling between the third conductive layer 113 and the first conductive layer 111 are used to distribute the charge during the fingerprint detection process, so that the pixel unit 110 outputs the first capacitor C F The capacitance signal associated with the fingerprint image is converted into a voltage signal by the integration unit 120. Each pixel unit 220 corresponds to a pixel in the fingerprint image, and each fingerprint detection circuit 100 outputs a voltage signal for determining a pixel value of a pixel in the fingerprint image. Therefore, based on the voltage signals output by multiple fingerprint detection circuits 100, a fingerprint image of the finger 200 can be obtained.

[0037] Since the conductive layers of different fingerprint detection circuits 100 are different during the manufacturing process, the consistency between the voltage signals output by different fingerprint detection circuits 100 will be affected.

[0038] To this end, in the embodiment of the present application, the area of ​​the second conductive layer 113 and the area of ​​the third conductive layer are configured such that the area of ​​the third conductive layer 113 is K times the area of ​​the second conductive layer 112, or in other words, the area of ​​the second conductive layer 112 is 1 / K times the area of ​​the third conductive layer 113. Here, K is a preset value not equal to 1.

[0039] Generally, the size of the second capacitor and the size of the third capacitor have opposite effects on the voltage signal output by the integration circuit 120. When the area of ​​the third conductive layer 113 is K times the area of ​​the second conductive layer 112, by setting K reasonably, the size relationship between the second capacitor and the third capacitor can be adjusted so that the second capacitor and the third capacitor can reasonably distribute the charge during the fingerprint detection process, thereby reducing the manufacturing differences between the conductive layers in different fingerprint detection circuits 100 and the impact on the consistency of the voltage signal output by the integration circuit 120.

[0040] In one implementation, the integration unit 120 includes an amplifier 121, a first input terminal of the amplifier 121 is connected to one end of the first conductive layer 111, an integration capacitor Cint is connected between the output terminal and the first input terminal of the amplifier 121, the other end of the first conductive layer 111 is connected to a first power supply, a second input terminal of the amplifier is connected to a reference voltage, and the second conductive layer 112 is connected to a second power supply.

[0041] Based on the circuit structure in this implementation, the above K can be based on the voltage V of the first power supply. CC , the voltage of the second power supply V DD , and the reference voltage V R For example, K=(V R +V1-V2) / (V1-VR ), V R is the reference voltage, V1 is the voltage of the first power supply, and V2 is the voltage of the second power supply. The voltage V1 of the first power supply and the voltage V2 of the second power supply may be equal, or the voltage V1 of the first power supply and the voltage V2 of the second power supply may be unequal. R It is usually smaller than the voltage V1 of the first power supply and the voltage V2 of the second power supply.

[0042] The following, combined Figure 2 Provide detailed explanation.

[0043] like Figure 2 As shown, the pixel unit 110 includes a first conductive layer 111, a second conductive layer 112 and a third conductive layer 113. When performing fingerprint detection, a first capacitor C is formed between the finger and the first conductive layer 111. F . The first conductive layer 111 is located in the top metal layer (Top Metal) of the integrated circuit layout, and the second conductive layer 112 and the third conductive layer 113 are located in the bottom metal layer (Top-1 Metal) of the integrated circuit layout. The first conductive layer 111 and the second conductive layer 112 are coupled to form a second capacitor C1, and the first conductive layer 111 and the third conductive layer 113 are coupled to form a third capacitor C2. According to the principle of parallel plate capacitors, that is, C=ε×S / d, the size of the capacitor is related to the area of ​​the metal plate, the distance between the two metal plates, and the dielectric constant ε. There is a dielectric layer between the two metal plates. During the manufacturing process, the fluctuation of the thickness of the dielectric layer will cause the second capacitor C1 in each pixel unit 110 to be different, or the third capacitor C2 in each pixel unit 110 to be different, which makes the voltage signal V output by the integration unit 120 OUT For example, when the difference between the second capacitors C1 in the two pixel units 110 is 0.1 fF, the voltage signals V output by the corresponding two integration units 120 are OUT There will be a difference of nearly 7% between them, so the data (Rawdata) output by the entire fingerprint detection circuit array will have a large fluctuation, which is related to the first capacitor C F It has nothing to do with the error caused by the manufacturing process. OUT The fluctuation will reduce the signal-to-noise ratio of fingerprint detection. Here, the fluctuation degree of the data output by each fingerprint detection circuit in the fingerprint detection circuit array is called consistency. For example, the consistency can be characterized by the difference between the maximum value and the minimum value in the output data of each fingerprint detection circuit. The smaller the consistency, the smaller the output error and the better the fingerprint detection performance. Figure 3The normalized results of the data output by the three fingerprint detection circuit arrays A, B and C are shown, among which the fingerprint detection circuit array A has the smallest consistency and the best performance; the fingerprint detection circuit array C has the largest consistency and the worst performance; the performance of the fingerprint detection circuit array B is between the fingerprint detection circuit array A and the fingerprint detection circuit array C.

[0044] In practical applications, the first conductive layer 111 in the pixel unit 110 is usually covered with an insulating medium, such as a passivation layer and a packaging material ( Figure 2 The distances between the peaks and valleys of the fingerprint and the first conductive layer 111 are different, so the first capacitors C generated on different pixel units 110 are different. F Different, the first capacitor C F Converted into different voltage signals V OUT , voltage signal V OUT The information can be output to a back-end processing unit to determine whether the position of the first conductive layer 111 corresponds to a peak or a valley of the fingerprint.

[0045] In one implementation, Figure 2 As shown, the second conductive layer 112 is connected to the second power supply through the first switch K1, and the second conductive layer 112 is grounded through the second switch K2. The first conductive layer 111 is connected to the first power supply through the third switch K3, and a fourth switch K4 is connected between the first conductive layer 111 and the integration unit 120.

[0046] Each fingerprint detection cycle may include a first period and a second period. In the first period, the first switch K1 and the third switch K3 are turned on, and the second switch K2 and the fourth switch K4 are turned off, so that the first power supply to the first capacitor C F and the second capacitor C1 is charged; in the second period, the second switch K2 and the fourth switch K4 are turned on, the first switch K1 and the third switch K3 are turned off, and the first capacitor C F and the second capacitor C1 discharges to the integration unit 120, so that the first capacitor C F The charge of the second capacitor C1 is transferred to the integration unit 120. In addition, part of the charge is transferred to other circuits ( Figure 2 The size of the capacitor C is related to the circuit itself and is not related to the first capacitor C F It is irrelevant and can be recorded as X.

[0047] In order to increase the signal quantity output by the integration unit 120, generally N fingerprint detection cycles, that is, N coding times, are performed to accumulate the charge quantity transferred to the integration circuit 120. The voltage signal V output by the fingerprint detection circuit 100 is finally obtained. OUT for:

[0048] VOUT =V R +N×[(V R +V1-V2)×C1+(V R -V1)×C F +(V R –V1)×C2+X] / Cint(1).

[0049] Multiple fingerprint detection circuits 100 detect voltage signals V corresponding to different positions of the finger OUT The analog to digital converter (ADC) converts the voltage signal V OUT After data processing and analog-to-digital conversion, the results are saved in registers.

[0050] In one implementation, Figure 2 As shown, a reset switch K5 is further connected between the output terminal and the first input terminal of the amplifier 121, and the reset switch K5 is used to reset the voltage signal V output by the amplifier 121. OUT The first input terminal of the amplifier 121 may be an inverting input terminal or a non-inverting input terminal of the amplifier 121 , and correspondingly, the second input terminal of the amplifier 121 may be a non-inverting input terminal or an inverting input terminal of the amplifier 121 .

[0051] like Figure 2 As shown, in the fingerprint detection circuit 100, the voltage V1 of the first power supply, the voltage V2 of the second power supply, and the reference voltage V R , and the above X can be considered fixed. The integral capacitor Cint across the amplifier 121 is usually composed of a metal-insulator-metal (MIM) capacitor, which is basically not affected by the process. N is a fixed value. Only the second capacitor C1 and the third capacitor C2 are greatly affected by the manufacturing process, resulting in different voltage signals V output by the fingerprint detection circuit 100. OUT There are fluctuations between them.

[0052] Assuming K = C2 / C1, based on the above formula (1), the voltage signal V OUT It can be further expressed as: V OUT =V R +N×[(V R +V1-V2)×C1+(V R –V1)×C F +K×(V R -V1)×C1+X] / Cint(2).

[0053] Further simplifying formula (2), we get:

[0054] VOUT = -A × (KB) × C1 + C (3);

[0055] Where A = N × (V1-V R ) / Cint,B=(V R +V1-V2) / (V1-V R ), C=V R +N×[(V R -V1)×C F +X] / Cint.

[0056] A, B, and C are constants related to the circuit itself and can be considered fixed. The voltage signal V output by the fingerprint detection circuit 100 is OUT Associated with the second capacitor C1. Affected by the manufacturing process, the fluctuation of the second capacitor C1 in different fingerprint detection circuits 100 is recorded as △C1. From formula (3), it can be obtained that the voltage signal △V output by the fingerprint detection circuit 100 is OUT for:

[0057] △V OUT =-A×(KB)×△C1(4).

[0058] △V OUT K and ΔC1 are associated. ΔC1 is affected by the manufacturing process. Therefore, the consistency of the output signal of the fingerprint detection circuit array can be improved by adjusting K.

[0059] It can be seen from formula (4) that when KB = 0, that is, K = B, △V OUT Since K=C2 / C1, when C2 / C1=B, △V OUT Minimum.

[0060] The second capacitor C1 between the second conductive layer 112 and the first conductive layer 111, and the third capacitor C2 between the third conductive layer 113 and the first conductive layer 111 can be regarded as two parallel plate capacitors. The second conductive layer 112 and the third conductive layer 113 share the first conductive layer 111 as the upper plate. Figure 4 As shown, the size of the second capacitor C1 and the size of the third capacitor C2 are respectively associated with the areas S2 and S3 of their lower plates, so K=C2 / C1=S2 / S1.

[0061] It can be seen that two capacitors, namely the second capacitor C1 and the third capacitor C2, are used to distribute the charge. By adjusting the layout design of the second capacitor C1 and the third capacitor C2 on the conductive layer of the integrated circuit, the area S1 of the second capacitor C1 and the area S2 of the third capacitor C2 satisfy S2 / S1=B, that is, S2 / S1=(V R +V1-V2) / (V1-VR ), then △V OUT ≈0, thereby reducing the consistency difference of the output signals of different fingerprint detection circuits 100.

[0062] The voltage V1 and the voltage V2 may be equal voltages; or, the voltage V1 and the voltage V2 may be unequal voltages, for example, V1 is the power supply voltage V CC , V2 is the operating voltage V of the circuit DD , V CC Can be greater than V DD .

[0063] When V1=V2, the area S1 of the second capacitor C1 and the area S2 of the third capacitor C2 satisfy: S2 / S1=V R / (V1-V R ).

[0064] In addition, considering that the size of a capacitor is also related to the distance between the two plates of the capacitor, the distance between the two plates of the capacitor in different fingerprint detection circuits 100 should be made equal as much as possible.

[0065] For example, the dielectric layer between the second conductive layer 112 and the first conductive layer 111 and between the third conductive layer 113 and the first conductive layer 111 may be polished. By improving the flatness of the dielectric layer, the influence of the thickness deviation of the dielectric layer in different fingerprint detection circuits 100 during the manufacturing process on the consistency of the output signal is reduced.

[0066] For another example, the thickness of the dielectric layer may be appropriately increased to reduce the sensitivity of the thickness deviation, thereby reducing the influence of the thickness deviation of the dielectric layer on the consistency of the output signal, such as increasing the thickness of the dielectric layer from the existing 1 micron to between 1.5 microns and 1.9 microns.

[0067] The present application also provides a fingerprint detection device, such as Figure 5 As shown, the fingerprint detection device 400 includes: a fingerprint detection circuit array 410, including a plurality of the above-mentioned fingerprint detection circuits 100; and a processing unit 410, which is used to determine a fingerprint image according to a voltage signal output by the fingerprint detection circuit array 410. The fingerprint detection device 400 has a higher signal-to-noise ratio, so its fingerprint detection performance is better.

[0068] The present application also provides a method for manufacturing a fingerprint detection circuit, which is used to manufacture the above-mentioned fingerprint detection device 300. Figure 6 As shown, method 500 includes some or all of the following steps.

[0069] In step 510, the second conductive layer 112 and the third conductive layer 113 in each pixel unit are manufactured on a substrate.

[0070] In step 520 , a dielectric layer is formed on the second conductive layer 112 and the third conductive layer 113 .

[0071] In step 530, the dielectric layer is polished.

[0072] The polishing process may include, for example, chemical mechanical polishing (CMP).

[0073] In step 540, a first conductive layer 111 is formed on the polished dielectric layer.

[0074] Since the distance between the two conductive layers affects the capacitance between the two conductive layers, by polishing the dielectric layer between the two conductive layers to improve its flatness, the thickness difference of the conductive layers in different fingerprint detection circuits can be reduced, thereby reducing the manufacturing difference of the conductive layers in different fingerprint detection circuits and the impact on the consistency of the voltage signal output by the integration circuit.

[0075] The thickness of the dielectric layer after polishing may be, for example, between 1.5 microns and 1.9 microns. By increasing the thickness of the dielectric layer, the sensitivity of the thickness deviation is reduced, thereby reducing the influence of the thickness deviation of the dielectric layer on the consistency of the output signal.

[0076] In one implementation, step 520 includes: depositing a first metal layer on a substrate; etching on the first metal layer to form a second conductive layer 112 and a third conductive layer 113, for example, etching on the first metal layer to form the second conductive layer 112 and the third conductive layer 113 by photolithography, dry etching, or wet etching.

[0077] In one implementation, step 540 includes: depositing a second metal layer on the polished dielectric layer; etching the second metal layer to form a first conductive layer 111, for example, forming the first conductive layer 111 on the second metal layer by photolithography, dry etching, or wet etching.

[0078] In one implementation, the method 500 further includes: forming a passivation layer on the first conductive layer 111 .

[0079] Specifically, for example Figure 7In the process flow shown, in step (a), a first metal layer 610 is deposited on a substrate 600; in step (b), the first metal layer 610 is etched to form a second conductive layer 112 and a third conductive layer 113; in step (c), a dielectric layer 620 is made on the second conductive layer 112 and the third conductive layer 113; in step (d), the dielectric layer 620 is subjected to CMP treatment, and the thickness of the dielectric layer after CMP treatment can be between 1.5 microns and 1.9 microns; in step (e), a second metal layer 630 is deposited on the dielectric layer 620; in step (f), the first metal layer 610 is etched to form a first conductive layer 111; in step (g), a passivation layer 640 is deposited on the first conductive layer 111.

[0080] The present application also provides an electronic device, comprising the above-mentioned fingerprint detection device 400.

[0081] It should be noted that, under the premise of no conflict, the various embodiments described in this application and / or the technical features in each embodiment can be arbitrarily combined with each other, and the technical solution obtained after the combination should also fall within the protection scope of this application.

[0082] The systems, devices and methods disclosed in the embodiments of the present application may be implemented in other ways. For example, some features of the method embodiments described above may be ignored or not performed. The device embodiments described above are merely schematic, and the division of units is merely a logical function division. There may be other division methods in actual implementation, and multiple units or components may be combined or integrated into another system. In addition, the coupling between the units or the coupling between the components may be direct coupling or indirect coupling, and the coupling may include electrical, mechanical or other forms of connection.

[0083] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working process of the above-described devices and equipment and the technical effects produced can refer to the corresponding processes and technical effects in the aforementioned method embodiments, and will not be repeated here.

[0084] It should be understood that the specific examples in the embodiments of the present application are only to help those skilled in the art to better understand the embodiments of the present application, rather than to limit the scope of the embodiments of the present application. Those skilled in the art can make various improvements and modifications based on the above embodiments, and these improvements or modifications all fall within the scope of protection of the present application.

[0085] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A fingerprint detection circuit, characterized in that: include: A pixel unit, comprising a first conductive layer, and a second conductive layer and a third conductive layer located on the same side of the first conductive layer, wherein a first capacitor is formed between the first conductive layer and the finger, a second capacitor is formed between the second conductive layer and the first conductive layer, and a third capacitor is formed between the third conductive layer and the first conductive layer, the second capacitor and the third capacitor are used for charge distribution so that the pixel unit outputs a capacitance signal associated with the first capacitor, and an area of ​​the third conductive layer is K times the area of ​​the second conductive layer, where K is a preset value not equal to 1; and An integration unit, used to convert the capacitance signal into a voltage signal, wherein the voltage signal is used to determine the fingerprint image of the finger; The integration unit comprises an amplifier, a first input terminal of the amplifier is connected to one end of the first conductive layer, an integration capacitor is connected between the output terminal of the amplifier and the first input terminal, the other end of the first conductive layer is connected to a first power supply, a second input terminal of the amplifier is connected to a reference voltage, and the second conductive layer is connected to a second power supply; K is determined based on at least one of the voltage of the first power supply, the voltage of the second power supply, and the reference voltage, K=(V R +V1-V2) / (V1-V R ), V R is the reference voltage, V1 is the voltage of the first power supply, and V2 is the voltage of the second power supply.

2. The fingerprint detection circuit according to claim 1, characterized in that: The voltage of the first power supply is equal to the voltage of the second power supply; or, The voltage of the first power supply is not equal to the voltage of the second power supply.

3. The fingerprint detection circuit according to claim 1, characterized in that: A reset switch is further connected between the output end of the amplifier and the first input end, and the reset switch is used to reset the voltage signal output by the amplifier.

4. The fingerprint detection circuit according to claim 1, characterized in that: The second conductive layer is connected to the second power supply through a first switch and the second conductive layer is grounded through a second switch, the first conductive layer is connected to the first power supply through a third switch, and a fourth switch is connected between the first conductive layer and the integration unit; Wherein, in a first period of a fingerprint detection cycle, the first switch and the third switch are turned on, and the second switch and the fourth switch are turned off, so as to charge the first capacitor and the second capacitor through the first power supply; In a second period of the fingerprint detection cycle, the second switch and the fourth switch are turned on, and the first switch and the third switch are turned off, so that the first capacitor and the second capacitor discharge to the integration unit.

5. The fingerprint detection circuit according to claim 1, characterized in that: There is a dielectric layer between the second conductive layer and the first conductive layer, and between the third conductive layer and the first conductive layer, and the dielectric layer is polished.

6. The fingerprint detection circuit according to claim 5, characterized in that: The thickness of the dielectric layer is between 1.5 microns and 1.9 microns.

7. A fingerprint detection device, characterized in that: include: A fingerprint detection circuit array, comprising a plurality of fingerprint detection circuits as claimed in any one of claims 1 to 6; as well as, The processing unit is used to determine the fingerprint image according to the voltage signal output by the fingerprint detection circuit array.

8. A method for manufacturing a fingerprint detection circuit, characterized in that: For manufacturing a pixel unit in a fingerprint detection device as claimed in claim 7, the method comprises: Manufacturing the second conductive layer and the third conductive layer in the pixel unit on the substrate; forming a dielectric layer on the second conductive layer and the third conductive layer; performing a polishing process on the dielectric layer; A first conductive layer is formed on the polished dielectric layer.

9. The method according to claim 8, characterized in that The thickness of the dielectric layer after polishing is between 1.5 microns and 1.9 microns.

10. The method according to claim 8 or 9, characterized in that: The polishing process includes chemical mechanical polishing (CMP).

11. The method according to claim 8 or 9, characterized in that: The method of manufacturing the second conductive layer and the third conductive layer in each pixel unit on the substrate includes: depositing a first metal layer on the substrate; The second conductive layer and the third conductive layer are formed by etching on the first metal layer.

12. The method according to claim 8 or 9, characterized in that: The step of manufacturing a first conductive layer on the polished dielectric layer comprises: Depositing a second metal layer on the polished dielectric layer; The first conductive layer is formed by etching on the second metal layer.

13. The method according to claim 8 or 9, characterized in that: The method further comprises: A passivation layer is formed on the first conductive layer.

Images