Pixel unit, method of manufacturing the same, and image sensor

Abstract

The application provides a pixel unit and a preparation method thereof and an image sensor, and relates to the technical field of semiconductors.The pixel unit comprises a first conductive layer and an absorption layer.The first conductive layer is located on one side of the absorption layer.The first conductive layer comprises a plurality of spaced optical regulation units.The plurality of spaced optical regulation units are used to change the exit angle of incident light and form refracted light, so that the incident angle of the refracted light matches the refractive index of the absorption layer.The absorption layer is used to scatter and absorb the refracted light to generate an electrical signal, thereby forming an image electrical signal corresponding to the incident light.The pixel unit regulates the incident light through the first conductive layer and the second conductive layer, can improve the absorption rate of the pixel unit to the incident light using a relatively simple structure without reducing the photosensitive performance of the image sensor, and improves the image recognition accuracy of the image sensor.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, and in particular to a pixel unit and its fabrication method, and an image sensor. Background Technology

[0002] With the rapid development of intelligent driving technology, vehicle image sensors have become the core components of intelligent driving environment perception systems, and high quantum efficiency has also become the core research and development direction of vehicle image sensors.

[0003] Currently, the mainstream technical solutions all take increasing the propagation distance of incident light in the photoelectric conversion region of the image sensor as the core technical means. By adding various optical control structures in the image sensor, the incident light is subjected to optical control such as refraction, reflection, and scattering, thereby extending the propagation distance of the incident light in the photoelectric conversion region, thereby improving the absorption efficiency of the image sensor for incident light, and thus improving the photoelectric conversion efficiency and quantum efficiency of the image sensor.

[0004] However, the above-mentioned technical solutions have many insurmountable defects. On the one hand, the additional optical control structure will squeeze the effective photosensitive area of ​​the image sensor, directly reducing the photosensitive performance of the image sensor. On the other hand, the structure of this type of optical control structure is relatively complex, which greatly increases the difficulty of device integration design, lengthens the research and development cycle, and reduces production efficiency. Summary of the Invention

[0005] This application provides a pixel unit and its fabrication method, as well as an image sensor. By setting a first conductive layer and a second conductive layer, the incident light can be modulated. Without reducing the photosensitivity of the image sensor, the absorption rate of the pixel unit for incident light can be improved using a relatively simple structure, thereby further improving the image recognition accuracy of the image sensor.

[0006] The embodiments of this application adopt the following technical solutions: In a first aspect, embodiments of this application provide a pixel unit, which includes a first conductive layer (A1) and an absorption layer (B1). The first conductive layer (A1) is located on one side of the absorption layer (B1). The first conductive layer (A1) includes a plurality of spaced optical control units (3). The plurality of spaced optical control units (3) are used to change the exit angle of the incident light and form refracted light so that the incident angle of the refracted light matches the refractive index of the absorption layer (B1). A portion of the absorption layer (B1) is a photosensitive material used to scatter and absorb the refracted light to generate an electrical signal, thereby forming an image electrical signal corresponding to the incident light.

[0007] Secondly, embodiments of this application provide a method for fabricating a pixel unit, applied to fabricating the pixel unit described in the first aspect, the method comprising: An absorption layer is formed, and a portion of the absorption layer is a photosensitive material used to scatter and absorb the refracted light to generate an electrical signal, thereby forming an image electrical signal corresponding to the incident light. A first conductive layer is formed, the first conductive layer including a plurality of spaced optical control units, the plurality of spaced optical control units being used to change the exit angle of incident light and form refracted light, so that the incident angle of the refracted light matches the refractive index of the absorption layer.

[0008] Thirdly, embodiments of this application provide an image sensor including a plurality of pixel units as described in the first aspect.

[0009] Beneficial effects In this application, by setting a first conductive layer and an absorption layer, and setting multiple spaced optical control units in the first conductive layer, the propagation angle of the incident light can be precisely controlled through the first conductive layer to generate refracted light that matches the refractive index of the second conductive layer. This reduces the reflection loss of the incident light at the interface between the first conductive layer and the absorption layer, ensuring that the vast majority of the incident light can smoothly enter the absorption layer, laying the foundation for improving the utilization rate of the incident light. By dissipating heat from the refracted light through the absorption layer, the transmission path of the refracted light in the absorption layer can be significantly extended, increasing the contact time and interaction probability between the scattered light and the photosensitive material in the absorption layer, significantly improving the absorption efficiency of the incident light, and realizing multi-angle control of the incident light propagation angle and absorption efficiency. This can improve the quantum efficiency of the pixel unit and simultaneously improve the photosensitivity and image recognition accuracy of the image sensor. Attached Figure Description

[0010] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 A schematic cross-sectional view of a first pixel unit provided for an embodiment of this application; Figure 2 A schematic cross-sectional view of a second pixel unit provided for an embodiment of this application; Figure 3 A schematic diagram of a cross-sectional structure of a second conductive layer provided for an embodiment of this application; Figure 4 A schematic diagram of the cross-sectional structure of a third pixel unit provided for an embodiment of this application; Figure 5 A flowchart illustrating the fabrication process of a pixel unit, provided for an embodiment of this application; Figure 6A schematic diagram of the substrate doping cross-sectional structure provided for the fabrication of a pixel unit in an embodiment of this application; Figure 7 A schematic diagram of the cross-sectional structure of the substrate isolation portion during the fabrication process of a pixel unit, provided for an embodiment of this application; Figure 8 A schematic diagram of the cross-sectional structure of the substrate insulating portion and the conductive layer during the fabrication process of a pixel unit, provided for an embodiment of this application; Figure 9 This is a schematic diagram of the cross-sectional structure of the second conductive layer light absorption layer in the pixel unit fabrication process provided in this application embodiment; Figure 10 This is a schematic diagram of the cross-sectional structure of the second conductive layer protrusion in the pixel unit fabrication process provided in this application embodiment; Figure 11 This is a schematic diagram of the cross-sectional structure of the first filling layer in a pixel unit fabrication process provided in an embodiment of this application; Figure 12 This is a schematic diagram of the cross-sectional structure of an optical control unit in a pixel unit fabrication process provided in an embodiment of this application; Figure 13 This is a schematic diagram of the cross-sectional structure of the second filling layer in a pixel unit fabrication process provided in an embodiment of this application; Figure 14 This is a schematic diagram of the structure of an image sensor provided in an embodiment of this application. Detailed Implementation

[0011] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0012] In the embodiments of this application, the terms "first", "second", "third", "fourth" are used to distinguish the same or similar items with essentially the same function and effect, only for the purpose of clearly describing the technical solution of the embodiments of this application, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated.

[0013] In the embodiments of this application, the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0014] In the description of this specification, the terms "one embodiment," "some embodiments," "exemplary embodiment," "example," "specific example," or "some examples," etc., are intended to indicate that a particular feature, structure, material, or characteristic associated with that embodiment or example is included in at least one embodiment or example of this application. The illustrative representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics mentioned may be included in any suitable manner in any one or more embodiments or examples.

[0015] In the embodiments of this application, "multiple" means two or more, and "at least one" means one or more, unless otherwise explicitly specified.

[0016] The features such as "parallel," "perpendicular," and "identical" used in the embodiments of this application include features in the strict sense of "parallel," "perpendicular," and "identical," as well as cases where "approximately parallel," "approximately perpendicular," and "approximately identical" include certain tolerances. Taking into account the measurement and the tolerances associated with the measurement of a specific quantity (e.g., limitations of the measurement system), they represent the acceptable deviation range for a specific value as determined by a person skilled in the art. For example, "approximately" can mean within one or more standard deviations, or within 10% or 5% of the value.

[0017] Unless the context otherwise requires, throughout the specification and claims, the term "comprising" is interpreted as open and encompassing, that is, "including, but not limited to".

[0018] In this specification, "electrical connection" and "coupling" include situations where constituent elements are connected together by a component having some electrical function. There are no particular limitations on the "component having some electrical function" as long as it enables the transmission and reception of electrical signals between the connected constituent elements.

[0019] With the rapid development of intelligent driving technology, the requirements for high quantum efficiency and imaging accuracy of vehicle image sensors, as the core components of environmental perception systems, are becoming increasingly stringent. Image sensors efficiently capture and convert incident light into stable image electrical signals by photoelectric conversion. After signal processing and algorithm analysis by the intelligent driving controller, the image electrical signals complete image recognition tasks such as road condition recognition, obstacle detection, and driving environment perception.

[0020] In related technologies, image sensors mainly improve the absorption efficiency of incident light by adding optical control structures such as diffraction gratings, deep trench reflection structures, and metal light-concentrating reflection layers inside the sensor. This extends the propagation path of incident light in the photoelectric conversion region, thereby improving the photoelectric conversion efficiency and quantum efficiency. However, the aforementioned image sensor technology solutions have many insurmountable shortcomings: on the one hand, the additional optical control structures such as diffraction gratings and deep trenches directly encroach on the effective photosensitive area of ​​the image sensor, reducing the photosensitive and photoelectric conversion performance of the device; on the other hand, the fabrication process of grating-type micro-nano optical structures is complex, requiring additional photolithography masks and relying on high-precision processes such as electron beam lithography, which significantly increases manufacturing costs and reduces production efficiency, making it difficult to meet the high-performance application requirements of in-vehicle intelligent driving perception scenarios.

[0021] Based on this, embodiments of this application provide a pixel unit, such as... Figure 1 , Figure 2 and Figure 4 As shown, the pixel unit includes: a first conductive layer A1 and an absorption layer B1. The absorption layer B1 includes a second conductive layer A2 and a substrate A3. The first conductive layer A1 is located on one side of the substrate A3. The first conductive layer A1 includes a plurality of spaced optical control units 3. The plurality of spaced optical control units 3 are used to change the exit angle of the incident light and form refracted light so that the incident angle of the refracted light matches the refractive index of the second conductive layer A2. The second conductive layer A2 is in contact with the side of the first conductive layer A1 near the substrate A3. At least a portion of the second conductive layer A2 is a photosensitive material used to scatter and refracted light and form scattered light, and / or absorb refracted light. The substrate A3 is used to absorb the scattered light or refracted light to generate an electrical signal, thereby forming an image signal corresponding to the incident light.

[0022] The optical control unit 3 is a subwavelength metasurface micro / nano structure, with multiple optical control units 3 arranged in a preset periodic array along a plane perpendicular to the first direction. High-precision control of the incident light propagation angle can be achieved by coordinating and controlling parameters such as the morphology, size parameters, arrangement period, and refractive index of the optical control units 3. The first direction is the direction from the substrate A3 to the second conductive layer A2.

[0023] For example, when the incident light is infrared light, the subwavelength can be less than 760 nm.

[0024] For example, the cross-sectional width of the optical control unit 3 along the direction perpendicular to the first direction may be smaller than the wavelength of the incident light; the spacing between the centers of the plurality of optical control units 3 is smaller than the wavelength of the incident light.

[0025] When the center-to-center distance between multiple optical control units is less than the wavelength of the incident light, the light cannot undergo significant bifurcation or deflection. Therefore, most of the incident light can only propagate forward in a single direction approximately perpendicular to the first conductive layer, forming refracted light with concentrated direction and minimal energy loss. This unidirectional refracted light is more likely to match the refractive index of the absorption layer, thus significantly reducing interface reflection loss when entering the absorption layer and ensuring that more light can smoothly enter the interior of the absorption layer. At the same time, since the refracted light does not diffuse obliquely, it avoids crosstalk caused by illuminating adjacent pixel units, which helps to improve the image sharpness and color reproduction of the image sensor.

[0026] At least a portion of the second conductive layer A2 is a photosensitive material, which may include, but is not limited to, the following: In the first case, a portion of the second conductive layer A2 is a photosensitive material; In the second case, the entire area of ​​the second conductive layer A2 is composed of photosensitive material.

[0027] The second conductive layer A2 is used to scatter and refract light to form scattered light, thereby extending the transmission path of the scattered light in the substrate A3, and / or to absorb refracted light to generate photogenerated carriers. This may include, but is not limited to, the following: In the first case, the second conductive layer A2 is used to scatter and refract light and form scattered light to extend the transmission path of the scattered light in the substrate A3; In the second case, the second conductive layer A2 is used to absorb refracted light to generate photogenerated carriers; In the third case, the second conductive layer A2 is used to scatter and refract the light and form scattered light to extend the transmission path of the scattered light in the substrate A3. At the same time, the second conductive layer A2 can also be used to absorb the refracted light to generate photogenerated carriers.

[0028] The second conductive layer A2 can change the propagation direction of refracted light in multiple directions and form scattered light. The scattered light is incident into the interior of the substrate A3 at multiple angles. At the same time, when the scattered light comes into contact with the sidewall of the substrate A3, it will be refracted, further changing the propagation direction and forming a propagation path with multiple reversals, thereby realizing the secondary extension of the transmission path of the scattered light and further improving the absorption and utilization rate of photons.

[0029] The photosensitive material in the second conductive layer A2 can directly absorb the refracted light emitted through the first conductive layer A1, converting photon energy into electron-hole pairs, thus generating photogenerated carriers. The second conductive layer A2 adds a photoelectric conversion stage to the existing photoelectric conversion stage in the substrate A3, directly capturing a portion of the incident photons and completing the photoelectric conversion, significantly increasing the total number of incident photons captured by the pixel unit.

[0030] Photosensitive materials can be selected according to the target operating wavelength, including but not limited to narrow band semiconductor materials such as PbS, InAs, and Ge. These materials have high absorption coefficients in the visible to near-infrared wavelength range, enabling efficient light absorption.

[0031] Substrate A3 serves as the base support structure for the pixel unit and is also the core secondary photoelectric conversion and signal readout carrier. Substrate A3 performs secondary absorption and photoelectric conversion on refracted light that is not absorbed by the second conductive layer A2, as well as scattered light that is modulated by the second conductive layer A2, converting photogenerated carriers into image electrical signals corresponding to the incident light.

[0032] The complete working process of the pixel unit provided in this application embodiment is as follows: The incident light first enters the first conductive layer A1, and the phase and propagation angle are precisely controlled by the optical control units 3 spaced apart in the first conductive layer A1, forming refracted light whose propagation angle is precisely matched with the refractive index of the second conductive layer A2, reducing the Fresnel reflection loss of the incident light at the interlayer interface, and ensuring that the vast majority of the incident light can smoothly enter the second conductive layer A2. After the refracted light exits from the first conductive layer A1, it enters the second conductive layer A2. Part of the refracted light is directly absorbed by the photosensitive material in the second conductive layer A2, generating photogenerated carriers and completing the first-stage photoelectric conversion. The other part of the refracted light is scattered by the second conductive layer A2, forming scattered light with a randomly tilted propagation direction. This scattered light, along with the refracted light that was not absorbed by the second conductive layer A2, is incident into the interior of the substrate A3. After the scattered and refracted light enters the photoelectric conversion region of substrate A3, some photons are directly absorbed by substrate A3 and generate photogenerated carriers; the other part of the scattered light, which propagates at an angle, is incident on the sidewall of substrate A3 and undergoes refraction and total internal reflection at the interface, forming a propagation path that is folded back multiple times inside substrate A3. During the process of extending the propagation path, it is gradually absorbed by substrate A3, completing the second-level photoelectric conversion. Substrate A3 collects photogenerated carriers generated by its own photoelectric conversion, as well as photogenerated carriers generated by the second conductive layer A2, and finally converts all photogenerated carriers into image electrical signals corresponding to the incident light, completing the entire photoelectric conversion and signal readout process.

[0033] In the embodiments of this application, by setting a first conductive layer A1, a second conductive layer A2, and a substrate A3 arranged sequentially along the incident light direction, and by setting multiple spaced optical control units 3 in the first conductive layer A1, and by setting at least a portion of the second conductive layer A2 as a photosensitive material, the propagation angle of the incident light can be precisely controlled through the first conductive layer A1, generating refracted light that matches the refractive index of the second conductive layer A2. This reduces the reflection loss of the incident light at the interface between the first conductive layer A1 and the second conductive layer A2, ensuring that the vast majority of the incident light can smoothly enter the second conductive layer A2 and the substrate A3, laying the foundation for improving the utilization rate of the incident light. The photosensitive material in the second conductive layer A2 absorbs the refracted light after refraction by the second conductive layer A2 and generates photogenerated carriers, adding a first-order optical conversion layer to the original photoelectric conversion region of the substrate A3. The electro-conversion path eliminates the need for an independent optical structure in the photoelectric conversion region of substrate A3, which would otherwise encroach on the effective photosensitive area of ​​substrate A3. This increases the total absorption of incident light without sacrificing the photosensitive performance of the pixel unit. By scattering the refracted light through the second conductive layer A2, scattered light is formed, significantly extending the transmission path of the scattered light in substrate A3. This increases the contact time and interaction probability between the scattered light and the photoelectric conversion region of substrate A3, significantly improving the absorption efficiency of substrate A3 for incident light. This allows for the control of incident light from propagation to multi-level absorption. At the same time, the overall stacked structure of the first conductive layer A1, the second conductive layer A2, and substrate A3 is simple and controllable. This can improve the quantum efficiency of the pixel unit without increasing the difficulty of device integration design or only slightly increasing the complexity of the fabrication process, thereby simultaneously improving the photosensitive performance and image recognition accuracy of the image sensor.

[0034] Optionally, in a pixel unit provided in an embodiment of this application, such as Figure 1 As shown, the second conductive layer A2 is located between the first conductive layer A1 and the substrate A3. The second conductive layer A2 has a first bonding surface and a second bonding surface that are disposed opposite to each other. The first bonding surface is flush with the side of the first conductive layer A1 that is close to the substrate A3, and the second bonding surface is flush with the side of the substrate A3 that is close to the first conductive layer A1. The entire second conductive layer A2 is a photosensitive material used to absorb refracted light and generate photogenerated carriers.

[0035] The first bonding surface is the upper surface of the second conductive layer A2 facing the first conductive layer A1, and the second bonding surface is the lower surface of the second conductive layer A2 facing the substrate A3. There is no height difference or air gap between the first bonding surface and the side of the first conductive layer A1 near the substrate A3, forming a continuous and tight contact interface without cavities; similarly, there is no height difference or interface gap between the second bonding surface and the side of the substrate A3 near the first conductive layer A1, forming a seamless interlayer contact structure.

[0036] For example, such as Figure 1As shown, the entire area of ​​the second conductive layer A2 is composed of homogeneous photosensitive material, forming a continuous and complete photoelectric conversion thin film layer. By adjusting the doping concentration and film thickness of the photosensitive material, it can be adapted to the light absorption requirements across the entire visible to near-infrared wavelength range, ensuring that the second conductive layer A2 has a stable and highly linear light absorption coefficient and photoelectric conversion efficiency within the target operating wavelength range.

[0037] By setting the first bonding surface of the second conductive layer A2 to be flush with the side of the first conductive layer A1 near the substrate A3, and the second bonding surface to be flush with the side of the substrate A3 near the first conductive layer A1, and by setting the entire area of ​​the second conductive layer A2 to be photosensitive material, the following beneficial effects are achieved: Firstly, it can eliminate the bonding gaps and interface steps between the first conductive layer A1 and the second conductive layer A2, and between the second conductive layer A2 and the substrate A3. Structurally, it avoids the light energy loss caused by diffuse reflection and stray light refraction at the gaps of incident light. At the same time, it eliminates the abrupt change in interlayer refractive index caused by the interface steps, further reducing the Fresnel reflection loss of incident light at the interlayer interface. This ensures that the refracted light after being modulated by the first conductive layer A1 can enter the interior of the second conductive layer A2 without loss, laying a structural foundation for maximizing the utilization of incident photon energy.

[0038] Secondly, based on the structural design that the entire area of ​​the second conductive layer A2 is composed of photosensitive material, the refracted light can interact with the photosensitive material throughout the entire space of the second conductive layer A2, maximizing the utilization of the entire volume space of the second conductive layer A2 for photoelectric conversion. Under the same layer thickness, the capture probability of incident photons can be significantly improved.

[0039] Thirdly, the homogeneous photosensitive material thin film structure can be fabricated in a single thin film deposition process, eliminating the need for subsequent etching, multiple filling, and step-by-step deposition steps. This significantly simplifies the fabrication process of the second conductive layer A2, reduces process complexity and manufacturing costs. At the same time, the homogeneous thin film layer has a lower surface defect density, which can effectively reduce non-radiative recombination of photogenerated carriers caused by surface defects, reduce the dark current of pixel units, and improve the signal-to-noise ratio of the device.

[0040] Optionally, in a pixel unit provided in an embodiment of this application, such as Figure 2 and Figure 4 As shown, the second conductive layer A2 is embedded in the substrate A3 on the side close to the first conductive layer A1. The second conductive layer A2 includes a plurality of protrusion structures 7 arranged perpendicular to the first direction. Along the first direction, the cross-sectional width of the protrusion structure 7 gradually decreases. The protrusion structure 7 is used to absorb refracted light to generate photogenerated carriers and to scatter refracted light to generate scattered light. The first direction is the direction from the substrate A3 to the second conductive layer A2.

[0041] The second conductive layer A2 is embedded in the substrate A3 on the side close to the first conductive layer A1. This means that the second conductive layer A2 is not a stacked structure formed independently of the substrate A3 by surface bonding, but is integrated into the substrate A3 on the side close to the first conductive layer A1 in an embedded configuration. The core functional structure of the second conductive layer A2 and the substrate A3 form an integrated design with continuous physical structure, homogeneous material system, and synchronized fabrication process. The two are not a simple splicing of two independent functional layers, but together constitute an integrated composite semiconductor structure. The two have no independent layer interface and no bonding gap.

[0042] For example, the protrusion structure 7 can take the form of a frustum, a pyramid, a nano-dendritic structure, a cone, etc. For example, the protrusion structure 7 can be a long strip prism structure or a ring prism structure.

[0043] When the protrusion structure 7 is a long strip prism, multiple protrusion structures 7 can be arranged in a periodic parallel array along the direction perpendicular to the first direction; when the protrusion structure 7 is a ring prism, the protrusion structures 7 can be arranged in a concentric ring with the central axis of the pixel unit as the center.

[0044] It should be noted that, along the first direction, in a local area of ​​the protruding structure 7, the cross-sectional width may exhibit a discontinuous gradual change pattern with a slight increase in stages. That is, the overall structure follows a gradual change pattern of being narrower at the top and wider at the bottom, while a sudden increase in width may occur locally.

[0045] The material selection for the protrusion structure 7 can be the same as the photosensitive material in the aforementioned embodiments, such as PbS, InAs, Ge, etc.; or it can be a silicon-based photosensitive material that is the same as the active part 5 of the substrate A3. It can be formed in one step by ICP (Inductively Coupled Plasma) maskless etching process, without the need for an additional photolithography mask. The preset cross-sectional gradient morphology can be achieved simply by adjusting the etching process parameters.

[0046] The working process when the second conductive layer A2 includes the protrusion structure 7 is as follows: After the refracted light emitted from the first conductive layer A1 is incident on the second conductive layer A2, it first irradiates the arrayed protrusion structure 7; multiple refractions and diffuse scattering occur at the sidewalls of the protrusion structure 7, forming large-angle scattered light with randomly tilted propagation direction; throughout the transmission process of the refracted and scattered light inside the protrusion structure 7, it is continuously absorbed by the photosensitive material constituting the protrusion structure 7, completing photoelectric conversion and generating photogenerated carriers; the scattered light and transmitted light that are not absorbed by the protrusion structure 7 are emitted to the substrate A3 through the bottom end of the protrusion structure 7.

[0047] In the embodiments of this application, by providing the second conductive layer A2 with a plurality of protrusions 7 arranged perpendicular to the first direction, and designing the protrusions 7 such that the cross-sectional area near the first conductive layer A1 is smaller than the cross-sectional area near the substrate A3, the following advantages are achieved: Firstly, on any horizontal cross-section perpendicular to the first direction, the cross-sectional area of ​​the protrusion structure 7 near the first conductive layer A1 is smaller than the cross-sectional area near the substrate A3, making the fill factor of the protrusion structure 7 near the first conductive layer A1 smaller than the fill factor near the substrate A3. This results in an effective refractive index that gradually increases from the side of the protrusion structure 7 near the first conductive layer A1 to the side near the substrate A3, allowing the incident light to form a continuous refractive index gradient transition on the surface of the protrusion structure 7, achieving an anti-reflection effect on the incident light. This eliminates the need to deposit an additional anti-reflection film layer on the surface of the pixel unit, reducing the complexity of the device fabrication process and manufacturing cost.

[0048] Secondly, the material in the protrusion structure 7 can directly absorb the incident refracted light, convert photon energy into electron-hole pairs, generate photogenerated carriers, and complete the first-stage photoelectric conversion. At the same time, the gradient cross-sectional morphology and arrayed arrangement of the protrusion structure 7 can produce multi-angle and wide-range scattering of the incident refracted light, causing the propagation direction of the refracted light to be randomly deflected, forming scattered light that diverges into the entire space. The scattered light incident on the substrate A3 can significantly improve the light transmission path in the substrate A3, increase the probability of interaction between photons and the photoelectric conversion region of the substrate A3, and improve the utilization rate of the incident light.

[0049] Optionally, in a pixel unit provided in an embodiment of this application, such as Figure 2 and Figure 4 As shown, the second conductive layer A2 also includes a first filling layer 4; the first filling layer 4 covers a plurality of protrusion structures 7; and along the first direction, the cross-sectional width of the first filling layer 4 gradually increases; the side of the first filling layer 4 near the first conductive layer A1 is flush with the side of the first conductive layer A1 near the substrate A3.

[0050] It should be noted that, along the first direction, in a local area of ​​the first filling layer 4, the cross-sectional width may exhibit a discontinuous gradual change pattern with a slight increase in stages. That is, the overall structure follows a gradual change pattern of being wider at the top and narrower at the bottom, while a sudden increase in width may occur locally.

[0051] For example, the first filling layer 4 can be made of a transparent medium material, such as inorganic medium materials like silica or alumina, or organic polymer transparent medium materials like SU-8 or polyimide.

[0052] In the embodiments of this application, the second conductive layer A2 further includes a first filling layer 4 covering multiple protrusion structures 7. The first filling layer 4 is designed such that its cross-sectional area near the first conductive layer A1 is larger than its cross-sectional area near the substrate A3, which has the following advantages: Firstly, the first filling layer 4 and the protruding structure 7 form a complementary space-filling structure, which can fill the undulating surface of the array of protruding structures 7 into a flat upper surface, so that a continuous and flat interface is formed between the second conductive layer A2 and the first conductive layer A1, eliminating the interface steps and air gaps caused by the array of protruding structures 7. This can avoid the light energy loss caused by diffuse reflection and stray light deflection at the interface steps of the incident light, further reduce the interface coupling loss of the incident light from the first conductive layer A1 to the second conductive layer A2, and ensure that more incident photons can enter the interior of the second conductive layer A2 to participate in photoelectric conversion, laying the foundation for improving quantum efficiency.

[0053] Secondly, the top-wide and bottom-narrow configuration of the first filling layer 4 forms a precise complementary match with the top-narrow and bottom-wide configuration of the protruding structure 7. This allows the filling factor of the protruding structure 7 to continuously increase from top to bottom while the filling factor of the first filling layer 4 synchronously and continuously decreases from top to bottom. After the two are combined, the overall effective refractive index of the second conductive layer A2 can form a continuous and linear smooth gradient change along the direction of incident light propagation, eliminating the abrupt refractive index change points inside the composite structure. This further enhances the broadband anti-reflection effect of the second conductive layer A2 and improves the coupling efficiency of incident light. At the same time, the continuous refractive index gradient can prevent light from being reflected back inside the structure, further reducing internal light energy loss.

[0054] Optionally, in a pixel unit provided in an embodiment of this application, such as Figure 1 , Figure 2 and Figure 4 As shown, the first conductive layer A1 also includes a second filling layer 2; the second filling layer 2 and the optical control unit 3 are alternately arranged in a direction perpendicular to the first direction.

[0055] For example, the second filling layer 2 can be made of a transparent medium material, such as inorganic transparent medium materials like silica, alumina, and magnesium fluoride, or organic polymer transparent medium materials like SU-8 and polyimide.

[0056] The second filling layer 2 and the optical control unit 3 are alternately arranged in a direction perpendicular to the first direction, which means that the second filling layer 2 and the optical control unit 3 are arranged in the same layer, and two adjacent optical control units 3 are separated by the second filling layer 2, and their orthogonal projections on the substrate A3 do not overlap.

[0057] In the embodiments of this application, by providing the first conductive layer A1, a second filling layer 2 is also included, and the second filling layer 2 and the optical control unit 3 are alternately arranged in a direction perpendicular to the first direction, which has the following beneficial effects: Firstly, the second filling layer 2 can fill the gap between adjacent optical control units 3, eliminating the air cavity between the optical control units 3. Structurally, it avoids light energy loss caused by diffuse reflection and stray light diffraction of incident light at the air gap. At the same time, it enables the first conductive layer A1 to form an integrated film structure with double flat surfaces on the upper and lower sides, which can form a continuous interface that is flush with and fits the upper lens 1 and the lower second conductive layer A2. This further reduces Fresnel reflection loss of incident light at the interlayer interface, ensuring that more incident light can enter the optical control unit 3 to complete the propagation angle control. This lays the structural foundation for accurately achieving the refractive index matching between the refracted light and the second conductive layer A2.

[0058] Secondly, the alternating arrangement of the second filling layer 2 and the optical control unit 3 allows for flexible adjustment of the overall equivalent refractive index of the first conductive layer A1 by adjusting the dielectric constant and filling width of the second filling layer 2. This creates a more precise gradient match with the refractive index of the second conductive layer A2, further reducing interface reflection loss when incident light exits from the first conductive layer A1 to the second conductive layer A2. This ensures that more photons can enter the second conductive layer A2 and the substrate A3 to participate in photoelectric conversion, ultimately achieving a simultaneous improvement in the wide-band quantum efficiency and imaging sensitivity of the pixel unit.

[0059] Optionally, in a pixel unit provided in an embodiment of this application, such as Figure 3 As shown, the second conductive layer A2 also includes a plurality of photoelectric conversion units 12; the photoelectric conversion units 12 are located on the surface of the protrusion structure 7 and are used to absorb refracted light and generate photogenerated carriers.

[0060] The photoelectric conversion unit 12 can be disposed between the protruding structure 7 and the first filling layer 4. Part of the surface of the photoelectric conversion unit 12 is in contact with the surface of the protruding structure 7, and another part of the surface is in direct contact with the first filling layer 4. The first filling layer 4 covers all the photoelectric conversion units 12 and fills the gaps between adjacent photoelectric conversion units 12, so that the photoelectric conversion unit 12 is stably confined in the interface area between the protruding structure 7 and the first filling layer 4, without the risk of displacement or falling off.

[0061] When the second conductive layer A2 includes a passivation layer 13, the photoelectric conversion unit 12 can be disposed between the passivation layer 13 and the first filling layer 4.

[0062] For example, the photoelectric conversion unit 12 can be a semiconductor quantum dot; Semiconductor quantum dots are semiconductor nanocrystals with dimensions of only a few nanometers (typically 2–20 nanometers), composed of hundreds to thousands of atoms. When the size of a semiconductor shrinks to the nanometer scale, a quantum confinement effect occurs—its band structure changes from continuous bands to discrete energy levels, and the band gap increases as the crystal size decreases. Because the band gap is tunable, quantum dots can cover wavelengths from visible light to short-wave infrared and even mid-wave infrared.

[0063] The photosensitive material of the photoelectric conversion unit 12 can be consistent with the material of the protruding structure 7, or it can be a photosensitive material that is complementary to the absorption band of the protruding structure 7. As a preferred option in this embodiment, the photoelectric conversion unit 12 is selected from quantum dot materials with high absorption coefficients in the near-infrared long-wave band, which complements the light absorption band of the protruding structure 7 and broadens the spectral response range of the pixel unit.

[0064] For example, the material of the photoelectric conversion unit 12 can be a photosensitive material, such as PbS, InAs, CdSe, etc.

[0065] For example, the photoelectric conversion unit 12 may be at least one of spherical, conical, pyramidal, and cubic shapes.

[0066] In the embodiments of this application, the photoelectric conversion unit 12 is disposed on the surface of the protruding structure 7, and the photoelectric conversion unit 12 is defined to absorb refracted light and generate photogenerated carriers, which has the following beneficial effects: Firstly, the incident light can pass through the light absorption of the photoelectric conversion unit 12 before entering the protrusion structure 7. Based on the original photoelectric conversion path of the protrusion structure 7 in the above embodiment, an independent photoelectric conversion stage is added, which can form a multi-stage continuous photoelectric conversion structure in the second conductive layer A2, greatly increasing the total amount of incident photons captured, reducing photon loss, and improving the photoelectric conversion efficiency of the second conductive layer A2.

[0067] Secondly, the photoelectric conversion unit 12 will not encroach on the effective photosensitive area of ​​the pixel unit, nor will it interfere with the function of the first conductive layer A1 in controlling the propagation angle of the incident light. Without sacrificing the core performance of the original structure, it can further improve the quantum efficiency.

[0068] Thirdly, the material of the photoelectric conversion unit 12 can be selected to be a photosensitive material that complements the absorption band of the protrusion structure 7. It can specifically absorb photons in the band with low response efficiency of the protrusion structure 7 (e.g., near-infrared long-wave photons with insufficient response of silicon-based materials), forming a perfect complement to the light absorption band of the protrusion structure 7. Without adjusting the doping process of the substrate A3, the spectral response range of the pixel unit can be greatly broadened, achieving high response across the entire visible to near-infrared band, and adapting to the wide-band operation requirements of the spectral image sensor.

[0069] Optionally, in a pixel unit provided in an embodiment of this application, such as Figure 3 As shown, the second conductive layer A2 also includes a passivation layer 13; the passivation layer 13 is located on the surface of the protrusion structure 7 and is used to reduce defects on the surface of the protrusion structure 7 in order to reduce the dark current on the surface of the protrusion structure 7.

[0070] The passivation layer 13 is a continuous and dense dielectric thin film layer that covers the outer surface of the protruding structure 7. The outer surface of the protruding structure 7 includes the top and sidewalls of the protruding structure 7. One side of the passivation layer 13 forms a tight fit with the surface of the protruding structure 7 without gaps or cavities, and the other side forms a continuous fit contact interface with the first filling layer 4, filling the entire interface area between the first filling layer 4 and the protruding structure 7 without interface steps or gaps.

[0071] The passivation layer 13 can be prepared using a dielectric material with high density and low interface state density, including but not limited to inorganic dielectric materials such as alumina, silicon dioxide, and silicon nitride. As a preferred embodiment, the passivation layer 13 can be prepared using an atomic layer deposition process, which can fill the micro-nano-level defects and pores on the surface of the protrusion structure 7.

[0072] In the embodiments of this application, by disposing the passivation layer 13 on the surface of the protrusion structure 7, the passivation layer 13 can be used to fill the micro-nano-level defect pores on the surface of the protrusion structure 7, specifically acting on the surface defect sites of the protrusion structure 7, thereby effectively passivating the dangling bonds and lattice defects on the surface of the protrusion structure 7 and reducing the surface defect state density of the protrusion structure 7. Based on the reduction of the surface defect state density, the non-radiative recombination of photogenerated carriers on the surface of the protrusion structure 7 can be significantly suppressed, reducing the leakage current caused by surface defects and reducing the dark current generated on the surface of the protrusion structure 7 from the root. In addition, the passivation layer 13 can form a physical encapsulation and isolation for the protrusion structure 7, preventing the material of the first filling layer 4 from causing contamination and erosion to the surface of the protrusion structure 7 during the preparation process, ensuring the integrity of the surface of the protrusion structure 7, further reducing the generation of surface defects, and continuously maintaining the performance of low dark current.

[0073] Optionally, in a pixel unit provided in an embodiment of this application, the dielectric constant of the first filling layer 4 is less than the dielectric constant of the protrusion structure 7.

[0074] It should be noted that the dielectric constant mentioned in the embodiments of this application specifically refers to the relative dielectric constant of the target pixel unit in the working band (e.g., visible to near-infrared band, 400nm~1700nm), rather than the dielectric constant in the low-frequency or DC state.

[0075] The first filling layer 4 can be fabricated using a transparent material with a low dielectric constant, while the protruding structure 7 can be fabricated using a photosensitive semiconductor material with a high dielectric constant. The range of the dielectric constant difference can be adapted and adjusted according to the target operating wavelength of the pixel unit. According to the dielectric confinement principle of dielectric optics, when light from the low dielectric constant (low refractive index) first filling layer 4 is incident on the high dielectric constant (high refractive index) protruding structure 7, the electromagnetic field energy of the light field will spontaneously converge towards the high dielectric constant region. The larger the dielectric constant difference, the stronger the local confinement ability of the light field, and the higher the proportion of light field energy confined inside the protruding structure 7. A large dielectric constant difference can significantly enhance the confinement ability of long-wavelength diverging light fields, thereby increasing the light field energy confined inside the protruding structure 7, greatly increasing the probability and duration of interaction between photons and photosensitive materials, and solving the defect of insufficient absorption efficiency of silicon-based materials for near-infrared long-wavelength light.

[0076] In the embodiments of this application, by limiting the dielectric constant of the first filling layer 4 to be less than the dielectric constant of the protrusion structure 7, the following advantages are achieved: Firstly, the incident light energy is firmly localized within the protruding structure 7, which serves as the photosensitive host. This significantly increases the interaction time and probability between photons and the photosensitive material, allowing more photons to be absorbed and converted into photogenerated carriers. This improves the photoelectric conversion efficiency of the second conductive layer A2. Especially for near-infrared long-wave photons, whose light fields are naturally prone to divergence, the high-low matching design of the first filling layer 4 and the protruding structure 7 can effectively confine the long-wave light field, solving the defect of insufficient absorption efficiency of silicon-based materials for near-infrared long waves in traditional structures and significantly broadening the spectral response range of the pixel unit.

[0077] Secondly, when light from the low-dielectric-constant first filling layer 4 is incident on the high-dielectric-constant protruding structure 7, according to the geometrical optics refraction law, the light is deflected towards the normal direction at the interface, causing the light to converge into the interior of the protruding structure 7. Simultaneously, the protruding structure 7 has a gradient sidewall morphology with a gradually increasing cross-sectional area from top to bottom. This sidewall causes continuous, multi-angle directional deflection of the propagating light, forming a large number of large-angle scattered light beams. When these large-angle scattered light beams are incident on the lower substrate A3, their effective transmission path length is significantly increased. Furthermore, when the scattered light reaches the sidewall of substrate A3, refraction and total internal reflection occur, causing the light path to refract multiple times within substrate A3, achieving multi-stage extension of the optical path. This mechanism allows photons to pass more fully through the photoelectric conversion region of substrate A3, significantly improving the absorption probability of incident photons by substrate A3, especially compensating for the low absorption coefficient of silicon-based materials for near-infrared long-wavelength photons, thereby achieving a simultaneous improvement in the quantum efficiency of pixel units across the entire visible to near-infrared wavelength range.

[0078] Optionally, in a pixel unit provided in an embodiment of this application, the dielectric constant of the second filling layer 2 is less than the dielectric constant of the optical control unit 3.

[0079] The second filling layer 2 is made of a transparent dielectric material with low dielectric constant and low light absorption loss in the visible-near infrared band, while the optical control unit 3 is made of a micro-nano optical dielectric material with a relatively higher dielectric constant and low light loss in the visible-near infrared band.

[0080] For example, the material of the second filling layer 2 can be a low dielectric constant inorganic transparent medium such as silicon dioxide, alumina, or magnesium fluoride, or a low dielectric constant organic polymer transparent medium such as SU-8 or polyimide.

[0081] For example, the material of the optical control unit 3 can be a transparent insulating dielectric material with low light absorption loss. For example, the material of the optical control unit 3 can be silicon nitride, amorphous silicon, titanium dioxide, gallium nitride, etc.

[0082] The above materials are all conventional materials used in the manufacturing process of CMOS (Complementary Metal-Oxide-Semiconductor) image sensors. They can be prepared by conventional semiconductor processes such as chemical vapor deposition, are fully compatible with existing wafer manufacturing lines, do not require additional special process equipment, and can effectively control the manufacturing cost and process complexity of the devices.

[0083] In the embodiments of this application, by limiting the dielectric constant of the second filling layer 2 to be lower than that of the optical control unit 3, the propagation angle of the incident light can be precisely controlled. The core function of the optical control unit 3 is to adjust the propagation direction of the incident light, allowing the light to enter the lower structure at the optimal angle. Its control effect is highly dependent on the difference in dielectric constant between the second filling layer 2 and the optical control unit 3. The lower dielectric constant of the second filling layer 2 can form a clear parameter match with the optical control unit 3, effectively improving its phase modulation depth and propagation angle control accuracy of the incident light. This ensures that the first conductive layer A1 can stably generate refracted light with a refractive index that precisely matches that of the second conductive layer A2, reducing Fresnel reflection loss of the incident light at the interface between the first conductive layer A1 and the second conductive layer A2, retaining more photon energy for subsequent photoelectric conversion, and laying the foundation for improved quantum efficiency.

[0084] Optionally, such as Figure 4As shown, in a pixel unit provided in an embodiment of this application, substrate A3 includes a first surface, a first doped portion 6, a second doped portion 8, an active portion 5, and an isolation portion 9; the first surface is the interface between substrate A3 and the second conductive layer A2; the first doped portion 6 is located on the side of the first surface away from the second conductive layer A2, and is used to suppress the recombination of photogenerated carriers at defects on the first surface to reduce the dark current of the pixel unit; the second doped portion 8 is disposed on the side of the first doped portion 6 away from the second conductive layer A2, and the second doped portion 8 is spaced apart from the first doped portion 6; the active portion 5 covers a portion of the first doped portion 6 and the second doped portion 8; the isolation portion 9 extends from the first surface into the interior of the active portion 5; the material of the protrusion structure 7 in the second conductive layer A2 is the same as the material of the active portion 5, or the material of the protrusion structure 7 is the same as the material of the photoelectric conversion unit 12 in the second conductive layer A2.

[0085] For example, the first doped portion 6 can be heavily p-type doped.

[0086] High concentrations of homotype heavy doping create strong band bending at the interface between the first doped portion 6 and the active portion 5, generating a built-in electric field pointing inwards from the active portion 5. This electric field effectively repels photogenerated minority carriers (e.g., photogenerated electrons are minority carriers in the P-type active portion 5), preventing them from drifting to the defect-rich first surface. This suppresses nonradiative recombination of photogenerated carriers at the defect sites on the first surface, thereby suppressing leakage current and dark current caused by surface defects.

[0087] For example, the second doped portion 8 can be an N-type heavily doped portion, and the active portion 5 can be a P-type doped portion.

[0088] The second doped portion 8 and the first doped portion 6 are separated by a portion of the active portion 5. The second doped portion 8 and the active portion 5 together constitute the core photoelectric conversion PN junction inside the substrate A3. Specifically, the depletion region of this PN junction is mainly located near the contact interface between the second doped portion 8 and the active portion 5, and its built-in electric field direction is from the active portion 5 to the second doped portion 8. When the active portion 5 is P-type doped and the second doped portion 8 is heavily N-type doped, under the action of this built-in electric field, photogenerated minority carriers (electrons) are accelerated and swept into the second doped portion 8, while photogenerated majority carriers (holes) are pushed to the bottom of the active portion 5. When incident light (including refracted light not absorbed by the second conductive layer A2 and scattered light modulated by the second conductive layer A2) enters the active portion 5, photons are absorbed by the semiconductor material of the active portion 5 and excited to generate electron-hole pairs. Under the influence of the built-in electric field of the PN junction, photogenerated electrons rapidly drift towards and accumulate in the second doped portion 8, while photogenerated holes drift away from the second doped portion 8 and are eventually drawn out through the conductive layer 11 at the bottom of the substrate A3. The photogenerated electrons accumulated in the second doped portion 8 are also collected through this conductive layer 11, thereby forming an image electrical signal corresponding to the incident light intensity.

[0089] For example, the isolation section 9 may be filled with an insulating barrier material, such as silicon dioxide, silicon nitride, etc.

[0090] The isolation section 9 can block the leakage current path between the active sections 5 of adjacent pixels, preventing the lateral diffusion of photogenerated carriers between adjacent pixels. At the same time, it can perform total internal reflection of large-angle scattered light incident on the isolation section 9, extending the transmission path of photons within the active section 5 of this pixel. While improving photon absorption efficiency, it reduces optical crosstalk and ensures the independence and accuracy of the imaging signal of each pixel unit in the pixel array.

[0091] In the embodiments of this application, when the material of the protrusion structure 7 is the same as that of the active part 5, it can be integrally formed on the surface of the substrate A3 by etching process, without the need for additional thin film deposition, material transfer wafer bonding and other processes. This can eliminate the heterojunction interface between the protrusion structure 7 and the substrate A3, reduce interface defects and contact resistance, and at the same time greatly simplify the fabrication process, improve the process yield and production efficiency of the device.

[0092] When the material of the protrusion structure 7 is the same as that of the photoelectric conversion unit 12 in the second conductive layer A2, the protrusion structure 7 can flexibly select a narrow band semiconductor material or a semiconductor quantum dot material that is consistent with the photoelectric conversion unit 12 according to the light absorption requirements of the target working band. It can form a complementary match with the photoelectric conversion unit 12 in the light absorption band, achieve efficient light absorption in the near-infrared long-wave band where the response efficiency of silicon-based materials is low, greatly broaden the spectral response range of the pixel unit, and adapt to the core application requirements of wide-band spectral image sensors.

[0093] Optionally, in a pixel unit provided in an embodiment of this application, such as Figure 1 , Figure 2 and Figure 4 As shown, the pixel unit also includes an insulating portion 10, a conductive layer 11, and a lens 1. The substrate A3 includes a second surface disposed opposite to the first surface. The insulating portion 10 is disposed on the side of the second surface away from the second conductive layer A2. The conductive layer 11 is disposed inside the insulating portion 10 and is used to export photogenerated carriers as image signals. The lens 1 is disposed on the side of the first conductive layer A1 away from the substrate A3 and is used to focus incident light onto the first conductive layer A1.

[0094] For example, the material of the insulating part 10 can be an inorganic insulating material or an organic insulating material. For instance, the material of the insulating part 10 can be an inorganic insulating material such as silicon dioxide or silicon nitride, or an organic insulating material such as polyimide or benzocyclobutene.

[0095] The insulating part 10 can achieve all-round electrical isolation between the conductive layer 11 and the active region, first doped region, second doped region and other semiconductor functional areas inside the substrate A3, avoiding problems such as signal crosstalk, leakage current and dark current rise; at the same time, it can isolate external moisture, impurity ions and pollutants from the erosion and contamination of the semiconductor area of ​​the substrate A3, and improve the working stability and long-term reliability of the pixel unit in the high temperature, high humidity and complex electromagnetic environment of the vehicle.

[0096] The conductive layer 11 is embedded inside the insulating portion 10. Its material can be a metal, such as copper, aluminum, titanium, or a composite metal, forming a conductive electrode structure corresponding to each pixel unit and establishing an ohmic contact with the second doped region inside the substrate A3. The conductive layer 11 is used to extract the photogenerated carriers generated and efficiently collected by photoelectric conversion in the substrate A3 and the second conductive layer A2 into a standard image electrical signal, which is then transmitted to the subsequent signal processing circuit. This avoids problems such as signal attenuation, distortion, and delay during transmission, effectively improving the sensor's imaging frame rate, signal reading accuracy, and response speed.

[0097] Lens 1 is made of a material with high transmittance and low dispersion, such as fused silica or silicon nitride. Lens 1 can efficiently converge and collimate a wide range of divergent light rays and obliquely incident light rays from the outside, and concentrate the edge light rays that would otherwise be scattered and lost to the optical control unit 3 area of ​​the first conductive layer A1, which greatly improves the effective light-receiving area and incident light utilization of the pixel unit, and can significantly improve the photosensitivity of the image sensor.

[0098] In summary, this embodiment, through the integrated design of the insulating part 10, the conductive layer 11, and the lens 1, fully covers the entire workflow from incident light convergence, wide-band photoelectric conversion, stable electrical signal output to long-term device protection. Without reducing the photosensitive area or increasing the process complexity, it simultaneously optimizes the optical performance, electrical performance, environmental adaptability, and long-term reliability of the pixel unit, making the device perfectly suited to the application requirements of high performance, high reliability, and large-scale array integration of automotive wide-band spectral image sensors.

[0099] The embodiments of this application provide a method for fabricating pixel units, applicable to fabricating pixel units as described in any of the preceding embodiments, such as... Figure 5 As shown, the method includes: S101, Provide substrate; For example, such as Figure 6 As shown, the substrate can be made of silicon. The first doped region in the substrate can be formed into a heavily p-type doped region through ion implantation. The second doped region in the substrate can be formed into a heavily n-type doped region through ion implantation. The active region in the substrate can be formed into a p-type doped region through ion implantation and annealing.

[0100] For example, such as Figure 7 As shown, the isolation portion in the substrate can be formed by etching and deposition processes. Etching processes can include photolithography or inductively coupled plasma etching; deposition processes can include chemical vapor deposition (CVD) or physical vapor deposition (PVD).

[0101] For example, the material of the isolation portion in the substrate can be an insulating dielectric material such as silicon dioxide or silicon nitride.

[0102] For example, such as Figure 8 As shown, the insulating part and the conductive layer can be formed by thin film deposition, patterning process and bonding process.

[0103] S102, such as Figures 9-11 As shown, a second conductive layer is formed, which is in contact with the side of the first conductive layer near the substrate. At least a portion of the second conductive layer is a photosensitive material used to scatter and refract light and form scattered light, and / or absorb refracted light. For example, the second conductive layer can be prepared by a semiconductor thin film deposition process.

[0104] Thin film deposition processes may include at least one of chemical vapor deposition, physical vapor deposition, atomic layer deposition, and solution spin coating.

[0105] Based on the structural design of the second conductive layer, patterning etching and surface passivation processes can be used to complete the refined fabrication of the second conductive layer. The patterning etching process can employ at least one of inductively coupled plasma etching and reactive ion etching, while the surface passivation process can employ at least one of atomic layer deposition and thermal oxidation.

[0106] S103. Form a first conductive layer. The first conductive layer is located on the side of the second conductive layer away from the substrate. The first conductive layer includes a plurality of spaced optical control units. The plurality of spaced optical control units are used to change the propagation angle of incident light of different wavelengths and form refracted light so that the propagation angle of the refracted light matches the refractive index of the second conductive layer and reduces the interface reflection loss of the incident light.

[0107] For example, such as Figure 12 As shown, the optical control unit can be fabricated using thin film deposition and patterning processes.

[0108] Thin film deposition processes may include at least one of physical vapor deposition, chemical vapor deposition, and atomic layer deposition processes, for depositing high dielectric constant dielectric materials for optical control units; Patterning processes may include at least one of electron beam lithography, inductively coupled plasma etching, and ultraviolet lithography.

[0109] For example, such as Figure 13 As shown, the second filling layer in the first conductive layer can be prepared by a thin film deposition process.

[0110] The pixel unit fabrication method provided in this application is fully compatible with the standard semiconductor manufacturing process of existing CMOS image sensors. The steps are simple and controllable, requiring no additional special process equipment, which can effectively reduce the manufacturing cost and process control difficulty of the device. At the same time, the substrate, second conductive layer and first conductive layer stacked structure formed by this method can precisely control the propagation angle of incident light of different wavelengths through the optical control unit spaced apart in the first conductive layer, generating refracted light that matches the refractive index of the second conductive layer. This effectively reduces the reflection loss of incident light at the interlayer interface and greatly improves the overall utilization rate of incident light. Furthermore, the photosensitive material of the second conductive layer can scatter the refracted light to extend the transmission path of the scattered light in the substrate, and / or directly absorb the refracted light to generate photogenerated carriers. Without sacrificing the effective photosensitive area of ​​the substrate or increasing the structural complexity of the device, the photoelectric conversion efficiency and quantum efficiency of the pixel unit can be effectively improved, and pixel units adapted to the application requirements of wide-band spectral image sensors can be stably fabricated.

[0111] Optionally, in a pixel unit fabrication method provided in an embodiment of this application, step S102 above includes sub-steps S1021 to S1025.

[0112] Sub-step S1021, such as Figure 9 As shown, a light-absorbing layer is deposited and formed, located on the side of the substrate close to the first conductive layer.

[0113] For example, the light-absorbing layer can be prepared by a thin-film deposition process.

[0114] The thin film deposition process can be at least one of chemical vapor deposition, physical vapor deposition, and molecular beam epitaxy. The material of the light absorption layer can be selected according to the target operating wavelength. It can be silicon-based semiconductor materials such as single crystal silicon and polycrystalline silicon, or narrow bandgap semiconductor materials such as PbS, InAs, and Ge, to match the light absorption requirements of the visible to near-infrared wide band. During the deposition process, the film thickness, density, and crystal quality of the light absorption layer can be controlled by adjusting process parameters such as deposition temperature, gas flow rate, and sputtering power.

[0115] Sub-step S1022, such as Figure 10 As shown, the light-absorbing layer is etched to form a raised structure.

[0116] For example, the light-absorbing layer can be patterned by an etching process.

[0117] The etching process can be at least one of inductively coupled plasma etching or reactive ion etching. During the etching process, the sidewall morphology of the protrusion structure is controlled by dynamically adjusting the process parameters so that the cross-sectional area of ​​the protrusion structure near the first conductive layer is smaller than the cross-sectional area near the substrate.

[0118] Sub-step S1023: Deposit to form a passivation layer, the passivation layer being located on the side of the protrusion structure away from the substrate; For example, a passivation layer can be prepared on the surface of the protrusion structure away from the substrate by a thin film deposition process.

[0119] Thin film deposition processes can be either atomic layer deposition (ALD) or chemical vapor deposition (CVD). For example, the passivation layer can be made of dielectric materials with high density and low interface state density, such as alumina, silicon dioxide, and silicon nitride.

[0120] Sub-step S1024: Deposit to form a photoelectric conversion unit, the photoelectric conversion unit being located on the side of the passivation layer away from the substrate; For example, the photoelectric conversion unit can be fabricated using at least one of solution spin coating, chemical vapor deposition, and molecular beam epitaxy.

[0121] The material of the photoelectric conversion unit can be matched with the corresponding composition according to the target absorption band, which complements the light absorption band of the protruding structure. During the preparation process, the film thickness and uniformity of the photoelectric conversion unit can be controlled by adjusting the core process parameters to ensure that it forms a close contact interface with the surface of the passivation layer.

[0122] Sub-step S1025, such as Figure 11 As shown, a first filler layer is deposited to form the first filler layer, which is located on the side of the photoelectric conversion unit away from the substrate.

[0123] For example, the first filling layer can be formed by a deposition process; The deposition process can be at least one of chemical vapor deposition, physical vapor deposition, or atomic layer deposition.

[0124] The material for the first filling layer can be a transparent dielectric material with a low dielectric constant, such as silicon dioxide, aluminum oxide, magnesium fluoride, etc.

[0125] For example, after deposition is completed, a planarization process can be used to planarize the surface of the first filling layer away from the substrate to form a flat surface, providing an interface basis for the subsequent preparation of the first conductive layer.

[0126] An image sensor is provided in the embodiments of this application, such as... Figure 14 As shown, it includes the pixel unit as described in any of the previous embodiments, and can achieve the same technical effect as the pixel unit in the foregoing embodiments. To avoid repetition, it will not be described again here.

[0127] The image sensor can include various types such as back-illuminated CMOS image sensor, stacked CMOS image sensor, global shutter CMOS image sensor, and wideband / multispectral CMOS image sensor, and can be widely adapted to application scenarios with high requirements for imaging accuracy, low light performance and environmental adaptability, such as intelligent driving visual perception and industrial inspection.

[0128] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A pixel unit, characterized in that, include: First conductive layer (A1) and absorbent layer (B1); The first conductive layer (A1) is located on one side of the absorption layer (B1). The first conductive layer (A1) includes a plurality of spaced optical control units (3). The plurality of spaced optical control units (3) are used to change the exit angle of the incident light and form refracted light so that the incident angle of the refracted light matches the refractive index of the absorption layer (B1). A portion of the absorption layer (B1) is a photosensitive material used to scatter and absorb the refracted light to generate an electrical signal, thereby forming an image electrical signal corresponding to the incident light.

2. The pixel unit according to claim 1, characterized in that, The absorption layer (B1) includes a second conductive layer (A2) and a substrate (A3). The second conductive layer (A2) is located between the first conductive layer (A1) and the substrate (A3). The second conductive layer (A2) has a first bonding surface and a second bonding surface disposed opposite to each other. The first bonding surface is flush with the side of the first conductive layer (A1) near the substrate (A3), the second bonding surface is flush with the side of the substrate (A3) near the first conductive layer (A1), and the entire second conductive layer (A2) is a photosensitive material used to absorb the refracted light and generate photogenerated carriers.

3. The pixel unit according to claim 1, characterized in that, The absorption layer (B1) includes a second conductive layer (A2) and a substrate (A3). The second conductive layer (A2) is embedded in the substrate (A3) on the side close to the first conductive layer (A1). The second conductive layer (A2) includes a plurality of protrusions (7) arranged perpendicular to the first direction. Along the first direction, the cross-sectional width of the protrusion structure (7) gradually decreases. The protrusion structure (7) is used to absorb the refracted light to generate photogenerated carriers and to scatter the refracted light to generate scattered light. Wherein, the first direction is the direction from which the substrate (A3) points to the second conductive layer (A2).

4. The pixel unit according to claim 3, characterized in that, The second conductive layer (A2) also includes a first filling layer (4); The first filling layer (4) covers the plurality of protruding structures (7); and along the first direction, the cross-sectional width of the first filling layer (4) gradually increases; The side of the first filling layer (4) near the first conductive layer (A1) is flush with the side of the first conductive layer (A1) near the substrate (A3).

5. The pixel unit according to claim 1, characterized in that, The first conductive layer (A1) further includes a second filling layer (2); The second filling layer (2) and the optical control unit (3) are alternately arranged in a direction perpendicular to the first direction.

6. The pixel unit according to claim 3, characterized in that, The second conductive layer (A2) also includes multiple photoelectric conversion units (12); The photoelectric conversion unit (12) is located on the surface of the protruding structure (7) and is used to absorb the refracted light and generate the photogenerated carriers.

7. The pixel unit according to claim 3, characterized in that, The second conductive layer (A2) also includes a passivation layer (13); The passivation layer (13) is located on the surface of the protrusion structure (7) to reduce defects on the surface of the protrusion structure (7) and thus reduce dark current on the surface of the protrusion structure (7).

8. The pixel unit according to claim 4, characterized in that, The dielectric constant of the first filling layer (4) is less than the dielectric constant of the protrusion structure (7).

9. The pixel unit according to claim 5, characterized in that, The dielectric constant of the second filling layer (2) is less than the dielectric constant of the optical control unit (3).

10. The pixel unit according to claim 1, characterized in that, The optical control unit (3) is made of a transparent insulating material.

11. The pixel unit according to claim 2 or 3, characterized in that, The substrate (A3) includes a first surface, a first doped portion (6), a second doped portion (8), an active portion (5), and an isolation portion (9); the first surface is the interface where the substrate (A3) and the second conductive layer (A2) are in contact; The first doped portion (6) is located on the side of the first surface away from the second conductive layer (A2) to suppress the recombination of photogenerated carriers at the defects on the first surface, thereby reducing the dark current of the pixel unit; The second doped portion (8) is located on the side of the first doped portion (6) away from the second conductive layer (A2), and the second doped portion (8) is spaced apart from the first doped portion (6); the active portion (5) covers a portion of the first doped portion (6) and the second doped portion (8). The isolation section (9) extends from the first surface into the interior of the active section (5); The material of the protrusion structure (7) in the second conductive layer (A2) is the same as the material of the active part (5), or the material of the protrusion structure (7) is the same as the material of the photoelectric conversion unit (12) in the second conductive layer (A2).

12. The pixel unit according to claim 11, characterized in that, The pixel unit further includes an insulating portion (10), a conductive layer (11), and a lens (1), and the substrate (A3) includes a second surface disposed opposite to the first surface; The insulating portion (10) is disposed on the side of the second surface away from the second conductive layer (A2); The conductive layer (11) is disposed inside the insulating part (10) and is used to export the photogenerated carriers as image signals; The lens (1) is disposed on the side of the first conductive layer (A1) away from the substrate (A3) and is used to focus the incident light onto the first conductive layer (A1).

13. A method for fabricating a pixel unit, characterized in that, The method is applied to the fabrication of a pixel unit as described in any one of claims 1 to 12, the method comprising: An absorption layer is formed, and a portion of the absorption layer is a photosensitive material used to scatter and absorb the refracted light to generate an electrical signal, thereby forming an image electrical signal corresponding to the incident light. A first conductive layer is formed, the first conductive layer including a plurality of spaced optical control units, the plurality of spaced optical control units being used to change the exit angle of incident light and form refracted light, so that the incident angle of the refracted light matches the refractive index of the absorption layer.

14. The method for preparing a pixel unit according to claim 13, characterized in that, The absorption layer includes a substrate and a second conductive layer, and forming the absorption layer includes: Provide substrate; A light-absorbing layer is deposited and formed on the side of the substrate near the first conductive layer; The light-absorbing layer is etched to form a raised structure; A passivation layer is deposited to form a passivation layer located on the side of the protrusion structure away from the substrate; A photoelectric conversion unit is deposited and formed, the photoelectric conversion unit being located on the side of the passivation layer away from the substrate; A first filler layer is deposited to form the photoelectric conversion unit on the side away from the substrate.

15. An image sensor, characterized in that, It includes a plurality of pixel units as described in any one of claims 1 to 12.

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