Pixel unit, preparation method thereof, image sensor, camera and electronic device

Abstract

The present disclosure provides a pixel unit and a preparation method thereof, an image sensor, a camera and an electronic device, and relates to the technical field of image sensors, and aims to solve the technical problem of a complex preparation process of the pixel unit. The preparation method of the pixel unit comprises forming a first doped layer on one side of a substrate. A second doped layer is formed on the side of the first doped layer away from the substrate, and the doping type of the second doped layer is different from the doping type of the first doped layer. A photosensitive part is formed in the second doped layer. The first doped layer is used as a stop layer to remove the substrate. The preparation method of the pixel unit provided by the present disclosure is used for preparing the pixel unit.

Description

Technical Field

[0001] This disclosure relates to the technical field of image sensors, and more particularly to a method for fabricating a pixel unit, a pixel unit, an image sensor, a camera assembly, and an electronic device. Background Technology

[0002] Image sensors typically include pixel units, which are used to acquire light signals and convert them into electrical signals, enabling the image sensor to perform image acquisition.

[0003] In related technologies, the fabrication process of pixel units is complex, which increases the cost of pixel units and thus increases the cost of image sensors. Summary of the Invention

[0004] To address the technical problem of complex fabrication processes for pixel units in related technologies, embodiments of this disclosure provide a method for fabricating a pixel unit, a pixel unit, an image sensor, a camera assembly, and an electronic device.

[0005] To achieve the above objectives, the embodiments of this disclosure adopt the following technical solutions:

[0006] In a first aspect, a method for fabricating a pixel unit is provided. The method includes forming a first doped layer on one side of a substrate. A second doped layer is formed on the side of the first doped layer away from the substrate, the doping type of the second doped layer being different from that of the first doped layer. A photosensitive portion is formed within the second doped layer. The first doped layer is used as a stop layer to remove the substrate.

[0007] In the embodiments of this disclosure, the first doped layer provides a stop layer for substrate removal. Therefore, during the substrate removal process, it is not necessary to repeatedly measure the thickness of the remaining layer structure (e.g., the remaining part of the substrate, the first doped layer, and the second doped layer) to determine whether the substrate has been completely removed. Instead, the determination of whether the substrate has been completely removed is made by judging whether the first surface exposed during the substrate removal process is the surface of the first doped layer away from the second doped layer (which is also judging whether the surface of the first doped layer away from the second doped layer is exposed). This simplifies the pixel unit fabrication process, improves the pixel unit production efficiency, and reduces the pixel unit cost.

[0008] Furthermore, by using the first doped layer as a stop layer during substrate removal, the first doped layer can protect the second doped layer, and thus protect the photosensitive part located within the second doped layer. This reduces the risk of the second doped layer being removed or partially removed, thereby reducing the risk of damage or removal of the photosensitive part and improving the reliability of the pixel unit fabrication method.

[0009] Furthermore, after the first doped layer is formed, a second doped layer is formed on the side of the first doped layer away from the substrate. This eliminates the need for processes such as high-energy ion implantation, allowing for deep implantation of dopants in the first doped layer. This reduces the damage to the second doped layer caused by processes such as high-energy ion implantation, improves the reliability of the pixel unit, and lowers the production cost of the pixel unit.

[0010] Understandably, since the photosensitive part is located within the second doped layer and far from the first doped layer, during photoelectric conversion, electrons or holes provided by the first doped layer can diffuse to the photosensitive part, increasing the width of the depletion region (the region where photogenerated carriers are depleted due to diffusion) of the pixel unit. This allows the pixel unit to acquire longer wavelength light signals (such as infrared or near-infrared light), improving the photoelectric conversion performance and efficiency of the pixel unit, thereby enhancing the image acquisition performance of the image sensor.

[0011] In some embodiments, the substrate includes a doped substrate. The doping type of the first doped layer is different from the doping type of the substrate. This configuration allows for the determination of whether the doped substrate has been completely removed by detecting the doping type of the first surface (the surface exposed during the removal of the doped substrate), further simplifying the pixel unit fabrication process, improving the accuracy of the determination results, and thus enhancing the reliability of the pixel unit fabrication method.

[0012] In some embodiments, the substrate is an undoped substrate. With this configuration, by determining whether doping elements (i.e., doping elements in the first doped layer) can be detected on the first surface (the surface exposed during the removal of the undoped substrate), it can be determined whether the undoped substrate has been completely removed, further simplifying the pixel unit fabrication process and improving production efficiency.

[0013] In some embodiments, the step of forming a first doped layer on one side of the substrate includes using an epitaxial growth process to form the first doped layer on one side of the substrate. The step of forming a second doped layer on the side of the first doped layer away from the substrate includes using an epitaxial growth process to form the second doped layer on the side of the first doped layer away from the substrate. This configuration reduces lattice defects in the first and second doped layers, lowers the impurity content in the first and second doped layers, and facilitates control of the dopant ion concentrations in the first and second doped layers, improving the uniformity of ion doping concentrations in both layers. Furthermore, it facilitates control of the thickness of the first and second doped layers, improving the reliability of the pixel unit fabrication method. Moreover, using an epitaxial growth process to form the first and second doped layers reduces the requirements for the lower-level operating equipment, further simplifying the pixel unit fabrication process and reducing production costs.

[0014] In some embodiments, the photosensitive portion includes a first doped portion and a second doped portion. The step of forming the photosensitive portion within the second doped layer includes forming the first doped portion within the second doped layer. The doping type of the first doped portion is the same as the doping type of the first doped layer. A second doped portion is formed within the second doped layer, spaced apart from the first doped portion. The doping type of the second doped portion is the same as the doping type of the second doped layer. Furthermore, the ion doping concentration of the second doped portion is different from the ion doping concentration of the second doped layer. This arrangement allows the first and second doped layers to form a PN junction, thereby enabling the pixel unit to perform photoelectric conversion.

[0015] In some embodiments, after forming the photosensitive portion within the second doped layer, a metal interconnect layer is further formed on the side of the second doped layer away from the first doped layer. A carrier sheet is bonded to the surface of the metal interconnect layer away from the second doped layer to form a bond. Using the first doped layer as a stop layer, the bond is flipped before the substrate removal step. This arrangement allows the electrical signal converted from the optical signal to be transmitted outside the pixel unit through the metal interconnect layer. Furthermore, the carrier sheet provides support and protection for the first doped layer, the second doped layer, and the metal interconnect layer, reducing the risk of breakage during substrate removal and improving the reliability of the pixel unit fabrication method. Moreover, flipping the bond before substrate removal ensures that the surface of the substrate away from the first doped layer faces upwards, facilitating substrate removal and improving the ease of pixel unit fabrication.

[0016] In some embodiments, before bonding the carrier sheet to the surface of the metal interconnect layer away from the second doped layer, a first metal electrode is formed. The first metal electrode penetrates the metal interconnect layer along the direction from the metal interconnect layer to the second doped layer and is electrically connected to the first doped portion. A second metal electrode is then formed. The second metal electrode penetrates the metal interconnect layer along the direction from the metal interconnect layer to the second doped layer and is electrically connected to the second doped portion. This configuration provides power to both the first and second doped portions through the first and second metal electrodes, enabling the pixel unit to perform photoelectric conversion.

[0017] In some embodiments, the first doped layer is used as a stop layer, and after the substrate removal step, a light-modulating component is formed on the side of the first doped layer away from the second doped layer. The carrier sheet is debonded to the surface of the metal interconnect layer away from the second doped layer. This configuration increases the intensity of light irradiating the photosensitive portion, enabling the pixel unit to acquire weak light signals, improving the reliability of the pixel unit, and thus improving the reliability of the image sensor. Furthermore, during the formation of the light-modulating component, the carrier sheet provides support and protection for the metal interconnect layer, the first doped layer, and the second doped layer, reducing the risk of breakage of these layers and improving the reliability of the pixel unit fabrication method.

[0018] On the other hand, a pixel unit is provided. The pixel unit is fabricated using the pixel unit fabrication method described above. The pixel unit includes a first doped layer, a second doped layer, and a photosensitive portion. The second doped layer is located to one side of the first doped layer. The doping type of the second doped layer is different from that of the first doped layer. The photosensitive portion is located within the second doped layer.

[0019] The pixel units provided in the embodiments of this disclosure are prepared using the pixel unit preparation method described above, and therefore have all the above-described beneficial effects, which will not be repeated here.

[0020] In some embodiments, the thickness of the first doped layer ranges from 0.1 μm to 5 μm. The ion doping concentration of the first doped layer ranges from 1e. 13 / cm 3 ~1e 17 / cm 3 This configuration avoids the first doped layer being too thin (e.g., less than 0.1 μm), thus reducing the risk of completely removing the first doped layer during substrate removal and allowing it to serve as a stop layer during substrate removal. Furthermore, it avoids the first doped layer being too thick (e.g., greater than 5 μm), reducing the distance between the light-receiving surface (i.e., the surface of the first doped layer furthest from the second doped layer) and the photosensitive element, increasing the intensity of light irradiating the photosensitive element and improving the photoelectric conversion performance of the pixel unit. The ion doping concentration of the first doped layer is set to a range of 1e-1. 13 / cm 3 ~1e 17 / cm 3 This avoids the first doped layer having too low an ion doping concentration (e.g., less than 1e). 13 / cm 3 This allows for easy determination of whether the surface of the first doped layer away from the second doped layer is exposed during substrate removal, enabling the first doped layer to serve as a stop layer during substrate removal. It also avoids situations where the ion doping concentration in the first doped layer is too low (e.g., less than 1 e^(-1e ... 13 / cm 3 This also increases the amount of electrons or holes provided by the first doped layer to the photosensitive part, thereby improving the photoelectric conversion performance of the pixel unit. Furthermore, it avoids excessively high ion doping concentration in the first doped layer (e.g., greater than 1 e^(-1e ... 17 / cm 3 Based on the fact that the first doped layer can serve as a stop layer when removing the substrate, the fabrication process of the first doped layer is simplified, and the cost of the pixel unit is reduced.

[0021] In some embodiments, the thickness of the second doped layer ranges from 1 μm to 2.5 μm. The ion doping concentration of the second doped layer ranges from 1e. 14 / cm 3 ~1e 17 / cm 3 This configuration avoids the second doped layer being too thin (e.g., less than 1 μm), allowing the photosensitive element to be embedded within it. Furthermore, it avoids the second doped layer being too thick (e.g., greater than 2.5 μm), thereby increasing the intensity of light illuminating the photosensitive element and improving the photoelectric conversion performance of the pixel unit. The ion doping concentration of the second doped layer is set to a range of 1e-1. 14 / cm 3 ~1e 17 / cm 3 This avoids the second doped layer having an excessively low ion doping concentration (e.g., less than 1e). 14 / cm 3 This increases the amount of electrons or holes provided by the second doped layer to the photosensitive part, thereby improving the photoelectric conversion performance of the pixel unit. Furthermore, it avoids excessively high ion doping concentrations in the second doped layer (e.g., greater than 1 e^(-1e ... 17 / cm 3 This simplifies the fabrication process of the second doped layer and reduces the cost of the pixel unit while still meeting the requirements for photoelectric conversion.

[0022] In some embodiments, the first doped layer is an N-type doped layer, and the second doped layer is a P-type doped layer. This configuration allows the P-type doped layer to provide holes to the photosensitive portion, thereby increasing the amount of hole migration during photoelectric conversion and improving the photoelectric conversion performance of the pixel unit. Furthermore, during photoelectric conversion, the N-type doped layer can provide electrons to the photosensitive portion, increasing the depletion region width and further improving the photoelectric conversion performance of the pixel unit, thereby enhancing the photoelectric conversion performance of the image sensor.

[0023] In some embodiments, the pixel unit further includes a light adjustment component. The light adjustment component includes an anti-reflective film, a filter, and a microlens. The anti-reflective film is located on the side of the first doped layer away from the second doped layer and covers the first doped layer. The filter is located on the side of the anti-reflective film away from the first doped layer. The microlens is located on the side of the filter away from the anti-reflective film. This configuration further increases the intensity of light illuminating the photosensitive portion, enabling the photosensitive portion to acquire weak light signals, improving the reliability of the pixel unit, and thus improving the reliability of the image sensor. Furthermore, it allows different colors of monochromatic light (e.g., red, green, and blue light) to illuminate the photosensitive portion, meaning the pixel unit can convert light signals of different colors of monochromatic light into electrical signals, improving the applicability of the pixel unit.

[0024] On the other hand, an image sensor is provided. The image sensor includes at least two pixel units as described above. The at least two pixel units are arranged in an array.

[0025] The image sensor provided in the embodiments of this disclosure includes at least two pixel units as described above, and therefore has all the beneficial effects described above, which will not be repeated here.

[0026] In some embodiments, the image sensor further includes an isolation section. The isolation section is located between any two adjacent pixel units. This arrangement reduces the intensity of light illuminating adjacent pixel units, thereby reducing optical crosstalk between adjacent pixel units and improving the reliability of the image sensor.

[0027] In another aspect, a camera assembly is provided. The camera assembly includes a lens assembly and an image sensor as described above. The image sensor is located on the light-emitting side of the lens assembly.

[0028] The camera assembly provided in the embodiments of this disclosure includes the image sensor as described above, and therefore has all the aforementioned beneficial effects, which will not be repeated here.

[0029] In another aspect, an electronic device is provided. The electronic device includes a housing and a camera assembly as described above. The housing has a first through-hole. The camera assembly is embedded in the first through-hole.

[0030] The electronic device provided by the embodiments of this disclosure includes the camera component as described above, and therefore has all the aforementioned beneficial effects, which will not be repeated here.

[0031] In some embodiments, the housing also has a second through-hole. The electronic device also includes a transmitter. The transmitter is used to emit light towards the object to be detected. A camera assembly is used to receive the light reflected from the object to be detected. Alternatively, the camera assembly is used to receive light passing through the object to be detected. This configuration enables the electronic device to acquire image information of the object to be detected even in low-light conditions, improving the applicability of the electronic device. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are only drawings of some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings. In addition, the drawings described below can be regarded as schematic diagrams and are not intended to limit the actual size of the product, the actual process of the method, etc. involved in the embodiments of this disclosure.

[0033] Figure 1 This is a structural diagram of an image sensor according to some embodiments;

[0034] Figure 2 for Figure 1 A cross-sectional view along the AA direction;

[0035] Figure 3A This is a structural diagram of the substrate, the second doped layer, and the photosensitive part according to some embodiments;

[0036] Figure 3B This is a structural diagram of the second doped layer and the photosensitive part according to some embodiments;

[0037] Figure 4A A flowchart illustrating the steps of a method for fabricating a pixel unit according to some embodiments;

[0038] Figure 4B This is a structural diagram of the substrate and the first doped layer according to some embodiments;

[0039] Figure 4C This is a structural diagram of a substrate, a first doped layer, and a second doped layer according to some embodiments;

[0040] Figure 4D This is a structural diagram of the photosensitive part according to some embodiments;

[0041] Figure 4E This is a structural diagram of the substrate, the first doped layer, and the second doped layer according to some other embodiments;

[0042] Figure 4F This is a structural diagram of the first doped layer and the second doped layer according to some embodiments;

[0043] Figure 4G for Figure 1 Another cross-sectional view along the AA direction;

[0044] Figure 5 A flowchart illustrating the steps of a method for fabricating a pixel unit according to some other embodiments;

[0045] Figure 6A A flowchart illustrating the steps of a method for fabricating a pixel unit according to some other embodiments;

[0046] Figure 6B This is a structural diagram of a metal interconnect layer according to some embodiments;

[0047] Figure 6C This is a structural diagram of a bond according to some embodiments;

[0048] Figure 6D This is a structural diagram of a bond according to some other embodiments;

[0049] Figure 6E This is a structural diagram of a first doped layer, a second doped layer, and a metal interconnect layer according to some embodiments;

[0050] Figure 7A A flowchart illustrating the steps of a method for fabricating a pixel unit according to some other embodiments;

[0051] Figure 7B This is a structural diagram of a first metal electrode and a second metal electrode according to some embodiments;

[0052] Figure 8A A flowchart illustrating the steps of a method for fabricating a pixel unit according to some other embodiments;

[0053] Figure 8B This is a structural diagram of a light-adjusting assembly according to some embodiments;

[0054] Figure 8C This is a structural diagram of a light-adjusting assembly according to some other embodiments;

[0055] Figure 9 This is a structural diagram of a camera assembly according to some embodiments;

[0056] Figure 10 This is a structural diagram of an electronic device according to some embodiments. Detailed Implementation

[0057] The embodiments of this disclosure will now be described in detail with reference to the accompanying drawings.

[0058] In the description of this disclosure, it should be understood that the terms “center,” “upper,” “lower,” “front,” “rear,” “left,” “right,” “vertical,” “horizontal,” “top,” “bottom,” “inner,” and “outer,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this disclosure.

[0059] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, unless otherwise stated, "a plurality of" means two or more.

[0060] In the description of this disclosure, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this disclosure based on the specific circumstances.

[0061] Figure 1 This is a structural diagram of an image sensor according to some embodiments. Figure 2 for Figure 1 A cross-sectional view along the AA direction.

[0062] like Figure 1 As shown, embodiments of this disclosure provide an image sensor 200. In some examples, the image sensor 200 is a complementary metal-oxide-semiconductor (CMOS) image sensor.

[0063] In some examples, such as Figure 1 As shown, the image sensor 200 includes multiple pixel units 100 arranged in a matrix. Each pixel unit 100 can convert received light signals into electrical signals. By acquiring the electrical signal output by each pixel unit 100, and then amplifying and performing digital-to-analog conversion on the electrical signal, the light information corresponding to that pixel unit 100 can be obtained, enabling the image sensor 200 to achieve image acquisition.

[0064] For example, pixel unit 100 can convert received visible light (e.g., white light or monochromatic light) light signals into electrical signals, and can also convert received invisible light (e.g., infrared light, near-infrared light, X-rays or gamma rays) light signals into electrical signals.

[0065] In some examples, a portion (two or more) of the plurality of pixel units 100 are used to convert the received red light optical signal into an electrical signal, another portion (two or more) are used to convert the received green light optical signal into an electrical signal, and yet another portion (two or more) are used to convert the received blue light optical signal into an electrical signal.

[0066] In some examples, pixel unit 100 includes a photodiode (PD) that enables pixel unit 100 to convert received light signals into electrical signals.

[0067] For example, such as Figure 2 As shown, the pixel unit 100 has a light-receiving surface 202 and a back-lighting surface 204, which are arranged opposite to each other. Light shines on the pixel unit 100 along the direction from the light-receiving surface 202 to the back-lighting surface 204. In some examples, the light-receiving surface 202 and the back-lighting surface 204 are smooth or nearly smooth planes.

[0068] It should be noted that, Figure 1 and Figure 2 Only a portion (two or more) of the pixel units 100 in the image sensor 200 are shown in the present disclosure. The embodiments of this disclosure do not further limit the number of pixel units 100 in the image sensor 200.

[0069] Figure 3A This is a structural diagram of the substrate, the second doped layer, and the photosensitive part according to some embodiments. Figure 3B This is a structural diagram of the second doped layer and the photosensitive portion according to some embodiments. Referring below... Figure 3A and Figure 3B The following is an example illustrating the preparation method of any one of the multiple pixel units 100 in some implementations of this disclosure.

[0070] In some implementations, such as Figure 3A As shown, the method for fabricating pixel unit 100 includes forming a second doped layer 120 on one side of substrate 102. For example, substrate 102 may be a silicon substrate, germanium substrate, silicon-on-insulator substrate, silicon carbide substrate, or other suitable semiconductor material.

[0071] In some examples, substrate 102 is a wafer. For example, the diameter of substrate 102 can be 4 inches, 6 inches, 8 inches, or 12 inches, etc.

[0072] like Figure 3A As shown, a photosensitive portion 130 is formed in the second doped layer 120. Understandably, the photosensitive portion 130 is used to convert optical signals into electrical signals, and for example, the photosensitive portion 130 includes a PN junction.

[0073] like Figure 3B As shown, after forming the photosensitive portion 130, the substrate 102 is removed. For example, as... Figure 2 As shown, after removing the substrate 102, one side surface of the second doped layer 120 can become the light-receiving surface 202 of the pixel unit 100, and the other side surface can become the backlight surface 204 of the pixel unit 100.

[0074] The inventors of this disclosure have discovered that, in the above implementation, the lack of a stop layer during substrate 102 removal makes it difficult to determine whether substrate 102 has been completely removed. For example, it is necessary to repeatedly measure the thickness of the remaining layer structure (e.g., the remaining portion of substrate 102 and the second doped layer 120) to determine whether substrate 102 has been completely removed, increasing the complexity of the pixel unit 100 fabrication process and reducing production efficiency.

[0075] Furthermore, since there is no stop layer when removing the substrate 102, the risk of partially or completely removing the second doped layer 120 is increased, which increases the risk of the photosensitive part 130 being damaged or removed, thus reducing the reliability of the pixel unit 100 fabrication method.

[0076] In order to simplify the fabrication process of pixel unit 100 and improve the reliability of the fabrication method of pixel unit 100, some embodiments of this disclosure provide a fabrication method of pixel unit 100.

[0077] Figure 4A This is a flowchart of the steps in a method for fabricating a pixel unit according to some embodiments. Figure 4B This is a structural diagram of a substrate and a first doped layer according to some embodiments. Figure 4C This is a structural diagram of a substrate, a first doped layer, and a second doped layer according to some embodiments. Figure 4D This is a structural diagram of the photosensitive part according to some embodiments. Figure 4E This is a structural diagram of a substrate, a first doped layer, and a second doped layer according to some other embodiments. Figure 4F This is a structural diagram of a first doped layer and a second doped layer according to some embodiments.

[0078] like Figure 4A As shown, the method for fabricating this pixel unit includes:

[0079] Step S101: A first doped layer is formed on one side of the substrate.

[0080] Understandably, the above embodiments of this disclosure have already illustrated the substrate 102, and will not be repeated here.

[0081] For example, such as Figure 4B As shown, the first doped layer 110 is located on one side surface of the substrate 102 and covers the substrate 102.

[0082] In some examples, the first doped layer 110 is a P-type doped layer. In other examples, the first doped layer 110 is an N-type doped layer. In some examples, at least one of boron, aluminum, gallium, indium, and thallium can be doped into the first doped layer 110 to form a P-type doped layer. In other examples, at least one of phosphorus, arsenic, and antimony can be doped into the first doped layer 110 to form an N-type doped layer.

[0083] In some examples, such as Figure 4B As shown, the thickness L1 of the substrate 102 is greater than the thickness L2 of the first doped layer 110, so that the substrate 102 can support and protect the first doped layer 110, reducing the risk of the first doped layer 110 breaking.

[0084] In step S102, a second doped layer is formed on the side of the first doped layer away from the substrate, and the doping type of the second doped layer is different from that of the first doped layer.

[0085] like Figure 4C As shown, the second doped layer 120 is located on the surface of the first doped layer 110 away from the substrate 102 and covers the first doped layer 110. The doping type of the second doped layer 120 is different from that of the first doped layer 110. That is, the number of outermost electrons of the doped element in the second doped layer 120 is different from the number of outermost electrons of the doped element in the first doped layer 110.

[0086] In some examples, the first doped layer 110 is an N-type doped layer and the second doped layer 120 is a P-type doped layer. In other examples, the first doped layer 110 is a P-type doped layer and the second doped layer 120 is an N-type doped layer.

[0087] It is understood that the above embodiments of this disclosure have provided examples of doping elements for P-type doping and N-type doping, and will not be repeated here.

[0088] Step S103: A photosensitive part is formed in the second doped layer.

[0089] like Figure 4DAs shown, a photosensitive portion 130 is formed in the second doped layer 120. Understandably, the photosensitive portion 130 can convert the received light signal into an electrical signal, so that the pixel unit 100 can realize the photoelectric conversion function.

[0090] In some examples, the photosensitive unit 130 includes a PN junction. For example, when the photosensitive unit 130 is illuminated, it can generate freely moving electrons and holes, called photogenerated carriers, enabling the pixel unit 100 to perform photoelectric conversion.

[0091] In some examples, the photosensitive portion 130 can be formed by ion implantation. For example, ion implantation can be performed on the surface of the second doped layer 120 away from the first doped layer 110 to form the photosensitive portion 130 within the second doped layer 120. Understandably, the photosensitive portion 130 is located away from the first doped layer 110.

[0092] In some examples, such as Figure 4C As shown, the thickness L3 of the second doped layer 120 is greater than the thickness L2 of the first doped layer 110, which increases the thickness L3 of the second doped layer 120 and makes it easier to form the photosensitive part 130 in the second doped layer 120.

[0093] Step S104: Use the first doped layer as a stop layer to remove the substrate.

[0094] Understandably, such as Figure 4D As shown, the first surface P1 can be exposed during the removal of substrate 102. In some examples, chemical mechanical polishing (CMP) can be used to remove substrate 102.

[0095] For example, such as Figure 4D As shown, when the substrate 102 is not removed, the first surface P1 is the surface of the substrate 102 away from the second doped layer 120. Figure 4E As shown, when the substrate 102 is partially removed (the removed portion is as follows) Figure 4E (As shown by the dashed line), the first surface P1 is the surface of the remaining portion of the substrate 102a away from the second doped layer 120. For example... Figure 4F As shown, when the substrate 102 is completely removed, the first surface P1 is the surface of the first doped layer 110 away from the second doped layer 120.

[0096] Understandably, in the embodiments of this disclosure, substrate 102a is used only to indicate the portion of substrate 102 remaining during the removal of substrate 102, and does not further limit substrate 102.

[0097] Understandably, the first doped layer 110 provides a stop layer for removing the substrate 102. Therefore, during the removal of the substrate 102, it is not necessary to repeatedly measure the thickness of the remaining layer structure (e.g., the remaining portion of the substrate 102, the first doped layer 110, and the second doped layer 120) to determine whether the substrate 102 has been completely removed. Instead, it is determined whether the substrate 102 has been completely removed by judging whether the exposed first surface P1 is the surface of the first doped layer 110 away from the second doped layer 120 (which is also judging whether the surface of the first doped layer 110 away from the second doped layer 120 is exposed). This simplifies the fabrication process of the pixel unit 100, improves the production efficiency of the pixel unit 100, and reduces the cost of the pixel unit 100.

[0098] Furthermore, by using the first doped layer 110 as a stop layer during the removal of the substrate 102, the first doped layer 110 can protect the second doped layer 120, that is, it can protect the photosensitive part 130 located within the second doped layer 120. This reduces the risk of the second doped layer 120 being removed or partially removed, thus reducing the risk of the photosensitive part 130 being damaged or removed, and improving the reliability of the pixel unit 100 fabrication method.

[0099] In some examples, the first doped layer 110 and the substrate 102 have at least one difference. For example, the first doped layer 110 may be doped with a first element, while the substrate 102 may not be doped with the first element, or the amount of the first element in the substrate 102 may be extremely small and negligible. In this way, by determining whether the first element can be detected on the exposed first surface P1, it can be determined whether the substrate 102 has been completely removed, thus improving the accuracy of the determination result.

[0100] In some examples, the first element is an easily detectable dopant element, such as phosphorus, arsenic, and antimony.

[0101] Figure 4G for Figure 1 Another cross-sectional view along the AA direction.

[0102] Understandably, after removing the substrate 102, the surface of the first doped layer 110 on the side away from the second doped layer 120 can be exposed. For example, as... Figure 4G As shown, the surface of the first doped layer 110 away from the second doped layer 120 can be used as the light-receiving surface 202 of the pixel unit 100.

[0103] As described above, the photosensitive part 130 is located within the second doped layer 120 and is far from the first doped layer 110. When the photosensitive part 130 is illuminated, it can generate freely moving electrons and holes (i.e., photogenerated carriers).

[0104] Understandably, during photoelectric conversion, the majority carriers provided by the P-type semiconductor are holes, and the minority carriers are electrons. The majority carriers provided by the N-type semiconductor are electrons, and the minority carriers provided by the N-type doped layer are holes. That is, in some examples, when the first doped layer 110 is an N-type doped layer, it can provide freely moving electrons to the photosensitive part 130. In other examples, when the first doped layer 110 is a P-type doped layer, it can provide freely moving holes to the photosensitive part 130.

[0105] In this way, the electrons or holes provided by the first doped layer 110 can diffuse to the photosensitive part 130, increasing the width of the depletion region (the region where photogenerated carriers are depleted due to diffusion) of the pixel unit 100, enabling the pixel unit 100 to acquire longer wavelength light signals (such as infrared light or near-infrared light), improving the photoelectric conversion performance of the pixel unit 100, and also improving the photoelectric conversion efficiency of the pixel unit 100, thereby improving the image acquisition effect of the image sensor 200.

[0106] As can be seen from the above, in the embodiments of this disclosure, the first doped layer 110 provides a stop layer for removing the substrate 102. Therefore, during the removal of the substrate 102, it is not necessary to repeatedly measure the thickness of the remaining layer structure (e.g., the remaining part of the substrate 102, the first doped layer 110, and the second doped layer 120) to determine whether the substrate 102 has been completely removed. Instead, it is determined whether the first surface P1 exposed during the removal of the substrate 102 is the surface of the first doped layer 110 away from the second doped layer 120 (which is also a determination of whether the surface of the first doped layer 110 away from the second doped layer 120 is exposed) to determine whether the substrate 102 has been completely removed. This simplifies the fabrication process of the pixel unit 100, improves the production efficiency of the pixel unit 100, and reduces the cost of the pixel unit 100.

[0107] Furthermore, by using the first doped layer 110 as a stop layer during the removal of the substrate 102, the first doped layer 110 can protect the second doped layer 120, that is, it can protect the photosensitive part 130 located within the second doped layer 120. This reduces the risk of the second doped layer 120 being removed or partially removed, thus reducing the risk of the photosensitive part 130 being damaged or removed, and improving the reliability of the pixel unit 100 fabrication method.

[0108] Furthermore, after the first doped layer 110 is formed, a second doped layer 120 is formed on the side of the first doped layer 110 away from the substrate 102. This eliminates the need for processes such as high-energy ion implantation to achieve deep implantation of doped elements in the first doped layer 110, reducing the damage to the second doped layer 120 caused by processes such as high-energy ion implantation, improving the reliability of the pixel unit 100, and reducing the production cost of the pixel unit 100.

[0109] Understandably, since the photosensitive portion 130 is located within the second doped layer 120 and far from the first doped layer 110, during photoelectric conversion, electrons or holes provided by the first doped layer 110 can diffuse to the photosensitive portion 130, increasing the width of the depletion region (the region where photogenerated carriers are depleted due to diffusion) of the pixel unit 100. This allows the pixel unit 100 to acquire longer wavelength light signals (e.g., infrared or near-infrared light), improving the photoelectric conversion performance of the pixel unit 100 and also increasing its photoelectric conversion efficiency, thereby improving the image acquisition performance of the image sensor 200.

[0110] In some embodiments, substrate 102 includes a doped substrate. The doping type of the first doped layer 110 is different from the doping type of substrate 102.

[0111] Understandably, the doping type of the first doped layer 110 is different from that of the doped substrate. That is, the number of outermost electrons of the doped element in the first doped layer 110 is different from the number of outermost electrons of the doped element in the doped substrate.

[0112] In some examples, the doped substrate includes a P-type doped substrate, and the first doped layer 110 is an N-type doped layer. In other examples, the doped substrate includes an N-type doped substrate, and the first doped layer 110 is a P-type doped layer.

[0113] The doping type of the doped substrate is set to be different from that of the first doped layer 110, so that by detecting the doping type of the first surface P1 (the surface exposed during the removal of the doped substrate), it can be determined whether the doped substrate has been completely removed.

[0114] For example, when the doped substrate is not completely removed, the doped element detected by the first surface P1 is the doped element in the doped substrate. When the doped substrate is completely removed, the doped element detected by the first surface P1 is the doped element in the first doped layer 110. Since the doping type of the doped substrate is different from the doping type of the first doped layer 110, the detected doped element can be used to determine whether the surface of the first doped layer 110 away from the second doped layer 120 is exposed, that is, to determine whether the doped substrate has been completely removed. This further simplifies the fabrication process of the pixel unit 100, improves the accuracy of the determination result, and thus improves the reliability of the fabrication method of the pixel unit 100.

[0115] As can be seen from the above, in some embodiments, the substrate 102 includes a doped substrate. In other embodiments, the substrate 102 is an undoped substrate.

[0116] Understandably, when the substrate 102 is an undoped substrate, the substrate 102 does not contain any doping elements, or the content of doping elements in the substrate 102 is extremely small and can be ignored.

[0117] Since the first doped layer 110 is a P-type doped layer or an N-type doped layer, it can be determined whether the undoped substrate has been completely removed by judging whether the doping element (that is, the doping element in the first doped layer 110) can be detected on the first surface P1 (the surface exposed during the removal of the undoped substrate).

[0118] For example, when the undoped substrate is not completely removed, it is difficult to detect doped elements through the first surface P1. When the undoped substrate is completely removed, the doped elements of the first doped layer 110 can be detected through the first surface P1. Therefore, by determining whether the doped elements in the first doped layer 110 can be detected by the first surface P1, it can be determined whether the surface of the first doped layer 110 away from the second doped layer 120 is exposed, that is, whether the undoped substrate has been completely removed, further simplifying the fabrication process of the pixel unit 100 and improving production efficiency.

[0119] For example, when detecting the first surface P1, multiple detection points can be selected at intervals on the first surface P1 to improve the accuracy of the detection results.

[0120] In some embodiments, the step of forming a first doped layer on one side of the substrate (i.e., step S101) includes forming a first doped layer on one side of the substrate using an epitaxial growth process.

[0121] For example, the epitaxial growth process involves growing an epitaxial layer with a complete crystal lattice and different impurity concentrations and thicknesses on a substrate 102 in the same crystal orientation and in a single-crystal manner.

[0122] like Figure 4B As shown, the first doped layer 110 is formed on one side of the substrate 102 by using an epitaxial growth process, which can reduce lattice defects in the first doped layer 110, reduce the impurity content in the first doped layer 110, and make it easier to control the dopant ion concentration in the first doped layer 110, thereby improving the uniformity of the ion doping concentration in the first doped layer 110. In addition, it is also easier to control the thickness of the first doped layer 110, thereby improving the reliability of the fabrication method of the pixel unit 100.

[0123] Furthermore, using an epitaxial growth process to form the first doped layer 110 can reduce the requirements for the lower-level operating equipment and further simplify the fabrication process of the pixel unit 100.

[0124] The step of forming a second doped layer on the side of the first doped layer away from the substrate (i.e., step S102) includes using an epitaxial growth process to form a second doped layer on the side of the first doped layer away from the substrate.

[0125] Similarly, such as Figure 4C As shown, the second doped layer 120 is formed on the side of the first doped layer 110 away from the substrate 102 by using an epitaxial growth process. This can reduce lattice defects in the second doped layer 120, reduce the impurity content in the second doped layer 120, and make it easier to control the dopant ion concentration in the second doped layer 120, thereby improving the uniformity of the ion doping concentration in the second doped layer 120. In addition, it is also easier to control the thickness of the second doped layer 120, thereby improving the reliability of the fabrication method of the pixel unit 100.

[0126] Furthermore, the use of epitaxial growth process to form the second doped layer 120 can reduce the requirements for the lower-level operating equipment and further simplify the fabrication process of the pixel unit 100.

[0127] In some embodiments, such as Figure 4G As shown, the photosensitive part 130 includes a first doped part 132 and a second doped part 134.

[0128] Figure 5 This is a flowchart of the steps of a method for fabricating a pixel unit according to some other embodiments.

[0129] In some embodiments, such as Figure 5 As shown, the step of forming the photosensitive portion within the second doped layer (i.e., step S103) includes:

[0130] Step S201: A first doped portion is formed within the second doped layer. The doping type of the first doped portion is the same as the doping type of the first doped layer.

[0131] In some examples, see Figure 4D The first doped portion 132 can be formed in the second doped layer 120 using an ion implantation process. For example, ion implantation can be performed on the surface of the second doped layer 120 away from the first doped layer 110 to form the first doped portion 132 in the second doped layer 120. Understandably, the first doped portion 132 is located away from the first doped layer 110.

[0132] Understandably, the doping type of the first doped portion 132 is the same as the doping type of the first doped layer 110. That is, the number of outermost electrons of the dopant element in the first doped portion 132 is the same as the number of outermost electrons of the dopant element in the first doped layer 110. Understandably, the doping element of the first doped portion 132 and the doping element of the first doped layer 110 can be the same or different.

[0133] In some examples, the first doped layer 110 is an N-type doped layer, and the first doped portion 132 is an N-type doped portion. In other examples, the first doped layer 110 is a P-type doped layer, and the first doped portion 132 is a P-type doped portion.

[0134] In some examples, the ion doping concentration of the first doped portion 132 is greater than the ion doping concentration of the first doped layer 110.

[0135] In step S202, a second doped portion is formed within the second doped layer. The second doped portion is spaced apart from the first doped portion, and the doping type of the second doped portion is the same as that of the second doped layer. Furthermore, the ion doping concentration of the second doped portion is different from that of the second doped layer.

[0136] See Figure 4D In some examples, an ion implantation process can be used to form the second doped portion 134 in the second doped layer 120. For example, ion implantation can be performed on the surface of the second doped layer 120 away from the first doped layer 110 to form the second doped portion 134 in the second doped layer 120. Understandably, the second doped portion 134 is located away from the first doped layer 110.

[0137] The doping type of the second doped section 134 is the same as that of the second doped layer 120. That is, the number of outermost electrons of the dopant element in the second doped section 134 is the same as the number of outermost electrons of the dopant element in the second doped layer 120. Understandably, the doping element of the second doped section 134 and the doping element of the second doped layer 120 can be the same or different.

[0138] Furthermore, the ion doping concentration of the second doped portion 134 differs from that of the second doped layer 120, allowing the second doped portion 134 to be formed within the second doped layer 120. In some examples, the ion doping concentration of the second doped portion 134 is greater than that of the second doped layer 120.

[0139] In some examples, the second doped layer 120 is a P-type doped layer, and the second doped portion 134 is a P-type doped portion. In other examples, the second doped layer 120 is an N-type doped layer, and the second doped portion 134 is an N-type doped portion.

[0140] As described above, the doping type of the second doped layer 120 is different from that of the first doped layer 110. The doping type of the first doped portion 132 is the same as that of the first doped layer 110, and the doping type of the second doped portion 134 is the same as that of the second doped layer 120. Therefore, the doping types of the first doped portion 132 and the second doped portion 134 can be different.

[0141] like Figure 4D As shown, the second doped portion 134 and the first doped portion 132 are spaced apart. It can be understood that a depletion region (the region where photogenerated carriers are depleted due to diffusion) can be formed between the second doped portion 134 and the first doped portion 132.

[0142] In some examples, the orthographic projection of the second doped portion 134 onto the substrate 102 surrounds the orthographic projection of the first doped portion 132 onto the substrate 102.

[0143] The photoelectric conversion principle of the photosensitive unit 130 will be illustrated below with an example.

[0144] Taking the first doped portion 132 as an N-type doped portion and the second doped portion 134 as a P-type doped portion as an example, it can be understood that the P-type and N-type doped portions can form a PN junction. When light shines on the pixel unit 100, photons carrying energy enter the PN junction and transfer energy to the bound electrons on the covalent bonds, causing some electrons to break free from the covalent bonds, thereby generating freely moving electrons and holes, called photogenerated carriers. Electrons move towards the N-type doped portion, and holes move towards the P-type doped portion, enabling the photosensitive portion 130 to convert the optical signal into an electrical signal.

[0145] In some examples, an I-type semiconductor (i.e., an intrinsic layer semiconductor) may also be included between the P-type doped portion and the N-type doped portion to improve the photoelectric conversion performance of the photosensitive portion 130.

[0146] The first doped layer 110 has the same doping type as the first doped portion 132, that is, the first doped layer 110 is an N-type doped layer. During photoelectric conversion, the first doped layer 110 can provide freely moving electrons. Electrons move towards the N-type doped portion, increasing the width of the depletion region (the region where photogenerated carriers are depleted due to diffusion) of the pixel unit 100, thereby improving the photoelectric conversion performance of the pixel unit 100.

[0147] Figure 6A This is a flowchart of the steps of a method for fabricating a pixel unit according to some other embodiments. Figure 6B This is a structural diagram of a metal interconnect layer according to some embodiments. Figure 6C This is a structural diagram of a bond according to some embodiments. Figure 6D This is a structural diagram of a bond according to some other embodiments. Figure 6E This is a structural diagram of a first doped layer, a second doped layer, and a metal interconnect layer according to some embodiments.

[0148] In some embodiments, such as Figure 6A As shown, after the step of forming the photosensitive portion in the second doped layer (that is, after step 103), the method further includes:

[0149] Step S301: A metal interconnect layer is formed on the side of the second doped layer away from the first doped layer.

[0150] For example, such as Figure 6B As shown, the metal interconnect layer 150 is located on the surface of the second doped layer 120 away from the first doped layer 110 and covers the second doped layer 120.

[0151] For example, such as Figure 6B As shown, the surface of the second doped layer 120 away from the first doped layer 110 is the light-receiving surface 202. The surface of the first doped layer 110 away from the second doped layer 120 is the backlight surface 204. The metal interconnect layer 150 is located on the surface of the second doped layer 120 away from the first doped layer 110, that is, the metal interconnect layer 150 and the backlight surface 204 are disposed adjacent to each other. The light-receiving surface 202 is away from the metal interconnect layer 150.

[0152] In some examples, the image sensor 200 with its light-receiving surface 202 away from the metal interconnect layer 150 can be referred to as a back-side image sensor (BSI).

[0153] In some examples, such as Figure 6BAs shown, the metal interconnect layer 150 includes an interlayer dielectric 154 and a multilayer metal wiring 152, with the multilayer metal wiring 152 embedded within the interlayer dielectric 154. In some examples, the multilayer metal wiring 152 is electrically connected to the photosensitive unit 130, enabling the electrical signal converted from the optical signal to be transmitted outside the pixel unit 100 via the multilayer metal wiring 152.

[0154] The following example illustrates the method for forming the metal interconnect layer 150.

[0155] In some examples, a first sub-layer interlayer dielectric layer may be formed on the side of the second doped layer 120 away from the first doped layer 110, and a patterned layer of metal wiring 152 may be formed within the first sub-layer interlayer dielectric layer. A second sub-layer interlayer dielectric layer may be formed on the side of the first sub-layer interlayer dielectric layer away from the second doped layer 120, and a patterned layer of metal wiring 152 may be formed within the second sub-layer interlayer dielectric layer. A third sub-layer interlayer dielectric layer may be formed on the side of the second sub-layer interlayer dielectric layer away from the first sub-layer interlayer dielectric layer, and a patterned layer of metal wiring 152 may be formed within the third sub-layer interlayer dielectric layer. This process continues until an interlayer dielectric layer 154 and multiple layers of metal wiring 152 are formed, i.e., a metal interconnect layer 150 is formed.

[0156] In some examples, the fabrication method of the pixel unit 100 before forming the metal interconnect layer 150 (i.e., before step S301) further includes:

[0157] To form a transistor.

[0158] For example, such as Figure 6B As shown, transistor 168 can be a metal-oxide-semiconductor field-effect transistor (MOSFET).

[0159] In some examples, the number of transistors 168 is multiple. For example, the multiple transistors 168 include a transfer transistor, a drive transistor, a reset transistor, and a select transistor.

[0160] In some examples, the gate of transistor 168 is located within the second doped layer 120, and the source and drain are located on the side of the second doped layer 120 away from the first doped layer 110.

[0161] In step S302, the carrier sheet is bonded to the surface of the metal interconnect layer away from the second doped layer to form a bonded body.

[0162] For example, such as Figure 6CAs shown, after the carrier sheet 162 is bonded to the surface of the metal interconnect layer 150 away from the second doped layer 120, a bond body 160 can be formed. That is, the bond body 160 includes the carrier sheet 162, the metal interconnect layer 150, the first doped layer 110, the second doped layer 120, and the substrate 102.

[0163] Understandably, the carrier sheet 162 can support and protect the first doped layer 110, the second doped layer 120 and the metal interconnect layer 150, reducing the risk of the first doped layer 110, the second doped layer 120 and the metal interconnect layer 150 breaking during the removal of the substrate 102.

[0164] For example, the material of the support sheet 162 may include glass or metal.

[0165] In some examples, a temporary bonding adhesive may be applied to the surface of the carrier sheet 162 or the metal interconnect layer 150 away from the second doped layer 120, so that the carrier sheet 162 can be temporarily bonded to the surface of the metal interconnect layer 150 away from the second doped layer 120.

[0166] Before the step of removing the substrate by using the first doped layer as a stop layer (that is, before step S104), the method further includes:

[0167] Flip key combination.

[0168] Understandably, after bonding the carrier sheet 162 to the surface of the metal interconnect layer 150 away from the second doped layer 120 (that is, after forming the bond body 160), the bond body 160 is flipped, as follows: Figure 6D As shown, the surface of the substrate 102 away from the first doped layer 110 is positioned upwards. This arrangement facilitates the removal of the substrate 102 and improves the ease of fabrication of the pixel unit 100.

[0169] Understandably, after removing the substrate 102, as Figure 6E As shown, the surface of the first doped layer 110 away from the second doped layer 120 can be exposed, that is, the light-receiving surface 202 can be exposed.

[0170] Figure 7A This is a flowchart of the steps of a method for fabricating a pixel unit according to some other embodiments. Figure 7B This is a structural diagram of a first metal electrode and a second metal electrode according to some embodiments.

[0171] In some embodiments, such as Figure 7A As shown, before the step of bonding the carrier sheet to the surface of the metal interconnect layer away from the second doped layer (that is, before step S302), the procedure further includes:

[0172] Step S401: A first metal electrode is formed. The first metal electrode penetrates the metal interconnect layer along the direction from the metal interconnect layer to the second doped layer and is electrically connected to the first doped portion.

[0173] In step S402, a second metal electrode is formed. The second metal electrode penetrates the metal interconnect layer along the direction from the metal interconnect layer to the second doped layer and is electrically connected to the second doped portion.

[0174] Understandably, the first metal electrode 170 and the second metal electrode 180 serve to conduct electricity. For example... Figure 7B As shown, the first metal electrode 170 penetrates the metal interconnect layer 150 along the direction from the metal interconnect layer 150 to the second doped layer 120 and is electrically connected to the first doped portion 132. That is, the first metal electrode 170 can be embedded in the interlayer medium 154 and is electrically connected to the first doped portion 132.

[0175] Similarly, the second metal electrode 180 penetrates the metal interconnect layer 150 along the direction from the metal interconnect layer 150 to the second doped layer 120 and is electrically connected to the second doped portion 134. That is, the second metal electrode 180 can be embedded in the interlayer medium 154 and is electrically connected to the second doped portion 134.

[0176] The following is an example illustrating the method for forming the first metal electrode 170 and the second metal electrode 180.

[0177] In some examples, after forming the metal interconnect layer 150, a first receiving hole and a second receiving hole can be formed on the metal interconnect layer 150. The first receiving hole and the second receiving hole penetrate the interlayer dielectric 154 along the direction from the metal interconnect layer 150 to the second doped layer 120, respectively, and expose the first doped layer 132 and the second doped layer 134. A first metal electrode 170 and a second metal electrode 180 are respectively embedded in the first receiving hole and the second receiving hole, such that the first metal electrode 170 can be electrically connected to the first doped layer 132, and the second metal electrode 180 can be electrically connected to the second doped portion 134.

[0178] In other examples, a first metal electrode 170 and a second metal electrode 180 may also be formed during the formation of the metal interconnect layer 150.

[0179] For example, a first sub-layer dielectric layer may be formed on the side of the second doped layer 120 away from the first doped layer 110, and a patterned first conductive layer may be formed within the first sub-layer dielectric layer. The first conductive layer includes a metal wiring layer 152, a first sub-metal electrode, and a second sub-metal electrode. A second sub-layer dielectric layer may be formed on the side of the first sub-layer dielectric layer away from the second doped layer 120, and a patterned second conductive layer may be formed within the second sub-layer dielectric layer. The second conductive layer includes a metal wiring layer 152, a first sub-metal electrode, and a second sub-metal electrode. A third sub-layer dielectric layer may be formed on the side of the second sub-layer dielectric layer away from the first sub-layer dielectric layer, and a patterned third conductive layer may be formed within the third sub-layer dielectric layer. The third conductive layer includes a metal wiring layer 152, a first sub-metal electrode, and a second sub-metal electrode.

[0180] Understandably, multiple first sub-layer interlayer dielectric layers can form an interlayer dielectric layer 154, multiple first sub-metal electrodes can form a first metal electrode 170, and multiple second sub-metal electrodes can form a metal electrode 180. This process continues until a metal interconnect layer 150, a first metal electrode 170, and a second metal electrode 180 are formed.

[0181] Understandably, the first metal electrode 170 and the second metal electrode 180 provide power to the first doped portion 132 and the second doped portion 134, enabling the pixel unit 100 to perform photoelectric conversion.

[0182] The following example illustrates how the first metal electrode 170 and the second metal electrode 180 are electrically connected to the positive and negative terminals of the power supply, with the first doped part 132 being an N-type doped part and the second doped part 134 being a P-type doped part.

[0183] In some examples, the first metal electrode 170 can be electrically connected to the positive terminal of the power supply, and the second metal electrode 180 can be electrically connected to the negative terminal of the power supply, so that the potential of the first doped portion 132 can be higher than the potential of the second doped portion 134, thereby forming an electric field in the second doped layer 120 in the direction from the first doped portion 132 to the second doped portion 134, so as to achieve reverse bias of the photosensitive portion 130.

[0184] In some examples, the first metal electrode 170 includes a first connecting portion and a first electrode plate. The first connecting portion is embedded within the interlayer dielectric 154, and the first electrode plate is electrically connected to the connecting portion. The second metal electrode 180 includes a second connecting portion and a second electrode plate. The second connecting portion is embedded within the interlayer dielectric 154, and the second electrode plate is electrically connected to the connecting portion. With this configuration, by electrically connecting the positive and negative terminals of the power supply to the first and second electrode plates respectively, power can be supplied to the photosensitive unit 130.

[0185] In some examples, the surfaces of the first and second electrode plates away from the second doped layer 120 are flush with or approximately flush with the surface of the metal interconnect layer 150 away from the second doped layer 120.

[0186] Figure 8A This is a flowchart of the steps of a method for fabricating a pixel unit according to some other embodiments. Figure 8B This is a structural diagram of a light-adjusting assembly according to some embodiments. Figure 8C This is a structural diagram of a light-adjusting assembly according to some other embodiments.

[0187] In some embodiments, such as Figure 8A As shown, after the step of removing the substrate by using the first doped layer as a stop layer (that is, after step S104), the method further includes:

[0188] Step S501: A light modulation component is formed on the side of the first doped layer away from the second doped layer.

[0189] As can be seen from the above, after removing the substrate 102, the surface of the first doped layer 110 on the side away from the second doped layer 120 can be exposed, that is, the light-receiving surface 202 can be exposed. Figure 8B As indicated by the middle arrow, light illuminates the pixel unit 100 along the direction from the light-receiving surface 202 to the backlight surface 204.

[0190] A light-modulating component 140 is formed on the side of the first doped layer 110 away from the second doped layer 120, such as Figure 8B As shown, this allows the light adjustment component 140 to cover the light-receiving surface 202.

[0191] Understandably, the light adjustment component 140 is used to adjust light. In some examples, the light adjustment component 140 includes an anti-reflection coating (ARC) 142, a filter 144, and a microlens 146.

[0192] For example, such as Figure 8B As shown, the anti-reflective film 142 is located on the side of the first doped layer 110 away from the second doped layer 120 and covers the first doped layer 110, that is, the anti-reflective film 142 can cover the light-receiving surface 202.

[0193] In some examples, the antireflective film 142 is attached to the light-receiving surface 202.

[0194] Understandably, the anti-reflective film 142 can reduce the reflection of light, thereby increasing the intensity of light illuminating the photosensitive unit 130, enabling the photosensitive unit 130 to acquire weak light signals, improving the reliability of the pixel unit 100, and thus improving the reliability of the image sensor 200.

[0195] In some examples, the antireflective film 142 is made of silicon nitride or silicon dioxide.

[0196] The filter 144 is located on the side of the antireflective film 142 away from the first doped layer 110. For example, the filter 144 covers the antireflective film 142.

[0197] Understandably, filter 144 is used to filter light. In some examples, filter 144 can be a red filter, a green filter, or a blue filter. The filters 144 of different pixel units 100 can be the same or different.

[0198] Microlens 146 is located on the side of filter 144 away from antireflective film 142. Understandably, microlens 146 is used to focus light, thereby further increasing the intensity of light illuminating photosensitive unit 130, enabling photosensitive unit 130 to acquire weak light signals, improving the reliability of pixel unit 100, and thus improving the reliability of image sensor 200.

[0199] In some examples, the number of microlenses 146 is the same as the number of photosensitive parts 130, with one microlens 146 used to focus light onto one photosensitive part 130.

[0200] In other examples, the number of microlenses 146 is greater than the number of photosensitive units 130. Multiple microlenses 146 (e.g., 2, 3, or 4) converge light to a single photosensitive unit 130. For example, the microlenses 146 can be a combination of various lenses such as spherical lenses, aspherical lenses, cylindrical lenses, and prisms.

[0201] Step S502: Debond the carrier sheet to the surface of the metal interconnect layer away from the second doped layer.

[0202] like Figure 8C As shown, after the light adjustment component 140 is formed, the carrier sheet 162 and the metal interconnect layer 150 are debonded, so that the surface of the metal interconnect layer 150 away from the second doped layer 120 (that is, the backlight surface 204) can be exposed.

[0203] In some examples, the image sensor 200 also includes a packaging substrate. The packaging substrate is located on the side of the metal interconnect layer 150 away from the second doped layer 120 and is used to package a plurality of pixel units 100.

[0204] The following example illustrates the debonding method by using temporary bonding adhesive to temporarily bond the carrier sheet 162 to the metal interconnect layer 150 on the side away from the second doped layer 120.

[0205] Understandably, the viscosity of the temporary bonding adhesive can decrease when the debonding conditions are met. This allows the carrier sheet 162 to be debonded to the metal interconnect layer 150 by sliding the carrier sheet 162. For example, depending on the temporary bonding adhesive, the debonding conditions may include high temperature, ultraviolet light irradiation, or laser irradiation.

[0206] As can be seen from the above, in some embodiments of this disclosure, after the light adjustment component 140 is formed, the carrier sheet 162 is debonded to the surface of the metal interconnect layer 150 away from the second doped layer 120. In this way, during the formation of the light adjustment component 140, the carrier sheet 162 can support and protect the metal interconnect layer 150, the first doped layer 110 and the second doped layer 120, reduce the risk of breakage of the metal interconnect layer 150, the first doped layer 110 and the second doped layer 120, and improve the reliability of the preparation method of the pixel unit 100.

[0207] In other examples, the carrier sheet 162 may be debonded to the surface of the metal interconnect layer 150 away from the second doped layer 120 before the light adjustment component 140 is formed. The metal interconnect layer 150 can protect the first doped layer 110 and the second doped layer 120, reducing the risk of the first doped layer 110 and the second doped layer 120 breaking.

[0208] On the other hand, such as Figure 4G As shown, an embodiment of this disclosure provides a pixel unit 100. The pixel unit 100 is fabricated using the pixel unit fabrication method described above, and therefore has all the aforementioned beneficial effects, which will not be repeated here.

[0209] Pixel unit 100 includes a first doped layer 110, a second doped layer 120, and a photosensitive portion 130. The second doped layer 120 is located to one side of the first doped layer 110. The doping type of the second doped layer 120 is different from that of the first doped layer 110. The photosensitive portion 130 is located within the second doped layer 120.

[0210] Understandably, the above embodiments of this disclosure have already provided examples of the first doped layer 110, the second doped layer 120, and the photosensitive part 130, and will not be repeated here.

[0211] In some embodiments, such as Figure 4C As shown, the thickness L2 of the first doped layer 110 ranges from 0.1 μm to 5 μm. The ion doping concentration of the first doped layer 110 ranges from 1e. 13 / cm 3 ~1e 17 / cm 3 .

[0212] In some examples, the thickness L2 of the first doped layer 110 can range from 0.5 μm to 4.5 μm, 1 μm to 3.5 μm, or 1.5 μm to 3 μm, etc. For example, the thickness L2 of the first doped layer 110 can be 1.5 μm, 2.2 μm, 3.6 μm, or 4.3 μm, etc.

[0213] Understandably, setting the thickness L2 of the first doped layer 110 to a range of 0.1 μm to 5 μm avoids the first doped layer 110 being too thin (e.g., less than 0.1 μm), thereby reducing the risk of completely removing the first doped layer 110 when removing the substrate 102, allowing the first doped layer 110 to serve as a stop layer when removing the substrate 102. Furthermore, it also avoids the first doped layer 110 being too thick (e.g., greater than 5 μm), reducing the distance between the light-receiving surface 202 (i.e., the surface of the first doped layer 110 away from the second doped layer 120) and the photosensitive part 130, increasing the intensity of light irradiating the photosensitive part 130, and improving the photoelectric conversion performance of the pixel unit 100.

[0214] In some examples, the ion doping concentration of the first doped layer 110 can range from 1e to 1e. 14 / cm 3 ~1e 17 / cm 3 Or 1e 15 / cm 3 ~1e 16 / cm 3 For example, the ion doping concentration of the first doped layer 110 can be 1e. 14 / cm 3 1e 15 / cm 3 Or 1e 16 / cm 3 wait.

[0215] Understandably, the ion doping concentration of the first doped layer 110 is set to a range of 1e. 13 / cm 3 ~1e 17 / cm 3 This avoids the ion doping concentration of the first doped layer 110 being too low (e.g., less than 1e). 13 / cm 3 This makes it easy to determine whether the surface of the first doped layer 110 away from the second doped layer 120 is exposed during the removal of the substrate 102, so that the first doped layer 110 can serve as a stop layer when removing the substrate 102.

[0216] Furthermore, as described above, the first doped layer 110 can provide electrons or holes to the photosensitive portion 130 to increase the width of the depletion region, thereby avoiding a low or excessively high ion doping concentration (e.g., less than 1 e) in the first doped layer 110. 13 / cm 3 It can also increase the amount of electrons or holes provided by the first doped layer 110 to the photosensitive part 130, thereby improving the photoelectric conversion performance of the pixel unit 100.

[0217] Furthermore, the ion doping concentration of the first doped layer 110 is set to a range of 1e. 13 / cm 3 ~1e 17 / cm 3 This also avoids excessively high ion doping concentration in the first doped layer 110 (e.g., greater than 1e). 17 / cm 3 Based on the fact that the first doped layer 110 can serve as a stop layer when removing the substrate 102, the fabrication process of the first doped layer 110 is simplified and the cost of the pixel unit 100 is reduced.

[0218] In some embodiments, such as Figure 4C As shown, the thickness L3 of the second doped layer 120 ranges from 1 μm to 2.5 μm. The ion doping concentration of the second doped layer 120 ranges from 1e 14 / cm 3 ~1e 17 / cm 3 .

[0219] In some examples, the thickness L3 of the second doped layer 120 ranges from 1 μm to 2 μm, 1.5 μm to 2 μm, or 1.8 μm to 2.2 μm, etc. For example, the thickness L3 of the second doped layer 120 can be 1.2 μm, 1.7 μm, 1.9 μm, or 2.3 μm, etc.

[0220] Understandably, setting the thickness L3 of the second doped layer 120 to a range of 1 μm to 2.5 μm avoids the second doped layer 120 being too thin (e.g., less than 1 μm), allowing the photosensitive part 130 to be located within the second doped layer 120. Furthermore, it also avoids the second doped layer 120 being too thick (e.g., greater than 2.5 μm), thereby increasing the intensity of light irradiating the photosensitive part 130 and improving the photoelectric conversion performance of the pixel unit 100.

[0221] In some examples, the ion doping concentration of the second doped layer 120 can range from 1e to 1e. 15 / cm 3 ~1e 17 / cm 3 Or 1e16 / cm 3 ~1e 17 / cm 3 For example, the ion doping concentration of the second doped layer 120 can be 1e. 15 / cm 3 1e 16 / cm 3 Or 1e 17 / cm 3 wait.

[0222] Understandably, since the photosensitive part 130 is located within the second doped layer 120, the second doped layer 120 can provide electrons or holes to the photosensitive part 130 during photoelectric conversion. The ion doping concentration of the second doped layer 120 is set to a range of 1e. 14 / cm 3 ~1e 17 / cm 3 This avoids the second doped layer 120 having an excessively low ion doping concentration (e.g., less than 1 e). 14 / cm 3 This increases the amount of electrons or holes provided by the second doped layer 120 to the photosensitive part 130, thereby improving the photoelectric conversion performance of the pixel unit 100.

[0223] Furthermore, it also avoids excessively high ion doping concentration in the second doped layer 120 (e.g., greater than 1e). 17 / cm 3 This simplifies the fabrication process of the second doped layer 120 and reduces the cost of the pixel unit 100 while still meeting the requirements of photoelectric conversion.

[0224] In some embodiments, the first doped layer 110 is an N-type doped layer and the second doped layer 120 is a P-type doped layer.

[0225] As can be seen from the above, during photoelectric conversion, the majority carriers provided by the P-type doped layer are holes, and the minority carriers are electrons. The majority carriers provided by the N-type doped layer are electrons, and the minority carriers provided by the N-type doped layer are holes.

[0226] Understandably, during photoelectric conversion, the electron mobility is greater than the hole mobility. The photosensitive part 130 is located within the second doped layer 120 (i.e., the P-type doped layer), so that during photoelectric conversion, the P-type doped layer can provide holes for the photosensitive part 130, increasing the amount of hole migration during photoelectric conversion and improving the photoelectric conversion performance of the pixel unit 100.

[0227] Furthermore, by setting the first doped layer 110 to be an N-type doped layer, the first doped layer 110 can provide electrons to the photosensitive part 130 during photoelectric conversion, thereby increasing the depletion region width and further improving the photoelectric conversion performance of the pixel unit 100, thereby improving the photoelectric conversion performance of the image sensor 200.

[0228] In some embodiments, such as Figure 4G As shown, the pixel unit 100 further includes a light adjustment assembly 140. The light adjustment assembly 140 includes an anti-reflective film 142, a filter 144, and a microlens 146. The anti-reflective film 142 is located on the side of the first doped layer 110 away from the second doped layer 120 and covers the first doped layer 110. The filter 144 is located on the side of the anti-reflective film 142 away from the first doped layer 110. The microlens 146 is located on the side of the filter 144 away from the anti-reflective film 142.

[0229] As can be seen from the above, the surface of the first doped layer 110 away from the second doped layer 120 is the light-receiving surface 202 of the pixel unit 100, such as... Figure 4G As indicated by the middle arrow, light illuminates the pixel unit 100 along the direction from the light-receiving surface 202 to the backlight surface 204.

[0230] like Figure 4G As shown, the light adjustment component 140 is located on the side of the first doped layer 110 away from the second doped layer 120, that is, the light adjustment component 140 can cover the light-receiving surface 202.

[0231] Understandably, such as Figure 4G As shown, the light adjustment assembly 140 is used to adjust the light. The light adjustment assembly 140 includes an anti-reflective film 142, a filter 144, and a microlens 146.

[0232] The anti-reflective film 142 is located on the side of the first doped layer 110 away from the second doped layer 120 and covers the first doped layer 110. Understandably, the anti-reflective film 142 can reduce the reflection of light, thereby increasing the intensity of light illuminating the photosensitive unit 130, enabling the photosensitive unit 130 to acquire weak light signals, improving the reliability of the pixel unit 100, and thus improving the reliability of the image sensor 200.

[0233] In some examples, the antireflective film 142 is made of silicon nitride or silicon dioxide.

[0234] The filter 144 is located on the side of the antireflective film 142 that is away from the first doped layer 110 and away from the second doped layer 120. For example, the filter 144 covers the antireflective film 142.

[0235] Understandably, filter 144 is used to filter light. In some examples, filter 144 can be a red filter, a green filter, or a blue filter. The filters 144 of different pixel units 100 can be the same or different.

[0236] Microlens 146 is located on the side of filter 144 away from antireflective film 142. Understandably, microlens 146 is used to focus light, thereby further increasing the intensity of light illuminating photosensitive unit 130, enabling photosensitive unit 130 to acquire weak light signals, improving the reliability of pixel unit 100, and thus improving the reliability of image sensor 200.

[0237] In some examples, the number of microlenses 146 is the same as the number of photosensitive parts 130, with one microlens 146 used to focus light onto one photosensitive part 130.

[0238] In other examples, the number of microlenses 146 is greater than the number of photosensitive units 130. Multiple microlenses 146 (e.g., 2, 3, or 4) focus light onto a single photosensitive unit 130.

[0239] For example, the microlens 146 can be a combination of various lenses such as spherical lenses, aspherical lenses, cylindrical lenses, and prisms.

[0240] By providing the light adjustment component 140, the intensity of light illuminating the photosensitive unit 130 is further increased, enabling the photosensitive unit 130 to acquire weak light signals, thereby improving the reliability of the pixel unit 100 and ultimately enhancing the reliability of the image sensor 200. Furthermore, it allows monochromatic light of different colors (e.g., red, green, and blue light) to illuminate the photosensitive unit 130, enabling the pixel unit 100 to convert light signals of different colors of monochromatic light into electrical signals, thus improving the applicability of the pixel unit 100.

[0241] As described above, the image sensor 200 includes at least two pixel units 100. The at least two pixel units 100 are arranged in an array. In some embodiments, such as... Figure 4G As shown, the image sensor 200 also includes an isolation section 210. The isolation section 210 is located between any two adjacent pixel units 100.

[0242] Understandably, the isolation section 210 is used to isolate light. For example, such as... Figure 4G As shown, by providing the isolation section 210, the pixel unit 100a and the pixel unit 100b can respectively convert the acquired light signal into an electrical signal, thereby reducing the intensity of light from the pixel unit 100a illuminating the pixel unit 100b, thus reducing the crosstalk between two adjacent pixel units 100 and improving the reliability of the image sensor 200.

[0243] It should be noted that in the embodiments of this disclosure, pixel unit 100a and pixel unit 100b are only used to distinguish two adjacent pixel units 100, and do not further limit the pixel unit 100.

[0244] For example, the isolation part 210 can be made of metal or non-metal.

[0245] In some examples, such as Figure 4G As shown, the isolation section 210 includes a first isolation section 212 and a second isolation section 214.

[0246] The first isolation portion 212 is located within the first doped layer 110 and a portion of the second doped layer 120, serving to block light. For example, the first isolation portion 212 can be a deep trench isolation (DTI). In some examples, the first isolation portion 212 can be formed using ion implantation.

[0247] In some examples, the first isolation portion 212 can also be embedded within the anti-reflective film 142 to further improve the isolation effect.

[0248] The second isolation section 214 is located between two adjacent filters 144 and serves to block light. For example, the second isolation section 214 can be a metal grid.

[0249] Understandably, by providing the isolation section 210, the intensity of light illuminating adjacent pixel units 100 is reduced, thereby reducing optical crosstalk between two adjacent pixel units 100 and improving the reliability of the image sensor 200.

[0250] Figure 9 This is a structural diagram of a camera assembly according to some embodiments.

[0251] On the other hand, such as Figure 9 As shown, an embodiment of this disclosure provides a camera assembly 300. The camera assembly 300 includes a lens assembly 310 and an image sensor 200 as described above. The image sensor 200 is located on the light-emitting side of the lens assembly 310.

[0252] The camera assembly 300 provided in the embodiments of this disclosure includes the image sensor 200 as described above, and therefore has all the beneficial effects described above, which will not be repeated here.

[0253] For example, such as Figure 9 As indicated by the middle arrow, light can reach the lens assembly 310. The lens assembly 310 can change the direction of light propagation, such as... Figure 9As shown by the dashed arrow, the light emitted from the light-emitting side of the lens assembly 310 can illuminate the image sensor 200 and be converted into an electrical signal by the image sensor 200 to realize the photoelectric conversion function.

[0254] In some examples, the lens assembly 310 includes at least one of a convex lens and a concave lens.

[0255] Figure 10 This is a structural diagram of an electronic device according to some embodiments.

[0256] In another aspect, embodiments of this disclosure provide an electronic device 400. For example... Figure 10 As shown, the electronic device 400 includes a housing 410 and a camera assembly 300 as described above. The housing 410 has a first through-hole. The camera assembly 300 is embedded in the first through-hole.

[0257] The electronic device 400 provided in the embodiments of this disclosure includes the camera assembly 300 as described above, and therefore has all the beneficial effects described above, which will not be repeated here.

[0258] For example, electronic device 400 includes mobile phones, tablets, smart access control systems, product testing instruments, televisions, smart wearable products (e.g., smartwatches, smart bracelets), virtual reality (VR) terminal devices, augmented reality (AR) terminal devices, and other electronic products with image acquisition capabilities. This application does not impose any special limitations on the specific form of electronic device 400.

[0259] In some examples, when the aforementioned electronic device 400 is a mobile phone, tablet computer, or product testing instrument, it can take pictures of objects or processed products. Light enters from the light-incident side of the lens assembly 310 and exits from the light-outcident side of the lens assembly 310. It is then received by the image sensor 200 and converted into an electrical signal, enabling the electronic device 400 to perform image acquisition.

[0260] In some examples, the electronic device 400 has a processor and a display. The image sensor 200 converts light signals into electrical signals and transmits these signals to the processor. The processor then generates image information of the object being detected and displays it on the display.

[0261] In some examples, the processor can be a central processing unit (CPU) or a graphics processing unit (GPU).

[0262] In some embodiments, such as Figure 10 As shown, the housing 410 also has a second through hole. The electronic device 400 also includes a transmitter 420. The transmitter 420 is used to emit light towards the object to be detected. The camera assembly 300 is used to receive the light reflected from the object to be detected. Alternatively, the camera assembly 300 is used to receive light passing through the object to be detected.

[0263] In some examples, transmitter 420 is used to emit non-intrusive light, such as infrared or near-infrared light. The light emitted by transmitter 420 is reflected by the object to be detected (e.g., a face) to camera assembly 300. Image sensor 200 within camera assembly 300 receives the light reflected from the face and converts it into an electrical signal to enable the recognition function of electronic device 400. In this case, electronic device 400 can be a mobile phone or a smart access control system, or other electronic devices with recognition capabilities.

[0264] In other examples, the camera assembly 300 is used to receive light passing through an object to be detected. For instance, the emitter 420 emits invisible light, such as X-rays or gamma rays, towards the object. The invisible light passes through the object and illuminates the camera assembly 300. The image sensor 200 within the camera assembly 300 receives the light passing through the object and converts it into an electrical signal to enable the detection function of the electronic device 400. In this case, the electronic device 400 can be an electronic device with X-ray detection capabilities, such as a security inspection device.

[0265] Understandably, by setting up the transmitter 420, the electronic device 400 can still acquire image information of the object to be detected even in low light conditions, thereby improving the applicability of the electronic device.

[0266] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0267] The above description is merely a specific embodiment of this disclosure, but the scope of protection of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this disclosure should be included within the scope of protection of this disclosure. Therefore, the scope of protection of this disclosure should be determined by the scope of the claims.

Claims

1. A method for fabricating a pixel unit, characterized in that, include: A first doped layer is formed on one side of the substrate; The first doped layer is doped with a first element, while the substrate is not doped with the first element; A second doped layer is formed on the side of the first doped layer away from the substrate, and the doping type of the second doped layer is different from that of the first doped layer; A photosensitive portion is formed within the second doped layer; The first doped layer is used as a stop layer to remove the substrate; During the removal of the substrate, the first surface is exposed; when the first surface can detect the first element, the substrate is completely removed.

2. The method for preparing a pixel unit according to claim 1, characterized in that, The substrate includes a doped substrate; the doping type of the first doped layer is different from the doping type of the substrate.

3. The method for preparing a pixel unit according to claim 1, characterized in that, The substrate is an undoped substrate.

4. The method for preparing a pixel unit according to any one of claims 1 to 3, characterized in that, The step of forming a first doped layer on one side of the substrate includes: The first doped layer is formed on one side of the substrate using an epitaxial growth process; The step of forming a second doped layer on the side of the first doped layer away from the substrate includes: An epitaxial growth process is used to form a second doped layer on the side of the first doped layer away from the substrate.

5. The method for preparing a pixel unit according to any one of claims 1 to 3, characterized in that, The photosensitive portion includes a first doped portion and a second doped portion, and the step of forming the photosensitive portion in the second doped layer includes: A first doped portion is formed within the second doped layer; the doping type of the first doped portion is the same as the doping type of the first doped layer. A second doped portion is formed within the second doped layer, and the second doped portion is spaced apart from the first doped portion. The doping type of the second doped portion is the same as that of the second doped layer; and the ion doping concentration of the second doped portion is different from that of the second doped layer.

6. The method for preparing a pixel unit according to claim 5, characterized in that, After the step of forming the photosensitive portion in the second doped layer, the method further includes: A metal interconnect layer is formed on the side of the second doped layer away from the first doped layer; The carrier sheet is bonded to the surface of the metal interconnect layer away from the second doped layer to form a bond body; Before the step of removing the substrate by using the first doped layer as a stop layer, the method further includes: Flip the bonded body.

7. The method for preparing a pixel unit according to claim 6, characterized in that, Before the step of bonding the carrier sheet to the surface of the metal interconnect layer away from the second doped layer, the method further includes: A first metal electrode is formed, which penetrates the metal interconnect layer along the direction from the metal interconnect layer to the second doped layer and is electrically connected to the first doped portion; A second metal electrode is formed, which penetrates the metal interconnect layer along the direction from the metal interconnect layer to the second doped layer and is electrically connected to the second doped portion.

8. The method for preparing a pixel unit according to claim 6, characterized in that, After the step of removing the substrate by using the first doped layer as a stop layer, the method further includes: A light modulation component is formed on the side of the first doped layer away from the second doped layer; The carrier sheet is debonded to the surface of the metal interconnect layer away from the second doped layer.

9. A pixel unit, characterized in that, The pixel unit is prepared using the pixel unit preparation method as described in any one of claims 1 to 8, and the pixel unit comprises: First doped layer; A second doped layer is located on one side of the first doped layer; the doping type of the second doped layer is different from that of the first doped layer. The photosensitive part is located within the second doped layer.

10. The pixel unit according to claim 9, characterized in that, The thickness of the first doped layer ranges from 0.1 μm to 5 μm, and the ion doping concentration of the first doped layer ranges from 1e. 13 / cm 3 ~1e 17 / cm 3 .

11. The pixel unit according to claim 9, characterized in that, The thickness of the second doped layer ranges from 1 μm to 2.5 μm, and the ion doping concentration of the second doped layer ranges from 1e. 14 / cm 3 ~1e 17 / cm 3 .

12. The pixel unit according to any one of claims 9 to 11, characterized in that, The first doped layer is an N-type doped layer, and the second doped layer is a P-type doped layer.

13. The pixel unit according to any one of claims 9 to 11, characterized in that, The pixel unit further includes a light adjustment component, the light adjustment component comprising: An anti-reflective film is located on the side of the first doped layer away from the second doped layer and covers the first doped layer; The filter is located on the side of the antireflective film away from the first doped layer; A microlens is located on the side of the filter away from the antireflective film.

14. An image sensor, characterized in that, It includes at least two pixel units as described in any one of claims 9 to 13, and the at least two pixel units are arranged in an array.

15. The image sensor according to claim 14, characterized in that, The image sensor also includes: An isolation section is located between any two adjacent pixel units.

16. A camera assembly, characterized in that, include: Lens assembly; The image sensor as described in claim 14 or 15, wherein the image sensor is located on the light-emitting side of the lens assembly.

17. An electronic device, characterized in that, include: The housing has a first through hole; The camera assembly as described in claim 16 is embedded in the first through hole.

18. The electronic device according to claim 17, characterized in that, The housing also has a second through hole, and the electronic device further includes: A transmitter used to emit light towards an object to be detected; The camera assembly is used to receive light reflected from the object to be detected; or, The camera assembly is used to receive light passing through the object to be detected.

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