Pixel structure and image sensor with shared pixel layout structure

Abstract

The application provides a pixel structure and an image sensor with a shared pixel layout structure, comprising a semiconductor substrate, a photoelectric conversion region, a charge collection region and a charge transport element, the photoelectric conversion region extends from a second surface to the semiconductor substrate, the charge collection region extends from the second surface to the semiconductor substrate, the charge transport element is located above a region of the photoelectric conversion region, the charge transport element comprises a first transport region and a second transport region which are adjacently arranged along a preset direction, the first transport region and the second transport region are arranged to have a first width and a second width respectively along the preset direction of the photoelectric conversion region as an extension direction, the first width is greater than the second width, and an included angle is formed between the preset direction and a charge transport direction. The application optimizes the pixel layout, reduces the light blocking area of the charge transport element on the photoelectric conversion region, thereby improving the color matching degree inside the pixel unit and improving the color unevenness.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of image sensors, in particular to a pixel structure and an image sensor with a shared pixel layout structure. BACKGROUND

[0002] Image sensors are an important component of digital cameras. According to different elements, they can be divided into two categories: CCD (Charge-Coupled Device) and CMOS (Complementary Metal-Oxide-Semiconductor). With the continuous development of CMOS integrated circuit manufacturing processes, especially the design and manufacturing processes of CMOS image sensors (CIS, CMOS Image Sensor), CMOS image sensors have gradually replaced CCD image sensors and become the mainstream. Compared with CCD image sensors, CMOS image sensors have higher industrial integration and lower power consumption.

[0003] A CMOS image sensor includes a pixel array, each pixel unit in the pixel array including a photodiode (PD), a charge transfer gate, and a floating diffusion region (FD), wherein the transfer gate controls the flow of photo-generated electrons between the photodiode and the floating diffusion region. The conventional pixel transfer gate layout design is typically a one-word long gate type. The purpose of this layout design is to effectively lock the electrons in the PD and to smoothly flow the photo-generated electrons into the FD.

[0004] Existing image sensors often have problems such as suboptimal imaging quality due to unreasonable pixel layout design. For example, unreasonable pixel layout design leads to differences in light sensitivity between different pixels, and in addition, differences in light sensitivity between pixels lead to color mismatch and color unevenness. With the increasing demand for overall performance of image sensors and the decreasing design of pixel size, the requirement for consistency of performance between different pixels is increasingly stringent, especially the light blocking of the transfer gate leading to the light sensitivity difference between pixels becomes unacceptable.

[0005] Therefore, it is necessary to provide a pixel structure and an image sensor with a shared pixel layout structure to solve the above problems in the prior art.

[0006] It should be noted that the above introduction to the technical background is only for the convenience of clearly and completely describing the technical scheme of the present application, and for the convenience of understanding by those skilled in the art. The above technical scheme cannot be considered as known to those skilled in the art just because it is described in the background section. SUMMARY

[0007] In view of the above-mentioned shortcomings of the prior art, the present application aims to provide a pixel structure and an image sensor with a shared pixel layout structure to solve the problem of the influence of the existing pixel layout on the imaging quality of the image sensor.

[0008] To achieve the above object and other related objects, the present application provides a pixel structure, comprising:

[0009] a semiconductor substrate comprising a first face and a second face opposite to each other;

[0010] a photoelectric conversion region extending from the second face into the semiconductor substrate;

[0011] a charge collection region extending from the second face into the semiconductor substrate;

[0012] a charge transport element located above a region of the photoelectric conversion region and configured to transport charges collected via the photoelectric conversion region to the charge collection region, the charge transport element comprising a first transport region and a second transport region located adjacent to each other along a preset direction, and the first transport region and the second transport region of the charge transport element are respectively configured to have a first width and a second width along a preset direction of the photoelectric conversion region as an extension direction, wherein the first width is greater than the second width, and there is an included angle between the preset direction and a charge transport direction.

[0013] Optionally, the charge transport element is located above a corner portion of the photoelectric conversion region and configured to transport charges collected via the photoelectric conversion region to the charge collection region, the charge transport element comprising a first transport region and a second transport region located adjacent to each other along a tangent direction of the photoelectric conversion region, the first transport region being close to the charge collection region, and the first transport region and the second transport region of the charge transport element are respectively configured to have a first width and a second width along the tangent direction of the photoelectric conversion region as an extension direction.

[0014] Optionally, the first transport region is closer to the charge collection region than the second transport region.

[0015] Optionally, the second width is between 40% and 80% of the first width.

[0016] Optionally, the photoelectric conversion region comprises a light-sensing doped region and an additional doped region not exceeding an outer contour of the light-sensing doped region, a normal projection of the charge transport element overlapping the photoelectric conversion region is at least within the additional doped region, the additional doped region has a same doping type as the light-sensing doped region, and a doping concentration of the additional doped region is greater than a doping concentration of the light-sensing doped region.

[0017] Optionally, the additional doped region is at least provided at a corner portion of the photoelectric conversion region, and the second transport region of the charge transport element does not overlap the additional doped region.

[0018] Optionally, the pixel structure further comprises a doped bulk region extending from the second surface of the semiconductor substrate towards the interior of the semiconductor substrate, the photoelectric conversion region and the charge collection region are located in the doped bulk region and the doped bulk region spans the charge transport element, and at least the first transport region of the charge transport element and the doped bulk region have an overlap.

[0019] Optionally, the photoelectric conversion region comprises a plurality of concentration doped regions with a doping concentration decreasing in sequence from the second surface of the semiconductor substrate towards the interior, and the plurality of concentration doped regions are arranged at least in the region where the photoelectric conversion region covers the charge transport element.

[0020] Optionally, the photoelectric conversion region comprises a plurality of concentration doped regions with a doping concentration decreasing in sequence from the second surface of the semiconductor substrate towards the interior, and the plurality of concentration doped regions correspond to the entire photoelectric conversion region along a plane parallel to the surface of the semiconductor substrate.

[0021] Optionally, the charge transport element further comprises a transport connecting portion, the transport connecting portion is adjacent to the second transport region and extends to the side of the photoelectric conversion region.

[0022] Optionally, the width of the transport connecting portion is greater than the width of the second transport region.

[0023] Optionally, the photoelectric conversion region is integrally formed in a square shape with a cut corner, a rectangular shape or an octagonal shape, and the first transport region of the charge transport element partially overlaps the cut corner section of the photoelectric conversion region.

[0024] Optionally, the pixel structure further comprises an isolation region, the isolation region extends from the second surface of the semiconductor substrate towards the first surface to the interior of the semiconductor substrate, and the isolation region is arranged at the periphery of the photoelectric conversion region, wherein the first transport region and the second transport region of the charge transport element both have an overlap with the isolation region.

[0025] Optionally, the charge transport element further comprises a transport functional region, the transport functional region is located on the side of the first transport region away from the second transport region and extends to the isolation region.

[0026] Optionally, the photoelectric conversion region comprises an extension portion protruding towards the charge collection region from the cut corner section along the charge transport direction thereof, the arrangement direction of the first transport region and the second transport region of the charge transport element intersects with the protruding direction of the extension portion of the photoelectric conversion region towards the charge collection region, and the first transport region of the charge transport element covers the extension portion.

[0027] The present application also provides an image sensor with a shared pixel layout structure, the image sensor comprising:

[0028] a color filter layer having light passages between the color filter layer and the semiconductor substrate to direct incident light filtered by the color filter layer to corresponding disposed photoelectric conversion regions;

[0029] at least two pixel structures as described above arranged in a matrix, wherein at least two adjacent pixel structures share one charge collection region;

[0030] a source follower transistor having a gate electrically connected to the corresponding charge collection region.

[0031] Optionally, the shared pixel layout structure comprises:

[0032] four pixel structures arranged in a matrix, the four pixel structures sharing two charge collection regions arranged oppositely in the middle of the matrix, wherein two adjacent first pixel structures share one first charge collection region, and two adjacent second pixel structures share one second charge collection region.

[0033] the source follower transistor is disposed between the first charge collection region and the second charge collection region.

[0034] Optionally, the shared pixel layout structure comprises: two pixel structures arranged in a matrix, the two pixel structures sharing one charge collection region, the source follower transistor being disposed on one side of the charge collection region, and a reset transistor and / or a gain control transistor being disposed on the other side of the charge collection region and between two photoelectric conversion regions sharing the same charge collection region.

[0035] Optionally, the image sensor comprises a pixel array comprising a plurality of pixel units arranged periodically, wherein each pixel unit comprises at least four pixel structures arranged in the shared pixel layout structure.

[0036] Optionally, the image sensor comprises a pixel array, a plurality of pixel units arranged periodically to form the pixel array, each pixel unit comprising at least four pixel structures arranged in the shared pixel layout structure; when the transmission connection part exists, the transmission connection part in each pixel unit is arranged at the side of the pixel unit.

[0037] Optionally, the color filter layer is provided with a plurality of color filter arrays arranged periodically, each color filter array is disposed corresponding to a pixel unit and comprises color filters arranged in a matrix, and the color components of the light filtered by the color filters are guided to the corresponding photoelectric conversion regions in the pixel units arranged in the shared pixel layout structure through the light passages, wherein the color filters of the same color are arranged along the diagonal direction of the color filter array.

[0038] As described above, the pixel structure and the image sensor with shared pixel layout structure of the present application, by optimizing the pixel layout, setting the charge transport element into the first transport region and the second transport region extending in the direction of the cut angle of the photoelectric conversion region, reducing the light blocking effect on the photoelectric conversion region, thereby improving the color matching degree inside the pixel unit and improving the color non-uniformity; in addition, by setting the light-doped region and the additional doped region not exceeding the outer contour of the light-doped region in the photoelectric conversion region, increasing the ion implantation concentration near the surface of the photoelectric conversion region below the charge transport element, as a compensation for the reduction of the area of the charge transport element, enhancing the charge transfer capability, thereby reducing the influence of charge residue on image lag. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 The basic structure block diagram of an image sensor system is shown.

[0040] Figure 2 The schematic diagram of a pixel circuit of an image sensor is shown.

[0041] Figure 3 The schematic diagram of a pixel structure in an embodiment of the present application is shown.

[0042] Figure 4 The structural schematic diagram of a pixel structure in an embodiment of the present application is shown.

[0043] Figure 5 The top view schematic diagram of a pixel structure in an embodiment of the present application including an additional doped region is shown.

[0044] Figure 6 The side view schematic diagram of a plurality of concentration doped regions in a pixel structure in an embodiment of the present application is shown.

[0045] Figure 7(a), Figures 7(b) to 8 The structural schematic diagram of an image sensor with shared pixel layout structure in an embodiment of the present application is shown, wherein Figure 7(a) shows the schematic diagram of two shared pixel layout structures, and Figure 7(b) shows the schematic diagram of a pixel unit composed of two two-shared pixel layout structures, Figure 8 The schematic diagram of a four-shared pixel layout structure is shown.

[0046] Figure 9A And Figure 9B The schematic diagram of a pixel structure in the prior art is shown.

[0047] Figures 10A to 10B The measured results of color matching degree and color uniformity of the image sensor made of the pixel structure of the embodiment and the comparative example of the present application are shown in the graph.

[0048] Element number explanation

[0049] 10-pixel structure

[0050] 100 Semiconductor substrate

[0051] 202 Photoelectric Conversion Zone

[0052] 104 Charge Collection Region

[0053] 106, 206 charge transport elements

[0054] 2061 First Transmission Area

[0055] 2062 Second Transmission Area

[0056] 110 doped host region

[0057] 120 Isolation Zone

[0058] 2021 Photosensitive Doped Region

[0059] 2022 Additional Doped Region

[0060] 2023 Extension

[0061] 2031, 2032…203n First concentration doped region, Second concentration doped region…Nth concentration doped region

[0062] 2064 Transmission Connection Section

[0063] 2065 Transmission Function Area

[0064] W1 First Width

[0065] W2 Second Width Detailed Implementation

[0066] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0067] Please see Figures 1 to 10B It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Although the illustrations only show components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation, the shape, quantity and proportion of each component in the actual implementation can be arbitrarily changed, and the layout of the components may also be more complex.

[0068] Figure 1A system architecture diagram is shown as an image sensor, which includes a pixel array and a readout circuit and a control circuit connected to the pixel array, the pixel array includes a two-dimensional pixel array, for example, the shown pixels P1, P2, P3...Pn are configured as several rows (illustrated as R1, R2...Ry) and several columns (illustrated as C1, C2...Cx), the pixel signals output by the pixel array are output to the readout circuit through column lines. A functional logic unit is connected to the readout circuit, and a state register is connected to the readout circuit and the control circuit, the image data can be read out from the readout circuit according to the readout mode set by the functional logic unit or the state register, and then transmitted to the functional logic unit, thereby realizing the read control of the pixel array.

[0069] In some applications, the state register can include a digitally programmed selection system for determining whether the readout system reads by a global shutter or a rolling shutter. The operation of the control circuit can be determined by the current setting of the state register, for example, the control circuit can generate an exposure signal for controlling image acquisition, such as reading by a global exposure signal or a rolling exposure signal.

[0070] Figure 2 A pixel circuit diagram of a three-transistor (3T) pixel unit of an image sensor is shown, the shown image sensor reads image data in a rolling exposure mode, wherein the pixel circuit includes a reset transistor (RST), a source follower transistor (SF), and the shown pixel circuit is coupled to a transfer transistor (TX) and a photodiode (PD) through a floating diffusion point (FD). During a given photodiode integration time, photons enter the photoconversion region via a light path, generating electron-hole pairs. After the integration period, a transfer pulse signal is applied to the transfer transistor (TX), and the accumulated charge inside the photodiode (PD) is transferred to the floating diffusion point (FD), and the floating diffusion point (FD) signal can be read out by the drain voltage VREF of the reset transistor.

[0071] During the operation of the pixel unit, the following relationship exists:

[0072]

[0073] Wherein, N photo represents the incident photons of each pixel; P is the unit plane irradiance, with the unit of W / cm 2 ; A pix is the pixel area, with the unit of cm 2 ; t INTwherein t is the integration time, in seconds; h is the Planck constant. Based on the above equation 1, it can be seen that the quantum efficiency is positively correlated with the number of photo-generated electrons collected by the photoelectric conversion region. Due to the light blocking effect of the transfer gate, the amount of light incident on the photoelectric conversion region will decrease, and the design of the transfer gate in different arrangements will cause differences in the incident light received by the photoelectric conversion region of the corresponding pixel, for example, it will cause the accumulated charge amount between the photoelectric conversion regions (such as Gr and Gb) for receiving the same color component of light in the pixel unit to deviate.

[0074] The existing image sensor often adopts a 2-pixel sharing or 4-pixel sharing layout to shorten the distance between the source follower transistor (SF) and the floating diffusion region (FD) to save the layout area. In addition, for the influence of the pixel layout design on the image tailing, it is found that the layout of the PD, the transfer gate (TG) and the floating diffusion region (FD) will affect the charge transfer, which will be affected by the shape of the transfer gate, so it is necessary to improve the color mismatch and inhibit the charge residual.

[0075] In order to reduce the light blocking of the transmission grid to the photoelectric conversion region as much as possible, and to suppress the difference in incident light intensity of the same color channel entering the same pixel unit, the present application provides a pixel structure, by optimizing the pixel layout, the charge transmission element is arranged as a first transmission region and a second transmission region with a preset direction as the extension direction, in an example, the preset direction is the tangent direction of the photoelectric conversion region, based on the above design, the shape of the second transmission region is changed, such as reducing the size of the second transmission region, so that the light blocking effect of the charge transmission element to the photoelectric conversion region is reduced, thereby improving the light sensitivity difference between the photoelectric conversion regions inside the pixel unit, thereby improving the color matching degree inside the pixel unit and improving the color unevenness. Wherein, the preset direction and the charge transmission direction have an included angle, in addition, further, the first transmission region is arranged close to the charge collection region relative to the second transmission region, so as to facilitate charge transmission based on the first charge transmission region, and to improve the influence of the charge transmission element on the light blocking based on the second charge transmission region. It should be noted that the preset direction can be any direction parallel to the center line of the center of the photoelectric conversion region, and the layout of any transmission element affecting the light sensitivity unevenness between pixels can be improved based on the design of the present application, which is designed in the extension direction, which can reduce the light blocking and reduce the deviation between different pixels. For example, the extension direction of the transmission element (the preset direction) and the electron transmission direction in the transmission channel formed below have an included angle, which can be the extension direction of the gate of the charge transmission element, that is, the gate width L direction, and the channel direction of the charge transmission element, that is, the gate length W direction, so as to facilitate the partitioning of the first transmission region and the second transmission region, and to facilitate the adjustment of the full well and charge tail performance. Of course, other partitioning designs of the charge transmission element other than the first transmission region and the second transmission region can also be performed.

[0076] As Figure 3 shown, the present embodiment provides a pixel structure 10, which includes a semiconductor substrate 100, a photoelectric conversion region 202, a charge collection region 104 and a charge transmission element 206, the semiconductor substrate 100 includes opposite first and second faces 100a and 100b (see Figure 6); photoelectric conversion region 202 extends from the second surface into the semiconductor substrate for receiving a light signal and converting the light signal into an electric charge signal; charge collection region 104 extends from the second surface into the semiconductor substrate; charge transport element 206 is located above a corner portion of the photoelectric conversion region and is configured to transport the electric charge collected via the photoelectric conversion region to the charge collection region 104, the charge transport element 206 includes a first transport region 2061 and a second transport region 2062 arranged along a preset direction, the first transport region 2061 includes a portion having a first width W1, and the second transport region 2062 includes a portion having a second width W2, wherein the first width W1 is greater than the second width W2; in the illustrated example, the charge transport element 206 includes the first transport region 2061 and the second transport region 2062 arranged adjacent to each other along a tangent direction of the corner of the photoelectric conversion region, and the first transport region 2061 and the second transport region 2062 of the charge transport element are respectively arranged to have the first width W1 and the second width W2 along the tangent direction of the corner of the photoelectric conversion region as the extending direction.

[0077] In an example, the second width W2 is between 40% and 80% of the first width W1, for example, it can be selected as 50%, 60%, and in addition, in an optional example, the width is reduced only from the side close to the photoelectric conversion region relative to the second transport region, as shown in the example. Figure 3 Thus, it is beneficial to improve the light shielding effect and adjust the performance of the corresponding image sensor, and facilitate the implementation of the process.

[0078] Based on the above technical solution, by arranging the first transport region and the second transport region adjacent to each other along a preset direction (such as a tangent direction) of the photoelectric conversion region, and the first transport region has a first width greater than the second width of the second transport region; relative to the positioning and shape of the charge transport element in the existing pixel structure, the charge transport element in the pixel structure of the present application has a reduced corresponding area with the photoelectric conversion region in the orthographic projection, reduces the light shielding area of the photoelectric conversion region, can reduce the light intensity difference of the incident light of the photosensitive region on the diagonal, and improves the color matching degree and color uniformity. In this example, the second transport region has a projection area offset from the photoelectric conversion region to the charge collection region relative to the first transport region, and further, the part of the offset projection area has a small second width relative to the first width of the first transport region, the area and the projection position are arranged correspondingly, of course, not limited thereto. In addition, in this example, the light enters from the second surface 100b of the semiconductor substrate 100, constituting a front-illuminated image sensor FSI.

[0079] As Figure 4As shown, in one example, the semiconductor substrate 100 includes a doped host region 110 extending from its second surface into the semiconductor substrate, i.e., an active region. The doped host region 110 has opposite electrical doping to the photoelectric conversion region 202. The doped host region 110 includes an outer contour defining a quadrilateral, octagonal, or similar shape. The photoelectric conversion region 202 is formed within the doped host region 110. In one example, the doped host region 110 is P-type doped, and the photoelectric conversion region 202 is N-type doped. Alternatively, the doped host region can be a region automatically formed within the semiconductor substrate based on isolation regions (such as STI).

[0080] In some embodiments, the photoelectric conversion region 202 and the transistor connected thereto may be formed in the doped host region 110. The photoelectric conversion region 202 is included in a photosensitive element in the semiconductor substrate 100, wherein the photosensitive element may include a photodiode, a pinned photodiode, or a similar device, and the transfer transistor may be an NMOS transistor. Alternatively, in a further optional example, the subsequent charge collection region 104 may also be formed in the doped host region 110.

[0081] like Figure 5 As shown, in one example, the orthographic projection of the first transmission region of the charge transport element overlaps with the corner of the photoelectric conversion region. In a further example, the orthographic projection of the first transmission region of the charge transport element may also overlap with the charge collection region 104. Depending on the situation, the orthographic projection of the second transmission region of the charge transport element overlaps with the photoelectric conversion region. In this example, the orthographic projection of the second transmission region of the charge transport element does not overlap with the photoelectric conversion region, which is beneficial to the transmission of electrical signals and to the improvement of the photosensitivity difference caused by the light blocking of the transmission element. In addition, in an optional example, the second transmission region 2062 extends away from the charge collection region 104.

[0082] In one implementation, see [link to implementation details]. Figure 5, the photoelectric conversion region 202 and the charge collection region 104 are located in the doped bulk region 110 and the doped bulk region 110 spans the charge transport element 206, wherein the photoelectric conversion region 202 is integrally formed into a square shape with a cut corner, a rectangular shape or an octagonal shape, respectively, the first transport region 2061 and the second transport region 2062 of the charge transport element are adjacently arranged along the cut corner direction of a corner of the photoelectric conversion region 202, and the first transport region 2061 of the charge transport element is superposed on a cut corner section of the photoelectric conversion region. The so-called "cut corner direction" herein means a direction of cutting a corner at the corner of a quadrilateral, octagonal or similar shape along a diagonal line of the corner, for example, the cut corner direction of the photoelectric conversion region can be understood as a direction consistent with or slightly deviated from the outer edge of the cut corner section shown. In this example, the cut corner direction is the preset direction, and the extension direction refers to the direction of the grid width L. In addition, the overall shape of the photoelectric conversion region 202 can be understood as the shape of the mask when formed, or as the design shape, for example, the design shape of the n-type ion implantation. In an example, the shape is the design shape of the photoelectrically doped region 2021.

[0083] In some embodiments, the pixel structure further comprises an isolation region 120 located at the periphery of the photoelectric conversion region 202 and surrounding the doped bulk region 110, extending into the interior of the semiconductor substrate from the second surface to the first surface of the semiconductor substrate; in an optional example, the first transport region 2061 and the second transport region 2062 of the charge transport element both have an overlap with the isolation region 120, avoiding a high electric field strength region caused by the superposition of the charge transport element and the isolation region, thereby suppressing the noisy electrons generated in the photoelectric conversion region. For example, the isolation region 120 is a shallow trench isolation structure STI, of course, the isolation region 120 can also be an ion implantation isolation region, which has an opposite electrical doping to the photoelectric conversion region 202.

[0084] In some embodiments, the photoelectric conversion region 202 includes an extension 2023 protruding towards the charge collection region, such as the extension 2023 of the photoelectric conversion region 202 protruding towards the doped bulk region 110 along the diagonal direction of the cut corner section thereof, i.e., the protruding extension of the photoelectric conversion region 202 along the electron transport direction, the first transport region 2061 of the charge transport element is superimposed on the extension 2023, which is conducive to facilitating effective charge transport; the arrangement direction of the first transport region 2061 and the second transport region 2062 of the charge transport element is crossed with the protruding direction of the extension 2023 of the photoelectric conversion region towards the doped bulk region, and the orthographic projection of the second transport region 2062 is not superimposed on the extension 2023, so as to further reduce the light blocking area of the photoelectric conversion region. In the present embodiment, the extension 2023 can also be omitted, such as the design shape of the photoelectric conversion region 202 being octagonal, without the extension to other square shapes. For example, the design shape of the light-sensing doped region 2021 can be octagonal, and the additional doped region 2022 does not exceed the outer contour of the light-sensing doped region 2021.

[0085] As shown in Figure 5 , the orthographic projection of the first transport region 2061 of the charge transport element is superimposed on the extension 2023 and the doped bulk region surrounding the extension, so that the accumulated photo-generated charges are transported via the effective channel formed in the overlapping area of the charge transport element and the extension, avoiding or reducing the situation that the carriers are trapped between the active region and the isolation region. As shown in Figure 4 and Figure 5 , the charge transport element 206 further includes a transport connection portion 2064 adjacent to the second transport region 2062 and extending to the side of the photoelectric conversion region, and forming an electrical connection at the side of the photoelectric conversion region. In an example, an interconnection through hole CT is prepared on the transport connection portion 2064 to provide a gate control signal. In an example, the width of the transport connection portion is greater than the width of the second transport region, so as to facilitate the realization of interconnection based on the transport connection portion, and facilitate the design of the width of the second transport region to improve light shielding while realizing interconnection in the effective area.

[0086] In another optional example, the charge transport element 206 further includes a transport functional region 2065 located on the side of the first transport region away from the second transport region and extending to the isolation region 120. Based on the arrangement of the transport functional region 2065, the effective channel of the corresponding region of the first transport region 2061 can be formed based on the arrangement of the second transport region 2062, which is conducive to the design of the topography of the charge transport, and can strengthen the control of the channel by the transport gate.

[0087] Continuing to refer to Figure 5The photoelectric conversion region 202 includes a light-doped region 2021 and an additional doped region 2022 which does not exceed the outer contour of the light-doped region. The orthogonal projection of the charge transport element 206 on the photoelectric conversion region 202 is at least within the additional doped region 2022. The additional doped region has the same doping type as the light-doped region, and the doping concentration of the additional doped region is greater than that of the light-doped region. By further configuring an additional doped region in the photoelectric conversion region, especially by increasing the electrical doping concentration under the charge transport element, the electron potential barrier on the electron transfer path can be reduced, the charge transport capability can be enhanced, and the image lag can be improved when the second transport region 2062 is provided.

[0088] In some embodiments, the additional doped region 2022 is at least provided at the corner of the photoelectric conversion region, and the second transport region 2062 of the charge transport element is provided not to overlap with the photoelectric conversion region, so as to reduce the blocking of the incident light by the charge transport element.

[0089] For example, the additional doped region 2022 extends to the lower part of the charge transport element 206, which can be an extension after the doping process or diffusion. The additional doped region 2022 can cooperate with the light-doped region 2021 to adjust the formation of the photoelectric conversion region and adjust the potential gradient on the transfer path of the photo-generated charges transferred to the charge collection region. It can be understood that the doping concentration of the additional doped region here can refer to the superposition of the doping ion concentration in the region formed after the second ion doping based on the first ion doping to form the light-doped region. In this example, the design of the additional doped region can effectively improve the light-difference while performing charge transport based on the first transport region when the second transport region 2062 is provided.

[0090] In another implementation, referring to Figure 6 The photoelectric conversion region 202 can include a plurality of concentration doped regions arranged from the second surface of the semiconductor substrate to the inside, i.e., a first concentration doped region 2031, a second concentration doped region 2032, and an Nth concentration doped region 203n with decreasing doping concentrations in sequence. The photoelectric conversion region 202 has a decreasing potential from the second surface of the semiconductor substrate to the inside, thereby improving the electron transport efficiency of the photoelectric conversion region and further improving the image lag problem. In addition, the full well capacity of the photoelectric conversion region can be adjusted based on the plurality of concentration doped regions, so as to adjust the doping concentration, improve the full well capacity, and match the demand of charges transferred to the charge collection region 104 when the second transport region 2062 is provided.

[0091] Referring to Figure 6, the first-concentration-doped region 2031, the second-concentration-doped region 2032, and the Nth-concentration-doped region 203n are arranged at least in the region of the photoelectric conversion region 202 covered by the charge transport element, so that the region under the charge transport element 206 covered by at least the photoelectric conversion region 202 has a reduced electric potential. Of course, the first-concentration-doped region 2031, the second-concentration-doped region 2032, and the Nth-concentration-doped region 203n can also be arranged in the entire photoelectric conversion region, as shown by the doping shown in Figure 6 .

[0092] Those skilled in the art can understand that the embodiments of the present application are not limited to the 3T pixel structure; those skilled in the art who benefit from the present application will understand that the embodiments of the present application can also be applied to 4T designs, 5T designs, and various other pixel structures.

[0093] As shown in Figure 7(a) , 7(b) and Figure 8 , the present embodiment provides an image sensor having a shared pixel layout structure, which includes a color filter layer and at least two pixel structures arranged in a matrix, the color filter layer and the semiconductor substrate having a light passage to guide incident light filtered by the color filter layer to a corresponding photoelectric conversion region 202; the path of the incident light entering the corresponding photoelectric conversion region 202 can be understood as the light passage here; wherein the pixel structure preferably has the structure described in the previous embodiment; two adjacent pixel structures share a charge collection region 104.

[0094] As shown in the image sensor, the image sensor further includes a reset transistor RST and a source follower transistor SF, and in an optional example, the image sensor further includes a gain control transistor DCG, as shown in FIG. 7(a), the gate of the source follower transistor SF is electrically connected to the corresponding charge collection region, for reading and / or discharging the charge accumulated in the charge collection region.

[0095] In an implementation, four pixel structures arranged in a matrix share two charge collection regions, and the two charge collection regions are arranged opposite to each other in the middle of the matrix, wherein two adjacent first pixel structures share a first charge collection region 104a, and two adjacent second pixel structures share a second charge collection region 104b.

[0096] In Figure 8In the shared pixel layout structure shown, the charge transport elements sharing the first charge collection region 104a are arranged opposite to each other to form a first enclosed region, and the charge transport elements sharing the second charge collection region 104b are arranged opposite to each other to form a second enclosed region, and the source follower transistor SF is arranged between the first charge collection region 104a and the second charge collection region 104b, i.e., between the first enclosed region and the second enclosed region.

[0097] In addition, when the shared pixel layout structure further includes a reset transistor and a gain control transistor, in the two-shared structure, the reset transistor and the gain control transistor are located on the other side of the charge collection region and between the two photoelectric conversion regions sharing the same charge collection region, as shown in FIG. 7(a); in the four-shared structure, the reset transistor and the gain control transistor are distributed on both sides of one of the charge collection regions together with the source follower transistor, as shown in FIG. 7(b). Figure 8

[0098] In another implementation, the image sensor includes a pixel array including a plurality of periodically arranged pixel units, wherein each of the pixel units includes at least two pixel structures in the shared pixel layout structure. In an example, FIG. 7(b) shows two-shared pixel structures, and FIG. 7(b) shows four-shared pixel structures. Figure 8

[0099] In an example, when the transport connection part is present, the transport connection part in each of the pixel units is arranged at the side of the pixel unit, for example, in FIG. 7(b), the four transport connection parts in one pixel unit are arranged at the upper and lower sides.

[0100] In some embodiments, the color filter layer is provided with a plurality of periodically arranged color filter arrays, each color filter array is arranged corresponding to a pixel unit and includes color filters arranged in a matrix, and the color components of the light filtered by the color filters are directed to the corresponding photoelectric conversion regions in the pixel units in the shared pixel layout structure, wherein the color filter array can be arranged in a 2x2 matrix of color filters, and the same color light channels are arranged along the diagonal direction of the matrix.

[0101] For example, the color filters in each color filter array can be arranged in an RGGB array. Referring back to Figure 10A and Figure 10B ​​, 202(R) represents a red component filtered from a red (R) color filter directed to a corresponding photoelectric conversion region via a light channel for generating a charge corresponding to the red (R) component, 202(G) represents a green component filtered from a green (G) color filter directed to a corresponding photoelectric conversion region via a light channel for generating a charge corresponding to the green (G) component, and 202(B) represents a blue component filtered from a blue (B) color filter directed to a corresponding photoelectric conversion region via a light channel for generating a charge corresponding to the blue (B) component.

[0102] In Figure 8 In the shared pixel layout structure shown in FIG. 7(b), two groups of two pixel structures arranged in a matrix correspond to form an RGGB array, i.e., two two-shared pixel units form a four-pixel matrix, and the pixels for generating charges corresponding to the green (G) component are arranged along the diagonal of the four-pixel matrix. Based on the technical solutions of the present application, the charge transport elements are designed, which can improve the light sensing difference between the two green light sensing pixels located on the diagonal, so that the light sensing of the green pixels located on the side of the red pixels and the light sensing of the green pixels located on the side of the blue pixels are consistent, which is conducive to obtaining signals with better consistency based on the RGGB array formed based on the above layout, and is conducive to obtaining accurate image information based on the corresponding pixel unit.

[0103] In a comparative example, referring to Figures 9A to 9B In the pixel unit, the upper and lower two pixels share part of the MOS tube, and thus the design of the shared MOS tube leads to the fact that the transfer gates on the upper and lower two pixels must be symmetrical along the X direction. Thus, the form of the charge transport element 106 on each pixel in the RGGB 4-pixel array shown is not completely consistent. In particular, the light introduced into the photoelectric conversion region along the vertical direction of the symmetry axis of the pixel unit cannot pass through the transfer gate composed of the commonly used polycrystalline silicon of the charge transport element 106, and the polycrystalline silicon itself cannot transmit light, Figure 9BThe light rays of the green channel arranged along the diagonal direction are shown. Due to the different light blocking areas of the charge transport element 106, the light intensity incident on the two photoelectric conversion regions 102(G) is different. Specifically, the light intensity received via the upper right green channel will be greater than the light intensity received via the lower left green channel, resulting in color mismatch between different green channels in the same pixel unit.

[0104] In order to illustrate the advantages of the pixel structure of the present application in color matching and color uniformity, the preferred mode of the pixel structure is measured, and the results are shown in Table 1. Figures 10A to 10B As can be seen, by optimizing the shape of the charge transport element in the pixel layout and reducing the light blocking area of the photoelectric conversion region by the charge transport element, the area S of the charge transport element in the pixel structure of the traditional design (Old design) corresponding to the light amount of the Gr and Gb pixels is ΔQ, the area S1 of the charge transport element in the pixel structure of the embodiment (New design) corresponding to the light amount of the Gr and Gb pixels is ΔQ1, S1 is less than S, ΔQ1 is less than ΔQ, wherein the charge transport element in the traditional design is of W1 width, and the charge transport element in the design of the embodiment of the present application is of W1 width and W2 width. It can be seen that in the design of the present application, the effect of color matching is improved by 50%, and the effect of color uniformity is improved by 10%.

[0105] In summary, the pixel structure and the image sensor having a shared pixel layout structure of the present application optimize the pixel layout, set the charge transport element as a first transport region and a second transport region extending in the direction of the cut angle of the photoelectric conversion region, reduce the light blocking effect on the photoelectric conversion region, thereby reducing the light intensity difference entering the adjacent photoelectric conversion region, improving the color matching degree in the pixel unit and improving the color unevenness. Therefore, the present application effectively overcomes the various shortcomings in the prior art and has high industrial utilization value.

[0106] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical thought disclosed by the present application should be covered by the claims of the present application.

Claims

1. A pixel structure, characterized by, The pixel structure comprises: a semiconductor substrate comprising opposite first and second faces; light enters from the second face of the semiconductor substrate; a photoelectric conversion region extending into the semiconductor substrate from the second face; a charge collection region extending into the semiconductor substrate from the second face; a charge transport element located above a region of the photoelectric conversion region and arranged to transport charge collected via the photoelectric conversion region to the charge collection region, the charge transport element comprising first and second transport regions arranged adjacent in a predetermined direction, and the first and second transport regions of the charge transport element are arranged to have a first width and a second width, respectively, in the predetermined direction as an extension direction, wherein the first width is greater than the second width, and the predetermined direction has an included angle with a charge transport direction; wherein the charge transport element is located above a corner portion of the photoelectric conversion region and arranged to transport charge collected via the photoelectric conversion region to the charge collection region, the charge transport element comprising first and second transport regions arranged adjacent in a tangent direction of the photoelectric conversion region, the first and second transport regions of the charge transport element are arranged to have a first width and a second width, respectively, in the tangent direction of the photoelectric conversion region as an extension direction, wherein the first transport region is close to the charge collection region; and / or the second width is between 40%-80% of the first width.

2. The pixel structure of claim 1, wherein: The photoelectric conversion region comprises a light-sensing doped region and an additional doped region not exceeding an outer contour of the light-sensing doped region, a normal projection of the charge transport element overlapping the photoelectric conversion region is at least within the additional doped region, the additional doped region has the same doping type as the light-sensing doped region, and a doping concentration of the additional doped region is greater than a doping concentration of the light-sensing doped region.

3. The pixel structure of claim 2, wherein: The additional doped region is arranged at least at a corner portion of the photoelectric conversion region, and the second transport region of the charge transport element does not overlap the additional doped region.

4. The pixel structure of claim 2, wherein: The pixel structure further comprises a doped bulk region extending into the semiconductor substrate from the second face of the semiconductor substrate, the photoelectric conversion region and the charge collection region are located in the doped bulk region and the doped bulk region spans the charge transport element, and at least the first transport region of the charge transport element and the doped bulk region have an overlap.

5. The pixel structure of claim 1, wherein: The photoelectric conversion region comprises a plurality of concentration doped regions sequentially decreasing in doping concentration from the second face of the semiconductor substrate to the interior, the plurality of concentration doped regions are arranged at least in a region of the photoelectric conversion region covered by the charge transport element or corresponding to the entire photoelectric conversion region along a plane parallel to the surface of the semiconductor substrate.

6. The pixel structure of claim 1, wherein: The charge transport element further comprises a transport connection portion adjacent to the second transport region and extending to a side portion of the photoelectric conversion region; and / or a width of the transport connection portion is greater than a width of the second transport region.

7. The pixel structure of claim 1, wherein: The photoelectric conversion region is integrally formed in a square shape with a cut corner, a rectangular shape, or an octagonal shape, and the first transfer region of the charge transfer element is partially overlaid on the cut corner section of the photoelectric conversion region.

8. The pixel structure of claim 1, wherein: The pixel structure further comprises an isolation region extending from the second surface of the semiconductor substrate to the inside of the semiconductor substrate towards the first surface, the isolation region being disposed at the periphery of the photoelectric conversion region, and the first transfer region and the second transfer region of the charge transfer element both having an overlap with the isolation region.

9. The pixel structure of claim 8, wherein: The charge transfer element further comprises a transfer function region located on the side of the first transfer region away from the second transfer region and extending to the isolation region.

10. The pixel structure of claim 1, wherein: The photoelectric conversion region comprises an extension protruding towards the charge collection region along the charge transfer direction thereof, the arrangement direction of the first transfer region and the second transfer region of the charge transfer element intersects with the protruding direction of the extension of the photoelectric conversion region towards the charge collection region, and the first transfer region of the charge transfer element is overlaid on the extension.

11. An image sensor having a shared pixel layout, comprising: The image sensor comprises: a color filter layer having light passages between the color filter layer and the semiconductor substrate to guide incident light filtered by the color filter layer to the corresponding photoelectric conversion region; at least two pixel structures as claimed in any one of claims 1 to 10 arranged in a matrix, wherein at least two adjacent pixel structures share one charge collection region; a source follower transistor having a gate electrically connected to the corresponding charge collection region.

12. The image sensor of claim 11, wherein, The shared pixel layout structure comprises: four pixel structures arranged in a matrix, the four pixel structures sharing two charge collection regions arranged opposite to each other in the middle of the matrix, wherein two adjacent first pixel structures share a first charge collection region, and two adjacent second pixel structures share a second charge collection region; the source follower transistor is disposed between the first charge collection region and the second charge collection region; Alternatively, the shared pixel layout structure comprises: two pixel structures arranged in a matrix, the two pixel structures sharing one charge collection region, the source follower transistor being disposed on one side of the charge collection region, and a reset transistor and / or a gain control transistor being disposed on the other side of the charge collection region and between two photoelectric conversion regions sharing the same charge collection region.

13. The image sensor of claim 11, wherein: The image sensor comprises a pixel array, a plurality of pixel units being periodically arranged to form the pixel array, wherein each pixel unit comprises at least four pixel structures arranged in the shared pixel layout structure; and / or when the transfer connection part exists, the transfer connection part in each pixel unit is arranged at the side of the pixel unit.

14. The image sensor of claim 13, wherein: The color filter layer is provided with a plurality of periodically arranged color filter arrays, each color filter array is arranged corresponding to a pixel unit and includes color filters arranged in a matrix, and the color components of the light filtered by the color filters are guided to the corresponding photoelectric conversion regions in the pixel units in the shared pixel layout structure through the light channel, wherein the color filters of the same color are arranged along the diagonal direction of the color filter array.

Images