Photosensitive circuit structure and image sensor

Abstract

The application provides a photosensitive circuit structure and an image sensor. The photosensitive circuit structure comprises a photosensitive photodiode and a compensation unit. The compensation unit comprises a compensation photodiode and a compensation capacitor. A first electrode of the photosensitive photodiode and a first electrode of the compensation photodiode are electrically connected to a first voltage terminal. A second electrode of the compensation photodiode is electrically connected to a first electrode of the compensation capacitor. A second electrode of the photosensitive photodiode and a second electrode of the compensation capacitor are electrically connected to a signal output terminal. The compensation photodiode is used to generate a leakage current equal to that of the photosensitive photodiode. The leakage current of the compensation photodiode can neutralize the leakage current of the photosensitive photodiode, thereby eliminating the influence of the leakage current of the photosensitive photodiode on the performance of the photosensitive circuit structure. Therefore, the photosensitive circuit structure and the image sensor provided by the application can improve the performance of the photosensitive circuit structure and the image sensor.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a photosensitive circuit structure and an image sensor. Background Technology

[0002] Image sensors utilize the photoelectric conversion function of optoelectronic devices to convert a light image on a photosensitive surface into an electrical signal proportional to the light image. Image sensors are characterized by their small size, light weight, high integration, high resolution, and low power consumption, and are therefore widely used in fields such as medical detection, fingerprint recognition, and health monitoring.

[0003] In related technologies, the working process of an image sensor can generally be divided into reset, photoelectric conversion, and readout. An image sensor may include multiple pixel units, driving circuits, readout circuits, etc. The pixel circuit in the pixel unit converts the received light signal into an electrical signal, which is turned on by the timing control of the driving circuit. The signal is then processed into a digital signal by the readout circuit via the data line and transmitted to the host computer to form a digital image.

[0004] However, the performance of the aforementioned image sensors needs improvement. Summary of the Invention

[0005] In view of at least one of the above-mentioned technical problems, embodiments of this application provide a photosensitive circuit structure and an image sensor, which can improve the performance of the photosensitive circuit structure and the image sensor.

[0006] To achieve the above objectives, the embodiments of this application provide the following technical solutions:

[0007] A first aspect of this application provides a photosensitive circuit structure, including a photosensitive photodiode and a compensation unit. The compensation unit includes a compensation photodiode and a compensation capacitor. The first terminals of both the photosensitive photodiode and the compensation photodiode are electrically connected to a first voltage terminal. The second terminal of the compensation photodiode is electrically connected to the first terminal of the compensation capacitor. The second terminals of both the photosensitive photodiode and the compensation capacitor are electrically connected to a signal output terminal. The compensation photodiode is used to generate a leakage current equal to that of the photosensitive photodiode.

[0008] The photosensitive circuit structure provided in this application includes a photosensitive photodiode and a compensation unit. The compensation unit can neutralize the leakage current of the photosensitive photodiode, thereby improving the performance of the photosensitive circuit structure. The photosensitive photodiode and the compensation unit together form a photosensitive unit. The compensation unit can also reduce the difference in dark current among photosensitive units in different pixel units, thereby making the image obtained by the image sensor more uniform. The compensation unit can include a compensation photodiode and a compensation capacitor. The first terminals of both the photosensitive photodiode and the compensation photodiode are electrically connected to a first voltage terminal. The second terminal of the compensation photodiode is electrically connected to the first terminal of the compensation capacitor. Both the second terminals of the photosensitive photodiode and the compensation capacitor are electrically connected to a signal output terminal. The compensation photodiode generates a leakage current equal to that of the photosensitive photodiode. The leakage current of the compensation photodiode is transmitted to the first terminal of the compensation capacitor and generates a charge at the second terminal of the compensation capacitor. The charge at the second terminal of the compensation capacitor has the opposite polarity to the charge at the first terminal. The charge at the second terminal of the compensation capacitor can neutralize the leakage current of the photosensitive photodiode, thereby eliminating the influence of the leakage current of the photosensitive photodiode on the performance of the photosensitive circuit structure.

[0009] In one possible implementation, the photosensitive circuit structure further includes a control unit, the first terminal of which is electrically connected to the second electrode of the photosensitive photodiode and the second electrode of the compensation capacitor, the second terminal of which is electrically connected to the signal output terminal, and the control terminal of which is electrically connected to the control signal terminal.

[0010] In this way, the control unit can control the signal output of the photodiode.

[0011] In one possible implementation, the photosensitive circuit structure further includes a reset unit, with a first terminal electrically connected to a second voltage terminal, a second terminal electrically connected to the second electrode of the photosensitive photodiode and the second electrode of the compensation capacitor, and a control terminal electrically connected to a reset signal terminal.

[0012] In one possible implementation, the reset unit includes at least two reset transistors connected in series, the at least two reset transistors including a first reset transistor and a second reset transistor, the first terminal of the first reset transistor is electrically connected to a second voltage terminal and forms the first terminal of the reset unit, the second terminal of the first reset transistor is electrically connected to the first terminal of the second reset transistor, and the second terminal of the second reset transistor is electrically connected to the second terminal of the photosensitive photodiode and the second terminal of the compensation capacitor and forms the second terminal of the reset unit.

[0013] The control terminals of both the first and second reset transistors are electrically connected to the reset signal terminal, forming the control terminal of the reset unit.

[0014] In this way, the leakage current of the reset unit is relatively small.

[0015] In one possible implementation, the photosensitive circuit structure further includes an amplification unit, which includes an amplification transistor. The first terminal of the amplification transistor is electrically connected to a second voltage terminal, the second terminal of the amplification transistor is electrically connected to a first terminal of the control unit, and the control terminal of the amplification transistor is electrically connected to the second terminal of the photosensitive photodiode, the second terminal of the compensation capacitor, and the second terminal of the reset unit.

[0016] In this way, the photosensitive circuit structure is more sensitive to low light and can be applied to more scenarios.

[0017] In one possible implementation, the photosensitive circuit structure further includes an auxiliary transistor, the first electrode of which is electrically connected to the second electrode of the photosensitive photodiode and the second electrode of the compensation capacitor, the second electrode of which is electrically connected to the control electrode of the amplifying transistor, and the control electrode of which is electrically connected to the control signal terminal.

[0018] This reduces the leakage current between the photosensitive unit and the signal output terminal; it also reduces the leakage current between the photosensitive photodiode and the second voltage terminal, thereby further improving the performance of the photosensitive circuit structure.

[0019] In one possible implementation, the control unit includes at least two control transistors connected in series, including a first control transistor and a second control transistor. The first electrode of the first control transistor forms a first terminal of the control unit, and the second electrode of the first control transistor is electrically connected to the first electrode of the second control transistor. The second electrode of the second control transistor is electrically connected to a signal output terminal and forms a second terminal of the control unit. The control electrodes of both the first and second control transistors are electrically connected to a control signal terminal and form a control terminal of the control unit.

[0020] This results in a smaller leakage current in the control unit.

[0021] In one possible implementation, the photosensitive photodiode is located on the light-incident side of the compensating photodiode.

[0022] In this way, the photosensitive photodiode can block the light so that the light cannot shine on the compensation photodiode, thus putting the compensation photodiode in a light-blocking state.

[0023] In one possible implementation, the photosensitive circuit structure includes a substrate, with both a photosensitive photodiode and a compensation photodiode located on the substrate. The orthogonal projections of the photosensitive photodiode and the compensation photodiode on the substrate do not overlap, and a light-blocking element is provided on the light-incident side of the compensation photodiode.

[0024] In this way, the light-blocking component can block the light so that the light cannot shine on the compensation photodiode, thereby putting the compensation photodiode in a light-blocking state.

[0025] A second aspect of this application provides an image sensor, including the photosensitive circuit structure described in the first aspect.

[0026] The image sensor provided in this application embodiment may include a photosensitive circuit structure, which may include a photosensitive photodiode and a compensation unit. The compensation unit can be used to neutralize the leakage current of the photosensitive photodiode, thereby improving the performance of the photosensitive circuit structure. The photosensitive photodiode and the compensation unit together form a photosensitive unit. The compensation unit can also reduce the difference in dark current among photosensitive units in different pixel units, thereby making the image obtained by the image sensor more uniform. The compensation unit may include a compensation photodiode and a compensation capacitor. The first terminals of both the photosensitive photodiode and the compensation photodiode are electrically connected to a first voltage terminal. The second terminal of the compensation photodiode is electrically connected to the first terminal of the compensation capacitor. Both the second terminals of the photosensitive photodiode and the compensation capacitor are electrically connected to a signal output terminal. The compensation photodiode generates a leakage current equal to that of the photosensitive photodiode. The leakage current of the compensation photodiode is transmitted to the first terminal of the compensation capacitor and generates a charge at the second terminal of the compensation capacitor. The charge at the second terminal of the compensation capacitor is opposite in polarity to the charge at the first terminal of the compensation capacitor. The charge at the second terminal of the compensation capacitor can neutralize the leakage current of the photosensitive photodiode, thereby eliminating the influence of the leakage current of the photosensitive photodiode on the performance of the photosensitive circuit structure.

[0027] The structure of this application, as well as its other inventive objectives and beneficial effects, will become more apparent from the description of the preferred embodiments taken in conjunction with the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is an equivalent circuit diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0030] Figure 2 Another equivalent circuit diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0031] Figure 3 Another equivalent circuit diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0032] Figure 4 Another equivalent circuit diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0033] Figure 5 Another equivalent circuit diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0034] Figure 6 Another equivalent circuit diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0035] Figure 7 Another equivalent circuit diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0036] Figure 8 This is a timing diagram of the photosensitive circuit structure provided in the embodiments of this application;

[0037] Figure 9 This is a schematic diagram of the structure of the photosensitive photodiode and the compensation photodiode provided in the embodiments of this application;

[0038] Figure 10 This is another structural schematic diagram of the photosensitive photodiode and the compensation photodiode provided in the embodiments of this application.

[0039] Explanation of reference numerals in the attached figures:

[0040] 100: Photosensitive circuit structure; 110: Photosensitive unit;

[0041] 111: Compensation unit; 120: Control unit;

[0042] 130: Reset unit; 140: Amplification unit;

[0043] 150: Substrate; 161: First voltage terminal;

[0044] 162: Second voltage terminal; 163: Signal output terminal;

[0045] 164: Control signal terminal; 165: Reset signal terminal;

[0046] 170: Light-blocking component. Detailed Implementation

[0047] In related technologies, an image sensor may include multiple pixel units, driving circuits, readout circuits, etc. Each pixel unit includes a pixel circuit, which converts the received light signal into an electrical signal. This electrical signal is then turned on by the timing control of the driving circuit and processed into a digital signal by the readout circuit via a data line. Each pixel circuit may include a transistor and a photodiode, with the anode of the photodiode electrically connected to a reverse bias voltage.

[0048] However, photodiodes generate dark current under reverse bias voltage, which affects the performance of image sensors. Furthermore, due to process errors and equipment variations, the dark current of photodiodes in different pixel units varies significantly, resulting in poor image uniformity acquired by the image sensor.

[0049] Based on at least one of the aforementioned technical problems, embodiments of this application provide a photosensitive circuit structure and an image sensor. The photosensitive circuit structure may include a photosensitive photodiode and a compensation unit. The compensation unit can be used to neutralize the leakage current of the photosensitive photodiode, thereby improving the performance of the photosensitive circuit structure. The photosensitive photodiode and the compensation unit together form a photosensitive unit. The compensation unit can also reduce the difference in dark current among photosensitive units in different pixel units, thereby making the image obtained by the image sensor more uniform. The compensation unit may include a compensation photodiode and a compensation capacitor. The first terminals of both the photosensitive photodiode and the compensation photodiode are electrically connected to a first voltage terminal. The second terminal of the compensation photodiode is electrically connected to the first terminal of the compensation capacitor. The second terminals of both the photosensitive photodiode and the compensation capacitor are electrically connected to a signal output terminal. The compensation photodiode generates a leakage current equal to that of the photosensitive photodiode. The leakage current of the compensation photodiode is transmitted to the first terminal of the compensation capacitor and generates a charge at the second terminal of the compensation capacitor. The charge at the second terminal of the compensation capacitor is opposite in polarity to the charge at the first terminal of the compensation capacitor. The charge on the second electrode of the compensation capacitor can neutralize the leakage current of the photodiode, thereby eliminating the influence of the leakage current of the photodiode on the performance of the photosensitive circuit structure.

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0051] The following will combine Figures 1-10 The image sensor provided in the embodiments of this application will be described.

[0052] The image sensor provided in this application embodiment may include a plurality of pixel units arranged at intervals, for example, the pixel units may be arranged in an array. Each pixel unit may include a photosensitive circuit structure 100, which can be used to convert the received optical signal into an electrical signal.

[0053] The image sensor may also include a first voltage line, a second voltage line, a control signal line, a reset signal line, and a data line. Figure 3 Multiple photosensitive circuit structures 100 are electrically connected to the first voltage line, the second voltage line, the control signal line, the reset signal line, and the data line Data.

[0054] The photosensitive circuit structure 100 provided in the embodiments of this application will be described below.

[0055] See Figure 1 The photosensitive circuit structure 100 may include a photosensitive unit 110. A first terminal of the photosensitive unit 110 may be electrically connected to a first voltage terminal 161, and a second terminal of the photosensitive unit 110 may be electrically connected to a signal output terminal 163. The first voltage terminal 161 may be used to electrically connect to a first voltage line, thereby providing a first voltage to the photosensitive circuit structure 100. For example, the first voltage may be a reverse bias voltage Vbias. The signal output terminal 163 may be connected to a data line Data... Figure 3 The circuit is electrically connected and the output signal Vout is read through the reading circuit.

[0056] In this embodiment, one of the first and second terminals of the photosensitive unit 110 can be the input terminal of the photosensitive unit 110, and the other of the first and second terminals of the photosensitive unit 110 can be the output terminal of the photosensitive unit 110. The first and second terminals of other circuit units in this application embodiment can be similar to those of the photosensitive unit 110, and will not be described in detail here.

[0057] See also Figure 1 The photosensitive unit 110 may include a photosensitive photodiode D1 and a compensation unit 111. The first terminal D11 of the photosensitive photodiode D1 and the first terminal of the compensation unit 111 are both electrically connected to a first voltage terminal 161. The second terminal D12 of the photosensitive photodiode D1 and the second terminal of the compensation unit 111 are both electrically connected to a signal output terminal 163. The compensation unit 111 can be used to neutralize the leakage current of the photosensitive unit 110, thereby improving the performance of the photosensitive circuit structure 100. For example, in the absence of light, the photosensitive photodiode D1 will have a small reverse leakage current flowing through it when a reverse bias voltage Vbias is applied; this leakage current is also called dark current. Since the total current output by the photosensitive photodiode D1 is the sum of the leakage current generated when it is in operation and not exposed to light and the current generated when exposed to light, reducing the leakage current of the photosensitive photodiode D1 can improve the light sensitivity of the photosensitive circuit structure 100. In addition, the compensation unit 111 can also reduce the difference in leakage current among the photosensitive units 110 in different pixel units, thereby improving the uniformity of the image acquired by the image sensor.

[0058] In this embodiment, one of the first terminal D11 and the second terminal D12 of the photodiode D1 can be the positive terminal of the photodiode D1, and the other of the first terminal D11 and the second terminal D12 can be the negative terminal of the photodiode D1. Taking the first terminal D11 of the photodiode D1 as the positive terminal as an example, the first voltage terminal 161 can input a reverse bias voltage Vbias to the positive terminal of the photodiode D1. The first and second terminals of other photodiodes in this application embodiment are similar to those of the photodiode D1, and will not be described in detail here.

[0059] See also Figure 1 The compensation unit 111 may include a compensation photodiode D2 and a compensation capacitor C. The first terminals D11 of the photosensitive photodiode D1 and D21 of the compensation photodiode D2 are both electrically connected to the first voltage terminal 161. The second terminal D22 of the compensation photodiode D2 is electrically connected to the first terminal C1 of the compensation capacitor C. The second terminals D12 of the photosensitive photodiode D1 and C2 of the compensation capacitor C are both electrically connected to the signal output terminal 163. Under the action of the first voltage input to the first voltage terminal 161, the photosensitive photodiode D1 generates a first leakage current, and the compensation photodiode D2 generates a second leakage current. When the second leakage current is transmitted to the first terminal C1 of the compensation capacitor C, a first charge is generated on the first terminal C1 of the compensation capacitor C. This first charge causes a second charge to be generated on the second terminal C2 of the compensation capacitor C. The first charge and the second charge have opposite polarities. The second charge has an opposite polarity to the first leakage current, thereby neutralizing the first leakage current. Therefore, the compensation unit 111 can reduce the leakage current of the photosensitive unit 110, thereby improving the light sensitivity of the photosensitive circuit structure 100 and thus improving the performance of the photosensitive circuit structure 100. The first terminal C1 and the second terminal C2 of the compensation capacitor C are the two electrodes of the compensation capacitor C.

[0060] Furthermore, under illumination, the photosensitive photodiode D1 can be illuminated and generate photocurrent. The compensation photodiode D2 can always be in a light-blocking state (the light-blocking state will be described in the following embodiments), and therefore cannot be illuminated and cannot generate photocurrent. For example, the second leakage current generated by the compensation photodiode D2 can be less than or equal to the first leakage current generated by the photosensitive photodiode D1, thereby reducing the impact of the first leakage current on the performance of the photosensitive circuit structure 100. When the first leakage current equals the second leakage current, the first and second leakage currents can be completely neutralized, resulting in a better improvement in the performance of the photosensitive circuit structure 100.

[0061] The operation of the photosensitive circuit structure 100 can be as follows: when the photosensitive unit 110 is not illuminated, the leakage current generated by the photosensitive photodiode D1 and the compensation photodiode D2 in the photosensitive unit 110 neutralizes each other. When the photosensitive unit 110 is illuminated, the photosensitive photodiode D1 of the photosensitive unit 110 can convert the received optical signal into an electrical signal and transmit it to the signal output terminal 163.

[0062] See Figure 2 The photosensitive circuit structure 100 may further include a control unit 120. The first terminal of the control unit 120 may be electrically connected to the second terminal D12 of the photosensitive photodiode D1 and the second terminal C2 of the compensation capacitor C. The second terminal of the control unit 120 may be electrically connected to the signal output terminal 163. The control terminal of the control unit 120 is electrically connected to the control signal terminal 164. The control signal terminal 164 may be electrically connected to a control signal line to provide a control signal (Gate) to the photosensitive circuit structure 100.

[0063] The operation of the photosensitive circuit structure 100 can be as follows: When the photosensitive unit 110 is not illuminated, the leakage current generated by the photosensitive photodiode D1 and the compensation photodiode D2 in the photosensitive unit 110 neutralizes each other. When the photosensitive unit 110 is illuminated, the photosensitive photodiode D1 of the photosensitive unit 110 can convert the received light signal into an electrical signal. This electrical signal can be transmitted to the first terminal of the control unit 120, and the control signal Gate of the control signal terminal 164 is used to control the on / off state of the control unit 120. When the control unit 120 is turned on, this electrical signal can be transmitted to the second terminal of the control unit 120.

[0064] The control unit 120 may include at least one control transistor, and the number of control transistors that the control unit 120 may include is one, two, three, or four or more. See some examples. Figure 3 The control unit 120 may include a first control transistor T1 and a second control transistor T2 connected in series. The first terminal T11 of the first control transistor T1 may be electrically connected to the second terminal of the photosensitive unit 110, forming the first terminal of the control unit 120. The second terminal T12 of the first control transistor T1 is electrically connected to the first terminal T21 of the second control transistor T2. The second terminal T22 of the second control transistor T2 is electrically connected to the signal output terminal 163, forming the second terminal of the control unit 120. The control terminals of both the first control transistor T1 and the second control transistor T2 are electrically connected to the control signal terminal 164, forming the control terminals of the control unit 120. See also other examples. Figure 2The control unit 120 may consist only of a first control transistor T1. The first terminal T11 of the first control transistor T1 may be electrically connected to the second terminal of the photosensitive unit 110, forming the first terminal of the control unit 120. The second terminal T12 of the first control transistor T1 forms the second terminal of the control unit 120, and the control terminal of the first control transistor T1 forms the control terminal of the control unit 120. The principle has been explained and will not be repeated here.

[0065] By controlling the gate signal of the first control transistor T1 and the second control transistor T2, the first control transistor T1 and the second control transistor T2 can be turned on, thereby allowing the electrical signal transmitted to the control unit 120 to be transmitted from the first terminal of the control unit 120 to the second terminal of the control unit 120. When there are multiple control transistors, the multiple control transistors can be connected in series. The leakage current of multiple control transistors is smaller than that of a single control transistor, thereby improving the performance of the photosensitive circuit structure 100. The smaller the leakage current of the control unit 120, the less noise is doped in the electrical signal output by the control unit 120, thereby improving the signal-to-noise ratio of the output signal Vout by reducing the leakage current of the control unit 120. When the leakage current of the control unit 120 is reduced, the difference in leakage current of the control unit 120 in different pixel units can also be reduced, thereby improving the uniformity of the image obtained by the image sensor. When there are two control transistors, it is possible to ensure that the control unit 120 has a small leakage current with a smaller number of control transistors.

[0066] In this embodiment, one of the first and second terminals of the control transistor can be the drain of the control transistor, and the other of the first and second terminals can be the source of the control transistor. The control terminal of the control transistor can be the gate of the control transistor. The control transistor can be a P-type transistor or an N-type transistor. Different enable levels are provided depending on the transistor type. The enable level refers to the level that enables the transistor to conduct. For example, when the transistor is a P-type transistor, the enable level is low. When the transistor is an N-type transistor, the enable level is high. Other transistors in the embodiments of this application are similar to the control transistor and will not be described in detail.

[0067] See Figure 4 and Figure 5The photosensitive circuit structure 100 may further include a reset unit 130. The first terminal of the reset unit 130 is electrically connected to the second voltage terminal 162, and the second terminal of the reset unit 130 is electrically connected to the second electrode D12 of the photosensitive photodiode D1 and the second electrode C2 of the compensation capacitor C. The control terminal of the reset unit 130 is electrically connected to the reset signal terminal 165. The reset signal terminal 165 can be electrically connected to a reset signal line to provide a reset signal Reset to the photosensitive circuit structure 100. The second voltage terminal 162 can be electrically connected to a second voltage line to provide a second voltage to the photosensitive circuit structure 100. For example, the second voltage can be VDD.

[0068] The operation of the photosensitive circuit structure 100 can be as follows: When the photosensitive unit 110 is not illuminated, the leakage current generated by the photosensitive photodiode D1 and the compensation photodiode D2 in the photosensitive unit 110 neutralizes each other. The reset unit 130 is turned on to input an electrical signal to the photosensitive unit 110 via the second voltage terminal 162, and is turned off when the photosensitive unit 110 has an initial electrical signal. When the photosensitive unit 110 is illuminated, the photosensitive photodiode D1 of the photosensitive unit 110 can convert the received light signal into an electrical signal. This electrical signal is combined with the initial electrical signal to form a composite electrical signal, which is transmitted to the first terminal of the control unit 120. The control unit 120 is turned on to transmit the composite electrical signal to the signal output terminal 163.

[0069] For example, the reset unit 130 may include at least one reset transistor, and the number of reset transistors that the reset unit 130 may include is one, two, three, four or more. For example, the reset unit 130 may include a first reset transistor T3 and a second reset transistor T4 connected in series. The first terminal T31 of the first reset transistor T3 is electrically connected to the second voltage terminal 162 and forms the first terminal of the reset unit 130. The second terminal T32 of the first reset transistor T3 is electrically connected to the first terminal T41 of the second reset transistor T4, and the second terminal T42 of the second reset transistor T4 is electrically connected to the second terminal D12 of the photosensitive photodiode D1 and the second terminal C2 of the compensation capacitor C, forming the second terminal of the reset unit 130. The control terminals of the first reset transistor T3 and the second reset transistor T4 are both electrically connected to the reset signal terminal 165 and form the control terminal of the reset unit 130.

[0070] By controlling the reset signal Reset at the control terminals of the first reset transistor T3 and the second reset transistor T4, the first reset transistor T3 and the second reset transistor T4 can be turned on, thereby allowing VDD to be transmitted from the first terminal of the reset unit 130 to the second terminal of the reset unit 130. When there are multiple reset transistors, they can be connected in series. The leakage current of multiple reset transistors is smaller than that of a single reset transistor, which can reduce signal noise, ensure the authenticity and accuracy of composite electrical signals, and thus improve the performance of the photosensitive circuit structure 100. In addition, it can also reduce the difference in leakage current of the reset unit 130 in different pixel units, thereby improving the uniformity of the image obtained by the image sensor. When there are two reset transistors, it is possible to ensure that the reset unit 130 has a small leakage current with a smaller number of reset transistors.

[0071] See also Figure 4 and Figure 5 The photosensitive circuit structure 100 may further include an amplification unit 140. The first end of the amplification unit 140 is electrically connected to the second voltage terminal 162, the second end of the amplification unit 140 is electrically connected to the first end of the control unit 120, and the control terminal of the amplification unit 140 is electrically connected to the second end of the photosensitive unit 110 and the second end of the reset unit 130.

[0072] The operation of the photosensitive circuit structure 100 can be as follows: When the photosensitive unit 110 is not illuminated, the leakage current generated by the photosensitive photodiode D1 and the compensation photodiode D2 in the photosensitive unit 110 neutralizes each other. The reset unit 130 is turned on so that the second voltage terminal 162 inputs an electrical signal to the photosensitive unit 110, and is turned off when the photosensitive unit 110 has an initial electrical signal. When the photosensitive unit 110 is illuminated, the photosensitive photodiode D1 of the photosensitive unit 110 can convert the received light signal into an electrical signal. This electrical signal is combined with the initial electrical signal to form a composite electrical signal. The composite electrical signal is transmitted to the control terminal of the amplification unit 140 so that the second terminal of the amplification unit 140 can follow the composite electrical signal and output a corresponding following electrical signal. The following electrical signal can be transmitted to the first terminal of the control unit 120, and the control unit 120 is turned on to transmit the following electrical signal to the signal output terminal 163.

[0073] For example, the amplification unit 140 may include an amplification transistor T5. The first terminal T51 of the amplification transistor T5 is electrically connected to the second voltage terminal 162, forming the first terminal of the amplification unit 140. The second terminal T52 of the amplification transistor T5 is electrically connected to the first terminal of the control unit 120, forming the second terminal of the amplification unit 140. The control terminal of the amplification transistor T5 is electrically connected to the second terminal D12 of the photosensitive photodiode D1, the second terminal C2 of the compensation capacitor C, and the second terminal of the reset unit 130, forming the control terminal of the amplification unit 140.

[0074] In embodiments where the photosensitive circuit structure 100 does not include the amplification unit 140 and the reset unit 130, the structure of the photosensitive circuit structure 100 is relatively simple and easy to implement. In embodiments where the photosensitive circuit structure 100 includes the amplification unit 140 and the reset unit 130, the photosensitive circuit structure 100 is more sensitive to low light and can be applied to more scenarios. For example, it can be used for under-display fingerprint recognition.

[0075] See Figure 6 and Figure 7 The photosensitive circuit structure 100 may also include an auxiliary transistor T6. The first terminal T61 of the auxiliary transistor T6 is electrically connected to the second terminal D12 of the photosensitive photodiode D1 and the second terminal C2 of the compensation capacitor C. The second terminal T62 of the auxiliary transistor T6 is electrically connected to the control terminal of the amplifying transistor T5. The control terminal of the auxiliary transistor T6 is electrically connected to the control signal terminal 164.

[0076] On one hand, the auxiliary transistor T6 and the control unit 120 can jointly control the transmission of the electrical signal generated by the photosensitive unit 110 to the signal output terminal 163, which is equivalent to increasing the number of control transistors in the control unit 120, thereby reducing the leakage current between the photosensitive unit 110 and the signal output terminal 163. In this case, even if the control unit 120 only has one control transistor, the control unit 120, with the assistance of the auxiliary transistor T6, can still ensure a smaller leakage current between the photosensitive unit 110 and the signal output terminal 163, thereby improving the performance of the photosensitive circuit structure 100. On the other hand, the auxiliary transistor T6 is located between the reset unit 130 and the photosensitive unit 110. The auxiliary transistor T6 can reduce the leakage current between the photosensitive unit 110 and the second voltage terminal 162, thereby further improving the performance of the photosensitive circuit structure 100.

[0077] The following are Figure 6 The specific working process of the photosensitive circuit structure 100 in the middle is explained.

[0078] See Figure 6 and Figure 8First, during the initial power-on phase (t1), the first reset transistor T3 and the second reset transistor T4 in the reset unit 130 are turned on under the control of the reset signal Reset. The second terminal T42 of the second reset transistor T4 is electrically connected to the control terminal of the amplifying transistor T5, resetting the control terminal of the amplifying transistor T5. After a preset time, the control terminal of the amplifying transistor T5 acquires an initial voltage, and the reset signal Reset at the reset signal terminal 165 controls the first reset transistor T3 and the second reset transistor T4 to turn off.

[0079] Next is the photoelectric conversion stage (t2). Under illumination, the photosensitive unit 110 is exposed, and the photosensitive photodiode D1 generates a photocurrent and injects electrons into the negative side of the photosensitive photodiode D1, so that the voltage on the negative side of the photosensitive photodiode D1 continues to decrease.

[0080] Next is the electrical signal reading stage (t3). After the photosensitive unit 110 has been exposed for a period of time, the first control transistor T1 and the auxiliary transistor T6 are turned on under the control of the control signal Gate. The first terminal T11 of the first control transistor T1 receives the voltage signal from the second terminal T52 of the amplifying transistor T5. After passing through the second terminal T12 of the first control transistor T1, the voltage signal is output. The voltage signal is transmitted to the data line Data and then to the reading circuit. The reading circuit outputs the reading signal Read, thereby realizing the reading of the voltage signal.

[0081] Since the change in photocurrent of photosensitive unit 110 is positively correlated with the change in voltage on the negative side of photosensitive photodiode D1, and the change in voltage on the negative side of photosensitive photodiode D1 is positively correlated with light intensity, the greater the light intensity, the greater the change in voltage on the negative side of photosensitive photodiode D1, the smaller the voltage value on the negative side of photosensitive photodiode D1, the smaller the output voltage value of amplification unit 140, and the smaller the voltage signal output by control unit 120. Thus, the light intensity illuminating photosensitive photodiode D1 can be determined by detecting the magnitude of the voltage signal output by control unit 120.

[0082] During the operation of the aforementioned photodiode D1, a reverse bias stage also exists. This reverse bias stage can be set among multiple photoelectric conversion stages according to user needs to ensure the stable operation of the photodiode D1. Because electrons are injected into the negative side of the photodiode D1 for a long time, it is in a biased state, affecting the photoelectric conversion process. Therefore, reverse bias adjustment is required. Specifically, a reverse bias voltage Vbias can be provided to the positive side of the photodiode D1 through the reverse first voltage terminal 161 to eliminate the bias voltage in the photodiode D1 and maintain its efficient photoelectric conversion performance.

[0083] The following describes the compensation photodiode D2 provided in the embodiment of this application in a light-shielding state.

[0084] See Figure 9 and Figure 10 The photosensitive circuit structure 100 can be disposed on the substrate 150, which can provide a supporting foundation for other structural layers on the substrate 150. The material of the substrate 150 can be monocrystalline silicon, polycrystalline silicon, amorphous silicon, germanium silicide, silicon carbide, gallium nitride, etc. The substrate 150 can be a bulk silicon substrate or a silicon-on-insulator (SOI) substrate. The substrate 150 can also be formed of other organic or inorganic materials; for example, the material of the substrate 150 can include polyimide (PI) or polyethylene.

[0085] Both the photosensitive photodiode D1 and the compensation photodiode D2 can be located on the substrate 150. See some examples. Figure 9 The photosensitive photodiode D1 can be located on the light-incident side of the compensation photodiode D2. Under illumination, light can shine on the photosensitive photodiode D1, which can block the light, preventing it from reaching the compensation photodiode D2, thus placing the compensation photodiode D2 in a light-blocking state. For example, along the thickness direction of the substrate 150, the photosensitive photodiode D1 and the compensation photodiode D2 can be stacked on the substrate 150. The orthogonal projection of the photosensitive photodiode D1 onto the substrate 150 covers the orthogonal projection of the compensation photodiode D2 onto the substrate 150. See also other examples. Figure 10 The orthographic projections of photosensitive photodiode D1 and compensation photodiode D2 on substrate 150 do not overlap, and the distance between them can be greater than or equal to 0. For example, the film layers in photosensitive photodiode D1 and compensation photodiode D2 can be formed on the same layer and made of the same material, thereby simplifying the fabrication process of photosensitive photodiode D1 and compensation photodiode D2. A light-blocking element 170 can be provided on the light-incident side of compensation photodiode D2. Under illumination, light can strike the light-blocking element 170, which can block the light from reaching compensation photodiode D2, thus placing it in a light-shielded state. For example, the orthographic projection of the light-blocking element 170 on substrate 150 can cover the orthographic projection of compensation photodiode D2 on substrate 150.

[0086] "Same layer, same material" refers to a base membrane layer formed from the same material. After patterning and / or other processing of the base membrane layer, different parts of the base membrane layer are formed into various structural membrane layers. The processing techniques for the different structural membrane layers can be the same or different, and the different structural membrane layers can have the same or different thicknesses, and can be located on the same horizontal plane or different horizontal planes.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A photosensitive circuit structure, characterized in that, It includes a photosensitive photodiode and a compensation unit, wherein the compensation unit includes a compensation photodiode and a compensation capacitor. The first electrode of the photosensitive photodiode and the first electrode of the compensation photodiode are both electrically connected to the first voltage terminal, the second electrode of the compensation photodiode is electrically connected to the first electrode of the compensation capacitor, and the second electrode of the photosensitive photodiode and the second electrode of the compensation capacitor are both electrically connected to the signal output terminal. The compensation photodiode is used to generate a leakage current equal to that of the photosensitive photodiode; the charge on the second terminal of the compensation capacitor is opposite in polarity to the charge on the first terminal of the compensation capacitor, and the charge on the second terminal of the compensation capacitor neutralizes the leakage current of the photosensitive photodiode. It also includes an auxiliary transistor, the first electrode of which is electrically connected to the second electrode of the photosensitive photodiode and the second electrode of the compensation capacitor, the second electrode of which is electrically connected to the control electrode of the amplifying transistor, and the control electrode of which is electrically connected to the control signal terminal.

2. The photosensitive circuit structure according to claim 1, characterized in that, It also includes a control unit, the first terminal of which is electrically connected to the second electrode of the photosensitive photodiode and the second electrode of the compensation capacitor, the second terminal of which is electrically connected to the signal output terminal, and the control terminal of which is electrically connected to the control signal terminal.

3. The photosensitive circuit structure according to claim 2, characterized in that, It also includes a reset unit, the first end of which is electrically connected to the second voltage terminal, the second end of which is electrically connected to the second electrode of the photosensitive photodiode and the second electrode of the compensation capacitor, and the control terminal of the reset unit is electrically connected to the reset signal terminal.

4. The photosensitive circuit structure according to claim 3, characterized in that, The reset unit includes at least two reset transistors connected in series. The at least two reset transistors include a first reset transistor and a second reset transistor. The first terminal of the first reset transistor is electrically connected to the second voltage terminal and forms the first terminal of the reset unit. The second terminal of the first reset transistor is electrically connected to the first terminal of the second reset transistor. The second terminal of the second reset transistor is electrically connected to the second terminal of the photosensitive photodiode and the second terminal of the compensation capacitor and forms the second terminal of the reset unit. The control terminals of the first reset transistor and the second reset transistor are both electrically connected to the reset signal terminal, forming the control terminal of the reset unit.

5. The photosensitive circuit structure according to claim 4, characterized in that, It also includes an amplification unit, which includes an amplification transistor. The first terminal of the amplification transistor is electrically connected to the second voltage terminal, the second terminal of the amplification transistor is electrically connected to the first terminal of the control unit, and the control terminal of the amplification transistor is electrically connected to the second terminal of the photosensitive photodiode, the second terminal of the compensation capacitor, and the second terminal of the reset unit.

6. The photosensitive circuit structure according to any one of claims 2-5, characterized in that, The control unit includes at least two control transistors connected in series. The at least two control transistors include a first control transistor and a second control transistor. The first terminal of the first control transistor forms a first terminal of the control unit. The second terminal of the first control transistor is electrically connected to the first terminal of the second control transistor. The second terminal of the second control transistor is electrically connected to the signal output terminal and forms a second terminal of the control unit. The control terminals of the first control transistor and the second control transistor are both electrically connected to the control signal terminal and form a control terminal of the control unit.

7. The photosensitive circuit structure according to any one of claims 1-5, characterized in that, The photosensitive photodiode is located on the light-incident side of the compensating photodiode.

8. The photosensitive circuit structure according to any one of claims 1-5, characterized in that, The device includes a substrate, and both the photosensitive photodiode and the compensation photodiode are located on the substrate. The orthogonal projections of the photosensitive photodiode and the compensation photodiode on the substrate do not overlap. A light-blocking element is provided on the light-incident side of the compensation photodiode.

9. An image sensor, characterized in that, Includes the photosensitive circuit structure described in any one of claims 1-8.

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