Image sensor and electronic device

Abstract

An image sensor and an electronic device, the image sensor including a semiconductor substrate including a plurality of pixel regions, each pixel region being formed with a well region, at least two photoelectric conversion elements, at least two pass transistors, and a shared floating diffusion region, the well region spacing the photoelectric conversion elements, each transmission transistor is connected between each photoelectric conversion element and the floating diffusion region, each transmission transistor comprises a transmission channel for balancing potential barrier difference, and the transmission channel is connected between the photoelectric conversion element and the floating diffusion region; when the transmission transistor is in an open state, electrons in the photoelectric conversion element can be transmitted to the floating diffusion region through the transmission channel, and when the transmission transistor is in a closed state, the transmission channel prevents the electrons from passing through. The image sensor provided by the utility model can balance potential barrier difference and is beneficial to improving imaging quality.

Description

Technical Field

[0001] The present utility model relates to the technical field of image sensors, and particularly to an image sensor and an electronic device. Background Art

[0002] With the development of the computer industry and the communication industry, image sensors that acquire images and convert the acquired images into electrical signals have been used in various fields, such as digital cameras, video cameras, personal communication systems (PCS), gaming devices, security cameras, and medical micro cameras.

[0003] As image sensors become highly integrated and pixel sizes are miniaturized, a shared pixel structure is adopted in image sensors, that is, multiple photoelectric conversion elements share a floating diffusion region and other related pixel circuit transistors. Each photoelectric conversion element in the same pixel is separated by a well region, and the floating diffusion region is formed in the well region. When the well region and / or multiple photoelectric conversion elements are formed by ion doping, the distances between each photoelectric conversion element and the well region will vary due to process errors. For example, in the shared pixel structure, the distances between some photoelectric conversion elements and the well region are larger, while the distances between some other photoelectric conversion elements and the well region are smaller, resulting in inconsistent barriers for different photoelectric conversion elements to transfer electrons to the floating diffusion region, which will reduce the imaging quality. Summary of the Utility Model

[0004] In view of this, the present utility model provides an image sensor that can balance the barrier differences and is beneficial to improving the imaging quality.

[0005] The present utility model provides an image sensor, including a semiconductor substrate, the semiconductor substrate includes a plurality of pixel regions, each of the pixel regions is formed with a well region, at least two photoelectric conversion elements, at least two transfer transistors, and a shared floating diffusion region, wherein:

[0006] The well region separates each of the photoelectric conversion elements, each of the transfer transistors is connected between each of the photoelectric conversion elements and the floating diffusion region, each of the transfer transistors includes a transfer channel for balancing the barrier differences, and the transfer channel is connected between the photoelectric conversion element and the floating diffusion region; when the transfer transistor is in an open state, the transfer channel conducts to achieve electron transfer, and when the transfer transistor is in a closed state, the transfer channel blocks electron transfer.

[0007] Optionally, the transfer transistor further includes a gate structure, the transfer channel is correspondingly arranged with the gate structure, and the transfer channel is within the voltage control range of the gate structure.

[0008] Optionally, the transfer transistor further includes a first protective layer disposed between the gate structure and the transfer channel.

[0009] Optionally, a second protective layer is formed on the surface of each of the photoelectric conversion elements, wherein the second protective layer is connected to the first protective layer; and / or, the doping concentration of the second protective layer is the same as that of the first protective layer; and / or, the doping type of the second protective layer is the same as that of the first protective layer and different from the doping type of the photoelectric conversion element; and / or, the depth of the second protective layer is greater than or equal to the depth of the first protective layer.

[0010] Optionally, the transfer transistor further includes a depth limiting layer, the depth limiting layer is correspondingly arranged with the transfer channel, and the depth limiting layer is located between the transfer channel and the material layer of the semiconductor substrate.

[0011] Optionally, the doping concentration of the depth limiting layer is equal to the doping concentration of the well region; and / or, the doping concentration of the depth limiting layer is greater than the doping concentration of the semiconductor substrate; and / or, when the transfer transistor further includes a first protective layer, the doping type of the depth limiting layer is the same as that of the first protective layer and different from the doping type of the transfer channel; and / or, the depth of the depth limiting layer is greater than or equal to the depth of the floating diffusion region and less than the depth of the well region, and the depth of the well region is less than the depth of the photoelectric conversion element; and / or, the depth of the upper surface of the depth limiting layer is less than the depth of the floating diffusion region.

[0012] Optionally, the doping type of the transfer channel is the same as that of the photoelectric conversion element and the floating diffusion region; and / or, the doping concentration of the transfer channel is equal to the doping concentration of the photoelectric conversion element; and / or, the depth of the transfer channel is less than or equal to the depth of the floating diffusion region; and / or, when there is a second protective layer on the surface of the photoelectric conversion element, the depth of the transfer channel is greater than the depth of the second protective layer.

[0013] Optionally, one end of the transfer channel has a first overlapping region with the photoelectric conversion element, and the other end of the transfer channel has a second overlapping region with the floating diffusion region.

[0014] Optionally, when one end of the transfer channel has a first overlapping region with the photoelectric conversion element and the other end of the transfer channel has a second overlapping region with the floating diffusion region, along the electron transfer direction, the size of the second overlapping region is greater than the size of the first overlapping region.

[0015] Optionally, each of the pixel regions is formed with a reset transistor and a source follower transistor, and the source follower transistor is configured to output the electrical signal of the floating diffusion region; the reset transistor is configured to reset the floating diffusion region, or each of the pixel regions is further formed with a selection transistor, and the selection transistor is configured to selectively output the electrical signal output by the source follower transistor to the column line.

[0016] Optionally, the image sensor further includes at least one of the following:

[0017] The image sensor further includes a color filter array, the color filter array is disposed on the light incident side of the semiconductor substrate, and the color filter array includes a plurality of color filter units, and each of the color filter units is respectively disposed in one-to-one correspondence with each of the pixel regions or respectively disposed in one-to-one correspondence with each of the photoelectric conversion elements;

[0018] The image sensor further includes a lens array, the lens array is disposed on the light incident side of the color filter array, and the lens array includes a plurality of lens units, and each of the lens units is respectively disposed in one-to-one correspondence with each of the color filter units or respectively disposed in one-to-one correspondence with each of the photoelectric conversion elements.

[0019] Optionally, the floating diffusion region extends from the surface of the semiconductor substrate to the well region, and at least a part of the well region is correspondingly located on the electron transfer path from the photoelectric conversion element to the floating diffusion region.

[0020] Optionally, the well region at least includes a first region and a second region, the first region and the second region are arranged in a cross manner, and the first region and the second region divide the pixel region into a plurality of sub-pixel regions; wherein, each of the sub-pixel regions is formed with one of the photoelectric conversion elements, and / or, the photoelectric conversion elements corresponding to the plurality of sub-pixel regions in the same pixel region share one floating diffusion region.

[0021] Optionally, the first region and the second region divide the pixel region into four sub-pixel regions, and the floating diffusion region includes two floating diffusion nodes, and each of the floating diffusion nodes is respectively located between two adjacent sub-pixel regions to receive electrons from the corresponding photoelectric conversion element, or, when there is a source follower transistor, the source follower transistor is located between the two floating diffusion nodes.

[0022] Optionally, the doping type of the well region is the same as that of the semiconductor substrate and different from the doping type of the photoelectric conversion element; and / or, the depth of the well region is less than the depth of the photoelectric conversion element and greater than the depth of the floating diffusion region; and / or, the well regions within at least the same pixel region are integrally formed based on the same mask.

[0023] The present utility model also provides an electronic device, including the image sensor described in any one of the above.

[0024] The transfer transistor of the image sensor of the present utility model includes a transfer channel. When the transfer transistor is in an open state, the transfer channel can transfer electrons, which can balance the problem that there is a large barrier difference between the photoelectric conversion element and the floating diffusion region due to the different distances between the well region and each photoelectric conversion element. The electrons in the photoelectric conversion element can be transferred to the floating diffusion region through the transfer channel, reducing the barrier difference between the photoelectric conversion element corresponding to different photoelectric conversion elements and the floating diffusion region in the same pixel region, which is beneficial to improving the imaging quality; when the transfer transistor is in a closed state, the transfer channel blocks the passage of electrons. Description of the Drawings

[0025] Figure 1 is a top view structural schematic diagram of the image sensor of the present application.

[0026] Figure 2 is a cross-sectional structural schematic diagram of the image sensor of the present application.

[0027] Figure 3 is a pixel circuit structural schematic diagram of the image sensor of the present application.

[0028] Figure 4 is a schematic diagram of the pixel region of the image sensor of the present application separated based on the well region.

[0029] Figure 5 is a cross-sectional structural schematic diagram of another embodiment of the image sensor of the present application.

[0030] Figure 6 is a cross-sectional structural schematic diagram of yet another embodiment of the image sensor of the present application.

[0031] Figure 7 is a flowchart of an example of the manufacturing method of the image sensor of the present application. Detailed Embodiments

[0032] The following specific embodiments illustrate the implementation manners of the present application. Those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification.

[0033] In the following description, reference is made to the accompanying drawings, which describe several embodiments of the present application. It should be understood that other embodiments may also be used, and mechanical composition, structure, electrical, and operational changes may be made without departing from the spirit and scope of the present application. The following detailed description should not be considered restrictive. The terms used herein are only for describing specific embodiments and are not intended to limit the present application.

[0034] Although in some instances the terms first, second, etc. are used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another.

[0035] Furthermore, as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It should be further understood that the terms "comprises", "comprising" indicate the presence of the features, steps, operations, elements, components, items, kinds, and / or groups, but do not preclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, kinds, and / or groups. The term "or" and "and / or" as used herein are to be construed as inclusive, or meaning any one or any combination. Thus, "A, B, or C" or "A, B, and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B, and C". An exception to this definition occurs only when the combination of elements, functions, steps, or operations are inherently mutually exclusive in some manner.

[0036] As Figure 1 , Figure 2 and Figure 3 shown, the image sensor includes a semiconductor substrate 10, the semiconductor substrate 10 includes a plurality of pixel regions 101, each pixel region 101 is formed with a well region 121, at least two photoelectric conversion elements PD (such as PD1, PD2), at least two transfer transistors TX (such as TX1, TX2), and a shared floating diffusion region FD. The well region 121 separates the photoelectric conversion elements PD from each other. Each transfer transistor TX is connected between the corresponding photoelectric conversion element PD and the floating diffusion region FD. Each transfer transistor TX includes a transfer channel 122 for balancing the potential barrier difference, and the transfer channel 122 is connected between the photoelectric conversion element PD and the floating diffusion region FD. When the transfer transistor TX is in the on state, the transfer channel 122 between the photoelectric conversion element PD and the floating diffusion region FD is turned on to achieve electron transfer. When the transfer transistor TX is in the off state, the transfer channel 122 between the photoelectric conversion element PD and the floating diffusion region FD is cut off to prevent electron transfer. For example, in an actual operating state, when the transfer transistor TX is in the on state, the electrons in the photoelectric conversion element PD can be transferred to the floating diffusion region FD through the transfer channel 122. When the transfer transistor TX is in the off state, the transfer channel 122 prevents electrons from passing through.

[0037] The transfer transistor TX of the image sensor of the present application includes a transfer channel 122, which can transfer electrons when the transfer transistor TX is in the on state, and can balance the problem that there is a large barrier difference between the photoelectric conversion element PD and the floating diffusion region FD due to the different distances between the well region 121 and each photoelectric conversion element PD. The electrons in the photoelectric conversion element PD can be transferred to the floating diffusion region FD through the transfer channel 122, reducing the difference in the barriers between the photoelectric conversion element PD corresponding to different photoelectric conversion elements PD and the floating diffusion region FD, which is beneficial to improving the uniformity of electron transfer of each photoelectric conversion element PD in the same pixel region, and is beneficial to improving the problem of inconsistency in performance such as electron crosstalk (blooming) / full well capacity (FWC) between the light and each photoelectric conversion element PD, and is beneficial to improving the imaging quality; in addition, when the transfer transistor TX is in the off state, the transfer channel 122 blocks the passage of electrons.

[0038] Optionally, the doping type of the well region 121 is different from that of the photoelectric conversion element PD, and the isolation of the photoelectric conversion element PD can be achieved based on the well region 121 of different doping types. Further, the semiconductor substrate 10 and the well region 121 have the same doping type, and the doping concentration of the well region 121 is greater than that of the semiconductor substrate 10.

[0039] Optionally, the depth of the well region 121 is less than the depth of the photoelectric conversion element PD and greater than the depth of the floating diffusion region FD. Here, the depth refers to the position extending inward from the upper surface of the semiconductor substrate 10, and the size of the distance between this position and the upper surface of the semiconductor substrate is the size of the depth here.

[0040] Optionally, the transfer channel 122 is formed by doping a local region of the semiconductor substrate 10.

[0041] Optionally, the doping type of the transfer channel 122 is the same as that of the photoelectric conversion element PD and the floating diffusion region FD. For example, the semiconductor substrate 10 and the well region 121 are P-type doped, and the doping types of the transfer channel 122, the photoelectric conversion element PD, and the floating diffusion region FD are all N-type.

[0042] Optionally, the doping concentration of the transfer channel 122 is equal to the doping concentration of the photoelectric conversion element PD.

[0043] Optionally, the doping concentration of the transfer channel 122 is less than the doping concentration of the floating diffusion region FD, and the doping concentration of the photoelectric conversion element PD is less than the doping concentration of the floating diffusion region FD.

[0044] Optionally, the depth of the lower surface of the transfer channel 122 is less than or equal to the depth of the floating diffusion region FD.

[0045] Optionally, asFigure 2 As shown, the transfer transistor TX further includes a gate structure 123. The transfer channel 122 is correspondingly arranged with the gate structure 123, and the transfer channel 122 is within the voltage control range of the gate structure 123. Since the transfer channel 122 is within the voltage control range of the gate structure 123, the gate voltage can control the transfer channel 122 to be in an open state or a closed state. When the transfer transistor TX is in the open state, the gate voltage controls the transfer channel 122 to open, that is, electrons can pass through the transfer channel 122. When the transfer transistor TX is in the closed state, the gate voltage controls the transfer channel 122 to close, and the transfer channel 122 prevents electrons from passing through.

[0046] Optionally, the material of the gate structure 123 is polysilicon, but not limited thereto. Further, the material of the gate structure 123 is doped polysilicon, for example, P-type doped polysilicon. Furthermore, by adjusting the doping concentration and / or gradient, it is beneficial to realize the control of the gate structure 123 over the transfer channel 122.

[0047] Optionally, as Figure 2 shown, the transfer transistor TX further includes a first protective layer 124, which is disposed between the gate structure 123 and the transfer channel 122.

[0048] In this embodiment, the first protective layer 124 is formed by P-type doping a local area of the semiconductor substrate 10, and the first protective layer 124 separates the gate structure 123 from the transfer channel 122.

[0049] Optionally, as Figure 2 shown, a second protective layer 125 is formed on the surface of each photoelectric conversion element PD, and the second protective layer 125 is connected to the first protective layer 124. Optionally, the doping type of the second protective layer 125 is the same as that of the first protective layer 124 and different from the doping type of the photoelectric conversion element PD.

[0050] In this embodiment, the second protective layer 125 is formed by P-type doping a local area of the semiconductor substrate 10, and the second protective layer 125 is used to protect the photoelectric conversion element PD. Optionally, the depth of the lower surface of the second protective layer 125 is greater than or equal to the depth of the lower surface of the first protective layer 124. Among them, in one implementation, the depth of the lower surface of the second protective layer 125 is greater than the depth of the lower surface of the first protective layer 124, as Figure 6As shown, a transfer potential gradient is formed under the transfer transistor gate based on at least the photoelectric conversion element PD, the second protective layer 125, the transfer channel 122, the first protective layer 124, and the floating diffusion region FD, which is beneficial to the transfer during the operation of the image sensor. For example, when the transfer transistor is turned off, one side of the photoelectric conversion element PD is turned off first, and the corresponding side of the floating diffusion region FD is turned off later, which is beneficial to the transfer of electrons to the floating diffusion region FD and helps prevent the backflow of the transferred electrons.

[0051] Optionally, the doping concentration of the second protective layer 125 is equal to the doping concentration of the first protective layer 124.

[0052] In one implementation, the second protective layer 125 and the first protective layer 124 can be formed based on the same process, which simplifies the process, so that the concentration and depth of the second protective layer and the first protective layer are the same.

[0053] Optionally, when the second protective layer 125 exists on the surface of the photoelectric conversion element PD, the depth of the lower surface of the transfer channel 122 is greater than the depth of the lower surface of the second protective layer 125.

[0054] Optionally, when the second protective layer 125 exists on the surface of the photoelectric conversion element PD, the depth of the upper surface of the transfer channel 122 is less than or equal to the depth of the lower surface of the second protective layer 125.

[0055] Optionally, as Figure 2 shown, the transfer transistor TX further includes a depth limiting layer 126. The depth limiting layer 126 is correspondingly arranged with the transfer channel 122, and the transfer channel 122 is located between the first protective layer 124 and the depth limiting layer 126.

[0056] In this embodiment, the depth limiting layer 126 is formed by doping a local area of the semiconductor substrate 10. The depth limiting layer 126 is used to limit the ion doping depth of the transfer channel 122. For example, the doping type of the depth limiting layer 126 is different from that of the transfer channel 122. For example, the depth limiting layer 126 is P-type doped.

[0057] Optionally, the doping type of the depth limiting layer 126 is the same as that of the first protective layer 124 and different from that of the transfer channel 122. For example, the doping types of the depth limiting layer 126 and the first protective layer 124 are both P-type, and the doping type of the transfer channel 122 is N-type.

[0058] Optionally, the doping concentration of the depth limiting layer 126 is equal to the doping concentration of the well region 121.

[0059] Optionally, the doping concentration of the depth limiting layer 126 is greater than the doping concentration of the semiconductor substrate 10.

[0060] Optionally, the depth of the lower surface of the depth limiting layer 126 is greater than or equal to the depth of the floating diffusion region FD and less than the depth of the well region 121, and the depth of the well region 121 is less than the depth of the photoelectric conversion element PD.

[0061] Optionally, the depth of the upper surface of the depth limiting layer 126 is less than the depth of the floating diffusion region FD.

[0062] Optionally, as Figure 2 shown, one end of the transfer channel 122 has a first overlap region 122a with the photoelectric conversion element PD, and the other end of the transfer channel 122 has a second overlap region 122b with the floating diffusion region FD. Thus, it is beneficial to realize the regulation of the barrier difference under the control of the transfer gate based on the configuration of the two overlap regions.

[0063] Optionally, along the electron transfer direction, the size of the second overlap region 122b is larger than the size of the first overlap region 122a, which is beneficial to the electron transfer towards the floating diffusion region FD direction, and is beneficial to alleviating the barrier difference corresponding to different photoelectric conversion elements. In one implementation, as Figure 2 shown, it can be that in the horizontal direction of the corresponding figure, the length of the second overlap region 122b is greater than the length of the first overlap region 122a.

[0064] Optionally, as Figure 3 shown, each pixel region 101 is formed with a reset transistor RST and a source follower transistor SF. The source follower transistor SF is used to output the electrical signal of the floating diffusion region FD; the reset transistor RST is used to reset the floating diffusion region FD. In other implementations, each pixel region 101 further includes a gain control transistor DCG, which is arranged between the reset transistor RST and the floating diffusion region FD, and the capacitance size of the corresponding floating diffusion region FD is adjusted by turning on and off the gain control transistor DCG.

[0065] Optionally, as Figure 3 shown, a selection transistor RS is further formed in each pixel region 101. The selection transistor RS is used to selectively output the electrical signal output by the source follower transistor SF to the column line (Pixel out). In this embodiment, the semiconductor substrate 10 is doped, for example, by plasma implantation, so that the source and drain electrodes of the photoelectric conversion element PD, the floating diffusion region FD, the transfer transistor TX, the source follower transistor SF, the reset transistor RST, and the selection transistor RS are formed in the semiconductor substrate 10.

[0066] Optionally, the image sensor further includes a color filter array (not shown in the figure). The color filter array is disposed on the light incident side of the semiconductor substrate 10 and includes a plurality of color filter units, and each color filter unit is respectively arranged in one-to-one correspondence with each pixel region 101. In this embodiment, the plurality of color filter units include a plurality of red color filter units R, a plurality of green color filter units G, and a plurality of blue color filter units B. For example, an adjacent combination of one red color filter unit R, two green color filter units G, and one blue color filter unit B forms a color filter unit to constitute a multi-Bayer array arrangement. That is, in one pixel region, four photoelectric conversion elements PD correspond to the same color filter material, so that sixteen photoelectric conversion elements PD correspond to four pixel regions to form a Bayer structure. Of course, in other implementation manners, it may also be that one pixel region has color filter units of different colors, and different photoelectric conversion elements correspond to different color filter units, and one pixel region forms a Bayer array.

[0067] Optionally, the image sensor further includes a lens array (not shown in the figure). The lens array is disposed on the light incident side of the color filter array and includes a plurality of lens units, and each lens unit is respectively arranged in one-to-one correspondence with each color filter unit. Of course, in other implementation manners, it may also be that one pixel region has a plurality of different microlenses, and different photoelectric conversion elements correspond to different microlenses. For example, one pixel region forms four microlenses. In this embodiment, the lens unit is a convex lens for converging light.

[0068] Optionally, as Figure 1 and Figure 2 shown, the floating diffusion region FD extends from the surface of the semiconductor substrate 10 to the well region 121, and at least a part of the well region 121 is correspondingly located on the electron transfer path from the photoelectric conversion element PD to the floating diffusion region FD. Among them, the well region 121 may be formed in the semiconductor substrate prepared from the surface of the semiconductor substrate 10, and the floating diffusion region FD may be formed in the semiconductor substrate prepared from the surface of the semiconductor substrate 10. Further, the floating diffusion region FD is also formed at the position of the well region 121 at the same time. In one implementation manner, an edge region of the well region 121 is correspondingly located between the opposite edges of the photoelectric conversion element PD and the floating diffusion region FD, so that at least a part of the well region 121 is correspondingly located on the electron transfer path from the photoelectric conversion element PD to the floating diffusion region FD. Among them, a part of the well region 121 is formed on the electron transfer from the photoelectric conversion element PD to the floating diffusion region FD, and the potential distribution on the transfer path is formed based on the doping materials such as the well region 121 and the substrate.

[0069] Optionally, as Figure 1 and 4As shown, the well region 121 includes a first region and a second region. The first region and the second region are arranged in a cross manner. The first region and the second region divide the pixel region 101 into a plurality of sub-pixel regions, and each sub-pixel region is formed with a photoelectric conversion element PD. For example, the first region and the second region may adopt a vertical cross manner. Of course, in other examples, the well region 121 may further include a plurality of regions, so that the required sub-pixel regions are formed by separating each other among the plurality of different regions.

[0070] Optionally, the photoelectric conversion elements PD in one pixel region 101 share a floating diffusion region FD. Further, when the well region 121 divides the pixel region 101 into a plurality of sub-pixel regions, the photoelectric conversion elements PD corresponding to the plurality of sub-pixel regions share a floating diffusion region FD.

[0071] It should be noted that sharing a floating diffusion region FD here means that each photoelectric conversion element PD is electrically connected to a floating diffusion region FD area, and further electrically connected to a source follower transistor SF by this floating diffusion region FD area for electrical signal reading. Among them, the floating diffusion region FD may be an integral area or an area composed of two or more different floating diffusion nodes.

[0072] In one implementation, as Figure 1 and 4 shown, each pixel region 101 is formed with four photoelectric conversion elements PD1, PD2, PD3, PD4 and four transfer transistors TX1, TX2, TX3, TX4 respectively corresponding to the photoelectric conversion elements PD1, PD2, PD3, PD4.

[0073] Optionally, as Figure 1 shown, the first region and the second region divide the pixel region 101 into four sub-pixel regions. Further, the floating diffusion region FD includes two floating diffusion nodes, and each floating diffusion node is located between two adjacent sub-pixel regions to receive electrons of the corresponding photoelectric conversion element PD. That is, the four photoelectric conversion elements PD corresponding to the four sub-pixel regions are divided into two groups, and each group shares a floating diffusion node. Further, when there is a source follower transistor SF, the source follower transistor SF is located between the two floating diffusion nodes, and its gate is electrically connected to the two floating diffusion nodes. That is, in this example, the source follower transistor SF is formed at the center position of the four photoelectric conversion elements PD.

[0074] Optionally, the well regions 121 within at least the same pixel region 101 are integrally formed based on the same mask, and the well regions 121 of each pixel region 101 in the pixel array can be formed using the same set of masks. For example, in a single preparation process, ion implantation can be performed using a single patterned mask, which can simplify the process. Additionally, the photoelectric conversion elements within at least the same pixel region 101 are formed based on the same mask.

[0075] When the well regions 121 are formed corresponding to different photoelectric conversion elements PD in a pixel region 101, for example, when the well regions 121 are formed in at least two regions (such as the first region and the second region), the well regions 121 may be offset, and the distances between the well regions 121 and different photoelectric conversion elements PD are different. For the region between the photoelectric conversion element PD and the floating diffusion region FD (corresponding floating diffusion node), it is equivalent to the distribution of the well regions 121 being different, resulting in differences in the transmission barriers between the photoelectric conversion element PD and the floating diffusion region FD. Based on the transmission channel 122 of the present application, the transmission of electrons between the photoelectric conversion element PD and the floating diffusion region FD can be optimized, the barrier differences of the corresponding paths of different photoelectric conversion elements PD can be alleviated, the electrical consistency of different photoelectric conversion elements PD within the pixel region can be improved, and the electrical crosstalk and / or the consistency of the full well capacity between the pixels corresponding to different photoelectric conversion elements PD can be improved.

[0076] The present application also provides a method for manufacturing an image sensor, as Figure 7 shown, applicable to the image sensor described in any one of the above solutions. The manufacturing method includes the following steps:

[0077] Provide a semiconductor substrate, the semiconductor substrate including a plurality of pixel regions;

[0078] Prepare well regions and photoelectric conversion elements in the semiconductor substrate. Each pixel region is formed with a well region and at least two photoelectric conversion elements, and the well regions separate the photoelectric conversion elements from each other;

[0079] Prepare a transmission channel, a transmission transistor, and a floating diffusion region in each pixel region. Each pixel region is formed with at least two transmission transistors and a shared floating diffusion region, where:

[0080] Each transmission transistor is connected between each photoelectric conversion element and the floating diffusion region. Each transmission transistor includes the transmission channel for balancing the barrier differences; the transmission channel is connected between the photoelectric conversion element and the floating diffusion region; when the transmission transistor is in the on state, the electrons in the photoelectric conversion element can be transferred to the floating diffusion region through the transmission channel, and when the transmission transistor is in the off state, the transmission channel blocks the passage of electrons.

[0081] Among them, the order of the above steps can be adjusted according to the preparation of the existing image sensor, and it is not limited to the above. In addition, for the structures involved in the steps, please refer to the foregoing description and will not be elaborated here.

[0082] Optionally, the well regions in at least the same pixel region are integrally formed based on the same mask.

[0083] Optionally, when a second protective layer is formed on the surface of the photoelectric conversion element and the transfer transistor includes a first protective layer, the first protective layer and the second protective layer are formed based on the same process.

[0084] Optionally, the photoelectric conversion elements in at least the same pixel region are integrally formed based on the same mask.

[0085] This application also relates to an electronic device including the above image sensor. In this embodiment, the electronic device is, for example, a camera, a mobile phone, a vehicle-mounted device, a machine vision device, etc., but not limited thereto.

[0086] The above embodiments merely illustrate the principles and effects of this application, rather than limiting this application, and the structures or structural features involved can be arbitrarily combined and superimposed. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of this application. In addition, it should be noted that the doping concentration in this embodiment refers to the doping concentration of a certain region formed during the doping process, and the doping concentration of the finally formed region may be different due to the doped structure. In addition, for the upper and lower surfaces of the region formed by doping, it refers to the surfaces controlled during the doping process, which may vary due to actual diffusion, but this is all common knowledge in the art and can be known to those skilled in the art. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed in this application should still be covered by the claims of this application.

Claims

1. An image sensor, characterized in that: The invention comprises a semiconductor substrate, wherein the semiconductor substrate comprises a plurality of pixel regions, each of the pixel regions is formed with a well region, at least two photoelectric conversion elements, at least two transfer transistors and a shared floating diffusion region, wherein: The well region separates the photoelectric conversion elements, and the transfer transistors are connected between the photoelectric conversion elements and the floating diffusion region. Each transfer transistor includes a transfer channel that balances the potential barrier difference, and the transfer channel is connected between the photoelectric conversion element and the floating diffusion region. When the transfer transistor is in an on state, the transfer channel is turned on to achieve electron transfer, and when the transfer transistor is in a off state, the transfer channel prevents electron transfer.

2. The image sensor according to claim 1, wherein: The transmission transistor further includes a gate structure, the transmission channel is arranged corresponding to the gate structure, and the transmission channel is within a voltage control range of the gate structure.

3. The image sensor according to claim 2, wherein: The transmission transistor further includes a first protection layer disposed between the gate structure and the transmission channel.

4. The image sensor according to claim 3, wherein: A second protective layer is formed on the surface of each of the photoelectric conversion elements, wherein the second protective layer is connected to the first protective layer; and / or the second protective layer has the same doping concentration as the first protective layer; and / or the second protective layer has the same doping type as the first protective layer and is different from the doping type of the photoelectric conversion element; and / or the depth of the second protective layer is greater than or equal to the depth of the first protective layer.

5. The image sensor according to claim 2, wherein: The transmission transistor further includes a depth limiting layer, which is arranged corresponding to the transmission channel and is located between the transmission channel and the material layer of the semiconductor substrate.

6. The image sensor according to claim 5, characterized in that The doping concentration of the depth limiting layer is equal to the doping concentration of the well region; and / or, the doping concentration of the depth limiting layer is greater than the doping concentration of the semiconductor substrate; and / or, when the transfer transistor also includes a first protective layer, the depth limiting layer is the same as the first protective layer and has a doping type different from that of the transfer channel; and / or, the depth of the lower surface of the depth limiting layer is greater than or equal to the depth of the floating diffusion region and less than the depth of the well region, and the depth of the well region is less than the depth of the photoelectric conversion element; and / or, the depth of the upper surface of the depth limiting layer is less than the depth of the floating diffusion region.

7. The image sensor according to claim 1, wherein: The doping type of the transmission channel is the same as the doping type of the photoelectric conversion element and the floating diffusion region; and / or the doping concentration of the transmission channel is equal to the doping concentration of the photoelectric conversion element; and / or the depth of the transmission channel is less than or equal to the depth of the floating diffusion region; and / or, when a second protective layer exists on the surface of the photoelectric conversion element, the depth of the transmission channel is greater than the depth of the second protective layer.

8. The image sensor according to claim 1, wherein: One end of the transmission channel has a first overlapping region with the photoelectric conversion element, and the other end of the transmission channel has a second overlapping region with the floating diffusion region; or, when one end of the transmission channel has a first overlapping region with the photoelectric conversion element, and the other end of the transmission channel has a second overlapping region with the floating diffusion region, along the electron transmission direction, the size of the second overlapping region is greater than the size of the first overlapping region.

9. The image sensor according to claim 1, wherein: Each of the pixel regions is formed with a reset transistor and a source follower transistor, the source follower transistor is used to output the electrical signal of the floating diffusion region; the reset transistor is used to reset the floating diffusion region, or each of the pixel regions is further formed with a selection transistor, the selection transistor is used to select and output the electrical signal output by the source follower transistor to a column line; and / or, The image sensor further includes at least one of the following: The image sensor further includes a color filter array, which is arranged on the light incident side of the semiconductor substrate, and includes a plurality of color filter units, each of which is arranged in a one-to-one correspondence with each of the pixel regions or in a one-to-one correspondence with each of the photoelectric conversion elements; The image sensor also includes a lens array, which is arranged on the light incident side of the color filter array. The lens array includes a plurality of lens units, and each of the lens units is respectively arranged in a one-to-one correspondence with each of the color filter units or respectively arranged in a one-to-one correspondence with each of the photoelectric conversion elements.

10. The image sensor according to any one of claims 1 to 9, characterized in that: The floating diffusion region extends from the surface of the semiconductor substrate to the well region, and at least a portion of the well region is correspondingly located on an electron transfer path from the photoelectric conversion element to the floating diffusion region.

11. The image sensor according to claim 10, wherein: The well region includes at least a first region and a second region, the first region and the second region are cross-arranged, and the first region and the second region divide the pixel region into a plurality of sub-pixel regions; wherein each of the sub-pixel regions forms a photoelectric conversion element, and / or the photoelectric conversion elements corresponding to a plurality of the sub-pixel regions of the same pixel region share a floating diffusion region.

12. The image sensor according to claim 11, wherein: The first region and the second region divide the pixel region into four sub-pixel regions, and the floating diffusion region includes two floating diffusion nodes, each of which is located between two adjacent sub-pixel regions to receive electrons from the corresponding photoelectric conversion element, or, when a source follower transistor is present, the source follower transistor is located between the two floating diffusion nodes.

13. The image sensor according to claim 10, wherein: The doping type of the well region is the same as that of the semiconductor substrate and different from the doping type of the photoelectric conversion element; and / or the depth of the well region is less than the depth of the photoelectric conversion element and greater than the depth of the floating diffusion region; and / or, the well region within at least the same pixel area is formed integrally based on the same mask.

14. An electronic device, characterized in that: Comprising the image sensor as claimed in any one of claims 1-13.

Images