Image sensor

Abstract

The utility model provides an image sensor, which comprises a semiconductor substrate, a first isolation structure is formed in the semiconductor substrate, the first isolation structure divides the semiconductor substrate into a plurality of pixel areas, and each pixel area is provided with a plurality of photoelectric conversion elements and at least one conduction part connected with at least two photoelectric conversion elements. Electrons generated by the connected photoelectric conversion elements can move to other photoelectric conversion elements through the conduction parts, and each pixel area further comprises an isolation area which separates the photoelectric conversion elements. The image sensor provided by the utility model is better in photosensitive effect and higher in sensitivity.

Description

Technical Field

[0001] The utility model relates to the technical field of image sensing, in particular to an image sensor. Background Art

[0002] With the development of computer industry and 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, camcorders, personal communication systems (PCS), game devices, security cameras, and medical miniature cameras.

[0003] As image sensors become highly integrated and pixel sizes are miniaturized, a shared pixel structure is used in image sensors, that is, multiple photoelectric conversion elements share one pixel. The electrons between the photoelectric conversion elements in the same pixel cannot flow to each other. It is possible that some photoelectric conversion elements in the same pixel produce insufficient electrons, while other photoelectric conversion elements are in a full well state (FWC), which may cause signal crosstalk between pixels and affect the linearity of the combined signal of the shared pixel unit, which will affect the image quality. Utility Model Content

[0004] In view of this, the utility model provides an image sensor with better photosensitivity and higher sensitivity.

[0005] An image sensor, the image sensor comprising a semiconductor substrate, a first isolation structure formed in the semiconductor substrate, the first isolation structure dividing the semiconductor substrate into a plurality of pixel regions, each of the pixel regions forming a plurality of photoelectric conversion elements and at least one conductive portion connecting at least two of the photoelectric conversion elements, the electrons generated by the connected photoelectric conversion elements can move to other photoelectric conversion elements through the conductive portion, and each of the pixel regions further comprising an isolation region separating the photoelectric conversion elements.

[0006] In an embodiment of the present invention, the isolation region is formed with a second isolation structure, the second isolation structure separates the photoelectric conversion elements, and the conductive portion is formed in the isolation region.

[0007] In an embodiment of the utility model, the above-mentioned isolation region includes a connecting portion and a plurality of isolation portions connected to the connecting portion, each of the isolation portions is arranged between two adjacent photoelectric conversion elements, and a plurality of the photoelectric conversion elements are arranged at intervals from each other around the circumference of the connecting portion; the connecting portion serves as the conductive portion, or at least one of the conductive portions is embedded in the connecting portion and the isolation portion, and the conductive portion connects each of the photoelectric conversion elements.

[0008] In an embodiment of the present invention, the conductive portion connects the photoelectric conversion elements in the pixel region.

[0009] In an embodiment of the present invention, the conductive portion is located in the middle of the pixel region, and a plurality of the photoelectric conversion elements are arranged at intervals around the conductive portion in a circumferential direction.

[0010] In an embodiment of the present invention, the conductive portion comprises a plurality of conductive sections spaced apart from each other, at least one conductive section is connected between two adjacent photoelectric conversion elements, and electron transfer is achieved between two adjacent photoelectric conversion elements through the conductive section.

[0011] In an embodiment of the present invention, each pixel region is formed with at least two conducting portions.

[0012] In an embodiment of the present invention, the semiconductor substrate comprises a first surface and a second surface which are arranged opposite to each other, and a distance is provided between the conducting portion and at least one of the first surface and the second surface.

[0013] In an embodiment of the present invention, the conductive portion comprises a first end surface and a second end surface which are arranged opposite to each other, the first end surface is coplanar with the first surface, and the second end surface is coplanar with the second surface.

[0014] In an embodiment of the utility model, the above-mentioned pixel area is formed with multiple transfer transistors and a shared floating diffusion area, each of the transfer transistors is respectively connected to each of the photoelectric conversion elements, the floating diffusion area is connected to each of the transfer transistors, and each of the transfer transistors is used to transfer the charge in each of the photoelectric conversion elements to the floating diffusion area.

[0015] In an embodiment of the utility model, each pixel region is formed with a reset transistor and a source follower transistor, the source follower transistor is used to output an electrical signal of the floating diffusion region; the reset transistor is used to at least reset the floating diffusion region;

[0016] Alternatively, a selection transistor is further formed in each pixel region, and the selection transistor is used to select and output the electrical signal output by the source follower transistor to a column line;

[0017] Alternatively, when a source follower transistor is formed, the source follower transistor is arranged in the middle of the pixel area, the plurality of photoelectric conversion elements are located on the peripheral side of the source follower transistor, and the floating diffusion area includes at least two sub-floating diffusion nodes, and the sub-floating diffusion nodes are connected to at least two of the photoelectric conversion elements based on the corresponding transfer transistor.

[0018] In an embodiment of the present invention, the potential barrier between adjacent photoelectric conversion elements connected by the conductive portion is greater than the potential barrier between the photoelectric conversion element and the floating diffusion region, and the potential barrier between the photoelectric conversion element and the floating diffusion region is greater than the potential barrier of the conductive portion.

[0019] In an embodiment of the present invention, the image sensor further comprises a color filter array, which is disposed on the light incident side of the semiconductor substrate. The color filter array comprises a plurality of color filter units, and each of the color filter units is disposed in one-to-one correspondence with each of the pixel regions.

[0020] In an embodiment of the present invention, the image sensor further comprises a lens array, wherein the lens array is arranged on the light incident side of the color filter array, and the lens array comprises a plurality of lens units, wherein each of the lens units is arranged in one-to-one correspondence with each of the color filter units.

[0021] A conducting part is connected between at least two photoelectric conversion elements of the image sensor of the present invention, and the connected photoelectric conversion elements can move electrons through the conducting part. For example, when the full well capacity of a photoelectric conversion element is exceeded, the conducting part can provide an electron movement path for excess electrons to flow to other photoelectric conversion elements. Therefore, the electron energy generated by the light received in the pixel area is not affected by the spatial limitations of each photoelectric conversion element, and the electrons can be accumulated in each photoelectric conversion element. The image sensor of the present application has a better photosensitivity and a higher sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the top view structure of the image sensor of the present application.

[0023] Figure 2 It is a schematic diagram of the pixel circuit structure of the image sensor of the present application.

[0024] Figure 3 It is a schematic diagram of a partial cross-sectional structure of the image sensor of the present application along the third direction.

[0025] Figure 4 is a partial cross-sectional view of the image sensor according to the first embodiment of the present application along a direction parallel to the first surface.

[0026] Figure 5 4 is a partial cross-sectional view of the image sensor according to the second embodiment of the present application along a direction parallel to the first surface.

[0027] Figure 6 4 is a partial cross-sectional view of an image sensor according to a third embodiment of the present application along a direction parallel to the first surface.

[0028] Figure 7a 4 is a partial cross-sectional view of the image sensor according to the fourth embodiment of the present application along the third direction.

[0029] Figure 7b 4 is a partial cross-sectional view of the image sensor according to the fourth embodiment of the present application along a direction parallel to the first surface.

[0030] Figures 8 to 10 It is a flowchart of a method for manufacturing an image sensor according to the fifth embodiment of the present application.

[0031] Figures 11 to 13 It is a flowchart of a method for manufacturing an image sensor according to the sixth embodiment of the present application.

[0032] Figures 14 to 16 It is a flowchart of a method for manufacturing an image sensor according to the seventh embodiment of the present application. DETAILED DESCRIPTION

[0033] The following is an explanation of the implementation of the present application by means of specific embodiments. People familiar with the art can easily understand other advantages and effects of the present application from the contents disclosed in this specification.

[0034] 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, structural, 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, and the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application.

[0035] Although the terms first, second, etc. are used herein to describe various elements in some instances, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element.

[0036] Furthermore, as used in this article, the singular forms "one", "an" and "the" are intended to include plural forms as well, unless there is an indication to the contrary in the context. It should be further understood that the terms "comprise", "include" indicate the presence of features, steps, operations, elements, components, projects, kinds, and / or groups, but do not exclude the presence, occurrence or addition of one or more other features, steps, operations, elements, components, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "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". Only when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way, will there be an exception to this definition.

[0037] Figure 1 is a schematic diagram of a top view structure of an image sensor of the present application, Figure 2is a schematic diagram of the pixel circuit structure of the image sensor of the present application, Figure 3 is a schematic diagram of a partial cross-sectional structure of the image sensor of the present application along the third direction, such as Figure 1 , Figure 2 and Figure 3 As shown, the image sensor includes a semiconductor substrate 10, a first isolation structure 11 is formed in the semiconductor substrate 10, and the first isolation structure 11 separates the semiconductor substrate 10 into a plurality of pixel regions 101, each pixel region 101 is formed with a plurality of photoelectric conversion elements PD (such as PD1, PD2, PD3, PD4) and at least one conductive portion 12 connecting at least two photoelectric conversion elements PD, and the electrons generated by each connected photoelectric conversion element PD can move to other photoelectric conversion elements PD through the conductive portion 12, and each pixel region 101 also includes an isolation region 1011, and the isolation region 1011 separates each photoelectric conversion element PD. In this embodiment, the semiconductor substrate 10 includes a first surface 111 and a second surface 112 that are parallel and oppositely arranged; a first direction X, a second direction Y, and a third direction Z that are perpendicular to each other are defined, and the first direction X and the second direction Y are parallel to the first surface 111.

[0038] Specifically, the semiconductor substrate 10 may be a structure composed of a single material layer, including but not limited to a silicon substrate, and its material may be single crystal silicon, single crystal germanium, polycrystalline silicon, amorphous silicon, or a silicon germanium compound, etc. Of course, the semiconductor substrate 10 may also be silicon on insulator SOI, etc. In addition, the semiconductor substrate 10 may also have an N-type doped or P-type doped region to meet actual needs.

[0039] The semiconductor substrate 10 serves as the base of the image sensor, and may also be a multi-layer structure, such as including a semiconductor substrate and an epitaxial layer formed on the surface of the semiconductor substrate. In this case, the epitaxial layer serves as a device functional layer to realize the preparation of the image sensor device. In addition, in other embodiments, the semiconductor substrate 10 may be any structure used to prepare the image sensor functional area in the field of image sensors, and the semiconductor substrate 10 may be used to prepare the photosensitive element of the CMOS image sensor, each transistor, and perform interconnection wiring.

[0040] In one example, the device functional layer may be a part of the semiconductor substrate 10, for example, it may be a P-type epitaxial layer (EPI) formed on a semiconductor substrate (such as a silicon substrate), and the epitaxial layer may be directly formed by an epitaxial process, or may be formed by other methods of existing processes. In this case, the semiconductor substrate and the epitaxial layer constitute the semiconductor substrate 10, and the epitaxial layer serves as the device functional layer. In one implementation, each functional region (including semiconductor devices) in the image sensor is prepared in the device functional layer. In other examples, the semiconductor substrate 10 as a whole may be considered to be a device functional layer of the first doping type, in which case the functional region in the image sensor may be prepared in the semiconductor substrate 10. Of course, if necessary, the structure required for the image sensor may also be prepared in the semiconductor substrate or other material layers. A back-illuminated image sensor may be prepared based on the semiconductor substrate and the device functional layer.

[0041] Optionally, the first isolation structure 11 extends from the second surface 112 of the semiconductor substrate 10 to the first surface 111 along the third direction Z. The first isolation structure 11 may be a doped region formed by first ion doping, such as a P-type doped region. Of course, it may also include a combination of a doped region formed by first ion doping and other isolation structures, such as a combination of a doped region formed by first ion doping from the second surface 112 and a back deep trench isolation structure BDT I formed from the first surface 111. Of course, other structures for dividing pixel regions in the prior art may also be used as the first isolation structure 11.

[0042] The image sensor of the utility model forms a conductive part between at least two photoelectric conversion elements, and the conductive part can provide an electron movement path for electrons to flow to other photoelectric conversion elements. The linearity of the combined signal of each photoelectric conversion element in the pixel area can be improved by controlling the potential barrier between the photoelectric conversion element and the floating diffusion area to be greater than the potential barrier of the conductive part; the image sensor of the present application has a conductive part 12 connected between at least two photoelectric conversion elements PD, and the connected photoelectric conversion elements PD can move electrons through the conductive part 12. For example, when the full well capacity (FWC) of a certain photoelectric conversion element PD is exceeded, the conductive part 12 can provide an electron movement path for excess electrons to flow to other photoelectric conversion elements PD. Therefore, the electron energy generated by the light received by the pixel area 101 is not affected by the spatial limitation of each photoelectric conversion element PD, and the electrons can be accumulated in each photoelectric conversion element PD. The image sensor of the present application has a better photosensitivity and a higher sensitivity. In addition, when signals are merged between different photoelectric conversion elements PD in the entire pixel area 101, the method of the present application can improve the linearity of the merged signal and improve the image quality.

[0043] Optionally, Figure 4is a schematic diagram of a partial cross-sectional structure of the image sensor of the first embodiment of the present application along a direction parallel to the first surface, such as Figure 4 and further see Figure 3 As shown, the isolation region 1011 is formed with a second isolation structure 13, the second isolation structure 13 separates the photoelectric conversion elements PD, and the conductive portion 12 is formed in the isolation region 1011. In this embodiment, the conductive portion 12 includes a plurality of conductive sections 124 spaced apart from each other, at least one conductive section 124 is embedded in the second isolation structure 13, and the conductive section 124 is connected between two adjacent photoelectric conversion elements PD, and electron transfer is achieved between the two adjacent photoelectric conversion elements PD through the conductive section 124; Figure 4 In the example shown, the central area of ​​the isolation region 1011 is not provided with the conductive portion 12 , that is, the central area of ​​the pixel region is not provided with the conductive portion 12 .

[0044] Optionally, the second isolation structure 13 extends from the second surface 112 of the semiconductor substrate 10 to the first surface 111 along the third direction Z; the peripheral side of the second isolation structure 13 is connected to the first isolation structure 11. The second isolation structure 13 may be an isolation structure formed by doping the second surface 112 of the semiconductor substrate during the front manufacturing process, such as a P-type isolation region; optionally, the material of the second isolation structure 13 may be the same as that of the first isolation structure 11. In the actual process, a deep trench isolation BDT I may also be prepared corresponding to the second isolation structure 13 during the back manufacturing process from the first surface 111 of the semiconductor substrate. In this case, it can be considered that the two together constitute the isolation inside the pixel area, which does not affect the implementation of the utility model.

[0045] Optionally, there is a spacing between the conductive portion 12 and at least one of the first surface 111 and the second surface 112. Preferably, there is a distance between the conductive portion 12 and both the first surface 111 and the second surface 112, that is, the conductive portion 12 is located between the first surface 111 and the second surface 112. The spacing is beneficial to the transmission control design. In other embodiments, the conductive portion 12 includes a first end face 121 and a second end face 122 that are arranged opposite to each other, the first end face 121 is coplanar with the first surface 111, and the second end face 122 is coplanar with the second surface 112.

[0046] In a preferred embodiment, the formation of the conductive portion 12 can be achieved by controlling the range of ion implantation during the process of forming the second isolation structure 13 by ion implantation, so that the area of ​​the semiconductor substrate 10 implanted with ions forms the second isolation structure 13, and the area not implanted with ions forms the conductive portion 12, that is, the impurities of the conductive portion 12 are the same as the impurities of the area of ​​the semiconductor substrate 10 that is not ion-doped. This process for forming the conductive portion 12 can reduce the ion doping steps and can reduce production costs. The semiconductor substrate 10 can be a P-type epitaxial layer, and the implanted ions forming the second isolation structure 13 can be P-type doped ions. The concentrations of the two can be controlled to be different to achieve the function of the present application. Of course, other examples can also use N epitaxial layer substrates.

[0047] In another preferred embodiment, the conductive portion 12 may be formed by performing ion implantation (such as P-type implantation) to form an initial formation region of the isolation structure, and then performing another ion doping (such as an N-type doping layer formed by N-type ion doping) in a local area of ​​the initial formation region of the isolation structure to form the conductive portion 12.

[0048] In an optional example, the concentration of N-type ion doping of the finally formed N-type ion-doped conductive portion 12 may be the same as the concentration of N-type ion doping of the connected photoelectric conversion element PD. In another optional example, the concentration of P-type ion doping of the finally formed P-type ion-doped conductive portion 12 is less than the doping concentration of the P-type isolation of the isolated connected photoelectric conversion element PD inside the corresponding pixel region.

[0049] Alternatively, if Figure 2 As shown, each pixel region 101 is formed with a plurality of transfer transistors TX (such as TX1, TX2, TX3, TX4) and a shared floating diffusion region FD, each transfer transistor TX is respectively connected to each photoelectric conversion element PD, the floating diffusion region FD is connected to each transfer transistor TX, and each transfer transistor TX is used to transfer the charge in each photoelectric conversion element PD to the floating diffusion region FD. In this embodiment, it can be similarly understood that each photoelectric conversion element PD can respectively constitute the source region of the corresponding transfer transistor TX, and the floating diffusion region FD can constitute the common drain region of each transfer transistor TX.

[0050] Optionally, 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 an electrical signal of the floating diffusion region FD; the reset transistor RST is used to reset at least the floating diffusion region FD; when the reset transistor RST is reset and turned on, the power supply voltage supplied to the source region of the reset transistor RST can be transmitted to the floating diffusion region FD, and thus, the floating diffusion region FD can be reset. In this embodiment, the floating diffusion region FD can be connected to the source region of the reset transistor RST and the gate of the source follower transistor SF.

[0051] Optionally, the source follower transistor SF can be used as a source follower buffer amplifier and can amplify the potential change of the floating diffusion region FD. Optionally, a selection transistor RS is also formed in each pixel area 101, and the selection transistor RS is used to select and output the electrical signal output by the source follower transistor SF to the column line. In this embodiment, the source region of the source follower transistor SF and the drain region of the selection transistor RS can be shared with each other, and the output voltage Vout can be provided from the source region of the selection transistor RS.

[0052] Optionally, the source follower transistor SF is arranged in the middle of the pixel region 101, and the plurality of photoelectric conversion elements PD are arranged around the source follower transistor SF, and the floating diffusion region includes at least two sub-floating diffusion nodes, and the sub-floating diffusion nodes are connected to at least two of the photoelectric conversion elements based on the corresponding transfer transistor. Optionally, the source follower transistor SF is arranged in the middle of the pixel region 101, and the plurality of photoelectric conversion elements PD are arranged around the source follower transistor SF.

[0053] Optionally, the floating diffusion region FD is arranged adjacent to the source follower transistor SF. Further, the floating diffusion region FD includes two sub-floating diffusion nodes, which are respectively arranged on both sides of the source follower transistor SF, wherein each sub-floating diffusion node can be electrically connected through an interconnection line and further electrically connected to the gate of the source follower transistor SF; since the source follower transistor SF is arranged in the middle of the pixel area 101, the source follower transistor SF is closer to the floating diffusion region FD, and therefore the parasitic capacitance is small.

[0054] Optionally, the potential barrier of the isolation structure between adjacent photoelectric conversion elements PD connected by the conductive part 12 is greater than the potential barrier between the photoelectric conversion element PD and the floating diffusion area FD, and the potential barrier between the photoelectric conversion element PD and the floating diffusion area FD is greater than the potential barrier of the conductive part 12. Among them, the potential barrier between the photoelectric conversion element PD and the floating diffusion area FD is greater than the potential barrier of the conductive part 12, so that the signal does not flow to FD in the non-transmission stage, which can improve the linearity of the combined signal of each photoelectric conversion element in the pixel area; the size relationship of the above-mentioned potential barrier can be formed by doping control, so that it is beneficial to control the transmission while satisfying the operation of each stage of the image sensor, and prevent the generation of image tailing l ag, and the electrons generated in the photoelectric conversion element PD preferentially move between different photoelectric conversion elements through the conductive part 12 in the exposure stage, and further, can be moved to the floating diffusion area FD through the transmission transistor in the signal transmission stage.

[0055] Alternatively, if Figure 3As shown, the image sensor further includes a color filter array 14, which is disposed on the light incident side of the semiconductor substrate 10, that is, disposed on the first surface 111 of the semiconductor substrate 10, and the color filter array 14 includes a plurality of color filter units 141, each of which is disposed one-to-one with each pixel region 101, that is, each color filter unit 141 covers a plurality of photoelectric conversion elements PD of each pixel region 101, and the plurality of photoelectric conversion elements PD of each pixel region 101 are used to photoelectrically convert light of the same color. In this embodiment, the color filter unit 141 includes a red color filter unit, a green color filter unit, and a blue color filter unit, wherein one red color filter unit, two green color filter units, and one blue color filter unit are arranged in a 2×2 two-dimensional array to form a color filter group, that is, four color filter units 141 are combined to form a color filter group, and the plurality of color filter groups can be arranged in a matrix form along a plurality of row lines and a plurality of column lines. The image sensor can work in a signal merging mode, that is, the signals of the photoelectric conversion elements of the same pixel area and the color filters sharing the same color are combined for use. Of course, the merging mode can be selected according to actual conditions, and the signals of the photoelectric conversion elements of a pixel area can be merged or partially merged. In addition, the image sensor can also work in a high-resolution mode with a single output.

[0056] Alternatively, if Figure 3 As shown, the image sensor also includes a lens array 15, which is arranged on the light incident side of the color filter array 14. The lens array 15 includes a plurality of lens units 151, and each lens unit 151 is arranged one-to-one with each color filter unit 141, that is, each lens unit 151 covers a plurality of photoelectric conversion elements PD of each pixel area 101, and each lens unit 151 is used to collect light incident on the plurality of photoelectric conversion elements PD of each pixel area 101.

[0057] Alternatively, if Figure 3 As shown, the image sensor also includes a first planar layer 16 and a second planar layer 17. The first planar layer 16 is disposed on the first surface 111 of the semiconductor substrate 10, the color filter array 14 is disposed on the first planar layer 16, the second planar layer 17 is disposed on the color filter array 14, and the lens array 15 is disposed on the second planar layer 17.

[0058] Optionally, the image sensor further includes an interconnection layer disposed on the second surface 112, and the interconnection layer is used to connect various devices such as the transmission transistor TX, the floating diffusion region FD, the reset transistor RST, the source follower transistor SF, the selection transistor RS, etc., to serve as an electrical signal transmission path between the devices.

[0059] Optionally, the image sensor further includes a pixel array and a circuit for controlling the pixel array, the circuit for controlling the pixel array including a column driver, a row driver, a timing controller and a readout circuit. The image sensor can operate according to a control command received from an image processor, and can convert light transmitted from an external object into an electrical signal and output the electrical signal to the image processor. The image sensor of the present application can be a complementary metal oxide semiconductor (CMOS) image sensor.

[0060] Second embodiment

[0061] Figure 5 is a schematic diagram of a partial cross-sectional structure of an image sensor according to a second embodiment of the present application along a line parallel to the first surface, such as Figure 5 As shown, the image sensor of this embodiment has substantially the same structure and function as the image sensor of the above-mentioned embodiment, except that the structure of the conductive portion 12 is different.

[0062] Specifically, Figure 5 As shown, the conductive portion 12 is arranged in the middle of the pixel area 101, and a plurality of photoelectric conversion elements PD are arranged at intervals around the circumference of the conductive portion 12, and the conductive portion 12 is connected to at least two photoelectric conversion elements PD. The figure shows a schematic diagram of the conductive portion 12 being connected to each photoelectric conversion element in the pixel area. Among them, the coverage area of ​​the top view when the conductive portion 12 is connected to the connected photoelectric conversion element can be designed according to the actual pixel requirements, and the electrons can be realized to flow based on the conductive portion, or the conductive portion can be in line contact with each photoelectric conversion element along the Z direction.

[0063] Please refer to the above for the structure and function of the image sensor, which will not be repeated here.

[0064] Third embodiment

[0065] Figure 6 is a schematic diagram of a partial cross-sectional structure of an image sensor according to a third embodiment of the present application along a line parallel to the first surface, such as Figure 6 As shown, the image sensor of this embodiment has substantially the same structure and function as the image sensor of the above-mentioned embodiment, and the difference lies in the number of the conductive portions 12 .

[0066] Specifically, Figure 6 As shown, each pixel region 101 is formed with two conductive portions 12, which are defined as a first conductive portion 12a and a second conductive portion 12b, respectively. The first conductive portion 12a and the second conductive portion 12b are both connected to at least two photoelectric conversion elements PD;

[0067] The first conductive portion 12a is located in the middle of the pixel region 101, and a plurality of photoelectric conversion elements PD are arranged around the first conductive portion 12a in a circumferential direction and spaced from each other. The first conductive portion 12a connects the photoelectric conversion elements PD.

[0068] The second conductive portion 12b includes a plurality of conductive sections 124 spaced apart from each other, at least one conductive section 124 is connected between two adjacent photoelectric conversion elements PD, and electron transfer is achieved between two adjacent photoelectric conversion elements PD via the conductive section 124. In this embodiment, the first conductive portion 12a and the second conductive portion 12b are at least partially embedded in the second isolation structure 13.

[0069] Please refer to the above for the structure and function of the image sensor, which will not be repeated here.

[0070] Fourth embodiment

[0071] Figure 7a is a schematic diagram of a partial cross-sectional structure of an image sensor along a third direction according to a fourth embodiment of the present application, Figure 7b is a schematic diagram of a partial cross-sectional structure of an image sensor according to a fourth embodiment of the present application along a line parallel to the first surface, such as Figure 7a and Figure 7b As shown, the image sensor of this embodiment has substantially the same structure and function as the image sensor of the above-mentioned embodiment, except that the structure of the isolation region 13 is different.

[0072] Specifically, Figure 7a and Figure 7b As shown, the isolation region 1011 includes a connection portion 1012 and a plurality of isolation portions 1013 connected to the connection portion 1012, each isolation portion 1013 is disposed between two adjacent photoelectric conversion elements PD, and the plurality of photoelectric conversion elements PD are disposed at intervals around the circumference of the connection portion 1012. In this embodiment, the connection portion 1012 is located in the middle region of the pixel region 101, and one end of the connection portion 1013 extends to the first isolation structure 11; in this embodiment, the isolation region 1011 includes four isolation portions 1013, and the connection portion 1012 and the four isolation portions 1013 are combined into a cross shape, one side of each isolation portion 1013 is connected to the connection portion 1012, and the other side of each isolation portion 1013 is connected to the first isolation structure 11.

[0073] In a further example, the opposite ends of each isolation portion 1013 extend to the first surface 111 and the second surface 112, respectively. In addition, the opposite ends of the connection portion 1012 extend to the first surface 111 and the second surface 112, respectively. In one implementation, the connection portion 1012 is formed based on the material of the semiconductor substrate 10, and the isolation portion 1013 may include an ion doping region. For example, the isolation portion 1013 may be formed by P-type ion doping from the second surface 112, and may be configured the same as the first isolation structure 11. That is, during the ion doping process, the region corresponding to the connection portion 1012 of the isolation region 13 is not doped, while the region corresponding to the isolation portion 1013 is doped to achieve isolation of the photoelectric conversion element. In other embodiments, the central region of the corresponding pixel region of the isolation region 13 may be doped, and there is an opening in the isolation region between two adjacent photoelectric conversion elements that is not ion-implanted, so that the opening can serve as a through-conducting portion. For example, for four photoelectric conversion element pixel regions, the central region of the cross-shaped isolation is doped, and there are openings in the four branches for partial doping. It should be noted that, in the solution where the connecting portion 1012 and the isolating portion 1013 exist, the second isolating structure 13 in the above embodiment corresponds to the isolating portion 1013 , that is, the connecting portion 1012 may exist in the middle opening region.

[0074] Optionally, at least one conducting portion 12 is embedded in the connecting portion 1012, for example, the conducting portion 12 connects each photoelectric conversion element PD, that is, the conducting portion 12 is connected to four photoelectric conversion elements PD respectively. In one implementation, the connecting portion 1012 can directly serve as the conducting portion 12, and in other implementations, ion doping can be additionally performed based on the description of the above embodiment to form the conducting portion.

[0075] In another optional example, at least one conducting portion 12 is embedded in the isolation portion 1013 to connect adjacent photoelectric conversion elements PD isolated by the isolation portion 1013. Of course, the conducting portion 12 may also be embedded in both the connecting portion 1012 and the isolation portion 1013. Figure 7a As shown, in an optional embodiment, the connecting portion 1012 can also be directly used as the conductive portion 12 for connecting each photoelectric conversion element PD in the pixel area. In this embodiment, the conductive portion 12 includes a first end surface 121 and a second end surface 122 that are oppositely arranged, the first end surface 121 is coplanar with the first surface 111, and the second end surface 122 is coplanar with the second surface 112.

[0076] Fifth embodiment

[0077] Figures 8 to 10 is a flowchart of a method for manufacturing an image sensor according to the fifth embodiment of the present application. Figures 8 to 10 , and refer to Figures 1 to 5The present application also relates to a method for manufacturing an image sensor, which is used to manufacture the above-mentioned image sensor. The method for manufacturing the image sensor includes:

[0078] A semiconductor substrate 10 is provided, wherein a plurality of pixel regions 101 are defined in the semiconductor substrate 10;

[0079] Performing first ion doping on the semiconductor substrate 10 to form a first isolation structure 11, wherein the first isolation structure 11 separates the semiconductor substrate 10 into a plurality of pixel regions 101;

[0080] Performing second ion doping on each pixel region 101 to form at least two photoelectric conversion elements PD, each pixel region 101 includes an isolation region 1011, and the isolation region 1011 separates each photoelectric conversion element PD;

[0081] A conductive portion 12 for electron movement is formed in each pixel region 101 , and the conductive portion 12 connects at least two photoelectric conversion elements PD. Electrons generated by each connected photoelectric conversion element PD can move to other photoelectric conversion elements PD through the conductive portion 12 .

[0082] The manufacturing method of the image sensor of the present application can form a conductive portion 12 between at least two photoelectric conversion elements PD; the conductive portion can provide an electron movement path for electrons to flow to other photoelectric conversion elements, and the linearity of the combined signal of each photoelectric conversion element in the pixel area can be improved by controlling the potential barrier between the photoelectric conversion element and the floating diffusion area to be greater than the potential barrier of the conductive portion; if the full well capacity (FWC) of a certain photoelectric conversion element PD is exceeded, the conductive portion 12 can provide an electron movement path for excess electrons to flow to other photoelectric conversion elements PD, and the electron energy generated by the light received by the pixel area 101 is not affected by the spatial limitations of each photoelectric conversion element PD, and the electrons can be accumulated in each photoelectric conversion element PD. The image sensor manufactured by the present method has a better photosensitivity and a higher linearity of the combined signal; the present method is conducive to realizing pixel area barrier control and improving signal transmission capability.

[0083] Optionally, see Figures 8 to 10 , the isolation region 1011 includes a first region and a second region, and the manufacturing method further includes:

[0084] Performing third ion doping (such as P-type ion doping) on ​​the first region to form a second isolation structure 13, wherein the second isolation structure 13 separates the photoelectric conversion elements PD;

[0085] The third ion doping is not performed on the second region, and the second region forms a conducting portion 12 .

[0086] In this implementation, the conductive portion 12 may be automatically formed after the third ion doping is performed to form the second isolation structure 13 , wherein the material of the conductive portion 12 may be the material of the semiconductor substrate 10 , such as P epitaxial.

[0087] In another implementation, the second ion doping is performed corresponding to each pixel region 101 to form a photoelectric conversion initial formation region, and the first region and the second region both correspond to the photoelectric conversion initial formation region;

[0088] Performing third ion doping on the first region to form a second isolation structure 13, wherein the second isolation structure 13 separates the photoelectric conversion elements PD;

[0089] The third ion doping is not performed on the second region, and the second region forms a conducting portion 12 .

[0090] In this implementation, an N-type photoelectric conversion initial formation region is formed corresponding to the pixel area, and a conductive portion 12 is automatically formed after a third ion doping is performed to form a second isolation structure 13. At this time, the material of the conductive portion 12 can be the material of the photoelectric conversion initial formation region, for example, an N-type doped conductive portion.

[0091] In this embodiment, the impurities of the conductive portion 12 are the same as the impurities of the non-ion-doped region of the semiconductor substrate 10 (or the previously formed photoelectric conversion initial formation region). This process for forming the conductive portion 12 can reduce the ion doping steps and reduce production costs.

[0092] Optionally, the manufacturing method also includes: forming multiple transfer transistors TX and a shared floating diffusion area FD in each pixel area 101; wherein each transfer transistor TX is respectively connected to each photoelectric conversion element PD, the floating diffusion area FD is connected to each transfer transistor TX, and each transfer transistor TX is used to transfer the charge in each photoelectric conversion element PD to the floating diffusion area FD.

[0093] Optionally, the manufacturing method further includes: forming a reset transistor RST and a source follower transistor SF in each pixel region 101, the source follower transistor SF is used to output an electrical signal of the floating diffusion region FD, and the reset transistor RST is at least used to reset the floating diffusion region FD.

[0094] Optionally, the manufacturing method further includes: forming a selection transistor RS in each pixel region 101, the selection transistor RS is used to select and output the electrical signal output by the source follower transistor SF to a column line.

[0095] The functions and structures of the transfer transistor TX, the floating diffusion region FD, the reset transistor RST, the source follower transistor SF, and the select transistor RS are described above and will not be described again. It should be noted that in the manufacture of the image sensor, the process of the devices corresponding to each pixel circuit can be performed with reference to the prior art.

[0096] Optionally, the manufacturing method also includes: controlling the potential barriers between the photoelectric conversion elements PD connected based on the conductive part 12, between the photoelectric conversion element PD and the floating diffusion area FD, and the potential barrier of the conductive part 12 by doping, so that the potential barrier between adjacent photoelectric conversion elements PD connected based on the conductive part 12 is greater than the potential barrier between the photoelectric conversion element PD and the floating diffusion area FD, and the potential barrier between the photoelectric conversion element PD and the floating diffusion area FD is greater than the potential barrier of the conductive part 12.

[0097] In an optional example, the concentration of N-type ion doping of the finally formed N-type ion-doped conductive portion 12 may be the same as the concentration of N-type ion doping of the connected photoelectric conversion element PD. In another optional example, the concentration of P-type ion doping of the finally formed P-type ion-doped conductive portion 12 is less than the doping concentration of the P-type isolation of the isolated connected photoelectric conversion element PD inside the corresponding pixel region.

[0098] Optionally, the manufacturing method further comprises at least one of the following:

[0099] The conductive portion 12 connects each photoelectric conversion element PD;

[0100] The conducting portion 12 is located in the middle of the pixel region 101, and a plurality of photoelectric conversion elements PD are arranged at intervals around the circumference of the conducting portion 12;

[0101] The conducting portion 12 includes a plurality of conducting sections 124 spaced apart from each other, at least one conducting section 124 is connected between two adjacent photoelectric conversion elements PD, and electron transfer is achieved between the two adjacent photoelectric conversion elements PD through the conducting section 124;

[0102] Each pixel region 101 is formed with two conductive portions 12, including a first conductive portion 12a and a second conductive portion 12b, wherein the first conductive portion 12a and the second conductive portion 12b are both connected to at least two photoelectric conversion elements PD;

[0103] The first conductive portion 12a is located in the middle of the pixel region 101, and a plurality of photoelectric conversion elements PD are arranged around the first conductive portion 12a in a circumferential direction and spaced from each other. The first conductive portion 12a connects the photoelectric conversion elements PD.

[0104] The second conductive portion 12 b includes a plurality of conductive sections 124 spaced apart from each other. At least one conductive section 124 is connected between two adjacent photoelectric conversion elements PD, and electron transfer is achieved between the two adjacent photoelectric conversion elements PD via the conductive section 124 .

[0105] Optionally, the manufacturing method further comprises at least one of the following:

[0106] The semiconductor substrate 10 includes a first surface 111 and a second surface 112 that are opposite to each other, and a distance exists between the conductive portion 12 and at least one of the first surface 111 and the second surface 112;

[0107] The conducting portion 12 includes a first end surface 121 and a second end surface 122 that are oppositely disposed. The first end surface 121 is coplanar with the first surface 111 , and the second end surface 122 is coplanar with the second surface 112 .

[0108] The conductive portion 12 may be formed only in the middle of the pixel region 101 (see above). Figure 5 As shown; or only formed between two adjacent photoelectric conversion elements PD, such as Figure 4 As shown, or a conductive portion 12 is formed between two adjacent photoelectric conversion elements PD and in the middle of the pixel region 101, as shown in FIG. Figure 6 shown.

[0109] Sixth embodiment

[0110] Figures 11 to 13 is a flowchart of a method for manufacturing an image sensor according to the sixth embodiment of the present application. Figures 11 to 13 The manufacturing method of the image sensor of this embodiment is substantially the same as the manufacturing method of the image sensor of the fifth embodiment, except that the formation method of the conductive portion 12 is different.

[0111] For details, please refer to Figures 11 to 13 , the manufacturing method further comprises:

[0112] Each pixel region 101 includes an isolation region 1011 , and the isolation region separates each photoelectric conversion element PD;

[0113] Performing fourth ion doping on the isolation region 1011 to form an initial formation region of an isolation structure;

[0114] The fifth ion doping is performed locally on the initial formation region of the isolation structure to form the second isolation structure 13 and the conductive portion 12 , wherein the region corresponding to the fifth ion doping forms the conductive portion 12 , and the second isolation structure 13 separates the photoelectric conversion elements PD.

[0115] In this implementation, an initial formation area of ​​an isolation structure is first formed inside the pixel area, based on which additional ion doping is performed to form a conductive portion 12. At the same time, the remaining part of the initial formation area of ​​the isolation structure automatically forms a second isolation structure 13. In this example, the fifth ion doping can be N-type ion doping to form an N-type doped conductive portion, and the fourth ion doping can be P-type ion doping.

[0116] The conductive portion 12 may be formed only in the middle of the pixel region 101 (see above). Figure 5 As shown; or only formed between two adjacent photoelectric conversion elements PD, such as Figure 4 As shown, or a conductive portion 12 is formed between two adjacent photoelectric conversion elements PD and in the middle of the pixel region 101, as shown in FIG. Figure 6 shown.

[0117] Seventh embodiment

[0118] Please continue to see Figures 11 to 13 As shown, the manufacturing method of the image sensor of this embodiment is substantially the same as the manufacturing method of the image sensor of the above embodiment, except that the formation order of the first isolation structure 11 and the second isolation structure 13 is different.

[0119] Specifically, the manufacturing method further includes: while performing first ion doping on the semiconductor substrate 10 to form the first isolation structure 11 , forming an isolation structure initial formation region in the isolation region 1011 ;

[0120] The fifth ion doping is performed locally on the initial formation area of ​​the isolation structure to form a second isolation structure 13 and a conductive portion 12, wherein the fifth ion doped area forms the conductive portion 12, and the second isolation structure 13 divides the pixel area 101 into a plurality of sub-pixel areas; and the second ion doping performed to form a plurality of photoelectric conversion elements PD corresponds to the area of ​​each sub-pixel area.

[0121] Eighth embodiment

[0122] Figures 14 to 16 FIG. 1 is a flow chart of a method for manufacturing an image sensor according to the seventh embodiment of the present application. Figures 14 to 16 The manufacturing method of the image sensor of this embodiment is substantially the same as the manufacturing method of the image sensor of the above-mentioned embodiment, except that the formation method of each photoelectric conversion element PD of each pixel region 101 is different.

[0123] For details, please refer to Figures 14 to 16 , the manufacturing method further comprises:

[0124] The second ion doping is performed corresponding to each pixel region 101 to form a photoelectric conversion initial formation region, such as Fig.14 As shown;

[0125] Performing fourth ion doping on the photoelectric conversion initial formation region to form an isolation structure initial formation region;

[0126] The fifth ion doping is performed locally on the isolation structure initial formation region to form a second isolation structure 13 and a conductive portion 12, wherein the fifth ion doped region forms the conductive portion 12, and the second isolation structure 13 divides the photoelectric conversion initial formation region into a plurality of photoelectric conversion elements PD.

[0127] The above embodiments are merely illustrative of the principles and effects of the present application and are not intended to limit the present application. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present application shall still be covered by the claims of the present application.

Claims

1. An image sensor, characterized in that: The image sensor includes a semiconductor substrate in which a first isolation structure is formed. The first isolation structure divides the semiconductor substrate into a plurality of pixel regions. Each of the pixel regions is formed with a plurality of photoelectric conversion elements and at least one conductive portion connecting at least two of the photoelectric conversion elements. The electrons generated by the connected photoelectric conversion elements can move to other photoelectric conversion elements through the conductive portion. Each of the pixel regions also includes an isolation region, which separates the photoelectric conversion elements.

2. The image sensor according to claim 1, wherein: The isolation region is formed with a second isolation structure, the second isolation structure separates the photoelectric conversion elements, and the conductive portion is formed in the isolation region.

3. The image sensor according to claim 1, wherein: The isolation region includes a connection portion and a plurality of isolation portions connected to the connection portion, each of the isolation portions is arranged between two adjacent photoelectric conversion elements, and a plurality of photoelectric conversion elements are arranged around the connection portion in a circumferential direction and spaced apart from each other; the connection portion serves as the conductive portion.

4. The image sensor according to claim 3, wherein: At least one of the conducting parts is embedded in the connecting part and the isolating part, and the conducting part connects the photoelectric conversion elements.

5. The image sensor according to claim 1, wherein: Include at least one of the following: The conductive portion connects the photoelectric conversion elements in the pixel area; The conducting portion is located in the middle of the pixel region, and a plurality of the photoelectric conversion elements are arranged around the circumference of the conducting portion and spaced from each other; The conductive portion includes a plurality of conductive sections spaced apart from each other, at least one conductive section is connected between two adjacent photoelectric conversion elements, and electron transfer is achieved between the two adjacent photoelectric conversion elements through the conductive section; Each of the pixel regions is formed with at least two of the conductive portions; The semiconductor substrate comprises a first surface and a second surface arranged opposite to each other, and a distance is provided between the conductive portion and at least one of the first surface and the second surface; The conducting portion includes a first end surface and a second end surface that are opposite to each other, wherein the first end surface is coplanar with the first surface, and the second end surface is coplanar with the second surface.

6. The image sensor according to any one of claims 1 to 5, characterized in that The pixel region is formed with a plurality of transfer transistors and a shared floating diffusion region, each of the transfer transistors is respectively connected to each of the photoelectric conversion elements, the floating diffusion region is connected to each of the transfer transistors, and each of the transfer transistors is used to transfer the charge in each of the photoelectric conversion elements to the floating diffusion region.

7. The image sensor according to claim 6, wherein: A reset transistor and a source follower transistor are formed in each pixel region. The source follower transistor is used to output the electrical signal of the floating diffusion region; and the reset transistor is used to at least reset the floating diffusion region.

8. The image sensor according to claim 7, wherein: A selection transistor is also formed in each pixel region, and the selection transistor is used to select and output the electrical signal output by the source follower transistor to a column line.

9. The image sensor according to claim 6, wherein: When a source follower transistor is formed, the source follower transistor is arranged in the middle of the pixel area, and the plurality of photoelectric conversion elements are located on the peripheral side of the source follower transistor. The floating diffusion area includes at least two sub-floating diffusion nodes, and the sub-floating diffusion nodes are connected to at least two of the photoelectric conversion elements based on the corresponding transfer transistor.

10. The image sensor according to claim 6, wherein: Include at least one of the following: Based on the fact that the potential barrier between the adjacent photoelectric conversion elements connected by the conductive portion is greater than the potential barrier between the photoelectric conversion element and the floating diffusion region, the potential barrier between the photoelectric conversion element and the floating diffusion region is greater than the potential barrier of the conductive portion; 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 one-to-one correspondence with each of the pixel regions; The image sensor further comprises a lens array, which is arranged on the light incident side of the color filter array. The lens array comprises a plurality of lens units, and each of the lens units is arranged in one-to-one correspondence with each of the color filter units.

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